A Method of Designing Nonlinear Observers for Squirrel-cage Induction Generators in Windmill Power Systems

Abstract

This paper presents a new method of designing nonlinear observers for squirrel-cage induction generators in the windmill power systems. The control law which globally stabilizes the currents, angular velocity and pitch angle under full state measurement is determined by Lyapunov's direct method. Exponentially stable observers for the induction generator subsystem in the windmill power system, which is modeled as a bilinear system, is proposed. The design of the proposed observer is based on Lyapunov's direct method, and its estimation error decays to zero exponentially irrespective of the input. It is also shown that the observer-based extended system is globally stable.