Open-Switch Fault Analysis of Three-Level Neutral Point Clamped Inverter

Multi-level inverter replaces the conventional two-level inverters in high and medium power applications due to their better output waveform quality, low stress on switches, and working independent of dynamic switching characteristics of individual switches. The chance of open-switch failure is high in multi-level inverter due to large number of switches. A prolonged open-switch failure may inversely affect the efficiency of drive system and may also leads to short-circuit failure. For a renowned fault detection and fault tolerant control implementation, the open-circuit fault and its effect had to be clearly studied. In this paper, the single switch open circuit failure analysis of three-phase three-level neutral point clamped (NPC) inverter is performed. The failure effects on output phase voltage, line voltage, line current, pole voltage, and DC-link capacitor voltage are studied.