基于改进型PEM和L指标的含风电场电力系统静态电压稳定评估

快速、准确地评估系统电压稳定性对于大规模风电并网后电力系统安全运行具有重要意义。为此，提出一种基于改进型点估计法(point estimate method，PEM)和局部电压稳定指标(L指标)的含风电场电力系统静态电压稳定评估方法。首先，提出一种改进型PEM计算L指标各阶矩和半不变量，并结合Cornish-Fisher级数展开获得其概率分布，相比于传统2n+1法，在无须涉及更高阶矩等复杂计算下可提升L指标分布的拟合精度；然后，利用风险偏好型效用函数定义计算各节点电压失稳风险度，完成含风电场电力系统静态电压稳定评估，识别系统电压稳定薄弱节点；最后，基于该风险度引入风电并网电压稳定因子，并由此分析风电对系统静态电压稳定的影响。采用改进的IEEE-14和39节点系统算例验证了所提方法的可行性和有效性。

Steady-State Voltage Stability Evaluation of Power System Containing Wind Farm Based on Improved PEM and L Index

How to quickly and accurately evaluate the system voltage stability after large-scale wind power integration is of great significance to the safe operation of the power system. This paper proposes a method for evaluating the steady-state voltage stability of power system with wind farms based on the improved point estimate method (PEM) and local voltage stability index (L index). Firstly, an improved PEM is put forward to calculate the order moments and semi-invariants of the L index and obtain its probability distribution by combining the Cornish-Fisher series expansion. Compared with the traditional 2n+1 method, this method can improve the fitting accuracy of the L index distribution without complex calculations such as higher-order moments. Then the risk preference utility function is employed to define and calculate the voltage instability risk of each node for assessing the static voltage stability of the power system with wind farms and identifying the weak nodes of system voltage stability. Finally, on the basis of the risk degree, the wind power grid-connected voltage stability factor is introduced to analyze the influence of wind power grid integration on the steady-state voltage stability of the system. The example results of the IEEE-14 node and IEEE-39 node verify the feasibility and effectiveness of the proposed method.