考虑负荷动态模型的在线小干扰电压稳定指标

On-line Small Disturbance Voltage Stability Index Considering Dynamic Load Model

对电力系统在任一时间断面上从某个负荷母线向系统侧看进去的部分进行戴维南等值,并对负荷采用三阶感应电动机并联恒阻抗动态模型,分析该负荷节点的小干扰电压稳定性。通过对负荷节点PV曲线上的平衡点进行小干扰分析的结果表明,等值系统的小干扰电压稳定性本质上是负荷中感应电动机部分的静态稳定性,感应电动机部分采用三阶模型和一阶模型得到系统平衡点的小干扰电压稳定性是一致的,因而文中采用一阶模型条件下所推导出的系统在线小干扰电压稳定状态指标的解析表达式,能表征系统当前运行点各个负荷节点的电压稳定程度。IEEE39节点系统的计算结果表明该指标正确、有效、计算简便。

To analyze the small disturbance voltage stability of a power system, the Thevenin equivalent circuit is used to represent the section of system seen from a load bus at any point of time, and a third order induction motor model paralleled with a constant impedance dynamic model is used to represent the bus load. The results of small disturbance analysis at equilibrium points on the load bus＇ s PV curve show that the essence of the small disturbance voltage stability of an equivalent system is the steady stability of the induction motor part of a load, and it makes no difference whether the first order model or the third order model is used to represent the induction motor. Based on this finding, a new state index for the small disturbance voltage stability is expressed by an analytical equation which is deduced from the first order model. Calculation results on the IEEE 39-bus system validate the method.