Concept and Control Strategy for the Grid Friendly Use of Medium Voltage Direct Current Links in German Distribution Grids

In this paper a control strategy for medium-voltage direct current (MVDC) link to increase the flexibility in the distribution grid is presented. An MVDC link is modelled and integrated in the grid model as the connection point of two existing medium voltage distribution grids to develop the control strategy. It is expected that the MVDC link provides an efficient opportunity to allow the control of active and reactive power flow and at the same time decouples voltage control of the two grids. Depending on the grid situation also the power transit over the high voltage grid is reduced. Thus, an increased amount of decentralized and renewable energy sources as well as additional loads can be connected to the existing distribution grid without the need for traditional grid reinforcement. In the considered use case the support of the distribution grid with a large amount of DG capacity is shown by applying the presented control strategy in the simulation model of the two medium voltage distribution grids and applying different load and generation scenarios.