A new fault detection method for NPC converters

Neutral Point Clamped (NPC) converter topology is one of the most widespread static conversion structures used in high power medium voltage industrial applications. In recent years, fault tolerance has become one of the most interesting features which could be requested by the market, in order to improve plants reliability and availability, thus avoiding, for example, the stop of means of transport and/or plants. This paper proposes a new fault detection method for NPC converters, able to detect any type of power semiconductor device fault. The fault detection, which is very fast, is based on the measurements of load and clamp-diode legs currents and avoids the use of gate-unit feedback signals and voltage measurements across each component.