A Novel Active Power Filter for

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IEEETRANSACTIONSONPOWERDELIVERY,VOL.20,NO.2,APRIL20051507ANovelActivePowerFilterforHarmonicSuppressionHurng-LiahngJou,Member,IEEE,Jinn-ChangWu,Yao-JenChang,andYa-TsungFengAbstract—Inthispaper,anovelactivepowerfilterisproposedAmongthoselistedabove,theseries/parallelresonanceistheandimplementedbyusingavoltage-sourcepowerconverterwithmostseriousdisadvantage.Itmayresultinover-current/over-aseriesconnectedinductorandcapacitorset.Thepowerconvertervoltageontheinductorandcapacitorcausingdamagetothepas-iscontrolledtogenerateacompensatingvoltagethatisconvertedsivepowerfilter.Sincethesystemimpedancehasasignificantintoacompensatingcurrentviatheseriesconnectedinductorandcapacitorset.Thecompensatingcurrentflowsintothepowereffectontheperformanceofpassivepowerfilter,itisveryhardfeederinordertosuppresstheharmoniccurrentsgeneratedbytoobtainanexcellentfilterperformanceinpracticalapplica-nonlinearloads.Thesalientadvantagesoftheproposedactivetions.Moreover,theharmoniccurrentproducedbyneighboringpowerfilterarelowervoltageratingofdccapacitorandpowernonlinearloadsmayflowintothepassivepowerfilterandresultswitchingdevices,smallerfilterinductor,smallerdimension,intheoverloadofthepassivepowerfilter.lightweight,betterfilterperformanceandlowelectromagneticinterference(EMI).Athree-phase100kVAactivepowerfilterRecently,theharmonicsuppressionfacilitiesbasedonpowerisdevelopedtodemonstratetheperformanceoftheproposedelectronictechniquehavebeendeveloped.Theseactivehar-method.Theresultsshowthattheproposedactivepowerfilterhasmonicsuppressionfacilitiesknownasactivepowerfiltercantheexpectedperformance.suppressthedifferentorderharmoniccomponentsofnonlinearIndexTerms—Activepowerfilter,harmonic.loadssimultaneously[3]–[14].Accordingtothepowercircuitconfigurationsandconnections,theactivepowerfiltercanbedividedintoparallelactivefilters,seriesactivefiltersandotherI.INTRODUCTIONfiltercombinations[13].Theparallelactivepowerfilteriscon-HEpowerelectronicrelatedfacilitiesmaygeneratealargenectedinparalleltotheloadandthegeneratedcompensationTamountofharmoniccurrentduetothenonlinearinputcurrentopposestotheloadharmoniccurrenttobeinginjectedcharacteristic.Theharmoniccurrentmaypollutethepowerintothepowerfeeder.Theparallelactivepowerfilterhasmanysystemcausingproblemssuchastransformeroverheating,configurations[13].Amongtheseconfigurations,thestandardrotarymachinevibration,voltagequalitydegradation,destruc-invertertypeiswidelyusedanddiscussed[3]–[9].Fig.1(a)tionofelectricpowercomponents,andmalfunctioningofshowsthesystemconfigurationofthestandardinvertertypemedicalfacilities[1].Inordertosolvetheproblemofharmonicparallelactivepowerfilter(conventionalparallelactivepowerpollutioneffectively,manyharmoniclimitationstandards,suchfilter).Theconventionalparallelactivepowerfiltercanper-asIEEE519-1992,IEC1000-3-2,andIEC1000-3-4,havebeenformtheharmoniccurrentsuppression,reactivepowercompen-established.sationandbalancingthree-phasecurrents.ThisfilterconsistsTheharmoniccurrentcanbesuppressedbyusingapassiveofavoltage-sourcepowerconverterandafilterinductorcon-oractivepowerfilter.Conventionally,thepassivepowerfilternectedinseries.Theroleofthefilterinductorisusedtosuppressisusedtosolvetheproblemsofharmonicpollutioninthein-thehighfrequencyripplecurrentgeneratedwhileswitchingthedustrialpowersystemduetoitslowcost.However,ithasthepowerelectronicdevicesofthepowerconverter.Theinduc-followingdisadvantages[2]:tanceofthefilterinductordependsonswitchingfrequency,dc1)sensitivetothevariationofpowersystemimpedance;voltage,andripplecurrentlimitation.Thedcbusvoltagemust2)sensitivetofrequencyvariationoftheutility;behigherthanthepeakvalueoftheutilityvoltagetoforcethe3)theriskofseries/parallelresonance;outputcurrentoftheactivepowerfilterunderthecommandof4)thefilterfrequencyisfixed,andnoteasytoadjust.compensatingcurrentintheconventionalparallelactivepowerfilter.Theuseofhighdcbusvoltagehasmanydisadvantagessuchaslargefilterinductance,andhighvoltageratingofdccapacitorandpowerelectronicdevices.AlargerfilterinductorManuscriptreceivedApril21,2003;revisedFebruary15,2004.Thisworkwillresultinsignificantpowerloss,moreheatdissipation,bulkwassupportedbytheUISAblerCorporation,Ltd.Paperno.TPWRD-00183-2003.dimensionandweight,anddegradestheperformanceoffre-H.-L.JouiswiththeDepartmentofElectricalEngineering,NationlKaoh-quencyresponse.TherequirementofhighvoltageratingofdcsiungUniversityofAppliedSciences,Kaohsiung807,Taiwan,R.O.C.(e-mail:capacitorandpowerelectronicdeviceslimitshighpowerappli-hljou@mail.e.kuas.edu.tw).J.-C.WuiswiththeDepartmentofElectricalEngineering,KuncationofactivepowerfiltersduetothehighpowerratingoftheShanUniversityofTechnology,Tainan710,Taiwan,R.O.C.(e-mail:powerconverterandcost.jinnwu@mail.ksut.edu.tw).Fig.1(b)showsthesystemconfigurationoftheseriesactiveY.-J.ChangandY.-T.FengarewiththeUISAblerCorporation,Ltd.,Kaoh-siung807,Taiwan,R.O.C.filter.ThemajoradvantagesoftheseriesactivefilterovertheDigitalObjectIdentifier10.1109/TPWRD.2004.841305parallelactivepowerfilterarethatitcanmaintaintheoutput0885-8977/$20.00©2005IEEE 1508IEEETRANSACTIONSONPOWERDELIVERY,VOL.20,NO.2,APRIL2005Fig.1.Systemconfigurationofactivepowerfilter,(a)standardinvertertypeparallelactivepowerfilter,(b)seriesactivepowerfilter,(c)hybridpowerfilter.voltagewaveformtobesinusoidalandbalancethethree-phasevoltages.However,theseriesfilterislesspopularintheindus-trialapplicationsduetotheinherentdrawbacksofseriescir-Fig.2.Systemconfigurationofproposedactivepowerfilter.cuits,namelyitmusthandlehighloadcurrents,whichincreasestheircurrentratingcomparedwiththeparallelactivepowerfil-ters[13].Insomeapplications,thecombinationsofseveraltypesoffilterscanachievegreaterbenefits.Themajorcombinationsin-cludeparallelactivefilterandseriesactivefilter,seriesactivefilterandparallelpassivefilter,parallelactivefilterandpar-allelpassivefilter,andactivefilterinserieswithparallelpassiveFig.3.Equivalentcircuitofproposedactivepowerfilter.powerfilter[13].Amongtheseconfigurations,theactivefilterinserieswithparallelpassivefilter,alsoknownasthehybridpowercapacitorset,apowerconverterandahighfrequencyripplefilter,ismorewidelydiscussedintheliterature[10]–[14].Thisfilter.Thevoltage-modecontrolisusedtocontrolthepowerconfigurationisshowninFig.1(c)wherethepassivefilterfil-converter.Thepowerconvertergeneratesacompensatingtersthedominantharmonic,andthepowerconverterisusedtovoltagethatisconvertedintoacompensatingcurrentflowingenhancethefilterperformanceandtoprotectthepassivefilterthroughtheseriesconnectedinductorandcapacitorset,andfrompowerresonance.Hence,thecapacityofthepowercon-thecompensatingcurrentflowsintothepowerfeederinorderverterissmallerthanthatoftheparallelactivepowerfilterfortofilterharmoniccurrentsgeneratedbynonlinearloads.Thethesamenonlinearload.Besides,thevoltagestressappliedtoconfigurationoftheproposedactivepowerfilterissimilartothepowerelectronicswitchesinthepowerconverterislow.Asthatofthehybridpowerfilterinthefirstview.However,thearesult,thehybridfilterissuitabletohigh-powerapplications.functionanddimensionofthepassiveelements(L-C)arenotHowever,thehybridpowerfilterrequiresabulkpassivepowerthesame.Intheproposedmethod,theinductoroftheseriesfiltersetandavoltage-matchingtransformer.connectedinductorandcapacitorsetisverysmall,anditisBasedonthetypeofcompensation,theactivepowerfiltercanusedtofiltertheswitchingrippleofthepowerconverter.Thebedividedintoreactivepowercompensation,harmoniccom-capacitorintheseriesconnectedinductorandcapacitorsetispensation,balancingofthree-phasesystemsandmultiplecom-usedtosupplyafixedreactivepower.However,thepassivepensations[13].Theconventionalparallelactivepowerfilterelements(L-C)inthehybridpowerfilterareusedtotunebelongstomultiplecompensations,anditcancompensateforthedominantharmoniccomponentoftheloadcurrent.Thetheharmoniccurrentandreactivepowersimultaneously[3]–[9].inductanceinthehybridpowerfilterislargerthanthatusedThehybridpowerfilterbelongstotheharmoniccompensation,intheproposedactivepowerfilter,then,thedimensionandanditonlycompensatesfortheharmoniccurrent[10]–[14].weightoftheinductorusedinthehybridpowerfilterarealsoInthispaper,anovelactivepowerfilterisproposed.largerthanthatusedintheproposedactivepowerfilter.TheTheproposedactivepowerfilterisimplementedbyusingahighfrequencyripplefilterisconfiguredbyasetofcapacitorsvoltage-sourcepowerconverterwithaseriesconnectedin-andresistor,anditusestofurtherfilterouttheswitchingrippleductorandcapacitorset.Theproposedactivepowerfiltercanofthepowerconverter.beregardedasanewfamilyofthehybridpowerfilter,combingFig.3showstheequivalentcircuitoftheproposedactiveaparallelactivefilterandanacpowercapacitor.Theproposedpowerfilter.Itconsistsoftwovoltagesources,oneistheutilityactivepowerfilterhastheadvantagesoflowervoltageratingandtheotheristhepowerconverter.Thecompensatingvoltageofdccapacitorandpowerswitchingdevices,smallerfiltergeneratedbythepowerconverterisadependentvoltagesourceinductor,smallerdimension,lightweight,betterfilterperfor-whosevoltagedependsontheharmoniccomponentsoftheloadmanceandlowEMI.Finally,athree-phase100kVAprototypecurrent.TheequivalentcircuitshowninFig.3canbefurtherisdevelopedtodemonstratetheperformanceoftheproposeddividedintothefundamentalfrequencyequivalentcircuitandactivepowerfilter.theharmonicfrequencyequivalentcircuitasshowninFig.4.Fig.4(a)showstheequivalentcircuitunderthefundamentalfre-II.SYSTEMCONFIGURATIONANDOPERATIONPRINCIPLEquency.Ifthepowerlossisnegligible,thecompensatingvoltageThesystemconfigurationoftheproposedactivepowerfiltergeneratedbythepowerconverteronlycontainsharmoniccom-isshowninFig.2.Itconsistsofaseriesconnectedinductorandponents.Hence,thevoltagesourceofthepowerconvertercan JOUetal.:NOVELACTIVEPOWERFILTERFORHARMONICSUPPRESSION1509thevoltageratingofdccapacitorandpowerelectronicdevicescanalsobereduced.Besides,theripplecurrentofthepowerconverterisdependentonthedcbusvoltageandfilterinduc-tance.Thisimpliesthatthelowerthedcbusvoltage,thesmallerfilterinductancerequiredforspecifiedripplecurrentlimitation.Therefore,thefilterinductanceusedintheseriesconnectedFig.4.Equivalentcircuitofproposedactivepowerfilter,(a)fundamentalfrequencyequivalentcircuit,(b)harmonicequivalentcircuit.inductorandcapacitorsetissmallerduetothelowerdcbusvoltage.Besides,thehighfrequencyresponseoftheproposedactivepowerfilterisbetterthanthatoftheconventionalparallelberegardedasashortcircuitunderthefundamentalfrequency.activepowerfilterduetothesmallerfilterinductance.Also,itisevidentthattheimpedanceoftheseriesconnectedComparedtotheconventionalparallelactivepowerfilter,itinductorandcapacitorsetiscapacitiveunderthefundamentalshowsthattheproposedactivepowerfilterusesthreeadditionalfrequency.Hence,theseriesconnectedinductorandcapacitoraccapacitorstoreducetheinductanceoffilterinductor.Inprac-setperformsthefixedreactivepowercompensation.Sincethetice,thecoreofaninductorwithlargeinductanceismadefrominductanceoftheseriesconnectedinductorandcapacitorsetistheironalloy,whichresultsinthebulkyvolume,heavyweightverysmallintheproposedactivepowerfilter,thecompensatingandlargeloss.Thecoreofaninductorwithsmallinductancereactivepowercanbeapproximatedascanbemadefromtheferritematerials,whichhavethecharac-teristicsofsmallvolume,lightweightandloweddycurrentloss(1)[15].TheEMI,generatedbytheswitchingofpowerconverter,isalsodependentonthedcbusvoltage.Therefore,thesalientwhereisthecapacitanceoftheseriesconnectedinductorandadvantagesoftheproposedactivepowerfilterarelowvoltagecapacitorset,andistheRMSvalueoftheutilitylineratingofdccapacitorandpowerswitchingdevices,smallerfiltervoltage.inductance,smallerdimension,lightweight,goodfilterperfor-Fig.4(b)showstheequivalentcircuitunderharmonicfre-manceandlowEMI.Besides,thesmallerfilterinductancecanquency.Ifthefrequencyislowerthanthetunedfrequency,theimprovethehighfrequencyresponseperformanceofthisac-seriesconnectedinductorandcapacitorsetiscapacitive.Ontivepowerfilter.Since,thecapacityofthedcbusvoltageisthecontrary,theseriesconnectedinductorandcapacitorsetisdependentontheamountofcompensationcurrentandnottheinductiveifthefrequencyishigherthanthetunedfrequency.utilityvoltage,theapplicationoftheproposedactivepowerfilterTheswitchingfrequencyofthepowerconverterissignificantlycouldbeextendedtoawidervoltagerange.Inthelimitedvari-higherthanthetunedfrequencyoftheseriesconnectedinductorablevoltageapplication,suchas220Vto480V,thechangeinandcapacitorset.Asaresult,theseriesconnectedinductorandthemaincomponentsisonlythevoltageratingofseriescon-capacitorsetactsasaninductortofiltertheswitchingfrequencynectedinductorandcapacitorset.Inaddition,theproposedac-ofthepowerconverter.Forsuppressingtheloadharmoniccur-tivepowerfiltercanbeappliedinHzpowersystemsonlyrent,thedesiredcompensatingvoltagecanbederivedasadjustingtheparametersofthecontrolcircuit.Fortheconven-tionalactivepowerfilter,thevoltageratingofbothactiveand(2)passivecomponentsmustbechanged.Thehardwarecostoftheproposedactivepowerfilterisverycompetitiveinthenonlinearwhereistheharmoniccomponentoftheloadcurrent,loadswhoseinputisadiode-rectifierorphase-controlledrec-istheimpedanceoftheseriesconnectedinductorandcapac-tifierwithalowlevelvoltagebelow480V.Theconventionalitorset.Ifthepowerconvertercangenerateavoltageasshownparallelactivepowerfiltercansupplythereactivepowerasthein(2),thenthisvoltageisconvertedintoacompensatingcur-variationoftheload,andperformstheunitypowerfactorcom-rentthatisoppositetotheloadharmoniccurrent.Hence,thepensation.Nevertheless,thehybridactivepoweronlysuppliesloadharmoniccurrentcanbesuppressed.AsshowninFig.4(a),afixedreactivepower.Thisresultsintheleadingpowerfactor,thefundamentalcomponentofutilityvoltagedropsonthese-astheloadconditionislight.Thereactivepowercompensationriesconnectedinductorandcapacitorset,hence,thecompen-performanceoftheproposedactivepowerfilterissimilartothesatingvoltagegeneratedbythepowerconverterconsistsonlyhybridpowerfiltersupplyingafixedreactivepower.theharmoniccomponents.Inaddition,(2)showsthatthede-siredcompensationvoltageisdependentontheloadharmoniccurrentandtheimpedanceoftheseriesconnectedinductorandIII.CONTROLTHEORYcapacitorset.Thisvalueissmallerthanthepeakvalueoftheutilityvoltage.FromtheoperationtheoryofthebridgepowerConventionally,theactivepowerfilterwascontrolledbytheconverter,thedcbusvoltageofapowerconvertermustbehighercurrent-mode.However,itishardtobeimplementedunderthanthepeakvalueofthecompensatingvoltage.Becausethelowfilterinductanceduetothehighswitchingripple,andpeakvalueofcompensatingvoltageissmallerthanthatoftheitmaygeneratemultiplecrossingduringacarrierperiodofutilityvoltage,thedcbusvoltageintheproposedactivepowerpulse-widthmodulator.Thephenomenonofmultiplecrossingfiltercanbereducedsignificantlyascomparedwiththecon-willresultinmorethanoneswitchingoperationduringacarrierventionalparallelactivepowerfilterwhosevoltagemustbeperiod.Intheproposedactivepowerfilter,thevoltage-modehigherthanthepeakvalueoftheutilityvoltage.Consequently,controlisused.Thethree-phasepowerconvertercontrolledby 