外文翻译原文-电池储能加强风力发电机在电力系统集成

JOURNALOFELECTRONICSCIENCEANDTECHNOLOGY,VOL.9,NO.1,MARCH201123AbstractThewindenergygeneration,utilizationanditsgridpenetrationinelectricalgridareincreasingworld-wide.Thewindgeneratedpowerisalwaysfluctuatingduetoitstimevaryingnatureandcausingstabilityproblem.Thisweakinterconnectionofwindgeneratingsourceintheelectricalnetworkaffectsthepowerqualityandreliability.Thelocalizedenergystoragesshallcompensatethefluctuatingpowerandsupporttostrengthenthewindgeneratorinthepowersystem.Inthispaper,itisproposedtocontrolthevoltagesourceinverter(VSI)incurrentcontrolmodewithenergystorage,thatis,batteriesacrossthedcbus.Thegeneratedwindpowercanbeextractedundervaryingwindspeedandstoredinthebatteries.Thisenergystoragemaintainsthestiffvoltageacrossthedcbusofthevoltagesourceinverter.Theproposedschemeenhancesthestabilityandreliabilityofthepowersystemandmaintainsunitypowerfactor.Itcanalsobeoperatedinstand-alonemodeinthepowersystem.Thepowerexchangeacrossthewindgenerationandtheloadunderdynamicsituationisfeasiblewhilemaintainingthepowerqualitynormsatthecommonpointofcoupling.Itstrengthenstheweakgridinthepowersystem.Thiscontrolstrategyisevaluatedonthetestsystemunderdynamicconditionbyusingsimulation.Theresultsareverifiedbycomparingtheperformanceofcontrollers.IndexTermsBatteryenergystorage,powerquality,windenergygeneratingsystem.1.IntroductionIntherecentyears,windenergygenerationhasbeenfocusedasacleanandinexhaustibleenergyanditspenetrationlevelhasincreasedthroughouttheworld.ThegrowthrateofrenewableinvestmentinthepowerManuscriptreceivedOctober18,2010;revisedFebruary18,2011.S.W.MohodiswiththeDepartmentofElectronicEngineering,Prof.RamMegheInstituteofTechnology&Research,Badnera-Amravati.PresentlyheisaresearchscholarwithVisvesvarayaNationalInstituteofTechnology,Nagpur,India.(E-mail:).M.V.AwareiswiththeDepartmentofElectricalEngineering,VisvesvarayaNationalInstituteofTechnology,Nagpur,India(e-mail:mva_).DigitalObjectIdentifier:10.3969/j.issn.1674-862X.2011.01.005generationisincreasingworld-wide.Germanyhasaround16%powerfromwindandDenmark20%.USisplanningtogenerate20%powerfromwind.Indiaisthefifthlargestwindenergyproducingcountry,havinggrosswindpowerpotentialestimatedas45,195MWandinstalledcapacity10,925MWin2009.However,theoutputpowerofwindgeneratorisfluctuatingandwillaffectoperationofinterconnectedgrid.Theutilitysystemcannotacceptthenewgenerationwithoutthestrictconditionofvoltageregulationduetorealpowerfluctuationandreactivepowergeneration/absorption.Theserequiresomemeasurestomitigatetheoutputfluctuationsoastokeepthepowerqualityinthegrid.Therehavebeenanumberofstudiesdonetoevaluateandmitigatetheimpactofwindgeneratingsystemonthegrid.Afewstudiesintheinterconnectedgridsystemarebasedontheformofhydrogen,capacitor,batteriesstorage,andsuperconductingmagneticenergystorage1-5.InJapan,batteryenergystoragewasusedformitigationofvariationsinwindfarmoutputtostabilizetheshortfluctuationsofoutput6.Thebulkenergystoragewasproposedformanagingwindpowerfluctuationwhichprovidesincreasingrequirementforreserve,enhancethewindpowerabsorption,achievethefuelcostsavings,andreduceCO2emissions7.Thestatisticalapproachwasproposedforutilizationoftwobatteriesenergystorage,inwhichwindpowerisusedtochargeonebatterystorageandtheotherisusedtodischargethebatterystorage8.Thecontrolmethodforthestateofchargeofbatterywasproposedin9.Thestaticcompensatorandbatteryenergystoragewasproposedforfixedspeedwindgeneratortoimprovethepowerqualityandstabilityforthepowersystem10,11.Thepenetrationofwindgenerationintothepowersystemwillincreasefurtherduetotheuseofvariablespeedwindgenerationtoaccommodatethemaximumpowerinthepowersystem.Thus,itpromoteswindgeneratingsystemthroughbatteryenergystorageintodaysscenario.Thebatterystorageprovidesarapidresponseforeitherchargingordischargingthebatterythusitactsasaconstantvoltagesourceinthepowersystem.Thebatterystorageiseffectivewhenwindspeedoutputfluctuationsarehighparticularlyatspeedjustbelowthenormaloperatingspeed.Hence,outputsmoothingstronglydependsonbatterystoragecapability.Inthispaper,theproposedsystemisefficientandBatteryEnergyStoragetoStrengthentheWindGeneratorinIntegratedPowerSystemSharadW.MohodandMohanV.AwareJOURNALOFELECTRONICSCIENCEANDTECHNOLOGY,VOL.9,NO.1,MARCH201124economicaltostrengthenthepowersystem.Inordertoverifytheeffectivenessoftheproposedsystem,currentcontrolmodeofvoltagesourceinverterisproposedwithbatterystorageandwindgeneratingsystem.ThecontrolleractionissimulatedinMATLAB/SIMULINKbasedoninstantaneousmodelingapproach.Theproposedcontrolsystemwithenergystoragehasthefollowingobjectives:Unitypowerfactoratthecommoncouplingbus;Reactivepowersupportfromwindgeneratorandbatteriestotheload;Stand-aloneoperationincaseofgridfailure.Thepaperisorganizedasfollows.Section2introducesthegeneralizedweakgridsystem.Section3givesthesystemconfigurationtostrengthenthepowersystem.Section4presentsthemathematicalmodel.Section5describesthesystemperformanceandsection6drawstheconclusion.2.WeakGeneratorinWeakGridSystemThegeneralizedwindgeneratorinterfacesysteminthepowersystemhasvoltagesoneachside.TheconnectedbusofwindgeneratorisaweakbusinthepowersystemanditisconnectedtostronggridthroughtheimpedanceZ,showninFig.1.Inthegeneralizedpowersystem,thethree-phasepoweristransmittedassymmetricalaspossible.Theline-to-linevoltageis3timeslargerthanphasevoltageandtotalthree-phasepowerisconstant.Thevoltagedropovertheimpedancecanbewrittenas-123VVIZ=(1)whereV1andV2aretherootmeansquare(r.m.s)voltage,Iisther.m.scurrentandZistheimpedanceoftransmissionlineandtransformerfeedingtogrid.Atthepointofcommonconnection(PCC),windfarmandlocalloadarealsoconnected.TheshortcircuitpowerSKinwindconnectionisgivenas21KSVZ=.