Piloting Medium-voltage Direct Current (MVDC) in Distribution Grids in Germany – Use Cases and Planning

This paper describes the motivation, planning, location and expected operation of a medium-voltage direct current (MVDC) back-to-back converter to increase flexibility in the distribution grid. The MVDC back-to-back system is expected to provide a unique opportunity to allow active power flow control as well as decoupled voltage control on both sides of the system in one single installation. Two possible use cases for the MVDC back-to-back converter in distribution grids are presented: 1) integration into a medium-voltage (MV) feeder for improved power quality and 2) connection of normally open points or subnetwork coupling. Both use cases ultimately offer the possibility of integrating an increased number of decentralized and renewable energy sources as well as new loads to the distribution grid and reduce undesired transits over the high voltage grid. In a selected region four feasible locations for the pilot have been identified and evaluated. The result are two locations which allow the application of both use cases, respectively, and an outlook regarding further planning and testing is given.