# US 12,006,914 B2 · Controlling power output of a wind turbine at below-rated wind speed

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- Number: US 12,006,914 B2
- Document ID: US12006914B2
- Status: Granted
- Kind: B2
- Application number: 17/623,078
- Filed: 2020-06-22
- Published: 2022-08-18
- Granted: 2024-06-11
- Earliest claimed: 2019-06-27
- Assignees: Vestas Wind Systems A/S
- Applicants: Vestas Wind Systems A/S
- Inventors: Fabio Caponetti; James Alexander Nichols; Benjamin Rowlinson
- Web page: https://patentgrep.com/patent/US12006914B2

## CPC

- F03D 7/0224: {Adjusting blade pitch}
- F03D 7/028: {controlling wind motor output power}
- F05B 2270/1033: Power (if explicitly mentioned)
- F05B 2270/32: Wind speeds
- F05B 2270/327: Rotor or generator speeds
- F05B 2270/331: Mechanical loads
- Y02E 10/72: Wind turbines with rotation axis in wind direction
- F03D: WIND MOTORS
- F05B: INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

There is provided a method of controlling power output of a wind turbine at below-rated wind speed, the method comprising: determining an indication of blade torsion of one or more rotor blades of the wind turbine in dependence on wind speed and/or rotor speed; determining a torsion-corrected blade pitch based on the indication of blade torsion; and using the torsion-corrected blade pitch to control pitch the one or more rotor blades.

## Claims

### Claim 1

A method of controlling power output of a wind turbine at below-rated wind speed, the method comprising:
determining an indication of blade torsion of one or more rotor blades of the wind turbine based on a predetermined relationship between the blade torsion and at least one of a wind speed and a rotor speed;
calculating a tip-speed ratio based on the rotor speed and the wind speed;
determining a torsion-corrected blade pitch based on the indication of blade torsion and the tip-speed ratio, wherein determining the torsion-corrected blade pitch comprises determining a first blade pitch based on the tip-speed ratio, determining a second blade pitch based on the indication of blade torsion, and comparing the first and second blade pitches to determine the torsion-corrected blade pitch; and
using the torsion-corrected blade pitch to control pitch of the one or more rotor blades.

### Claim 2 (depends on 1)

The method of claim 1, wherein one or both of the first and second blade pitches is determined using a look-up table.

### Claim 3 (depends on 1)

The method of claim 1, wherein the second blade pitch is a blade pitch offset, and wherein determining the torsion-corrected blade pitch comprises adjusting the first blade pitch by the blade pitch offset.

### Claim 4 (depends on 3)

The method of claim 3, wherein determining the second blade pitch comprises:
determining a wind speed blade pitch offset based on an indication of blade torsion determined in dependence on the wind speed;
determining a rotor speed blade pitch offset based on an indication of blade torsion determined in dependence on the rotor speed; and
calculating the second blade pitch as a sum of the wind speed and rotor speed blade pitch offsets.

### Claim 5 (depends on 3)

The method of claim 3, wherein determining the first blade pitch comprises:
determining a tip-speed ratio blade pitch based on the tip-speed ratio;
determining a wind-speed blade pitch based on the wind speed and/or determining a rotor-speed blade pitch based on the rotor speed; and
calculating the first blade pitch as a minimum of the tip-speed ratio blade pitch and the determined wind-speed blade pitch and/or rotor-speed blade pitch.

### Claim 6 (depends on 1)

The method of claim 1, wherein the torsion-corrected blade pitch is determined to be a minimum of the first and second blade pitches.

### Claim 7 (depends on 1)

The method of claim 1, wherein the indication of blade torsion is determined in dependence on blade root flapwise bending moment.

### Claim 8 (depends on 1)

The method of claim 1, wherein the indication of blade torsion is determined in dependence on a current operating point of the wind turbine.

