Deep Flux Weakening Control with Six-Step Overmodulation for a Segmented Interior Permanent Magnet Synchronous Motor

The flux weakening control is significant for the interior permanent magnet synchronous motor to obtain a wide constant power range which is required in the electric vehicle application. A representative flux weakening method is to design an outer voltage loop using the voltage reference and the voltage limit. If the characteristic current of the motor is less than the current limit, the deep flux weakening can be achieved by applying the Maximum Torque per Voltage (MTPV) control. The proposed scheme in this paper can achieve smooth transitions among the constant toque region with the Maximum Torque per Ampere (MTPA) method, the flux weakening region with the voltage reference regulated method and the deep flux weakening region with the MTPV method. Besides, the six-step overmodulation strategy is adopted to improve the DC voltage utilization for the whole speed range. The performance of the drive system is confirmed by experiments.