An Optimized Pulse Width Modulation for Dual Three-Phase PMSM under Low Carrier Ratio

In high-power traction system, the stator current of the dual three-phase permanent magnet synchronous motor (DTP-PMSM) suffers from large number of current harmonics due to the limitation of the switching frequency of the inverter. Thus, this paper proposes a novel current harmonic distortion minimization (CHM) pulse width modulation (PWM) method under low carrier ratio to suppress current harmonics for the DTP-PMSM, which takes the salient pole ratio, the leakage inductance and the load angle of DTP-PMSM into consideration. The mathematical model of current harmonics of DTP-PMSM using synchronous PWM is established under low carrier ratio. The established model demonstrates that the current harmonics of the DTP-PMSM are not only affected by the inverter output voltage, but also affected by the salient pole ratio, the leakage inductance and the load angle of DTP-PMSM. To achieve better control performance on harmonics suppression of the DTP-PMSM, an optimization problem considered characteristics of the DTP-PMSM is formulated to minimize the current harmonics by regulating the switching angles of each phase. The total harmonic distortion (THD) of stator current can be reduced effectively by solving the optimization problem. The effectiveness and robustness of the proposed method are verified and compared with three other methods under the same switching frequency.