Investigations on a fuzzy logic based SVC Damping controller

Abstract

Power systems all over the world have grown exponentially with time. Since acquiring right-of-way for laying of new transmission lines have been increasingly more difficult in light of economic, legislative and environmental problems, more and more power has to be pushed through the already stressed existing transmission corridors. This may result in low frequency oscillations typically in the range of 0.1-2 Hz. These low frequency oscillations may be exhibited as synchronous machines oscillating against one another, or a group of machines oscillating with respect to another group. Traditional approach to address this problem has been to equip PSS in the machines which has tendency to damp out power oscillations. Ever since the FACTS technology was initiated by the EPRI in the 1980’s, a number of power electronics based FACTS Controllers have evolved, which modify the existing power system parameters to effect rapid controllability of existing power transmission capabilities. Static Var Compensator (SVC) was one of the earliest FACTS Controllers to be used for voltage control and stability improvement of power networks. Modulation of the SVC susceptance using supplementary control signals like generator speed deviation, line current etc in conjunction with the SVC voltage controller can be used to damp power system oscillations. In addition, fuzzy logic based damping controllers came into existence, which proved to be more effective in damping power system oscillations than conventional ones. In this work, a conventional and a fuzzy logic based SVC damping controller is developed for power oscillation damping. Different supplementary control signals have been adopted for both these controllers and the small signal stability of the system is studied. A comparison of the responses indicates that fuzzy logic based SVC damping controllers exhibit better performance characteristics than conventional ones.