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1、810IEEETransactionsonEnergyConversion,Vol.14,No.3,September1999ANALYSISANDPERFORMANCEASSESSMENTOFTHEACTIVEFREQUENCYDRIFTMETHODOFISLANDINGPREVENTIONM.E.Ropp,M.Begovic,A.RohatgiSchoolofElectricalandComputerEngineeringGeorgiaInstituteofTechnologyAtlanta,CA30332-0250Abstract:Islandingofphotovoltaic
2、(PV)systemscancauseaConsiderthesystemshowninFigure1,whichincludesavarietyofproblemsandmustbeprevented.However,iftherealPVsystem,alocalload(wehaveusedaparallelRLCcircuitandreactivepowersoftheloadandPVsystemarecloselymatched,asasimplifiedversionofthedynamicloadmodelssuggestedislandingdetectionbyp
3、assivemethodsbecomesdifficult.Also,in[SI),aswitch(recloser,circuitbreaker,fuse,etc.),andthemostactivemethodsloseeffectivenesswhenthereareseveralPVutilityvoltagesource.Equations(1)and(2)describetherealsystemsfeedingthesameisland.Theactivefrequencydriftmethod(AFD),alsocalledthefrequencybiasmethod
4、,enablesislandingandreactivepowerbeingconsumedbytheRLCload.detectionbyforcingthefrequencyofthevoltageintheislandtoEquation(1)showsthatiftherealpowerproductionofthedriftupordown.Inthispaper,AFDisstudiedanalytically,usingPVsystemandtherealpowerdemandoftheloadarenotthedescribingfunctionanalysistec
5、hnique,andbysimulation,usingmatchedatthetimewhentheswitchisopened,thentheRMSMATLAB.ItisshownthatAFDhasanondetectionzone(NDZ)involtageatnodeainFigure1,V*,mustincreaseordecreasewhichitfailstodetectislanding,andthatthisNDZincludesarangeuntilPlaad=P,,(assumingRtobeconstantoverthetimeofunity-power-f
6、actorloads.Finally,thepaperdescribesanovelintervalofinterest).methodusingpositivefeedbackwhichsignificantlyshrinksthesizeoftheAFDNDZ.Keywords:islanding,grid-connectedPVsystems,activefrequencydrift,inverterprotection.I.INTRODUCTIONSimilarly,ifthereactivepowerproductionofthePVIslandingofagrid-con
7、nectedindependentgeneratorsuchsystemandthereactivedemandoftheloadarenotmatched,asaphotovoltaic(PV)system,occurswhenasectionofathenwhentheutilityisdisconnectedEquation(2)indicatesutilitysystemcontainingsuchgeneratorsisdisconnectedt
