A Novel Modulation Method with Simultaneous Reduction of Common-Mode Voltage and Switching Losses for Three-Level SNPC Inverter

The three-phase three-level (3-L) sparse neutral point clamped (SNPC) inverter is representing a promising alternative for motor drives and three-phase PFC rectifier systems. For the operation of these applications, the common-mode (CM) voltage is needed to be reduced. However, conventional modulation schemes with reduced CM voltage leads to high switching losses of the 2-L inverter stage. To address this issue, a novel modulation method based on zero vector transitions is proposed in this article. The proposed method reduces CM voltage amplitude to Vdc/6, and achieves zero switching loss of the 2-L inverter stage. The switching state sequence is determined, and the vectors dwell-time calculation is reconsidered. Finally, the proposed modulation method is verified by the experiment using a 1.5-kW hardware prototype.