Robust second order sliding mode controller for grid connected DFIG system

Abstract

Grid-connected DFIG run by variable-speed wind turbine exhibits highly nonlinear behaviour causing large ripple or chattering in controlled quantity resulting into deterioration of mechanical components. Therefore, development of robust control scheme for DFIG is a challenging task in such a highly perturbed environment. This thesis presents robust Second-Order Sliding Mode (SOSM) scheme based on Super-Twisting Algorithm (STA) for direct control of stator active and reactive powers of grid-connected DFIG in stationary reference frame with two-fold objectives. The first one is to control stator active power of DFIG in order to get wind turbine extract optimum wind power and the second one is to control the stator reactive power of the DFIG to follow the grid demand. This approach based on SOSM control attenuates chattering in controlled quantities due to continuous control action and provide robust dynamic performance. This PhD thesis would be useful further to develop wind farm control strategies which are most important in the development of new grid codes to be designed by Transmission System Operators (TSOs) in the country in order to make wind farms run as conventional power plants. newline newline