A multi-port interline DC power flow controller

For high voltage direct current (HVDC) grid, the utilization of DC power flow controller can increase the DC current control freedom. This paper proposes a novel multi-port interline power flow controller (MIPFC) based on capacitive energy transfer mechanism (CET). It is constructed by full-bridge sub-modules (SMs) and thyristor valves. The proposed CET-MIPFC presents desirable characteristics such as low cost, high efficiency and small footprint. Firstly, the n-port CET-MIPFC topology is introduced. Afterwards, taking the three-port CET-MIPFC as an example, the topology structure, operation principle, and parameter design are elaborated. Meanwhile, the corresponding control schemes are deliberated to ensure its line current control and energy balancing. Furthermore, simulations are carried out which confirms the validity of the CETMIPFC.