(2)GridV1V2PointofcommonconnectionWindpowerPQLL+LoadZPwQwFig.1.Generalizedwindgeneratorinthepowersystem.ThechangeinwindpowerproductionwillcausechangesinthecurrentthroughtheimpedanceZ.ThesecurrentchangescausethechangesinthevoltageV2.Inpractice,connectionswithnetworkhavingshortcircuitratiolessthan2.5aretobeavoided,asitgivesrisetothevoltagefluctuationsanditiscalledasweakgrid.TheimpedanceZRjX=+isatthefundamentalfrequency.Generallytheimpedanceinpresenceofharmonicsbecomesas()LZhRjhX=+(3)wherehistheharmonicorder,thatistosay,theinductivereactancechangeslinearlywithfrequency.ThecombinationofwindpowerproductionandloadisrepresentedasPjQ+,wherePistheactivepowerandQisthereactivepower.Thereactivepowerisdependentonthephaseshiftbetweenvoltageandcurrent,asshownin(4):1tanQP=.(4)ThereactivepowerinthewindhasanimpactonvoltageV2.Theimpactisalsodependentonlocalloadandonthefeedinggridimpedance.Thus,itisnecessarytostrengthentheweakgridusingtheenergystoragesysteminthewindenergygeneratedpowersystem.3.SystemConfigurationtoStrengthentheSystemTheproposedenergystoragetostrengthenthewindgeneratinggridinthepowersystemisconfiguredonitsoperatingprincipleandbasedonthecontrolstrategyforswitchingtheinverter,asshowninFig.2.3-phase415V,50HzPointofCommonCouplingSourceBatteryEnergystorage=LoadVs,IsIbInverterAC-DCconverterInterfacingTransformerWindgeneratorPL,QLVia,b,cVsa.b.cR,LRi,LiCFig.2.Schemeofenergystoragetostrengthenthewindgenerator.PointofcommonconnectionWindpowerPL+LLoad2Grids,Is3-phase415V,50Hzpointofcommoncouplingsa,bcVR,LPL,QLLoadVia,b,cRi,LiInverterBatteryenergystorageac-dcconverterInterfacingtransformerWindgeneratorSourceIbMOHODetal.:BatteryEnergyStoragetoStrengthentheWindGeneratorinIntegratedPowerSystem253.1OperatingPrincipleIntheproposedsystem,themagnitudeofsourcecurrentisdeterminedbytheinstantaneouscurrentamongsource,powerconverterandload.Thebatteryisusedasanenergystorageelementforthepurposeofvoltageregulation.Thewindenergygeneratingsystemisconnectedtotheuncontrolledrectifierbridgewhoseoutputvoltageisvariabledcandconnectedtobatterystorageforcharging.Thebatterycanalsobechargedfromgridinlowdemandingridandcanbeusedforpeakdemand.Theerrorcurrentisinjectedthroughcurrentcontrolvoltagesourceinverterinthegridatthepointofcommoncoupling.3.2ControlStrategyoftheSystemThecontrolstrategytostrengthenthewindgeneratingsystemisshowninFig.3.Intheimplementationofcontrolstrategyintothegridsystem,adclinkisrequiredtointerfacethewindenergygeneratingsystemintothegridthroughapowerconverter.Theinductiongeneratoroutputisfirstconvertedthrougharectifier.Thedcvoltageatwhichthebatteryenergystoragesystem(BESS)isconnectedwithreferencevaluesanderrorsisfedintoproportional-integralcontroller.Theoutputofproportional-integralcontrollerismultipliedbyareferencesinewavegenerator.Hence,thedesiredreferencecurrent*RefIcanbeobtained.Thepracticalcurrentisdetectedbycurrentsensorandsubtractedfromthedesiredreferencecurrentsothattheerrorissenttothehysteresiscurrentmodecontrollertogeneratetheswitchingpattern.Thus,thiscontrolstrategyactsasaninstantaneousfeedbackcurrentcontrolmethodofpulsewidthmodulation(PWM)forswitchingtheinverteringridsystemasshowninFig.4.Fig.3.Controlstrategyofthesystem.Fig.4.InstantaneousfeedbackcontrolofPWM.Thecurrentcontrolledmodeofinverteroperationispresentedasiaiasaia()()iiidiRiLvvLdt=+(5)ibibsbib()()iiidiRiLvvLdt=+(6)icicscic()()iiidiRiLvvLdt=+(7)dciaibic()ABcdviSiSiSCdt=+(8)whereiav,ibv,andicvaretheinvertervoltages,sav,sbv,andscvarevoltagesatPCC,andiia,iib,andiicareinvertercurrents.Switchingsignalsareobtainedbycomparingreferencecurrents*sai,*sbi,and*sciwiththeactualcurrentssai,sbi,sciofsource.Thecurrenterrorsai,bi,andciareappliedtothehysteresiscontrollersthatproducethecorrectsignaltoswitchthepowerelectronicsswitchesONandOFFuntilthecurrentexceedsorfallsbelowthetolerancelimit.Inthistechnique,aseparatecomparatorisusedtodrivetheinverter.Theconductionstateofathree-leginverterisrepresentedbythreelogicvariableswitchingfunctionsSA,SB,andSC.ThecharacteristicsoftheswitchingfunctionasSA=(ai)ofahysteresiscontrollerforphaseAoftheinverter.Thecharacteristicsconstituteahysteresisloopthatcanbedescribedas0,if21,if2aAaihSih(9)wherehdenotesthewidthoftheloop,andSA=0andAS=1indicatethestateofswitches.Duetothisswitchingfunction,theinverterinjectsthecurrentintothegridinsuchawaythatthesourcecurrentisharmonicfree.Theinjectedcurrentwillcanceloutthereactiveandharmonicpartoftheloadcurrentandthusimprovethepowerfactor.Toaccomplishthesegoals,thegridvoltagesaresensedandsynchronizedingeneratingthecurrentcommandfortheinverter.Forabalancedthree-phasesource,voltageiswrittenatthegridassasbscsin()sin(120)sin(120).abcvVtvVtvVt=+DD(10)Therefore,thereferencecurrentforthecomparisonmustbederivedfromthesource(grid)voltage.ThesecurrentscanbeexpressedasVDC(Ref)BESSPIcontrollerXmultiplierIsaiaSASASwitchingsignalIsa(actual)Sine-wavegeneratorSourcevoltagedetectorVDC(actual)00.0040.0080.0120.0160.020Time(s)6420246I(Amps)ReferencecurrentHysteresisbandsActualcurrentJOURNALOFELECTRONICSCIENCEANDTECHNOLOGY,VOL.9,NO.1,MARCH201126sasbscsin()sin(120)sin(240)iItiItiIt=DD(11)whereIisproportionaltothemagnitudeofthefilteredsourcevoltageofphasea.Thisensuresthatthesourcecurrentiscontrolledtobesinusoidalirrespectiveofwhetherthesourcevoltageisunbalancedornot.Thewindgeneratingsystemwithbatteryenergystoragesystemisthebestsuitedsinceitrapidlyinjectsorabsorbsthereactivepowertostabilizethegrid.Italsocontrolsthedistributionandtransmissionsystemataveryfastrate.4.MathematicalModelofWindGeneratingSystemwithBatteryThemathematicalmodelofwindgeneratingsystemisdescribedasfollows.4.1WindEnergyGeneratingSystemTheinductiongeneratorhavingbeenusediswindturbinegeneratingsystem,becauseithasadvantagesofgeneratingthepowerfromvariablespeedprimemover,beingsuitableforhighspeedoperation,maintenance,lowercostcomparingwithothermachinesofidenticalrating,andthevoltageandfrequencybeingcontrolledbygrid.Theoutputpowerofthiswindturbinesystemispresentedas3wind12PAV=(12)where(kgm3)istheairdensityandA(m2)istheareasweptoutbyturbineblade.Itisnotpossibletoextractallkineticenergyofwind,thusitextractsafractionofpowerinwind,calledpowercoefficientCpofthewindturbine,anditisgivenasmechwindpPCP=(13)wherePmechisthemechanicalpowerofwindturbineinNm,and160.5917pC=(14)whichisalsoknownasBetzslimit.Thiscoefficientcanbeexpressedasafunctionoftipspeedratioandpitchangle.Itisahighlynonlinearfunctionhavingpowerfunctionofand.IfthemechanicaltorqueTmechisapplied,itisconvenienttocalculatePmechfromgeneratingsystem,whereistheturbinerotationalspeed.mechmechturbineTP=.