Hybrid-compensation-arrangement-in-dispersed-gener

IEEETRANSACTIONSONPOWERDELIVERY,VOL.20,NO.2,APRIL20051719HybridCompensationArrangementinDispersedGenerationSystemsZheChen,SeniorMember,IEEE,FredeBlaabjerg,Fellow,IEEE,andJohnK.Pedersen,SeniorMember,IEEEAbstract—Thispaperpresentsahybridcompensationsystemconsistingofanactivefilteranddistributedpassivefilters.Inthesystem,eachindividualpassivefilterisconnectedtoadistortionsourceanddesignedtoeliminatemainharmonicsandsupplyre-activepowerforthedistortionsource,whiletheactivefilterisre-sponsibleforthecorrectionofthesystemunbalanceandthecan-cellationoftheremainingharmonics.Thepaperalsoanalyzestheeffectsofthecircuitconfigurationonthesystemimpedancecharacteristicsandconsequentlytheeffec-tivenessofthefiltersystem.Simulationstudiesareperformedforapowersystemincludingthedispersedgenerationunitsconnectedintothesystemthroughpowerelectronicconvertersanddioderec-tifierloads,whichproducethedistortedwaveforms.Thesimula-tionresultshavedemonstratedthatgoodcompensationeffectscanbeachievedbyusingthecombinedfiltersystemconsistingofdis-tributedpassivefiltersandanactivefilter.IndexTerms—Activefilter,dispersedgeneration,distributedpassivefilters,hybridcompensation,impedancecharacteristics.I.INTRODUCTIONANelectricalsystemoftensuppliesconsumerswithvar-ioustypesofloads,includingnonlinearloads,suchassingle-phaseand/orthree-phasethyristorconverters,dioderec-tifiersanduninterruptiblepowersupplies.Thesenonlinearloadsmayproduceharmonicsandsystemunbalanceandmayalsoconsumereactivepower.Thepowerqualityofacsystemscanbedeteriorated,ifapropercompensationisnotinplace.Thesituationbecomesmoreseriouswiththedevelopmentofthedispersedgeneration(DG)wherepowerelectroniccon-vertersareoftenusedtointerfacethegenerationunits,suchaswindturbinesandfuelcellsetc.Thepowerelectronicinterfacesmaygenerateharmonicsandrequirereactivepower(e.g.,SCRconverters).Alsothetypesandlevelsofthedistortionsmayvarywiththeoperationconditionsofthedispersedgenerationunitsandtheloads;therefore,aneffectivecompensationsystemisre-quiredtomaintainthepowerquality.Passivefiltershavethefeaturesoflowcostandgoodeffi-ciencyandhavebeenwidelyusedtoabsorbharmoniccurrentofnonlinearloads.Theycanalsoprovidereactivepowertoimprovethepowerfactor.However,passivefilterssuffersomedrawbacks,suchasstrongdependenceonsystemimpedance,susceptibletosourceandloadresonanceandthecharacteristicManuscriptreceivedOctober22,2003.Paperno.TPWRD-00531-2003.Z.CheniswiththeInstituteofEnergyTechnology,AalborgUniversity,Aal-borgDK-9220,Denmark(e-mail:[e-mail]),onleavefromDeMontfortUniversity,LeicesterLE19BH,U.K.(e-mail:[e-mail]).F.BlaabjergandJ.K.PedersenarewiththeInstituteofEnergyTechnology,AalborgUniversity,AalborgDK-9220,Denmark(e-mail:[e-mail];[e-mail]).DigitalObjectIdentifier10.1109/TPWRD.2004.834349variationduetoaging.Alsopassivefiltersareoftendesignedwithfixedparameters,whichcannotbeeasilyadaptedforthevaryingoperationconditionsandaredifficulttocorrectthesystemunbalance.Activepowerfilters[1],includingseriesandshuntactivefil-ters,havebeendevelopedtocompensatethedrawbacksofpas-sivefilters.Activefiltersareflexibleandcanprovideexcellentcompensationforvoltageandcurrentdistortions,butarenotacost-effectivesolutionyetduetothehighconstructionandop-erationcosts.Consequently,hybridfiltertopologies,suchasthecombinationofseriesactiveandparallelpassivefilters[2]andactivefilterinserieswithparallelpassivefilters[3]–[5]havebeendevelopedtocombinetheadvantagesofpassivefiltersandactivefiltersforcosteffectivecompensation.Theparallelconnectionofpassivefilterswithanactivefilterhasbeendiscussedpreviously[6],[7],whereonepassivefilterandoneactivefilterareconnectedinparallel,thearrangementhasshowntheeffectivenesstodealwiththedistortionunderavaryingoperationcondition.Thispaperextendstheconceptintoasystemconsistingofagroupofdistributedpassivefiltersandoneactivefilter,whichcaneffectivelycompensatethedistortioninalocalnetwork,suchasalocalDGsystemorawindfarm.Thesystemconfigurationwillbepresentedwithabriefde-scriptionoftheoperationofthefiltersystem,thenthefiltersaredescribed.Thevariationsoftheimpedancecharacteristicsduetothechangeofthesystemconfiguration,i.e.,theconnectionoftheshuntpassivefiltersandloads/dispersedgenerationunits,aretobepresented.Furthermore,simulationstudiesarepresented,analyzedanddiscussed.II.SYSTEMCONFIGURATIONTheconfigurationofthestudiedsystemisillustratedinFig.1,wherethepassivefiltersaredistributivelyconnectedneartheloads/dispersedgenerationunitsinthesystemandanactivefilterisconnectedatacentralconnectionpoint,forexample,asubstation.Eachpassivefiltermaybedesignedaccordingtothedistortioncharacteristicsoftheload/dispersedgenerationunitthatthepassivefilterisconnectedto,andtheactivefilterisinparallelwiththepassivefiltersandloads/dispersedgenerationunits.Inoperation,thepassivefilterscompensateforthemajorhar-monicsatapositionneartheloadorgenerationunit.Therefore,theharmonicflowislimitedandtheharmonicimpact,suchasinterferencetocommunicationsandincreaseinpowerloss,aretobeeffectivelyreduced.Theactivefilterislocatedattheupstreampositiontore-movetheremainingharmonicsandco