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

This article proposes adaptive torque ripple suppression methods by utilizing resonant controllers during the single-phase open-circuit fault-tolerant operation of a three-phase star-connected permanent magnet synchronous motor (PMSM). A zero-sequence current is supposed to be injected to maintain the postfault torque the same as the prefault torque. According to the postfault PMSM model, a feedforward voltage compensation can be adopted to inject the zero-sequence currents and, hence, attenuate the postfault speed and torque ripples in the vector control framework. However, the feedforward voltage compensation, which is related to the phase resistance and leakage inductance, may be inaccurate due to the temperature variation, etc., and hence, an unexpected second harmonic torque ripple still exists. In this article, the adaptive suppression methods of the second harmonic torque are proposed. The first one constructs a novel closed current loop of the zero-axis and the second one modifies the controllers in the dq-axis current loop. These methods are based on the resonant controllers, which can adaptively compensate for the voltage needed for the zero-sequence current injection. Experiments are implemented based on a four-leg inverter and the performance comparison between the feedforward compensation and adaptive compensation validates that the proposed methods can effectively suppress the postfault torque and speed ripple.