电力系统暂态分析.pptx

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1、Negative Side:Direct MethodIntroductionsDefinition:UsePowerSystemTransientCharacteristicsFunctionToDescribeOrAnalyzeThePowerSystemTransientStabilityFirstIntroducedInThe1950sThanksToAthayAndKakimotosWork,TheDirectMethodGotRapidDevelopment.ClassificationsClassical ModelDirect MethodComplex ModelEnergy

2、 Function MethodTSEFAcceleration MethodRVEPPSEFLyapnoy Function MethodPEBSIMEFEEACTSDLyapnoyFunctionMethod:DengDashangPotentialEnergyBoundarySurface(PEBS):JiangTengIndividualMachineEnergyFunction(IMEF):FangLueExtendedEqual-areaCriterion(EEAC):JingTianApplications:MuhammadHamidConclusion:HuangYupengA

3、n Analogy Of Rolling Ball ModelRolling ball model points1.Theareainsidetheballrepresentsthestabilityregionandtheoutsiderepresentstheinstabilityregion.2.Initiallytheballisrestingatthebottomofthebowl,thestateisreferredtoasstableequilibriumpoint(SEP).Whenkineticenergyisinjectedtotheball,theballwillroll

4、upinsidethesurfaceofthebowl.3.Thepointwheretheballwillstopisgovernedbytheamountofkineticenergyinitiallyinjected.Iftheballconvertsallitskineticenergyintopotentialenergybeforereachingtherim,thenitwillrollbackandeventuallysettledownatthestableequilibriumpointagain.4.Ifthekineticenergyishighenoughtocaus

5、etheballtogoovertherim,theballwillentertheregionofinstability.Application to power sysytem:ThebasisfortheapplicationoftheTEF(TransientEnergyFunction)methodtotheanalysisofpowersystemstabilityisconceptuallysimilartothatforaballrollinginabowl.Initiallythesystemisoperatingatastableequilibriumpoint.If a

6、fault occurs,theequilibriumisdisturbedandthesynchronousmachinesaccelerate.Thepowersystemgainskineticandpotentialenergyduringfault-onperiodandthesystemmovesawayfromtheSEP.After fault cleared,thekineticenergyisconvertedintopotentialenergyinthesamemannerastheballrollingupthepotentialenergysurface.Toavo

7、idinstability,thesystemmustbecapableofabsorbingthekineticenergyatatimewhentheforcesonthegeneratorstendtobringthemtowardnewequilibriumpositions.Thisdependsonthepotentialenergy-absorbingcapabilityofthepost-disturbancesystem.Foragivenpostdisturbancenetworkconfiguration,thereisamaximumorcritical amount

8、of transientenergythatthesystemcanabsorb.Consequently,assessmentoftransientstabilityrequires:(a)Functionsthatadequatelydescribethetransientenergyresponsibleforseparationofoneormoresynchronousmachinesfromtherestofthesystem(b)Anestimateofthecriticalenergyrequiredforthemachinestolosesynchronism.The ste

9、ps for Lyapunov function method:1)Defineenergyfunction;2)Determinecriticalenergy;3)Comparingtheenergyatfaultclearingandcriticalenergytojudgethesystemisstableornot.ThekeyofthedirectmethodforthetransientstabilityanalysisistoconstructLyapunovfunction,whichisthetransient energy function.Equation1divided

10、byequation2,andintegratinggives:12Definition Of The Transient Energy FunctionStability Region And Phase Plane DiagramIntheabovefigure,eachlotus（15）isanequalenergycurve.Thetotalenergyincreasesfrominsidertooutsider,untilthecorrespondingmaximumsealedcurvetounstableequilibriumpointandreachescriticalener

11、gy.Thiscurveiscalledpolarcircle,theinsideisstableregion.Thus,wegetcritical energyIf,thesystemisstable.,thesystemisunstable.IfIf,Itisacriticalcase.energyatfaultclearingtime:The Procedure Of Lyapunov Function MethodPotential Energy Boundary Surface(PEBS)ApproachPrincipleThecalculationoftheRUEPforlarge

12、systemisverytime-consuming.ThePEBSapproachwasdevelopedtoavoidthecalculationoftheRUEP.PEBSistheboundarydeterminedbythecurveswhichcrosseveryunstableequilibriumpointandisorthogonaltoeveryequipotentialsurfaces.StepsItcanbeillustratedbythefigurebelowWecanseeclearlythecrossingpointismuchmoreclosertoRUEPaf

