# US 12,180,930 B2 · Determining a frequency of an oscillating movement of a wind turbine tower > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,180,930 B2 - Document ID: US12180930B2 - Status: Granted - Kind: B2 - Application number: 17/800,015 - Filed: 2021-01-21 - Published: 2023-03-09 - Granted: 2024-12-31 - Earliest claimed: 2020-02-25 - Assignees: Siemens Gamesa Renewable Energy A/S - Applicants: Siemens Gamesa Renewable Energy A/S - Inventors: Henrik Steffensen; Carl Lund Richter - Web page: https://patentgrep.com/patent/US12180930B2 ## CPC - F03D 17/00: Monitoring or testing of wind motors, e.g. diagnostics (testing during commissioning of wind motors F03D13/30) - F03D 7/0296: {to prevent, counteract or reduce noise emissions} - F05B 2270/327: Rotor or generator speeds - F05B 2270/334: Vibration measurements - F05B 2270/807: Accelerometers - 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 determining a frequency of an oscillating movement of a wind turbine tower. The wind turbine tower includes a nacelle and a generator including a stator and a rotor, the oscillating movement causing a rolling movement of the nacelle, the method including obtaining a first signal indicative of rotor speed relative to the nacelle, obtaining a second signal indicative of rotor speed relative to ground, determining a first amplitude spectrum based on the first signal, determining a second amplitude spectrum based on the second signal, determining a difference function based on the first amplitude spectrum and the second amplitude spectrum, and determining the frequency of the oscillating movement of the wind turbine tower as a frequency corresponding to a peak in the difference function. A device for determining a frequency of an oscillating movement. ## Claims ### Claim 1 A method of operating a wind turbine having a wind turbine tower, the wind turbine tower carrying a nacelle and a generator including a stator and a rotor, the method comprising: determining a frequency of an oscillating movement of the wind turbine tower, the oscillating movement causing a rolling movement of the nacelle, wherein the frequency is determined by: obtaining a first signal indicative of a speed of the rotor relative to the nacelle; obtaining a second signal indicative of the speed of the rotor relative to ground; determining a first amplitude spectrum based on the first signal; determining a second amplitude spectrum based on the second signal; determining a difference function based on the first amplitude spectrum and the second amplitude spectrum, and determining the frequency of the oscillating movement of the wind turbine tower as a frequency corresponding to a peak in the difference function; and controlling the wind turbine according to the frequency of the oscillating movement of the wind turbine tower. ### Claim 2 (depends on 1) The method according to claim 1, wherein the oscillating movement of the wind turbine tower is a second mode tower oscillating movement. ### Claim 3 (depends on 1) The method according to claim 1, wherein the difference function is determined as an absolute difference between the first amplitude spectrum and the second amplitude spectrum as a function of frequency. ### Claim 4 (depends on 1) The method according to claim 1, further comprising applying a smoothing to each of the first amplitude spectrum and the second amplitude spectrum before determining the difference function. ### Claim 5 (depends on 1) The method according to claim 1, wherein the first signal is obtained by a rotor speed sensor arranged within the nacelle and configured to measure the speed of the rotor. ### Claim 6 (depends on 5) The method according to claim 5, wherein the rotor speed sensor is an optical or a magnetic sensor configured to detect when a corresponding part of the rotor passes by the first sensor. ### Claim 7 (depends on 1) The method according to claim 1, wherein the second signal is obtained by a monitoring device arranged at a hub of the wind turbine. ### Claim 8 (depends on 7) The method according to claim 7, wherein the monitoring device comprises at least one inertial sensor. ### Claim 9 (depends on 8) The method according to claim 8, wherein the at least one inertial sensor comprises a g-sensor and/or a gyroscope. ### Claim 10 (depends on 1) The method according to claim 1, wherein determining the first amplitude spectrum and determining the second amplitude spectrum comprises applying a sliding discrete Fourier transform to the first signal and the second signal, respectively. ### Claim 11 (depends on 1) The method according to claim 1, further comprising confirming the determined frequency as the frequency of the oscillating movement of the wind turbine tower if the peak value of the difference function exceeds a predetermined threshold value. ### Claim 12 A controller of a wind turbine having a wind turbine tower, the wind turbine tower carrying a nacelle and a generator including a stator and a rotor, the controller comprising: an interface configured to: receive a first signal indicative of a speed of the rotor relative to the nacelle, and receive a second signal indicative of the speed of the rotor relative to ground, and a processing unit configured to: determine a first amplitude spectrum based on the first signal, determine a second amplitude spectrum based on the second signal, determine a difference function based on the first amplitude spectrum and the second amplitude spectrum, determine a frequency of an oscillating movement of the wind turbine tower as a frequency corresponding to a peak in the difference function, and control the wind turbine according to the frequency of the oscillating movement of the wind turbine tower. ### Claim 13 (depends on 12) A wind turbine comprising a device according to claim 12. ### Claim 14 (depends on 1) A computer program product comprising a non-transitory computer readable medium comprising computer executable instructions, which, when executed by a processor, are configured to perform the steps of the method according to claim 1.