Modeling and Transient Simulation of Unified Power Flow Controllers (UPFC) in Power System

with the growing demand of electricity, at times, it is not possible to erect new lines to face the situation. Flexible AC Transmission System (FACTS) uses the thyristor controlled devices and optimally utilizes the existing power network. FACTS devices play an important role in controlling the reactive and active power flow to the power network and hence both the system voltage fluctuations and transient stability. This paper proposes the Unified Power Flow Controller (UPFC) as a strong candidate to provide a full dynamic control of Power transmission operating parameters: voltages, line impedance, and phase angle under normal and fault conditions. Simulink model composed for 4 bus system equipped with UPFC to illustrate the control features of this device and their influence to increase power transfer and improve system stability. Digital simulation using MATLAB/SIMULINK is done with this model and the results are presented. The effect of UPFC on real power, reactive power and the voltage is also presented.