A MCU Based Intelligent Charger with Multi Chargin

AMCU-BasedIntelligentChargerwithMulti-ChargingModeChang-HuaLinChi-YuChenMin-HsuanHungDept.ofElectricalEngineeringTatungUniversityTaipei,[e-mail].&C.Eng.NationalIlanUniversitySt.John’sUniversityofS.&T.Ilan,TaiwanNewTaipeiCity,[e-mail]@mail.sju.edu.twAbstract—AMCU-basedchargerfortheLiFeO4batterypackisimplementedinthispaper.Themaincircuitisafull-bridgephase-shiftconverter.Theusercanselectthechargingstrategyandobservethestateofcharge(SOC)ofthebatteryfromtheoperationinterface.Moreover,theproposedchargersystemcommunicateswiththebatterymanagementsystemviatheI2Cinterface,andgeneratesthechargingcurrentaccordingtotheestimatedSOCandtheselectedoperationmode.Inaddition,thechargingcurrentiskeptatpresetconstantvaluebymodulatingthephase-shiftamounttoshortthechargingtimeandimprovethebatterylifespan.Furthermore,therearethreechargingstrategyforuserselection.Alltheexperimentalresultsarealsoprovided.Keywords—charger;full-bridgephase-shift;SOC;battery;microcontroller-based.I.INTRODUCTIONOwingtotheglobalclimatechangeandtheabnormalrisinginternationalcrudeoilprices,sustainabledevelopmentforenvironmentprotectionanddiscoveryofcleanandgreenenergyareessential.Themainairpollutionemissionsnotonlyfromindustrialmanufacturing,butalsothedailylifeofthefuelaboardthevehicle,itsengineemissionsareoneofthemajorsourcesofpollution.Especiallycarbondioxideistheculpritcausinggreenhouseeffect,thedestructionoftheecologicalenvironmentisverylarge.Therefore,manyresearchesofelectricvehiclehavebeencontinuouslydevelopedandstillanattractivetopic.Relativetothetraditionalgasoline-poweredvehicles,theelectricvehicles(EV)canachievelowpollutionandlownoise.Moreover,secondarybatteryusedinelectricvehiclesmusthavehighenergydensity,longcyclelife,nomemoryeffectandtheabilitytoprovideinstanthigh-powerhigh-current.Recently,Battery-poweredproductioncanprovidemanyadvantagessuchascompactvolume,lowerweight,highersafety,longerlifecycle,higherdischargecurrent,andrechargeable.However,thebatterymanagementsystemisessentialformonitoring,balancing,andprotectingthebatterypackduetoexpensivebatterycosttoprolongthebatterylifespan[1].Inaddition,abatterychargerwithhighperformanceandanadequatechargingcontrolisabsolutelynecessary.Sofar,thetraditionalCC-CVcharging,shownasFig.1,isthemostwidelyusedmethod[2]-[3].Inthispaper,theproposedsystemincludesamicrocontrollerasthecontrolcore,andaninterfacetokeyincommandsandtoobservesomeinformation.AsshowninFig.2,theimplementedintelligentchargerisdrivenbyusingreasonablealgorithmaccordingtouser’sdemand,andthenchargetoLiFeO4batterypack[4]-[5].Fig.1ThediagramofthetraditionalCC-CVchargingmethod.Fig.2Thediagramoftheproposedintelligentcharger.II.SYSTEMDESCRIPTIONFORTHEFULL-BRIDGEPHASE-SHIFTCOVERTERAgeneralbatterycharger,whichextractspowerfromanac-linesourcetocontrolthepowerflowtochargethebatterysystem,consistsofanAC/DCrectifierusedasthepowerfactorcorrector(PFC)andaDC/DCconvertertransformingtheDCvoltagetoanothervoltagelevelforchargingbattery.Inordertoimprovethechargingperformances,researchershaveproposedvariouschargingcircuitsandcontrolalgorithms.ToimplementaDC/DCconverter,whichcanbeappliedfora600Wfastcharger,afull-bridgephase-shiftconverter(FBPSC)isemployed.Fig.3depictsthecircuit286978-1-4799-4315-9/14/$31.00c2014IEEEconfigurationoftheusedFBPSC,wherethemaincircuitiscomposedoffourpowerswitches(S1-S4),atransformerforisolation,twodiodes(D1-D2)forrectification,Lo-Cofilter.Inthemaincircuit,theresonantcomponentsarethecombinationoftheleakageinductanceLlkandtheparasiticcapacitances(Cds1-Cds4)toachievezerovoltageswitching(ZVS).Fig.3Thecircuitconfigurationoftheusedfull-bridgephase-shiftedconverter.Inchargingprocess,thepowerswitchesoftheFBPSCarealternativelyswitchingaccompanywithphase-shiftcontrol.ThekeywaveformsoftheFBPSCareshownasFig.4,wherethedefinitionofthedutycycleasfollowsD=tonT×100%(1)Fig.4ThekeywaveformsoftheFBPSCinaswitchingperiod.ModeI[t0-t1]Inthismode,boththeS1andS4areturnedon,theelectricalenergyarecoupledfromtheprimary-sideofthetransformerTtothesecondary-side,andthenchargingtheoutputinductorLothroughtherectifyingdiodeD1.FromFig.5,wecanobtaindipri(t)dt=1ndiLo(t)dt=Vin-nVoሺLlk+n2Loሻ(2)wheren=NpሺNsሻFig.5TheequivalentcircuitandpowerflowoftheModeI.ModeII[t1-t2]TheS4isstillturnedoninthisModeasshowninFig.6.Duringthistimeinterval,theleakageinductorcurrentIprikeepthesamedirectionandchargetoCds1anddischargetoCds4,respectively,untilthevoltageVABdecreasetozeroandthenthebodydiodeDs2willbeconducted.Fig.6TheequivalentcircuitandpowerflowoftheModeII.ModeIII[t2-t3]AsshowninFig.7,thebodydiodeDs2isconductedduetoforwardbias,i.e.thevoltageVDs2descendtozerosoastoachievezerovoltageswitchingonS2.Inthemeanwhile,therelationshipcanbeexpressedasdipri(t)dt=1ndiLo(t)dt=-nVoሺLlk+n2Loሻ(3)Fig.7TheequivalentcircuitandpowerflowoftheModeIII.ModeIV[t3-t4]InModeVI,theS4isturnedoffandtheprimary-sidecurrentIpriwillchargetoCds4anddischargetoCds3,respectively,asshowninFig.8.Finally,thevoltageVABwillfallto-Vin,andthesy