(15)Therefore,mechturbinewind(,)PfV=(16)23mechwind12pPRVC=(17)whereVwindisthewindspeedinm/s.VdcEbCVdcRectifiedfromwindgeneratorIbRbIdc(rect)Idc(inv)Fig.5.dclinkforbatterystorageandwindgenerator.4.2dcLinkforBatteryandWindGeneratorIntheinverter,thecapacitorisusedastheintermediateelement,whichdecouplesthewindgeneratingsystemandgridsystemshowninFig.3.Theuseofcapacitorismoreefficientandlessexpensivethaninductoranditismodeledasdcdc(rect)dc(inv)bdCVIIIdt=(18)whereCiscircuitcapacitance,Vdcisrectifiervoltage,Idc(rect)isrectifieddc-sidecurrent,andIdc(inv)isinverterdc-sidecurrent,asshowninFig.5.Thebatterystorageisconnectedtodc-linkgridandisrepresentedbyavoltagesourceEbconnectedinserieswithaninternalresistanceRb.Theinternalvoltagevarieswiththechargestatusofthebattery.TheterminalvoltageVdcisgivenasdcbbbVEIR=(19)whereIbrepresentsthebatterycurrent.Itisnecessarytokeepadequatedc-linkleveltomeettheinvertervoltage:dcinv22VVM(20)whereVinvisline-to-neutralr.m.svoltageofinverter,switchingfrequencyis2kHz,inverteroutputfrequencyis50Hz,andM.ismodulationindex(0.9).Thusthedclinkisdesignedfor800V.Thedc-linkcapacitanceiscalculatedascpposICfV=(21)wherefsistheswitchingfrequency,Vcppisthepeak-peakvalueofvoltageacrossthecapacitor,andIoistheoutputcurrentofinverter.4.3ModelofBatteryIntheanalysisofthesystemwithbatteriesstorage,themathematicalmodelofbatteryisdependentonthesystemstudies.Thenumbersofbatterymodelsareavailableasfarastheterminalbehaviorisconcerned12.Theapproximateshort-termmodelhavingsourceEbconnectedinserieswithaninternalresistanceRbisusedforthestudy.Theresponsetimeofbatteryisdependentonitselectricalparameters.Inpracticetheleadacidbatteriesaregenerallyused.Forelectricalenergystorageapplications,alargenumberofVIdc(inv)Idc(rect)IbbbVdcRectifiedfromwindgeneratorMOHODetal.:BatteryEnergyStoragetoStrengthentheWindGeneratorinIntegratedPowerSystem27cellsareconnectedinseriesinordertoproducetherequiredoperatingvoltagesasdesignfordclink.4.4VoltageSourceInverterInthevoltagesourceinverter,eachswitchofconverterisrepresentedasabinaryswitch.ThevalueofthisresistanceisinfiniteiftheswitchisOFFandzeroifitisON.TheinverteroutputphasevoltageequationscanbewrittenandmodeledasANdcBNCN2111213112ABCVSVVSSV=.