Significance of ancillary devices for load frequency control

Over the past few decades, the demand for electricity has increased significantly, while the extension of electric infrastructure (such as the generation and transmission sector) has been restricted because of resource constraints and physical intermittencies. As a consequence, loading greatly affects transmission lines, which results in instability problems and limits the power transfer capability. Therefore, a flexible alternating current transmission system (FACTS) could be essential to flexibly control the power flow between the transmission lines. Besides, FACTS is also enhancing the system controllability and stability through various arrangements. Moreover, the application of modern power electronics into the power system network has changed the stability and security factor scenario. As the controller plays a vital role in AGC, the incorporation of FACTS can further enhance the stability and power flow control. The FACTS system has been categorized into three provisions according to the connection: series, shunt, and hybrid. More importantly, the role of FACTS in the AGC system has played a crucial role, which has been made a remarkable achievement toward minimizing the sudden change in frequency and tie-line power deviation.