Output feedback excitation control of synchronous generators

In this paper a solution to the output feedback control problem, that improves the transient stability properties, of a single machine infinite bus power system is proposed by designing a nonlinear observer that asymptotically recovers the unmeasurable states of the system. The structure of the closed-loop system is completed by considering an injection and damping assignment passivity-based controller for which its stability properties are well established under a state feedback setting. It is shown, by using Lyapunov arguments and as a consequence of the asymptotic stability properties of the closed-loop system, that the properties of the original state feedback controller are (also asymptotically) recovered. The output feedback design considers that both the load angle and the speed deviation of the machine are measurable and that the mechanical power delivered to the synchronous generator is constant and known, assumptions that allow to treat uncertainty on the operating (equilibrium) point of the system in a simple way. The theoretical results are illustrated via numerical simulations. Copyright (C) 2004 John Wiley Sons, Ltd.