In the islanded micro‐grids the power cannot be exchanged by the upstream network and the system inertia level is low. Therefore, the network sensitivity to disturbances and load changes is more than the connected mode. In such situation, the system states can behave with more degree of freedom and have less dependency to total system dynamic. The variety of equipment with different dynamics and the load level uncertainty leads to continuous changes in the islanded micro‐grid operating point. These changes are more considerable in the islanded micro‐grid due to lack of inertia and limited stability margins. Therefore, the determination of appropriate model order for system in such way that the reduced order model keeps the essential dynamic behavior and neglects the less effective modes, is critical. Therefore, in this paper a three‐step method based on multi‐time scale theory and singular perturbation method is proposed for optimum model order reduction in islanded micro‐grid. The proposed method is applied to a typical micro‐grid with different types of DGs and loads. The load level uncertainty is modeled by probability density function (PDF) and reduced order model of system is validated in different operating scenarios by sensitivity analysis, participation factor investigation and time domain simulation.

中文翻译：

---

多时间尺度理论对降阶微电网的动态稳定性分析

在孤岛微电网中，上游网络无法交换功率，并且系统惯性水平很低。因此，网络对干扰和负载变化的敏感性比连接模式高。在这种情况下，系统状态可以表现出更大的自由度，并且对整个系统动态的依赖性较小。各种具有不同动力学和负载水平不确定性的设备会导致孤岛微电网工作点不断变化。由于缺乏惯性和有限的稳定裕度，这些变化在孤岛微电网中更为明显。因此，以降阶模型保持必要的动态行为并忽略不太有效的模式的方式确定系统的适当模型顺序至关重要。所以，本文提出了一种基于多时间尺度理论和奇异摄动法的三步法，以减少孤岛微电网中模型的最优阶数。所建议的方法适用于具有不同类型的DG和负载的典型微电网。通过概率密度函数（PDF）对负荷水平的不确定性进行建模，并通过敏感性分析，参与因子调查和时域仿真来验证系统在不同操作场景下的降阶模型。