Protection in DC networks has long been a complex challenge, often cited as a major barrier to their widespread adoption. The presence of large DC-link capacitors and the replacement of traditional transformers with power electronic converters result in fault current rise rates that are tens to hundreds of thousands of times higher than those in AC grids. Despite this, conventional DC protection strategies are largely borrowed from the traditional AC protection mindset. In DC networks, the inclusion of large link capacitors renders the series insertion of circuit breakers, similar to AC network practices, suboptimal, as breakers must interrupt fault currents injected from multiple sources with varying escalation time constants. Existing DC circuit breaker technologies also inherently struggle to simultaneously achieve high interruption speed, minimal size, and low cost. Consequently, relying on a single circuit breaker does not necessarily offer an optimal solution in terms of speed, cost, or compactness. This paper investigates fault propagation mechanisms in common power electronic converter topologies and proposes a novel protection strategy based on the coordinated use of multiple circuit breakers with varying interruption speeds. The proposed approaches are also validated through comprehensive simulations.
Ghadrdan et al. (Wed,) studied this question.