Power sequencing approach to fault isolation in dc systems: Influence of system parameters

We show that medium-voltage dc power buses can be protected against short circuit faults by coordinating the action of a converter that supplies power to the bus with the action of contactors that are used to reconfigure the bus connections. Following a fault, the bus is de-energized (so there is no large current to interrupt), one or more contactors are reconfigured, and the dc bus is then reenergized. For a typical industrial dc bus, we show that it is possible to execute this de-energize-reconfigure-re-energize process 10 times faster than an AC bus can be protected and reconfigured using traditional circuit breakers. We show how the de-energizing and reconfiguring times depend on the output capacitance of the main converter and on the distance to the fault, and we show how to size each hold-up capacitor so that loads on unfaulted circuits can ride through the process uninterrupted.