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A decentralized negotiation framework for restoring electrical energy delivery networks with intelligent power routers - IPRs

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Title:
A decentralized negotiation framework for restoring electrical energy delivery networks with intelligent power routers - IPRs
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Laurens, Idalides Jose Vergara ( author )
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English
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Electric power systems -- Control ( lcsh )
Electric power distribution -- Management ( lcsh )
Electric power distribution -- Management ( fast )
Electric power systems -- Control ( fast )
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bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )

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Current Electrical Energy Delivery Networks (EEDN) are managed from a centralized operations and control center. In the event of a system failure, human operators at this control centers device schemes for restoring the system back into an operational state. Such a scheme is inefficient and unreliable since a crippling failure at the control center would render the system useless. In this thesis, we present a decentralized framework to help control and manage an Electrical Energy Delivery Networks (EEDN). Our scheme is based on the idea of modelling the EEDN as a data network. The paths taking the flows of power are then controlled by devices that we call Intelligent Power Routers (IPRs). These IPRs monitor the status of the network, and when a failure occurs, they work together to open new paths to send power from the generators to the consumers (e.g. cities, factories, hospitals). In this thesis, we present the architecture of our solution, and show distributed algorithms for a particular problem: restoring the undamaged part of a EEDN after a major failure. Our experiments demonstrate that our approach is reliable, effective, and scalable. More importantly, our approach can find restoration solutions that are efficient, and sometimes as good as those produced by centralized algorithms. We present a first prototype of IPRs network that has a satisfactory performance for system restoration using the new approach.
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Includes bibliographical references.
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System requirements: Adobe Reader.
Statement of Responsibility:
by Idalides Jose Vergara Laurens.

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898500216 ( OCLC )
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A Decentralized Negotiation Framework for Restoring Electrical Energy Delivery Networks with Intell igent Power Routers IPRs By Idalides Jose Vergara Laurens A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in COMPUTER ENGINEERING University of Puerto Rico Mayagez Campus 2005 Approved by: ______________________________________ Bienvenido Velez Member, Graduate Committee ____________________ Date ______________________________________ Agustin Irizarry Member, Graduate Committee ____________________ Date ______________________________________ Jose Fernando Vega Member, Graduate Committee ____________________ Date ______________________________________ Manuel Rodriguez President, Graduate Committee ____________________ Date ______________________________________ Ana C. Gonzalez Representative of Graduate Studies ____________________ Date ______________________________________ Isodoro Couvertier Chairperson of the Department ____________________ Date

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UMI Number: 1427024 1427024 2005 UMI Microform Copyright All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, MI 48106-1346 by ProQuest Information and Learning Company.

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ABSTRACT ADecentralizedFrameworkforRestoringElectricalEnergy DeliveryNetworkswithIntelligentPowerRoutersBy IdalidesJoseVergaraLaurensCurrentElectricalEnergyDeliveryNetworks(EEDN)aremanagedfromacentralizedoperationsandcontrolcenter.Intheeventofasystemfailure,humanoperatorsat thiscontrolcentersdeviceschemesforrestoringthesystembackintoanoperationalstate. Suchaschemeisinecientandunreliablesinceacripplingfailureatthecontrolcenter wouldrenderthesystemuseless.Inthisthesis,wepresentadecentralizedframeworkto helpcontrolandmanageanElectricalEnergyDeliveryNetworks(EEDN).Ourschemeis basedontheideaofmodellingtheEEDNasadatanetwork.Thepathstakingthe”owsof powerarethencontrolledbydevicesthatwecallIntelligentPowerRouters(IPRs).These IPRsmonitorthestatusofthenetwork,andwhenafailureoccurs,theyworktogetherto opennewpathstosendpowerfromthegeneratorstotheconsumers(e.gcities,factories, hospitals).Inthisthesis,wepresentthearchitectureofoursolution,andshowdistributed algorithmsforaparticularproblem:restoringtheundamagedpartofaEEDNafteramajor failure.Ourexperimentsdemonstratethatourapproachisreliable,eective,andscalable. Moreimportantly,ourapproachcan“ndrestorationsolutionsthatareecient,andsometimesasgoodasthoseproducedbycentralizedalgorithms.Wepresenta“rstprototype ofIPRsnetworkthathasasatisfactoryperformanceforsystemrestorationusingthenew approach. ii

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RESUMEN UnEsquemaDescentralizadoparaRestaurarRedesde PotenciaEl ectricautilizandoEnrutadoresInteligentesde PotenciaPor IdalidesJoseVergaraLaurensActualmentelasredesdetransmisi onydistribuci ondepotenciael ectricasonadministradasdesdeuncentrodecontrol.Cuandoocurreunafallaenelsistema,losoperadoresenestecentrodecontrolutilizanesquemasderestauraci onparallevaralsistema nuevamenteaunestadooperacional.Esteesquematieneladebilidadques šelcentrode controlesafectadoporlafalla,elsistemanopuedeserrestaurado.Elesquemapropuesto enestatesissebasaenlaideademodelarlasredesdePotenciael etricacomounared detransmisi ondedatos.Loscaminosutilizadosparatransmitirpotenciael ectricason controladosporunosdispositivosllamadosEnrutadoresInteligentesdePotencia.Estosdispositivosmonitoreanelestadodelsistema,ycuandoocurreunafalla,ellostrabajanjuntos paraestablecernuevoscaminosparatransmitirpotenciadesdelosgeneradoreshastalos consumidores(Ciudades,f abricas,Hospitales).Enestatesispresentamoslaarquitectura propuestaparanuestrasoluci onylosalgoritmosdistribuidosparaunproblemaparticular: restaurarlamayorparteposibledelsistemadepotencialuegodeundisturbiomayor.Nuestrosexperimentosmuestranquenuestrapropuestaescon“able,efectivayescalable.Lo m asimportanteesquenuestrapropuestalograencontraresquemasderestauraci onefectivos yenalgunasocacionestanbuenoscomoloscentralizados.Presentamoselprimerprototipo deEnrutadoresInteligentesdePotencia,elcualtuvounbuendesempe oparalarestauraci o dediversossistemasdepotencia. iii

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Copyright c by IdalidesJoseVergaraLaurens 2005iv

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Tomyfamily,wifeCarmen,fatherId alides,motherRosalbaandsisterNeifav

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ACKNOWLEDGMENTSIwouldliketothankin“nitelymyadvisorDr.ManuelRodr šguezforgivingme theopportunitytoworkwithhim,forhissupport,theadvicegiventomethroughoutthe graduateprogramandespeciallyforhisfriendshipduringtheseyears.Also,Iwanttothank Dr.BienvenidoV elez,Dr.Jos eFernandoVegaandDr.Agust šnIrizarryforservingon mygraduatecommitteeandforreviewingmywork.De“nitively,iwanttothankmywife CamenLilianaforsupportingmetheseyears.Likewise,iwanttothankmyparentsI alides andRosalbaandmysisterNeifafortheircontinuouslysupportthroughalltheseyears. IwanttothankthemembersoftheEPNESProjectatUPRM,especiallyprofessorsA. Irizarry,B.V elez,J.Cede noandstudentsMarianela,Carlos,Christian,JuanandJaneth.I thanktomypartnersofAdvanceDataManagementGroup-ADMG(Elliot,Ren e,Hillary, JairoandLizvette)andParallelandDistributedComputingLab(Wilson,Gustavoand Amado)fortheiracademiccontributionsandtheirfriendship.Finally,iwanttothankGod forallthathehasgavemealltheseyears. vi

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TABLEOFCONTENTSLISTOFTABLESx LISTOFFIGURESxii 1Introduction1 1.1Overview .....................................1 1.2ProblemStatement................................2 1.3ProposedSolution................................3 1.4ObjectivesofthisThesis.............................5 1.5Contributions..... ..............................6 1.6ThesisStructure.................................6 2RelatedWork8 2.1Overview .....................................8 2.2DistributedSystems. ..............................8 2.3ComputerNetworksandRoutingProtocols ..................10 2.4Peer-to-PeerNetworks ..............................13 2.5Multi-agentsTechnologies.. ..........................14 2.6ElectricalPowerSystems............................15 3ModelDescriptionandIPRsNetworkArchitecture18 3.1Overview .....................................18 3.2MappingofElectricalEnergyDistributionNetworks(EEDN)toaWideArea Network(WAN).................................18 3.2.1Network-”owproblem..........................19 3.2.2SimilaritiesofanEEDNwithaWAN... ..............20 3.2.3OperationinWAN............................21 3.3AssumptionsforRestorationProcessusingIPRs. ..............22 3.4MathematicalformulationforSystemRestoration...............23 3.4.1Objectivefunction.. ..........................23 3.4.2Modelconstrains.............................24 vii

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3.5IPRsNetworkArchitecture...........................25 3.5.1Classi“cationofIPRs..........................26 3.6IPRsDecisionScheme..............................27 3.7IPRBasicNegotiationScheme.........................28 3.7.1BasicsalgorithmsforIPRsNegotiationscheme............28 3.7.2ExampleofbasicIPRsNegotiation...................30 3.7.3ImprovementtoBasicNegotiationScheme...............32 3.7.3.1Modi“cationstoImprovetheIPRsNegotiation.......33 3.7.3.2ExampleofthenewNegotiationscheme...........34 3.7.4Disadvantagesofmodi“cationofIPRs.................34 4Multi-stageIPRNegotiationscheme36 4.1Overview .....................................36 4.2Island-zoneapproach...............................36 4.2.1TypesofIPRs..............................37 4.2.2ZonesasPowerNetworkEquivalents..................38 4.3Negotiationintwophases............................39 4.3.1Intra-ZoneNegotiationphase......................39 4.3.1.1FriendlyRequeststage.....................40 4.3.1.2PersistentRequeststage....................42 4.3.1.3Loadsheddingcommunicationscheme............43 4.3.2Inter-zoneNegotiationphase......................47 4.4IPRsMessagestypes...............................50 4.4.1Normalstatemessages..........................50 4.4.2Contingencymessages..........................50 4.4.2.1Intra-zonemessages......................50 4.4.2.2Inter-zonemessages......................52 5ExperimentalResults53 5.1Introduction....................................53 5.1.1Prototypeoverview.. ..........................54 5.1.1.1Prototypestructure......................55 5.2Intra-zonescenarios...............................56 5.2.1WSCCnine-bussystem-ScenarioI..................56 5.2.2WSCCnine-bussystem-ScenarioII..................58 5.2.3WSCCnine-bussystem-ScenarioIII.................63 5.2.4WSCCnine-bussystem-ScenarioIV.................66 5.2.5WSCCnine-bussystem-ScenarioV..................68 viii

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5.2.6WSCC179-busSystem... ......................72 5.3Inter-zonescenarios................................87 5.3.1WSCCnine-bussystem.........................87 5.3.2WSCCnine-bussystem-interconnectedtwosystems... ......90 5.3.3WSCC179-busSystem... ......................93 5.4Experimentalresultssummary.........................98 6ConclusionandFutureWork99 6.1SummaryofContributions.. ..........................100 6.2FutureWork..... ..............................102 BIBLIOGRAPHY103 APPENDICES105 AMulti-stageNegotiationalgorithms106 A.1IPRsNegotiationalgorithms..........................106 A.1.1Intra-zonealgorithms..........................106 A.1.2Inter-zonealgorithms..........................113 ix

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LISTOFTABLES5.1ScenarioI-Simulationconditions-WSCCnine-bussystem.........57 5.2ScenarioI-Simulationresults-WSCCnine-bussystem...........59 5.3ScenarioII-Loadsstatus-WSCCnine-bussystem..............60 5.4ScenarioII-Generatorsstatus-WSCCnine-bussystem...........61 5.5ScenarioII-Busandlinesstatus-WSCCnine-bussystem.........62 5.6ScenarioIII-Loadsstatus-WSCCnine-bussystem.............65 5.7ScenarioIII-Generatorsstatus-WSCCnine-bussystem..........65 5.8ScenarioIII-Busandlinesstatus-WSCCnine-bussystem.........65 5.9ScenarioIV-Loadsstatus-WSCCnine-bussystem.............67 5.10ScenarioIV-Generatorsstatus-WSCCnine-bussystem..........67 5.11ScenarioIV-Busandlinesstatus-WSCCnine-bussystem.........68 5.12ScenarioV-Loadsstatus-WSCCnine-bussystem..............70 5.13ScenarioV-Generatorsstatus-WSCCnine-bussystem...........70 5.14ScenarioV-Busandlinesstatus-WSCCnine-bussystem.........71 5.15WSCC179-bussystem-Zone1-A-Generatorsstatus.. ..........78 5.16WSCC179-bussystem-Zone1-A-Loadsstatus. ..............79 5.17WSCC179-bussystem-Zone1-B-Generatorsstatus.. ..........80 5.18WSCC179-bussystem-Zone1-B-Loadsstatus. ..............80 5.19WSCC179-bussystem-Zone1-C-Generatorsstatus.. ..........81 5.20WSCC179-bussystem-Zone1-C-Loadsstatus. ..............81 5.21WSCC179-bussystem-Zone2-A-Generatorsstatus.. ..........82 5.22WSCC179-bussystem-Zone2-A-Loadsstatus. ..............83 5.23Generatorsstatus-WSCC179-bussystem-Zone2-B.. ..........84 5.24Loadsstatus-WSCC179-bussystem-Zone2-B. ..............85 5.25WSCCnine-bussystem-Inter-zonescenario-Zone1-Busandlinesstatus88 5.26WSCCnine-bussystem-Inter-zonescenario-Zone2-Busandlinesstatus89 5.27WSCCnine-bussystem-Inter-zonescenario-Generatorstatus.......89 5.28WSCCnine-bussystem-Inter-zonescenario-Loadsstatus.........89 5.29WSCCNine-bussystem-Interconnectedtwosystems-Zone1-Busand linesstatus....................................91 x

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5.30WSCCNine-bussystem-Interconnectedtwosystems-Zone1-Generator status.......................................92 5.31WSCCNine-bussystem-Interconnectedtwosystems-Zone1-Loadsstatus92 5.32WSCCNine-bussystem-Interconnectedtwosystems-Zone2-Busand linesstatus....................................92 5.33WSCCNine-bussystem-Interconnectedtwosystems-Zone2-Generator status.......................................93 5.34WSCCNine-bussystem-Interconnectedtwosystems-Zone2-Loadsstatus93 5.35WSCC179-bussystem-Zone1-A(Inter-zonescenario)-Generatorsstatus97 5.36WSCC179-bussystem-Zone1-A(Inter-zonescenario)-Generatorsstatus97 5.37WSCC179-bussystem-Zone1-A(Inter-zonescenario)-Loadsstatus...97 5.38WSCC179-bussystem-Zone1-B(Inter-zonescenario)-Loadsstatus...98 xi

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LISTOFFIGURES1.1ASlowresponsecouldcauseacascadefailures................3 1.2IPRSRespondPromptlytoAvoidFurtherDeterioration...........4 1.3OrganizationofEPNESprojectatUPRM...................5 2.1TheDNSnamespaceishierarchicallyorganizedintoatreeofdomains...9 2.2Networkrepresentedasagraph.........................11 3.1ModelingaEEDNasagraph ..........................21 3.2RelationbetweenEEDN,IPRslocationandIPRlogicalconnections.(Gen n:Generatorn,SrcPR:sourcePowerRouter,PPR:PrincipalPowerRouter, SnkPR:SinkPowerRouter)...........................26 3.3Load1isun-servedbecauseLine1hasafailure................31 3.4ExampleofIPRsNegotiationProcess......................32 3.5DisadvantageofIPRsBasicnegotiationscheme................33 3.6ExampleoftheIPRsNegotiationschememodi“ed..............35 4.1ExampleofIsland-zoneapproach........................37 4.2NetworkequivalentofzoneAforzoneB4.1..................39 4.3ExampleofFriendlystage.Power”owsinsteadystate............41 4.4ExampleofFriendlystage.Restorationprocess................42 4.5ExampleofPersistentstage.Restorationprocess...............44 4.6ExampleofLoadShedding.Restorationprocess-sectiona.........46 4.7ExampleofLoadShedding.Restorationprocess-sectionb.........46 4.8ExampleofLoadShedding.Restorationprocess-sectionc.........47 4.9ExampleofInter-zoneNegotiation.Systemconditions............48 4.10ExampleofInter-zoneNegotiation.Negotiationprocess...........49 5.1PrototypeStructure...............................55 5.2ScenarioI-WSCCNine-bussystemmodi“ed.................57 5.3ScenarioII-WSCCnine-bussystem......................60 5.4ScenarioIII-WSCCnine-bussystem.....................63 5.5ScenarioIV-WSCCnine-bussystem.....................66 5.6ScenarioV-WSCCnine-bussystem ......................69 5.7WSCC179-busmodel ..............................73 5.8WSCC179-busmodel-Zone1-A.. ......................74 5.9WSCC179-busmodel-Zone1-B.. ......................74 5.10WSCC179-busmodel-Zone1-C.. ......................75 xii

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5.11WSCC179-busmodel-Zone2-A.. ......................75 5.12WSCC179-busmodel-Zone2-B.. ......................76 5.13WSCCNine-bussystem-Inter-zonescenario.................87 5.14WSCCNine-bussystem-Interconnectedtwosystems.. ..........90 5.15WSCC179-busmodel ..............................95 5.16WSCC179-busmodel-Inter-zonescenario-Zone1-B.. ..........96 xiii

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CHAPTER1Introduction1.1OverviewEverysocialandeconomicfunctionofoursocietydependsonthesecureandreliableoperationoftheelectricpowernetwork[1].ExistingPowerDeliverySystemsare designedwithredundantpowergeneratorsanddeliverylinestomakethesystemtolerant tofailuresontheseelements[2].However,thecontrolandcoordinationoftheprocessto generate,transmit,anddistributepowerstilloccursinacentralizedmanner,withonlya fewsites(controlcenters)managingmission-criticaltasksforpowergenerationanddelivery [3].Thiscentralizedschemehasacleardrawback:afailureinoneofthesecontrolcenters mightresultinthetotalcollapseofthesystem.Therefore,itishighlydesirablethatfutureElectricalEnergyDistributionNetworks(EEDN)havethecapabilitiesforautomating anddistributingthetasksofcoordinatingandcontrollingthepowergeneration,transmission,anddistributioncomponentswhencontingenciesoremergencysituationsoccur[1]. Ourideaistohaveenoughintelligenceandredundancythroughoutthesystemtosurvive failures,andthenquicklyrecoverfromthem. 1

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21.2ProblemStatementOursocietyishighlydependantonEEDNthereforeitshighreliabilityisalways required.Wheneveragroupofconsumersarede-energizedbyafailureintheEEDN,it isnecessarytorestoretheelectricalserviceassoonaspossibletoenabletheconsumersto continuewiththeiractivities.Currently,EEDNarecontrolledfromacentralizedcontrol centerthatreceivesmeasurementfrompowergeneratorandtransmissionlines.Whenan electricpowersupplyinterruptioniscausedbyafaultinanysystemcomponent;engineers andoperatorsatthecommandcenterstartworkingtopromptlyrestorethepowersystem toanoptimaltargetcon“gurationthroughaPowerRestorationProcess[2].Thus,Power Restorationistheprocessperformedbythecontrolcenterafterafaultorblackoutoccurrenceinwhichthesystemelementsarerecon“guredandre-energizedwiththeobjective ofrestoringtheservicetoasmanyde-energizedconsumers(calledŽloadsŽ)aspossible. Toobtainthetargetcon“gurationinarestorationprocess,variousapproacheshavepreviouslybeenproposed,whichcanberoughlyclassi“edintofourcategories:heuristics,expert systems(ESs),mathematicalprogramming(MP),andsoftcomputing[2].But,allthese restorationmethodsarecentralizedprocessesthatarelaunchedandcoordinatedfromthe controlcenter. Thequestionthatmustberaisedhereis:whatwouldhappenifthecontrolcenter isalsoaectedbythefault?Inaddition,therestorationprocesscouldbeaslowand errorproneprocessduetofactorssuchas:a)overwhelmingamountofdata,b)misscommunicationsonthepartofoperators,c)lackofcoordinationbetweenelectricutilities sharingthepowergrid,ord)lackofaccuratemeasurements.Thecriticalissue,asshown in“gure1.1,isthataslowresponseduringacontingencycouldgenerateacascadeeect aectingmoreportionsofthesystem,andevenatotalsystemcollapse[1].

