Stability Enhancement of a Multi-machine System using a Generalized Unified Power Flow Controller (GUPFC)

The generalized unified power-flow controller (GUPFC) is one of the latest-generation devices of flexible AC transmission systems (FACTS), which can be used to control the power flow of multiple transmission lines, increase loadability of the power system, improve power-system stability, etc. In this paper, the simulation results of a fourmachine system using the proposed GUPFC to improve power quality and achieve damping improvement are presented. The proposed GUPFC is designed to contribute adequate damping characteristics and enhance power quality of the studied multi-machine system under various operating conditions using MATLAB/SIMULINK toolbox. A time-domain scheme based on a nonlinear-system model subject to a three-phase short-circuit fault at the transmission line is performed to examine the effectiveness of the proposed control scheme. It can be concluded from the comparative simulated results of the studied system with and without the proposed GUPFC that the proposed GUPFC has superior characteristics for improving the stability of the studied system subject to a severe disturbance