13、tertwoiteration.AssessIndividual Machine Energy Function(单机能量法单机能量法)ReferenceFirstPresentedByMichelInHisThesis:powersystemtransientstabilityusingindividualmachineenergyfunction,IEEETrans.Oncircuitsandsystems,Vol.3,No.5,May1983,pp266276Two Problems:Significantportionsofthesystemtransientenergydonotco

14、ntributetosystemseparation;henceitshouldbecorrectedforintransientstabilityassessment.CriticalGroupOfMachinesNoncriticalGroupOfMachinesSystemseparationMachinesthattendtoseparatefromthesystemTherestmachinesSimulationsIndicate:IndividualMachineEnergyFunctionFormulationconvertStableconvertUnstableOveral

15、l system energy functionLessconservativestabilityresultswhenusingindividualmachineenergy.Extended Equal-area CriterionTimeDomainSimulationMethodDirectMethodsTransientenergyfunctionExtendedequal-areacriterionHybridmethodsAllYourWorksAreBasedOnMyTheory!LyapunovExtendedEqual-areaCriterionTransientenerg

16、yfunctionhavesometroubles.Redefinethestabilitymargin.Usingcomputertechnology,findtheintercrosswithSBS.DecoupletheobservespaceintoOneMachinetoInfiniteBus(OMIB).SEEACUsingtheclassicmulti-machinesystem.Verygoodresultsatsmallsystems.DEEACConsideringaboutThenoncoherentinsidethecomplementationgroups.Impro

17、vedtheaccuracyandrobustnessbasedonSEEAC.IEEACUsingSBStocomputethegeneratorsdynamictrajectory.Separatetheintegralspaceandtheobservespace.TransformTo map the two-machine system into the OMIB system,we further more do the RM transform:Where,Thus,we get the integral space and the observe space separeted

18、.AdvantagesoftheEEACTheuniquecriticalprovedmethod,andtheuniquequantitativeanalysismethod.Sensitivityanalysiscanhelpfortheestimationofthestablelimit.Earlyterminationoftheintegration.Supporthighspeedandhugeamountofinformation.Application Of Transient Energy FunctionThe surface inside the bowl represen

19、t the potential energy surface,and the rim of the bowl represents the potential energy boundry surface(PEBS)Two quantites are required to determine if the ball will enter the instability region.(a)The initial kinetic energy injected and(b)the height of the rim at the crossing point ROLLING BALL ANAL

20、OGY APPLICATION IN POWER SYSTEM TEF IS EQUIVALENT TO EQUAL AREA CRITERIA Showtwoplots,bothhavingarotorangleastheordinate.thelowerplotillusratethetransientenergymethodwhichcanbeusedtospecifyinTermsofpotentialandkineticenergy.RegionofstabilityanditslocalapproximationThekineticenergygainedduringthefaul

21、tonperiodisaddedtothepotentialenergyatthecorrespondingrotorangle,andthesumiscomparedtocriticalpotentialenergytodeterminestabilityThestateofthesystematfaultclaearingcanbedescribebythevalueoftheenergyfunctionevalutedathencethedirectmethodsolvesthestabilityproblembyComparingtoVcrcriticalenergyThisiscon

22、sistenttothedirectmethodDIRECT METHOD ANALYSIS OF A SINGLE MACHINE INFINITE BUS(SMIB)SYSTEM REFERENCESPower System Stability and Control:PrabhaKunduP.CMAGNUSSON,“TRANSIENTENERGYMETHODOFCALCULATINGSTABILITY”AIEEETrans,vol.66,pp747-755,1947Powersystemtransientsytabilityanalysisusingtransientenergyfunc

23、tionA.Afouad/vijayvittalThank you!ConclusionsProblems Of Numerical Integration Method:LongComputingTimeNotProvideStabilityQuantitativeIndexDifficultToOnlineCalculationAdvantages:SensitivityanalysisQuantitativeAnalysisOfTheDegreeOfStabilitySpeedSoftware:DIRECT,IPEBS,IC-PEBS,EEACRealTimeControlProspectOnline Dynamic Security AnalysisStability Control:PredictionOfGeneratorsOutOfSynchronismCuttingloadsystemOperation Planning:CheckrelayprotectionsettingtimeSystem Planning:CriticalenergycanreflectGridarchitecture Mix with Numerical Integration MethodThanks For Your Attention!