### Claim 9 (depends on 1)

The method of claim 1, wherein determining the torsion-corrected blade pitch comprises:
calculating an average torsion along a length of the one or more rotor blades based on the indication of blade torsion; and,
determining the torsion-corrected blade pitch based on the average torsion along the length of the one or more rotor blades.

### Claim 10 (depends on 1)

The method of claim 1, wherein the indication of blade torsion is calculated based on a model of the one or more rotor blades.

### Claim 11 (depends on 1)

The method of claim 1, wherein controlling the one or more rotor blades comprises pitching the one or more rotor blades to the torsion-corrected blade pitch.

### Claim 12

A controller for controlling power output of a wind turbine at below-rated wind speed, the controller being configured to:
determine an indication of blade torsion of one or more rotor blades of the wind turbine in dependence on wind speed and rotor speed;
calculate a tip-speed ratio based on the rotor speed and the wind speed;
determine a torsion-corrected blade pitch based on the indication of blade torsion and the tip-speed ratio, wherein determining the torsion-corrected blade pitch comprises determining a first blade pitch based on the tip-speed ratio, determining a second blade pitch based on the indication of blade torsion, and comparing the first and second blade pitches to determine the torsion-corrected blade pitch; and
send a control signal to command pitch control of the one or more rotor blades using the torsion-corrected blade pitch.

### Claim 13 (depends on 12)

The controller of claim 12, wherein one or both of the first and second blade pitches is determined using a look-up table.

### Claim 14 (depends on 12)

The controller of claim 12, wherein the second blade pitch is a blade pitch offset, and wherein determining the torsion-corrected blade pitch comprises adjusting the first blade pitch by the blade pitch offset.

### Claim 15 (depends on 12)

The controller of claim 12, wherein in determining the first blade pitch, the controller is configured to:
determine a tip-speed ratio blade pitch based on the tip-speed ratio;
determine a wind-speed blade pitch based on the wind speed and/or determining a rotor-speed blade pitch based on the rotor speed; and
calculate the first blade pitch as a minimum of the tip-speed ratio blade pitch and the determined wind-speed blade pitch and/or rotor-speed blade pitch.

### Claim 16 (depends on 12)

The controller of claim 12, wherein the torsion-corrected blade pitch is determined to be a minimum of the first and second blade pitches.

### Claim 17 (depends on 12)

The controller of claim 12, wherein in determining the torsion-corrected blade pitch, the controller is configured to:
calculate an average torsion along a length of the one or more rotor blades based on the indication of blade torsion; and,
determine the torsion-corrected blade pitch based on the average torsion along the length of the one or more rotor blades.

### Claim 18

A wind turbine, comprising:
a tower;
a nacelle disposed on the tower;
a rotor extending from the nacelle and having a plurality of blades disposed on a distal end thereof;
a controller configured to:
determine an indication of blade torsion of one or more rotor blades of the wind turbine in dependence on wind speed and rotor speed;
calculate a tip-speed ratio based on the rotor speed and the wind speed;
determine a torsion-corrected blade pitch based on the indication of blade torsion and the tip-speed ratio, wherein determining the torsion-corrected blade pitch comprises determining a first blade pitch based on the tip-speed ratio, determining a second blade pitch based on the indication of blade torsion, and comparing the first and second blade pitches to determine the torsion-corrected blade pitch; and
send a control signal to command pitch control of the one or more rotor blades using the torsion-corrected blade pitch.

### Claim 19 (depends on 18)

The wind turbine of claim 18, wherein in determining the first blade pitch, the controller is configured to:
determine a tip-speed ratio blade pitch based on the tip-speed ratio;
determine a wind-speed blade pitch based on the wind speed and/or determining a rotor-speed blade pitch based on the rotor speed; and
calculate the first blade pitch as a minimum of the tip-speed ratio blade pitch and the determined wind-speed blade pitch and/or rotor-speed blade pitch.

### Claim 20 (depends on 18)

The wind turbine of claim 18, wherein the torsion-corrected blade pitch is determined to be a minimum of the first and second blade pitches.