Flexible power flow control for next-generation multi-terminal DC power network

To realize massive integration of distributed renewable energy resources in future power system, the development of efficient measures for their integration is required. Using DC grid is more efficient and more compatible for the integration of renewable energy resources and energy storage devices. In the next-generation DC power network, many kinds of nodes which consist of generators, loads, energy storage devices, and so on and links (distribution lines) are connected. Thus, the grid structure is complex, and flexible power flow controls are essential. In a DC distribution network, the only controllable parameter is voltage of nodes, thus it is difficult to control the power flow of each link independently. In this paper, we study a power flow control on the links named link voltage control based on a bidirectional buck-boost converter implemented on the link. In addition to the voltage difference between the nodes, the link voltage controller generates additional voltage difference on the link intentionally. Thus, it is possible to control power flow of a specific link independently without affecting power flow of other links. In this way, flexible controls of power flows in a multi-terminal DC power network become possible. The effectiveness of the power flow control is demonstrated by experiments. The high controllability of the link voltage controller will contribute to the realization of future DC power grid.