Harmonic Torque Suppression Methods for Single-Phase Open-Circuit Fault-Tolerant Operation of PMSM Considering Third Harmonic BEMF

Abstract

This article proposes a novel type of the 2nd and 4th harmonic torque suppression methods during conventional single-phase open-circuit fault-tolerant operation when considering the 3rd harmonic back-EMF of permanent magnet synchronous motor (PMSM). These suppression methods are based on injecting the 3rd harmonic currents into the two remaining healthy phases, which produces harmonic torque of opposite phase to cancel the original one. The suppression can have three different constraints: maintaining the average torque, eliminating the 2nd harmonic torque, and eliminating the 4th harmonic torque. They cannot be achieved simultaneously. Combining any two of them leads to a particular injection method. Three particular methods are developed and their performance are investigated by theoretical analysis and compared against the conventional one. The proposed fault tolerant control strategies are applicable to various fault-tolerant inverter topologies by using these novel phase current references, whereas the current tracking algorithms could be different. To ease validation, a four-leg inverter topology is selected to implement such injection methods to a three-phase star-connected 10-pole/9-slot PMSM. The experiments validate that tracking the proposed current references can effectively suppress the harmonic torque, which confirms the theoretical analysis.