Optimal interaction between PSS and FACTS devices in damping power systems oscillations: part I

Most power systems are interconnected through long distance tie lines in order to transfer or exchange a large amount of electric power. Due to limited availability of resources because of the strict environmental constraints and sometimes shortage of funds to build new transmission lines, this necessitates the operation of transmission lines near or for short term on their thermal limits. Also, the demand for electric power has rapidly increased and is expected to continue growing , while expansion in generation is restricted too due to the same reasons mentioned above, this necessitates the generators too to operate near their stability limits. As a result of all these factors, power systems oscillations will occur; if not well damped, these oscillations may keep growing in magnitude until loss of synchronism results. The power system stabilizer (PSS) and flexible ac transmission system devices (FACTS) can help in damping of power systems oscillations. The objective of this work is to study and design a controller capable of doing the task of damping in less economical control effort, and to globally link all controllers of national network in an optimal manner, toward smarter grids. This can be well done if a specific coordination between PSS and FACTS devices, is accomplished. Firstly, A genetic algorithm-based controller is used. Genetic Algorithm (GA) is utilized to search for optimum controller parameter settings that optimize a given eigenvalue based objective function. Secondly, an optimal pole shifting, based on modern control theory for multi-input multi-output systems, is used. It requires solving first order or second order linear matrix Lyapunov equation for shifting dominant poles to much better location that guaranteed less overshoot and less settling time of system transient response following a disturbance.