FRT capability of single-phase grid-connected inverter with minimized interconnected inductor

Abstract

This paper proposes a fault-ride-through (FRT) method for a single-phase grid-connected inverter with a minimized inductor by reducing the inverter output current overshoot. When a low-inductance interconnected inductor is used, the inverter output current overshoot becomes very high at a voltage sag and a voltage recovery. Therefore, a grid-voltage fault stops the operation of the grid-connected inverter due to an overcurrent protection. In the proposed method, the current overshoot is suppressed by using a momentary gate-block with a high-performance disturbance observer. Moreover, the inverter output current in steady state is also stabilized by using the high-performance disturbance observer. Consequently, by using the proposed method, the grid-connected inverter continues to operate without interruption during the fault of the grid voltage. The maximum overshoot rate of the inductor current at the voltage recovery moment after fault clearance is reduced from 534% in the conventional method to 46.5% in the proposed method.