The reactive power compensation in power system is done by using different Flexible AC Transmission Controllers (FACTS). Unified Power Flow Controller (UPFC) is simulated and analyzed to observe its overall functions when integrated into a transmission line. It is installed in electric transmission lines hence assisting in the controlling and manipulating of the power flowing in the lines to give out reliable, controlled and efficient electricity to an ordinary consumer. The modelling of this device UPFC was done based on the theory of line models which are short, medium and a long line models. Conclusion on which model to use was based on two factors. The first one is model voltage level and length of the transmission line. The simulation of the designed circuit models was carried out using MATLAB and the results were then analyzed.