Control of the inter-area dynamics using FACTS technologies in large electric power systems

In this paper a conceptual formulation of a modular control design for controlling inter-area oscillations in the very large-scale power systems is introduced. The design is based on using the new state-space formulation of power system dynamics recently introduced. This choice of state-space enables one to represent even the nonlinear dynamics in the standard state-space form of ordinary differential equations. Furthermore, it sets the basis for control design in terms of measurements simple to perform, and therefore promises considerable robustness. Next, the physical devices for controlling the inter-area oscillations are assumed to be capable of directly controlling flows of transmission lines on which they are located. Some examples of such devices are phase-shifting transformers and series capacitors. If these devices are controlled by means of fast power electronic switching they can be categorized under the well recognized class of the flexible AC transmission systems (FACTS) devices. This paper is concerned with the conceptual systems issues of the best control design so that certain desired performance of the inter-area dynamics is guaranteed.