In islanded systems with droop-controlled inverters, small-signal stability is a subject of major concern. The electromagnetic (EM) dynamics of the lines have a significant effect on the stability, limiting the maximum values of the droop gains. In past works, this effect has either been neglected or merely observed through eigenvalue plots. In this paper, the impact of the line dynamics is formally analyzed to identify the destabilizing effects so that they can be mitigated for a generic system. For this, a novel approach is employed, using the generalized droop control whereby the observed instability purely corresponds to the effect of line dynamics. The effect of the potential instability factors, viz., distribution system lag factor, EM-induced cross-coupling and EM-induced damping on the critical system modes are studied. A theory-based design is proposed for the power measurement filter for mitigating these effects. The resulting closed-loop model is derived, demonstrating guaranteed stability for all droop gains and R/X ratios. The proposed filter design is validated through simulation and experimental case studies.

中文翻译：

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缓解由下垂控制的多逆变器系统中的线路动态引起的稳定性问题

在具有下垂控制逆变器的孤岛系统中，小信号稳定性是一个主要问题。线路的电磁 (EM) 动力学对稳定性有显着影响，限制了下垂增益的最大值。在过去的工作中，这种影响要么被忽略，要么只是通过特征值图观察到。在本文中，对线路动力学的影响进行了正式分析，以确定不稳定的影响，以便可以减轻通用系统的影响。为此，采用了一种新颖的方法，使用广义下垂控制，由此观察到的不稳定性完全对应于线动力学的影响。研究了潜在的不稳定因素，即配电系统滞后因子、电磁感应交叉耦合和电磁感应阻尼对临界系统模式的影响。提出了一种基于理论的功率测量滤波器设计，以减轻这些影响。得出的闭环模型证明了所有下垂增益和 R/X 比的稳定性保证。提议的滤波器设计通过模拟和实验案例研究得到验证。