Electric Power Systems

TRITA-EES-0001ISSN1100-1607OnLoadFlowControlinElectricPowerSystemsArnimHerbigStockholm2000DoctoralDissertationRoyalInstituteofTechnologyDepartmentofElectricPowerEngineeringElectricPowerSystemscArnimHerbig,January2000KTHHgskoletryckeriet,Stockholm2000AbstractThisdissertationdealswiththecontrolofactivepowerow,orloadow,inelectricpowersystems.Duringthelastfewyears,interestinthepossibilitiestocontroltheactivepowerowsintransmissionsystemshasincreasedsignicantly.Thereisanumberofreasonsforthis,comingbothfromtheapplicationsidethatis,frompowersystemoperationsandfromthetechnologicalside,whereadvancesinpowerelectronicsandrelatedtechnologieshavemadenewsystemcomponentsavailable.Loadowcontrolisbynatureamultiinputmultioutputproblem,sinceanychangeofloadowinonelinewillbecomplementedbychangesinotherlines.Strongcrosscouplingbetweencontrollablecomponentsistobeexpected,andthepossibilityofadverseinteractionsbetweenthesecomponentscannotberejectedstraightaway.Interactionswithdynamicphenomenainthepowersystemarealsoasourceofconcern.Threecontrollablecomponentsareinvestigatedinthisthesis,namelythecontrolledseriescapacitor(CSC),thephaseangleregulator(PAR),andtheuniedpowerowcontroller(UPFC).Propertiesandcharacteristicsofthesedevicesareinvestigatedanddiscussed.Asimplecontrolstrategyisproposed.Thisstrategyisthenanalyzedex-tensively.Mathematicalmethodsandphysicalknowledgeabouttheper-tinentphenomenaarecombined,anditisshownthatthiscontrolstrategycanbeusedforafairlygeneralclassofdevices.Computersimulationsofthecontrolledsystemprovideinsightintothesystembehaviorinasystemofreasonablesize.Therobustnessandstabilityofthecontrolsystemarediscussedasareitslimits.Further,thebehaviorofthecontrolstrategyinasystemwherethemod-elingallowsfordynamicphenomenaareisinvestigatedwithcomputersimulations.Itisdiscussedunderwhichcircumstancesthecontrolactionhasbenecialordetrimentaleectonthesystemdynamics.Finally,agraphicalapproachforanalyzingtheeectofcontrollersontheclosedloopbehaviorofasystemisdiscussed.Thephaserootlocustechniqueispresentedanditsapplicationtopowersystemsillustrated.TRITA-EES-0001ISSN1100-1607iiiivAcknowledgmentsThisdissertationcoverstheworkIhavecarriedoutatthedivisionofElectricPowerSystems,DepartmentofElectricPowerEngineering,RoyalInstituteofTechnology,sinceFebruary1995.First,Iwouldliketoexpressmydeepestgratitudeandappreciationtomysupervisor,ProfessorGranAndersson.Hisskilledguidance,valuablecomments,stimulatingdiscussionsandsupportthroughoutthisprojecthavebeenindispensable.Iwishtothankmycolleaguesatthedivisionofelectricpowersystemsforthefriendlyatmosphere.Specialthanksgotothesecretaryofthedivi-sionMs.LillemorHyllengrenforherhelpincountlesspracticalmatters.IalsoowethankstoMr.ErikThunberg,withoutwhosehelpthecom-puteradministrationwouldhavekeptmetoobusytowritethisthesis,Mr.MehrdadGhandhariandMr.ThomasAckermann,whowerealwayshelpfulfriendsandgoodcompanyforthelunchbreaks,Mr.JonasPerssonforhishelpwithSIMPOW,andDr.LawrenceJonesforhiscollaborationonpapersanddiscussionsoncontroltheory.FinancialsupportfromtheSwedishNUTEKREGINAprojectisgrate-fullyacknowledged.Iowemyutmostandlifelonggratitudetomyparentsfortheirunfalter-ingbackingandencouragementandtheirsupportthroughthelowsanddelightinthehighsthroughtheyears.Last,butcertainlynotleast,IwouldliketothankmyancØeMs.JuleighGiddens,whoenrichesmylifeinmorewaysthanIcaneverhopetoexpress.ArnimHerbigStockholmFebruary2000vviAcronymsAcronymDescriptionACAlternatingCurrentANNArticialNeuralNetworkCSCControllableSeriesCapacitorDCDirectCurrentFACTSFlexibleACTransmissionSystemsGTOGateTurnOThyristorHVDCHighVoltageDirectCurrentKBSKnowledgeBasedSystemLQGLinearQuadraticGaussianMIMOMultiInputMultiOutputNASANationalAeronauticsandSpaceAdministrationNASREMNASA/NISTStandardReferenceModelforTelerobotControlSystemArchitectureNISTNationalInstituteofStandardsandTechnologyPARPhaseAngleRegulatorSOFLICSelfOrganizingFuzzyLogicControlUPFCUniedPowerFlowControllerviiviiiContentsAbstractiiiAcknowledgmentsvAcronymsv1Introduction31.1ControlofActivePowerFlowMotivation........31.2ScopeandOrganizationofthisThesis...........51.3ContributionsofthisThesis.................62MultivariableControlStrategies92.1ShortTaxonomyofAvailableControlMethods......102.1.1ControlMethodsBasedonPhysioMathematicalMod-eling..........................102.1.2ControlMethodsBasedonExperientialEvidence.132.2ControlArchitecture.....................152.3ControlMethodsfortheDierentLevelsoftheArchitecture192.4ControllersinElectricPowerSystems:SpecialConsidera-tions..............................19ixxContents3ToolsforControlofActivePowerFlow233.1ControlledSeriesCapacitor,CSC..............243.2PhaseAngleRegulator,PAR................253.3UniedPowerFlowController,UPFC...........273.4OtherFACTSDevices....................294LoadFlowControlUsingCSCandPAR314.1TwoSeriesCapacitors....................314.1.1TheSimpleTestSystem...............324.1.2ControlwithIndependentIntegralControllers...334.1.3MathematicalAnalysisoftheControlledSystem.334.1.4SimulationoftheSimpleT