Secure and reliable operation of the power system is a critical issue for large, complicated, and interconnected power system networks. Security constraints such as thermal limits of transmission lines and bus voltage limits must be satisfied under any operating point in order to deliver reliable power to the consumers. One of the best alternative solutions of improvement of the security of power system is the use of flexible AC transmission systems (FACTS) devices. FACTS devices can be used to limit the power flow on the overloaded line and to increase the use of alternative paths to improve power transmission capacity. This chapter briefly describes all three categories of FACTS devices, namely shunt controllers (static synchronous compensator, static var compensator, thyristor-controlled reactor, thyristor switched reactor, thyristor switched capacitor), series controllers (static synchronous series compensator, thyristor controlled series capacitor, thyristor-controlled series reactor), and combined series-shunt controllers (unified power flow controller).
IMPROVING POWER SYSTEM QUALITY USING FLEXIBLE AC TRANSMISSION SYSTEMS
