Analysis and solution of the unbalanced device voltage issue for SiC MOSFET based diode neutral point clamped converter

摘要

This paper investigates the unbalanced device voltage issue for SiC MOSFETs based Diode Neutral Point Clamped (DNPC) converter and proposes a snubber based solution to solve this problem. Compared with IGBT, the switching speed of wide band-gap power device SiC MOSFET is much faster. The drain to source voltages Vds of inner switches and outer switches in DNPC are much different due to the fast switching speed. The switching transients of power device in different modulations are analyzed to describe the relation between, parasitic parameters and switching speed . Based on the switching transient analysis, a snubber is applied to clamp the device voltage of inner switches in DNPC. 10kW DNPC bidirectional AC/DC converter is implemented with 1700V SiC devices to verify the analysis and solution.