Seite - 259 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 616 (a) Efficiency MAP under proposed control method (b) Efficiency MAP for contrast Figure11.EfficiencyMAPofdrivesystem. It is clear that thepeakefficiencyof thedrive systemunder theproposedmulti-level current hysteresismodulation is 3%higher than that of the contrastingdrive system, becausemulti-level currenthysteresismodulationreachesalowerswitchingfrequencyofinverterdevicesandthenreduces inverterswitchingloss.Wecouldalsoseethat thehigh-efficiencyareaof thedrivesystemis largerthan in thecontrastingsystem,extendingto lowspeedandlowtorqueareas,because in theregionofstar modeandtrianglemodethere isonlyone inverterworkingandproducingswitching loss. The iron losscausedbythestatorvoltagevector in theunsteadystate is less thanthat in independentmode because thestatorvoltageamplitude instarandtrianglemodeis lower. Wealsoconductedasimulationofasmallelectricvehicle foreconomicperformance. Thedrive systemunder theproposedcontrolmethodwasequipped,andthedrivesystemunder the traditional two-level currenthysteresismodulationwithoutwindingmodeswitchingfunctionwasalsousedfor contrast. Thebasicparametersof thevehicleareshowninTable6. Table6.Parametersofvehicle. Items Parameters Vehicleweightm0/kg 950 DragcoefficientCd 0.30 WindwardareaA/m2 2.11 Reductiongearratio i0 8.4 Rollingradius rg/m 0.307 Rotationalmassconversionfactorδ 1.1 Rollingresistancecoefficient f 0.015 Transmissionefficiencyηm 0.95 RateofbrakingenergyregenerationRb 0.6 259