A Simple PWM-based Direct Torque Control for Dual Three-phase Permanent Magnet Synchronous Machine Drives

This paper investigates the PWM-based direct torque control strategies for dual three-phase permanent magnet synchronous machine (PMSM) drives. The classical switching-table-based direct torque control (ST-DTC) scheme for dual three-phase drives usually suffers from significant harmonic currents, large torque ripples and variable switching frequency. In this paper, two simple formulae are developed to obtain the amplitude and angle of the torque-production-related reference voltage vectors from the errors of torque and stator flux. To further reduce the harmonic currents caused by machine/inverter asymmetry, harmonic current regulators are employed to generate the harmonic-current-related reference voltage vectors. The specific space vector pulse width modulation (SVPWM) technique is employed to implement the reference voltage vectors. With the proposed method, not only the harmonic currents and torque ripples have been significantly reduced, but also the switching frequency is constant. The experimental results validate the effectiveness of the proposed strategy.