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3 Figure1.1:ASlowresponsecouldcauseacascadefailures1.3ProposedSolutionAttheUniversityofPuertoRico-Mayaguez,intheElectricPowerNetworksEciencyandSecurity(EPNES)project(sponsoredbyNationalScienceFoundation(NSF)), wearecurrentlydevelopingtechnologiesforanextgenerationofEEDNbasedonadistributed,de-centralizedframeworkforcontrolandcommunicationbetweensystemcomponents.Inourframework,theintelligencethatcanbeusedforcontrolandcoordinationoperationsisembeddedintoaseriesofcomputingdevicescalledtheIntelligentPowerRouters (IPRs)[1].TheseIPRsarestrategicallyconnectedtopowergeneratorsandpowerlines, thusenablingthemnotonlytoobservecurrentnetworkconditions,butalsocooperatewith eachtoactivealternatelinestomovepowerfromproducerstoconsumers[1].Forexample, whenpowerislostonagivenregionduetoageneratorfailure,severalIPRsinchargeof thatregionmightaskanothergeneratortoincreasepowersupplyandthencoordinateto openalternatelinestobringenergyintotheaectedregion.Ourgoalistoshowthatby distributingnetworkintelligenceandcontrolfunctionsusingtheIPR,wewillbecapableof

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4 achievingimprovedsurvivability,security,reliability,andre-con“gurabilityasitoccursin DataNetworks[4].Thisapproachborrowsfromcomputernetworks:a”owofdataneeded tobeestablishedbetweentwogeographicallydistantend-pointsisimplementedviadata routersandforwardingprotocols.Thesedatarouterscooperatebymovingpiecesofdata overthenetworkuntilthedatareachesthedesireddestination(s).TheIPRsinanEEDN couldoperateinsimilarfashionwithdueconsiderationofthephysicaldierencesbetween dataexchangeandenergyexchange[1]. TheIPRsNetworkwillbebuiltwithaPeer-to-Peer(P2P)oramesharchitecture inwhich,foragivenIPR,itshouldbeirrelevantwhetheritsinputscomefrompower producersorotherIPRs[1].Intheeventofacomponentorsystemfailure,theIPRswill makelocaldecisionsandcoordinatearestorationprocesswithotherrouterstobringthe systembacktooperation,asshownin“gure1.2. Figure1.2:IPRSRespondPromptlytoAvoidFurtherDeterioration But,theproposedschemewillnotsubstitutecurrentcontrolprotocolsifthereare

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5 nocontingencies.However,undernormaloperatingconditions,theIPRswouldprovide additionalinformationonsystemstatustothecentralenergymanagementsystem.The IPRwillallowthesystemtooperateindegradedoperationduringmajorcontingencies[1]. Intheapproachpreviouslyoutlinedisobviousthenecessityofarobustprotocol fordistributedcontroltocoordinatealltasksofIPRsnetwork.Figure1.3showstheorganizationoftheEPNESprojectintheUPRM.Thisthesisisinvolvedinthesectionsofthe IPRProtocolsandRestorationModels.Inthisdissertation,wepresentaspectsassociated withthedesignofthisdistributedprotocolforIPRsandseveralalgorithmstoperform restorationprocessinadistributedway. Figure1.3:OrganizationofEPNESprojectatUPRM1.4ObjectivesofthisThesisThemainobjectivethisthesisistodesignthecommunicationprotocolsandnegotiationschemetoIntelligentPowerRouterstoachievePowerSystemRestoration.

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6 € TodesigntheIPRsNetworkArchitecture € TodesignareliableControlprotocolsforIPRsnetwork,de“ningmessagestypes, communicationschemesandroutingalgorithms. € TodesignthenecessaryAlgorithmsfornegotiationduringsystemrestoration. € Todevelopafunctionalprototypewithcapabilitiestonegotiatepowerrequestbetween IPRsinanetwork.1.5ContributionsThemajorcontributionsofthisthesiscanbesummarizedasfollows: 1.WehaveestablishedamappingbetweenElectricalEnergyDistributionNetworks (EEND)andWideAreaNetwork(WAN). 2.Designofthearchitectureandcommunicationprotocolsandnegotiationschemefor distributednegotiationforpowersystemrestorationusingIPRs,thiswillcomplement butnotsubstituteexistingcontrolmechanisms. 3.DemonstrationofthefeasibilityofIPRSthroughseveralexperiments,theobtained resultsshowsuccessfulrestorationplanformajorcontingency.1.6ThesisStructureTheremainderofthisthesisisstructuredasfollows.Chaptertwopresentsasurvey ofrelatedworkarrangedinfoursubtopics:i)Poweranddeliverysystems;ii)Computing networksandroutingprotocols;iii)Distributedsystemsandiv)Peer-to-peerarchitecture. ChapterthreepresentsthebasicconceptsassociatedwiththeofIPRnetworkdiscussingi) MappingofElectricalEnergyDeliveryNetworks(EEDN)asaWideAreaNetwork-WAN; ii)mathematicalformulationofanobjectivefunctionwithitsassociatedconstraints;andiii)

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7 IPRNetworkarchitecture1.ChapterfourpresentstheIPRsNetworkmulti-stagenegotiation schemeanditscomponentsdescribingi)DesignforIPRarchitectureanddistributedcontrol protocol;ii)island-zoneapproachiii)Messagetypesandiv)Algorithmsassociatedwith IPRs.Chapter“vepresentstheexperimentsandtheresultsobtained.Finally,Chaptersix presentsthe“nalconclusionsandfuturework. 1Anetworkarchitecturecanbedenedastheorganizationofthenetwork,specifyingtherolesofeach elementandtheirrelations.

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CHAPTER2RelatedWork2.1OverviewInthischapter,wepresenthererelevantworkuponwhichthisthesisisbased. Theareasarea)DistributedSystems,b)ComputingNetworksandRoutingProtocols,c) Peer-to-PeerNetworks,d)Multi-agenttechnologiesande)ElectricalPowerSystem.2.2DistributedSystemsAdistributedsystemisacollectionofindependentcomputersthatappearstoits usersasasinglecoherentsystem[5].Themaingoalofadistributedsystemistomake iteasyforuserstoaccessremoteresources,andtosharethemwithothersusersina controlledway.Likewise,anotherimportantgoalofadistributedsystemistransparency,a distributedsystemthatisabletopresentitselftousersandapplicationsasifitwereonly asinglecomputersystemissaidtobetransparent. Distributedsystemsshouldalsoberelativelyeasytoexpandorscaleasaconse8

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9 quenceofhavingindependentcomputers.But,whenasystemneedstoscaleverydierent typesofproblemsneedtobesolvedsuchasproblemswithperformanceandcommunications.Oneoftheseproblemiscausedbyanenormousnumberofmessagethathavetobe routedovermanylines.TocombatthisproblemthereexistsatechniquecalledDistribution. Distributioninvolvestakingacomponent,splittingitintoasmallerparts,andsubsequently spreadingthosepartsacrossthesystems.DomainNameSystem(DNS)isagoodexample ofdistributionintheInternet.TheDNSnamespaceishierarchicallyorganizedintoatree ofdomains,whicharedividedintonon-overlappingzone[5]. intcomedugovmil org netjpusnl sun eng yale eng ailinda robot acm jackjill ieee keio cs cs pc24 co nec csl ocevu cs flitsfluit ac GenericCountries Z1 Z2 Z3 Figure2.1:TheDNSnamespaceishierarchicallyorganizedintoatreeofdomains Currently,thedevelopmentofnewDistributedSystemisstronglysupportedby theacademic,scienti“candindustrialcommunity.Anexampleofthesedevelopmentsisthe GridComputinginnitiative.TheearlyeortsinGridcomputingstartedasprojectstolink USsupercomputingsites,butnow,therearemanyapplicationsthatcanbene“tfromthe Gridinfrastructure,includingcollaborativeengineering,dataexploration,high-throughput

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10 computing,andofcoursedistributedsupercomputing[6]. AnotherexampleofDistributedSystemistheMiddlewaresystem.Essentially, middlewareisadistributedsoftwarelayer,orplatformwhichabstractsoverthecomplexityandheterogeneityoftheunderlyingdistributedenvironmentwithitsmultitudeofnetworktechnologies,machinearchitectures,operatingsystemsandprogramminglanguages[6]. Threeprogrammingmodelsarethemostusedinmiddlewaredevelopments.The“rstisthe objectbasedmiddleware,inwhichapplicationsarestructuredintoobjectsthatinteractvia locationtransparentmethodinvocation(e.g.OMGsCORBAandMicrosoftsDistributed COM).ThesecondmodelisEventBasedMiddleware,whichisparticularlysuitedtothe constructionofnon-centralizeddistributedapplicationsthatmustmonitorandreactto changesintheirenvironment(e.g.processcontrol,Internetnewschannelsandstocktracking).Itisclaimedthateventbasedmiddlewarehaspotentiallybetterscalingproperties forsuchapplicationsthanobjectbasedmiddleware[6].Finally,thethirdmodelisMessageorientedmiddlewareanditisbiasedtowardapplicationsinwhichmessagesneedtobe persistentlystoredandqueued(e.g.Work”owandmessagingapplications).2.3ComputerNetworksandRoutingProtocolsThemainfunctionofthenetworklayeroftheprotocolstackTCP/IPisrouting packetsfromsourcetodestinationmachines.Theroutingalgorithmisthatpartofthe networklayersoftwareresponsiblefordecidingwhichoutputlineshouldbeusedtotransmit anincomingpacket.Routingis,inessence,aproblemofgraphtheory[4].Figure2.2shows anetworkrepresentedasagraph.Thenodesofthegraphmaybehosts,switches,routers ornetworks.Theedgesrepresentnetworklinkswithanassociatedcost,whichgivessome indicationorcostofthedesirabilityofsendingtracoverthatlink. Thebasicproblemofroutingisto“ndthelowest-costpathbetweenanytwonodes,

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11 Figure2.2:Networkrepresentedasagraph wherethecostofapathequalsthesumofthecostofalledgesthatmakeupthepath[4]. Routingalgorithmscanbegroupedintotwoclasses:Non-adaptivealgorithmsand adaptivealgorithms.The“rstarestaticandtheydonotmakedecisionsbasedoncurrent tracconditionsandtopologyofthenetwork;Adaptivealgorithms,ontheotherhand, changetheirroutingdecisiontore”ectchangesinthenetwork.DistanceVectorRouting (RIP)andLinkStateRoutingAlgorithmbelongtothesecondgroupandtheybuildrouting tablesbasedonshortestpathapproach. IntheDistanceVectoralgorithmeachnodeconstructsaone-dimensionalarray containingtheŽdistancesŽ(costs)toallothernodesanddistributesthatvectortoits immediateneighbors.ThebasicideabehindtheLinkStateRoutingprotocolis:Everynode knowshowtoreachitsdirectlyconnectedneighbors,andifwemakesurethatthetotalityof thisknowledgeisdisseminatedtoeverynode,theneverynodewillhaveenoughknowledge ofthenetworktobuildacompletemapofthenetwork.Reliable”oodingisthemechanism usedtoachievethisidea.Inthisapproacheachnodesendsitslink-stateinformationouton allofitsdirectlyconnectedlinks,witheachnodethatreceivesthisinformationforwarding itoutonallofitlinks,exceptthesourcelink.Thisprocesscontinuesuntiltheinformation

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12 hasreachedallnodesinthenetwork[4]. AWideAreaNetwork(WAN),suchastheInternet,isorganizedasinterconnected AutonomousSystems(AS),eachofwhichisundercontrolofasingleadministrativeentity andcanuseitsownroutingalgorithminside.AnInteriorGatewayProtocol(IGP)is aroutingalgorithmusedinsideanAS,whileaExteriorGatewayProtocolisanrouting algorithmsusedbyanAStocommunicatewithanotherAS. Allaninteriorgatewayprotocolhastodoismovepacketsasecientlyaspossible fromthesourcetothedestination.Itdoesnothavetoworryaboutpoliciesofuseofan AS[7].OneofInteriorGatewayProtocol(IGP)mostwidelyusedisOpenShortestPath FirstProtocol(OSPF)thatisalink-stateroutingprotocoldesignassuccessoroftheoriginal IGPusedintheInternet. Exteriorgatewayprotocolroutershavetoworryaboutusagepoliciesagreatdeal. TheBorderGatewayProtocol(BGP)hasbeendesignedtoallowmanykindsofrouting policiestobeenforcedintheinter-AStrac,suchaspreventingtracthroughcertainAS (e.g.,tracstartingorendingatIBMshouldnottransitMicrosoft). Everyroutingprotocolhavebeendesignedtoreducecongestionandimprovenetworkperformance.However,withthegrowthofmultimedianetworking,oftentheseprotocolsarenotenough.TheResourcereSerVationProtocol(RSVP)isaproposalfora protocoldesigntoreserveresourcesacrossacomputernetworktoguaranteequalityofservicesuchasportionsofbandwidthacrosscommunicationnetwork.Thisprotocolisoriented tomultimediaapplicationslikevideotransmission.RSVPisreceiver-oriented:thereceivers ofthedata”owareresponsibleofinitiatingtheresourcereservationandmaintainingthe reservationthroughtimeusingbymeansofcon“rmationmessages.

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132.4Peer-to-PeerNetworksTheclient/servermodeldescribestherelationbetweentwocomputerprocesses programswhereoneofthem(theclient)sendsaservicerequesttoother(theserver).This serverrespondstotheclientrequest,butonlytheclientcanmakearequesttotheserver,no otherwise.Theclient/servermodelisbasedonadistributedmodelforstorage,processing andaccesstodata.Generally,serversarepowerfulcomputersorprocessesdedicatedto managingdiskdrives(“leservers),printers(printservers),ornetworktrac(network servers).Clientsareworkstationsonwhichusersrunapplications.Clientsrelyonservers forresources,suchas“les,devices,andevenprocessingpower. AnothertypeofnetworkarchitectureisknownasaPeer-to-Peer(P2P)architecture becauseeachnodehasequivalentcapabilitiesandresponsibilities,inotherwords,apeer-topeernetworkisanetworkthatdoesnothaveacentralcomputer(s)ordedicatedserver(s). Everyelementisbothaclientandaserver.Inapeer-to-peernetworkeverycomputeracts onitsownandisnotdependentonanothercomputerorserver,anditallowsindividual computerstocommunicatedirectlywitheachotherandtoshareinformationandresources withoutusingspecializedservers[8]. ThisP2Parchitectureinthepasthadbeenappliedprimarilyinsmallernetworks oflessthanadozencomputers.However,recentlywehaveseenanexplosivegrowthin theuseof“le-sharingsoftwareinordertoexchangedigitalaudio,videoandothertypesof “les.ThetrendwasstartedbyNapster,whichallowssharingofMP3music“lesamong anarbitrarysetofusers.Thereexistnumerousvariantsof“lesharingsoftwareincludingWrapster(aslightgeneralizationofNapster)andMorpheus(whichprovidesgeneral “lesharingwithoptimizeddownloadalgorithmsusingmultiplecopiesbasedontheFastTrackprotocol).Concurrently,distributedversionsof“le-sharinghavealsobeendeveloped, includingGnutellaandFreenet[9].

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14 Finally,theuseofP2Parchitecturesopensupnewdimensionsofhandlingand managingtheinformationfacilitatingtheexchangeofthemostrecentlycreatedandhighly distributedinformation.ThedecentralizedP2Psystemprovidesthepotentialtoberobust tofaultsorintentionalattacks,makingthemidealforlong-termstorage[10].2.5Multi-agentsTechnologiesAnautonomoussystemisasystem,whichcanreactintelligentlyand”exiblyon changingoperatingconditionsanddemandsfromthesurroundingprocesses[11].Anagent actsautonomouslyonthebaseofinformationfromtheenvironmentorotheragents.If someinformationismissingtheagentsubstitutesautonomouslyitsoriginalactionscheme byanewonewithoutthisinformation[11].Beyondthisbehaviorofsingleagents,teams ofagentsshallbeenabledtoachieveacommongoal[11]. Twobasiccon“gurationsofagentsareagroupofagentswithdierentsubtasksand groupsofagentsofthesamekindandthesamehierarchicallevel.The“rstcon“gurationis coveredbytheautonomoussystemde“nitioninwhichautonomouscomponentsasagents requestandprovideinformationtootheragents.Thesecondcon“gurationneedsparticular methodslikenegotiationtoreachglobalgoalswhilekeepinglocalconstrains[11]. Multi-agentcoordinationandcooperationisabasicissueofmulti-agentsystem (MAS).Besidestheresearchandimplementionofcooperativeagentteamwork,communicationamongagentsalsoplaysanimportantrole[12].Communicationprotocolsenable agentstoexchangeandunderstandmessage.Interactionprotocolsenableconversation throughstructuredexchangesofmessages[11].Coordinationmethodsservetoestablish conversationbetweenagents.Coordinationisbasedoncommunicationandindividual decision-making.

