Fuzzy logic based FACTS controller for damping oscillations

This paper describes the modeling and fuzzy based control to enhance the dynamic stability of a single machine connected to a large system through flexible AC transmission system. A linear model of a synchronous machine with excitation system characterized by a single time constant and gain is adopted for this purpose. The synchronous machine is described in terms of six parameters derived on the basis of operating conditions and line reactance. The flexible AC transmission system adjusts the line reactance by turning on/off series capacitance added to the transmission line. The effect of change in line reactance on the parameter values of the machine model is found and the most sensitive parameters are identified. The response of the machine for different disturbances and natural damping coefficients is evaluated by modifying the most sensitive parameters using the fuzzy knowledge-based FACTS controller. The simulation studies bring out the effectiveness of the control scheme.