# US 11,306,699 B2 · Method for load reduction on wind turbine blade pitch bearings > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,306,699 B2 - Document ID: US11306699B2 - Status: Granted - Kind: B2 - Application number: 16/487,315 - Filed: 2017-11-27 - Published: 2020-02-20 - Granted: 2022-04-19 - Earliest claimed: 2017-02-22 - Assignees: Siemens Gamesa Renewable Energy A/S - Applicants: Siemens Gamesa Renewable Energy A/S - Inventors: Julian Ehlers; Michael Hind; Drew Eisenberg; Alejandro Gomez Gonzalez; Peder Bay Enevoldsen; Lasse Gilling - Web page: https://patentgrep.com/patent/US11306699B2 ## CPC - F03D 7/0224: {Adjusting blade pitch} - F03D 7/024: {of individual blades} - F03D 7/0292: {to reduce fatigue} - F03D 80/70: Bearing or lubricating arrangements - F05B 2260/79: Bearing, support or actuation arrangements therefor - F05B 2270/309: Rate of change of parameters - F05B 2270/326: Rotor angle - 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 Provided is a method for adjusting a pitch angle of a rotor blade connected to a rotor of a wind turbine, the method includes: pitching the rotor blade towards a target blade pitch angle, the manner of pitching depending on a load on a pitch bearing and/or an azimuthal position of the rotor. ## Claims ### Claim 1 A method for adjusting a pitch angle of a rotor blade connected to a rotor of a wind turbine, the method comprising: pitching the rotor blade towards a target blade pitch angle with a pitch rotational speed that depends on a load on a pitch bearing, wherein the pitch rotational speed is adjusted to be lower in a range of azimuthal positions in which the load on the pitch bearing due to aerodynamics and due to gravitation is larger than for other azimuthal positions. ### Claim 2 (depends on 1) The method according to claim 1, wherein the pitching the rotor blade comprises: decreasing a pitch rate of the rotor blade in a range of azimuthal positions of the rotor, where the load on the rotor blade pitch bearing or a bending moment of the rotor blade is above a threshold; and increasing the pitch rate of the rotor blade in another range of azimuthal positions of the rotor, where the load on the rotor blade pitch bearing or the bending moment of the rotor blade is at or below the threshold. ### Claim 3 (depends on 1) The method according to claim 1, wherein the pitch rotational speed further depends on the azimuthal position of the rotor. ### Claim 4 (depends on 3) The method according to claim 3, wherein the pitch rotational speed depends on the azimuthal position according to a predefined curve (and/or wherein the pitch rotational speed is the smaller the greater the load on the pitch bearing is. ### Claim 5 (depends on 3) The method according to claim 3, wherein the pitch rotational speed depends on the azimuthal position, if the pitch bearing load indicating quantity indicates that the load of the pitch bearing exceeds a threshold, wherein the pitch bearing load indicating quantity is estimated and/or measured and/or calculated from at least one operational parameter of the wind turbine or the environment. ### Claim 6 (depends on 5) The method according to claim 5, wherein the pitch rotational speed is lower for azimuthal positions where the rotor blade performs a downswing than for azimuthal positions where the rotor blade performs an upswing. ### Claim 7 (depends on 1) The method according to claim 1, wherein the pitch rotational speed: has a first value, when the target pitch angle is adjusted from an initial pitch angle to the target pitch angle in a direction towards stall, and has a second value, when the target pitch angle is adjusted from the initial pitch angle to the target pitch angle in a direction away from stall, wherein the first value is different from the second value. ### Claim 8 (depends on 1) The method according to claim 1, wherein the pitching of the rotor blade comprises: pitching the rotor blade depending on a measured blade root moment and/or pitch bearing load indicating quantity. ### Claim 9 (depends on 1) The method according to claim 1, wherein the pitching the rotor blade comprises: pitching the rotor blade further depending on pitch bearing load accumulated over time. ### Claim 10 (depends on 1) The method according to claim 1, wherein the azimuthal position is defined in degrees relative to a vertically oriented longitudinal axis of the rotor blade, while a tip of the rotor blade is pointing upwards, wherein the pitch rotational speed has a first average value in an azimuthal position range between 110 and 350°, wherein the pitch rotational speed has a second average value in an azimuthal position range between 350 and 110° wherein the first average value is between two times and 100 times as great as the second average value. ### Claim 11 (depends on 1) The method according to claim 1, wherein pitch rotational speed depends on the load on the pitch bearing, if: the load level of the pitch bearing exceeds a threshold, and/or a wind turbulence level is greater than threshold, and/or a deviation of drive train rotational speed from a reference exceeds a threshold and/or a wind speed is greater than a threshold. ### Claim 12 (depends on 1) The method according to claim 1, wherein the pitch rotational speed depends on the average load of each blade's pitch bearing, wherein a rate of pitch change is a function of each blade's bearing load compared to the average bearing load on all blades; and/or wherein the pitch rotational speed depends on a torsional strain on the rotor blade and/or on the pitch bearing. ### Claim 13 A method for adjusting pitch angles of a first rotor blade and a second rotor blade both connected to a rotor of a wind turbine, the method comprising: pitching the first rotor blade with a first pitch rotational speed that depends on a first load on a first pitch bearing, wherein the first pitch rotational speed is adjusted to be lower in a range of azimuthal positions for the first rotor blade in which the load on the first pitch bearing due to aerodynamics and due to gravitation is larger than for other azimuthal positions of the first rotor blade, and pitching the second rotor blade with a second pitch rotational speed that depends on a second load on a second pitch bearing, wherein the second pitch rotational speed is adjusted to be lower in a range of azimuthal positions for the second rotor blade in which the load on the second pitch bearing due to aerodynamics and due to gravitation is larger than for other azimuthal positions of the second rotor blade, wherein pitching the first rotor blade is independent of pitching the second rotor blade. ### Claim 14 An arrangement for adjusting a pitch angle of a rotor blade connected to a rotor of a wind turbine, the arrangement comprising: a pitching system configured to pitch the rotor blade towards a target blade pitch angle with a pitch rotational speed that depends on a load on a pitch bearing, wherein the pitch rotational speed is adjusted to be lower in a range of azimuthal positions in which the load on the pitch bearing due to aerodynamics and due to gravitation is larger than for other azimuthal positions. ### Claim 15 (depends on 14) A wind turbine, comprising: a rotor; at least one rotor blade connected to the rotor; and the arrangement according to claim 14.