Disturbance observer based integral sliding mode control for wind energy conversion systems

Abstract

Capturing of maximum power using wind energy conversion systems (WECS) is one of the focused problems in constructing high efficient wind energy source systems. In wind turbines with variable speed, maximum power can be reached at the point called optimal tip speed ratio point. Traditional anemometers are not effective in terms of accuracy of measured speed. Various methods are suggested to precisely estimate wind speed. A genetic algorithm is one of the proposed approaches to calculate wind speed accurately. However, its implementation is hard due to many parameters in the input. The relationship between the aerodynamic torque and wind speed gives us the opportunity to receive information about wind speed using the observed value of the aerodynamic torque. Several observers such as robust observers and sliding mode observers are introduced, and in their design stage, the assumption about slowly varying aerodynamic torque is made. In some cases, the fact of the proportionality of the aerodynamic torque to the wind speed makes this assumption inappropriate for a real system. Linear control methods are not satisfied to control WECSs due to its nonlinear nature. Application of nonlinear control techniques can be complicated and difficult in practice.