Enhancement of fault ride through capabilities for grid-connected DFIG-based wind farms using nonlinear adaptive backstepping controllers

In this paper, nonlinear adaptive backstepping controllers are designed for grid-connected wind energy conversion systems (WECSs) with doubly-fed induction generators (DFIGs) in order to enhance the fault ride through (FRT) capability. The main control objectives are to ensure the desired power injection (both active and reactive) into the grid while enhancing the FRT capability. The proposed adaptive controllers are designed for grid-side and rotor-side converters by considering dynamics of these converters along with the dynamic of the DC-link voltage. These controllers are designed to provide robustness against parametric uncertainties and for this purpose, all relevant parameters are considered as unknown. The unknown parameters are estimated through the adaptation laws and these adaptation laws along with the control actions for converters are obtained in such a way that the convergence of different physical properties of wind farms is ensured. The effectiveness of the proposed control scheme is validated on a single DFIG-based 9 MW WECS by applying severe three-phase short-circuit faults on the connection point of the wind farm. The performance of the proposed controller is also compared with an existing adaptive sliding mode control (EASMC) scheme in terms of active power injection, reactive power support, and voltage sag at the point of common coupling (PCC) along with fluctuations in the DC-bus voltage.