Variable gain high order sliding mode control approaches for PMSG based variable speed wind energy conversion system

This research article proposes two different variants of variable gain higher-order sliding mode control (HOSMC) strategy for a variable-speed wind energy conversion system (WECS) based on a permanent magnet synchronous generator (PMSG). The main objective is to extract the maximum wind power with reduced chattering and mechanical stress. The main flaw of the classical sliding mode control (SMC) is the high-frequency switching, called chattering, which is alleviated by employing HOSMC strategies. The control law design is based on a super-twisting algorithm (STA) and a real-twisting algorithm (RTA) with variable gains. The proposed control techniques inherit the property of robustness and successfully deal with the nonlinear behavior of the system, erratic nature of the wind speed, external disturbances as well as model uncertainties. Also, the significance of smooth control action and variable gains strongly reduce the chattering effect. For a given reference speed, the generator speed and its missing derivative are retrieved by using a uniform robust exact differentiator (URED). The performance validation and effectiveness of the proposed control techniques is supported by Matlab/Simulink simulations, carried out under varying wind speed, parametric variations, and load variations.