Research On Vector Control For Permanent Magnet Synchronous Motor Of Electric Vehicle Over Full Speed Range

With the shortage of fossil energy,atmospheric pollution and the greenhouse effect,new energy electric vehicles have attracted more and more attention.As one of the core components of electric vehicles,motor drive system directly affects the power and handling of electric vehicles.Permanent magnet synchronous motor(PMSM)has become the first choice motor for electric vehicles due to its high efficiency and reliable operation.In this paper,the vector control strategy of permanent magnet synchronous motor is studied in the full speed domain,and the speed regulation range is divided into the base speed and above and the base speed.Firstly,in order to meet the needs of low-speed and high-torque conditions such as frequent starting and climbing of electric vehicles,it is necessary to select the built-in PMSM with salient pole effect as the driving motor.The maximum current-torque ratio(MTPA)of the control strategy below the base speed is required.Aiming at the slow response of motor speed caused by sudden load change under MTPA control,and the chattering problem of traditional sliding mode variable structure,this paper proposes an improved power speed sliding mode controller(SMC)to replace the traditional PI speed controller.The simulation results verify that the improved SMC speed regulator can stably follow a given speed,improving the system's steady-state accuracy and response speed.Next,in order to meet the needs of high-speed driving in electric vehicles,PMSM needs to continue to increase after reaching the base.As the speed increases,the stator winding voltage of the motor increases,and the on-board power supply capacity is constant,and the output voltage is limited.Therefore,the motor needs to be weak-magnetically controlled to operate above the base speed.In order to reduce the AC and DC current coupling effect under high-speed motor operation,based on the traditional negative compensation weak magnetic control,a current decoupling module based on voltage compensation is designed.The simulation results show that the speed waveform is consistent with the expected speed setting.The torque ripple is also small,the system response is also fast,and the MTPA and weak magnetic control strategies are smooth,but this method needs to update the accurate motor parameters in real time,and the control system is relatively complicated.Then,in order to further simplify the control system of the drive motor and completely eliminate the current coupling effect during the flux-weakening operation,this paper introduces two single-current regulation flux-weakening control strategies of the fixed-axis and the alternating-axis.From the theory and simulation,compared with the fixed-axis flux-weakening control method,the alternating-axis flux-weakening control method has the advantages of strong load capacity and high motor efficiency,and is more suitable for the control strategy of electric vehicles.Finally,based on the alternating-axis single-current regulation flux-weakening control method,the fuzzy self-tuning fuzzy PI speed controller and anti-saturation PI current controller are designed.Compared with the traditional PI controller,the speed and torque fluctuation are smaller,which further enhances the system.Robustness enhances the ride comfort of electric vehicles at high speeds.