Improving DC Circuit Breaker Performance Through an Alternate Commutating Circuit

Fault interruption in de circuits is more challenging than in their ac counterparts. The absence of natural current zero crossing along with resistive nature of the dc grids creates a significantly higher fault current to disrupt at the dc circuit breakers. Available approaches to break dc fault currents include creating forced zero-crossing current at the breaker or employing solid-state circuit breakers. This paper summarizes the current dc breaker technologies and proposes a new alternate method. The proposed mechanism is a mechanical circuit breaker that utilizes two switches, of which one generates zero-crossing with an alternate oscillatory circuit for the other one, which can be a conventional zero crossing-based ac breaker and is used in the main circuit. This is different than the conventional single-switch commute-and-absorb method currently used. It is shown that the proposed oscillatory circuit improves the fault current extinction and significantly reduces the voltage rate-of-change while creating the current zero-crossing faster, when compared to the available technology. Thus, the proposed mechanism is capable of interrupting high de currents with minimal arc through a less expensive ac circuit breaker. Simulation and hardware results are provided to show the efficiency of the proposed breaker.