Transient Voltage Suppression Strategy of New Energy System through Flexible DC Considering Multi-resource Cooperation

In the high-voltage DC power grid connected to large-scale wind power, in response to the problem of wind turbine cascading disconnection caused by significant fluctuations in AC voltage at the supply end after a DC fault occurs, the internal mechanism of wind turbine cascading disconnection caused by DC faults is explored. Local and global transient voltage rise severity indicators based on multiple binary tables under fault are proposed as starting conditions for the coordinated suppression strategy of transient over-voltage. Then, for the active part, an improved DC energy consumption device topology and switching strategy based on thyristors were proposed; For the reactive power part, a control strategy based on the coordination between the converter station side condenser and the wind farm side SVG is proposed to suppress the disconnection of high-voltage DC supply end wind turbines. During different periods of DC blocking, according to the characteristics of voltage changes at the supply end, the condenser's spontaneous reactive response ability, excitation control ability, and SVG reactive power regulation ability are utilized at different times to suppress transient voltage drop or transient voltage rise exceeding the protection threshold of wind turbine disconnection. The correctness and effectiveness of the proposed method have been verified through simulation.