Model-based Aeroservoelastic Design and Load Alleviation of Large Wind Turbines

Abstract

This paper presents an aeroservoelastic modeling approach for dynamic load alleviation in large wind turbines with trailing-edge aerodynamic surfaces. The tower, potentially on a moving base, and the rotating blades are modeled using geometrically non-linear composite beams, which are linearized around reference conditions with arbitrarily-large structural displacements. Time-domain aerodynamics are given by a linearized 3-D unsteady vortexlattice method and the resulting dynamic aeroelastic model is written in a state-space formulation suitable for model reductions and control synthesis. A linear model of a single blade is used to design a Linear-Quadratic-Gaussian regulator on its root-bending moments, which is finally shown to provide load reductions of about 20% in closed-loop on the full wind turbine non-linear aeroelastic model.

Nonlinear Aeroelastic Modeling and Analysis of Flexible Wind Turbine Blades

“…The results are compared with the data from Jonkman et al 22 and Ng et al 23 and listed in Table 1. From the table, it can be seen that the results from the current formulation closely correlate with the other code packages (FAST 22 and SHARP 23 ) and commercial software (ADAMS).…”

Nonlinear Modal Condensation of Large Finite Element Models: Application of Hodges’s Intrinsic Theory

“…7 shows the first two torsional modes in terms of intrinsic variables: angular velocity φ φ φ 1 , torsional moment φ φ φ 2 , angular momentum ψ ψ ψ 1 , and torsional curvature ψ ψ ψ 2 . The chosen lumped mass model splits 16.85 (7) 16.87 (7) 17.03 (7) 17.03 (7) 3 r d x-y bending 46.55 (11) 46.64 (13) (146) the mass equally along all 30 notes, which gives nearly twice the angular momentum at the free end compared to the condensation from a distributed mass, and, more interestingly, a better matching between angular velocity and curvatures at the free end is observed between the beam and the shell with distributed mass. Fig.…”

“…Nonlinear formulations based on displacements [4], strains [5] and mixed intrinsic formulations [6] have been developed and applied to a wide range of situations and vehicles. They have provided relevant insight into the analysis of radical new configurations [7][8][9], nonlinear aeroelasticity [10], and design of large wind turbines [11,12].…”

Model-based aeroelastic analysis and blade load alleviation of offshore wind turbines

“…The use of a clamped blade for controller design does neglect important couplings, particularly rigid-body motion at its root representative of tower motion. In a recent paper by Ng, Hesse, Palacios, Graham, and Kerrigan (2014b), this control model was augmented with rigid body motion at its root. The closed-loop results on the full turbine were no better than the base case controller synthesized without rigid-body motions, indicating gust disturbance dominating the response of the system and justifies the use of the clamped blade for controller design.…”

“…The numerical verification of the proposed aeroelastic model for the land-based NREL turbine was performed in Ng et al (2015) and Ng et al (2014b). To verify implementation of the floating conditions, a regular Airy wave of height 6 m and period 10 s was simulated on the floating turbine.…”