Design of suboptimal H∞ excitation controllers

This paper presents a method to design power system suboptimal robust excitation controllers based on H^∞ control theory. The suboptimal controller results from additional constraints that are imposed on the standard optimal H^∞ solution. Global stability constraints are incorporated into the H^∞ algorithm to ensure stability of the interconnected system under decentralized control. Furthermore, a Lyapunov-based index is used to evaluate the robustness properties of the closed loop. In order to obtain a reduced order controller, the method of balanced truncation is used. The suboptimal H^∞ controllers are output feedback controllers. These controllers posses superior robustness as compared to a conventional PSS and optimal H^∞ controllers