Medium Voltage Power Switch in Silicon Carbide—A Comparative Study

This paper discusses various solutions of energy conversion in medium voltage using power switches in Silicon Carbide (SiC) technology. In particular, a comparative study is focused on four different variants of an inverter phase leg operating at 1.5 kV DC, which has not been presented in the literature yet. The first one is based on a standard two-level half-bridge built from a 3.3 kV SiC MOSFET power module rated at 450 A. Then, the two-level solution with series-connected devices inside 1.2 kV/450 A power modules is taken into account. Finally, a flying-capacitor phase leg also based on the same 1.2 kV devices is investigated in two different modes: a standard three-level operation and quasi-two-level mode with a significantly reduced capacitor. The presented study is founded on in-depth experiments: all four phase legs were designed, built, and tested in the laboratory. All versions were connected in a half-bridge configuration with an inductive load. Tests were conducted under identical conditions to test the overall performance and switching behavior for various gate resistances. In addition, different aspects are analyzed and compared in this paper, including parasitics, cooling performance, gate drivers and layout considerations, providing selection guidelines for power switches with SiC power devices in medium voltage power electronics applications.