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15 Cooperationiscoordinationamongnon-antagonisticagents,whilenegotiationis coordinationamongcompetitiveorself-interestedagents.Thelastmechanismdoesnot requireacentraldecisionmakerormanaginginstance.Theagentshavetoexchangetheir actualstatusorpositionandthentrytosolvepossiblecon”ictsbythemselves.Theagents needanegotiationschemeandadecisionprocessthateachagentusestodetermineits positions,concessionsandcriteriaforagreement[11].Awayofdescribingthenegotiation isbasedontheassumptionthattheagentsareeconomicallyrational.Agentscreateadeal thatisajointplanbetweentheagentsthatwouldsatisfytheirgoals.Eachagentwantsto maximizeitsownutility.Theagentsdiscussanegotiationset,whichisthesetofalldeals thathaveapositiveutilityforeveryagent.2.6ElectricalPowerSystemsAnElectricalPowerSystemcanbede“nedasagroupofoneormoregenerating resourcesandconnectingtransmissionlinesoperatedundercommonmanagementorsupervisiontosupplyconsumers[13].Apower-deliverysystemiseverythingthatexistsbetween powergeneration(e.g.generators,batteries,etc.)andthespeci“cconsumerofpower(e.g. computers,motors,weaponsystems,etc.).Apower-deliverysystemisformedbytheTransmissionsystemandtheDistributionsystem.Thetransmissionsystemecientlytransmits largeamountsofelectricalenergyoverlongdistancesandathighvoltage.Whenthishigh voltageelectricityarrivesatamajorloadcenter,thevoltageisreducedtomaketheelectricitymoresuitabletobesenttotheindividualconsumers[13].TheDistributionSystem transmitselectricalenergybetweentransmissionsystemand“naluser.Ancharacteristic ofDistributionsystemsistheuseofanetworkwithradialcon“guration(withoutloops), whilethetransmissionsystemusesnon-radialcon“gurationsforthenetwork. Obviouslyinamodernpowerdeliverysystem(PDS)thereareliterallyhundreds

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16 ofdevices,subsystemsandcontrollers,etc,whichareusedtodistribute,switch,control andmakedecisionsaboutthehealthandfunctionalityofthePDSitself.Powerdelivery systemsareusedinapplicationsfromshipsandsubmarinestocommercialbuildings.The coordinationprocessoftheseelementsrequiresophisticatedmethodsandtechnologies,asit ispresentedin[14].Theadventofpowerindustryderegulationhasplacedgreateremphasis ontheavailabilityofinformation,theanalysisofthisinformation,andthesubsequent decision-makingtooptimizesystemoperationinacompetitiveenvironment.Intelligent electronicdevices(IEDs)beingimplementedinsubstationscontainvaluableinformation, bothoperationalandnon-operational,neededbymanyusergroupswithintheutility.The challengefacingutilitiesisdeterminingastandardintegrationarchitecturethatmeetsthe utilitysspeci“cneeds,canextractthedesiredoperationalandnon-operationalinformation, anddeliverthisinformationtotheuserswhohaveapplicationstoanalyzetheinformation. Theworkin[15]presentsamulti-agentsystemthatitconsistsofseveralFacilitatorAgents(FAGs),Equipment-Agents(EAGs)andSwitch-Box-Agents(SBAGs).AFAGacts asamanagerforthenegotiationprocessbetweenagents.EAGcorrespondstoanequipment oftheelectricpowersystemsuchasabus,atransformerandatransmissionline,while SBAGisapseudo-objectwhichconsistsofneighboringcircuitbreakersanddisconnecting switches.Theproposedmulti-agentsystemrealizesappropriateswitchingoperationsby havingagentsinteractwithneighboringagents. Onotherhand,thetermBlackoutreferstoaneectthatcauseanentirepowersystemtobede-energized.Severalcontingenciesmightcausetheblackoutsuchas:a)generator failure,b)damagetotransmissionlinesorc)damagetodeviceliketransformers.Thedurationoftheblackoutcanbeminutes,hoursordays.Obviously,thelongertheblackout theworstitsimpactwillbeontheconsumers.Powersystemrestorationistheprocess necessarytorecon“gureandr-energizedtheelementsinthepowersystemtorestoreservice toasmanyconsumersaspossible[2].Afterasystemblackout,itisnecessarytocarry

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17 arestorationprocesstobringbacktheelectricnetworkintoanoperational(butperhaps degraded)state.Toobtainthetargetcon“gurationinarestorationprocess,variousapproacheshavebeenproposedsofar.Theseapproachescanberoughlyclassi“edintofour categories:heuristicssearchalgorithms,expertsystems(ESs),mathematicalprogramming (MP),andsoftcomputing[1]. Multi-agentssystemrestoration,presentedin[2],consistsonamulti-agentapproachtopowersystemrestorationprocessformedbyanumberofbusagents(BAGs)and asinglefacilitatoragent(FAG).BAGisdesignedtodecideasuboptimaltargetcon“gurationafterafaultoccursbyinteractingwithotherBAGs,whileFAGisdesignedtoact asamanagerforthedecisionprocess.Whenasystemportionisde-energized,theBAGs aectedsendarequesttosystemFAG,andthischooseswhichBAGsrequestareaccepted forrestoration.

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CHAPTER3ModelDescriptionandIPRs NetworkArchitecture3.1OverviewTheIPRsschemeattemptstoquicklygenerateasystemrestorationsolutionthrough distributedcoordinationinasimilarfashiontodataroutersinaWide-AreaNetwork.3.2MappingofElectricalEnergyDistributionNetworks(EEDN) toaWideAreaNetwork(WAN)AWide-AreaNetwork(WAN)isacomputernetworkformedbyasetofelements thatcanmovedataovergeographicallydistantnodes[7].Whena”owofdataneedstobe establishedbetweentwoendpoints,theseelementscooperatebymovingpiecesofdataover thenetworkuntilthedatareachesthedesireddestination(s).Likewise,anElectricalpower systemisformedbyasetofcomponentsinterconnectedinanelectricaltransmissionand 18

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19 distributionnetwork;thislatternetworkis,inprinciple,similartoaWide-AreaNetwork (WAN)suchastheInternet.3.2.1Network-owproblemADatanetworksistypicallyrepresentedasadirectedweightedgraph.Animportantprobleminthistypeofgraphisthemaximum”owproblem.Inthisproblemeach edgerepresentsaŽpipeŽthatcantransportsomecommodityandtheweightoftheedges representsthemaximumamountthatitcantransport.Themaximum-”owproblemisto “ndawayoftransportingthemaximumamountofthegivencommodityfromsomevertex s,calledthesourcetosomevertext,calledthesink[16]. A”ownetworkNconsistsof: € AconnecteddirectedgraphGwithnon-negativeintegerweightsontheedgescalled ŽcapacityŽ. € Twodistinguishedvertices,source(s)andsink(t)nodes,suchthatshasnoincoming edgesandthasnooutgoingedges. A”owfornetworkNisanassignmentofanintegervaluef(e)toeachedgeeofG thatsatis“esthefollowingproperties[16]: € ForeachedgeeofG,the”owassignedmustbenogreaterthantheedgescapacity (capacityrule). € ForeachnodevofG,theincoming”owmustbeequaltooutgoing”ow(conservation rule). TherestorationprocessforpowersystemscanberepresentedasaNetwork”ow problemandsolvedusinggraphtheoryasispresentedin[17].

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203.2.2SimilaritiesofanEEDNwithaWANThefactthatanEEDNandaWANareformedbyasetofelementsdesignedto transmitaproduct(energyordata)fromproducerstoconsumers,permitsustoestablisha mappingbetweenEEDNElementsandComputerNetworkElements.Figure3.1(a)shows thetypicalcon“gurationforaEEDN,and“gure3.1(b)depictsagraphmodellingthe EEDN.WenowpresenttherolesforeachofthecomponentsofanEEDN,andestablisha parallelwithaWAN: € PowerProducers :Thesearetheelementsinchargeofgeneratingelectricenergy. Theycanbenucleargenerators,hydraulicgenerators,thermalgeneratorsoreven anarrayofbatteries.TheyareoftencalledŽ generators Žandtheywouldbethe equivalentofdataserversinaWAN.Inanetwork”owgraphrepresentationthe producerarethesourcenodes. € Powerconsumers :Theconsumersaretheclientsoftheelectricalsystemsuchas hospitals,ocebuilding,malls,etc.TheyaretypicallycalledtheŽloadsŽandthey wouldbetheequivalentofclientapplications.Inournetworkgraphrepresentation theloadsarethesinknodes. € Transmission/Distributionlines :theyareinchargeoftransferringelectrical powerfromproducers(generators)toconsumers(loads).InaWANthesecomponentswouldbedatalinks.InanetworkgraphrepresentationtheTransmissionlines areedgesandthepower”owdirectionisthedirectionoftheedges. € Buses :Theyareasetofinternalnodeswhichtheelectricaltransmissionlinesare connectedto.InaWAN,buseswouldbeequivalenttodataroutersanddataswitches. InaNetwork”owgraph,busesareinternalnodesinthegraph.

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21 Figure3.1:ModelingaEEDNasagraph3.2.3OperationinWANWhenadataclientsendsaninformationrequesttoadataserver,thisserver fragmentsthedatarequestedinpacketsandtheyaresenttotheclientacrossthenetwork. Thepacketsarethebasicunitofdatathatcanbetransmittedonacomputernetwork[7]. Ateachstepofthisprocess,arouterthatreceivesadatapacketdeterminesthenextrouter thatshallforwardthatfragmentofdatauntilthedatareachesthedesireddestination(s). Noticethattheremightbemanycandidaterouters,buttheonethatcandothebest forwardingjobistheonethatisselected. Ifanyrouterorlinkofthesystemfails,therouterswillre-con“gurethepathsto routethepackets,sothattheclientsarenotaectedbysuchfailure.Inourview,aEEDN couldoperateinsimilarfashionwithdueconsiderationofthephysicaldierencesbetween dataexchangeandenergyexchange.

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223.3AssumptionsforRestorationProcessusingIPRsThePowersystemfailuresmaybecausedbystorms,failuresoftheprotection system,failuresofhigh-voltageequipment,excessivecustomerdemand,humanerrors,sabotage(vandalismorterrorism)andothermajordisturbances[2].Powersystemrestoration problemisaverycomplexcombinationalproblemthatcanbeformulatedasamulti-stage, non-linear,continuousandbinaryconstrainedoptimizationproblem.Themainobjective ofthisprocessistorestoreservicetoloadsasquicklyaspossiblekeepingafeasiblecon“gurationinallstages[18]. Currently,thepowersystemrestorationprocesscommonlyconsistsoftwomain sequentialsteps.First,theoptimalsystemcon“gurationtargetisobtainedfromthesetof feasiblecon“gurations.Second,switchingoperationsareperformedinordertoachievethe optimaltargetcon“gurationobtainedinthe“rststep,maintainingthesystemoperating withinitsfeasiblelimits[18].Thatmeansallbusvoltagemagnitudes,transmissionline”ows (activeandreactivepower),andgeneratorpoweroutputsarewithintheircorresponding feasiblelimits[18]. Inthisthesis,weassumethepowersystemrestorationproblemasaNetwork Flowproblemwherethecommodityinthenetworkisonlytheactivepower.Theother aspectsinvolveinastandardpowersystemrestoration,suchasvoltages,systemfrequency andreactivepower,arenotinvolvedintonegotiationschemeproposedforIPRsinthis thesis.Likewise,thenegotiationprocessperformedbyIPRswillnotincludetheswitching operationsorder.Alltheseissuesareconsideredaselementsofthefutureworks.

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233.4MathematicalformulationforSystemRestorationThe“rststeptoapplyComputerSciencetoapowerrestorationproblemisto understandthatpowerrestorationisanoptimizationproblem,andithasanobjective functionwithasetofassociatedconstraints.Ourmathematicalmodelisamodi“cationof amathematicalformulationpresentedin[2].3.4.1ObjectivefunctionTheobjectiveofthemathematicalmodelofthispowersystemrestorationapproach istomaximizethenumberofservedloadswiththehighestpriority.Inotherwords,after afaultoccurs,themodelshallseektorestoreasmanyofthemostimportantloadsas possible.Inthisscheme,eachload Lkhasapriority Prk,whichisanumberintherange[1, M].Thisnumberindicatestherelativepriorityofagivenloadwithrespecttootherloads inthesystem.Priorityvaluescloseto1indicatehigh-priority,whereasvaluesclosetoM indicateloadswithrelativelylowpriority.Theobjectivefunctionisgivenbythefollowing mathematicalexpression: Max kRLk yk ( Š Prk) Where PrkistheloadPriority(thehighestpriorityloadwillhavePr=1,the secondpriorityloadwillhavePr=2andlikewisetheotherloads), isanaturalnumber largerthanthePrvalueoflesspriority, Lkiseachloadinthesystem, ykisadecision variable( yk=1:load LkisRestored, yk=0:load Lkisnotrestored),andRde“nesthe setofde-energizedloads.Ourgoalisforouralgorithmstoattempttorestoreasmany priority-1loadsaspossiblewithoutviolatinganyconstraints.Then,movetothepriority-2 loadsandrestoreasmanyaspossible.Therestorationcontinuesuntileitherallpriority classeshavebeenexploredornomorepowerisavailabletobringanyotherloadbackinto

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24 thesystem.3.4.2ModelconstrainsTheconstraintsassociatedwithourmathematicalmodelaresimilartotheconstraintsintherestorationmodelpresentedin[2]: € Powerbalanceofthesystembetweensupplyanddemand .AtypicallyEEDN doesnothavebuersforstoringenergybecauseenergybuersarenotcost-eective; then,allpowergeneratedmustbeconsumedbytheloads.Inmathematicalterms: thesumofpowergeneratedbythesystemmustbeequalthatthesumofthepower consumedbyalltheloads(loadsinnormalstateandrestoredafterblackout).This constraintisde“nedby: kMGkŠ kRL xkŠ iNLi=0 Where Gkisthepowergeneratedbygeneratork, LkisPowerdemandedbyloadk, xkisadecisionvariable( xk=1:includedinrestorationpath, xk=0:noincluded), LiisPowerdemandedbyloadi,Risthesetofloadforrestorationoperation,Nis thesetofloadinnormalstateandMisthesetofgeneratorsinthesystem. € Limitsonpowersourceavailableineachbusforrestoration. Foreachnode ofthesystem,the”owofpowerinoutputlinescannotbegreaterthanthesumof poweravailableininputlines.Inotherwords,anodecannotgivemoreelectrical powerthatitcanreceive.Thisconstraintisde“nedby: eFqPe xe Gq( qS ) Where PemeansPower”owinbranche, xeisadecisionvariableforlinee( xe=1: includedinrestorationpath, xe=0:notincluded), GqrepresentsthePoweravailable inbusq. Fq:branchesconnectedtobusqandSisthesetofbusesinthesystem.

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25 € Limitsinlinecapacityforpowertransmission. Foreachlineinthesystemthe power”owcannotbegreaterthanthelinecapacity,independentof”owdirection. | Pk| Uk( kB ) Where Pkispower”owinlinek, Ukispower”owcapacityoflinekandBissetof alllinesatthesystem.3.5IPRsNetworkArchitectureThekeyofourapproachisthattheIPRsareawareofthesystemstateatall times.WeassumethatthereisoneIPRineachofthebusesinthesystemsotheycanbe alwaysmonitoringthesystemlines.Inaddition,therearespecialpurposeIPRsassociated withthepowergeneratorsandwiththeloads.Weassumethatwearedealingonlywitha transmissionsystem,butourideasalsoapplytoadistributionsystem.Figure3.2(a)shows asystemwithfourbuses,threegeneratorsandtwoloads.Figure3.2(b)showstheIPRsthat correspondtothiscon“guration.EachIPRhasasetofoutputlinesthatconnecttheIPR tootherIPRsortoloads.Likewise,eachIPRhasasetofinputlinesthatconnecttheIPR tootherIPRsortogenerators.Theseoutputandinputlinescorrespondtotransmission linesthatmovepowerbetweenthebusesassociatedwitheachIPRs.Inputlinesmodela transmissionlinethanbringspowerintothebusassociatedagivenIPR.Likewise,output linesmodelatransmissionline(orbranch)thatfeedsfromthebusassociatedwithagiven IPR. TheIPRsareorganizedinapeer-to-peernetwork,oramesharchitecture,asshown in“gures3.2(a)and3.2(b).Inthisarchitecture,foragivenIPR,itisirrelevantwhether itsinputscomedirectlyfrompowerproducersorotherIPRs.Thekeytoourapproachis toprovidemultipleredundantpowerpathsbetweenproducers(generators)andconsumers (loads).

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26 Figure3.2:RelationbetweenEEDN,IPRslocationandIPRlogicalconnections.(Gen n:Generatorn,SrcPR:sourcePowerRouter,PPR:PrincipalPowerRouter,SnkPR:Sink PowerRouter) Inaddition,animportantissuetorealizeisthatthenetworkfortransmissionof electricalenergyisdierentfromthecommunicationnetworkbetweenIPRs.Thisscheme guaranteesindependencyofcommunicationinlightofacontingencyintheelectrictransmissionsystem.But,theIPRnetworkcommunicationmustemulatetheelectricalconnections inthesystem.Toaccomplishthis,eachIPRXestablishesaTCP/IPconnectionwitheach oftheIPRsYthatareattachedtolinesassociatedwithIPRX.Thisisshownin“gure 3.2(b).3.5.1ClassicationofIPRsWehavedevelopedthreetypesofIPRsasshownin“gure3.2(b): € SourcePowerRouter(SrcPR) :Theseroutersarelocatedatpowergenerators (producers),andtheyinformthesystemaboutthecapacityoftheirpowergenerators. Inaddition,eachonecommunicateswithitsneighborsaboutitscurrentstatusat

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27 particularmoment. € PrincipalPowerRouter(PPR) :theserouterswillre-con“gurethenetworkinthe eventofahigh-riskoperatingcondition,orsometypeofsystemfailure. € SinkPowerRouter(SnPR) :TheseroutersareconnectedbetweentheIPRsnetworkandtheloads.Theirprincipalfunctionistoconnectanddisconnectloadsfrom thesystemasrequired.3.6IPRsDecisionSchemeIPRsdecisionsfortheactivationofcontingencyplansarebasedontwofactors; next,wediscusseachone: € PriorityFactor :Everyoutputlinehasapriorityfactor,similartothepriorityvalues assignedtotheloads.Thesepriorityfactorsindicatewhicharethelinesthatmust beserviced“rst,intheeventofacontingency.AllIPRsmustrespondandguarantee satisfactiontotheirŽclientsŽattachedtowithhighestpriority.Thepriorityfactorof anoutputlineisde“nedintherangeofNaturalnumbersinwhichone1meansthe highestpriority,andlargerpriorityfactorvaluesindicatelesspriority.Forexample,a linewithpriorityfactor6islessimportantthanalinewithpriorityfactor2.Initially thepriorityfactorofeachlineissetbythesystemoperators.Inthefuture,wepropose toexplorealgorithmsthatassignprioritiesbasedonafunctionofthetypesofloads thatarefed(directlyorindirectly)byeachoutputline. € ReliabilityFactor :Everyinputlinehasareliabilityfactor,whichindicateshow reliableisthesourceofpowerfeedingtheline.NoticethatagiveninputlineS feedinganIPRXisseenasanoutputlinebyanotherIPRY.Hence,thereliability factorofaninputlineSisequaltothepriorityfactorassignedtothelinebytheIPR YthatseesthelineSasanoutputline.

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283.7IPRBasicNegotiationSchemeThemainoperationalbehaviorfortheIPRsisbasedontwoideas: € WhenanIPRreceivesapowerrequest,itveri“esthepriorityoftheŽclientŽoutput linethatmadetherequest.Iftheclienthasthehighestpriorityfactor,thentheIPR triestoresolvetherequest.Otherwise,theIPR:a)sendsastatusrequesttoallclient outputlineswithhigherpriorityfactor,b)waitsforstatusresponses,andc)theIPR triestoresolveallreceivedrequestbeginningwiththerequestwithhighestpriority. € Foreachrequest,theIPR“rstsendsarequestformorepowertothemorereliable inputlineavailable.IftheresponseobtainedisaDenyResponsethentheIPRproceedstosendtherequesttotheinputlinewiththesecondhighestreliability.This processisrepeateduntilpowerisreceivedoralllineshavebeenexplored.3.7.1BasicsalgorithmsforIPRsNegotiationschemeTheoperationalbehaviorofIPRsdescribedabove,isimplementedusingthefollowingalgorithm,whichisdividedinthreeparts: 1.The“rstpartisapplicablefortheSinkPR: Ifrestorationprocessisneededthen Eachloadaffectedsendsa getmessagetoIPRwithmostreliableline Ifnotsatisfied,trynextlineuntil powerarrivesorrequestisdeniedbyall neighboringIPRs Endif

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29 2.ThesecondpartisapplicableforeachPPR: IfIPRreceivearequestmessagethen Checksourcemessagepriority Storethemessageinrequestqueue SendaStatusRequesttoallotherclients withhigherpriorityaskingfortheirstatus. WaittimeTtoacquireresponses. Foreachresponse Ifresponseisnotnormalstatus Storethemessageresponseinrequestqueue Endif Foreachmessageinrequestqueue MovetofirstInputLink RepeatuntilanOKresponseisobtainedora denymessageisobtainedfromallpowersuppliers AdjacentIPR CheckLinkcapacity Iflinkcapacitycansupportmorepowerflow SendgetmessagetoIPRwithmost reliablelinenotyetinspected Waitforresponse IfOKresponse SendOkresponsetoclient else MovetonextInputLink Endif

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30 IfIPRobtainsdenymessagefromallIPRs Senddenyresponsetoclient Endif else MovetoInputLink Endif Endrepeat Endif 3.ThethirdpartisapplicableforeachSourcePR: IfIPRreceivesagetmessagethen Ifthegeneratorcangeneratemorepower SendoneOKresponsetotheclient Else Sendadenymessagetoclient Endif Endif3.7.2ExampleofbasicIPRsNegotiationWeusethesystempresentedin“gure3.2(a)toshowhowtheIPRsnetwork interactstoperformthesystemrestorationprocess.Forthissystem,weproposetoputan IPRineachbusofthesystem.Innormalstate,theIPRsinterchangeinformationabout theirstatusandtheirlinestatus. InourapproacheachbushasPrincipalPowerRouter(PPR),eachLoadhasa SinkPowerRouterandeachGeneratorhasaSourcePowerRouter(SrcPR)(“gure3.3(b)). Whenafaultoccurs,inthiscaseLoad1isun-servedbecauseLine1hasafailure(“gure

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31 Figure3.3:Load1isun-servedbecauseLine1hasafailure 3.3(a)),therestorationprocessisperformedasfollow: 1.TheaectedSinkPowerRouterbeginstherestorationprocess(SnkPR1).ThisSink IPRsendsarequestmessagetoitsmostreliablesupplierinthiscasePPR3(“gure 3.4(a-1)). 2.ThePPR3sendsarequestmessagetoitsmostreliablesupplier,PPR1(“gure3.4(a-2)) 3.PPR1cannotservicetherequest,soitsendsaDenyMessagetoPPR3(“gure3.4(a3)). 4.ThePPR3receivesthedenymessageanditproceedstosendarequestmessageto thesecondmostreliablesupplier,inthiscasePPR2(“gure3.4(a-4)). 5.ThePPR2receivestherequestmessage,itsendsaRequestMessagetoitsmost reliablesupplierSRCPR2(“gure3.4(a-5)).

