A Self-Voltage Balanced Hybrid Three-Level MV Inverter Using 3.3-kV SiC MOSFET Module With False-Trigger-Proof Design

Abstract

This article presents a self-voltage balanced three-level (3L) active-neutral-point-clamped (ANPC) medium-voltage (MV) inverter. Two switches of this inverter operate at high frequency (HF), while four switches operate at low frequency (LF), which is suitable to be implemented with hybrid “Si IGBTs + SiC MOSFETs” for MV applications. A 3.3-kV SiC MOSFET power module with low parasitic packaging is applied as HF switches, and the dc-link capacitor voltages can be self-balanced through periodic charging/discharging processes with a small decoupling capacitor. However, the inrush current occurs during voltage balancing processes, resulting in the false trigger of desat protection for LF switches. In this article, the mechanism of inrush current during voltage balancing processes is analyzed and a 3L gate driving method is proposed for LF switches to solve the false-triggering issue and improve the inrush energy loss distribution. In addition, high dv/dt of SiC switching transients may cause the false-triggering issue of HF switches, and desat protection design equations are therefore derived for this 3.3-kV SiC MOSFET power module to achieve a fast (< 440 ns) short-circuit response and maintain a good noise immunity to high dv/dt. A 4-kV dc, 40-kVA inverter prototype is built in the laboratory and the experimental results are provided to verify the proposed methods.