Experimental investigation of short-circuit failures in a three level neutral-point-clamped voltage-source converter phase-leg with IGBTs

In the last years, the well known 3L-NPC VSC has been successfully transferred to low voltage high power applications. However, the study of short-circuit failures in a 3L-NPC phase-leg is still missing. This paper presents the theoretical and experimental investigation of short-circuit failures in a three level neutral-point-clamp voltage-source converter (3L-NPC VSC) phase-leg with IGBTs. A categorization of the failures is realized. Due to symmetries, there are only eight different types of failure that have to be investigated. A proposal of how to handle short-circuits in an 3L-NPC VSC IGBT phase-leg is presented.