Research On Electric Vehicle Drive System Torque Control Under Field Weakening

In order to make EV (electric vehicle) can run on the wide speed range, EV drivesystems generally use field weakening control algorithm to expand the speed range. Butsome of the shortcomings of the field weakening control algorithm itself will reduce thetorque response speed. In addition, the asynchronous motor flux saturation will reducethe torque control precision. In order to solve the above problems, this article made thefollowing research:1. The driving system structure and the overall performance parameters werestudied to further analyze the EV drive system torque control capability and speed rangerequirements. Then, the vector control system of EV drive system was studied todetermine the EV induction motor drive system block diagram of the overallimplementation.2. The asynchronous motors field weakening running feature was analyzed. A newfiled weakening control algorithm with reference voltage calculation block wasinvolved based on the filed weakening control algorithm with voltage closed-loop toimprove the asynchronous motor torque response speed.3. Torque controller for low speed was designed, and then torque controller forhigh speed was designed after analysis of flux saturation characteristics. A new torquecontroller was designed to enhance the accuracy of the torque control by combining twodifferent torque controllers designed above.4. A20kW induction motor drive system experimental platform used in EV wasbuilt based on the research above. Then the basic functions and performance was testedon this experimental platform. The experimental results show that the basic functions ofthe drive system is perfect, governor and overload performance meet the requirements,torque control accuracy meet the requirements.