Direct torque control of dual three-phase permanent magnet motor based on improved duty cycle calculation

Abstract

The multiphase permanent magnet synchronous motor (PMSM) has the following advantages: compact construction, strong fault tolerance, high power density, and small torque ripple. The motor is extensively applied to various fields, including military and electric vehicles. In this paper, a direct torque control (DTC) strategy is proposed based upon combining synthetic virtual vector and duty cycle modulation to address the drawbacks of large current harmonics and high motor losses during the traditional DTC process of dual three-phase PMSM. Building upon the conventional torque deadbeat principle, the duty cycle of the voltage vector can be worked out. Therefore, a duty cycle calculation approach is put forward on the grounds of reference torque prediction, which accurately estimates the torque demand of the motor during each sampling period, enabling the control system to more accurately calculate the appropriate duty cycle to meet real-time torque requirements. Through simulation, it is exhibited that this approach can efficiently lessen harmonic current and torque ripple while maintaining the advantages of traditional DTC.