An Adaptive Torque Ripple Suppression Method of Three-Phase PMSM During Single-Phase Open-Circuit Fault-Tolerant Operation

Abstract

This paper proposes an adaptive torque ripple suppression method by paralleling resonant term to current PI controller and duplicating the faulty leg modulation wave to neutral leg. The proposed method is applicable to three-phase star-connected permanent magnet synchronous motor (PMSM) during single-phase open-circuit fault-tolerant operation with four-leg inverter topology. Feedforward compensations can be adopted to realize a zero-sequence current injection and reduce torque ripple in post-fault operation. However, the compensated voltage is related with phase resistance which varies with temperature rise and this results in unexpected 2nd harmonic torque ripple. In this paper, the 2nd harmonic voltages in dq axis caused by the inaccuracy of feedforward compensation are derived. Therefore, the 2nd harmonic resonant controllers are added parallel to PI controller in current loops to adaptively compensate the voltage error, which will further suppresses the 2nd harmonic torque ripple. Moreover, the modulation wave of the faulty phase is duplicated to neutral leg. This modified modulation does not require additional modulation algorithm and inherits the high voltage utilization of SVPWM. Experiments verify that the proposed method can effectively suppress the 2nd harmonic torque ripple and maintain voltage utilization.