Performance Analysis of Hybrid DC Circuit Breaker based on Counter-Current Injection Method for Low-Voltage DC Grids

Isolating the faults in low-voltage DC grids remains a major technical obstacle in designing the protection system for LVDC grids [1]. Conventional mechanical circuit breakers need to be connected in series to make them compatible for DC grids and they are still not fast enough to disconnect the DC faults with fast rising DC short-circuit currents. In this paper, performance of a hybrid DC circuit breaker topology using a counter-current injection method for producing current-zero switching [2] is analyzed. The topology allows use of a mechanical circuit breaker assisted with power electronic based auxiliary circuit for the switching of DC currents at minimal arcing. A thyristor is used instead of mechanical circuit breaker to enforce switching at current-zero crossing. The circuit breaker topology is simulated in Matlab/Simulink and implemented in hardware for 380Vdc networks. The study analyzes the effect of different circuit elements on the maximum interruption capability and turn-off time of the circuit breaker.