Stability limits for a full wind turbine equipped with trailing edge systems

by Thomas Buhl, Mac Gaunaa, Leonardo Bergami and Peter B. Andersen

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Outline

• Motivation• 2D stability• 3D stability• Results• Conclusion

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Motivation

Complex terrain CFD by Dr. Bechmann Risø

Siemens Wind power

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Motivation

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Adaptive trailing edges

From 2003 to today: three large research projectsinvolving more than 10

researchers,6 master thesis and 3 Ph.d’s

Inspiration Not applicable!

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Typical turbine layout

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Controller

”aerodynamic” controller part

”elastic” controller part

”pitch” controller part

”power” controller part

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Motivation

Load reduction on Upwind turbine – by P. B. Andersen

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Wind tunnel results

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2D stability

2D stability results from L. Bergami and M. Gaunaa

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Full turbine stability Results-Original turbine no flaps

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Full turbine stability Results-Original turbine with and without flaps

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Moving the center of gravity

Figures made by Li Na in ADAPWING2 project funded by Danish Research Council

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Moving the center of gravity

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2D Stability-Moving the center of gravity

From: Hansen, M.H., Aeroelastic instability problems for wind turbines.

Wind Energy (2007) 10 , 551-577

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Moving the center of mass

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Full turbine stability Results-Moving the center of gravity

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Full turbine stability Results-Moving the center of gravity

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Conclusions• Results from 2D studies show that adding flap control generally lowers

the stability limits• Results from 2D show that the effects of adding elastic trailing edges are

not trivial. Possibility of drastically lowered flutter velocities.

• The reference turbine is very stable.• The full turbine results show that the critical tip speed for which instability

occurs is lower for turbines equipped with trailing edge flaps compared to the turbine without.

• In most of the instability cases found an artificial propeller mode (large forward blade deflections) occurs.

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Future work

• Emergency stop• future extensions to this work should focused also on the controller

parameters and the influence of these on the stability limits– Elastic flaps– Aggresivily tuned flap control – Less stable reference turbine

• This work is partially funded by

Acknowledgement