直流接入比与频率稳定性的关系及水电主导调频控制的改进策略

Relationship Between DC Access Ratio and Frequency Stability and Improved Strategy of Hydropower Dominant Primary Frequency Control

受端频率稳定性与直流接入比的关系研究,对直流接入量的选择和频率稳定控制都有意义。分析了水电主导调频时,直流受端区域受扰后的频率波动过程,得到直流接入比与暂、动、静态频率稳定性指标的关系。发现接入比与3态稳定性都负相关,且对暂、动态的影响力较大。另外,还分析了送端直流输出调节对受端频率的影响。为提高受端的频率稳定性,提出了水电机组一次调频的改进策略,即在频率反馈通道并联微分环节以提高阻尼,设置新的调差系数以提高静、暂态稳定性。仿真验证了改进策略的有效性。该研究对提高直流受端区域的频率稳定性,提供了实用的参考依据。

Study of relationship between frequency stability of receiving end and DC access ratio is of great significance for selection of DC access ratio and frequency stability control. The paper analyzes frequency fluctuation process under disturbance of DC receiving-end region when hydropower units dominate primary frequency regulation, to obtain the relationship between DC access ratio and transient, dynamic and static frequency stability index. Analysis find out that the access ratio is negatively related to stability of the three states, and has a great influence on transient and dynamic performance. In addition, the influence of DC output adjustment on receiving-end frequency is also analyzed. Therefore, in order to improve frequency stability of receiving-end area, an improved strategy of primary frequency regulation of receiving-end hydropower units is suggested, i.e. a differential link is connected in parallel in the frequency feedback channel to improve damping and a new adjustment coefficient is set to improve static and transient stability. Effectiveness of the improved strategy is verified with simulation. The study provides a practical reference for improving frequency stability of DC receiving-end region.