1510IEEETRANSACTIONSONPOWERDELIVERY,VOL.20,NO.2,APRIL2005thevoltage-modecontrolactsasavoltageamplifierwiththetogenerateavirtualharmonicresistortobeconnectedinseriesgainrepresentedbywiththeseriesconnectedinductorandcapacitorset.Thevirtualharmonicresistoractsasaharmonicdamper.Itcanberealized(3)byusingthepowerconvertertogenerateaharmonicvoltagethatisproportionaltotheharmoniccomponentsoftheactivewhereisthedcbusvoltageandistheamplitudeofthepowerfiltercurrent.Hence,thethirdcontrolsignalcanbecarriersignalofthepulse-widthmodulator.Hence,thecontrolrepresentedascircuitofthevoltage-modecontrollerisusedtodeterminea(7)referencevoltagebydividingthedesiredcompensatingvoltagebythegainshownin(3).whereisthecurrentharmoniccomponentoftheactiveFromtheabovesection,itcanbefoundthatthedesiredcom-powerfilter.Hence,thepowerconvertercanactasavirtualhar-pensatingvoltagegeneratedbythepowerconverterisderivedmonicresistor.from(2).Hence,thefirstcontrolsignalcanbefurtherde-Adccapacitorlocatedatthedcbusofthevoltage-sourcerivedfrom(2),anditisrepresentedaspowerconverterisusedtosupplyadcvoltagetothepowerconverterandactasanenergybuffer.Thedcbusvoltageisex-(4)pectedtobeaconstantvoltage.However,thevirtualharmonicresistorinthesecondandthirdcontrolloopsandtheswitchingwhereLandCaretheinductanceandcapacitanceoftheserieslossofpowerconverterwillconsumetherealpower.Then,theconnectedinductorandcapacitorsetrespectively,andRisthevoltagevariationatthedcbuscannotbeavoided.Tomaintainstraylossofactivepowerfilter.Ifthepowerconvertercangen-aconstantdcbusvoltage,thefourthcontrolloopisused.Theerateaharmonicvoltageequaltothefirstcontrolsignalvoltageregulationofthedcbusvoltagecanbeobtainedbyusingandconvertintoacompensatingcurrentbytheseriesconnectedthepowerconvertertogenerateafundamentalvoltageinphaseinductorandcapacitorset,theharmoniccomponentsoftheloadorout-of-phasewiththefundamentalcomponentoftheactivecurrentcanbecompensatedtheoretically.Inpractice,thefilterpowerfiltercurrent.Thefourthcontrolsignalcanberep-performanceisdegradedduetotheparametersoftheseriescon-resentedasnectedinductorandcapacitorsetthatmaybevariedduetoage,variablefrequency,productionandtemperature.Forimproving(8)thecompensatingperformance,thesecondcontrolloopmustbeusedtomodifytheerrorofcompensatingresult.Theconceptofwhereisthefundamentalcomponentoftheactivepowerthesecondcontrolloopisbasedonthetheoryofconventionalfiltercurrent.Then,thepowerconverteractsasapositive/neg-hybridpowerfilter[10]–[12].Thesecondcontrolsignalativefundamentalresistortoabsorb/regeneratetherealpowerisobtainedbydetectingtheharmoniccomponentsoftheutilityfrom/totheutility,soastomaintainthedcbusvoltageatacon-currentandthenamplifyingwithagain,anditcanberep-stantvalue.resentedasFromtheabove,thereferencevoltageofthecontrolcircuitisthesummationofthefirst,second,third,andfourth(5)controlsignals,anditcanberepresentedaswhereistheharmoniccomponentoftheutilitycurrent.If(9)thepowerconvertercangenerateavoltageequaltothesecondcontrolsignal,theutilityharmoniccurrentcanbederivedIn(9),thefirstcontrolsignalisthedominantcomponent.fromFig.4(b)andrepresentedasHence,thecompensatingvoltagegeneratedbythepowercon-verterisalmosttheproductoftheimpedanceoftheseriescon-nectedinductorandcapacitorsetandtheharmoniccomponents(6)ofloadcurrent.From(6),itcanbefoundthatatermisaddedtothede-IV.CONTROLBLOCKDIAGRAMnominatorwhenthepowerconvertergeneratesavoltageasthesecondcontrolsignal.Hence,thesecondcontrolloopisFig.5showsthecontrolblockdiagramoftheproposedactiveusedtocontrolthepowerconvertertoactasavirtualharmonicpowerfilter.Itconsistsoffourcontrolloops.FromFig.5,itcanresistor.Thevirtualharmonicresistorisinserieswithbefoundthatfourfeedbacksignals,namelytheloadcurrent,thetheutilitytoblocktheuncompensatedharmoniccomponentsofutilitycurrent,theoutputcurrentofpowerconverterandthedcloadcurrentflowingbacktotheutility[12].Intheproposedac-busvoltageareusedinthecontrolcircuitoftheproposedactivetivepowerfilter,thefirstcontrolloopactsasroughtuning,andpowerfiltertocalculatethereferencevoltageofthepowercon-thesecondcontrolloopisusedforfine-tuning.verter.ThefirstcontrolloopisusedtoimplementtheproductofDuetotheuseofvoltage-modecontrolintheproposedactiveharmoniccomponentsoftheloadcurrentandtheimpedanceofpowerfilter,theseriesconnectedinductorandcapacitorsetmaytheseriesconnectedinductorandcapacitorsetshownin(3).Theresultinhighfrequencyoscillationbetweentheutilityandtheloadcurrentisdetectedandsenttotheband-rejectionfilterItoactivepowerfilters.Hence,thethirdcontrolloopisappliedtofilteroutitsfundamentalcomponent.From(3),itcanbefoundavoidhighfrequencyoscillation.Thethirdcontrolloopisusedthattheproductofharmoniccomponentsoftheloadcurrent JOUetal.:NOVELACTIVEPOWERFILTERFORHARMONICSUPPRESSION1511TABLEIMAJORPARAMETERSOFPROTOTYPETABLEIICOMPARISONRESULTSFig.5.Controlblockdiagramofproposedactivepowerfilter.andtheimpedanceoftheseriesconnectedinductorandcapac-itorsetcanbeobtainedbyfeedingtheharmoniccomponentofloadcurrenttoaProportionalIntegralDifferential(PID)con-troller.Theproportional,integralanddifferentialcoefficientsaretheresistorR,capacitorCandinductorLshownin(3),re-spectively.Then,theoutputofthefirstcontrolloopisobtained.Foravoidingtheeffectofnoise,alow-passfilterisusedinthefrontofDifferentialcontrollerandahigh-passfilterisinsertedattheendofIntegralcontrollertorejectthedccomponentduetotheinitialcondition.Since,theseriesconnectedinductorandcapacitorsetislocatedattheoutputofthepowerconverter,thecapacitoralsocanblockthedccomponentduetotheinitialcon-dition.Hence,theeffectoftheinitialconditioncausedbytheswitch-onoftheproposedactivepowerfiltercanbesuppressed.Forimprovingthecompensatingperformance,thesecondcontrolloopisusedtomodifytheerrorofthecompensatingresultsofthefirstcontrolloop.Inthesecondcontrolloop,thedetectedutilitycurrentissenttotheband-rejectionfilterIItofilteroutthefundamentalcomponent.Then,theuncompensatedFig.6.Experimentalresultofproposedactivepowerfilterundersteadystate,harmoniccomponentsoftheutilitycurrentareobtained.The(a)utilityvoltage,(b)utilitycurrent,(c)loadcurrent,and(d)outputcurrentofactivepowerfilter.outputoftheband-rejectionfilterIIisfedtotheamplifierItoobtaintheoutputofthesecondcontrolloop.V.EXPERIMENTALRESULTSThethirdcontrolloopisusedtogenerateavirtualharmonicresistortobeconnectedinserieswiththeseriesconnectedin-Fordemonstratingtheperformanceoftheproposedactiveductorandcapacitorsettoactasadamper.Theoutputcurrentpowerfilter,athree-phase100kVAprototypeisdeveloped.ofthepowerconverterissenttoaband-passfiltertoobtaintheThemajorparametersoftheprototypeareshowninTableI.fundamentalcomponent,andthen,thedetectedoutputcurrentTheutilitypowerissuppliedbyathree-phasethree-wireutilityofthepowerconverteranditsfundamentalcomponentarefedtosystemwith380Vand60Hz.Acomparisonoftheproposedasubtractortoobtaintheharmoniccomponents.TheharmonicactivepowerfilterandtheconventionalparallelactivepowercomponentsarefedtoamplifierIItoobtaintheoutputofthefilterisshowninTableII.Sincetheinductanceofseriesthirdcontrolloop.connectedinductorandcapacitorsetisonly58H,aferriteThefourthcontrolloopisusedtoregulatethedcbusvoltage.corecanbeusedtoreducethepowerloss,weightandvolume.Thefourthcontrolloopcomprisesalow-passfiltertofilteroutHence,thevolumeandweightoftheproposedactivepowerthedcbusvoltagerippleandasubtractortosubtractasettingfilterisevidentlysmallerthanthatoftheconventionalparallelvaluefromtheoutputoflow-passfilter,then,thesubtractorre-activepowerfilter.Inaddition,thehardwarecostisalsoreducedsultissenttoaPIcontroller.Theoutputoftheband-passfiltersignificantly.Thetestedloadisa300kVAUPSwithasix