This paper proposes a method for suppressing the torque ripple caused by a partial voltage saturation in an active power decoupling motor drive utilizing a motor neutral point. In motor drives with active buffers that use motor leakage inductance, partial voltage saturation causes power pulsation. This voltage saturation is caused by a combination of positive-sequence voltage for motor speed control and zero-sequence voltage for active buffer control. This partial voltage saturation causes torque ripple at frequency that is four times the power supply frequency. To reduce the torque ripple caused by partial voltage saturation, this paper applies a zero-sequence priority type flux weaking control and a motor PIS current control. A prototype is used to validate the proposed method. The torque ripple of the quadruple-frequency component of the power supply which is caused by partial voltage saturation, is reduced by 99.8%. Consequently, the total torque ripple is reduced by 87.6%.
Kawauchi et al. (Sat,) studied this question.