The UPFC devices are integrated into the power system to control the power flow in specific lines and improve the security of the transmission line. UPFC is one of the most promising FACTS devices for power flow control and enhancing stability. This work describes the effect of UPFC to enhance dynamic stability reducing congestion problems in power systems. UPFC can improve power system dynamic performance through its supplementary control. Different simulations are carried out in the MATLAB Simulink environment.