# US 11,994,108 B2 · Multi-rotor wind turbine oscillation damping > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,994,108 B2 - Document ID: US11994108B2 - Status: Granted - Kind: B2 - Application number: 17/258,430 - Filed: 2019-07-03 - Published: 2021-09-02 - Granted: 2024-05-28 - Earliest claimed: 2018-07-06 - Assignees: Vestas Wind Systems A/S - Applicants: Vestas Wind Systems A/S - Inventors: Julio Xavier Vianna Neto; Søren Dalsgaard; Anders Yde Wollesen; Kim Hylling Sørensen - Web page: https://patentgrep.com/patent/US11994108B2 ## CPC - F03D 7/0296: {to prevent, counteract or reduce noise emissions} - F03D 1/02: having a plurality of rotors - F03D 7/0224: {Adjusting blade pitch} - F03D 7/0264: {for stopping; controlling in emergency situations (orientating out of wind F03D7/0208)} - F03D 7/042: {by means of an electrical or electronic controller} - F05B 2240/211: with vertical axis - F05B 2240/37: Multiple rotors - F05B 2260/70: Adjusting of angle of incidence or attack of rotating blades - F05B 2260/964: by damping means - F05B 2270/327: Rotor or generator speeds - 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 A method of damping oscillations in a multi-rotor wind turbine and a wind turbine are provided. The wind turbine comprises a wind turbine support structure and at least a first nacelle with a first rotor and a second nacelle with a second rotor, at least one of the nacelles being located at a position away from a central longitudinal axis of the wind turbine support structure. The method comprises the steps of receiving and processing motion data, selecting a damping algorithm and generating a pitch control signal. The processing comprises determining at least one prominent oscillation mode of the wind turbine support structure and selecting a corresponding damping algorithm. ## Claims ### Claim 1 A method of damping oscillations in a multi-rotor wind turbine, the wind turbine comprising a wind turbine support structure and at least a first nacelle with a first rotor and a second nacelle with a second rotor, at least one of the nacelles being located at a position away from a central longitudinal axis of the wind turbine support structure, the method comprising: receiving motion data representing a movement of the first nacelle and of the second nacelle; processing the received motion data to determine at least two prominent oscillation modes of the wind turbine support structure; for each prominent oscillation mode selecting a corresponding damping algorithm; based on each one of the selected damping algorithms and the received motion data, generate a partial pitch control signal for a pitch controller of at least one of the rotors; combining the generated partial pitch control signals into a combined pitch control signal for the pitch controller of the at least one of the rotors; and based on the combined pitch control signal, instructing the respective pitch controller to adapt a pitch of the at least one of the rotors. ### Claim 2 (depends on 1) The method of claim 1, wherein the motion data further represents a movement of the wind turbine support structure. ### Claim 3 (depends on 1) The method of claim 1, wherein the motion data comprises position data, velocity data and/or acceleration data. ### Claim 4 (depends on 1) The method of claim 1, wherein: at least two rotor arms are attached to the wind turbine support structure, the first nacelle and the second nacelle being carried by the respective rotor arms; the motion data comprises acceleration signals from accelerometers associated with the respective nacelles; one of the at least two prominent oscillation modes is determined to be a tower torsion mode; and the corresponding damping algorithm for the tower torsion mode at least includes subtracting the acceleration signal of the first nacelle from the acceleration signal of the second nacelle. ### Claim 5 (depends on 4) The method of claim 4, wherein one of the prominent oscillation modes is determined to be a tower torsion mode, and one of the prominent oscillation modes is determined to be a tower fore-aft mode, wherein: a first partial pitch control signal for the corresponding damping algorithm for the tower torsion mode at least includes subtracting the acceleration signal of the first nacelle from the acceleration signal of the second nacelle; and a second partial pitch control signal for the corresponding damping algorithm for the tower torsion mode at least includes summing the acceleration signal of the first nacelle from the acceleration signal of the second nacelle. ### Claim 6 (depends on 5) The method of claim 5, wherein the generating of the pitch control signal includes applying a frequency filter based on a frequency window characteristic for the prominent oscillation mode of the respective damping algorithm. ### Claim 7 (depends on 1) The method of claim 1, wherein: at least two rotor arms are attached to the wind turbine support structure, the first nacelle and the second nacelle being carried by the respective rotor arms; the motion data comprises acceleration signals from accelerometers associated with the respective nacelles; one of the at least two prominent oscillation modes is determined to be a tower fore-aft mode; and the corresponding damping algorithm for the tower fore-aft mode at least includes summing the acceleration signal of the first nacelle and the acceleration signal of the second nacelle. ### Claim 8 (depends on 6) The method of claim 6, wherein the frequency filter is applied after the subtraction of the acceleration signals and after the summation of the acceleration signals. ### Claim 9 (depends on 6) The method of claim 6, wherein: a first and a second rotor arm are attached to the wind turbine support structure at a first vertical level, the first nacelle and the second nacelle being carried by the respective rotor arms; a third and a fourth rotor arm are attached to the wind turbine support structure at a second vertical level, a third nacelle with a third