Flux-weakening control of permanent magnet synchronous motor using in electric vehicles

Interior permanent magnet synchronous motor (IPMSM) can be applied in electric vehicles for its wide-speed operation. The current vector control algorithm of an IPMSM in different speed operation region over is proposed in this paper. Form the theoretical analyses, the optimal behavior of the IPMSM can be achieved by considering three control strategies: maximum torque per ampere (MTPA) control strategy in constant torque region, constant current amplitude control in general flux-weakening region, and maximum input power flux-weakening control in high-speed region. The algorithm provides robust current regulation with maximum efficiency and torque capability for IPMSM. In different region, the optimum d-axis current command can be calculated according to different control strategy. The q-axis current command is determined from the torque command and d-axis current. In testing the proposed control algorithm, a vector control system, which consists of two closed loops of control: speed control and current control, was developed to control the IPMSM operating in different speed region. Simulation results from a machine prototype show that the algorithm provides good static and dynamic response in wide-speed region with different control strategies. This paper presents the operating principles, theoretical analyses, and simulation results of the IPMSM over wide-speed region.