Voltage stability indices based on active power transfer using simulated phasor measurements

In recent years and in the foreseeable future, power demands generally around the world and particularly in North America will experience rapid increases due to the increase of customers' requirements, while the development of transmission systems in North America is rather slow. Voltage stability assessment becomes one of the highest priorities to power utilities in North America. Voltage stability index (VSI) is a feature for solving voltage stability problems. It is generated from the basic power flow equations and/or energy functions. The mathematical expression of a VSI is often written as a polynomial containing the systems real-time measurements such as voltage magnitudes, phase angles, bus injected power and branch power flow values, etc.;In this thesis, the principle and derivation process of two voltage stability indices are presented. Relevant simulations are analyzed to demonstrate the VSIs' functions as illustrating the system's stability condition, estimating the systems operating states, determining system sensitive buses; and generator-sensitive buses and helping to apply system protection strategy. The thesis also discussed the application of VSIs with synchronized phasor measurement units, a precise system phasor measuring device using global positioning signal to obtain wide-area system measurements simultaneously. The effect of measurements errors on the computation of the VSI is studied and examined. Finally, a discussion of the future development of synchrophasors and VSI methods is given.