海上风电经VSC-HVDC系统受端电网不对称故障抑制策略

海上风电经柔性直流输电技术（即基于电压源换流器的高压直流输电系统，VSC-HVDC）送出系统中受端电网故障不仅影响受端换流站交直流侧系统的运行状态，严重情况下也会阻碍送端换流站和海上风电机组的正常运行。针对这一实际问题，分析了海上风电经VSC-HVDC送出系统中受端电网发生不对称故障的传播机理，提出了一种基于Lyapunov函数方法的负序分量抑制策略。首先，建立了海上风电机组经VSC-HVDC送出系统的拓扑结构，并分析了受端电网发生不对称故障的传播机理。其次，根据受端换流站的数学模型推导出满足Lyapunov函数全局稳定性的负序开关函数，并求解出开关函数的系数，进一步设计出相应的Lyapunov函数控制器。最后，基于MATLAB/Simulink软件仿真将所提策略与传统PI控制进行对比，验证了所提策略的正确性和有效性。

Suppression Strategy for Asymmetric Faults in the Receiving-End Grid of Offshore Wind Power Through VSC-HVDC System

The failure of the receiving-end grid in the voltage source converter (VSC) based high voltage direct current (HVDC) system of offshore wind power not only affects the operation status of the AC/DC side system of the receiving end converter station, but also hinders the normal operation of the sending end converter station and offshore wind turbines in severe cases. In order to solve this problem, the propagation mechanism of asymmetric faults in the receiving-eng grid of offshore wind power transmission system through VSC-HVDC was analyzed, and a negative sequence component suppression strategy based on Lyapunov function method was proposed. Firstly, the topology structure of the offshore wind turbine transmission system through VSC-HVDC was established, and the propagation mechanism of asymmetric faults in the receiving-end grid was analyzed. Secondly, based on the mathematical model of the receiving-end converter station, a negative sequence switching function that satisfies the global stability of the Lyapunov function is derived, and the coefficients of the switching function are solred. Thus, the corresponding Lyapunov function controller is further designed. Finally, the proposed strategy was compared with traditional PI control based on MATLAB/Simulink software simulation to verify its correctness and effectiveness.