Device and method for starting three-terminal flexible direct-current power transmission system

The invention relates to a device and a method for starting a three-terminal flexible direct-current power transmission system. Three converter stations are arranged in the three-terminal flexible direct-current power transmission system. The device and the method are characterized in that 1), two of the three converter stations are set as sending terminal converter stations, the rest converter station is set as a receiving terminal converter station, and the three converter stations are connection through direct-current lines; 2), the three-terminal flexible direct-current power transmission system is started based on self-excitation pre-charging; in an uncontrollable stage, IGBT (insulated gate bipolar transistor) signals of all high-power switch devices fail to be up namely in a locked state, and sub-module capacitors are charged by serial connection of limiting resistors; and in a controllable stage, the IGBT signals of the high-power switch devices are unlocked to control the sub-module capacitors to be charged continuously, and when capacitor voltage is approximate to a preset level, and limiting resistors are cut off to switch to a normal operating mode; and 3), the three-terminal flexible direct-current power transmission system gradually enters a preset steady-state operation mode under the action of a three-terminal controller, so that the starting process is completed. The device and the method for starting the three-terminal flexible direct-current power transmission system can effectively weaken influences of system starting on the power grid side and have the advantages of logical distinctness, high operability and high reliability.