Energetic Optimization of Variable Speed Wind Energy Conversion Systems by Extremum Seeking Control

This paper approaches the control problem aiming at maximizing the energetic conversion for a class of horizontal axis fixed pitch variable speed small power wind energy conversion systems, working in the partial load region. The wind turbine model and its parameters are poorly known. Using the extremum seeking control principles, a new approach of the generically called maximum power point tracking (MPPT) is proposed. It aims at driving the average position of the operating point near to optimality. Instead of inducing sinusoidal search signals, the wind turbulence is here used as search disturbance. The operating point´s distance to optimality is estimated using the fast Fourier transform processing of some available measures. The high speed shaft´s average rotational speed is then slowly adjusted. Numerical simulations are used to validate the proposed control law.