A Triple Interline DC Power Flow Controller with Dual-Freedom Control Function

In meshed HVDC grids, the power flow distribution has a significant influence on the operational safety of electrical system. Independent power flow controllers are essential since voltage source converters cannot accurately control the power flow of each branch. A triple interline DC power flow controller (TI-DCPFC) with dual-freedom control is proposed in this paper. First, the power flow ranges of each line in a 4-terminal HVDC grid where an interline DC power flow controller (IDCPFC) and a TI-DCPFC is installed separately, are analyzed. It verifies that extended power flow controllers enlarge the controlling diversion. Then, a new topology of TI-DCPFC with dual-freedom control is proposed and its operational modes as well as control strategy is discussed. Finally, the performance of TI-DCPFC applied in a 4-terminal meshed HVDC grid in different cases is tested by a series of simulations.