Nonlinear Feedback Linearization Control for Wind Generators in Hybrid Wind Energy Conversion Systems

This paper deals with the optimal power extraction of wind generators in hybrid wind energy conversion systems. The proposed control technique is the nonlinear exact feedback linearization which is able to give satisfactory performances over a broad spectrum of operating points. The main contribution of the paper is the successful dealing with the most challenging task in the design of nonlinear feedback linearization controllers for wind energy conversion systems, which is the transform and manipulation of state-dependent high-order nonlinear power coefficients presented in wind turbines. In other words, this paper addresses the full-order highly nonlinear power coefficients functions instead of using approximated low-order functions as in previous works in literature. The obtained nonlinear controller is able to cope with the time-varying nature of wind turbines and maintain the optimal power conversion points. Moreover the nonlinear feedback linearization control performance is also compared to that of traditional perturbation and observation based maximum power point tracking and classical PI control. The numerical simulation outcomes show that the proposed nonlinear controller outperform those two traditional controllers in terms of maximum gained power and transient specifications.