Research On Direct Torque Control System Of Permanent Magnet Synchronous Motor For Electric Vehicle Based On Model Predictive Control

Direct Torque Control(DTC)is a rapidly developing motor control technology.Its application in permanent magnet synchronous motor(PMSM)system has also attracted the attention of academia and industry.Compared with the field orientated control technology widely used in electric vehicle drive system,DTC has less dependence on motor parameters,faster dynamic torque response,and does not need complex rotating coordinate transformation and mechanical position sensor.Its application in electric vehicle drive system has potential to be further explored.Firstly,the mathematical model of PMSM and its electromagnetic torque equation are introduced.According to the control idea of DTC,combined with stator flux and electromagnetic torque equation,the direct torque control(ST-DTC)based on switching table is introduced.Modeling and Simulation of ST-DTC can realize the correct control of surface permanent magnet synchronous motor(SPMSM)and interior permanent magnet synchronous motor(IPMSM).In order to improve the control effect,after summarizing the general rules of action of arbitrary voltage vectors on control variables,combined with the low complexity requirements of practical application of motor,SPMSM and IPMSM are divided into a voltage vector selection region which is only affected by the parameter of torque angle.In the selected area,only one fixed angle is selected as the position angle of the applied voltage vector.The direct torque control system based on fixed voltage vector angle selection strategy is modeled and simulated,and the correct control of SPMSM and IPMSM can also be realized.In order to further improve the integrated control effect of two control variables in DTC,a direct torque control strategy based on variable angle predictive control strategy is established.In this strategy,the angle of the voltage vectors available in each interval is variable.The angle is optimized by combining the predictive control with the constructed evaluation function.The simulation results show that the direct torque control based on variable angle predictive control strategy achieves smaller control variable ripple than the direct torque control based on switching table and the direct torque control based on fixed voltage vector angle selection strategy.Finally,in order to improve the control effect and reduce the computational load of the system as much as possible.In this paper,the number of voltage vectors is optimized and the predictive equation of control variables is simplified.The hardware platform is used to verify that the optimized predictive control can greatly reduce the operation time and ensure the control accuracy unchanged.