Research On Control Strategy Of Permanent Magnet Synchronous Motor Driven By Electric Vehicle

With the development of economy and society,the automobile industry is facing two major problems: energy shortage and environmental pollution.Electric vehicles have come into people's vision because of their cleanliness and efficiency.Developing new energy vehicles is the future trend.Driving motor control system is one of the key technologies of electric vehicle.This paper takes the built-in permanent magnet synchronous motor as the research object,and explores the control strategy suitable for driving permanent magnet synchronous motor of electric vehicle.The specific research contents are as follows:Firstly,the significance of the electric vehicle drive motor system is analyzed,the requirements of the electric vehicle to the drive motor are analyzed,and the built-in permanent magnet synchronous motor is selected as the research object according to the characteristics of different kinds of motors,and the research status of the control strategy of the permanent magnet synchronous motor is analyzed.Secondly,three coordinate systems of permanent magnet synchronous motor(PMSM)and their mutual transformation are introduced in detail,and the principle and implementation method of space vector pulse width modulation(SVPWM)are analyzed,and the SVPWM module is built in Simulink.Then,the vector control strategies of various subdivisions are analyzed,including Id = 0,MTPA control,constant flux linkage control,MTPV control,etc.The characteristics of these strategies are analyzed.Because MTPA control can minimize the stator current under the same motor output torque,it can effectively improve the efficiency of the motor.Under the limitation of the same inverter capacity,it can provide the maximum torque,which can be used under the motor base speed.MTPA control uses flux-weakening control in the full speed range of the motor because of the presence of motor back-EMF above the base speed.In order to simplify the control algorithm and make the algorithm easier to implement in engineering,the two control methods are tabulated,and the minimum stator current corresponding to the target torque under voltage and current limitation is calculated by using fmincon function.The current ID and IQ are a one-to-one relationship,and the vector control simulation of the motor is realized by using Simulink.In order to provide a working environment with vehicle load for driving motors and better verify the motor control performance,a hybrid vehicle model is built in simulink.The model inputs the difference between the given working speed and the actual speed into PI driver module,obtains the target torque,transfers the target torque instruction to the motor model,and transfers the real torque to the actual speed estimation model when the motor is running.The results show that the motor torque can track the driver's target torque command,so that the actual vehicle speed can track the target speed,which verifies that the control performance of the motor meets the driving requirements.Finally,in order to verify that the motor control strategy built in Simulink can run in real time in the motor control unit(MCU),a hardware-in-the-loop platform based on NI PXI is built,and the control performance of the motor is verified to further verify that the control performance of the motor meets the driving requirements.