A ZVS-PWM Scheme for Three-Phase Active-Clamping T-Type Inverters

For increasing power density and other performance of T-type three-level inverters, the soft-switching technique is studied. This article proposes a novel zero-voltage switching (ZVS) PWM scheme for active clamping three-phase T-type inverters, which can realize the ZVS operation of all switches and reduce the switching loss. The proposed ZVS PWM scheme is evolved from discontinuous PWM and modified for the requirements of T-type inverter. It enables all switches, including main switches and auxiliary switches, operate at a fixed frequency. However, a larger current on the power semiconductor devices occurs at 60° zone transition. To suppress this current surge, the carriers used in the ZVS PWM scheme are phase shifted. Finally, the novel ZVS PWM scheme is verified on a 10 kW/150 kHz SiC-based ZVS T-type inverter prototype.