A Multi-Level Fuzzy Power System Stabilizer to Improve Dynamic Stability

The electrical power system is the one of the largest complex and dynamic system on earth. This system is continuously subjected to small disturbances that might cause loss of synchronism and also breakdown of entire system. For this purpose, Power system stabilizers (PSS) are used to generate supplementary control signals for the excitation system in order to damp these low frequency power system oscillations. The additional signals are derived from speed deviations, excitation deviations and accelerating power are injected into the automatic voltage regulator. The conventional power system stabilizer (CPSS) uses lead-lag compensation techniques, where gain settings are fixed for specific operating condition. In an attempt to cover wide range of operating conditions fuzzy logic controllers are the best. The fuzzy logic uses linguistic information and avoids complex mathematical models, while ensuring better performance. In this project, a novel design of multi-level fuzzy controller for power system stabilizer to damp the low frequency power system oscillations is described. The control objective is to enhance the stability and to improve the dynamic response of the SMIB system. The system is modeled as standard K-coefficients in second order. Its control structure is designed to bring fore an intelligent upper level fuzzy controller and a lower level direct fuzzy controller. This fuzzy controller performance is observed for different membership functions like triangular, Gaussian and trapezoidal. The performance of the proposed controller shows improved results when compared to conventional and direct fuzzy controllers. This work is executed in SIMULINK environment and performance is investigated for disturbances subjected to inputs of different membership functions.