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32 6.SRCPR2answerswithanarmativeresponsethatisroutedtoallinvolvedIPRSuntil reachestheSinkIPRthatbegantherestorationprocess(“gure3.4(a-6)(a-7)(a-8)). 7.Finally,thesystemgoesbackintoanoperationalstatewithitsallLoadsservedas “gure3.4(b)shows. Figure3.4:ExampleofIPRsNegotiationProcess.3.7.3ImprovementtoBasicNegotiationSchemeTheprincipaladvantageofIPRsBasicnegotiationschemeisthatitissimple,thus easytoimplement.UsingthisschemetheIPRsobtainquicklyresponsetotheirrequests. But,inthisscheme,theIPRsonlycananswerwithanOKresponseifoneofits InputLinescanservetheentirerequest,otherwise,theIPRsendsaDenyResponseforthis request.Forexample,inthesystemshownin“gure3.5a)theLoad1isun-servedaftera

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33 blackout.TheIPRsperformtherestorationprocessasfollows: 1.TheSnkPR1with100MWsendsarequestforservicetoPPR1(“gure3.5(b-1)). 2.PPR1hastwoinputlineswith50MWofcapacity.PPR1answerswithaDeny responsebecausenonelinescansupportthe100MW(“gure3.5(b-1). 3.Finally,theLoad1stillun-servedafterIPRsnegotiationprocessasshown“gure3.5 (c). But,thesystemcanserveLoad1iftherequestissplitintotworequestof50MW.Toavoid thisproblem,wemadeamodi“cationintheIPRsNegotiationschemethatwediscuss bellow. Figure3.5:DisadvantageofIPRsBasicnegotiationscheme 3.7.3.1ModicationstoImprovetheIPRsNegotiation Wemodi“edtheBasicNegotiationschemeoftheIPRstosolvethisproblemand improvethenegotiationresults.Thisimprovementconsistsintwomodi“cations:

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34 € WhenanIPRreceivesaDenyresponsefromallInputLines,itproceedstosend requestthroughitsoutputlinesthatdonothaveassigned”ow.Andtheseoutput linesbecomeintoInputlines. € WhenagivenIPRreceiveDenyResponsefromallInputLines,itsplittherequest intomanyrequestsasnecessaryanditsendstheserequeststhroughtheInputLines. 3.7.3.2ExampleofthenewNegotiationscheme Usingthesystemdepictedin“gure3.6weexplainthenewnegotiationscheme. Inthiscase,Load1isun-servedafterablackout.Therestorationprocessisperformedas follows: 1.SnkPR1sendsarequestsmessagetoPPR1(“gure3.6(b-1)),PPR1checksitsinput lines,butnoneoftheinputlinecanholdtherequest. 2.PPR1checkstheoutputlineslookingforanyoutputthatcanholdtherequest.But, itdoesnot“ndanyline. 3.Therequestissplitintotworequestof50MWandtheyaresendthroughLine1and Line2(“gure3.6(b-2)). 4.SrcPR1andSrcPR2allocateresourcesandresponsetoPPR1(“gure3.6(b-3)). 5.PPR1getstheresponsesandsendsaOKmessagetoLoad1(“gure3.6(b-4)). 6.Finally,Load1isrestoredasshownin“gure3.6(c).3.7.4DisadvantagesofmodicationofIPRsWiththismodi“cationstheIPRshavemorepossiblepathstosupplypowertothe loads,butwiththisnewuniverseofpossibilitiesthenumberofmessagestravellingacross thenetworkincreasestoo.Thisnewscenario,withsomanymessages,generatescongestions

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35 Figure3.6:ExampleoftheIPRsNegotiationschememodi“ed onthenetwork.Toavoidthisproblem,wepresentinthenextchapteramulti-stagescheme forcontrollingthenumberofmessageinthenetwork.

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CHAPTER4Multi-stageIPRNegotiation scheme4.1OverviewInthischapterweintroducetheIsland-zoneapproachforcontrollingthenumber ofmessagetravellingonthenetwork.Inthisapproachthesystemisdividedinseveral zones.Eachzoneisasub-systemwithgenerators,busesandloadsthatneedberestored. Likewise,wepresenttheprotocolsandalgorithmstoperformthenegotiationprocessintwo phases.TheFirstphaseisforrestoringtheloadswithgenerationcapacityavailableinthe samezone,andthesecondphaseisforrestoringloadsusingthecapacityintheneighboring zones.4.2Island-zoneapproachThekeytoimprovetheperformanceandqualityoftheIPRsdecisionmaking residesintheirknowledgeofthestateoftheirneighbors.Hence,theymustexchangestate 36

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37 messagescontinuously.But,astheIPRsNetworkgrowsthenumberofmessageswillgrow too,generatingcongestioninthecommunicationsnetworkaswefoundinsomeexperiments usingIPRsmodi“edscheme.Toavoidthis,wedividethesysteminzonesorgeographical regions.Eachzonehasabalancebetweengenerationanddemand.Then,eachzonebehaves asanautonomousnetworkofIPRs,capableofexchangingmessageswithotherzones.4.2.1TypesofIPRsTosupportthisZoneapproachweneedanadditionalIPRclassi“cationscheme. InteriorIPRsarethosethatexchangemessageswithinazone.BorderIPRsexchange messagesbetweenzones.Figure4.1showsanexampleofaPowerSystemdividedintwo zones(AandB).ZoneAhassevenbusesandoneachbushasanIPR.ZoneAhassix interiorIPRsandoneBorderIPR.Likewise,ZoneBhas11buseswithnineInteriorIPRs andtwoborderIPRs. Figure4.1:ExampleofIsland-zoneapproach

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38 € InteriorsIPRs. TheyexchangeIntra-zonemessages.Theirmainfunctionisto establishasecureoperationalstatewithintheinteriorofeachZone.Forthis,each SrcPRinformsthestateofitsgeneratorinamessagethatisspreadtotheinteriorof thezone.Inthisway,eachIPRknowsthestateofgeneratorsinitsarea,allowingit tomodifyitsreliabilitytabletorequestpowerfromgeneratorswithmoreprobability ofrespondingitsrequest.Thisschemeavoidsthewasteoftimeinaskingforpower fromgeneratorsthatcannotsatisfythem. € BorderIPRs. Theyexchangestatemessagesbetweendierentzonestomaintainthe well-beingofthegeneralstateofthesystem.WheninazoneX,thereisademandthat cannotbeservedbyitsgenerators,theborderIPRsrequestpowertotheirneighboring zonesinaneorttoguaranteethattheentiretyoftheloadsinzoneXareserved.In theeventofacatastrophiceventthatforcestothedivisionofthesystemsinislands, theborderIPRsexchangemessagestocoordinatetheinterconnectionprocessamong thoseislands.4.2.2ZonesasPowerNetworkEquivalentsInElectricalPowerSystemaNetworkEquivalentisaformforrepresentingaregion ofthepowersystemasaGeneratororaloaddependingonthepowerbalanceinthisregion. Foragivenpowersystemregion,iftheGenerationcapacityexceedsthedemandthenthis regionwillberepresentedasaGenerator;otherwise,thesectionwillberepresentedasa Load. Tosimplifythenegotiationschema,BorderIPRsseeeachneighboringzoneasa GeneratororLoad(NetworkEquivalent)dependingonthepower”owdirection.Figure 4.2illustratesthisidea;itshowstheviewofZoneAforBorderIPRsofZoneBastwo GeneratorsandtwoLoads.TheseGeneratorsaretheleastreliablegeneratorsforZoneB.

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39 Figure4.2:NetworkequivalentofzoneAforzoneB4.14.3NegotiationintwophasesClearly,itisalmostimpossibletoobtainoptimalanswersstartingfromlocaldecisions.Andalthoughthatitisnotourobjective,theIPRtheywillhavethecapacityto improvethestatusofthesystembymeansofanegotiationinseveralstageslookingto restoremoreandmoreloadsastimeprogresses.Inthissectionwepresentadescriptionof eachnegotiationstage.InAppendixAwepresentthecomplexalgorithmstoimplement thismulti-stagenegotiationscheme.4.3.1Intra-ZoneNegotiationphaseThe“rstphaseofIPRnegotiationisperformedattheintra-zonelevel.Atthis stage,theInteriorIPRsworktosatisfythemaximnumberofhigh-priorityloadstothe interiorofitszone.Bymeansofaperiodicexchangeofmessages,theinteriorIPRsareable

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40 todeterminewhichloadsshouldbeservedwiththegenerationcapacityineachzone,to makesurethatthesystemoperatesinasecureway.Theprocessofintra-zonenegotiation iscarriedoutinthreestages,discussedbelow: 4.3.1.1FriendlyRequeststage. Thisisthe“rststageoftheIPRsNegotiationprocesstoperformthesystem restoration.Thegoalofthisstageisreturnthesystemtoitspreviousoperationalstate, maintainingthepower”owasitwasbeforetheblackout.Inthisstageofthenegotiation theIPRsfollowthenormaloutlineofnegotiationdescribedinsection3.6.Inthisscheme, eachloadusesitsSnkPRtoposerequestsforpowertotheIPRnetwork.Thisrequestis routeduntilanarmativeanswerornegativeanswerisfound,whichdependoncurrent systemconditions.Followingtheprioritiesscheme,IPRschoosewhichloadscanbeserved andwhichcannot.InthisphasetheIPRstrytoreturnthesystemtoitspreviousoperationalstate,maintainingtherequestitthesamedirectionaspower”owswerebeforethe contingency. But,ifahighpriorityloadsendsalaterequestandtheresourcesofthesystemare alreadyassignedandtheydonotallowservingthisload,thisloadwillreceiveanegative answer.Thus,inthisphaseloadsofhigh-prioritymightbeunserved.SinceIPRsonly requestenergybasedonthe”owofthepreviousstage,thenalternative”owscannotbe explored.Asaresultothersolutionthatmightenableahigh-priorityloadtoberestored arenotconsidered. ExampleofFriendlyStage. Inthisexamplethesystemhasthreegenerators,threeloadsandninebuses.In thiscase,thepower”owsinsteadystateislike“gure4.3.Afterasystemblackoutcaused byfailuresinthelines2-8and4-1,theIPRsbegintherestorationprocess.The“rst

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41 NegotiationstageistheFriendlyStagewiththeobjectiveofreturningthesystemtoits previousstatus.TheFriendlyRequeststageisperformedasfollows: Figure4.3:ExampleofFriendlystage.Power”owsinsteadystate 1.Loads1,2and3sendRequestMessagesusingitsrespectiveSinkPowerRouters (“gure4.4(1)). 2.Themessageareroutedacrossthenetworkusingtheschemedescribedaboveusing priorityandreliabilityfactors(“gure4.4(2)). 3.PPR7and5receiveanArmativeResponseandtheseresponsesareroutedtoSnkPr 2and3(“gure4.4(3)). 4.PPR9receivesaDenymessagefromitsInputLines(“gure4.4(4)),anditroutes thisresponsetoSnkPr1(“gure4.4(5)).NoticethattherequestsentbyLoad1only reachIPR4andIPR8becausethelines4-5and8-7areoutputsofIPR4and8,since inthefriendlystagetherequestsaretransmittedonlyacrossinputlines. 5.Asresultofthisstageload2and3arerestored,butload1remainsdisconnected.

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42 Figure4.4:ExampleofFriendlystage.Restorationprocess 4.3.1.2PersistentRequeststage. ThisisthesecondstageperformedbytheIPRstorestorethesystem,anditis performedafterFriendlystageifoneorasetofloadsremainun-served.Theobjectiveof thisstageisrestoretheloadsthatcouldnotberestoredduringtheFriendlyStage.The SnkPRsthatreceiveanegativeanswerintheFriendlyRequeststagenowsendaPersistent ServiceRequest.ThisrequesttypeforcestheIPRstoattemptasystemrecon“gurationby changingthedirectionofthepower”owsnecessarytosatisfythemosthigh-priorityloads. Inthisstage,ifitisnecessarytheIPRsusethesplitrequestschemedescribedinsection 3.6.3.1. ExampleofPersistentStage. ThesystemforthisexampleisthesameusedintheexampleofFriendlyStage withthreegenerators,threeloadsandninebuses.Inthiscase,thepower”owsinsteady

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43 stateisasshown“gure4.3.Afterasystemblackoutcausedbyfailuresinthelines2-8and 4-1,theIPRsbeginrestorationprocess.The“rstNegotiationstageistheFriendlyStage withtheobjectiveofreturningthesystemtoitspreviousstatus.AfterFriendlyStagethe Load1remainsdisconnected,thentheIPRsbeginthePersistentstagetosupplytheload 1.ThePersistentstageisperformedasfollow: 1.Load1sendsaPersistentRequestusingitsrespectiveSinkPowerRouters(“gure4.5 (1)). 2.ThemessageisroutedacrossthenetworkusingthePersistentstagescheme(“gure 4.5(2)).NoticethattherequestcanbesentbyPPR4throughtheline4-5because inthisstagetherequestsaretransmittedacrosstheoutputlinesthatdonothave powerallocated. 3.The“nalresponseisroutedfromSrcPR3toSnkPr1acrossthenetwork(“gure4.5 (3)). 4.Asresultofthisstageload1isrestoredlikeload2and3. 4.3.1.3Loadsheddingcommunicationscheme. Thisisthelaststageofintra-zonenegotiationphase.InthisstagestheIPRs determineiftheyneedtodisconnectasetoflow-priorityloadstoguaranteeserviceto high-priorityloads. WhenagivenIPRdeterminesthatitneedstodisconnectasetoflowpriority loadstoguaranteeservicetoahighpriorityload,itsendsaspecialdisconnectmessageto theselectedlow-priorityloads.Toaccomplishthis,everyrequestmessageissignedwith acompleteroutetotheload.TheIPR,wichcanbetheSourceorthePrincipalPower Router,sendsaDisconnectMessagefollowingthepathstoredinthemessagetoreachthe SnkPRsservicingthelow-priorityloads.TheIPRthenwaitsforaDisconnectCon“rmation

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44 Figure4.5:ExampleofPersistentstage.Restorationprocess Message.ThislatterisroutedbytheIPRsinthepathbetweentheIPRandtheSnkPRs. WhentheSnkPRgetsaDisconnectmessage,itdisconnectsitsloadandsendsadisconnect con“rmationmessagetoIPRthatsenttheDisconnectmessage.Then,theSnkPRstarts lookingforpowerfromalternativegenerators.WhentheSrcPRreceivesthedisconnect messagefromalldisconnectedloads,itsendanarmativeresponsetothehighpriority loadthatmadethepowerrequest. ExampleofPersistentStage. ThesystemforthisexampleissimilartothesystemusedintheexampleofFriendly Stagewiththreegenerators,threeloadsandninebuses.ButinthiscasetheGenerator3 onlycanserve270MW.Thepower”owsinsteadystateisasshownin“gure4.3.After asystemblackoutcausedbyfailuresinthelines2-8and4-1,theIPRsbeginrestoration process.The“rstNegotiationstageistheFriendlyStagewiththeobjectiveofreturnthe systemtoitspreviousstatus.Inthiscase,theLoad1withpriority2arenotservedwhile

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45 Load3withpriority3hasbeenserved.ThentheIPRsbeginthepersistentnegotiation stagewithloadshedding.ThePersistentwithloadsheddingstageisperformedasfollow: 1.Load1sendsaPersistentRequestusingitsrespectiveSinkPowerRouters(“gure4.6 (1)). 2.ThemessageisroutedacrossthenetworkusingthePersistentstagescheme(“gure 4.6(2)).NoticethattherequestissentbyPPR4throughtheline4-5becausein thisstagetherequestsaretransmittedacrosstheoutputlinesthatdonothavepower allocated.AndSrcPR3receivestherequestandnoticesthatitdoesnothaveenough capacitytosupplyallloads.ThisSrcPRnoticesthatthenewrequestisfroma2nd priorityloadanditisservinga3thpriorityload,soitdecidestodisconnectthelowest priorityload. 3.SrcPR3sendsaDisconnectmessagetoSnkPrconnectedtoLoad3(“gure4.7(3)). ThismessageisrouteduntilitreachesSnkPR3(“gure4.7(4)). 4.SnkPR3disconnectsLoad3andsendsaDisconnectcon“rmationtoSrcPR3(“gure 4.7(5)).ThismessageisrouteduntilitreachesSrcPR3(“gure4.6(6)). 5.SrcPR3sendstheArmativeResponsetoSnkPR1andthismessageisroutedacross thenetworkuntilitreachesSnkPR1(“gure4.8(7)). 6.Finally,Load1withpriority2isservedlikeLoad2withpriority1,whileLoad3is disconnected.

