Optimization of power production in a wind turbine at below rated power

Patent metadata

Field	Value
Publication number	US-9683551-B2
Application number	US-201214369524-A
Country	US
Kind code	B2
Filing date	Dec 13, 2012
Priority date	Dec 29, 2011
Publication date	Jun 20, 2017
Grant date	Jun 20, 2017

Abstract

The rotor blades of a wind turbine each have a plurality of fiber-optic pressure variation sensors which can detect the onset of a stall condition. The output of the stall condition sensors is input to a stall count circuit which increases a stall count signal each time a stall indication is received. The stall count signal is decayed exponentially over time and the current signal is summed with the decayed signal from a previous sampling period to form a value from which a stall margin is determined. An λ:θ curve of tip speed to wind speed ratio λ against pitch angle reference θ is then determined from the stall margin.

First claim

What is claimed is:

1. A method of operating a wind turbine at below rated power, comprising:
sensing stall conditions using one or more stall condition sensors on wind turbine rotor blades;
determining a stall margin based on the sensed stall conditions, wherein the determination of the stall margin comprises determining a stall event count using a stall event counter based on outputs from the one or more stall condition sensors, the stall margin being determined from the stall event count, wherein the stall event count is dependent on the time between detected stall conditions output by the at least one stall condition sensor;
selecting a curve of tip to wind speed ratio against blade pitch angle according to the determined stall margin; and
varying the blade pitch angle of at least one of the wind turbine blades in accordance with the selected curve.

2. A method according to claim 1 , wherein the stall event counter increases the stall event count on detection of a stall condition by the at least one stall condition sensor, and decays the stall event count over time.

3. A method according to claim 2 , wherein an output from the at least one stall condition sensor is processed to determine an increase in a stall event signal, and scaled by an amount determined according to wind conditions.

4. A method according to claim 3 , wherein the processed and scaled output is summed with a processed and scaled output from a previous sampling time period weighted by an amount determined according to wind conditions.

5. A method according to claim 4 , wherein the summed outputs are mapped to a stall margin and the curve of tip speed to wind speed ratio against blade pitch angle determined from the mapped stall margin.

6. A method according to claim 5 , wherein the stall margin is varied between a nominal value and an optimal value depending on the stall event count output.

7. A method according to claim 3 , wherein a first constant is determined on the basis of wind speed and wind turbulence, and the first constant is used to scale the increase in the stall event signal.

8. A method according to claim 1 , wherein the at least one stall condition sensor comprises a plurality of stall condition sensors on each of the rotor blades of the wind turbine.

9. A method according to claim 8 , wherein the stall condition sensors are fibre-optic pressure variation sensors.

10. A method according to claim 9 , wherein the fibre-optic pressure variation sensors comprise a membrane arranged over an aperture in a blade surface and a fibre-optic light transmitter and a fibre-optic light receiver arranged within the aperture to detect vibration of the membrane by detecting fluctuations in the intensity of light received by the fibre-optic light receiver.

11. A method according to claim 1 , wherein the varying of the blade pitch angle of at least one of the wind turbine blades in accordance with the selected curve varies the pitch angle of all the blades by a common amount.

12. A control system for operating a wind turbine at below rated power, comprising:
one or more stall condition sensors for sensing stall conditions on wind turbine rotor blades;
a stall margin determination arrangement for determining a stall margin based on sensed stall conditions, wherein the arrangement for determining the stall margin comprises a stall event counter for determining a stall event count based on outputs from the one or more stall condition sensors, the stall margin being determined from the stall event count and the stall event count being dependent on the time between detected stall conditions output by the at least one stall condition sensor;
a controller for selecting a curve of tip to wind speed ratio against rotor blade pitch angle according to the determined stall margin; and
a pitch angle controller for varying the blade pitch angle of at least one of the rotor blades in accordance with the selected curve.

13. A control system according to claim 12 , wherein the stall event counter increases the stall event count on detection of a stall condition by the at least one stall condition sensor, and decays the stall event count over time.

14. A control system according to claim 13 , wherein the stall event counter determines an increase in a stall event signal from the at least one stall condition sensor, and the stall event signal is scaled according to wind conditions.

15. A control system according to claim 14 , comprising a summer for summing the scaled stall event signal with a scaled stall event signal from a previous sampling time period weighted by an amount determined according to wind conditions.

16. A control system according to claim 15 , comprising a device storing a map of stall margins and corresponding curves of tip speed to wind speed ratio against blade pitch angle.

17. A control system according to claim 16 , wherein the stall margin is varied between a nominal value and an optimal value depending on the stall event count.

18. A control system according to claim 14 , wherein a first constant is determined on the basis of mean wind speed and wind turbulence, and the first constant is used to scale the increase in the stall event signal.

19. A control system according to claim 12 , wherein the at least one stall sensor comprises a plurality of stall condition sensors on each of the rotor blades of the wind turbine.

20. A control system according to claim 19 , wherein the stall condition sensors are fibre-optic pressure variation sensors.

21. A control system according to claim 20 , wherein the fibre-optic pressure variation sensors comprise a membrane arranged over an aperture in a rotor blade surface and a fibre-optic light transmitter and a fibre-optic light receiver arranged within the aperture to detect vibration of the membrane by detecting fluctuations in the intensity of light received by the fibre-optic light receiver.

22. A control system according to claim 12 , wherein the pitch angle controller is a common pitch angle controller for varying of the blade pitch angle of the wind turbine blades in accordance with the selected curve by a common amount.

23. A wind turbine having a control system according to claim 12 .

Assignees

• Vestas Wind Sys As

Inventors

• Andersen Asger Svenning
• Thomsen Jesper Sandberg
• Kristoffersen Jacob Krogh
• Olesen Ib Svend
• Romblad Jonas

Classifications

• Y02E10/723

  Cross-Sectional Technologies · mapped topic

• F03D7/042

  by means of an electrical or electronic controller · CPC title

• F03D7/046

  with learning or adaptive control, e.g. self-tuning, fuzzy logic or neural network · CPC title

• F03D7/0256 Primary

  Stall control (adjusting the blades in stall position F03D7/0224) · CPC title

• F03D17/00

  Monitoring or testing of wind motors, e.g. diagnostics (testing during commissioning of wind motors F03D13/30) · CPC title