随着负荷类型多元化及新能源装机比例上升，源荷之间的功率波动增加了未知的随机扰动，电力系统频率响应复杂多变。为此提出随机-阶跃双扰动下考虑随机频率安全的机组组合，涵盖以频率置信区间下限为表征的频率安全约束。基于带权值非线性最小二乘法对多机频率响应模型进行拟合，得到等效单机频率响应模型。基于随机线性系统理论，通过等效单机频率响应模型构建包含频率的系统状态空间模型，确定状态变量初值，揭示状态变量初值对大功率阶跃扰动与随机扰动叠加下随机频率响应影响，推导频率安全指标最严重的频率置信区间。IEEE 24节点算例与实际系统算例验证了所提方法的有效性，量化了不同权重、随机扰动与初始状态、新能源占比的影响。

With the diversification of load types and the increase of the proportion of new energy installed capacity, the power fluctuation between source and load increases the unknown random disturbance, which makes the frequency response of power system more complex and unpredictable. Therefore, a unit commitment method considering random frequency safety under the Random-step-dual-disturbance method is proposed. The frequency safety constraint represented by the lower limit of frequency confidence interval is covered. Based on nonlinear least square method with weight, the multi-machine frequency response model is nonlinear fitted, and the equivalent single-machine frequency response model is obtained. Based on the stochastic linear system theory, a system state space model including frequency was constructed for the equivalent single-machine frequency response model to determine the initial value of the state variables. The influence of the initial value of the state variables on the random frequency response under the superposition of high-power step disturbance and random disturbance is revealed, and the frequency confidence interval of the most serious frequency safety index is deduced. The IEEE 24 test system and Actual test system verifies the effectiveness of the proposed method and quantifies the effects of different weights, random disturbance and initial states, and the proportion of new energy sources.