Wind turbine with a wind velocity measurement system

• US 6,320,272 B1
• Filed: 01/14/2000
• Issued: 11/20/2001
• Est. Priority Date: 03/26/1997
• Status: Expired due to Term

• Current Assignee: Forskningscenter RISO
• Original Assignee: Forskningscenter RISO
• Inventors: Frandsen, Sten, Hansen, Jesper Kjær, Lading, Lars, Sangill, Ole
• Primary Examiner(s): Ponomarenko, Nicholas
• Application Number:
  US09/381,830
• Time in Patent Office: 676 Days
• Field of Search: 290/44, 290/43, 290/54, 290/55, 417/334, 416/31
• US Class Current: 290/44
• CPC Class Codes: F03D 17/00 Monitoring or testing of wind motors, e.g. diagnostics testing during commissioning of wind motors F03D13/30
• CPC Class Codes: F03D 7/0224 Adjusting blade pitch
• CPC Class Codes: F03D 7/043 characterised by the type of control logic
• CPC Class Codes: F05B 2270/1016 in variable speed operation
• CPC Class Codes: F05B 2270/20 to optimise the performance of a machine
• CPC Class Codes: F05B 2270/32 Wind speeds
• CPC Class Codes: F05B 2270/805 Radars
• CPC Class Codes: G01P 5/26 by measuring the direct influence of the streaming fluid on the properties of a detecting optical wave
• CPC Class Codes: Y02E 10/72 Wind turbines with rotation axis in wind direction

Abstract

A wind turbine includes a laser wind velocity measurement system mounted on a nacelle of the wind turbine for determination of air velocities at the same relative position in front of the wind turbine, and which compensates for wind velocity changes prior to impingement of the air flow on the adjustable pitch wind turbine blades so that desired maximum tip speeds, tip speed ratios, and normalized power output C_p may be maintained.

Claims

1. A wind turbine, comprising:

a nacelle; and

a wind velocity measurement system which determines air velocities at a relative position in front of the wind turbine, said wind velocity measurement system including a laser anemometry system for emission of a laser light beam for illumination of particles in the air,

wherein the laser anemometry system is mounted on the nacelle to follow the motion of the nacelle so that the determination of the air velocity in front of the wind turbine is accomplished at a same relative position with respect to the nacelle.

2. A wind turbine according to claim 1, wherein the laser anemometry system includes

a laser for emission of the laser light beam for illumination of particles in the air;

a detector for detection of light emitted from particles that have been illuminated by the laser light beam, and

a signal processor connected to the detector for generating a velocity signal corresponding to the velocity of the particles based on the detected light.

3. A wind turbine according to claim 2, wherein the laser anemometry system is a Michelson interferometer type laser Doppler anemometer.

4. A wind turbine according to claim 2, wherein the light emitted from particles in the air is transmitted to the laser for perturbation of the power output of the laser, wherein the detector detects the light emitted from the particles that have interacted with the illuminating laser light by measuring the perturbed power output of the laser.

5. A wind turbine according to claim 4, wherein the laser comprises a tapered waveguide with an output window constituting a laser mirror and a focusing element.

6. A wind turbine according to claim 2, wherein the signal processor includes a frequency locked loop.

7. A wind turbine according to claim 1, comprising:

adjustable pitch blades,

a pitch controller for setting a desired blade pitch, the desired blade pitch being set according to a signal provided at an input of the pitch controller, and

a control system for controlling the output power generated by the wind turbine by control of blade pitch, said control system including

a control output connected to the input of the pitch controller,

a velocity input connected to an output of the velocity measurement system, and

a pitch processor for calculation of the desired blade pitch based on determined air velocity values and generation of a corresponding pitch control signal provided at the control output,

wherein the determination of air velocities in front of the wind turbine compensates for a delay in setting the desired blade pitch so that an actual blade pitch setting is set in accordance with an actual wind velocity at the adjustable pitch blades during operation of the wind turbine.

8. A wind turbine according to claim 7, wherein the pitch processor is adapted to generate a pitch signal so that a tip speed ratio is substantially equal to a desired ratio.

9. A wind turbine according to claim 7, wherein the pitch processor is adapted to generate a pitch control signal so that a tip speed can not exceed a maximum velocity value.

