A SiC & Si Hybrid Four-Level ANPC Converter with Multi-Step Soft-Switching Modulation Achieving Capacitor Voltage Balancing

Abstract

Four-level active-neutral-point-clamped (ANPC) converter has become a research hotspot in academic and industry terms for its features such as lower switching losses, lower voltage stresses on devices, and higher power density than two-level or three-level converters in high-power areas. Nowadays, SiC MOSFET & Si devices hybrid converters have been demonstrated as a high-performance and cost-effective solution. In this paper, a SiC MOSFET & Si devices hybrid four-level ANPC converter is proposed, which requires only two SiC MOSFETs with relatively low blocking voltage in each phase. In order to solve the voltage balancing problem in this circuit, a multi-step soft-switching modulation strategy is then proposed. Implementing the proposed modulation, only SiC devices undertake hard-switching at switching frequency and Si devices are all in soft-switching mode. As a result, the proposed converter has high efficiency but significantly lower cost compared to the all-SiC-MOSFET-based converter in the same topology. The proposed topology and modulation scheme are verified by simulation and experimental results.