Research On High Torque Precision Control Of Permanent Magnet Synchronous Motors For Electric Vehicles

Permanent magnet synchronous motor(PMSM),which has strength in energy conversion,is extensively applied in driving system of Electric Vehicle(EV).However,EV is frequently operated in torque mode,which results in the requirement of improving torque performance.The torque performance is usually composed of the torque ripple and torque accuracy,yet many researchers mostly concentrate on how to reduce the torque ripple.The torque accuracy is used to measure the difference between the actual and desired value of torque,and the higher the accuracy is,the closer the real torque is to the given torque.High torque accuracy,which can ensure the rationality of torque distribution,is of benefit to improve the security of EV.Thus,increasing the torque accuracy is becoming a hot issue in the field of PMSM.The detailed research includes the following aspects:1.A modified Direct Torque Control(DTC),which is based on the mathematic model of PMSM and Space Vector Pulse Width Module(SVPWM),is introduced.And the relevant simulations have been carried out to verify that the modified DTC method can effectively improve the torque performance.2.The influence factors of PMSM's torque accuracy are introduced when using DTC,and not only the core loss,but also inverter dead-time is analyzed in detail.What's more,the corresponding simulations have been carried out,and the simulation results illustrate that how these factors have impacts on the torque accuracy.3.A high-precision torque control strategy for PMSM is proposed in this paper.This strategy consists of two parts,one part is the improvement of DTC when considering the control decoupling between the flux and the torque,another part is the compensation method for both the core loss and the inverter dead-time,and the simulation results shows that the proposed strategy can effectively improve the torque accuracy.Based on the above study,the improved DTC method and the torque accuracy compensation method are all implemented on the platform,and the feasibility and effectiveness of the proposed strategy are confirmed by the experimental results.