Coordination of active current limiters and hybrid circuit breakers for a MVDC link meshing MVAC distribution grids

This paper presents a protection scheme for a medium voltage dc (MVDC) link, that meshes three different MVAC distribution grids through ac/dc power converters. The proposed scheme includes active current limiters, hybrid circuit breakers and a communication layer for the coordination of these protection devices and power converters (logic selectivity). Active current limiters, installed just after dc bulk capacitors of each power converter, ensure fault current limitation in order to protect the power converters until the fault clearance by dc grid protections. The coordination logic among the protection devices is described in this paper, together with notes on the design of those devices. In case of communication failure, the proposed scheme could not guarantee logic selectivity, but it is anyway able to clear the fault. The effectiveness of the proposed protection strategy is validated in a fast transients simulation environment, using detailed model of power electronic converters.