The dc-side admittance of a modular multilevel converter can be used in assessing the stability of the dc system by means of impedance-based stability criteria. An accurate mathematical representation of the small-signal admittance can be given using harmonic linearization. To this end, the effect of the internal dynamics of the converter, e.g., the circulating current, the converter control scheme, and the controller parameters on the admittance of the converter should be analyzed. In this article, a linear analytical model for the dc-side admittance of the converter is derived based on a combination of harmonic linearization and frequency-domain representation, which incorporates different control schemes. Moreover, an admittance model is given for the closed-loop voltage control mode of the converter, where the ideal insertion indices are applied. To this end, the impact of an arm-balancing controller and its parameters on the dc-side admittance of the converter is investigated. Finally, experiments are carried out on a down-scaled prototype to validate the accuracy of the analytical model.

中文翻译：

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闭环电压控制下模块化多电平转换器直流侧导纳的建模和整形

模块化多电平转换器的直流侧导纳可用于通过基于阻抗的稳定性标准评估直流系统的稳定性。小信号导纳的准确数学表示可以使用谐波线性化给出。为此，应分析转换器内部动态特性，例如循环电流，转换器控制方案和控制器参数对转换器导纳的影响。在本文中，基于谐波线性化和频域表示的组合，得出了转换器直流侧导纳的线性分析模型，该模型结合了不同的控制方案。此外，给出了转换器的闭环电压控制模式的导纳模型，应用理想插入索引的位置。为此，研究了臂平衡控制器及其参数对转换器直流侧导纳的影响。最后，在缩小的原型上进行实验以验证分析模型的准确性。