Research On Efficiency Optimization Of Induction Motor Based On Vector Control For Electric Vehicles

The operating efficiency of induction motors(IMs)of electric vehicles(EVs)has an important influence on the vehicle economy and driving range.There is a great significance to study the efficiency optimization of IMs.Based on field oriented control(FOC)strategy of IMs in EVs,this paper research in three aspects,i.e.modeling induction motor including iron loss and iron currents compensation method,efficiency optimization strategy based on the loss model of IMs,and the current controller design.Firstly,the dynamic mathematical model and the state equation of IMs including the iron loss are established in the two-phase synchronous rotating coordinate system.The simulation models using system blocks establishing method and S-Function method are built in Matlab/Simulink.Considering magnetizing inductance of IMs in EVs is small which increase iron loss,the influence of iron loss on FOC of IMs should not be ignored.Then,the influence of iron loss on rotor flux oriented control(RFOC)is analyzed especially on the torque control accuracy.Further,two compensation methods,static compensation and static-flux compensation,are proposed in flux observation and reference current control section.The performance of different compensation method combinations are analyzed and compared.The simulation results proved that the compensation methods can achieve an accurate torque in steady-state.Secondly,focused on efficiency optimization strategy,the constraint conditions of IMs are analyzed first,and the steady-state operating area is presented.Then,a more accurate loss model is obtained than the loss model which neglects the leakage inductance.Moreover,steady-state optimal flux linkage is obtained in the whole operating conditions based on the loss model and constraint conditions.On this basis,in order to get a quick torque response,based on the steady-state optimal flux linkage and voltage equations,the dynamic efficiency optimal control strategy composed by the optimal flux control mode and outer voltage field-weakening control mode under different operating conditions is proposed.The effectiveness of the control strategy to improve motor efficiency and speeding up torque response is verified by simulation.Next,in order to achieve good decoupling performance and to improve the dynamic property of the IM,the voltage equations of IMs including iron loss are analyzed.Then,the traditional Internal Model Controller(IMC)are designed and studied,then an improved IMC with a linear feedback is proposed to improve robustness and stability of the current controller.A stronger robustness of the improved IMC has been verified by analysis results and simulation results.Lastly,an experimental prototype of IM controller is designed.Experimental study of the efficiency optimization control strategy is carried out on laboratory platform.The steady and dynamic performance of FOC,optimization performance of optimization strategy and decoupling capability of improved IMC controller are verified.