Evaluation of DPWM schemes for Si/SiC three-level hybrid active NPC inverters

The hybrid utilization of SiC and Si devices can achieve a trade-off between the efficiency and cost of three-level active neutral-point-clamped (3L-ANPC) inverters. This paper studies a three-phase 2-SiC 3L-hybrid ANPC (3L-HANPC) inverter with different discontinuous pulse width modulation (DPWM) schemes. The principles of these DPWM schemes are analyzed in detail, and carrier-based algorithm for two of the DPWM schemes are given. Finally, a 6 kW three-phase 2-SiC 3L-HANPC inverter prototype was built to compare these two modulation schemes. Experimental results show that DPWM1 with its peak voltage-clamped can achieve a higher efficiency than DPWM2 with its zero-crossing clamped. However, the DPWM2 scheme has a lower THD than the DPWM1 scheme. Since the THD improvement contributed by the DPWM2 scheme is relatively small, the DPWM1 scheme is the preferred DPWM scheme.