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46 Figure4.6:ExampleofLoadShedding.Restorationprocess-sectiona Figure4.7:ExampleofLoadShedding.Restorationprocess-sectionb

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47 Figure4.8:ExampleofLoadShedding.Restorationprocess-sectionc4.3.2Inter-zoneNegotiationphaseTheobjectiveofthisphaseistogetpowerfromanotherzonetotrytorestorethe loadsthatwerenotservedintheIntra-Zonenegotiationprocess.WhenaSnkPRreceivesa deniedresponseforaPersistentRequestMessage,itsendsaInter-zoneAssistanceRequest, andthismessageisrouteduntilitgetsaBorderIPR.ThisBorderIPRsendsthisrequestto itspeerBorderIPRinanotherzone.Then,ifaBorderIPRreceivesanInter-ZoneRequest, itstoresthismessageanditsendsaFriendlyRequestMessagetotheIPRsinitszone network.NoticethatthismessageistreatedasanIntra-Zonemessageanditisprocessed asmentionedintheprevioussection. WhentheBorderIPRreceivesthe“nalresponse,itissenttotheborderIPRinthe zonewhichinitiatedthenegotiationprocess.Ifthismessageisanarmativeresponse,itis senttotheSnkPRthatmadetheoriginalrequest.Otherwise,theoriginalpowerRequestis

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48 routedtoanotherBorderIPRuntilanarmativeresponseisobtained,oraDenyresponse isobtainedfromallBorderIPRs.Inthislattercase,a“nalDenyResponseissenttothe SnkPRthatmadetheoriginalrequest.ThisSnkawaitsatimeintervalT,andthenbegins thewholeprocessagain. ExampleofInter-zonenegotiationPhase Thesystemusedinthisexampleisdividedintwozones,eachonehasthree generators,threeloadsandninebusesasshownin“gure4.9. Figure4.9:ExampleofInter-zoneNegotiation.Systemconditions Afterasystemblackoutcausedbyfailuresinthelines2-8and4-1inZoneA,the IPRsbegintherestorationprocess.The“rstNegotiationphaseisperformedatIntra-zone level.AsresultofIntra-zoneNegotiationineachzone,allloadsofZoneBarerestored whileLoad1and2ofZoneAarerestoredbutLoad3isdisconnected.Thesystemusesthe Inter-zonenegotiationtorestoredload3ofzoneA.Thisprocessisperformedasfollow:

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49 1.Load3ofzoneAisun-servedafteranintra-zonenegotiation,itsendsarequestfor inter-zoneassistance(“gure4.10(1)). 2.ThisrequestisroutedtotheZoneBusingBorder-IPR5inZoneA(“gure4.10(2)). 3.Border-IPR9ofZoneB,catchestherequestandbeginsanintra-zonenegotiationto satisfytherequest(“gure4.10(3)). 4.The“nalanswerisroutedtoLoad3ofZoneA(“gure4.10(4)and(5)). 5.FinallyallloadsofzoneAandBarerestoredaftertheInter-zonenegotiationphase. Figure4.10:ExampleofInter-zoneNegotiation.Negotiationprocess

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504.4IPRsMessagestypesSomemessagetypeswerede“nedforIPRscommunicationsandinteractions.These messagetypespermitadistributedcontrolandcoordinationoftheIPRsNetwork.Their missionistomaintaineachIPRawareoftheconditionsinitsneighboringIPRs.These messagetypesareorganizedintwogroups:4.4.1NormalstatemessagesThesemessagetypesaredesignedtoexchangeinformationbetweenadjacentIPRs whiletheEEDNisinnormalstateoperation(steadystate): € Connectionmessage:theycontaininformationabouteachlinkconnectedtooneIPR. ThesemessagesallowtheIPRstoestablishcommunicationchannelswithothersIPRs. € StatusRequest:thesemessagesaresentbyagivenIPRtoaskanotherIPRforits status. € StatusResponse:thismessagetypecorrespondstoamessagesentbyanIPRwhen itreceivesaStatusRequest,anditcontainsinformationaboutoperationalvariables ofthegivenIPR.4.4.2ContingencymessagesWhenaSystemfailureoccursintheEEDN,thesemessagetypeswillbeexchanged betweenIPRsduringthesystemrestorationprocess. 4.4.2.1Intra-zonemessages ThesemessagetypesaredesignedtoexchangeinformationbetweenIPRstoperformthesystemrestorationinIntra-zonelevel.

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51 € Friendlystagemessages: Aswepresentedinsection4.3.1the“rststepofIPRs negotiationoccursinthefriendlystage.Thesemessagesaredesignedtoperformthe “rstnegotiationstage. Getmessage:Theyaresentbyloadstorequestmorepower. Putresponse:arepositiveresponsesofanIPRtoapowerrequestreceivedfrom aparticularoutputline. Denyresponse:arenegativeresponsesgivenbyanIPRwhenitreceivesarequest thatitcannotsatisfy. € Persistentandloadsheddingmessages: thesecondstepofIPRsnegotiation occursinPersistentandloadsheddingstage.Thesemessagesaredesignedtoperform thesecondnegotiationstage. PersistentRequestmessage:Theyaresentbyloadstorequestmorepower. ThesemessagesallowIPRstochangeoutputlinestoinputlines. Disconnectmessage:ThesemessagesaresentbyPrincipalPowerRoutersor SourceGeneratorstolower-priorityloadswhentheyreceiveahigh-priorityrequestandloadsheddingisnecessarytosatisfythatrequest. Disconnectcon“rmationmessage:Theloadsthatreceivethedisconnectmessage sendsathesemessagetypetode-allocatetheresourcesassociatedtothem. MandatoryGetmessage:ThesemessagesaresentbySinkPowerRouterswhen theloadcannotservedinthefriendlystage.ThesemessagesallowIPRsto disconnectlow-priorityloadsifitisnecessarytosupplyahigh-priorityrequest. MandatoryChangemessage:ThesemessagesaresentbyPrincipalPowerRouters tode-allocateresourcesoflow-priorityloadsandallocatethemtosupplyahighpriorityrequest. Mandatorycon“rmationmessage:WhenaPrincipalPowerRouterschangesresourcesoflow-priorityrequesttoahigh-priorityrequest,itsendsthismessage tothePrincipalPowerRouterthatsenttheMandatoryChangeMessage.

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52 4.4.2.2Inter-zonemessages ThesemessagetypesaredesignedtoexchangeinformationbetweenIPRstoperformthesystemrestorationinInter-zonelevelwheninIntra-zoneleveltheIPRscannot restoreeveryload. € Inter-zoneRequest:Thesemessagesaresentbyloadswhentheyarenotservedduring Intra-zonenegotiationlevel.Thesemessagesareroutedacrosszonesuntiltheyreach aborderPowerRouter. € Inter-zoneGetmessage:ThesemessagearesentbyaBorderPowerRoutertoit neighborzone.WhenaBorderPowerRouterreceivesthistypeofmessagebeginsan Intra-zonenegotiationtosupplytherequest. € Inter-zonePutMessage:arepositiveresponsesforanInter-zoneGetMessage. € Inter-zoneDenyMessage:arenegativeresponsesforanInter-zoneGetMessage.

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CHAPTER5ExperimentalResults5.1IntroductionTovalidateourideas,wehaveimplementedasoftwarelibrarywithalltheprotocols andcommunicationsforIPRsoperationsandthealgorithmpresentedinchapters3and4. Wethenconstructedacomputersimulation,toexperimentwiththeconceptsassociated withtheIPRs. Theobjectiveofoursimulationsconsistsinobtainingareservationandallocation ofpowerresourcestoenableasystemrestorationusingnewIPRsapproachafteratotal systemblackout.Thus,theIPRswillnegotiateto“ndoutaneective(butperhapssuboptimal)allocationofpowertoeachlineandloads.Theimportantissuehereisdemonstrate thecapacityofIPRstosolvetherestorationproblemusingadecentralizedframework. Inordertodemonstratetheeectivenessoftheproposedapproachmanytestcases wereused,allusingthestandardtest-bedsystemsofnineand179-busmodeloftheWestern SystemsCoordinatingCouncil-WSCC1.Wepresentseveralofthesesimulationcases,these 1WesternSystemsCoordinatingCouncil(WSCC)wasformedwiththesigningoftheWSCCAgreement53

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scenariosareorganizedintwogroups,Intra-zonescenariosandInter-zonescenarios.The “rstgroupisfordemonstrationoftheeectivenessofIntra-zonenegotiationscheme;andthe secondgroupisfordemonstrationoftheeectivenessofthemulti-stagenegotiationscheme. Noticethatwerunseveralsimulationsforeachscenarios,becausetheorderinwhichthe messagesaresentandroutedbyIPRsvariesthroughthetimeproducingdierentallocations oftheresources. ThesoftwarelibrarywasbuiltusingtheJavaprogramminglanguage,anditwas runonseveralcomputersinterconnectedviaa100MbpsLAN.Intheearlystageofthis research,weusedonecomputerforeachIPR,butwhenweusedWSCC-179busmodel,we ranthesimulationusingacomputerforeachzone.Eachofthesecomputershasaprocessor PentiumIVof2.4GHzand512MBor1GBinRAM. Finally,tosimplifythe“gurespresentedinthischapter,thePrincipalPowerRouter (PPR)hastheIdofitsBus(e.g.ForBus1itsPPRisPPR1).SinkPowerRouter(SnkPR) hastheIdofitsLoad(e.g.forLoad1itsSnkPRisSnkPR1).And,eachSourcePower Router(ScrPR)hastheIdofitsGenerator(e.g.forGenerator1itsSrcPRisSrcRPR1).5.1.1PrototypeoverviewWedevelopedaprototypethatimplementstheIPRsconceptdescribedinthis thesis.Thisprototypeisdividedintothreeindependentsoftwareapplications,butallapplicationshavesimilarstructureandcommunicationscheme.Theirdierencesareassociated withtheirfunctionalroles: € SourcePowerRouters: thisapplicationimplementstheconceptsassociatedwith SourcesPowerRouters. onAugust14,1967by40electricpowersystems.Those"chartermembers"representedtheelectricpower systemsengagedinbulkpowergenerationand/ortransmissionservingallorpartofthe14WesternStates andBritishColumbia,Canada.[19]54

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€ SinkPowerRouters: thisapplicationimplementstheconceptassociatedwithSink PowerRouters. € PrincipalPowerRouters: thisapplicationimplementstheconceptassociatedwith SinkPowerRouters. 5.1.1.1Prototypestructure Aswepresentedabove,allapplicationshavesimilarmulti-layerstructureasshown in“gure5.1.Eachonewithfunctionalrolesclearlyde“nedasdescribedbellow: Figure5.1:PrototypeStructure € Communicationlayer. WiththislayertheIPRsestablishedthecommunication withothersforexchangingmessages.ThislayerusesTCPandUDPsocketstointerchangemessages. € Interpreterlayer. ThemessagesinterchangedbyIPRsarebuiltusingXML.The interpreterlayerreceivesandsendsXMLmessagesfrom/totheCommunicationlayer. Theinterpreterlayerparsesthesemessagetodeterminetype,parametersandsource, andsendthisinformationtoDecisionlayer. € Decisionlayer. TheDecisionlayeristhebrainofIPRs,itmakedecisionsabout routingpaths,andnegotiationschemes. 55

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5.2Intra-zonescenariosInordertodemonstratetheeectivenessoftheIntra-zonenegotiationalgorithms, wepresentseveralscenarioswherethenegotiationforthesystemrestorationoccursatthe Intra-zonelevel.Firstwehavefourmodi“cationsoftheWSCCnine-bussystem,and“nally wehavetheWSCC179-bussystemdividedin“veautonomouszones.Thesezonehavethe characteristicofbalancebetweengenerationcapacityandloaddemandwithinthezone.5.2.1WSCCnine-bussystem-ScenarioIThegoalofthissimulationistoprovetheeectivenessofthebasicIPRsNegotiationscheme.Inthiscase,theIPRstrytoperformthesystemrestorationafterasystem blackout.Themodelusedconsistsofanetworkofthreegenerators,sixbusesandthree loadsasdepictedin“gure5.2.Aswementionedbefore,thisisamodi“cationoftheWSCC model.Inthisscenario,aftertheblackout,everycomponentareavailableforthesystem restoration. Table5.1showsthevaluesoftheprincipalvariablesofoursimulation.Each rowinthistablecorrespondstovariablesassociatedwitheachbusofthesystem.The columnŽBusŽcorrespondstotheIdenti“erofthebus;thecolumnŽLineŽcorrespondsto theidenti“erofeachlineconnectedtoeachbus;thecolumnŽLimitŽcorrespondstothe capacityofeachlineinthesystem;thecolumnŽReliabilityŽcorrespondstotheReliability factorassociatedwitheachlineinthesystemandthecolumnŽPriorityŽcorrespondstothe Priorityfactorassociatedwitheachlineinthesystem. 56

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Figure5.2:ScenarioI-WSCCNine-bussystemmodi“ed Bus Line Limit Reliability Priority B1 Gen1 90MW 1 / B1B2 90MVA / 2 B1B6 90MVA / 1 B2 B1B2 90MVA 2 / B2B3 125MVA 1 / Load1 125MW / 1 B3 Gen2 190MW 1 / B2B3 125MVA / 1 B3B4 125MVA / 2 B4 B3B4 125MVA 2 / B4B5 100MVA 1 / Load2 100MW / 3 B5 Gen3 100MW 1 / B4B5 100MVA / 1 B5B6 100MVA / 2 B6 B5B6 100MVA 2 / B1B6 90MVA 1 / Load3 90MW / 2 Table5.1:ScenarioI-Simulationconditions-WSCCnine-bussystem 57

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Resultsofsimulation Afterrunningthetestcasesindependenttimes,thepowerallocationnegotiatedby IPRscansupply100%ofthepowerrequiredbyloadsineachcase.Afteratotalblackout, allaectedSnkPRssendrequestmessagestotheirhighreliabilitysuppliers.Whenthey receivethemessagesrequest,theysendarequestmessagestotheirSrcPRs.TheSrcPRs verifythegeneratorsstatus,andreplytotherequest.TheSrcIPRsallocatethepowerof theirgeneratorsandsendaarmativeresponsetoIPRsthatmadetherequests.These responsesaresentacrossnetworkallocatingpowerateachlineforsystemrestoration. Theallocationofpowersatis“estheconstraintsestablishedinthemathematical formulation(section3.2).Moreover,thisallocationofpowerisdoneinadecentralized manner,usingonlylocalinformation.Table5.2presentstheallocationofpowerforeachof theelementsinthesystem.Inthistableeachrowcorrespondstothevariablesassociated witheachbusinthesystemanditsvalueafterrunningthesimulation.Thethree“rst columnscorrespondhasthesamemeanintable5.1andthecolumnŽOutputŽrepresents the”owmagnitudeassignedtoeachlineasSimulationresult.5.2.2WSCCnine-bussystem-ScenarioIITheobjectiveofthisscenarioistodemonstratethecapacityofSourcePower Routerstomakedecisionsforloadsheddingifitisneededtoguaranteetheserviceto high-priorityloads.Themodelusedconsistsofanetworkofthreegenerators,ninebuses andthreeloadsasdepictedin“gure5.3,this“gureshowstheLinescapacity,Generators capacityandLoadspriorityanddemand.Aswementionedbefore,thisisamodi“cation oftheWSCC-ninebusmodel.IntheScenarioIthesystemhasallresourceavailable.But, inthisScenariothesystemhasthelinesB8-B3andB1-B7outofservice.Thegeneration capacityavailableis270MWandthetotaldemandis315MW,thissituationmeansthat 58

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Bus Line Limit Output B1 Gen1 90MW 90MW B1B2 90MVA 0MW B1B6 90MVA 90MW B2 B1B2 90MVA 0MW B2B3 125MVA 125MW Load1 125MW 125MW B3 Gen2 190MW 125MW B2B3 125MVA 125MW B3B4 125MVA 0MW B4 B3B4 125MVA 0MW B4B5 100MVA 100MW Load2 100MW 100MW B5 Gen3 100MW 100MW B4B5 100MVA 100MW B5B6 100MVA 0MW B6 B5B6 100MVA 0MW B1B6 90MVA 90MW Load3 90MW 90MW Table5.2:ScenarioI-Simulationresults-WSCCnine-bussystem someloadsmustremainun-servedafterthenegotiationprocess. Resultsofsimulation Afterrunningthetestcasestendierenttimes,inallcasesthepowerallocation negotiatedbyIPRscansupplyhigherpriorityloads(load1andload2).Thenegotiation processisperformedinthisway:Afterthefriendlystage,loads2and3areservedbutLoad 1isdisconnected.Because,Load3(priority3)haslowerprioritythanload1(priority2) thesystemusePersistentStagetoallocatepowerforload1;SinkPowerRouter(SnkPR1) sendsaPersistentGetMessage,thismessageisrouteduntilitreachesSourcePowerRouter (SrcPR3)connectedtoGenerator3.ThisSrcPR3makedecisiontodisconnectlowest priorityload(load3)becausethelimitofthegeneratoronlyletittosupplyload1ifit disconnectstheload3.ThedisconnectmessageissendtoSinkPowerRouter3(SnkPR3) andtheputmessageisroutedfromSrcPR3toSnkPR1tosupplyload1.Finally,loads1 59

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Figure5.3:ScenarioII-WSCCnine-bussystem and2withhigh-prioritiesareservedwhilethelowest-priorityload(load3)isdisconnected. Theallocationofpowersatis“estheconstraintsestablishedinthemathematical formulation(section3.2).Moreover,thisallocationofpowerisdoneinde-centralizedmanner,usingonlylocalinformation.Table5.3presentstheallocationofpowerforeachload inthesysteminfriendlyandpersistentstage.Table5.4presentspowerallocationineach generatorofthesystemafterfriendlyandpersistentstages.And,table5.5showsthevaluesoftheprincipalvariablesonbusesandlinesofoursimulationssuchascapacity(Limit column),Availability(statuscolumn),powerallocatedafterFriendlyStage(FriendlyStage column)andpowerallocatedafterPersistentstage(PersistentStagecolumn). Load Priority Value Initialstatus Friendlystage PersistentStage Load1 2 125 Un-served Un-served Served Load2 1 100 Un-served Served Served Load3 3 90 Un-served Served Un-served Table5.3:ScenarioII-Loadsstatus-WSCCnine-bussystem 60

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Generator Line Limit Status Friendlystage PersistentStage Gen1 B7-Gen1 250 Available 0 0 Gen2 B8-Gen2 300 Available 0 0 Gen3 B9-Gen3 270 Available 190 225 Table5.4:ScenarioII-Generatorsstatus-WSCCnine-bussystem 61

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Bus Line Limit Status FriendlyStage PersistentStage B1 B1-B7 250 un-Available 0 0 B1B2 250 Available 0 0 B1B6 250 Available 0 125 B2 B1B2 250 Available 0 0 B2B3 250 Available 0 125 B2-Load1 125 Available 0 125 B3 B3-B8 300 un-Available 0 0 B2B3 250 Available 0 0 B3B4 250 Available 0 0 B4 B3B4 250 Available 0 0 B4B5 150 Available 100 100 B4-Load2 100 Available 100 100 B5 B5-B9 400 Available 190 225 B4B5 150 Available 100 100 B5B6 250 Available 90 125 B6 B5B6 250 Available 90 125 B1B6 250 Available 0 125 B6-Load3 90 Available 90 0 B7 B1-B7 250 un-Available 0 0 B7-Gen1 250 Available 0 0 B8 B2-B8 300 un-Available 0 0 B8-Gen2 300 Available 0 0 B9 B5-B9 400 Available 190 225 B9-Gen3 270 Available 190 225 Table5.5:ScenarioII-Busandlinesstatus-WSCCnine-bussystem 62

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5.2.3WSCCnine-bussystem-ScenarioIIITheobjectiveofthisscenarioistodemonstratethecapacityofPrincipalPower Routerstomakedecisionsforloadsheddingifitisneededtoguaranteetheserviceto higher-priorityloads.Themodelusedconsistsofanetworkofthreegenerators,ninebuses andthreeloadsasdepictedin“gure5.4.Aswementionedbefore,thisisamodi“cation oftheWSCCmodel.InthisScenario,likeScenarioII,thesystemhasthelinesB8-B3 andB1-B7out-of-service.InscenarioIItheloadsheddingisperformedfromSourcePower Routersbecausethelimitationofthesystemisgivenbythegenerationcapacity.Inthis ScenariothelimitationisgivenbylineB5-B9thatdoesnotsupportallamountofpower ”owrequestedbytheloads. Figure5.4:ScenarioIII-WSCCnine-bussystem Resultsofsimulation 63