10. A wind turbine according to claim 8, wherein the pitch processor is adapted to generate a pitch control signal so that a tip speed can not exceed a maximum velocity value.

11. A wind turbine according to claim 7, wherein the pitch processor further comprises a data storage for storage of a first function of a shaft torque as a function of a blade pitch and wind speed for the wind turbine, and wherein the pitch processor is adapted to calculate the desired pitch utilizing the first function.

12. A wind turbine according to claim 7, wherein the pitch processor further comprises a data storage for storage of a second function of a normalized power output C_p as a function of a blade pitch and a tip speed ratio for the wind turbine, wherein the pitch processor is adapted to calculate the desired blade pitch utilizing the second function.

13. A wind turbine according to claim 12, wherein the pitch processor is further adapted to determine a pitch that, for a given tip speed ratio, substantially maximizes the normalized power output C_p.

14. A wind turbine according to claim 1, comprising:

a control system for controlling an output power generated by the wind turbine by control of a load connected to a power output of the wind turbine, said control system including

a control output connected to the load,

a velocity input connected to an output of the wind velocity measurement system, and

a processor for calculation of a desired load value based on the determined air velocity values at the position in front of the wind turbine and for generation of a corresponding load signal provided at the control output,

wherein use of the determined air velocity values by the processor compensates for a delay in setting the desired load value so that an actual load value setting is set in accordance with an actual wind velocity at a plurality of blades of the wind turbine during operation of the wind turbine.

15. A system for determination of a power curve of the wind turbine according to claim 1, comprising a power measurement system for determination of an output power generated by the wind turbine.

18. A wind turbine according to claim 1, wherein the wind velocity measurement system further comprises spatial scanning means for performing a measurement scan in front of the wind turbine by changing a relative position of a point where the measurement is performed so that information related to a vertical and/or horizontal wind velocity distribution in front of the wind turbine may be obtained.

19. The wind turbine of claim 1, wherein the relative position at which air velocities are determined is located in front of the wind turbine at a distance of 2.5 times a wind turbine rotor diameter.

20. The wind turbine according to claim 1, wherein the wind velocity measurement system includes a shutter mechanism to block reflection of the laser light beam from a wind turbine rotor.

16. A method of determining a characteristic power curve for a wind turbine, comprising:

mounting, on a nacelle of the wind turbine, a wind velocity measurement system including a laser anemometry system for determination of air velocities in a position in front of the wind turbine;

connecting a power measurement system for determination of an output power generated by the wind turbine, said power measurement system being connected between a power generator of the wind turbine and a load receiving the output power generated by the wind turbine; and

recording values of wind velocity determined by the wind velocity measurement system and corresponding output power values determined by the power measurement system.

21. The method of claim 16, further comprising determining a turbulence of an airflow in the position in front of the wind turbine.

22. The method of claim 16, wherein the position in front of the wind turbine is located at a distance of 2.5 times a wind turbine rotor diameter.

17. A method of controlling output power from a wind turbine, comprising:

mounting, on a nacelle of the wind turbine, a wind velocity measurement system which includes a laser anemometry system;

determining air velocities in a position in front of the wind turbine; and

providing determined velocity values to a power control system of the wind turbine.

23. The method of claim 17, wherein the position in front of the wind turbine is located at a distance of 2.5 times a wind turbine rotor diameter.

24. A wind turbine, comprising:

a nacelle; and

a wind velocity measurement system which determines air velocities at a relative position in front of the wind turbine, said wind velocity measurement system including a laser for emission of a laser light beam for illumination of particles in the air,

wherein the laser is mounted in a hub of the wind turbine to follow the motion of the nacelle so that the determination of the air velocity in front of the wind turbine is accomplished at a same relative position with respect to the nacelle.

25. A wind turbine, comprising:

a nacelle; and

a wind velocity measurement system which determines air velocities at a relative position in front of the wind turbine, said wind velocity measurement system including a laser for emission of a laser light beam for illumination of particles in the air,

wherein the laser is mounted in a hollow shaft of a hub of the wind turbine to follow the motion of the nacelle so that the determination of the air velocity in front of the wind turbine is accomplished at a same relative position with respect to the nacelle.