ZVRT Capability of Single-Phase Grid-Connected Inverter With High-Speed Gate-Block and Minimized LCL Filter Design

This paper proposes a zero-voltage ride-through (ZVRT) method and an LCL filter design method to meet the fault ride-through (FRT) requirements for a single-phase grid-connected inverter with a minimized LCL filter. A high inverter output current overshoot occurs at a grid voltage sag and a grid voltage recovery, when a low-inductance LCL filter design is employed in order to minimize the filter volume. In order to suppress the current overshoot, a high-speed gate-block operation and the design method of the minimized LCL filter are proposed. In particular, the filter design considers the delay time in the gate-block operation in order to clarify the reduction limitation of the inductance in the LCL filter. As a result, the maximum inverter output current overshoot is suppressed to 146% by the high-speed gate-block operation and the designed LCL filter, where the impedances of an interconnected inductor and a filter inductor are 1.0% and 0.78% of the inverter normalized impedance, respectively. Therefore, it is possible to meet the FRT requirements with the proposed ZVRT method even with the minimized LCL filter.