Development Of Permanent Magnet Synchronous Motor Controller For Low-speed Electric Vehicle

In the context of energy crisis and environmental problems,Low-speed electric vehicles(EV)are popular in third and fourth tier cities because of low noise,low cost,energy conservation and environmental protection.Research on the control strategy of low-speed EV driving system is helpful to promote the industrialization of EV in China,and improve the core technology of high-end EV through the technology upgrading of low-speed EV.At the same time,low-speed EV demand to start quickly and run efficiently.This paper focuses on the key technologies of permanent magnet synchronous motor(PMSM)such as Maximum Torque Per Ampere(MTPA)control and flux-weakening control,and a low-speed EV motor drive system is constructed.First of all,This paper introduces the industry status of low-speed EV and the research status of drive motor and controller at home and abroad.According to the low cost and high performance requirements of low-speed EV drive system,this paper compares different drive motor,position detection devices and power electronic devices.So this paper chooses a 3 kW PMSM with magnetic encoder as drive motor.Secondly,this paper expounds the basic principle of vector control,introducing the principle of coordinate transformation,the mathematical model of the permanent magnet synchronous motor(PMSM),PMSM control strategy,space vector pulse width modulation technology.This paper introduces the improvement scheme of the new hardware circuit module base on the old version of software and hardware system.This paper also completed the program design of initial,protection module and Systick timer.Especially,this paper proposes position detection algorithm,velocity calculation method and Z signal calibration position method based on magnetic rotary encoder,and the validity of the research is verified by experiments.Besides,this paper presents an anti-slip slope control method for the EV.Then,this paper analyzes and compares the MTPA control formula method and the MTPA control look-up table method of IPMSM.The look-up table method can save program running time and make the most of the motor torque output capacity,and raise the low-speed EV battery life by increasing motor efficiency.In this paper,the flux-weakening algorithm based on the voltage difference changing the dq current vector and flux-weakening algorithm based on curve fitting are studied,which make the motor get wider range of speed regulation.Finally,a comprehensive performance test is carried out for the drive system.The test results show that the motor drive system performs well and meets the expected design requirements.