Page - 153 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 1503 AdetailedbatterymodelingandEKF-basedSOCestimationcanbefoundinthereference [33]. Note that the proposed battery system can also allowdifferent SOC-estimation algorithms to be programmedandcompared. TofurthervalidatetheproposedSOC-estimationalgorithmunderrealisticanddynamicsituations, theNewEuropeanDrivingCycle (NEDC) loadprofile fora typicalelectricvehiclewasapplied to the 12-cell seriesbattery-packprototypetosimulate theelectricvehicleapplicationsunder theambient temperatureeffectandcomparedwith thestandardEKF-estimationapproach. TheNEDCloadprofile is showninFigure14a, subjectedto theambient temperature. It isworthytonote that the loadprofile hadbeenscaleddowntofit thebatterypack. TheprogrammableDCelectronic loadwasusedtorun thepre-programmedNEDCloadprofile. Before theexperiment, thebatterypackwas fullychargedto obtainaninitialSOCof100%.ThecalibratedAmpere-hour (Ah)datareadingfromtheequipmentwas usedas thereference.AsshowninFigure14b, theSOCestimationof theproposedSOCmodelcan followthereferenceSOCrobustly. Despite the loadprofilechangingdrastically, theSOCerrorcan reboundafterashortperiodofdrift.Ontheotherhand, theSOC-estimationresult fromtheEKF-based SOCmodeldriftedawayafter several test cycles. Insummary,under theNEDCtestprofile,which is usedtosimulate the load inreality, theproposedSOC-estimationmethodperformsbetter thanthe EKF-basedmethod. Figure 14. (a) New EuropeanDriving Cycle (NEDC) current profile; (b) SOC comparisonwith EKF-basedmodel. After theSOCestimationwasvalidated, thedualdiagnosisandprotectionschemeswere tested underdifferent fault conditions. In the12-cell seriesbattery-packsystem, themaximumcurrentof the batterycellwasset to10Awithamaximumdelayof10safter the fault isdetected. Thisprovides limitationsonthecurrentandthe timedelayused in the faultdiagnosis.Note that thesevaluescanbe adjusted. Figure15showsthefault-detectionandself-recoverycurve.Once theexternal short-circuit occurred, theanalogschemedetectedthe faultwithinaveryshort timeandgeneratedaprotection signal to turnoff thedischarging switch, as shown inFigure 15. It tookaround100msbefore the faultwasdetected. Thus, theresult showsthat theexternal short-circuit fault canbedetectedandthe systemcanlater recover fromthefault. 153