Fault-Tolerant Control for Multiphase Induction Machines With Torque Ripple Reduction Considering Harmonic Injection

Open-circuit fault is one of the common faults of multiphase motors. After fault occurrence, the control strategy needs to be modified in order to maintain smooth and uninterrupted operation. However, existing strategies with harmonic injection are unable to achieve effective decoupling of multiple planes. This letter proposes a novel fault-tolerant strategy with harmonic injection for the purpose of torque ripple reduction while enhancing torque operation range compared with state-of-the-art method. Since the higher order harmonic plane has less effect on torque ripple generation, the proposed strategy introduces harmonics into the higher order plane, thereby reducing its coupling to the fundamental plane. A seven-phase induction motor is utilized as the prototype to verify the effectiveness of the proposed fault-tolerant control technique. Furthermore, the design principles of the proposed strategy in this letter can easily be extended to multiphase motors with higher phase numbers.