基于值集法对云南电网超低频振荡的稳定分析

Stability Analysis of Ultra-Low Frequency Oscillation of Yunnan Power Grid Based on Value Set Approach

基于值集法(value set approach)提出一套用于超低频振荡稳定分析的多参数图形化分析工具,并以云南电网为例分析了云南电网与南方电网异步联网后出现的超低频振荡现象。首先,根据云南电网异步联网前后的系统结构构建一个统一频率模型以模拟超低频振荡现象。随后,利用值集法计算特征多项式在超低频频段的值集,并根据值集到复平面原点的距离判断系统的鲁棒稳定性。通过观察各不确定参数对值集的影响,进一步分析各参数对稳定性的交互作用并提出改进措施。分析结果表明,云南电网异步联网后水电比例过高是导致超低频振荡的重要原因,并且水轮机特性系数对稳定性的影响不容忽视,在稳定分析和模型建模时需要着重考虑。系统中水电厂电调型调速器参数设置存在改善空间。对水电厂调速器进行参数优化后,超低频振荡得到改善。

This paper presents a multi-parameter graphic-oriented robustness analysis method for ultra-low frequency oscillations based on value set approach. Yunnan Power Grid is taken as a study example, where ultra-low frequency oscillations occurred after asynchronously connected to China Southern Power Grid. Firstly, Yunnan Grid is represented with a uniform-frequency model to catch dynamics of ultra-low frequency oscillations. Value set of the system characteristic polynomial within frequency range is then calculated so that the system robust stability is analyzed by observing distances between the value sets and origin. Effects of uncertain parameters on system stability are analyzed and improvement measures are suggested. Results show that excessive large proportion of hydropower during asynchronous interconnection is a culprit contributing to the ultra-low frequency oscillations in Yunnan Grid. Moreover, turbine parameter coefficients are proved to play an important part in system stability, and should not be overlooked in system modelling. By optimizing parameters of hydropower governors, the stability is improved.