A Novel Index to Predict the Voltage Instability Point in Power Systems Using PMU-based State Estimation

Online assessment of power system voltage stability is essential to ensure its secure operation. Various indices have been developed to determine the proximity to voltage instability. The calculation of some of these indices has taken a high computational time, and some of them don't give appropriate results. In this study, a normalized voltage stability index (SI) for the voltage stability assessment is presented, which is mathematically developed on a two-bus system and is also studied on the IEEE 39-bus test system. With this index, the candidate buses for the voltage instability event are identified, and the voltage instability point of each of them is predicted using the curve fitting tool. Also, The state estimation tool is used to evaluate the proposed index and predict the instability point. In addition to the simplicity of calculation and reliability, the preference of the proposed method is that it is fast enough that it can be used for online monitoring of voltage stability.