控制参数对柔性直流电网稳定性的影响分析

控制参数的合理选择是柔性直流电网稳定运行的前提条件，而其参数整定又依赖于柔性直流电网的稳定性模型。首先，提出了基于直流电压斜率控制的柔性直流电网小信号模型，同时考虑了模块化多电平换流器内部动态特性及环流抑制器的作用。然后，利用根轨迹法分析直流电压斜率控制器的PI参数、斜率参数和环流抑制器PI参数对系统稳定性影响。利用参与因子法识别二倍频环流所对应的模态，进而分析PI参数对二倍频环流抑制的影响效果。最后，在PSCAD/EMTDC平台上搭建张北柔性直流电网试验示范工程仿真系统，验证所提建模方法以及结论的正确性，为实际工程中控制参数整定提供了理论依据。

Impact analysis of control parameters on the stability of flexible DC girds

Reasonable selection of control parameters is a precondition for stable operation in a flexible DC power grid, and their tunings will depend on the stability model of the flexible DC power grid. First, a small-signal model of such a grid based on DC voltage slope control is proposed, and the internal dynamic characteristics of the modular multilevel converter and the function of the circulating current suppressor are considered. Secondly, the root locus method is used to analyze the influence of the PI parameters and the slope parameter of the DC voltage slope controller, and of the PI parameters of the circulating current suppressor on the stability of the system. The participation factor method is adopted to identify the mode corresponding to the double frequency circulating current, and then the suppression effect of PI parameters on double frequency circulation is analyzed. Finally, a simulation of the Zhangbei flexible DC grid demonstration project is built on the PSCAD/EMTDC platform to verify the correctness of the proposed modeling methods and conclusions. This paper provides a theoretical basis for control parameter tuning in practical projects.This work is supported by the Beijing Natural Science Foundation (No. 3172015) and the Science and Technology General Project of Beijing Education Commission (No. KM201911232016).