Negative Sequence Current Suppression of Dual Three-Phase Permanent Magnet Synchronous Machines Considering Inductance Asymmetry

This paper investigates the source of negative sequence current and proposes its suppression strategies of dual three-phase permanent magnet synchronous machines (PMSM) in order to minimize the torque ripple. The machine model is established by considering the mutual-inductance asymmetry and magnetic coupling between windings. These unbalances can result in the negative sequence currents appearing as the second harmonic currents in dq-axis, which reach their maximum when only one set of winding is active during fault-tolerant operation. This paper proposes a second Harmonic Voltage Feedforward (HVF) compensation strategy based on exploiting the PMSM mathematical model considering mutual-inductance asymmetry. Compared with proportional-integral-resonant (PIR) control strategy, the proposed HVF strategy has better dynamic performance despite of its dependence on motor parameters. Therefore, a hybrid control of combining PIR and the second HVF strategy is proposed to inherit both advantages. The experimental results of traditional PI control strategy and three suppression strategies are compared. The comparison results validate the effectiveness of three suppression strategies, especially the hybrid control strategy.