Analysis of a Novel Motor Drive System with Zero Common Mode Voltage

When the back-to-back (BTB) three-level neutral-point clamped (NPC) converter is applied to motor drive occasions, the high-frequency common-mode voltage (CMV) caused by the switching action of the semiconductors has potential security risks. By installing a novel DC-DC converter at the DC bus of the BTB-NPC), the common mode current circuit is disconnected, and a zero common mode voltage motor drive system (ZCMV-MDS) is proposed in this paper. Based on the ZCMV-MDS, a safe grounding can be provided for the motor. In this paper, the state space model of the addition novel DC-DC converter is established, and the optimization modulation strategy is proposed. Further, a multi-port expansion scheme is also analyzed. Under the multi-port expansion of the novel DC-DC converter, the duty cycle is determined by the input power and the output power of each port. Finally, the losses are calculated, and the efficiency of the proposed ZCMV-MDS is much better than other isolation schemes. Simulation is presented to verify the effectiveness of the proposed scheme.