-pulseisthefundamentalcomponentofactivepowerfiltercurrent,andrectifiercharger.theoutputofthefourthcontrolloopistheproductoftheoutputFig.6showstheexperimentalresultoftheproposedactiveofthePIcontrollerandtheoutputoftheband-passfilter.powerfilterinthesteadystate.TheloadcurrentshowninFinally,themodulatedsignalcanbeobtainedbysummingtheFig.6(c)isrichinharmonics;itstotalharmonicdistortionoutputsofthefirst,thesecond,thethirdandthefourthcontrol(THD)is51%.However,theTHDoftheutilitycurrentafterloops.Then,themodulatedsignalissenttoapulse-widthmod-compensatingbytheproposedactivepowerfilterisonly4.5%.ulatorsoastodrivethepowerswitchingdevicesofthepowerThewaveformoftheutilitycurrentaftercompensatingbyconverter.theproposedactivepowerfilterisnearlysinusoidal.Thetest 1512IEEETRANSACTIONSONPOWERDELIVERY,VOL.20,NO.2,APRIL2005Fig.7.Experimentalresultofproposedactivepowerfilterundertransientofapplyingnonlinearload,(a)utilityvoltage,(b)utilitycurrent,(c)loadcurrent,Fig.9.Experimentalresultunderweakpowersourceafterapplyingactiveand(d)outputcurrentofactivepowerfilter.powerfilter.filter.TheTHD%oftheturbinegenerator’svoltageandcur-rentare4%and4.5%,respectively.Hence,thiscandemonstratethattheproposedactivepowerfilternotonlycansuppresstheinputcurrentharmonicsbutalsoavoidthewaveformdistortionofthevoltageundernonlinearloads.Theaboveexperimentalresultsdemonstratethattheproposedactivepowerfilterhastheexpectedperformance.VI.CONCLUSIONRecently,manypowerelectronicapplicationtechnologieshavebeenusedtoreplacetheroleofconventionalpassiveele-mentsinthedistributionpowersystemforsolvingtheproblemsofpowerquality.TheactivepowerfilterisusedtosolvetheFig.8.Experimentalresultunderweakpowersourcebeforeapplyingactiveharmonicproblemsintheindustrialpowersystem,andthispowerfilter.becomespopulargradually.However,thewideuseoftheactivepowerfilterisstilllimitedduetothehighcostandthepowerresultshowsthattheharmonicsuppressionperformanceofratingofpowerelectronics.theproposedactivepowerfilterisexcellent.Fig.7showstheInthispaper,anovelactivepowerfilterisproposed.Thepro-experimentalresultoftheproposedactivepowerfilterunderposedactivepowerfilterhastheadvantagesoflowervoltageswitching-inthenonlinearload.AsseeninFig.7(b),theutilityratingfordccapacitorandpowerswitchingdevices,smallercurrentisstillnearlysinusoidalunderthetransientduration.Itfilterinductor,smallerdimension,lightweight,betterfilterper-verifiesthatthetransientperformanceoftheproposedactiveformanceandlowelectromagneticinterference(EMI).Athree-powerfilterisexcellent.phase100kVAactivepowerfilterisdevelopedtodemonstrateIntheindustrialdistributionpowersystem,aturbinegener-theperformanceoftheproposedmethod.Theexperimentalre-atorisoftenusedasaback-uppower.Becausethecapacityofsultsshowthattheproposedactivepowerfilterhasexcellenttheturbinegeneratorisnotlargeenough,thepowersourceofperformanceinsuppressingharmoniccurrent.Thehardwaretheturbinegeneratorcanberegardedasaweakpowersource.costoftheproposedactivepowerfilterisverycompetitiveinTheexperimentalresultsshowninFigs.8and9aretestedundernonlinearloadswhoseinputisadiode-rectifierorphase-con-theconditionofweakpowersource.Theweakpowersourceistrolledrectifierwithalowlevelvoltagebelow480V.suppliedbya800kVAturbinegenerator.Theloadusedinthetestisthepowerequipmentusingathree-phaserectifierintheREFERENCESinputport.AsseeninFig.8,thevoltagewaveformofthetur-[1]R.D.HendersonandP.J.Rose,“Harmonics:Theeffectsonpowerbinegeneratorisdistortedseriouslyduetothenonlinearload.qualityandtransformers,”IEEETrans.IndustrialApplications,pp.TheTHDoftheutilityvoltageandtheutilitycurrentare12%528–532,1994.[2]C.J.Wu,J.C.Chiang,S.S.Yen,C.J.Liao,J.S.Yang,andT.Y.and25%respectively.ThedistortedutilityvoltagemaydisturbGuo,“Investigationandmitigationofharmonicamplificationproblemsthenormaloperationofpowerequipmentitselfortheneigh-causedbysingle-tunedfilters,”IEEETrans.PowerDel.,pp.800–806,boringloadusingthesamepowersource.Fig.9showsthatboth1998.