Method for operating a wind turbine

Patent metadata

Field	Value
Publication number	US-11401914-B2
Application number	US-202016900570-A
Country	US
Kind code	B2
Filing date	Jun 12, 2020
Priority date	Jun 19, 2019
Publication date	Aug 2, 2022
Grant date	Aug 2, 2022

Abstract

Provided is a method for operating a wind turbine that includes a rotor operable with variable rotor speed and having rotor blades with adjustable pitch angles. Wind causes a rotor thrust acting on the rotor depending on the rotor speed and depending on a common pitch angle. In partial load, when the wind is below rated speed, the turbine is controlled by a rotor speed curve, defining the rotor speed for each operating point of the turbine. In a normal mode when the operation of the turbine is not throttled, a normal rotor speed curve in combination with a normal common pitch angle is used, and in a throttled mode when the thrust is to be limited, a throttled rotor speed curve, different from the normal rotor speed curve, in combination with a throttled common pitch angle, different from the normal common pitch angle, is used to reduce the thrust.

First claim

The invention claimed is:

1. A method for operating a wind turbine, comprising:
controlling the wind turbine, in partial load when wind speed is below a rated wind speed, using a rotor speed curve that defines a rotor speed for a respective operating point of the wind turbine and using a common pitch angle, wherein the wind turbine includes a rotor operable with variable rotor speed and having rotor blades with adjustable pitch angles, wherein the adjustable pitch angles are represented by the common pitch angle, and wherein the wind turbine produces electrical power from wind and the wind causes a rotor thrust, acting on the rotor, that depends on the rotor speed and the common pitch angle, wherein:
during the partial load and in a normal operational mode when the operation of the wind turbine is not throttled, a normal rotor speed curve is used as the rotor speed curve and a normal common pitch angle is used as the common pitch angle, and
during the partial load and in a throttled operational mode when the rotor thrust is to be limited, a throttled rotor speed curve, different from the normal rotor speed curve, is used as the rotor speed curve, and a throttled common pitch angle, different from the normal common pitch angle, is used as the common pitch angle to reduce the rotor thrust, wherein:
operation of the rotor is associated with a power coefficient,
a relationship between the power coefficient and a rotor thrust coefficient is defined as an optimization criterion, and
the throttled rotor speed curve is configured such that the optimization criterion is maximized.

2. The method according to claim 1 , wherein the rotor speed curve defines a relationship between the rotor speed and one of:
electrical power to be produced,
a generator torque to be set, or
the wind speed.

3. The method according to claim 1 , comprising:
limiting or reducing the rotor thrust by increasing the throttled common pitch angle with respect to the normal common pitch angle; or
configuring the throttled rotor speed curve such that for a given throttled pitch angle the electrical power is maximized.

4. The method according to claim 1 , wherein:
the optimization criterion is defined according to at least one of:
a first ratio of the power coefficient to the rotor thrust coefficient,
a second ratio of a first function depending on the power coefficient to a second function depending on the rotor thrust coefficient, and
a third ratio of a weighted power coefficient to a weighted rotor thrust coefficient.

5. The method according to claim 1 , wherein the throttled rotor speed curve is configured such that, depending on the throttled common pitch angle, a tip speed ratio is set such that the electrical power is maximized.

6. The method according to claim 5 , wherein the throttled rotor speed curve is configured such that, depending on the throttled common pitch angle, the tip speed ratio is set such that a ratio of the power coefficient to the rotor thrust coefficient is maximized.

7. The method according to claim 5 , comprising:
configuring the throttled rotor speed curve by applying an optimization criterion, wherein the optimization criterion is a pitch angle curve of the common pitch angle depending on the tip speed ratio and depending on the ratio of the power coefficient to the rotor thrust coefficient, wherein all possible common pitch angles depending on the tip speed ratio and depending on the ratio of the power coefficient to the rotor thrust coefficient form a three-dimensional surface and tuples of tip-speed-ratio values and pitch angle values correspond to a curve following a gradient.

8. The method according to claim 1 , wherein the rotor speed curve is configured as depending on a ratio of the power coefficient to the rotor thrust.

9. The method according to claim 1 , comprising:
controlling the wind turbine in a full load, when the wind speed is at or above the rated wind speed:
during the full load, operating the wind turbine in the normal operational mode with a rated rotor speed, a rated generator torque and rated power; and
during the full load, operating the wind turbine in the throttled operational mode with a throttled rotor speed below the rated rotor speed, increased generator torque above the rated generator torque or the rated power.

10. The method according to claim 1 , wherein:
a set of throttled rotor speed curves is provided, each throttled rotor speed curve comprises the throttled common pitch angle; and
for operating the wind turbine, one throttled rotor speed curve of the set of throttled rotor speed curves is selected depending on an amount of the rotor thrust to be limited.

11. The method according to claim 1 , wherein in a transient operation where operation shifts from the partial load to a full load, the throttled common pitch angle increases with increasing wind speed.

12. The method according to claim 11 , wherein in the transient operation the pitch angle increases depending on an increase of the produced electrical power.

13. The method according to claim 12 , wherein the pitch angle increases with a predefined pitch angle to power slope.

14. The method according to claim 1 , comprising:
operating in the throttled operational mode based on at least one criterion or information from a list including:
an azimuth position of the wind turbine,
the wind speed,
gustiness intensity or turbulence intensity,
a wake-effect, according to which the wind turbine influences a wind field of a further wind turbine arranged in lee of the wind turbine,
a first signal received from the further wind turbine arranged in lee of the wind turbine,
a second signal received from a central farm controller of a wind farm including the wind turbine, and
a requirement for reducing noise emission.

15. A first wind turbine comprising:
a rotor operable with variable rotor speed and having rotor blades with adjustable pitch angles, the adjustable pitch angles being represented by a common pitch angle; and
a generator configured to generate electrical power from wind, wherein:
the wind causes a rotor thrust that acts on the rotor and that depends on the rotor speed and the common pitch angle,
a wind turbine controller is configured to operate the first wind turbine such that in partial load, when the wind is below rated wind speed, the first wind turbine is controlled using a rotor speed curve, defining the rotor speed for a respective operating point of the first wind turbine,
during the partial load and in a normal operational mode when the operation of the first wind turbine is not throttled, a normal rotor speed curve is used as the rotor speed curve and a normal common pitch angle is used as the common pitch angle, and
during the partial load and in a throttled operational mode when the rotor thrust is to be limited, a throttled rotor speed curve, different to the normal rotor speed curve, is used as the rotor speed curve and a throttled common pitch angle, different to the normal common pitch angle, is used as the common pitch angle to reduce the rotor thrust, wherein:
operation of the rotor is associated with a power coefficient,
a relationship between the power coefficient and a rotor thrust coefficient is defined as an optimization criterion, and
the throttled rotor speed curve is configured such that the optimization criterion is maximized.

16. An arrangement of wind turbines comprising:
the first wind turbine according to claim 15 ;
a second wind turbine arranged in proximity of the first wind turbine; and
a communication interface configured

Assignees

• Wobben Properties Gmbh

Inventors

• Lehn Andreas
• Bekiropoulos Dimitrios

Classifications

• F05B2270/32

  Wind speeds · CPC title

• F05B2270/1033

  Power (if explicitly mentioned) · CPC title

• F03D7/0276 Primary

  controlling rotor speed, e.g. variable speed · CPC title

• F03D9/25

  the apparatus being an electrical generator (F03D9/22 takes precedence) · CPC title

• F03D7/048

  controlling wind farms · CPC title