In this paper, a decentralized robust approach is proposed for the Automatic Generation Control (AGC) system based on a modified traditional AGC structure. This work addresses the new strategy to adapt well-tested classical AGC scheme to the changing environment of power system operation under deregulation. The effect of bilateral contracts is considered as a set of new input signals in each control area dynamical model. In practice, AGC systems use simple proportional-integral (PI) controllers. However, since the PI controller parameters are usually tuned based on classical or trial-and-error approaches, they are incapable of obtaining good dynamical performance for a wide range of operating conditions and various scenarios in deregulated environment. In this paper with regard to this problem, the AGC synthesis is formulated as an H∞ static output control problem and is solved using a developed iterative linear matrix inequalities (ILMI) algorithm to design of robust PI controllers in the restructured power system control areas. A three area power system example with possible contract scenarios and wide range of load changes is given to illustrate the proposed approach. The resulting controllers are shown to minimize the effect of disturbances and maintain the robust performance.
