A Load-Independent Controllable Z-Source Circuit Breaker With an Intrinsic Fault Detection Method

The Z-source circuit breaker using thyristor as the main switch benefits from its low cost, low conduction loss, and high ruggedness. However, the fault protection of the conventional Z-source circuit breakers only relies on the change of the load. In this article, a load-independent controllable Z-source circuit breaker (CZCB) with an intrinsic fault detection circuit is proposed. It will not be protected by mistake during any load step change, and an accurate fault current detection can be achieved with a specific threshold. Meanwhile, the fault current is monitored by the on-state voltage of the main thyristor, so no additional sensor is needed. An auxiliary thyristor is used to turn off the main thyristor reliably when an overcurrent is detected. In addition, only one inductor is needed in the CZCB, and the L-C parameter is much smaller than the conventional Z-source breakers, leading to lower size and cost. The performance of the proposed CZCB is verified by simulation and experiment. The results show that the fault current can be cleared within a few microseconds, and the total fault isolation time is only about 38 mu s.