Existing impedance-based stability criterion (IBSC) for electromagnetic stability assessment of multiple-grid-connected-inverter (GCI)-based power systems suffers from several limitations. First, global stability feature is hard to be obtained if Nyquist-criterion-based IBSC is used. Second, heavy computational burdens caused by either right-half-plane (RHP) poles calculation of impedance ratios or nodal admittance matrix construction can be involved. Third, it's not easy to locate the oscillation origin, since the dynamics of individual components are missing in the aggregated load and source sub-modules. This article aims to overcome the aforementioned three limitations of the existing IBSC. First, frequency responses of the load impedance and source admittance defined at each node in a selected components aggregation path are obtained by aggregating individual components (e.g., GCIs and transmission lines), from which imaginary parts of RHP poles of these load impedances and source admittances are directly identified without knowing analytical expressions of these load impedances and source admittances. Then, based on the Nyquist plots of minor loop gains (defined as the ratios of the impedance frequency responses of these load and source sub-modules), stability features of these selected nodes are obtained. Finally, if some nodes are unstable, the oscillation origin is located based on numbers of the RHP poles of these load impedances and source admittances. Compared to the existing IBSC, the presented method can assess global stability and locate oscillation origin more efficiently. The local circulating current issue, as a main obstacle of the existing IBSC, can also be identified. Time-domain simulation results in Matlab/Simulink platform and real-time verification results in OPAL-RT platform of a four-GCI-based radial power plant validate the effectiveness of the presented electromagnetic oscillation origin location method.

中文翻译：

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使用组件阻抗频率响应的基于多逆变器的电力系统中的电磁振荡原点定位

现有的基于阻抗的稳定性标准（IBSC），用于基于多电网连接逆变器（GCI）的电力系统的电磁稳定性评估受到一些限制。首先，如果使用基于奈奎斯特准则的IBSC，则很难获得全局稳定性。其次，可能涉及由阻抗比的右半平面（RHP）极计算或节点导纳矩阵构造引起的沉重计算负担。第三，要确定振荡原点并不容易，因为在聚合的负载和源子模块中缺少单个组件的动态。本文旨在克服现有IBSC的上述三个限制。第一，通过汇总单个组件（例如，GCI和传输线），可以获得在所选组件聚集路径中每个节点上定义的负载阻抗和源导纳的频率响应，这些负载阻抗和源导纳的RHP极的虚部直接从中汇总无需知道这些负载阻抗和源导纳的分析表达式即可确定。然后，基于次要环路增益的Nyquist图（定义为这些负载和源子模块的阻抗频率响应之比），可以获得这些选定节点的稳定性特征。最后，如果某些节点不稳定，则根据这些负载阻抗和源导纳的RHP极数确定振荡源。与现有的IBSC相比，所提出的方法可以评估整体稳定性并更有效地定位振荡起源。还可以确定作为现有IBSC的主要障碍的当地循环电流问题。基于Matlab / Simulink平台的时域仿真结果以及基于四GCI的核电站OPAL-RT平台的实时验证结果验证了所提出的电磁振荡原点定位方法的有效性。