Influence of Wind Farms on Power System Dynamic an

Page1of34InfluenceofWindFarmsonPowerSystemDynamicandTransientStabilitySummaryreportM.Hughes,O.Anaya-Lara,N.JenkinsandG.StrbacFebruary2005DTICentreforDistributedGenerationandSustainableElectricalEnergyInfluenceofwindfarmsonpowersystemdynamicandtransientstabilityPage2of34ExecutiveSummaryTheaimoftheworkofthisreportwastoinvestigatethewaysinwhichbulkwindfarmgenerationwouldinteractwithconventionalgenerationandinfluencenetworkfundamentaldynamiccharacteristics.ThereportisbasedoncurrentstudiesbeingcarriedoutattheUniversityofManchesteraspartoftheworkoftheDTICentreforDistributedGenerationandSustainableElectricalEnergy.TheUKGovernmenthasadeclaredtargetthatrenewableenergyshouldprovide15%ofUKelectricitysuppliesby2015.Theintegrationofsuchlevelsofrenewablegeneration,mainlyfromwindenergy,intotheUKpowernetworkwillheavilyinfluencenetworkcharacteristicsandpushnetworkoperationintocurrentlyunknownterritory.Whilsttheoperation,controlcapabilitiesanddynamiccharacteristicsofnetworkscomprisingsynchronousgenerationarewellestablishedandunderstood,thesamecannotbesaidfornetworkshavingmixedsynchronousandinductiongenerators.Inlightofthis,studiesarepresentlybeingcarriedouttoestablishanunderstandingofthebasicinteractionanddynamiccharacteristicsofsuchmixedgenerationsystemsandtheoutcomeoftheinitialworkdoneisreportedhere.Asimplegenericnetworkmodel,basedonathree-generatorsystem,isusedforthepresentdynamicstudies.InordertoprovideresultsandcharacteristicsthatcouldbeconsidereddirectlyrelevanttotheUKnetwork,anoperatingsituationwasconsideredinwhichonesynchronousgeneratorwaschosentohavethecombinedgeneratingcapacityoftheEngland-Walesnetwork,anothersynchronousgeneratortohavethecombinedcapacityoftheSouthernScotlandnetworkandthethirdgeneratortohaveaprojectedwindgenerationcapacityfortheNorthernScotlandnetwork.AppropriatevaluesforthegenerationandtransmissionlineinterconnectionswerechoseninconsultationwithNGT.WhilstthissimplegenericmodelisinnowayintendedasananalogueoftheUKnetwork,itisconsideredtoreflectthebasicdynamicinteractionsthatwillinfluencethebehaviouroftheUKnetworkwhenbulkwindgenerationispresent.Timeresponsesimulationandeigenvalueanalysisisusedtoestablishbasictransientanddynamicstabilitycharacteristics.AvarietyofgeneratingsituationsareconsideredforthegeneratortakentorepresentthenorthernScotlandsubnetwork.ThewindgenerationisprovidedeitherbywindfarmsbasedonFixedSpeedInductionGenerators(FSIGs)orDoublyFedInductionGenerators(DFIGs).Inaddition,inordertoprovideabaselineagainstwhichwindfarminfluenceonnetworkdynamicscanbejudged,thecaseisalsoconsideredwherethepowerexportedisprovidedbyconventionalsynchronousgeneration.Dependentonthefollowingassumptionsmadeinthemodelling,namely:1.TheconvertersaresufficientlyrobusttocaterforallthedemandsoftheDFIGcontrollerduringtransientoperation.2.Thesimplifiedmodelusedfortheconverterandits‘crowbarprotection’providesanadequaterepresentationofbehaviourforthesituationsstudied.3.TheDFIG3rdordermodel,thatignoresstatordynamicsandwaschosenforitscompatibilitywiththemodelsnormallyusedforconventionalsynchronousgeneratorsinpowersystemanalysispackages,adequatelyrepresentsdynamicbehaviourforthesituationsstudied.4.Themodelrepresentingtheshaftdynamicsoftheturbine/generatorsystemthatignorestorsionaloscillationsisappropriate.5.Thenumerousgeneratorsofwindfarmgenerationcanberepresentedcoherentlyasasinglegenerator.InfluenceofwindfarmsonpowersystemdynamicandtransientstabilityPage3of34Thestudiesindicatethefollowing:i)FSIGbasedwindfarmscancontributesignificantlytonetworkdamping,butarevulnerabletonetworkfaults.ii)ThecontrolflexibilityandcapabilityofDFIGbasedwindfarmsenablesuchgenerationtocontributepositivelytonetworkoperationintermsofvoltagerecoveryfollowingfaultsandimprovedsystemdamping.iii)ADFIGhasthepotentialofprovidingsuperiordynamicandtransientperformancethanthatofaconventionalsynchronousgenerator.iv)TheresultsusingthenewlydevelopedFMACcontrolschemedemonstratetheimportanceofDFIGcontrolinprovidinggoodoperatingperformanceandnetworksupport.Fromwhichitcanbeconcludedthat:i)Inmixedgenerationnetworks,bulkwindgenerationbasedentirelyonFSIGbasedwindfarmswouldmakethenetworkvulnerabletosystemfaults,restrictgeneratingcapacityandposeoperationalproblems.ii)BulkwindgenerationviaDFIGbasedwindfarms,suitablycontrolled,canbeaccommodatedonanetworkwithoutintroducingproblemsoftransientordynamicstabilityandcancontributepositivelytonetworkoperationandenhancenetworkdynamiccharacteristics.InfluenceofwindfarmsonpowersystemdynamicandtransientstabilityPage4of34TableofContentsExecutiveSummary.....................................................................................................2TableofContents.........................................................................................................4ListofFigures..............................................................................................................5ListofTables...............................................................................................................61.Introduction...........