Open-circuit fault detection method for Grid-side Three-level NPC Inverter

Reliability of power electronics is one most critical challenge to face in order to improve the reliability of wind turbine system (WTS). As the power of the wind turbine is increasing, different topologies of power converters are developed for wind turbine applications. The three-level Neutral-Point Clamped (NPC) converter is widely used in WTS, since it has many advantages like a large output capacity, high output voltage and low current Total Harmonic Distortion (THD). However, the topology of these converters has a large number of switches which are fragile components. Open circuit is one of the most common failures in these converters and causes considerable economic damage in wind power systems. This paper presents an open-circuit fault diagnosis method for a three-level NPC inverters based on current and charge distortion in the output of the inverter. The operation of the NPC inverter under normal and open-circuit fault are analyzed. Simulations results of the converter control and the fault diagnosis method are presented and discussed.