Study On Wide Speed Range Control Methods Of IPMSM For Electric Vehicle

Motor is the core component of electric vehicle drive system,whose control strategy and speed governing performance have a great impact on the vehicle performance and driving experience.Combined with the operating conditions and driving requirements of electric vehicle,this paper studies the control strategy in the wide speed range of permanent magnet synchronous motor.The operating condition of electric vehicle is complicated and changeable,which requires that the driving motor has a wide speed range and strong torque output capability.In this paper,interior permanent magnet synchronous motor(IPMSM)is selected as the electric vehicle driving motor,and the vector control strategy in the wide speed range is put forward.At low speed the motor is controlled by maximum torque per ampere(MTPA),and at high speed it is controlled by flux-weakening control method based on negative direct axis current compensation.The proposed control strategies can make the motor smoothly transit from low speed to high speed zone,and make the drive system operate with high efficiency and wide speed range.In order to further improve the utilization ratio of DC bus voltage,a simplified SVPWM over-modulation algorithm is applied in the control system,and the influence of over-modulation algorithm on the performance of flux-weakening control is analyzed.The simulation results show that under the condition of the bus voltage constant,the application of over-modulation algorithm can improve the output voltage of the inverter,and increase the torque output in flux-weakening area with shorter dynamic response time.At the same time the method can also expand the speed range.In the vector control system of using traditional current PI regulator,the problem of incomplete current decoupling exists.When the electric vehicle is driving at high speed,the motor runs in the flux-weakening area.At this moment,current coupling effect is more prominent,which results in big tracking error of direct-axis and quadrature-axis current,and also leads to poor performance of torque output.In this paper,current feedback decoupling algorithm is proposed to realize the complete decoupling control of the current.In accordance with the need of motor parameters in the decoupling algorithm,recursive least squares method is adopted to identify the parameters,which can improve the system robustness to parameter perturbation.The results of simulation suggest that the algorithm proposed can make the actual current rapidly and accurately track the given current in flux-weakening area.As a result,the torque output is increased,and the system dynamic capability is improved.Finally,the hardware platform of electric vehicle motor drive system is designed with TMS320F28335 as the main control chip,and the corresponding software code is written.Then some preliminary experiments and tests are carried out.The results show that the wide speed range control strategies proposed in this paper are effective and feasible,which lay the foundation for further research.