Energy functions analysis in voltage collapse

Time-domain approach examines the behaviour of the system, one determines w hether stability has been maintained or lost. In contrast to the time-domai n approach, direct methods determine system stability based on energy funct ions. The basis of direct methods for the stability assessment of a system is knowledge of the stability region. During the last decade, many research es have thoroughly analysed the use of energy functions for the direct stab ility assessment of networks. Energy function analysis offers a different g eometric, view of voltage collapse. The Transient Energy Function, a techni que based on Lyapunov stability theory and originally developed for direct stability analysis of power systems, has been successfully used as a voltag e stability index for collapse studies. In this paper the simulation result s are on the IEEE 173-bus test system.