Active Current Harmonic Suppression for Torque Ripple Minimization at Open-Phase Faults in a Five-Phase PMa-SynRM

This paper presents an active phase current harmonic suppression method to smartly and adaptively perform torque ripple minimization (TRM) under open-phase fault conditions in a five-phase permanent-magnet-assisted synchronous reluctance motor (PMa-SynRM). The five-phase machine is gaining increasing attention due to its promising fault-tolerant and wide-speed operation capabilities. However, during the fault-tolerant operation, the torque ripple is substantially increased with dangerous vibrations. Until now, most TRMs have been primarily performed to maintain the constant magnetomotive force while only analyzing its fundamental harmonic. However, large torque variations are also caused by unexpectedly modulated high-order harmonic fluctuations that are challenging to predict. This fluctuation in current harmonics is highly destructive to reluctance machines due to its higher nonlinearity. To address this critical challenge, a real-time active TRM technique has been proposed that will be smartly adaptive to identified harmonic fluctuations. To achieve this, the proposed TRM solution systematically consists of three major steps: first, active harmonic identification; second, harmonic injection; and third, vector rotation of phases. To precisely identify fluctuating harmonics in a real time, a high precision but compact correlation-based monitoring algorithm has been proposed. A detailed theoretical analysis has been carried out through a finite-element analysis. The experimental tests are conducted to validate the proposed theory through a five-phase PMa-SynRM drive controlled by Texas Instruments DSP F28335.