不确定性问题是电压暂降评估工作的难点之一。文中提出了一种在不确定条件下的电压暂降概率仿真与评估方法，重点分析发电机组的启停、负荷波动和系统运行方式的变化等随机性因素对负荷点电压暂降评估指标的影响。机组运行状态发生变化时，运用线性化方法修正初始潮流分布。文中建立了负荷波动时的电压暂降迭代计算格式，避免了每次迭代时重新计算潮流，提高了算法的计算效率。对IEEE 30节点试验系统的蒙特卡洛仿真以及评估指标的计算验证了文中方法的有效性。

Uncertainty is one of the difficulties in the assessment of voltage sag. In this paper a method to simulate and assess probability of voltage sag under uncertain conditions is proposed, in which the influence of random factors, such as startup and shutdown of units, load fluctuation and variation of system operation modes, on assessment indices of voltage sag and emphatically analyzed. When operation condition of units varies, the initial power flow distribution is modified by linearization method. A pattern of iteration calculation of voltage sag under load fluctuation is built to avoid the recalculation of power flow for each time of iteration, thus the calculation efficiency of the proposed algorithm is improved. The Monte Carlo simulation results of IEEE 30-bus system and the calculation results of assessment indices vary the effectiveness of the proposed method.

基金项目：国家重点基础研究发展计划项目(973项目) (2009CB219706)；国家自然科学基金资助项目(70773039，70911130016)；高等学校学科创新引智计划项目(B08013)。

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