The rapid development of power electronics technology provides opportunities to develop new power equipment to improve the performance of the actual power systems. During the last decade, a number of control devices called "Flexible AC Transmission Systems" (FACTS) technology have been proposed and implemented. FACTS devices can be used for power flow control, loop-flow control, voltage regulation, enhancement of transient stability and damping of power oscillations. FACTS devices can be used as a series controller, shunt controllers or by a combination of both.