(22)whereVAN,VBN,andVCNarethephasevoltagesofinverter.Theswitchingfunctionsfortheinverterarederivedfromahysteresistypeofcontroller.TheSA,SB,andSCaretheswitchingfunctionsandVdcisthebatteryvoltage13-17.5.SystemPerformanceTheschemeofawindgeneratorwithbatteryenergystorageforextractionofwindenergyisshowninFig.2anditissimulatedinMATLAB/SIMULINKwithpowersystemblockset.TheSIMULINKmodellibraryincludesthemodelsofconverter,inductiongenerator,load,etc.Ithasbeenconstructedforsimulation.ThesimulationparametersforthegivensystemarelistedinTable1.5.1SteadyStateandDynamicStatePerformanceTheloadisconsideredasanonlinearloadforthesimulationofthesystem.Theperformanceofthesystemisobservedforthepowerqualityimprovementaswellastosupporttheload,whensourceisnotavailable.Theinverterisswitchedonat0.2s.ThesourcecurrentIs,loadcurrentIL,andinverterinjectedcurrentIinvaremeasuredwithandwithoutinvertercontrollerinthecircuitandalsoatstand-alonemodeofoperation.ThecurrentsuppliedfromTable1:Systemparametersthesourceismadesinusoidalandharmonics-freeassoonasthecontrollerisinthesystem,whichisshowninFig.6(a).TheloadcurrentinthesystemisshowninFig.6(b).TheinjectedcurrentsuppliedfromtheinverterisshowninFig.6(c).Duringtheinterval,theloadcurrentwillbetheadditionofsourcecurrentandinvertercurrent.Thegridfailureisobservedattimet=0.6sandsourcevoltageisnotavailable,thusinverterwillsupportfortheloadandwillutilizethebatteryenergystoragesystemfromwindgeneratorasastand-alonemode.Fig.6.Measuredcurrent:(a)sourcecurrent,(b)loadcurrent,and(c)inverter-injectedcurrent.Fig.7.dcLinkperformance:(a)dc-linkvoltage(b)rectifiedcurrentofwindgenerator,(c)currentsuppliedbybattery,and(d)charging-dischargingofdc-linkcapacitor.SystemparametersSpecificationsSourcevoltage3-phase,415V,50HzSourceandlineinductance0.5mHWindgeneratorparameter(inductiongenerator)150kW,415V,50Hz,P=4,Rs=0.01,Rr=0.015,Ls=0.06H,Lr=0.06H,Ave.windvelocity:5m/sdc-linkparameterdcLink-800V,C=5F.Rectifier-bridgeparameterSnubberresistanceR=100,Ron=0.01,C=1FInverter-parameter-IGBT-device,threearmbridgetypeRated:1200VForwardcurrent:50AGatevoltage:+/20VT-Ondelay:70nsT-Offdelay:400nsPowerdissipation:300WBatterystoragedc:800VInterfacingtransformerRating-1MVA,Y-Ytype,415/800V,50HzLoadparameter3-phase415V,nonlinearload_controller-OFFPowerQualitymodestand-alone-mode(a)00.70.8000(b)0000300506008000controller-OFF(c)00.70.8Time(s)(a)10050050100Isource(A)00.70.8Time(s)(b)1000100Iload(A)00.70.8Time(s)(c)Iinv(A)1000100(a)(b)(c)(d)controller-OFF00.70.8Time(s)(a)00.70.8Time(s)(b)00.70.8Time(s)(c)00.70.8Time(s)(d)850800750Vdc(V)Idc-WG(A)40200150100500Ibattery(A)50050Icap(A)JOURNALOFELECTRONICSCIENCEANDTECHNOLOGY,VOL.9,NO.1,MARCH2011285.2dcLinkPerformanceThewindenergygeneratorisoperatedtogeneratethepowerandsuppliedtotheuncontrolledrectifiertointerfaceinthedclink.Theoutputofvariablespeedinductiongeneratorsarespeeddependentanditisnecessarytoconverttheoutputintodcvoltage.Thedc-linkvoltageisshowninFig.7(a).Totransfertherealpowerfromthewindgeneratorintotheload,thegeneratedpowerisfedtorectifierforchargingthebatteries.Thecontrolstrategywillmaintaintheconstantdcvoltageacrossthedclink.TherectifiedcurrentfromwindgeneratorisshowninFig.7(b)andthecurrentsuppliedfrombatterystorageisshowninFig.7(c).Thecharginganddischargingofdc-linkcapacitorareshowninFig.7(d).Thedepthofdischargeisnotconsideredinthesimulation.5.3W