Review of flexible AC transmission systems; enabling technologies for future smart grids

Since the Kyoto agreement on global greenhouse-gas emissions has been ratified by nearly all nations, individual countries pledged to reduce conventional fossil fuel-based generation and integrating more renewable energy sources within the electricity grids. With such enthusiasm, researchers have identified several challenges in achieving this goal. These challenges include extensive mix of utility, individual investors and residential generation, employing cost effective energy storage technology, adopting intelligent on line monitoring and self-healing systems, secured communication protocols and smart control technologies. In developing the architecture for future smart grids comprising distributed renewable energy sources, the international renewable energy agency has identified remarkable points in this ambitious transformation journey these are: enabling bi-directional energy flow, proposing improved grid interconnection, adopting improved technologies and increasing energy storage capacity. As some of the renewable energy sources are of intermittent characteristic, it is expected that flexible ac transmission systems (FACTS) playing a significant role within the next generation of electricity grids. This paper is aimed at providing a brief review for the most popular FACTS devices, their applications and various proposed controllers.