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This paper presents an open-circuit fault detection method for a grid-connected neutral-point clamped (NPC) inverter system.

Further, a fault-tolerant control method under an open-circuit fault in clamping diodes is proposed. Under the grid-connected

condition, it is impossible to identify the location of a faulty switch by the conventional methods which usually use the distortion

of outputs because the distortion of the outputs is the same in some fault cases. The proposed fault detection method identifies

the location of the faulty switch and the faulty clamping diode of the NPC inverter without any additional hardware or complex

calculations. In the case of the clamping diode faults, the NPC inverter can transfer full rated power with sinusoidal currents by the

proposed fault-tolerant control. The feasibility of the proposed fault detection and the fault-tolerant control methods for the grid-

connected NPC inverter are verified by simulation and experimental results.