Page - 289 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2016,9, 997 disR chgR oV oc V oI Figure7.Batteryequivalentcircuitof theRintmodel. In the diagram, Rdis and Rchg are the internal resistance of the batterywhen charging and discharging, andVoc is the open circuit voltage of the battery. Rdis,Rchg, andVoc are functions of thebatterystateofcharge (SOC)andtemperatureT.Whenthebatterypowerdemandisknown, the terminalvoltageof thebattery,Vo, andcurrent, Io, canbecalculatedbasedonthemathematicalmodels describedbelow. Pcmd=VoIo, (4) Vo=Voc−RintIo, (5) BycombiningEquations (4)and(5),Equation(6)canbeobtained. Io= Voc 2Rint − √ ( Voc 2Rint ) 2 −Pcmd Rint , (6) Here,Rint is the internal resistanceof thebatterywhenchargingordischarging;andPcmd is the batterydemandpowerwhenchargingordischarging. ThecurrentbatterySOCvaluecanbecalculatedbytheamperehouralgorithm[26]methodwith thespecific formulashownas follows: SOC(t)=SOCstart− ∫ t 0 Iodt Qmax , (7) whereSOCstart is the initialbatterySOCvalue,andQmax is themaximumbatterycapacity. Theworkingstateandrelatedparametersof thebatteryare related to the temperature, so the changeof the internalbattery temperatureshouldbeconsidered. Thespecificcalculationformula is presentedas follows: mcp dT(t) dt =RintI2o(t)−hcA[T(t)−Ta], (8) whereA is the totalheatdissipationareaof thebattery, cp is thespecificheatcapacityof thebattery,hc is theheat transfercoefficientof thebatterycoolingsystem,andTa refers to theambient temperature. Basedontheaboveequations, thebatterymodel isestablished inSimulink. The inputandoutput signals, aswellas thecalculationmoduleofbatterymodel, areshowninFigure8. Thebatterymodel mainly includes thecurrent, internal resistance, terminalvoltage,outputpower,SOC, andtemperature calculationmodules. Themaincharacteristicparametersof thebatteryareshowninTable8. 289