AN ON-LINE VOLTAGE STABILITY INDEX OF POWER SYSTEM BASED ON SYNCHRONIZED PHASOR MESUREMENT

The rapid development and wide applications of Wide-Area Measurement System (WAMS) provide great potential for online assessment of voltage stability in large-scale power systems. An on-line voltage stability index, LVSI, has been proposed in this paper, which is defined as a function of measurements of WAMS. For any transmission line at a certain time point, LVSI is constructed based on the model of Π equivalent connecting with an infinite voltage source and a load, and calculated by measured bus voltage phasor, power flow and other related quantities. The maximum value of the all LVSI can be considered as the voltage stability index of the system. Correspondingly, the line with maximum LVSI is called the weakest line. The distance between LVSI and the critical value of 1 denotes the margin of voltage stability. And if the system is being deteriorated towards voltage collapse, the LVSI of the weakest line will approach to 1. Simulation results of the EPRI 36-bus system show the validity of the index, and the availability of the index used for real-time monitoring of power system voltage stability.