Fuzzy bang-bang control of static VAR compensators for damping system-widelow-frequency oscillations

Static VAR compensators (SVCs) have been widely used in power systems to ke ep terminal voltages within bounds. The other application is to improve pow er systems damping, especially for loosely connected power systems. In this paper, a scheme using fuzzy logic control (FLC) is connected in parallel w ith a conventional voltage regulation loop to form a supplementary damping loop for the SVC to increase the system's transmission capacity. The FLC is based on bang-bang control, and provides damping across each connected lin e to the SVC. Damping is of particular importance especially for weakly cou pled power systems. Using rotor-angle signals that are estimated from volta ge and power measurements at each connected line to the SVC, a fictitious g enerator at the remote end of each connected line is identified. The SVC re ceives control signals from all fictitious generators, which are competing and reacting differently at different phases of system oscillations. The fi nal control for the SVC combines the control signals from all fictitious ge nerators, which are scaled according to their individual contributions to d amping. The proposed signal structure guarantees robustness and effectivene ss of the final control with respect to different loading and fault conditi ons. The FLC design is based on Lyapunov function analysis, and is simulate d on a three-generator power system for performance evaluation. (C) 1999 El sevier Science S.A. All rights reserved.