Loss Analysis of Three-Level Active Neutral Point Clamped Converter under Fault Tolerance Operation

Abstract

Compared with traditional three-level neutral-point-clamped (NPC) converter, the recently proposed three-level active NPC (ANPC) converter has the ability to overcome the unbalanced loss distribution, and therefore result in increased output power or switching frequency. In industrial applications, fault tolerance ability of power converters is very important considering system availability, safety and reliability. This paper introduced the control schemes to get stable and continuous output under single device fault for both open-circuit and short-circuit fault cases. By analyzing the phase relationship of reference voltage and load current, the loss calculation method under fault tolerant operation was proposed. Calculation results show that the devices junction temperatures under fault tolerant operation are within the safe operation area (SOA) even they are a little bit higher compared to normal operation, which also confirm the effectiveness of the fault tolerant control schemes.