Isolated and Nonisolated DC-to-DC Converters for Medium-Voltage DC Networks: A Review

Medium-voltage dc (MVdc) technology is a promising solution to avoid the installation of new ac networks. MVdc can provide optimum integration of large-scale renewable energy sources, the interconnection of different voltage levels of dc and ac grids with the ancillary services. The development in MVdc depends significantly on the dc–dc converters. Such converters support the modern trends of utilizing medium-frequency transformers in power networks. Research on isolated converters technology is in its infancy and limited by the conversion ratio and component ratings. Besides, there is no standards exist covering specific aspects of isolated converter product. Thus, a review of such converters is needed. This work presents, for the first time, a review of the dc–dc power converter families in MVdc grids, including the leading families that are isolated and nonisolated converters, as well as other subfamilies comparing the specifications and characteristics. Also, the applications of these converters are provided by focusing on the essential requirements for each application.