Ground fault protection for DC bus using controlled power sequencing

Abstract

We present a new approach to protect a multi-branch medium-voltage DC bus from ground faults. Behavior analysis of a DC distribution scheme shows that it is possible to quickly de-energize the DC bus by controlling the main converter, open a contactor to remove the faulted line, then re-energize the system. This strategy reduces the out-of-service time and avoids the use of mechanical circuit breakers and their arc-eliminating equipments. The fast response time allows unfaulted loads to ride through the process with minimal local energy storage. Our research shows that it is possible to de-energize, reconfigure, and re-energize a typical industrial DC bus 10–20 times faster than methods traditionally applied in AC circuits, and that only 470 µFarad of bus capacitance is needed for unfaulted circuits to ride-through the process uninterrupted.