Research On Direct Torque Control Strategy Of Permanent Magnet Synchronous Motor For Vehicle

Nowadays,with the improvement of people’s awareness of eco-environmental protection and energy conservation,electric vehicles are becoming more and more popular because of their advantages of green,efficient and energy-saving.Therefore,the research on electric vehicles had became a hot spot,and one of the core parts was the motor and its drive control system.Vector control and direct torque control were the main speed control technologies which widely used in high performance motors.Direct torque control(DTC)was a method of converter controlling the torque of three-phase motor.Unlike vector control,it directly controlled the controlled torque instead of control the torque indirectly by decoupling the current,which eliminated complex coordinate transformation.DTC had been widely used in motor control system because of its characteristics of high precision of torque,fast response speed and less strict requirements for motor parameters.This paper taken three-phase sinusoidal PMSM as the research object and DTC as the basic control method.The traditional DTC adopted hysteresis control and chose the space voltage vector by looking up the table.But whether the stator flux magnitude and torque could reach the given value accurately after choosing the space voltage vector was not in consideration.Therefore,the DTC system with hysteresis control scheme had large torque and flux ripple.In order to solve these problems,this paper applied sliding mode control theory to DTC control system of PMSM and combined SVPWM control technology to reduce the torque ripple and improve the control performance of the system.Then,the PMSM-DTC system based on SMC and SVPWM control was simulated and compared under Matlab/simulink.Finally,the PMSM-DTC experiment platform was built according to the existing experimental conditions.The digital control scheme based on CAN bus was adopted to control the experimental platform.At the same time,the traditional DTC model and the improved DTC model were calibrated separately,and then written into the controller to control the motor operation.The experimental results shown that the PMSM-DTC control strategy based on high-order SMC control algorithm studied in this paper had good dynamic and static performance of speed,which could obviously reduce the problem of large torque ripple of traditional DTC and the overshoot of the system and the steady-state error.