Dual-Functional Dynamic Voltage Restorer to Limit Fault Current

This paper proposes a dual-function dynamic voltage restorer (DFDVR) with fault current-limiting capability. The new topology can operate under different modes: the short-circuit fault current-limiting mode and the compensation mode for voltage fluctuation. Different functions of the DFDVR are achieved by controlling a brake chopper circuit and antiparallel thyristors. During fault conditions, the antiparallel thyristors are deactivated to protect the dc-side capacitor, and the duration of the ON-and OFF-periods of the semiconductor switch in the brake chopper circuit is controlled to adjust fault current amplitudes. During voltage sags, the antiparallel thyristors are activated, and the brake chopper circuit is turned OFF by controlling the gate turn-OFF thyristor in the brake chopper circuit, thus making the DFDVR similar to a conventional DVR. The control scheme and optimal parameter selection of the DFDVR are provided. The design methodology of the DFDVR was verified through simulations performed using the PSCAD/EMTDC software. The experimental results prove the capability and effectiveness of the DFDVR topology.