Recently, a high-frequency resonance (HFR) incident has been captured in an actual HVDC project of China Southern Power Grid, which is regarded as a new stability issue caused by the interaction between the modular multilevel converter (MMC) and the weak ac grid. To investigate this event, this paper proposes a stability analysis method based on the frequency-coupling impedance model (FCIM). First, the FCIMs of the MMC and the ac grid are established in abc-frame individually with the frequency coupling effect of the MMC taken into account. Next, they are aggregated into a two-by-two impedance matrix by numerical calculation. Then, based on the aggregated FCIM, a criterion is developed to locate the HFR modes and to evaluate their stability. Finally, the results obtained from FCIM-based analysis are verified by electromagnetic transient (EMT) simulations as well as the field measurements.

中文翻译：

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基于频率耦合阻抗模型的实际 MMC-HVDC 系统中高频谐振事件的分析

近日，南方电网某HVDC项目中捕获到一起高频谐振（HFR）事件，被认为是模块化多电平换流器（MMC）与弱交流电网相互作用引起的新的稳定性问题。 . 为了研究这一事件，本文提出了一种基于频率耦合阻抗模型（FCIM）的稳定性分析方法。首先，考虑到MMC的频率耦合效应，MMC和交流电网的FCIM分别建立在abc-frame中。接下来，通过数值计算将它们聚合成一个 2×2 的阻抗矩阵。然后，基于聚合的 FCIM，开发了一个标准来定位 HFR 模式并评估它们的稳定性。最后，