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This paper proposes a fault-detection method for an open-switch fault in the switches of grid-connected neutral-pointclamped

inverter systems. The proposed method can not only detect the fault condition but also identify the location of the faulty switch. In

the proposed method, which is designed by incorporating a simple switching control in the conventional method, the fault condition

is detected on the basis of the radius of the Concordia current pattern, and the location of the faulty switch can be identified. By

using the proposed method, it is possible to detect the open-switch fault and identify the faulty switch within two fundamental

periods, without using additional sensors or performing complex calculations. Simulations and experiments are carried out to confirm

the reliability of the proposed fault-detection method.