Implementation of a discrete fuzzy PID excitation controller for power system damping

The power system is nonlinear with frequent changes in operating regions. Analog proportional integral derivative PID controllers are widely used in excitation control of power systems. Fuzzy logic control is often viewed as a form of nonlinear PD, PI or PID control. This paper describes the design principle, tracking performance of a fuzzy proportional-integral PI plus derivative D controller. This controller is developed by first describing discrete time linear PID control law and then progressively deriving the steps necessary to incorporate a fuzzy logic control mechanism into the modifications of the PID structure. The bilinear transform (Tustin's) is used to discretize the conventional PID controller. In this paper some performances criteria were utilized for comparison with other PID controllers, such as settling times, overshoots and the amount of positive damping. The proposed scheme is robust to variations in operating conditions to match the fluctuations of load demand in the power system.