Stopping a wind turbine rotor using pre-set pitch rates

Patent metadata

Field	Value
Publication number	US-11959460-B2
Application number	US-202017779114-A
Country	US
Kind code	B2
Filing date	Nov 20, 2020
Priority date	Nov 21, 2019
Publication date	Apr 16, 2024
Grant date	Apr 16, 2024

Abstract

Control of a wind turbine in a stop process where a stop controller is used to pitch the blades at a number of pre-set pitch rates including a first pitch rate and a second pitch rate. The stop controller is arranged to access desired pitch angles of the stopping process and add an envelope band to the desired pitch angles. In the stop process, pitching at a selected pitch rate among the number of pre-set pitch rates is performed, and the pitch rate is changed according to criteria to keep the pitch value within the envelope band.

First claim

The invention claimed is:

1. A method for controlling a wind turbine, the wind turbine comprises a rotor with one or more pitch adjustable rotor blades and a stop controller configured to control the one or more pitch adjustable rotor blades towards a feathering position in response to a rotor stop signal as part of a stopping process that reduces speed of the rotor, and wherein the stop controller is arranged to pitch the one or more pitch adjustable rotor blades at a number of pre-set pitch rates including a first pitch rate and a second pitch rate, the second pitch rate being lower than the first pitch rate, wherein the method comprises:
accessing desired pitch angles of the stopping process, the desired pitch angles defining a pitch trajectory across an entire duration of the stopping process;
defining an envelope band of the pitch trajectory by adding positive values and negative values to the desired pitch angles, thereby defining an upper band and a lower band of the pitch trajectory across the entire duration, or until a termination criterion has been reached; and
operating the stop controller to:
move the one or more pitch adjustable rotor blades at a selected pitch rate among the number of pre-set pitch rates until a pitch angle signal is outside a pitch angle value defined by the envelope band such that:
when the pitch angle signal is larger than the upper band at a specific time, the selected pitch rate is changed to the second pitch rate; and
when the pitch angle signal is smaller than the lower band at a specific time, the selected pitch rate is changed to the first pitch rate.

2. The method of claim 1 , wherein the stop controller is arranged to move each of the one or more pitch adjustable rotor blades individually in accordance with the pitch angles defined by the envelope band.

3. The method of claim 1 , wherein the desired pitch angles are based on a desired collective pitch angle setting and a desired individual pitch angle setting.

4. The method of claim 3 , wherein the desired individual pitch angle setting is only applied if a required magnitude is above a threshold.

5. The method of claim 1 , wherein the desired pitch angles are predefined for the entire duration of the stopping process.

6. The method of claim 1 , wherein the desired pitch angles are determined during the stopping process.

7. The method of claim 6 , wherein the desired pitch angles are determined based on a time duration or sensor input.

8. The method of claim 1 , wherein upon receipt of the rotor stop signal at the stop controller, the one or more pitch adjustable rotor blades with a pitch angle inside the envelope band or a pitch angle lower than the lower band are set to move with a highest pitch rate among the number of pre-set pitch rates, and the one or more pitch adjustable rotor blades with a pitch angle larger than the upper band are set to move with a lowest pitch rate among the number of pre-set pitch rates.

9. The method of claim 1 , wherein a band width of the envelope band is changed, either at specified times in the stopping process or progressively as the stopping process is progressing.

10. The method of claim 1 , wherein upon reaching the termination criterion in the stopping process, the pitch angle is controlled to pitch the one or more pitch adjustable blades at one of the pre-set pitch rates without taking the envelope band into account.

11. The method of claim 10 , wherein the pitch angles are in a first process controlled to align all pitch angles, and in a second process controlled to pitch at a same pitch rate.

12. The method of claim 1 wherein the stop controller is implemented as a safety controller.

13. The method of claim 1 wherein the desired pitch angles of the stopping process are determined based on a stored pitch angle signal, wherein operating the stop controller further comprises:
prior to receipt of the rotor stop signal, generating the stored pitch angle signal using pitch angle signals for each of the one or more pitch adjustable rotor blades for at least a fraction of a rotor revolution;
either prior to receipt of the rotor stop signal, or upon receipt of the rotor stop signal, determining at least one periodic component of the stored pitch angle signal; and
after determining the at least one periodic component, implementing the stopping process by controlling the one or more pitch adjustable rotor blades towards the feathering position using a pitch control signal containing the at least one periodic component.

14. A wind turbine comprising a control system and a rotor with one or more pitch adjustable rotor blades, the control system being arranged for controlling the wind turbine in response to a rotor stop signal, wherein the control system comprises:
a stop controller arranged for controlling the one or more pitch adjustable rotor blades towards a feathering position in response to the rotor stop signal as part of a stopping process, and wherein the stop controller is arranged to pitch the one or more pitch adjustable rotor blades at a number of pre-set pitch rates including a first pitch rate and a second pitch rate, the second pitch rate being lower than the first pitch rate;
wherein the stop controller is arranged to:
access desired pitch angles of the stopping process, the desired pitch angles defining a pitch trajectory across an entire duration of the stopping process;
define an envelope band of the pitch trajectory by adding positive values and negative values to the desired pitch angles, thereby defining an upper band and a lower band of the pitch trajectory across the entire duration, or until a termination criterion has been reached;
move the one or more pitch adjustable rotor blades at a selected pitch rate among the number of pre-set pitch rates until a pitch angle signal is outside a pitch angle value defined by the envelope band such that:
when the pitch angle signal is larger than the upper band at a specific time, the selected pitch rate is changed to the second pitch rate; and
when the pitch angle signal is smaller than the lower band at a specific time, the selected pitch rate is changed to the first pitch rate.

15. The wind turbine of claim 14 , wherein the stop controller is arranged to move each of the one or more pitch adjustable rotor blades individually in accordance with the pitch angles defined by the envelope band.

16. The wind turbine of claim 14 , wherein the desired pitch angles are based on a desired collective pitch angle setting and a desired individual pitch angle setting.

17. The wind turbine of claim 16 , wherein the desired individual pitch angle setting is only applied if a required magnitude is above a threshold.

18. A computer program product comprising a non-transitory computer readable medium having software code which, is adapted to control a wind turbine comprising a rotor with one or more pitch adjustable rotor blades, the computer program product being adapted to perform an operation for controlling the wind turbine, the operation comprising:
implementing a stopping process by a stop controller in response to a rotor stop signal, the stopping process reducing speed of the rotor by controlling the one or more pitch adjustable rotor blades towards a feathering position at a number of pre-set pitch rates including a first pitch rate and a second pitch rate, the second pitch rate being lower than the first pitch rate, wherein the stop controller is configured to:
access desired pitch angles of the stopping process, the desired pitch angles defining a pitch trajectory

Assignees

• Vestas Wind Sys As

Inventors

• Hammerum Keld
• Jeppesen Christian
• Sowman Jon

Classifications

• F03D7/0252 Primary

  with aerodynamic drag devices on the blades · CPC title

• F03D7/0224

  Adjusting blade pitch · CPC title

• F05D2260/70

  Adjusting of angle of incidence or attack of rotating blades · CPC title

• F03D7/0264 Primary

  for stopping; controlling in emergency situations (orientating out of wind F03D7/0208) · CPC title

• F03D7/024

  of individual blades · CPC title