Coordination control method for multi-terminal flexible DC power transmission system

The invention relates to the technical field of flexible DC power transmission, particularly relates to a coordination control method for a multi-terminal flexible DC power transmission system, and especially relates to a control method for a multi-terminal converter station flexible DC power transmission current converter of more than three terminals. The method comprises the following steps that (1) in the multi-terminal flexible DC power transmission system, direct current regulated sagging slope control is additionally arranged in constant DC voltage stations; (2) DC voltage regulated sagging slope control is additionally arranged in constant active power stations; and (3) when there is no communication between the stations, the two constant DC voltage stations in the multi-terminal system are set as constant DC voltage control stations, and the constant DC voltage control stations act as balance nodes in a DC network. Constant DC voltage station controllers are optimized. When the operation state of the system exceeds range of regulation of the only DC voltage sagging slope control, the DC network is enabled to still maintain the optimal voltage level after occurrence of a severe fault through the optimal target regulation system DC voltage and power of each station.