Hamid Toliyat - Ferdowsi University – Mashhad, Iran
Javad Sadeh - Ferdowsi University – Mashhad, Iran

This paper presents a fuzzy logic power system stabilizer (PSS) for stability enhancement of a power systems. In order to accomplish a satisfactory damping characteristic over a wide range of operating points, speed deviation (∆ω) and acceleration (∆ώ) of synchronous generators were taken as the input signals to the fuzzy controller. It is well known that these variables have significant effects on damping the generators shaft mechanical oscillations. A modification of the terminal voltage feedback signal to the excitation system as a function of the accelerating power on the unit is used to enhance the stability of the system. The stabilizing signals are computed using the fuzzy membership function depending on these variables. The effectiveness of the proposed improved fuzzy controller is demonstrated by digital computer simulation studies of a one machine infinite bus system.