Reduced Switching Frequency Alternate Clamp PWM Scheme for DC-biased Vernier Reluctance Machine System

This paper proposes a reduced switching frequency alternate clamp pulse-width-modulation (PWM) scheme for DC-biased vernier reluctance machine (DC-biased-VRM) with zero sequence current regulation capacity. DC-biased-VRM uses the additional DC bias current in armature winding to construct the rotor flux. To adjust the DC bias current, the paper proposes the utilization of an open winding inverter to provide the zero-sequence current path. Compared with the traditional three-phase inverter, the number of switching action is doubled, and there is some optimization space in adjusting the DC bias current and reducing the switching loss. For the requirements above, this paper introduces the alternating clamp control and realizes the regulation of zero sequence voltage by combining with the proposed reconfigured zero voltage vector, so as to ensure the regulation ability of zero sequence current. Finally, the effectiveness of the proposed scheme is verified by prototype experiments. The strategy can reduce the switching frequency of the inverter, and ensure low switching loss. It provides an effective solution for improving the efficiency of DC-biased-VRM drive system.