A Novel Sequential Direct Torque Control Scheme for Seven-phase Induction Motors

Traditional direct torque control method suffers from the issues of torque ripple and harmonic currents for multiphase motors. This paper firstly extends the concept of virtual vectors for a seven-phase motor to eliminate harmonic currents. Secondly, the duty cycle optimization is utilized to reduce the torque ripple. Finally, a novel cascade method is proposed to select the voltage vector which can further alleviate the torque ripple. Simulation results verified that the proposed method can effectively reduce dynamic and steady-state torque ripple at both high and low speed. This paper uses a seven-phase motor for an illustration, but it should be mentioned here that the proposed method is applicable for multiphase motors with any number of phases.