Voltage stability analysis on two time scales by direct methods: quasi steady state analysis

Abstract

The theme of this research project is studying the problem of dynamic voltage stability, with special attention to cases of instability arising from major disturbances such as short circuit or loss of large blocks of generation and/or load. The models used for these studies have multiple time scales, it means devices of fast and slow dynamics coexist in the system. In fact, the problems of voltage instability due to the slow dynamics are very common and justify the interest in this type of study. In order to study the stability of slow dynamics, the engineers usually employ numerical integration of a simplified model where the short term dynamics are replaced by the equations of equilibrium. This method of analysis is known in the literature as QSS method (Quasi Steady State). The objectives of this research project are two: The first is to establish the theoretical foundations of the QSS method and establish the conditions under which the QSS method provides reliable results. The second objective is to explore the fundamentals of the QSS method to extend the direct methods of stability analysis, initially developed for the problem of transient stability analysis, to the problem of stability analysis in the midterm. (AU)