Maximum power extraction from a wind turbine using second-order fast terminal sliding mode control

Abstract

The maximum wind power extraction and reduction of mechanical stresses in the operating region of below rated wind speed (region 2) are two major issues in wind power. To overcome both issues, two nonlinear control strategies using a second-order sliding mode control (SOSMC) are proposed seeking a better performance. The proposed controllers have been developed to neutralize the effects of parametric uncertainties, unmodeled dynamics, and external disturbances. In the first strategy, a proportional integral derivative (PID) sliding surface is used while in the second strategy a combination of nonlinear terminal sliding surface with PID sliding surface is used to design of the second order fast terminal sliding mode control (SOFTSMC). PID sliding surface is applied to ensure the better tracking, to achieve a zero steady-state error, to reduce the mechanical loads and to attenuate the chattering phenomenon whereas nonlinear terminal sliding surface is applied to have maximum wind power extraction and to establish fast finite-time convergence by applying a small control input. The Lyapunov stability theorem is conducted to show closed loop stability. The results are compared to some existing control laws and their performance evaluation are presented in Table. 1. The results of Table. 1 confirm the effectiveness of the proposed controllers.