Power Flow Control by Serial DC/DC Converters in DC Grids

The structural design of future DC distribution grids is influenced by the equipment used as well as its operation methods. Power electronic converters promise potential for voltage and power flow control at the system interfaces to other DC grids, neighboring AC grids or grid customer systems. Serial DC/DC converters within DC grids could provide additional capability for power flow control and therefore offer operational benefits to the grid. Within this paper, the modelling of serial DC/DC converters for quasi-stationary system analysis is described. The novel equipment is integrated in a power flow and an optimal power flow (OPF) calculation using a second order cone programming (SOCP) relaxation. A method for the positioning of these components in order to eliminate limit violations in future meshed DC grids is presented. The benefit of additional power flow control capability for MVDC grids is investigated in two case studies.