[3]S.J.Chiang,W.J.Ai,andF.J.Lin,“Paralleloperationofcapacity-waveformsofthevoltageandcurrentoftheturbinegeneratorlimitedthree-phasefour-wireactivepowerfilters,”Proc.Inst.Elect.Eng.arenearlysinusoidalafterapplyingtheproposedactivepowerElectricPowerApplications,vol.149,no.5,pp.329–336,2002. JOUetal.:NOVELACTIVEPOWERFILTERFORHARMONICSUPPRESSION1513[4]J.C.WuandH.L.Jou,“Asimplifiedcontrolmethodforsingle-phaseJinn-ChangWuwasborninTainan,Taiwan,activepowerfilter,”Proc.Inst.Elect.Eng.ElectricalPowerApplica-R.O.C.,in1968.HereceivedtheM.S.E.E.andtions,pp.219–224,1996.Ph.D.E.E.degreesfromNationalChengKung[5]H.Akagi,“Trendsinactivepowerlineconditioners,”IEEETrans.PowerUniversity,Tainan,in1992and2000.Electron.,vol.9,no.3,pp.263–268,1994.CurrentlyheisanAssociateProfessoratthe[6]A.Abellan,J.M.Benavent,andG.Garcera,“AnewcontrolmethodforDepartmentofElectricalEngineering,KunShanobtainingreferencecurrentsofshuntactivepowerfiltersinunbalancedUniversityofTechnology.Hisresearchinterestsareandnonsinusoidalconditions,”IEEEISIE’99,pp.831–836,1999.powerqualityandpowerelectronicapplications.[7]B.Singh,K.Al-Haddad,andA.Chandra,“Anewcontrolapproachtothree-phaseactivepowerfilterforharmonicsandreactivepowercom-pensation,”IEEETrans.PowerSyst.,vol.13,no.1,pp.133–138,1998.[8]J.C.WuandS.J.Huang,“Designandoperationsofcascadedactivepowerfiltersforthereductionofharmonicdistortioninapowersystem,”inProc.Inst.Elect.Eng.Gen.Transm.Distrib.,vol.146,1999,pp.193–199.[9]T.KawabataandY.Komatsu,“Characteristicsofthreephaseactivepowerfilterusingextensionpqtheory,”inIEEEISIE’97,1997,pp.302–307.[10]S.Bhattacharya,P.T.Cheng,andD.M.Divan,“HybridsolutionsforYao-JenChangwasborninPingtung,Taiwan,improvingpassivefilterperformanceinhighpowerapplications,”IEEER.O.C.,in1968.HegraduatedfromtheDepartmentTrans.Ind.Appl.,pp.732–747,1997.ofElectricalEngineering,NationalKaohsiungInsti-[11]H.FujitaandH.Akagi,“ApracticalapproachtoharmoniccompensationtuteofTechnology,Kaohsiung,Taiwan,in1988.inpowersystem,seriesconnectionofpassiveandactivefilters,”IEEEHehasmorethan15yearsexperienceindevel-Trans.Ind.Appl.,pp.1020–1025,1991.opingpowerelectronicdevicesincludingthestatic[12]J.Dixon,J.Espinoza,L.Moran,andD.Rivas,“AsimplecontrolschemeUPSandthepowerharmonicsfilter.HeisnowDi-forhybridactivepowerfilter,”inIEEEPESC,2000,pp.991–996.rectoroftheR&DDivisionofUISAblerElectronics[13]M.EI-Habrouk,M.K.Darwish,andP.Mehta,“Activepowerfilters:ACompany.review,”inProc.Inst.Elect.Eng.ElectricPowerApplications,vol.147,2000,pp.403–412.[14]M.Rastogi,N.Mohan,andA.A.Edris,“Hybrid-activefilteringofhar-moniccurrentsinpowersystems,”IEEETrans.PowerDel.,vol.10,no.4,pp.1994–2000,Oct.1995.[15]Mohan,Undeland,andRobbins,PowerElectronicsConverters,Appli-cationsandDesign,3rded.NY:Wiley,2003.MediaEnhanced.Hurng-LiahngJou(M’98)wasborninTaiwan,Ya-TsungFengwasborninTaichung,Taiwan,R.O.C.,in1959.HereceivedtheB.S.E.E.degreeR.O.C.,onJanuary6,1972.HereceivedtheB.S.fromChungYuanUniversity,Jonglih,Taiwan,indegreeinelectricalengineeringfromNational1982,andtheM.S.E.EandPh.D.E.E.degreesfromKaoshiungUniversityofAppliedSciencesin1999NationalChengKungUniversity,Tainan,Taiwan,inandtheM.S.degreeinelectricalfromNational1984and1991,respectively.ChiaoTungUniversityin2001.Currently,heisaProfessorintheDepartmentofHeworkedfortwoyearsattheR&DDivisionofElectricalEngineeringofNationalKaohsiungUni-theUISAblerElectronicsCompany.HisresearchversityofAppliedSciences,Kaohsiung,Taiwan.HisinterestsinpowerelectronicsincludeUPS,activeresearchinterestsincludepowerelectronicsapplica-powerfilters,anddigitalcontrollers.tionsandpowerqualityimprovementtechnique.