电动车用无刷双馈电动机恒功率弱磁研究

Constant Power Flux-Weakening Control of Brushless Doubly-Fed Motor for Electric Vehicles

电动车用无刷双馈电动机在基速以下恒转矩运行、基速以上恒功率弱磁扩速运行。由于励磁电流可控制,理论上能够调节励磁电流实现恒功率控制。但是,由于无刷双馈电动机的非线性特性导致其反电势为不规则方波形状,类似直流电机那样采用相电压反馈控制励磁电流实现恒功率控制困难较大。利用三相电枢绕组电阻电压间接测量反电势控制励磁电流,实现无刷双馈电动机恒功率弱磁控制,保证恒功率阶段电机的出力最大,从而提高无刷双馈电动机恒功率弱磁扩速范围,满足电动车对驱动电机的要求。仿真、实验结果验证了该方法的有效性。

The brushless doubly-fed motor runs with constant torque below the base speed and with constant power by field weakening over the base speed. Theoretically speaking, regulation of exciting current can be achieved to realize the constant power control as the exciting current is controllable. But unlike linear motors, brushless doubly-fed motors find difficult to realize constant power control by utilizing phase voltage since the nonlinear characteristics may cause BEMF to be in irregular square wave. The field current of brushless doubly-fed motor was controlled by the flux weakening control with three-phase armature resistance voltage in order to obtain the maximum output and extended the speed range ,which satisfied the demands of electric vehicles. Simulation and experimental results confirmed＇ the theory of the flux weakening method is effective.