A Current Flow Controller with Independent Regulation Capability for HVDC Grid

With the increasing significance of renewable energy and demand for long-distance power transmission and large-scale gridinterconnection, developing and expandinghigh voltage direct current (HVDC) grids have become essential. However, in multi-terminal or meshed DC grids, controlling the current flow of each line through converter stations is not completely feasible. The line current flow regulation devices used in AC grids cannot be applied in DC grids straightforwardly. Therefore, in order to implementcomplete power flow control in HVDC grids, DC current flow controller (DCCFC) becomes indispensable. As the state-of-the-art interline DCCFCs need to exchange power between multiple lines, this paper presents a DCCFC topology that can be used in multi-terminal DC grids and which can achieve independent control and bidirectional regulation. The operation principle and control strategy of the proposed DCCFC are studied, with simulation results of steady-state and dynamic response presented to validate the theoretic analysis.