ENHANCEMENT OF POWER OSCILLATION DAMPING IN A SMIB SYSTEM USING FUZZY LOGIC BASED POWER SYSTEM STABILIZER

Abstract

ABSTRACT Power systems are subjected to low frequency disturbances that might cause loss of synchronism and an eventual breakdown of entire system. The oscillations, which are typically in the frequency range of 0.2 to 3.0 Hz, might be excited by the disturbances in the system or, in some cases, might even build up spontaneously. These oscillations limit the power transmission capability of a network and, sometimes, even cause a loss of synchronism and an eventual breakdown of the entire system. For this purpose, Power system stabilizers (PSS) are used in conjunction with the excitation system in order to damp these low frequency power system oscillations. The use of power system stabilizers has become very common in operation of large electric power systems. The conventional PSS (CPSS) which uses lead-lag compensation, where gain settings designed for special operating conditions exhibits poor performance under different loading conditions. The constantly changing nature of power system makes the design of CPSS a difficult task. Therefore, it is very difficult to design a stabilizer that could present robust performance at all operating conditions of electric power systems. To overcome the drawback of conventional power system stabilizer (CPSS), many techniques such as fuzzy logic, genetic algorithm, neural network etc. have been proposed in the literature. In an attempt to cover a wide range of operating conditions, fuzzy logic based technique has been suggested as a possible solution to overcome the above problem. Using this technique, complex system mathematical model can be avoided, while giving good performance under different operating conditions. Fuzzy Logic has the features of simple concept, easy implementation and computational efficiency. The fuzzy logic based power system stabilizer model is evaluated on a single machine infinite bus (SMIB) power system, and then the performance of Conventional power system stabilizer (CPSS) and Fuzzy logic based Power system stabilizer (FLPSS) are compared. Results demonstrate that fuzzy logic based power system stabilizer gives better performance than the Conventional Power system stabilizer. It has been shown that both the magnitude of oscillation and the setting time of the oscillation in FLPSS is much less than that of CPSS.