A DC Power Flow Controller for Multi-Terminal DC Grids

A HVDC grid based on voltage source converter (VSC) is an attractive solution for the grid integration of offshore renewable energy, interconnection of ac grids, facilitation of power markets, and energy emergency support. However, the power flow within the dc grids is determined by the line resistance and cannot be fully controlled by the VSCs only. Thus, power flow control of dc grids are needed not only to realize the economic operation and power markets, but also to prevent overload of dc lines in post-fault conditions. Four types of control devices, dc transformer, the variable resistor, series voltage source and interline dc power flow controller (IDCPFC) are presented to achieve the goal of power flow controlling. This paper presents a dc power flow controller (DCPFC) based on dc converter. This DCPFC can be extended to multi-terminal power flow control in dc power grids. The operation principle of the proposed DCPFC is analyzed. And the theoretical analysis is validated by a full-scaled simulation.