Electrical Power Systems Stabilization through Series Compensation by using Variable Structure Control

This work deals with power system stabilization through a flexible transmission line (FACTS). Series compensation is introduced by a controlled switching scheme that changes the transmission line reactance. Switching is implemented according to variable structure control concepts in order to establish a sliding mode operation where oscillations die out very fast. A power system consisting of a synchronous generator, a line reactance with series compensation and an infinite bus is used as a case study. For this basic power system control strategies are shown to pursue: a) sliding mode operation; b) asymptotic stability; or c) asymptotic stability with sliding mode operation. The last strategy assures asymptotic stability for large oscillations and afterwards a fast convergence towards a stable equilibrium state. Simulation tests are then performed for the basic power system, first, for an initial condition and then under a disturbance. The dynamics of a reduced model of a real power system is also studied under a disturbance. The combined strategy, asymptotic stability with sliding mode, shows to be adequate for power system stabilization