Mitigation of Power Flow Congestion in a meshed DC grid with controllable DC Series Voltage

The growing load demand and the higher penetration of renewable energy in a meshed DC grid in future may overload its existing transmission system, namely the Power Flow Congestion (PFC). The PFC can be mitigated either by installing additional transmission reinforcements or by better utilizing the existing transmission infrastructure. For the latter, this paper proposes a novel application of a controllable DC Series Voltage (DCSV) to solve the congestion problem. The DCSV can be inserted in series with any transmission path (cables/overhead lines) enabling it to directly control the current or power flowing through it. This in turn relieves the overloaded transmission paths in the other parts of the system. Load flow and dynamic simulations are carried out in DIgSILENT PowerFactory and in PSCAD respectively to show the feasibility of this concept in a meshed DC grid, as well as the impacts on system losses and line voltage drop. The post outage control of DCSV and its impact on power flows through transmission paths are also studied and briefly reported.