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Afterrunningthetestcasestendierenttimes,inallcasesthepowerallocation negotiatedbyIPRscansupplyhigherpriorityloads(load1andload2).Thenegotiation processisperformedinasfollow: Afterfriendlystageloads2and3areservedwhileload1isdisconnected.But,load 3(priority3)haslowerprioritythanload1(priority2).ThenthesystemusePersistent Stagetoallocatepowerforload1;SinkPowerRouter(SnkPR1)sendsaPersistentGet Message(PGM).PrincipalPowerRouter6(PPR6)getthemessageandmakedecisionto disconnectlowestpriorityload(load3)becausethelimitofitsinputlineonlyletsitto supplyload1ifitdisconnectstheload3.ThedisconnectmessageissendtoSinkPower Router3(SnkPR3)andPPR6makeaMandatoryChangeMessage(MCHM)toassign theresourceallocatedforload3toload1,andthisMCHMisrouteduntilitreachesSource PowerRouter(SrcPR3)connectedtoGenerator3.SrcPR3assigntheresourcesneededto supplyload1,andsendsthe“nalresponsetoPPR6.PPR6getstheresponseandsends aputmessagetoSnkPR1.Finally,loads1and2withhigh-prioritiesareservedwhilethe lowest-priorityload(load3)areun-served. Theallocationofpowersatis“estheconstraintsestablishedinthemathematical formulation(section3.2).Moreover,thisallocationofpowerisdoneinde-centralizedmanner,usingonlylocalinformation.Table5.6presentstheallocationofpowerforeachload inthesysteminfriendlyandpersistentstage.Table5.7presentspowerallocationineach generatorofthesystemafterfriendlyandpersistentstage.And,table5.8showsthevalues oftheprincipalvariablesonbusesandlinesofoursimulationssuchascapacity(Limit column),Availability(statuscolumn),powerallocatedafterFriendlyStage(FriendlyStage column)andpowerallocatedafterPersistentStage(PersistentStagecolumn). 64

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Load Priority Value Initialstatus Friendlystage PersistentStage Load1 2 125 Un-served Un-served Served Load2 1 100 Un-served Served Served Load3 3 90 Un-served Served Un-served Table5.6:ScenarioIII-Loadsstatus-WSCCnine-bussystem Generator Line Limit Status Friendlystage PersistentStage Gen1 B7-Gen1 250 Available 0 0 Gen2 B8-Gen2 300 Available 0 0 Gen3 B9-Gen3 270 Available 190 225 Table5.7:ScenarioIII-Generatorsstatus-WSCCnine-bussystem Bus Line Limit Status FriendlyStage PersistentStage B1 B1-B7 250 un-Available 0 0 B1B2 250 Available 0 0 B1B6 250 Available 0 125 B2 B1B2 250 Available 0 0 B2B3 250 Available 0 125 B2-Load1 125 Available 0 125 B3 B3-B8 300 un-Available 0 0 B2B3 250 Available 0 0 B3B4 250 Available 0 0 B4 B3B4 250 Available 0 0 B4B5 150 Available 100 100 B4-Load2 100 Available 100 100 B5 B5-B9 250 Available 190 225 B4B5 150 Available 100 100 B5B6 150 Available 90 125 B6 B5B6 150 Available 90 125 B1B6 250 Available 0 125 B6-Load3 90 Available 90 0 B7 B1-B7 250 un-Available 0 0 B7-Gen1 250 Available 0 0 B8 B2-B8 300 un-Available 0 0 B8-Gen2 300 Available 0 0 B9 B5-B9 250 Available 190 225 B9-Gen3 270 Available 190 225 Table5.8:ScenarioIII-Busandlinesstatus-WSCCnine-bussystem 65

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5.2.4WSCCnine-bussystem-ScenarioIVTheobjectiveofthisscenarioistodemonstratethecapacityofPrincipalPower Routerstomakesplitrequests(section3.6)andthecapacityofPrincipalRouterstomake decisionsforloadsheddingifitisneeded.Themodelusedconsistsofanetworkofthree generators,ninebusesandthreeloadsasdepictedin“gure5.5.InthisScenario,like ScenarioII,thesystemhasthelinesB8-B3andB1-B7out-of-service.Aswementioned before,thisisamodi“cationoftheWSCC-ninebusmodel. Figure5.5:ScenarioIV-WSCCnine-bussystem Resultsofsimulation Afterrunningthetestcasestendierenttimes,inallcasesthepowerallocation negotiatedbyIPRscansupplyhigherpriorityloads(load1andload2).Afterfriendly stageloads2and3areservedbutload3(priority3)islow-prioritythanload1(priority2). 66

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ThenthesystemusePersistentStagetoallocatepowerforload1;PrincipalPowerRouter inbus2(PPR2),withtheinformationobtainedfromFriendlystage,makesdecisionto sendsplitrequestacrosslinesB2-B1andB2-B3.Theserequestsarerouteduntiltheyreach PPR5,PPR5checkthecapacityofitsinputlineandmakesthedecisionofdisconnect load3(withlessprioritythanload1).Theresourcesareallocatedtosupplyload1and theresponseisroutedtoload1.Finally,loads1and2withhigh-prioritiesareservedwhile thelowest-priorityload(load3)isun-served. Theallocationofpowersatis“estheconstraintsestablishedinthemathematical formulation(section3.2).Moreover,thisallocationofpowerisdoneinde-centralizedmanner,usingonlylocalinformation.Table5.9presentstheallocationofpowerforeachload inthesysteminfriendlyandpersistentstage.Table5.10presentspowerallocationineach generatorofthesystemafterfriendlyandpersistentstage.And,table5.11showsthevaluesoftheprincipalvariablesonbusesandlinesofoursimulationssuchascapacity(Limit column),Availability(statuscolumn),powerallocatedafterFriendlyStage(FriendlyStage column)andpowerallocatedafterPersistentStage(PersistentStagecolumn). Load Priority Value Initialstatus Friendlystage PersistentStage Load1 2 110 Un-served Un-served Served Load2 1 100 Un-served Served Served Load3 3 90 Un-served Served Un-served Table5.9:ScenarioIV-Loadsstatus-WSCCnine-bussystem Generator Line Limit Status Friendlystage PersistentStage Gen1 B7-Gen1 250 Available 0 0 Gen2 B8-Gen2 300 Available 0 0 Gen3 B9-Gen3 270 Available 190 210 Table5.10:ScenarioIV-Generatorsstatus-WSCCnine-bussystem 67

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Bus Line Limit Status FriendlyStage PersistentStage B1 B1-B7 250 un-Available 0 0 B1B2 250 Available 0 0 B1B6 250 Available 0 110 B2 B1B2 250 Available 0 0 B2B3 250 Available 0 110 B2-Load1 110 Available 0 110 B3 B3-B8 300 un-Available 0 0 B2B3 250 Available 0 0 B3B4 250 Available 0 0 B4 B3B4 250 Available 0 0 B4B5 150 Available 100 100 B4-Load2 100 Available 100 100 B5 B5-B9 270 Available 190 210 B4B5 150 Available 100 100 B5B6 250 Available 90 110 B6 B5B6 250 Available 90 110 B1B6 250 Available 110 B6-Load3 90 Available 90 0 B7 B1-B7 250 un-Available 0 0 B7-Gen1 250 Available 0 0 B8 B2-B8 300 un-Available 0 0 B8-Gen2 300 Available 0 0 B9 B5-B9 270 Available 190 210 B9-Gen3 270 Available 190 210 Table5.11:ScenarioIV-Busandlinesstatus-WSCCnine-bussystem5.2.5WSCCnine-bussystem-ScenarioVTheobjectiveofthisscenarioistodemonstratethecapacityofPrincipalPower Routerstomakesplitrequestswithoutloadshedding.Themodelusedconsistsofanetwork ofthreegenerators,ninebusesandthreeloadsasdepictedin“gure5.6.Aswementioned before,thisisamodi“cationoftheWSCCmodel.InthisScenario,likeScenarioII,the systemhasthelinesB8-B3andB1-B7out-of-service.Table5.14showsthevaluesofthe principalvariablesonbusesandlinesofoursimulations. Resultsofsimulation 68

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Figure5.6:ScenarioV-WSCCnine-bussystem Afterrunningthetestcasestentimes,inallcasesthepowerallocationnegotiated byIPRscansupplyallloads(load1,load2andload3).Afterfriendlystageloads2and3 areservedbutload3(priority3)isless-prioritythanload1(priority2).Thenthesystem usePersistentStagetoallocatepowerforload1.PrincipalPowerRoutedinbus2(PPR 2),withtheinformationobtainedfromFriendlystage,makesdecisiontosendsplitrequest acrosslinesB2-B1andB2-B3.TheserequestsarerouteduntiltheyreachPPR5,PPR5 checksthecapacityofitsinputlineandroutestherequeststoSrcPR3.Theresourcesare allocatedtosupplyload1andtheresponseareroutedtoload1.Finally,loads1,2and3 areserved. Theallocationofpowersatis“estheconstraintsestablishedinthemathematical formulation(section3.2).Moreover,thisallocationofpowerisdoneinde-centralizedmanner,usingonlylocalinformation.Table5.12presentstheallocationofpowerforeachload inthesysteminfriendlyandpersistentstage.Table5.13presentspowerallocationineach 69

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generatorofthesystemafterfriendlyandpersistentstage.And,table5.14showsthevaluesoftheprincipalvariablesonbusesandlinesofoursimulationssuchascapacity(Limit column),Availability(statuscolumn),powerallocatedafterFriendlyStage(FriendlyStage column)andpowerallocatedafterPersistentStage(PersistentStagecolumn). Load Priority Value Initialstatus Friendlystage PersistentStage Load1 2 110 Un-served Un-served Served Load2 1 100 Un-served Served Served Load3 3 90 Un-served Served Served Table5.12:ScenarioV-Loadsstatus-WSCCnine-bussystem Generator Line Limit Status Friendlystage PersistentStage Gen1 B7-Gen1 250 Available 0 0 Gen2 B8-Gen2 300 Available 0 0 Gen3 B9-Gen3 300 Available 190 300 Table5.13:ScenarioV-Generatorsstatus-WSCCnine-bussystem 70

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Bus Line Limit Status FriendlyStage PersistentStage B1 B1-B7 250 un-Available 0 0 B1B2 250 Available 0 60 B1B6 250 Available 0 60 B2 B1B2 250 Available 0 60 B2B3 250 Available 0 50 B2-Load1 110 Available 0 110 B3 B3-B8 300 un-Available 0 0 B2B3 250 Available 0 50 B3B4 250 Available 0 50 B4 B3B4 150 Available 0 50 B4B5 150 Available 100 150 B4-Load2 100 Available 100 100 B5 B5-B9 300 Available 190 300 B4B5 150 Available 100 150 B5B6 150 Available 90 150 B6 B5B6 150 Available 90 150 B1B6 250 Available 0 60 B6-Load3 90 Available 90 90 B7 B1-B7 250 un-Available 0 0 B7-Gen1 250 Available 0 0 B8 B2-B8 300 un-Available 0 0 B8-Gen2 300 Available 0 0 B9 B5-B9 300 Available 190 300 B9-Gen3 300 Available 190 300 Table5.14:ScenarioV-Busandlinesstatus-WSCCnine-bussystem 71

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5.2.6WSCC179-busSystemThemodelusedconsistsofanetworkof29generators,179busesand113loads. Thesystemisdividedinto“vezones(1-A,1-B,1-B,2-Aand2-B)asdepictedin“gure 5.7.Intheoriginalmodelseveralloadsarenetworkequivalentswithanegativevalue,this meansthatinthesesectionthegenerationexceedsthedemand.Foroursimulationthese loadswithnegativeloadsaregenerators.Thenthenumberofgeneratorincreasewhilethe numberofloadsdecrease. Theobjectiveofthisscenarioistorestorethesystemafteratotalblackout.We workedwithlessPrincipalPowerRoutersthanbusesinthesystembecauseaPPRcould manageoneormorebuses.InthismodelthebusesPPRsarelocatedatthebusesthat haveatleastthreelines.Because,inbuseswithtwolinestheIPRdonotneedtochoice whichlinethewillserve. Figure5.8,5.9,5.10,5.11and5.12showtheschemesofZone1-A,1-B,1-C,2-A and2-Brespectively. Resultsofsimulation Afterrunningseparatelyseveralsimulationsforeachzone,weobtainthatinzones 1-A,1-B,1-Cand2AtheIPRnetworkcouldallocateresourceseverytimetosupplyall loads.ButinZone2-BtheIPRnetworkcouldallocateresourcesfor84%ofloadsinthe bestcaseand76%ofloadsintheworsecasebut everyhigh-priorityloads weresupplied inthiszone.Tables5.15to5.24showtheresultsofnegotiationineachzoneofWSCC 179-bussysteminoneofsimulationperformed.Thepowerallocatedineachgeneratoris notthesamealways,butinallsimulationsperformedthepowergeneratedmatchwiththe powerdemandbyloadsineachzone. 72

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Figure5.7:WSCC179-busmodel 73

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Figure5.8:WSCC179-busmodel-Zone1-A Figure5.9:WSCC179-busmodel-Zone1-B 74

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Figure5.10:WSCC179-busmodel-Zone1-C Figure5.11:WSCC179-busmodel-Zone2-A 75

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Figure5.12:WSCC179-busmodel-Zone2-B 76

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Theallocationofpowersatis“estheconstraintsestablishedinthemathematical formulation(section3.2).Moreover,thisallocationofpowerisdoneinde-centralizedmanner,usingonlylocalinformation. 77

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Resultsofsimulation-Zone1-A InthiszonetheIPRsnegotiationgetstosupplyallloadswiththeinternalgenerationcapacityineverysimulation.Theresourcesallocationchangeineachsimulation.Table 5.15presentsthePowerAllocationforeachgeneratorsinthiszone.ThecolumnŽGeneratorŽ correspondstothebuswherethegeneratorisconnected.ThecolumnŽLineŽcorresponds theIdenti“erofthelinebetweentheGeneratoranditsbus.ThecolumnŽLimitŽcorrespondstotheGeneratorCapacity,ColumnŽStatusŽcorrespondstoGeneratorAvailability andColumnŽFinalŽcorrespondstoPowerAllocationforeachgenerator. TheTable5.16presentsthestatusofeachLoadinthiszoneduringthenegotiation process.ThecolumnŽLoadŽcorrespondstothebuswheretheloadisconnected.ThecolumnŽPriorityŽcorrespondstotheLoadPriority.ThecolumnŽInitialStatusŽcorresponds theInitialstatusaftertheblackoutandColumnsŽFriendlystageŽandŽPersistentStageŽ correspondtotheLoadstatusaftereachnegotiationstagerespectively. Generator Line Limit Status Final Gen30 B30-Gen30 10000 Available 4500 Gen35 B35-Gen35 10000 Available 3700 Gen65 B65-Gen65 10000 Available 5232 Gen68 B68-Gen68 67.5 Available 0 Gen69 B69-Gen69 44.2 Available 0 Gen70 B70-Gen70 10000 Available 972 Gen73 B73-Gen73 1525 Available 0 Gen77 B77-Gen77 10000 Available 4877 Gen79 B79-Gen79 10000 Available 8600 Gen82 B82-Gen82 66.6 Available 0 Gen83 B83-Gen83 339 Available 0 TotalGenerated 27881 Table5.15:WSCC179-bussystem-Zone1-A-Generatorsstatus 78

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Load Priority Value Initialstatus Friendlystage PersistentStage 30 2 100 Un-served Served Served 31 3 4400 Un-served Served Served 34 2 3600 Un-served Served Served 35 3 100 Un-served Served Served 65 3 100 Un-served Served Served 66 3 1700 Un-served Served Served 67 3 160 Un-served Un-served Served 70 3 100 Un-served Served Served 71 3 3137 Un-served Un-served Served 75 3 2584 Un-served Un-served Served 76 3 3200 Un-served Served Served 77 3 100 Un-served Served Served 78 1 3500 Un-served Un-served Served 79 2 100 Un-served Served Served 80 2 5000 Un-served Served Served TotalLoads 27881 66.35% 100% Table5.16:WSCC179-bussystem-Zone1-A-Loadsstatus Resultsofsimulation-Zone1-B InthiszonetheIPRsnegotiationgetstosupplyforallloadswiththeinternal generationcapacityineverysimulation.Theresourcesallocationchangeineachsimulation. Table5.17presentsthePowerAllocationforeachgeneratorsinthiszone.Thecolumn ŽGeneratorŽcorrespondstothebuswherethegeneratorisconnected.ThecolumnŽLineŽ correspondstheIdenti“erofthelinebetweentheGeneratoranditsbus.Thecolumn ŽLimitŽcorrespondstotheGeneratorCapacity,ColumnŽStatusŽcorrespondstoGenerator AvailabilityandColumnŽFinalŽcorrespondstoPowerAllocationforeachgenerator. TheTable5.18presentsthestatusofeachLoadinthiszoneduringthenegotiation process.ThecolumnŽLoadŽcorrespondstothebuswheretheloadisconnected.ThecolumnŽPriorityŽcorrespondstotheLoadPriority.ThecolumnŽInitialStatusŽcorresponds theInitialstatusaftertheblackoutandColumnsŽFriendlystageŽandŽPersistentStageŽ correspondtotheLoadstatusaftereachnegotiationstagerespectively. 79

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Generator Line Limit Status Final Gen36 B36-Gen36 10000 Available 891.9 Gen45 B45-Gen45 10000 Available 2153 Gen159 B159-Gen159 10000 Available 1410.6 Gen160 B160-Gen160 62 Available Gen162 B162-Gen162 10000 Available 355 TotalGenerated 4810.5 Table5.17:WSCC179-bussystem-Zone1-B-Generatorsstatus Load Priority Value Initialstatus Friendlystage PersistentStage 36 2 100 un-served served served 44 1 2053 un-served served served 45 3 100 un-served served served 85 1 610 un-served served served 155 3 457.7 un-served served served 156 3 33.9 un-served served served 157 3 148 un-served served served 158 3 116.1 un-served served served 159 1 100 un-served served served 161 2 255 un-served served served 162 3 100 un-served served served 164 1 31.6 un-served served served 165 2 141.2 un-served served served 166 3 379 un-served served served 167 2 185 un-served served served TotalLoads 4810.5 100% 100% Table5.18:WSCC179-bussystem-Zone1-B-Loadsstatus Resultsofsimulation-Zone1-C InthiszonetheIPRsnegotiationgetstosupplyforallloadswiththeinternal generationcapacityineverysimulation.Theresourcesallocationchangeineachsimulation. Table5.19presentsthePowerAllocationforeachgeneratorsinthiszone.Thecolumn ŽGeneratorŽcorrespondstothebuswherethegeneratorisconnected.ThecolumnŽLineŽ correspondstheIdenti“erofthelinebetweentheGeneratoranditsbus.Thecolumn ŽLimitŽcorrespondstotheGeneratorCapacity,ColumnŽStatusŽcorrespondstoGenerator AvailabilityandColumnŽFinalŽcorrespondstoPowerAllocationforeachgenerator. 80

