针对电力系统中多输入-多输出（multiple-input multiple-output，MIMO）特征带来的稳定性分析挑战，将输入-输出稳定理论与小增益定理引入电力系统稳定裕度计算，构建“系统-扰动”互联反馈框架及稳定裕度量化方法。该方法包含两大核心：一是计算系统最大奇异值，建立能够表征变量耦合特征的MIMO系统鲁棒稳定判据；二是采用小增益定理，建立可显式量化的增益裕度指标，提出了考虑系统不确定性的稳定裕度计算方法。仿真验证结果表明，所提指标在系统动态特性发生复杂变化时，仍能准确反映系统抗扰能力及控制参数对稳定性的影响规律。该方法为电力系统中多类型设备的稳定特性评估提供了统一分析工具，具有重要的理论意义和实际应用价值。

In response to the challenges in stability analysis posed by the multiple-input multiple-output (MIMO) characteristics in power systems, this paper innovatively introduces input-output stability theory and the small-gain theorem into the calculation of system stability margins. A feedback interconnection framework of "system-disturbance" is established, along with a quantitative method for assessing stability margins. The proposed approach comprises two key contributions: first, the computation of the maximum singular value of the system to establish a robust stability criterion for MIMO systems, which effectively characterizes the coupling characteristics among variables; second, the application of the small-gain theorem to develop an explicitly quantifiable gain margin index, thereby enabling the computation of stability margins that systematically account for system uncertainties. Simulation results demonstrate that the proposed index accurately reflects the system's disturbance rejection capability and the influence of control parameters on stability, even under complex variations in system dynamics. This method provides a unified analytical tool for evaluating the stability characteristics of diverse devices in power systems, offering significant theoretical and practical value.