Novel Harmonic Current Controller for DC-Biased Vernier Reluctance Machines Based on Virtual Winding

Direct current-biased Vernier reluctance machine (dc-biased VRM) adopts a doubly salient structure and sinusoidal phase currents. It has better performance than switched reluctance machines and variable flux reluctance machines. The back electromotive force waveforms of dc-biased VRMs contain low-order harmonics. It leads to harmonic currents in phase windings. The current harmonics increase the losses and worsen controller performance. The suppression of current harmonics has become a hot research topic in literatures. However, the existing harmonic suppression methods have their inherent defects. In this article, a novel harmonic current controller based on virtual winding is proposed. Harmonic currents are decoupled and transformed into different harmonic planes, and independent closed-loop control is realized. The characteristics of harmonic planes and the relationship between them are analyzed. According to the analysis, the method of choosing valid planes and harmonic distribution is introduced. The major advantage of the proposed method is that, harmonic current sampling and control can be realized without the use of filters, and it avoids complicated design of controller parameters. Experimental results based on a dc-biased VRM are presented. It verifies that the proposed current control strategy based on virtual winding shows excellent harmonic control performance.