MMC-HVDC直流侧阻抗模型简化方法

目前大多数模块化多电平换流器(MMC)的阻抗模型过于复杂，而已有的模型简化方法大多针对时域状态空间模型，不便于谐振分析。因此，以定有功功率控制和定直流电压控制的MMC为例，提出MMC直流侧阻抗模型简化方法。首先对MMC直流侧阻抗进行详细建模，根据分析得到的等效电容在高频段的旁路特性，保留低频段下的阻抗详细模型，忽略对整体阻抗特性几乎没有影响的部分，实现阻抗模型的简化，并基于简化模型提取阻抗特性的关键影响参数进行稳定性分析。最后基于PSCAD/EMTDC平台进行仿真验证，仿真结果验证了所提简化阻抗模型的准确性，以及关键参数对系统稳定性影响的分析结果。

DC-side impedance model simplification method of MMC-HVDC

Most of the current impedance models of MMC(Modular Multilevel Converter) are too complicated, while the existing model simplification methods mainly focus on time-domain state-space models, which is inconvenient for resonance analysis. Thus, a DC-side impedance model simplification method of MMC is proposed, where the MMCs with fixed active power control and fixed DC voltage control are illustrated as examples. Firstly, the detailed DC-side impedance model of MMC is established. According to the bypass characteristic of the equivalent capacitor in high-frequency domain through analysis, the detailed impedance model in low-frequency domain is remained, and the model parts barely affecting the overall impedance characteristic are ignored, so that the impedance model is simplified. Based on the simplified model, the key impact parameters for the impedance characteristics are identified for stability analysis. Finally, simulation in PSCAD/EMTDC platform is conducted. The simulative results verify the accuracy of the proposed simplified impedance model and the impact analysis results of the key parameters on the system stability.