rotor and a fourth nacelle with a fourth rotor being carried by the respective rotor arms; and a first prominent oscillation mode is determined to be a first level tower torsion mode, a second prominent oscillation mode is determined to be a second level tower torsion mode, the frequency window characteristic for the first level tower torsion mode being different from the frequency window characteristic for the second level tower torsion mode. ### Claim 10 (depends on 1) The method of claim 1, wherein: at least two rotor arms are attached to the wind turbine support structure, the first nacelle and the second nacelle being carried by the respective rotor arms at substantially equal distances from the longitudinal axis, the motion data is obtained by at least two motion sensors, located along the respective rotor arms, a vibrational mode comprises a torsion mode and/or a fore-aft bending mode of the wind turbine support structure; and determining a vibrational mode level includes combining motion signals from the at least two motion sensors in order to decouple a torsion signal from a fore-aft bending signal. ### Claim 11 (depends on 10) The method of claim 10, wherein each nacelle comprises an oscillation sensor for generating the motion data, and wherein the oscillation sensor is operatively coupled to an oscillation control unit for sending the motion data thereto. ### Claim 12 (depends on 11) The method of claim 11, further comprising a tower oscillation sensor, provided at the wind turbine support structure for generating the motion data based on mechanical oscillations of the wind turbine support structure, and wherein the tower oscillation sensor is operatively coupled to the oscillation control unit for sending the motion data thereto. ### Claim 13 (depends on 1) The method of claim 1, further comprising: for each prominent oscillation mode determining a respective oscillation mode level; comparing the determined oscillation mode levels to respective oscillation mode thresholds; generating a shutdown request for shutting down the nacelles if at least one of the oscillation mode levels exceeds the oscillation mode threshold; and sending the shutdown request to the pitch controllers of the rotors. ### Claim 14 A multi-rotor wind turbine comprising: a wind turbine support structure; a first nacelle with a first rotor and a first pitch controller, operatively coupled to the first rotor for controlling the pitch thereof; a second nacelle with a second rotor and a second pitch controller, operatively coupled to the second rotor for controlling the pitch thereof; at least one of the nacelles being located at a position away from a central longitudinal axis of the wind turbine support structure; and an oscillation control unit, operably coupled to the first and the second pitch controller and being configured to perform an operation of damping oscillations in the multi-rotor wind turbine, the operation comprising: receiving motion data representing a movement of the first nacelle and of the second nacelle; processing the received motion data to determine at least two prominent oscillation modes of the wind turbine support structure; for each prominent oscillation mode selecting a corresponding damping algorithm; based on each one of the selected damping algorithm and the received motion data, generating a partial pitch control signal for a pitch controller of at least one of the rotors; combining the generated partial pitch control signals into a combined pitch control signal for the pitch controller of the at least one of the rotors; and based on the combined pitch control signal instructing the respective pitch controller to adapt a pitch of the at least one of the rotors. ### Claim 15 (depends on 14) The multi-rotor wind turbine claim 14, wherein the motion data further represents a movement of the wind turbine support structure. ### Claim 16 (depends on 14) The multi-rotor wind turbine of claim 14, wherein the motion data comprises position data, velocity data and/or acceleration data. ### Claim 17 (depends on 14) The multi-rotor wind turbine of claim 14, wherein: at least two rotor arms are attached to the wind turbine support structure, the first nacelle and the second nacelle being carried by the respective rotor arms; the motion data comprises acceleration signals from accelerometers associated with the respective nacelles; one of the at least two prominent oscillation modes is determined to be a tower torsion mode; and the corresponding damping algorithm for the tower torsion mode at least includes subtracting the acceleration signal of the first nacelle from the acceleration signal of the second nacelle. ### Claim 18 (depends on 14) The multi-rotor wind turbine of claim 14, wherein: at least two rotor arms are attached to the wind turbine support structure, the first nacelle and the second nacelle being carried by the respective rotor arms; the motion data comprises acceleration signals from accelerometers associated with the respective nacelles; one of the at least two prominent oscillation modes is determined to be a tower fore-aft mode; and the corresponding damping algorithm for the tower fore-aft mode at least includes summing the acceleration signal of the first nacelle and the acceleration signal of the second nacelle. ### Claim 19 (depends on 18) The multi-rotor wind turbine of claim 18, wherein one of the prominent oscillation modes is determined to be a tower torsion mode, and one of the prominent oscillation modes is determined to be a tower fore-aft mode, wherein: a first partial pitch control signal for the corresponding damping algorithm for the tower torsion mode at least includes subtracting the acceleration signal of the first nacelle from the acceleration signal of the second nacelle; and a second partial pitch control signal for the corresponding damping algorithm for the tower torsion mode at least includes summing the acceleration signal of the first nacelle from the acceleration signal of the second nacelle.