This book presents coordinated design of PSS and FACTS damping controllers in multi-machine power system. When power systems are operating under stringent conditions, the inception of poorly damped low-frequency inter-area oscillations may lead to system-wide breakups or considerably reduce the power transfers over critical corridors. Request of PSSs have become the first measure to increase the system damping. However, during some operating conditions, PSS may not produce enough damping, particularly to inter-area modes. Recently, FACTS technology is emerging as an interesting approach to help in alleviating several power system operating difficulties. FACTS devices and PSS are all fast acting power system devices, and they have the potential to interact with each other and deteriorate the performance of overall system, if they are not coordinated properly. The coordinated design problem of PSS and FACTS controllers can be formulated as an optimization problem and an effective optimization technique could provide a reliable solution for the problem. In addition, this book proposes an effective optimization algorithm based on particle swarm optimization for the solution.