The power system is constantly subjected to numerous forms of disruptions, resulting in a loss of stability. The cause of instability is a large disturbance. The "large disturbance" leads to electromechanical oscillations in a synchronous generator. For this problem, the Tana Beles hydropower plant uses AVR to enhance the stability of synchronous generators under steady state and faulty conditions. However, with the creation of large disturbances, this regulator gives poor performance due to long settling time and maximum overshoots. In this thesis, power system transient instability of synchronous generators found in the Tana Beles Hydropower plant was introduced in steady state and faulty conditions. Which were damped out quickly by using a fuzzy logic controlled power system stabilizer (FLPSS). FLPSS is implemented in the excitation systems of synchronous generators to damp electromechanical oscillations of the study under wide operating conditions. The system performance has been performed in different scenarios (under normal and faulty conditions with AVR, PID, CPSS, and FLPSS for comparative analysis). FLPSS reduces settling time and greatly damps electromechanical oscillations of rotor speed, load angle, electrical torque, and active power of synchronous generators under steady state and faulty conditions. The thesis deals with the design procedure for a fuzzy logic based PSS (FLPSS) which improves the transient stability of synchronous generators. The speed deviation of a synchronous machine and acceleration are chosen as the input signals to the fuzzy logic controller. Under steady state conditions, FLPSS enhances the settling time of rotor speed and load angle by 79.2% and 68.75% respectively. Similarly, the overshoots of rotor speed, active power, electrical torque, and terminal voltage are reduced by 14.3%, 55%, 55%, and 6.5% respectively. During a fault condition, FLPSS also enhances the settling time of rotor speed, load angle, active power, and electrical torque by 77.7%, 50%, 88%, and 76.5% respectively. Similarly, FLPSS reduces the overshoots of generator parameters of rotor speed, load angle, and terminal voltage by 7.7%, 3.1%, and 14.26% respectively. The comparison was done between the excitation systems with AVR and FLPSS using MATLAB/Simulink software. Keywords: CPSS, FLPSS, MATLAB /Simulink, PID controller and Transient Stability