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Research Papers

Individual Blade Pitch Control for the Controls Advanced Research Turbine (CART)

[+] Author and Article Information
Karl A. Stol, Wenxin Zhao

Department of Mechanical Engineering, The University of Auckland, Private Bag 92019, New Zealand

Alan D. Wright

 National Renewable Energy Laboratory, 1618 Cole Boulevard, Golden, CO 80401-3393

J. Sol. Energy Eng 128(4), 498-505 (Jul 26, 2006) (8 pages) doi:10.1115/1.2349542 History: Received April 13, 2006; Revised July 26, 2006

Pitching the individual blades of a horizontal-axis wind turbine allows control of asymmetric aerodynamic loads, which in turn influences structural loads in the nonrotating frame such as tower side-side bending. These loads are not easily controlled by traditional collective pitch algorithms. This paper presents the design of individual pitch control systems for implementation on the Controls Advanced Research Turbine (CART) in Colorado to verify controller performance for load attenuation. The control designs are based on linear time-periodic state-space models of the turbine and use optimal control methods for gain calculation. Comparisons are made between new individual pitch, new collective pitch, and baseline controller performance in both above rated and below rated wind conditions. Results from simulations show the potential of individual pitch to reduce tower side-side fatigue damage in above rated wind speeds (by 70% compared to baseline control) but with no improvement over collective pitch in below rated wind speeds. Fatigue load reductions in tower fore-aft, shaft torsion, and blade flap are also observed. From 13h of field testing, both collective and individual pitch controllers achieve a reduction in fatigue damage. However, the superior performance of individual pitch control observed in simulation was not verified by the field test results.

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Copyright © 2006 by American Society of Mechanical Engineers
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References

Figures

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Figure 2

SYMDYN DOFs and control inputs for CART modeling

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Figure 3

Linearization point locations on the approximate CART power curve

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Figure 4

Hub-height wind speeds in simulation

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Figure 5

Controller performance in region 2 simulations

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Figure 6

Typical blade pitch variation in region 2 simulations (SYMDYN )

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Figure 7

Tower fore-aft bending load spectrum in region 2 simulations (SYMDYN )

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Figure 8

Controller performance in region 3 simulations

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Figure 9

Tower fore-aft bending load spectrum in region 3 simulations (SYMDYN )

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Figure 10

Tower side-side bending load spectrum in region 3 simulations (SYMDYN )

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Figure 11

Low-speed shaft torsion spectrum in region 3 simulations (SYMDYN )

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Figure 12

Typical blade pitch variation in region 3 simulations (SYMDYN )

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Figure 13

Controller performance in region 2 field tests

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Figure 14

Controller performance in region 3 field tests

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