在低频交流输电系统(Low frequency AC transmission system，LFAC)中，由于海上风电场和陆上交流系统之间频率解耦和信号传输延迟，海上风电场无法及时响应陆上电网频率变化。为此，本文结合系统惯量提出一种提高海上风电场主动频率支撑能力的控制策略。频率信号传递方面，基于模块化多电平矩阵变换器(Modular multilevel matrix converter，M3C)低频侧构网V/f控制策略，结合系统惯量设计了附加频率下垂控制器，建立起M3C网侧与低频侧的频率耦合联系，从而实现两侧频率信息的实时传递。频率支撑方面，当系统发生扰动产生频率偏差时，海上风电机组通过附加下垂控制可调整功率指令值，进而为系统提供频率支撑。最后在MATLAB/Simulink中通过负荷变化和三相交流短路故障的仿真验证了所提协同控制策略的有效性。

In low frequency AC transmission system (LFAC), offshore wind farm is unable to respond to changes in onshore grid frequency in a timely manner due to frequency decoupling and signal transmission delays between the offshore wind power system and the onshore AC system. For this reason, this paper proposes a control strategy to improve the active frequency support capability of offshore wind farms by combining the system inertia. In terms of frequency signaling, an additional frequency sag controller is designed based on the V/f control strategy of the low-frequency-side structure network of the modular multilevel matrix converter (M3C), combined with the system inertia. The frequency coupling link between the M3C net side and the low-frequency side is established, so as to realize the real-time transmission of frequency information between the two sides. In terms of frequency support, when the system is disturbed to generate frequency deviation, the offshore wind turbine can adjust the power command value through additional droop control, thereby providing frequency support for the system. Finally, the effectiveness of the proposed coordinated control strategy is verified in MATLAB/Simulink through the simulation of load change and three-phase AC short circuit fault.