Energy-Management-for-a-Fuel-Cell-hybrid-vehicle

EnergyManagementforaFuelCellHybridVehicleJIANGZhi-ling2,1,CHENWei-rong1,QUZhi-jian3,(1.SchoolofElectricalEngineering，SouthwestJiaotongUniversity，2.SchoolofElectronicInformationSouthwestpetroleumUniversity,Chengdu,china)DAIChao-hua1,CHENGZhan-li1(3.SchoolofElectricalEngineering,BeijingJiaotongUniversity,Beijing,china)Abstract-—Inrecentyears,duetoemissionreductionpolicies,researchfocusedonalternativepowertrainsamongwhichelectricvehiclespoweredbyfuelcellsarebecominganattractivesolution.Especially,proton-exchangefuelcellhasmoreandmoreapplicationsinhybridvehicle.Themainissuesofthesevehiclesaretheenergymanagementsystemandtheutilizationrateofthefuel.Inordertooptimizetheperformanceoffuelcellsandreducefuelconsumption,thebestcontrolsolutionistopoweravehiclewithbothfuelcellandbattery.Tomodelthehybridpowertrainsbehavior,asimulationprogramhasbeenmadeandimplementedinmatlab/simulink.Inparticular,thefuelcelltypeisselectedasproton-exchangefuelcellandthebatteryislead-acidbattery.Thefuelcellprovidesthenormalrequiredpowerforelectricvehiclesrunning,whereasthebatterymodelalsoaccountsforthecharge/dischargeefficiency.Thehybridpowertrainsisequippedwithanenergymanagementsystem.Duringacceleration,powerisprovidedbythestoragebatterydischarging,whileduringdecelerationthebatteryisrecharged.Thecontrolstrategiesassumechargemaintainingoperationofthebattery,andthefuelcellsystemhastoworkarounditsmaximumefficiency.Thefeasibilityforenergymanagementisprovedbysimulationexperiment.Keywords—fuelcellstack;hybridsystem;energymanagement;battery;converter;BDCⅠ.INTRODUCTONIthasbeenacceptedthatfuelcellsintheframeofemissionreductionpoliciesareoneofthemostpromisingcandidatesforvehiclepowergenerationasanalternativetointernalcombustionengine.Theprotonexchangemembranefuelcells(PEMFCs)arethemostinterestingforthispurposeduetotheircompactnessandlowoperationtemperature[1].Soautomobilemanufacturesaredevelopingdirecthydrogen,polymer-electrolytefuelcellsystemstoprovidetractionpowerforvehiclebecauseoftheirzeroemissions[2].Atthesame,useofhydrogenfortransportationalsoopensthewindowofopportunityforalternativeinfrastructurefuelsincludingnaturalandbiomass.However,theoutputcharacteristicofPEMFCislimitedbythemechanicaldeviceswhichareusedformaintainingtheairpressure,temperatureandthehumidityinthecell.Forthisreason,thefuelcellisknownasslowdynamicresponseequipmentrespecttotheloadtransition.Itwilltakeaboutseveralsecondsforthefuelcelltobuildanothernewsteadystateoncethereisaloadtransition[3].Thisprocesswillshortentheoperationlifeofthefuelcellbecauseofsufferingtemperatureexcessorover-air-pressure.Tosolvetheproblem,thefuelcell/batteryorfuelcell/super-capacitorhybridsystemshasbeenproposed[1][3][4][5][6].Onemotivationforhybridizingpoweristoimproveitsfueleconomybyrecoveringaportionofthebrakingenergyandsustainstheoperationlifeoffuelcell.Simultaneously,usetheadvantageofbothtechnologiesandreducingtheirdisadvantagesbycombiningthehighenergydensityoffuelcellsandthehighpowerdensityofbatteries.However,thiscomplexfuelcellhybridpowersystemrequiresmoreelaboratestudiesforcomponentconfigurationandsystem-levelcontrolstrategydevelopmenttofullyexplorethepotentialbenefitsofthisadvanced978-1-4244-4813-5/10/$25.00©2010IEEEtechnology.Ahybridfuelcellpowertrainssystemisproposed,asshowinFig.1.Thepowersystemiscomposedofanfuelcell,abattery,auni-directionalDC-DCconverter(UDC)[7],Abi-directionalDC-DCconverter(BDC)[3].ThefuelcellandthebatteryareconnectedtothesameDCbusthroughtheappropriateUDCandBDC,respectively.Theproposedhybridsystemhassomeadvantages:1)Duringthestartperiodofthesystem,thebatterywillpowertothesystemtomakethefuelcellstatseasily.2)Whentheloadtransits,i.e,theloadstepsupordown,duetothefuelcellcan’trespondquickly,thebatterywillprovideorabsorbtheunbalancedenergywhilethefuelcellisonlyexportingaslowvaryingpower,whichimprovedthedynamiccharacteristicofthewholesystem.3)Reducingthetotalcost,inotherwords,thepowerratingofthefuelcellcanbedecreasedduetothebatterycanprovidepeakpower.Inthehybridsystem,fuelcellisthemainpowersourceandthebatteryistheauxiliarysource.Therefore,thecontrolstrategyneedstodeterminethepowersplitbetweenthefuelcellandtheenergystoragecomponent.Whichaimstomakethewholesystemoperateswithhighefficiencyandhighreliability.Thispaperproposesapowermanagementcontrolstrategyforthehybridpowertrainssystem,whichincludesfuelcellcontrollerandpowercontrollertwocomponents.Thehybridsystemisbuiltthroughmatlab/simulinktoverifythetheoreticalanalysis.Experimentsshowthatthemechanicaldeviceinthefuelcellcangainsufficienttimeformodulationduringtheloadtransition,whiletheloaddynamicisfulfilledbytheenergymanagementmodule.Besides,theenergystoriedinthebatterywillbemaintainedatasetlevelunderthecontrolofthepowermanagementcontrollerwhentheloadisconstantorvaryslowly.So,thesystemcanbemostlyoperatedunderanappropriatecondition.Fig.1TheprinciplediagramforfuelcellhybridsystemⅡ.SYSTEMCONFIGURATIONInFig.1,thehybridconfigurationinthepaperhasbeenproposed.ThefuelcellisaPEMFCfedwithcompressedhydrogen,whilethebatteryisalead-acidbattery.Theba