H∞ decentralized observation and control of nonlinear interconnected systems

In this paper, we investigate the problem of H,, decentralized tracking control design with a decentralized observer for interconnected nonlinear systems which are characterized by the interconnection of N subsystems. Each subsystem is modeled by a linear constant part perturbed by an additive nonlinearity which is illustrated by the interconnection terms. The proposed feedback control scheme is developed to ensure the asymptotic stability of the augmented system, to reconstruct the non-measurable state variables of each subsystem, to maximize the nonlinearity domain, and to improve the performance of the model reference tracking control by using the H-infinity criterion despite the external disturbances. The proposed control approach is formulated in a minimization problem and derived in terms of linear matrix inequalities (LMIs) whose resolution yields the decentralized control and observation gain matrices. The effectiveness of the proposed control scheme is demonstrated through numerical simulations on a power system with three interconnected machines. (C) 2009 ISA. Published by Elsevier Ltd. All rights reserved.