A New Flux Weakening Control Strategy for IPMSM (Interior Permanent Magnet Synchronous Machine) in Automotive Applications 2020-01-0466

As one of the core components of electric vehicles(EV), the drive motor system has a significant impact on the EV operation performance. The interior permanent magnet synchronous motor (IPMSM) has a wide range of applications in EV, due to its high efficiency, high power density, high torque current and wide speed range. In the field of EV, motor control system is required to have a high operating range. IPMSM operates at constant torque mode below rated speed and constant power mode above rated speed. The back electromotive force(Back-EMF) generated by the rotor in the constant power mode causes the inverter output voltage to saturate. Therefore, it is necessary to ensure that the controller is still operating in the linear region by applying a flux weakening(FW) current to the stator.

This paper propose an optimal FW path control strategy based on a state space consisting of a direct-axis current and a cross-axis current, bounded by maximum torque per ampere (MTPA) curve, maximum current curve, and maximum torque per voltage (MTPV) curve. The approach is founded on the proposed method to adjust d- and q-axis reference stator current along constant torque curves using two-dimensional lookup tables. The control strategy is aimed at maximizing the output torque range and minimizing motor armature current at full motor speed range. To verify the strategy, a motor controller for EV is developed based on Infineon TC265 in this paper. Simulation and experimental result show that the control strategy can greatly improve the speed range of the motor and ensure good controllability of the torque above rated speed.