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A New Strategy for Detection and Management of Faults in High Power NPC Converter Systems

Neutral Point Clamped (NPC) converter is often used in high power medium voltage industrial applications. This paper proposes a new fault detection and management method for NPC converters, able to detect any type of power semiconductor device fault and to allow the continuity of operation in case of fault. The fault detection, which is very fast, is based on the measurements of load and clamp-diode legs currents. The fault management strategy is suitable for NPC inverters feeding both passive and active load (such as a three-phase asynchronous motor) supplied by Active Front End (AFE) or Diode Front End (DFE). Finally, a comparison among three different reconfiguring modulations, with special regard to the evaluation of harmonic distortion of the line-to-line voltages and phase currents, is suggested.