Blade Load Mitigation Control Design for a Wind Turbine Operating in the Path of Vortices

Turbulence generated in the stable atmospheric boundary layer can contain vorticity that adversely affects wind turbine blade fatigue life. We investigated advanced control algorithms that mitigate the vortex/wind turbine interaction. State space control designs can meet multiple control objectives such as maintaining power regulation while mitigating blade flap bending moment amplitude. We implemented disturbance accommodating control (DAC) methods in a structural dynamics code to mitigate blade loads and maintain constant power production in above-rated wind speeds. As a best-case scenario, we implemented a disturbance model that incorporated very detailed vortex characteristics in full-state feedback. This reduced equivalent fatigue load as much as 30% compared to a standard proportional-integral (PI) controller. A realizable DAC controller that incorporates only the vertical shear component of the vortex reduced loads by 9% compared to a PI controller, and as much as 29% when the vortex was superimposed over normal turbulence.

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