Unified Power Flow Controller (UPFC) is the most versatile FACTS device which has the capabilities of controlling power flow in the transmission lines, improving the transient stability, mitigating system oscillations and providing voltage support by integrating series and shunt compensators. This paper can serve as a compendium of the tremendous amount of new materials being developed in this field. First rotor angle deviation and speed deviation are analysed with and without FACT devices in a

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... Single-Machine Infinite Bus (SMIB) power system, then PID controller is incorporated properly for improving electromechanical oscillation with STATCOM, SSSC and UPFC under step change in turbine mechanical input and faulty condition respectively. The results are compared by using Matlab Simulink.