Perturbation estimation based nonlinear adaptive control of a full rated converter wind-turbine for fault ride-through capability enhancement

The fault ride-through capability (FRTC) of a full rated converter wind turbine relies on the operation and control of the grid-side converter. To enhance the FRTC of the wind power generation system (WPGS), this paper investigates a novel controller for the grid-side converter, based on nonlinear adaptive control (NAC). Lumped perturbation terms are defined in the NAC to include all unknown and time-varying dynamics and external disturbances of the WPGS, and can be estimated by designing perturbation observers. The estimate of the perturbation terms is used to compensate the real perturbations and finally achieve an adaptive feedback linearizing control of the original nonlinear system, without requiring the accurate system model and full state measurements. The proposed NAC is an output feedback control and adaptive to parameter uncertainties and unknown nonlinearities of the WPGS, and time-varying external disturbances including grid faults, voltage dips and intermittent wind power inputs. The effectiveness of the proposed NAC is verified by simulation studies and compared with conventional vector controller and feedback linearizing controller, which show that it can provide better FRTC even though the grid voltage levels are far below their nominal values.