Quasi-bridge-type fault current limiter for mitigating fault transient phenomena

This study proposes a quasi-bridge-type fault current limiter (QBT-FCL) for reducing the fault current level and the magnitude of voltage sag. Before a fault occurs, because of the voltage-compensation effect, the equivalent impedance of the QBT-FCL is very low, and hence it has almost no influence on the circuit. Therefore, the load seems to directly connect to the voltage source, and there is almost no distortion to the load voltage and current waveforms. When the fault occurs, the limiter automatically inserts the impedance into the circuit, and thus the magnitude of the fault current and voltage sag can be effectively reduced. After the fault is cleared, the limiter starts to freewheel and recovers to the normal operation state. As a result, the QBT-FCL still has a negligible effect on the circuit and is ready for the next fault occurrence. Theoretical analysis for the proposed QBT-FCL has been fully developed in this study. Finally, the feasibility and performance of the proposed limiter have been verified by the simulated and experimental results.