海上风电低频输电系统低频侧不对称故障控制策略

Asymmetric faults of low-frequency submarine cable will lead to risks of overcurrent of power electronic devices in modular multilevel matrix converter（M3C） and overvoltage in the non-fault phase，which brings great challenges to offshore wind power low frequency transmission system（LFTS）. To solve the above problems，a control strategy for asymmetric fault of submarine cable is proposed based on excellent controllability of power electronic equipment in M3C. The low-frequency side voltage of M3C is adjusted dynamically according to the fault severity to avoid overvoltage in the healthy phase. Meanwhile，to limit the amplitude of short circuit current and protect power devices from overcurrent，the negative-sequence current is suppressed by sub-converters. Then the fault equivalent model is derived for fault analysis with taking the influence of control strategy into account. The model of offshore wind power LFTS is built in PSCAD／EMTDC. The simulative results validate the effectiveness of the proposed control strategy and fault analysis method. The strategy can realize stable operation of the system under asymmetric fault of low-frequency side.