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TheTable5.20presentsthestatusofeachLoadinthiszoneduringthenegotiation process.ThecolumnÂŽLoadÂŽcorrespondstothebuswheretheloadisconnected.ThecolumnÂŽPriorityÂŽcorrespondstotheLoadPriority.ThecolumnÂŽInitialStatusÂŽcorresponds theInitialstatusaftertheblackoutandColumnsÂŽFriendlystageÂŽandÂŽPersistentStageÂŽ correspondtotheLoadstatusaftereachnegotiationstagerespectively. Generator Line Limit Status Final Gen9 B9-Gen9 10000 Available 2228.7 Gen4 B4-Gen4 10000 Available 100 Gen6 B6-Gen6 10000 Available 2060 Gen11 B11-Gen11 10000 Available 1330 Gen18 B18-Gen18 10000 Available 100 TotalGenerated 5818.7 Table5.19:WSCC179-bussystem-Zone1-C-Generatorsstatus Load Priority Value Initialstatus Friendlystage PersistentStage 2 3 1750 un-served served served 4 3 100 un-served served served 5 3 2350 un-served served served 6 2 100 un-served served served 8 2 239 un-served served served 9 3 100 un-served served served 10 2 139.7 un-served served served 11 1 100 un-served served served 17 3 840 un-served served served 18 2 100 un-served served served TotalLoads 5818.7 100% 100% Table5.20:WSCC179-bussystem-Zone1-C-Loadsstatus 81

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Resultsofsimulation-Zone2-A InthiszonetheIPRsnegotiationgetstosupplyforallloadswiththeinternal generationcapacityineverysimulation.Theresourcesallocationchangeineachsimulation. Table5.21presentsthePowerAllocationforeachgeneratorsinthiszone.Thecolumn ŽGeneratorŽcorrespondstothebuswherethegeneratorisconnected.ThecolumnŽLineŽ correspondstheIdenti“erofthelinebetweentheGeneratoranditsbus.Thecolumn ŽLimitŽcorrespondstotheGeneratorCapacity,ColumnŽStatusŽcorrespondstoGenerator AvailabilityandColumnŽFinalŽcorrespondstoPowerAllocationforeachgenerator. TheTable5.22presentsthestatusofeachLoadinthiszoneduringthenegotiation process.ThecolumnŽLoadŽcorrespondstothebuswheretheloadisconnected.ThecolumnŽPriorityŽcorrespondstotheLoadPriority.ThecolumnŽInitialStatusŽcorresponds theInitialstatusaftertheblackoutandColumnsŽFriendlystageŽandŽPersistentStageŽ correspondtotheLoadstatusaftereachnegotiationstagerespectively. Generator Line Limit Status PersistantStage 100 B100-100 43.3 Available 0 103 B103-103 10000 Available 815.6 111 B111-111 189 Available 0 112 B112-112 10000 Available 493.91 115 B115-115 0.7 Available 0 116 B116-116 10000 Available 984 118 B118-118 10000 Available 6538.6 TotalGenerated 8832.11 Table5.21:WSCC179-bussystem-Zone2-A-Generatorsstatus 82

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Load Priority Value Initialstatus Friendlystage PersistentStage 101 1 210.4 un-served served served 102 3 50 un-served served served 103 1 100 un-served served served 104 2 305 un-served served served 105 2 27.5 un-served served served 106 2 8.01 un-served served served 107 1 265 un-served served served 108 2 55.6 un-served served served 109 1 777.6 un-served served served 110 3 40 un-served served served 112 3 100 un-served served served 113 2 148 un-served served served 116 3 100 un-served served served 117 3 884 un-served served served 118 3 100 un-served served served 119 3 5661 un-served un-served served TotalLoads 8832.11 35.9% 100% Table5.22:WSCC179-bussystem-Zone2-A-Loadsstatus Resultsofsimulation-Zone2-B InthiszonetheIPRnetworkcouldallocateresourcesfor84%ofloadsinthebest caseand76%ofloadsintheworsecase.Butineverysimulation, everyhigh-priority loads aresuppliedinthiszonewiththeinternalgenerationcapacityofthiszone.The resourcesallocationchangeineachsimulation.Table5.23presentsthePowerAllocation foreachgeneratorsinthiszone.ThecolumnŽGeneratorŽcorrespondstothebuswherethe generatorisconnected.ThecolumnŽLineŽcorrespondstheIdenti“erofthelinebetween theGeneratoranditsbus.ThecolumnŽLimitŽcorrespondstotheGeneratorCapacity, ColumnŽStatusŽcorrespondstoGeneratorAvailabilityandColumnŽFinalŽcorresponds toPowerAllocationforeachgenerator. TheTable5.24presentsthestatusofeachLoadinthiszoneduringthenegotiation process.ThecolumnŽLoadŽcorrespondstothebuswheretheloadisconnected.ThecolumnŽPriorityŽcorrespondstotheLoadPriority.ThecolumnŽInitialStatusŽcorresponds 83

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theInitialstatusaftertheblackoutandColumnsÂŽFriendlystageÂŽandÂŽPersistentStageÂŽ correspondtotheLoadstatusaftereachnegotiationstagerespectively. Generator Line Limit Status Final Gen13 B13-Gen13 10000 Available 3287.2 Gen15 B15-Gen15 10000 Available 2155.4 Gen37 B37-Gen37 1862 Available 0 Gen40 B40-Gen40 10000 Available 921.6 Gen43 B43-Gen43 10000 Available 537 Gen46 B46-Gen46 72.8 Available 0 Gen47 B47-Gen47 10000 Available 1012.5 Gen60 B60-Gen60 2771 Available 0 Gen63 B63-Gen63 129 Available 0 Gen138 B138-Gen138 10000 Available 1206.5 Gen140 B140-Gen140 10000 Available 3291 Gen144 B144-Gen144 10000 Available 100 Gen148 B148-Gen148 10000 Available 1330 Gen149 B149-Gen149 10000 Available 3676 TotalGenerated 17517.2 Table5.23:Generatorsstatus-WSCC179-bussystem-Zone2-B 84

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Load Priority Value Initialstatus Friendlystage PersistentStage 12 1 90 Un-served served served 13 3 100 Un-served served served 15 1 100 Un-served served served 16 3 793.4 Un-served served served 19 3 617 Un-served served served 40 3 100 Un-served served served 41 3 135 Un-served un-served served 43 3 100 Un-served served served 47 3 100 Un-served served served 48 3 121 Un-served served served 50 2 320 Un-served served served 51 3 237.2 Un-served un-served served 54 2 138 Un-served un-served served 55 3 807.8 Un-served un-served served 57 1 117 Un-served served served 58 3 121 Un-served served served 59 2 887.7 Un-served un-served served 61 1 401 Un-served un-served served 62 2 205.2 Un-served served served 136 2 856 Un-served served served 137 2 175 Un-served un-served served 138 1 100 Un-served served served 139 3 902.3 Un-served served served 140 3 100 Un-served served served 141 2 3191 Un-served served served 142 1 204.2 Un-served un-served served 143 1 377.4 Un-served un-served served 144 3 100 Un-served served served 145 2 3098 Un-served un-served un-served 148 1 100 Un-served served served 149 2 100 Un-served served served 150 3 3118 Un-served un-served served 151 3 1230 Un-served served served 152 3 406 Un-served served served 154 1 1066 Un-served un-served served TotalLoads 20615.2 48.36% 84.97% Table5.24:Loadsstatus-WSCC179-bussystem-Zone2-B 85

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86

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5.3Inter-zonescenariosInordertodemonstratetheeectivenessoftheInter-zonenegotiationalgorithms, wepresentseveralscenarioswherethenegotiationforthesystemrestorationoccursinthe Inter-zonelevel.Firstwehaveonemodi“cationofWSCCnine-bussystemdividedintotwo zones;assecondscenariowepresenttwomodi“edWSCCnine-bussysteminterconnected, eachsystemisazone.Finally,wepresentamodi“cationoftheWSCC179-bussystem dividedin“vezoneswithsomemodi“cationinpowerlimitsofthegenerators.5.3.1WSCCnine-bussystemThemodelusedconsistsofanetworkofthreegenerators,ninebusesandthree loadsasdepictedin“gure5.14.Thesystemisdividedintotwozones: € Zone1formedbygenerator1,load3andbuses7,1,6. € Zone2formedbygenerators2,3;loads1,2;andbuses2,3,4,5,8,and9. TheobjectiveofthisscenarioisdemonstratethecapacityofInter-zonealgorithms tosupplyloadswhentheintra-zonenegotiationcannotdoit. Figure5.13:WSCCNine-bussystem-Inter-zonescenario 87

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Resultsofsimulation Afterrunningthetestcasesfourtimes,thepowerallocationnegotiatedbyIPRs cansupply100%ofthepowerrequiredbyloadsineachcase.AfterIntra-zonenegotiation loads1and2areservedbutload3arenotservedbecausethegenerationcapacityinZone 1isnotenoughtoserved.Then,load3sendsaInter-zonerequestacrossPPR6,andPPR 5getsthisrequestandproducesaintra-zonenegotiationtosupplythisrequest.Finally generator3cansupplytherequestandallloadsofthesystemareservedafterinter-zone negotiationstage. Theallocationofpowersatis“estheconstraintsestablishedinthemathematical formulation(section3.2).Moreover,thisallocationofpowerisdoneinde-centralizedmanner,usingonlylocalinformation.Table5.25presentstheallocationofpowerforlinein zone1.andTable5.26presentstheallocationofpowerforeachlineinzone2. Bus Line Limit Status Intra-zone Inter-zone B1 B1-B7 250 Un-Available 0 0 B1B2 250 Available 0 0 B1B6 250 Available 0 0 B6 B5B6 150 Available 0 90 B1B6 250 Available 0 0 B6-Load3 90 Available 0 90 B7 B1-B7 250 un-Available 0 0 B7-Gen1 250 Available 0 0 Table5.25:WSCCnine-bussystem-Inter-zonescenario-Zone1-Busandlinesstatus 88

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Bus Line Limit Status Intra-zone Inter-zone B2 B1B2 250 Available 0 0 B2B3 250 Available 110 110 B2-Load1 110 Available 110 110 B3 B3-B8 300 un-Available 0 0 B2B3 250 Available 110 110 B3B4 250 Available 110 110 B4 B3B4 250 Available 0 50 B4B5 250 Available 210 210 B4-Load2 100 Available 100 100 B5 B5-B9 300 Available 210 300 B4B5 250 Available 210 150 B5B6 150 Available 0 90 B8 B2-B8 300 un-Available 0 0 B8-Gen2 300 Available 0 0 B9 B5-B9 300 Available 210 300 B9-Gen3 300 Available 210 300 Table5.26:WSCCnine-bussystem-Inter-zonescenario-Zone2-Busandlinesstatus Generator Zone Line Limit Status Intra-zone Inter-zone Gen1 1 B7-Gen1 250 Available 0 0 Gen2 2 B8-Gen2 300 Available 0 0 Gen3 2 B9-Gen3 300 Available 210 300 Table5.27:WSCCnine-bussystem-Inter-zonescenario-Generatorstatus Load Zone Priority Value Initialstatus Intra-zone Inter-zone Load1 1 2 110 Un-served Served Served Load2 1 1 100 Un-served Served Served Load3 2 3 90 Un-served un-served Served Table5.28:WSCCnine-bussystem-Inter-zonescenario-Loadsstatus 89

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5.3.2WSCCnine-bussystem-interconnectedtwosystemsThemodelusedconsistsofanetworkofsixgenerators,eighteenbusesandsix loadsasdepictedin“gure5.14.Thesystemisdividedintotwozones,eachoneisaWSCC nine-bussystem. TheobjectiveofthisscenarioisdemonstratethecapacityofInter-zonealgorithms tosupplyloadswhentheintra-zonenegotiationcannotdoit. Figure5.14:WSCCNine-bussystem-Interconnectedtwosystems Resultsofsimulation Afterrunningthetestcasesfourtimes,thepowerallocationnegotiatedbyIPRs cansupply100%ofthepowerrequiredbyloadsineachcase.AfterIntra-zonenegotiation inzone1,loads1and2areservedbutload3arenotservedbecausethegenerationcapacity inZone1isnotenoughtoserved.Whilezone2reachestosupplyitsloads.Then,load3 ofzone1sendsaInter-zonerequestacrossPPR6,andPPR2ofzone2getsthisrequest andproducesaintra-zonenegotiationtosupplythisrequest.Finallygenerator2ofzone2 cansupplytherequestandallloadsofthesystemareservedafterinter-zonenegotiation 90

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stage. Theallocationofpowersatis“estheconstraintsestablishedinthemathematical formulation(section3.2).Moreover,thisallocationofpowerisdoneinde-centralizedmanner,usingonlylocalinformation.Table5.29presentstheallocationofpowerforlinein zone1.andTable5.32presentstheallocationofpowerforeachlineinzone2. Bus Line Limit Status Intra-zone Inter-zone B1 B1-B7 250 NoAvailable 0 0 B1B2 250 Available 0 0 B1B6 250 Available 125 125 B2 B1B2 250 Available 125 125 B2B3 250 Available 0 0 B2-Load1 125 Available 125 125 B3 B3-B8 300 un-Available 0 0 B2B3 250 Available 0 0 B3B4 250 Available 0 0 B4 B3B4 250 Available 0 0 B4B5 150 Available 100 100 B4-Load2 100 Available 100 100 B5 B5-B9 400 Available 225 225 B4B5 150 Available 100 100 B5B6 250 Available 125 125 B6 B5B6 250 Available 125 125 B1B6 250 Available 125 125 B6-Load3 90 Available 0 90 B6-zone2 250 Available 0 90 B7 B1-B7 250 un-Available 0 0 B7-Gen1 250 Available 0 0 B8 B2-B8 300 un-Available 0 0 B8-Gen2 300 Available 0 0 B9 B5-B9 400 Available 225 225 B9-Gen3 270 Available 225 225 Table5.29:WSCCNine-bussystem-Interconnectedtwosystems-Zone1-Busandlines status 91

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Generator Line Limit Status Intra-zone Inter-zone Gen1 B7-Gen1 250 Available 0 0 Gen2 B8-Gen2 300 Available 0 0 Gen3 B9-Gen3 270 Available 225 225 Table5.30:WSCCNine-bussystem-Interconnectedtwosystems-Zone1-Generator status Load Priority Value Initialstatus Intra-zone Inter-zone Load1 2 125 Un-served Served Served Load2 1 100 Un-served Served Served Load3 3 90 Un-served Un-served Served Table5.31:WSCCNine-bussystem-Interconnectedtwosystems-Zone1-Loadsstatus Bus Line Limit Status Intra-zone Inter-zone B1 B1-B7 250 Available 90 0 B1B2 250 Available 0 0 B1B6 250 Available 90 90 B2 B1B2 250 Available 0 0 B2B3 250 Available 125 125 B2-Load1 125 Available 125 125 B6-zone2 250 Available 0 90 B3 B3-B8 300 Available 125 215 B2B3 250 Available 125 215 B3B4 250 Available 0 0 B4 B3B4 250 Available 0 0 B4B5 150 Available 100 100 B4-Load2 100 Available 100 100 B5 B5-B9 400 Available 100 100 B4B5 150 Available 100 100 B5B6 250 Available 0 0 B6 B5B6 250 Available 0 0 B1B6 250 Available 90 90 B6-Load3 90 Available 90 90 B7 B1-B7 250 Available 90 90 B7-Gen1 250 Available 90 90 B8 B2-B8 300 Available 125 215 B8-Gen2 300 Available 125 215 B9 B5-B9 400 Available 100 100 B9-Gen3 270 Available 100 100 Table5.32:WSCCNine-bussystem-Interconnectedtwosystems-Zone2-Busandlines status 92

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Generator Line Limit Status Intra-zone Inter-zone Gen1 B7-Gen1 250 Available 90 90 Gen2 B8-Gen2 300 Available 125 215 Gen3 B9-Gen3 270 Available 100 100 Table5.33:WSCCNine-bussystem-Interconnectedtwosystems-Zone2-Generator status Load Priority Value Initialstatus Intra-zone Inter-zone Load1 2 125 Un-served Served Served Load2 1 100 Un-served Served Served Load3 3 90 Un-served Served Served Table5.34:WSCCNine-bussystem-Interconnectedtwosystems-Zone2-Loadsstatus5.3.3WSCC179-busSystemThemodelusedconsistsofanetworkof29generators,179busesand113loads. Thesystemisdividedinto“vezones(1-A,1-B,1-C,2-Aand2-B)asdepictedin“gure 5.15.Intheoriginalmodelseveralloadsarenetworkequivalentswithanegativevalue,this meansthatinthesesectionthegenerationexceedsthedemand.Foroursimulationthese loadswithnegativeloadsaregenerators.Thenthenumberofgeneratorincreasewhilethe numberofloadsdecrease. InthisscenariointheZone1-Bthegenerator45canoperateonlyat50%ofits capacity.ThetransmissionlinebetweenZone1-BandZone1-Cisdisconnected,andthe followingthreelinesinZone1-Bareout-of-service: € 36-85 € 159-158 € 162-161 Withthiscon“guration,theIPRsinZone1-BneedtouseInter-zonenegotiationto supplytheirloadsbecausethelocalgeneratorsforZone1-Bareunreachablefortheloads. 93

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Theobjectiveofthisscenarioistorestorethesystemafteratotalblackout.We workedwithlessPrincipalPowerRoutersthanbusinthesystembecauseaPPRcould manageoneormorebuses. Resultsofsimulation Afterrunningseparatelyseveralsimulationsforeachzone,inasimilarfashionto Intra-zoneresults,weobtainthatinzones1-A,1-B,1-Cand2-AtheIPRnetworkcould allocateresourceseverytimetosupplyallloads.ButinZone2-BtheIPRnetworkcould allocateresourcesfor84%ofloadsinthebestcaseand76%ofloadsintheworsecasebut everyhigh-priorityloads aresuppliedinthiszone. Inthiscasetheloads85,161,164,165and166ofZone1-Bareservedbygenerators inZone1-A,becausethecapacityoftheavailablelinesinzone1-Bisnotenoughtosupply theseswiththegenerationcapacityintothiszone.Then,theSinkPowerRouterconnected toLoad85sendsasetofInter-zonerequests,andthisrequestisansweredbygeneratorsin theZone1-A(azonerichingeneration). Theallocationofpowersatis“estheconstraintsestablishedinthemathematical formulation(section3.2).Moreover,thisallocationofpowerisdoneinde-centralizedmanner,usingonlylocalinformation. 94

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Figure5.15:WSCC179-busmodel 95

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Figure5.16:WSCC179-busmodel-Inter-zonescenario-Zone1-B Table5.35presentsthepowerallocationforgeneratorsinZone1-AandTable 5.36presentsthepowerallocationforgeneratorsinZone1-B.InthesetablestheColumn ŽGeneratorŽcorrespondstotheIdenti“erofeachgenerator.ThecolumnŽLineŽcorresponds tothepowerlinethatconnectsGeneratorswithitsbus.ThecolumnŽlimitŽcorresponds toGeneratorCapacity,columnŽStatusŽcorrespondstoAvailabilityofeachgenerator.And thecolumnŽFinalŽcorrespondstopowerallocationforeachgenerators.Inthissectionwe presentonlyresultsforZones1-Aand1-B,becausetheotherszonehavesimilarresultsas wepresentedinsectionofIntra-zoneresults. TheTable5.37presentsthestatusofeachLoadinthiszoneduringthenegotiation processfortheZone1-A.ThecolumnŽLoadŽcorrespondstothebuswheretheloadis connected.ThecolumnŽPriorityŽcorrespondstotheLoadPriority.ThecolumnŽInitial StatusŽcorrespondstheInitialstatusaftertheblackoutandColumnsŽFriendlystageŽand ŽPersistentStageŽcorrespondtotheLoadstatusaftereachnegotiationstagerespectively. TheTable5.38presentsthestatusofeachLoadinthiszoneduringthenegotia96

