Design Optimization of Wind Turbine Blades under Unsteady Dynamics

Abstract

This report presents a non-linear dynamic aero-servo-structural optimization framework applied to wind turbine blades under unsteady loads. The performances of the optimization with the Nested Analysis and Design (NAND) approach and the Simultaneous Analysis and Design (SAND) approach are investigated and compared.
The optimal blade design is described with a focus on the impact of the coupling
between control and structure introduced in the analysis model. The aerodynamic model for the loads is based on the Blade Element Momentum theory. The structural model for the blade is based on the nite element method and on a simplied cross section analysis of the internal blade structure. The optimization problem aims at reducing the mass of the blade within constraints on the power, the tip displacement and the pitch angle, by varying the chord and the control parameters. The optimization with the NAND approach is run using a Sequential Quadratic Programming Algorithm whereas the Interior-point algorithm is used for the SAND approach.
This study shows that adding the control strategy as a design variable allows a relaxation of the structural constraints and further mass reduction. The SAND approach was found to be less robust and less efficient than the NAND approach.