点估计法在电压稳定性分析中的应用

Application of Point Estimate Method to Voltage Stability Analysis

针对电压稳定概率评估中难以考虑支路故障随机性的问题,提出了基于点估计法的电压稳定分析方法。该方法不仅可以方便地统一处理线路故障及节点注入功率的不确定性,还克服了线性化方法难以计及发电机无功出力约束的不足;避免了潮流方程线性化,通过少量确定性计算即可求出系统负荷裕度以及电压崩溃临界点处节点电压幅值与相角的前几阶矩,从而获得各待求随机量的概率分布,确定某一负荷水平下的电压失稳概率。与蒙特卡罗方法相比,点估计法在具有较高计算精度的同时,体现出求解速度快的特点。数值仿真分析了随机变量标准差和系统规模对点估计法计算精度的影响,并指出在综合考虑计算精度和计算时间的情况下,2点估计法的结果令人满意。

The problem of taking random branch outages into account in probabilistic evaluation of voltage stability is studied, and an efficient point estimate method based is proposed. The proposed method can not only consider random branch outages as well as Uncertainties of nodal power injections conveniently but also overcome the shortage of linearzation method＇s inability of considering the generator output constraint. This method avoids making power flow equations linear, and the statistic moments of loading margin, magnitude and angle of bus voltage on the point of voltage collapse are computed by a few deterministic computations. The probabilistic distributions of each desired variable are then obtained and the probability of voltage instability under some load level may be determined. The point estimate method has high precision results, and when comparing with Monte Carlo simulation, it needs less execution time. The effects of standard deviation of random variables and system size on computational accuracy are investigated by several numerical examples and two points estimate method are recommended when computational accuracy and execution time are considered in a comprehensive way.