Embodiments herein describe in-plane vibration damping techniques for MR turbines. The MR turbines can include arms that extend from a common tower and support multiple rotors. Because the rotors are disposed laterally away from the tower, side-to-side motion of the tower causes the rotors to have an angled trajectory that includes both lateral and vertical displacement. In addition, a rotor disposed on one side of the tower in MR turbine can have a very different trajectory than a rotor disposed on the opposite side of the tower. To account for the vertical displacement and the different trajectories, in one embodiment, a controller can use different phase offsets for each rotor when calculating pitch offsets for performing in-plane vibration damping. In another embodiment, the controller can use both the lateral and vertical accelerations of the rotors to identify the pitch offsets for the rotors to perform in-plane vibration damping.

The invention relates to a sensor arrangement for use on a wind turbine. The sensor arrangement comprises a rotor blade-related sensor, which is arranged in/on a rotor blade, and a non-rotor blade-related sensor, wherein the sensor signals, which are associated with the rotor blade-related sensor, are processed by fusion with the sensor signals which are associated with the non-rotor blade-related sensor. The invention also relates to a method for operating a wind turbine.

A method for wind turbine tower damping is disclosed, as well as an associated controller and wind turbine. The method comprises determining, using one or more sensor signals, dynamic state information for a tower of a wind turbine during power production, wherein the dynamic state information comprises a tower frequency. The method further comprises determining at least one control loop gain value using the tower frequency, and generating, using the at least one control loop gain value, one or more control signals for controlling a rotational speed of a rotor of the wind turbine.

Provided is a system for determining an amount of oscillating movement of a wind turbine, the wind turbine including a tower, a non-rotating upper part supported by the tower, a rotor having a rotor axis, and a generator for generating electric power. The system includes (a) a sensor unit adapted to provide a rotor speed signal indicative of a rotational speed of the rotor relative to the non-rotating upper part, (b) a filtering unit adapted to, based on the rotor speed signal provided by the sensor unit, provide a filtered signal including information associated with an oscillating movement of the wind turbine, and (c) a processing unit adapted to determine the amount of oscillating movement based on the filtered signal provided by the filtering unit. Furthermore, a wind turbine and a method are described.

A first vibration sensor measures vibration of a bearing. A second vibration sensor for measuring background noise received by the first vibration sensor is installed so as not to receive vibration of the bearing. A data acquisition device receives a first signal that is a measurement signal of the first vibration sensor and a second signal that is a measurement signal of the second vibration sensor and outputs a third signal obtained by subtracting the second signal from the first signal as data indicating vibration of the bearing.

A method of monitoring a blade pitch bearing of a rotor blade of a wind turbine is provided, the method including: pitching the rotor blade; measuring an amount of a vibration of the blade pitch bearing during the pitching; estimating a condition of the blade pitch bearing based on the measured amount of vibration. Also disclosed is an arrangement for monitoring a blade pitch bearing, a rotor blade bearing and a wind turbine.

The present disclosure is directed to a system for monitoring wear on a gearbox of a wind turbine. A controller of the system is configured to determine a torque exerted on a rotor shaft of the wind turbine or a generator shaft of the wind turbine based on measurement signals received from a first sensor of the system. The controller is also configured to determine an accumulated wear value for the gearbox based on the torque.

The present invention relates to a control method and a wind turbine configured to determine a load signal of at least one component of the wind turbine, and to calculate a damage rate based on this load signal. The control method calculates and monitors the damage rate in real-time, wherein the damage rate is normalised by using a first function defining a first transition phase. A second function is afterwards applied to the normalised damage rate which defines a second transition phase. These transition phases allows for a smooth transition between different operating modes of the wind turbine. The control method may further change the power output of the wind turbine relative to the nominal power output when the output signal of the second function is determined to be stable over at least one time period.

A method for mitigating damage in a rotor blade of a plurality of rotor blades of a wind turbine includes receiving a plurality of acceleration signals from the plurality of the rotor blades in at least one direction. The method also includes generating a spectral density for each of the plurality of acceleration signals. Further, the method includes determining blade energies for each of the plurality of rotor blades based on the spectral densities for each of the plurality of acceleration signals for at least one predetermined frequency range. Moreover, the method includes comparing the blade energies to at least one of each other or a predetermined damage threshold. In addition, the method includes implementing a control action when one or more of the blade energies vary from each other by a predetermined amount or one or more of the blade energies exceed the predetermined damage threshold.

The invention relates to a method for estimating a clearance (7) between a tower (2) and foundations (6) of a wind turbine (1), comprising the following steps: S1: acquiring N maximum accelerations of the tower (2) of the wind turbine (1); S2: associating a predefined interval of accelerations with each maximum acceleration; S3: determining the number of occurrences of each interval of accelerations over the N time intervals; S4: deducing therefrom a mode for the N time intervals; S5: repeating steps S1 to S4 multiple times so as to obtain multiple modes; S6: comparing the modes obtained in this manner and deducing therefrom a change in the clearance (7).