transmission of power with a high power factor and high power quality, supreme transient stability, economics, and a low risk of system failure are the primary concerns in the power grid system. The steady growth of electrical power demands and loads, especially non-linear loads, makes the power system network increasingly difficult to manage, and the system becomes unstable with massive power flows if effective control and operation are not implemented. The evolution of the power system has brought new obstacles, and due to the complex system network, it might be difficult to operate the system in a stable state at times. On the other hand, significant progress has been achieved in power electronics, which allows the power system to remain stable even when the worst-case scenario occurs due to a fault. FACTS technology is one of the innovations in power electronics. FACTS (Flexible Alternating Current Transmission Systems) devices are based on power electronics and other dynamic controllers that adjust one or more AC transmission system parameters in order to improve controllability and power transfer capabilities. FACTS controllers, such as UPFC, are one way to improve power system control (Unified Power Flow Controller). At the same time, UPFC can manage voltage, impedance, and phase. In the power system block set, MATLAB/PSAT is used to simulate the UPFC control technique for grid-connected power systems. The effectiveness of UPFC is examined using an IEEE 9 bus power system network by applying a 3-phase fault to dissimilar buses and evaluating the performance of FACTS devices in an IEEE 9 bus power system during a fault situation.