基于无源阻尼的柔性直流输电系统高频振荡抑制策略

High-frequency oscillation suppression strategy of MMC-HVDC based on passive damping method

柔性直流输电系统的控制链路延时效应使系统阻抗在高频段呈现负阻尼特性,可能导致与交流线路分布电容相互作用产生高频振荡。现有抑制策略中,附加低通滤波器等有源阻尼策略对运行工况和延时时间变化的适应性较差,无源阻尼策略适应性较好但面临功率损耗较大等问题。基于此,本文首先建立考虑完整控制环节和延时效应的模块化多电平换流器交流阻抗模型,通过阻抗分析法分析高频振荡的产生原因,其次提出基于无源阻尼的高频振荡抑制策略及参数设计方法,最后通过抑制效果分析和功率损耗比较证明所提高频振荡抑制策略的有效性。结果表明,所提振荡抑制策略可适应延时时间的变化,实现高频振荡的有效抑制且基波功率损耗低。

The delay effect of the control link of MMC-HVDC makes the system impedance exhibit negative damping characteristics in the high frequency band, which may cause high frequency oscillation due to the interaction with the distributed capacitance of the AC line. Among the existing strategies, active damping strategies such as additional low-pass filters have poor adaptability to changes in operating conditions and delay time, while passive damping strategies have good adaptability but faced with problems such as large power loss. In view of the above problems, this paper firstly establishes the AC impedance model of the modular multilevel converter considering the complete control link and delay effect, and analyzes the causes of high frequency oscillation through impedance analysis. Secondly, a passive damping-based high-frequency oscillation suppression strategy and parameter design method are proposed. Finally, the effectiveness of the proposed high-frequency oscillation suppression strategy is proved by effect analysis and power loss comparison. The research results show that the proposed oscillation suppression strategy can adapt to the change of delay time, and realize the effective suppression of high-frequency oscillation and low power loss.