Protection devices against DC fault in a back-to-back converter applied to distribution grids

This paper considers the possibility to connect two medium voltage primary distribution grids through a DC connection realized by two AD/DC converters in back-to-back configuration. In particular, after a description of the whole system, the effects of a bolted or non-bolted DC fault are analyzed. Then, an active current limiter is proposed to limit the fault currents and keep the controllability of the system. Such a system is then modeled and studied through many simulations that confirm the effectiveness of the proposed current limiter.