换流器型电源具有控制灵活、响应快的优点，利用其储能可实现对系统频率的快速支撑。针对现有方法缺乏控制对频率最低点影响的量化分析、无法在不同条件下有效提升频率最低点等问题，本文提出了一种基于功率阶跃控制的频率支撑策略，旨在提升频率最低点。首先，分析了功率阶跃控制下系统的频率响应，推导了受扰后两次频率下跌时频率最低点的解析表达式。基于该表达式，结合各风机可释放的转子动能确定了功率阶跃控制的最优参考值，实现了多风机附加功率的协调分配。最后，在MATLAB/Simulink上搭建了测试系统模型，数值仿真结果验证了所提策略的有效性。

The converter interfaced power sources has the advantages of flexible and fast response, the energy stored in its rotating masses can be released to realize fast system frequency support. Most of the existing control strategies pay less attention to quantitative analysis of how control strategies affect the frequency nadir, and fail to effectively enhance the frequency nadir under any conditions. Aiming at improving the system frequency nadir, a frequency support strategy based on step power control is proposed. Firstly, the system frequency response under step power control is analyzed, and the analytical expressions of the two frequency nadirs following the disturbance are derived further. Then, the optimal reference of power step control is determined by combining the kinetic energy that can be released by each wind turbine generators and a coordinated distribution of the additional power is realized based on the expressions. Finally, a test system is built on MATLAB/Simulink. The effectiveness of the proposed strategy is verified by numerical simulation results.