# US 11,441,542 B2 · Operating a wind turbine using estimated wind speed while accounting for blade torsion

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- Number: US 11,441,542 B2
- Document ID: US11441542B2
- Status: Granted
- Kind: B2
- Application number: 15/528,450
- Filed: 2015-11-20
- Published: 2017-11-09
- Granted: 2022-09-13
- Earliest claimed: 2014-11-21
- Assignees: Vestas Wind Systems A/S
- Applicants: Vestas Wind Systems A/S
- Inventors: Martin Atzler; Thomas Scheel; Lars Finn Sloth Larsen
- Web page: https://patentgrep.com/patent/US11441542B2

## CPC

- F03D 17/00: Monitoring or testing of wind motors, e.g. diagnostics (testing during commissioning of wind motors F03D13/30)
- F03D 7/0224: {Adjusting blade pitch}
- F03D 7/0276: {controlling rotor speed, e.g. variable speed}
- G01P 5/00: Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft (application of speed-measuring devices for measuring volume of fluid G01F)
- G05B 17/02: electric
- F05B 2240/221: with horizontal axis
- F05B 2270/327: Rotor or generator speeds
- F05B 2270/328: Blade pitch angle
- Y02E 10/72: Wind turbines with rotation axis in wind direction
- F03D: WIND MOTORS
- G01P: MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT (measuring or recording blood flow A61B5/02, A61B8/06; monitoring speed or deceleration of electrically-propelled vehicles B60L3/00; vehicle lighting systems adapted to indicate speed B60Q1/54; determining position or course in navigation, measuring ground distance in geodesy or surveying G01C; combined measuring devices for measuring two or more variables of movement G01C23/00; measuring velocity of sound G01H; measuring velocity of light G01J7/00; measuring direction or velocity of solid objects by reception or emission of radiowaves or other waves and based on propagation effects, e.g. Doppler effect, propagation time, direction of propagation, G01S; measuring speed of nuclear radiation G01T; measuring acceleration of gravity G01V; {measuring or recording the speed of trains B61L23/00; speed indicators incorporated in motor vehicles B60K35/00; measuring frequency or phase G01R; traffic control G08G})
- G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G)
- 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

A method for estimating a wind speed at a wind turbine is disclosed, said wind turbine comprising a rotor carrying a set of wind turbine blades, each wind turbine blade having a variable pitch angle. A blade torsion contribution, representing torsion introduced in the wind turbine blades, is derived, based on an obtained rotational speed, ω, of the rotor, and an obtaining a pitch angle, θ, of the wind turbine blades. An adjusted pitch angle, θ′, is calculated as a sum of the obtained pitch angle, θ, and the derived blade torsion contribution, and a wind speed, vest, is estimated, based on the obtained rotational speed, ω, and the calculated adjusted pitch angle, θ′. An accurate and reliable estimate for the wind speed is thereby obtained. The wind turbine may be controlled in accordance with the estimated wind speed, vest.

## Claims

### Claim 1

A method of controlling operation of a wind turbine comprising a rotor carrying a set of wind turbine blades, wherein each wind turbine blade of the set has a variable pitch angle, the method comprising:
obtaining a rotational speed of the rotor;
obtaining a pitch angle of the wind turbine blades;
deriving a blade torsion contribution based on the rotational speed and the pitch angle;
calculating an adjusted pitch angle as a sum of the pitch angle and the blade torsion contribution;
calculating an estimated wind speed based on the rotational speed and the adjusted pitch angle, wherein calculating the estimated wind speed comprises:
calculating an estimated power output of the wind turbine for the estimated wind speed;
comparing the estimated power output to a measured power output of the wind turbine; and
determining, based on the comparison, whether to update the estimated wind speed; and
operating the wind turbine based on the estimated wind speed to provide electrical energy to a power grid.

### Claim 2 (depends on 1)

The method according to claim 1, wherein deriving the blade torsion contribution comprises:
using a blade torsion look-up table comprising interrelated values of the rotational speed, the pitch angle, and the blade torsion contribution.

### Claim 3 (depends on 2)

The method according to claim 2, further comprising:
generating the blade torsion look-up table using a model-based simulation.

### Claim 4 (depends on 1)

The method according to claim 1, wherein calculating the estimated wind speed comprises:
using a power coefficient look-up table comprising interrelated values of the rotational speed, a wind speed, the adjusted pitch angle, and a power coefficient.

### Claim 5 (depends on 1)

The method according to claim 1, wherein calculating the estimated wind speed is performed as an iterative process.

