For systems subject to unbalanced faults, analytical model building for stability assessment is a challenging task. This letter presents a straightforward modeling approach. A generalized dynamic circuit representation is achieved by use of the Laplacian transform variable $s$ . We translate the voltage and current relationship at the fault location into the relationship of three subsystems. The final circuit model is an interconnected sequence network with impedances in the Laplace domain. This circuit can be directly converted from a steady-state sequence network. This modeling procedure is illustrated by an example case of an induction motor served by a grid through a series compensated line. Electromagnetic transient simulation results demonstrate that sub-synchronous oscillations can be mitigated when a single-line to ground fault is applied at the motor terminal. Stability analysis results based on the dynamic circuit corroborate the simulation results. What's more, the derived circuit effortlessly reveals why unbalance can enhance stability.

中文翻译：

---

考虑不平衡拓扑的故障和稳定性分析的拉普拉斯域电路模型

对于存在不平衡故障的系统，稳定性评估的分析模型构建是一项具有挑战性的任务。这封信提出了一种简单的建模方法。通过使用拉普拉斯变换变量实现广义动态电路表示$s$ . 我们将故障位置的电压和电流关系转化为三个子系统的关系。最终的电路模型是一个互连的序列网络，其阻抗在拉普拉斯域中。该电路可直接由稳态时序网络转换而来。该建模过程通过一个由电网通过串联补偿线路提供服务的感应电机示例进行说明。电磁瞬态仿真结果表明，当在电机端子处应用单线接地故障时，可以减轻次同步振荡。基于动态电路的稳定性分析结果证实了仿真结果。更重要的是，派生电路毫不费力地揭示了为什么不平衡可以提高稳定性。