Critical-mode-based soft-switching modulation for three-phase inverters

In this paper, a new critical-conduction-mode (CRM)-based modulation is proposed for three-phase inverters. With this modulation, soft switching is achieved and the efficiency of the inverter is improved, especially for high frequency operation with SiC MOSFET. In three-phase string PV inverter applications, by operating at switching frequency above 300 kHz, power density of the inverter is estimated to be at least three times higher than commercial products, while peak efficiency is estimated to be about 99%. Good performance of this proposed modulation is verified with simulation analysis. The results are also experimentally verified on a 25 kW SiC-based three-phase inverter prototype with 80W/in
³
power density, and 98.9% peak efficiency is achieved with non-interleaved operation.