Fuzzy sliding mode control for UPFC to improve transient stability of power system

This paper presents a nonlinear controller based on the fuzzy sliding-mode control technique to improve the transient stability of the power system. The rapid response of a controller is very desirable to damp transient power oscillation in the power system which is achieved with this control technique by shifting the sliding surface closer to the error trajectory using fuzzy logic. By this the sliding mode control unit need not wait for the state errors to strike the sliding surface. This modification enhances the performance of sliding mode control and also avoids the chattering effect. To validate the sturdiness of the controller computer simulation has been done by inducing transient disturbance at three different operating points and its performance has been compared with conventional PI controller. Following a transient disturbance the range of deflection in rotor angle is competently delimited by this nonlinear controller to maintain the generator in synchronism. The effectiveness of this nonlinear controller has been found to be independent of the operating point of power system.