### Claim 6

A wind turbine comprising:
a rotor carrying a set of wind turbine blades, wherein each wind turbine blade of the set has a variable pitch angle; and
a controller configured to implement an operation, comprising:
obtaining a rotational speed of the rotor;
obtaining a pitch angle of the wind turbine blades;
deriving a blade torsion contribution based on the rotational speed and the pitch angle;
calculating an adjusted pitch angle as a sum of the pitch angle and the blade torsion contribution;
calculating an estimated wind speed based on the rotational speed and the adjusted pitch angle, wherein calculating the estimated wind sped comprises:
calculating an estimated power output of the wind turbine for the estimated wind speed;
comparing the estimated power output to a measured power output of the wind turbine; and
determining, based on the comparison, whether to update the estimated wind speed; and
operating the wind turbine based on the estimated wind speed to provide electrical energy to a power grid.

### Claim 7

A computer program product comprising computer readable executable code which, when executing on one or more processors, implements an operation, comprising:
obtaining a rotational speed of a rotor of a wind turbine;
obtaining a pitch angle of one or more wind turbine blades attached to the rotor;
deriving a blade torsion contribution based on the rotational speed and the pitch angle;
calculating an adjusted pitch angle as a sum of the pitch angle and the blade torsion contribution;
calculating an estimated wind speed based on the rotational speed and the adjusted pitch angle, wherein calculating the estimated wind speed comprises:
calculating an estimated power output of the wind turbine for the estimated wind speed;
comparing the estimated power output to a measured power output of the wind turbine; and
determining, based on the comparison, whether to update the estimated wind speed; and
operating the wind turbine based on the estimated wind speed to provide electrical energy to a power grid.

### Claim 8 (depends on 1)

The method of claim 1, wherein operating the wind turbine comprises one of:
controlling the pitch angle of the wind turbine blades;
controlling the rotational speed of the rotor; and
controlling a power output of the wind turbine.

### Claim 9 (depends on 1)

The method of claim 1, wherein calculating the estimated power output comprises:
estimating one or more power losses in the wind turbine.

### Claim 10 (depends on 1)

The method of claim 1, wherein calculating the estimated wind speed further comprises:
setting the estimated wind speed responsive to determining that the estimated power output equals the measured power output.

### Claim 11 (depends on 3)

The method of claim 3, wherein the model-based simulation comprises:
obtaining a first pitch angle from a first simulation in which the wind turbine blades are modeled as being completely stiff in a torsion direction; and
obtaining a second pitch angle from a second simulation in which the wind turbine blades are modeled with actual torsional stiffness values,
wherein the blade torsion contribution is based on a difference of the first pitch angle and the second pitch angle.

### Claim 12 (depends on 5)

The method of claim 5, wherein calculating the estimated power output and comparing the estimated power output to the measured power output occurs in a first iteration, the method further comprising:
deriving, in the first iteration, a power coefficient of the wind turbine based on the rotational speed, the adjusted pitch angle, and an estimated wind speed from a previous iteration; and
updating the estimated wind speed responsive to the comparison, wherein the updated estimated wind speed is based on the power coefficient.

### Claim 13 (depends on 5)

The method of claim 5, wherein calculating the estimated power output and comparing the estimated power output to the measured power output occurs in a first iteration, the method further comprising:
updating the estimated wind speed responsive to the comparison; and
performing, using the updated estimated wind speed, a second iteration of calculating the estimated power output and comparing the estimated power output to the measured power output.

### Claim 14 (depends on 13)

The method of claim 13, wherein updating the estimated wind speed comprises:
determining an error signal representing a difference between the estimated power output and the measured power output;
multiplying the error signal by a gain factor; and
integrating the gain factor-multiplied error signal.

### Claim 15 (depends on 6)

The wind turbine of claim 6, wherein operating the wind turbine comprises one of:
controlling the pitch angle of the wind turbine blades;
controlling the rotational speed of the rotor; and
controlling a power output of the wind turbine.

### Claim 16 (depends on 6)

The wind turbine of claim 6, wherein deriving the blade torsion contribution comprises:
using a blade torsion look-up table comprising interrelated values of the rotational speed, the pitch angle, and the blade torsion contribution.

### Claim 17 (depends on 16)

The wind turbine of claim 16, wherein the operation further comprises:
generating the blade torsion look-up table using a model-based simulation.

### Claim 18 (depends on 7)

The computer program product of claim 7, wherein deriving the blade torsion contribution comprises:
using a blade torsion look-up table comprising interrelated values of the rotational speed, the pitch angle, and the blade torsion contribution.

### Claim 19 (depends on 18)

The computer program product of claim 18, wherein the operation further comprises:
generating the blade torsion look-up table using a model-based simulation.