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Generator Line Limit Status Final Gen30 B30-Gen30 10000 Available 4500 Gen35 B35-Gen35 10000 Available 3700 Gen65 B65-Gen65 10000 Available 5135.2 Gen68 B68-Gen68 67.5 Available 0 Gen69 B69-Gen69 44.2 Available 0 Gen70 B70-Gen70 10000 Available 972 Gen73 B73-Gen73 1525 Available 0 Gen77 B77-Gen77 10000 Available 5003.6 Gen79 B79-Gen79 10000 Available 9987 Gen82 B82-Gen82 66.6 Available 0 Gen83 B83-Gen83 339 Available 0 TotalGenerated 29297.8 Table5.35:WSCC179-bussystem-Zone1-A(Inter-zonescenario)-Generatorsstatus Generator Line Limit Status Final Gen36 B36-Gen36 10000 Available 100 Gen45 B45-Gen45 5000 Available 3093.7 Gen159 B159-Gen159 10000 Available 100 Gen160 B160-Gen160 62 Available 0 Gen162 B162-Gen162 10000 Available 100 TotalGenerated 3393.7 Table5.36:WSCC179-bussystem-Zone1-A(Inter-zonescenario)-Generatorsstatus Load Priority Value Initialstatus Friendlystage PersistentStage 30 2 100 Un-served Served Served 31 3 4400 Un-served Served Served 34 2 3600 Un-served Served Served 35 3 100 Un-served Served Served 65 3 100 Un-served Served Served 66 3 1700 Un-served Served Served 67 3 160 Un-served Un-served Served 70 3 100 Un-served Served Served 71 3 3137 Un-served Un-served Served 75 3 2584 Un-served Un-served Served 76 3 3200 Un-served Served Served 77 3 100 Un-served Served Served 78 1 3500 Un-served Un-served Served 79 2 100 Un-served Served Served 80 2 5000 Un-served Served Served TotalLoads 27881 66.35% 100% Table5.37:WSCC179-bussystem-Zone1-A(Inter-zonescenario)-Loadsstatus 97

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tionprocessfortheZone1-B.ThecolumnÂŽLoadÂŽcorrespondstothebuswheretheloadis connected.ThecolumnÂŽPriorityÂŽcorrespondstotheLoadPriority.ThecolumnÂŽInitial StatusÂŽcorrespondstheInitialstatusaftertheblackoutandColumnsÂŽIntra-zonephaseÂŽ andÂŽInter-zonephaseÂŽcorrespondtotheLoadstatusaftereachnegotiationphaserespectively.NoticethatLoads85,161,164,165and166stillun-servedafterIntra-zone,butafter Inter-zonephasetheseloadsareserved. Load Priority Value Initialstatus Intra-zonephase Inter-zonephase 36 2 100 un-served served served 44 1 2053 un-served served served 45 3 100 un-served served served 85 1 610 un-served un-served served 155 3 457.7 un-served served served 156 3 33.9 un-served served served 157 3 148 un-served served served 158 3 116.1 un-served served served 159 1 100 un-served served served 161 2 255 un-served un-served served 162 3 100 un-served served served 164 1 31.6 un-served un-served served 165 2 141.2 un-served un-served served 166 3 379 un-served un-served served 167 2 185 un-served served served TotalLoads 4810.5 70.4% 100% Table5.38:WSCC179-bussystem-Zone1-B(Inter-zonescenario)-Loadsstatus5.4ExperimentalresultssummaryInthischapter,wehavepresentedseveralsimulationscenariostodemonstratethe eectivenessofourIPRsNegotiation.Thesescenariosareorganizedintwogroups,IntrazonescenariosandInter-zonescenarios.IneveryscenariotheIPRsobtainsuccessfullythe reservationofpowerneededtosupplyallloadsoratleastthehigh-priorityloads. 98

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CHAPTER6ConclusionandFutureWorkEverysocialandeconomicfunctionofoursocietyishighlydependentonElectrical EnergyDeliveryNetworks-EEDN,thereforeitshighreliabilityisalwaysrequired.Currently,tomaketheEEDNtoleranttofailuresandimprovetheirreliability,PowerDelivery Systemsaredesignedwithredundantpowergeneratorsanddeliverylines.However,the decisionforsystemcontrolandcoordinationaremadeinacentralizedmannerfromonlya fewsites(controlscenters).Thiscentralizedschemehasacleardrawback:afailureinone ofthesecontrolcentersmightresultinthetotalcollapseofthesystem. Inthisthesis,wehavepresentedanewmodelforPowerSystemRestorationbased onadistributedconceptwithscalablecoordinationusingIntelligentPowerRouters(IPRs). Obviously,theseIPRsneedarobustcontrolprotocolforguaranteeanoptimalsystem performance.Inthisthesis,wehavepresentedseveralrestorationstrategiesembeddedinto IPRs.Therestorationprotocolanddecisionalgorithmarebasedinthereliabilityfactor forinputslinesandpriorityfactorforinputlines.Also,weaddedamulti-stagenegotiation schemeasaimportantcharacteristictoimproveIPRsperformance,scalabilityandquality ofdecisions.Moreover,wehavepresentedaprototypeofIPRsnetworkthathasagood performanceforsystemrestorationinmanyscenariosusingthetest-bedsystemsdesignedby 99

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WesternSystemsCoordinatingCouncil-WSCC.Inparticular,ourintra-zonenegotiation protocolswereabletorestoreeiherallloadsorthemostcriticalones100%ofthetime. Likewise,theinter-zonenegotiationprotocolswereabletorestoremostoftheloadsinthe WSCC179-bussystem.ThisdemonstratesthefeasibilityofusingIPRsastheelements thatcandirecttherestorationofthesysteminade-centralizedmanner. Inthischapter,wepresentasummaryofthemainresultsandcontributionsof thisthesis.Inaddition,weoerasetoffuturedirectionsforIPRsdevelopment.6.1SummaryofContributionsInthisresearchthemajorcontributionisthedevelopmentofacompletelydistributedframeworktosolvetheproblemofElectricalPowerSystemRestoration.Traditionally,thisproblemhasbeenresolveusingcentralizedsolutions,withtheriskassociated tothisapproach.Inourframework,theintelligencethatcanbeusedforcontrolandcoordinationoperationsisembeddedintoaseriesofcomputingdevicescalledtheIntelligentPower Routers(IPRs)[1].TheseIPRsarestrategicallyconnectedtopowergeneratorsandpower lines,thusenablingthemnotonlytoobservecurrentnetworkconditions,butalsocooperate witheachothertoactivelyalternatelinestomovepowerfromproducerstoconsumers. Inchapter3,wepresentedourMappingofElectricalEnergyDistributionNetworks (EEDN)toaWideAreaNetwork(WAN)withthesimilaritiesbetweenWANelementsand EEDNelements.Additionallyinthatchapter,wepresentedourmathematicalformulation withourobjectivefunctionandmodelconstraintstomaintainphysicalconsiderationsfor ElectricalPowerSystems.Also,wehavepresentedourIPRNetworkArchitectureasa peer-to-peernetwork.Inthisarchitecture,itisirrelevantwhetheritsinputscomedirectly frompowerproducersorotherIPRs.Thekeytoourapproachistoprovidemultiple redundantpowerpathsbetweenproducers(generators)andconsumers(loads).Finally,we 100

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havepresentedthesplitrequestschemetoimprovetheIPRsperformanceincreasingthe numberofpossibilitiesofpathstosupplytheLoadrequests. Chapter4presentstheIsland-zoneapproachforcontrollingthenumberofmessages travellingonthenetwork.Withthisapproachthesystemisdividedinseveralzones. Eachzoneisasub-systemwithgenerators,busesandloadsthatneedtoberestored.The restorationschemedevelopedinthatchapterisdividedintwophases.The“rstphase(IntrazonePhase)isdesignedtoperformtherestorationprocessusingthelocalresourcesineach zone.Andthesecondphase(Inter-zonePhase)istherestorationprocessusingthecapacity intheneighboringzones.Additionally,inchapter4wehavepresentedthenecessarymessage typestoperformtherestorationprocessusingtheIPRnegotiationscheme. TheeectivenessofIPRnegotiationscheme,fortherestorationprocessinadecentralizedform,waspresentedinchapter5.Chapter5presentsseveralsimulationscenarios usingthetest-bedsystemsdesignedbytheWesternSystemsCoordinatingCouncil-WSCC. Thissimulationscenariosaredividedintotwogroups.The“rstgroupisorientedtodemonstratetheeectivenessofIntra-zonenegotiationschemeandthesecondgroupisorientedto demonstratetheeectivenessofInter-zonenegotiationscheme.Finally,theeectivenessof theIPRNegotiationSchemeisdemonstratedineveryscenario,sincetheIPRswhereable tosuccessfullyobtainthereservationofpowerneededtosupplyallloads(inmostofthe cases),oratleastforthehigh-priorityloads. Insummary,inthisthesiswehavepresentedanewschemetoperforminadistributedanddecentralizedformfortherestorationprocessforElectricalEnergyDelivery Networks,availableforTransmissionandDistributionsystems. 101

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6.2FutureWorkWehaveproposedfutureworktoimprovethequalityofdecisionandIPRsperformance: 1.Thenextstepofthisresearchmustbeorientedtocalculatethereliabilityandpriority factorsdynamicallyandadaptivelywhilesystemconditionschange.Theresponsetime oftheIPRNegotiationisassociatedwiththespeedofIPRNetworktoestablishthe adequatepathbetweengeneratorsandloads.Noticethatifthereliabilityandpriority factorre”ecttherealsystemconditionsallthetime,thentheIPRsdonotwastetime searchingthroughlow-reliabilitypossibilities. 2.WeproposetoinvolveothercharacteristicsoftheElectricalPowerSystemssuchas reactivepower,systemfrequencyandsystemvoltageintheIPRsnegotiationscheme. InthisthesiswepresenttheIPRsnegotiationschemeforsystemrestorationbutona highabstractlevel,todeploytheseconceptsinthephysicalsystemsitisnecessaryto considerateotherphysicalcharacteristicsofElectricalPowerSystems.Inaddition,it isnecessarytoimplementthemechanismsnecessarytoperformtheswitchingoperationsthatenablethepower”owsthattherestorationplanspeci“es(whichtheIPRS generate). 3.Weproposemodifythenegotiationschemetopermitthepartialrestorationofthe loads.Inpowersystemsispossiblerestoredaportionofagivenload,becausegenerally eachloadisrepresentingasetofloads. 4.Finally,ourIPRsmustpre-computeasetofcontingencyplanstoimprovetheirresponsetimewithinformationabouthistoricalcontingencies.Thesecontingencyplans willbebasedonreservingresources,suchasportionsoflinecapacity,foreachIPR acrossthenetwork. 102

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BIBLIOGRAPHY[1]V elez-ReyesM.Cede noJ.V elezB.ONeill-CarrilloE.Ram šrezA.Irizarry-RiveraA., RodrguezM.IntelligentPowerRoutersforDistributedCoordinationinElectricEnergy ProcessingNetworks. 2003EPNESWorkshop ,October23-242003. [2]SasakiH.A.NagataT.Multi-AgentApproachtoPowerSystemRestoration. IEEE TransactionsonPowerSystems ,17(2):457…462,march2002. [3]D.W.FellhoelterK.J.Allen,W.Fletcher.Securingcriticalinformationandcommunicationinfrastructuresthroughelectricpowergridindependence. The25thInternational TelecommunicationsEnergyConference, ,October19-232003. [4]DavieBrucePetersonLarry. ComputerNetworksasSystemapproach .MorganKaufmann,secondeditionedition,2000. [5]vanSteenMaartenTanembaumAndrews. DistributedSystems,principlesandparadigmas .PrenticeHall,2002. [6]IEEE.IEEEDistributedSystemson-line. URL:http://dsonline.computer.org/portal/site/dsonline/index.jsp. [7]TanembaumAndrews. ComputerNetwork .PrenticeHall,2002. [8]VijayTewari.AFrameworkforClassifyingPeer-to-PeerTechnologies. ClusterComputingandtheGrid2ndIEEE/ACMInternationalSymposiumCCGRID. ,2002. [9]RodriguezM.VergaraI.CarvajalJ.,CarvajalC.SupportingMultimediaApplications withNetTraveler. 7thIASTEDInternationalConferenceonInternetandMultimedia SystemsandApplications ,August2003. [10]CoronadoEnna. SRE:SearchandRetrievalEngineoftheTerraScopeDatabaseMiddlewareSystem .UPRM,2003. [11]RehtanzChristian. AutonomousSystemsandIntelligentAgentsinPowerSystemControlandOperation .Springer,“rstedition,2003. [12]WangYuehai;HongBing-rong.Multi-AgentApproachtoPowerSystemRestoration. IntelligentControlandAutomation,2002.Pro ceedingsofthe4thWorldCongresson 4:3205…3209,june2002. [13]ChapmanStephenJ. ElectricMachineryandPowerSystemFundamentals .McGrawHill,2001. 103

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[14]McDonaldJ.D.Substationautomation.IEDintegrationandavailabilityofinformation. IEEEPowerandEnergyMagazine ,1:22…31,March-April2003. [15]M.UtataniH.Sasaki.T.Nagata,H.Nakayama.AMulti-agentApproachtoPower SystemNormalStateOperations. IEEEPowerEngineeringSocietySummerMeeting march2002. [16]TamassiaRobertoGoodrichMichael. AlgorithmDesign-Foundations,Analysisand InternetExamples .JohnWiley&Sons,Inc.,2002. [17]PrasadV.ButlerK.L.,SarmaN.D.R.NetworkRecon“gurationforServiceRestorationinShipboardPowerDistributionSystems. IEEETrans.OnPowerSystems ,16:653 …661,November2001. [18]JuanJim enez. ParticleSwarmOptimizationApplicationinPowerSystemsEngineering .UPRM,2004. [19]WECC.WesternElectricityCoordinatingCouncil. http://www.wecc.biz/wrap.php?“le=wrap/about.html. 104

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APPENDICES105

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APPENDIXAMulti-stageNegotiationalgorithmsA.1IPRsNegotiationalgorithmsInsection3.6wepresentedthebasicnegotiationschema,inthissectionwepresent thecomplexnegotiationschemainvolvingIPRnegotiationprocessisintwophases.A.1.1Intra-zonealgorithmsThealgorithmsforintra-zonephasearedesignedtoperformnegotiationina FriendlyandaPersistentstages.Inthefriendlystagethenegotiationisperformedas describedinsection3.6. BelowwepresentthealgorithmsforPersistentandLoadsheddingstagedivided inthreesection:forSinkPR,forSourcePrandforPrincipalPR. ForSinkPowerRouters(SnkPr): SendaPersistentGetMessage Waitforresponse 106

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ifresponseisaPutMessage connectload else SendaMandatoryGetMessage Waitforresponse ifresponseisaPutMessage Connectload else BeginInter-zoneprocess endif endif ForSourcePowerRouters(SrcPr) Waitformessage ifmessageisaPersistentGetMessage CheckGeneratorCapacity ifGeneratorcansupplyrequest sendPutMessage else sendaDeniedMessage endif else ifmessageisMandatoryGetMessage ifSrcPRcansupplyrequestdisconnecting low-priorityservedloads sendDisconnectMessages 107

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WaitforDisconnectConfirmationMessages Allocateresourcesforrequest sendPutMessage else sendDeniedMessage endif endif endif ForPrincipalPowerRouters mainfunction Waitformessage selectmessageTypecase casePersistentGetMessage: processPersistentGetMessage break casedeniedmessage processdeniedmessage break casePutmessage processputmessage break caseDisconnectMessage processDisconnectMessage break caseDisconnectConfirmationMessage processDisconnectConfirmationMessage 108

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break caseMandatorygetmessage processMandatorygetmessage break caseMandatorychangemessage processchangemessage break endselectcase; endfunction functionprocessPersistentGetMessage Checksourcemessagepriority Storethemessageinrequestqueue SendaStatusRequesttoallothersclients withhigherpriorityaskingtheirstatus. WaittimeTtoacquireresponses. Foreachresponse Ifresponseisnotnormalstatus Storethemessageinrequestqueue Endif Changeoutputlinestoinputlinesifitispossible Foreachmessageinrequestqueue RepeatuntilgetanOKresponseorobtain denymessagefromallpowersupplier AdjacentIPR Iflinkcapacitycansupportmorepowerflow SendgetmessagetoIPRwithmost 109

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reliablelinenotyetinspected Waitforresponse IfOKresponse SendOkresponsetoclient Endif IfIPRobtainsdenymessagefromallIPRs SendDeniedMessagetoclient Endif Endif Endrepeat endfunction functionprocessDeniedmessage checkpendingqueuefororiginalrequest iforiginalrequestisasplitrequest Senddeniedmessagetoclient Senddisconnectconfirmationacrossinputlinewith affirmativeresponse de-allocateresourcesallocatedforthisrequest else Checkavailablecapacityininputlines ifavailablecapacity>=requestvalue Splitrequest sendpartialrequestsacrossselectedlines else Checklower-priorityservedrequeststhanactual request 110

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iflower-priorityservedrequestvalue>=actual requestvalue SendrequiresDisconnectMessages foreachDisconnectMessage WaitforDisconnectConfirmationMessage processDisconnectConfirmationMessage SendrequiresMandatoryChangeMessage else SendDeniedMessagestoclient endif endif endif endfunction functionprocessputmessage checkpendingqueuefororiginalrequest ifsplitrequest setinputlinewithaffirmativeresponse checkforothersinputlinesinvolvedinactual request ifeveryinvolvedinputlineshaveaffirmative response Allocateresources sendPutMessagetoClient else Waitforothersresponses endif 111

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else Allocateresources sendPutMessagetoClient endif endfunction functionprocessDisconnectMessage routedisconnectmessageacrossappropriatedoutputlines endfunction functionprocessDisconnectConfirmationMessage routeDisconnectConfirmationMessageacrossappropriatedinputlines de-allocateappropriatedresources endfunction functionMandatorygetmessage Checklower-priorityservedrequeststhanactualrequest iflower-priorityservedrequestvalue>=actual requestvalue SendrequiresDisconnectMessages foreachDisconnectMessage WaitforDisconnectConfirmationMessage processDisconnectConfirmationMessage SendrequiresMandatoryChangeMessage else SendDeniedMessagestoclient 112

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endif endfunction functionMandatoryChangeMessage Checkobjectiverequestthatwasdisconnected Changeappropriatedparameterstoallocateresources foractualrequest sendMandatoryChangemessageacrossappropriated inputlines endfunctionA.1.2Inter-zonealgorithmsFortheInter-zonenegotiationschemawehavedesignedthefollowingalgorithms. InthisphaseareinvolvedonlySinkPowerRoutersandPrincipalPowerRouters. ForSinkPowerRouter SendaInter-zoneRequestMessage Waitforresponse ifresponseisaPutMessage connectload else beginaIntra-zoneProcess endif ForPrincipalPowerRoutersweuseBasicnegotiationalgorithmmodi“edwith conditionifitisaBorderPowerRouteritmustsendaInter-zoneGetMessage. 113

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Waitformessage ifmessageisaInter-zoneRequest ifactualPowerrouterisaBorderPowerRouter sendaInter-zoneGetMessage Waitforresponse IfaPutInter-zonemessage sendaputmessagetoclient else RoutethemessageasanIntra-zonemessageuntil reachanotherBorderPowerRouterorgeta intra-zoneresponse(putordeniedmessage) endif else ifmessageisaInter-zonegetmessage beginIntra-zonenegotiationprocess waitforaIntra-zoneresponse ifIntra-zoneresponseisaPutmessage sendaInter-zonePutmessagetooriginalzone else sendaInter-zoneDeniedmessagetooriginalzone endif else messageisanIntra-zonerequestanditmustberouted withintra-zonealgorithms endif endif 114