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To achieve the fault-tolerant operation of motor drives, many control algorithms have been proposed. Among them, it is more flexible and intuitive to find solutions to phase current at phase coordinate. Then it is necessary to track the given phase current. Up to now, several current controllers have been proposed. A hysteresis controller suffers from the drawback of the variable switching frequency. Proportional-integral control cannot track ac signals with zero error. As to the proportional resonant controller, its performance is highly dependent on the accuracy of motor speed detection. Considering this, a current controller is based on the adaptive filter. The adaptive filer is worked as the current controller by adjusting its structure, in which the motor model is extra introduced. The controller updates the tap weight in each control cycle until it outputs the optimal voltage to track the given phase current. Besides, the adaptive algorithm is improved by adding a feedforward term to gain a higher dynamic response. Moreover, to ensure the stability of the controller, the control parameter selection principles are analysed and acquired accordingly. Finally, several groups of experiments are conducted. The experiment results coincide with the analysis.

This paper mainly focuses on the third harmonic current suppression for symmetrical sixphase fault-tolerant permanent magnet synchronous motor drives. First, a brief motor model is established to analyze the source of the third harmonic current. Resonant controller is always appreciated in terms of harmonic current suppression. However, its performance is highly depended on the precise of the motor speed, which makes it not really suit for variable-speed applications. Fortunately, adaptive filter can skip this problem. Then a current controller based on the adaptive filter is designed to eliminate the third harmonic current. However, the dynamic response of the controller designed is unsatisfactory. Besides, the steady edge of the controller is rather narrow, which limits the operation range of motor. Then some improvements are made to the structure of the controller as well as the adaptive algorithm. Finally, several groups of experiments are conducted to compare both steady performance and dynamic performance of the controller based on adaptive filter and the improved controller. The experiments results coincide with the analysis and several conclusions are drawn. Besides, the proposed controller also applies to the elimination of other harmonic current.INDEX TERMS Adaptive filter, current controller, harmonic suppression, least mean square.

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