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.

Provided is a method for controlling an electric generator of a wind turbine. The method includes varying an amplitude and/or phase angle of an harmonic current of said electric generator, while said electric generator is rotating, in particular at a known condition, measuring a signal indicative of generator vibration after and/or during varying said amplitude and/or phase angle, repeating said varying and said measuring until a predetermined requirement is met, evaluating an operating point for said electric generator by using said measured signals indicative of generator vibration in order to reduce a ripple torque of said generator, and controlling a current, in particular said harmonic current, of said electric generator in order to meet said operating point.

A method for operating a wind turbine, an associated wind turbine, and an associated wind park are provided. The wind turbine has a tower with tower loads acting thereon and an aerodynamic rotor which generates a rotor thrust. The method has a step of reducing the rotor thrust. The reduction of the rotor thrust is performed while considering the effect of the reduction of the rotor thrust on the tower loads. Thus, the reduction of the rotor thrust is avoided in cases which result in undesirable or even counter-productive effects on the tower loads.

An automated method to determine modal characteristics of a wind turbine tower at an offshore location in a continuous manner includes reading one or more sensor data signals, prefiltering the one or more sensor data signals to divide the signals into a plurality of time segments, obtaining a frequency domain representation of each of the plurality of time segments by computing a Power Spectral Density (PSD) of each of the time segments to identify one or more frequency peaks in each of the time segments, assigning a probability to each of the frequency peaks in the PSD of each of the time segments, combining all assigned probabilities and determining the likelihood of the one or more frequency peaks. Also disclosed is an offshore wind turbine tower having a turbine control system utilizing the automated method to determine modal characteristics of the wind turbine.

A method of determining a frequency of an oscillating movement of a wind turbine tower is provided, the wind turbine tower carrying 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. Also provided is a device for determining a frequency of an oscillating movement.

The present invention provides a method of operating a wind turbine. The wind turbine comprises at least one rotatable blade. The method comprises the steps of providing a load sensor configured to generate a load signal representing loading on the blade, generating a first load signal when the blade is in a first position, and generating a second load signal when the blade is in a second position. Additionally, the method comprises steps of detecting a rotational speed of the blade, calculating a weight force on the blade based on the first and the second load signal, and calculating a centrifugal force on the blade based on the first and the second load signal. Subsequently, the weight force is compared with a predetermined weight force, and the centrifugal force is compared with a predetermined centrifugal force at the detected rotational speed. Finally, a risk of ice throw is determined based on the comparisons of the weight force and the centrifugal force with the predetermined forces.

Disclosed herein is a vibration monitoring and diagnosing system for monitoring conditions of a wind power generator and diagnosing a defective portion thereof using vibration characteristics obtained from acceleration sensors mounted to the wind power generator. A vibration-based defect detecting method may include: collecting vibration data of the wind power generator using the plurality of sensors; extracting a first characteristic value of a time domain based on the vibration data; extracting characteristic values in one or more frequency bands for a location of each sensor in a frequency domain or an envelope frequency domain if the first characteristic value is greater than a preset alarm setting value; and determining that a defect is present when at least one characteristic value of the characteristic values is greater than a preset normal value.

The present invention relates to a method and wind turbine for determining a dynamic twist of one or more blades. One or more first signals are received from a first wireless sensor attached to a blade of a wind turbine and a first angle is determined based on the received first signals. One or more second signals are received from a second wireless sensor attached to a blade of a wind turbine and spaced apart from the first wireless sensor by a predetermined distance. A second angle is determined based on the received second signals. A dynamic twist of the blade is determined based on the determined first angle, the determined second angle and the predetermined distance.

A method of determining the shape of at least part of a wind turbine blade during operation of the wind turbine, the method comprising measuring first and second values of acceleration at one or more locations on the blade, the first and second values of acceleration being in substantially mutually perpendicular directions, and determining a shape parameter of the blade based upon the relative magnitudes of the measured first and second values of acceleration at the one or more locations.

A method for monitoring a wind turbine is described. The method comprises measuring acceleration by means of a fiber-optic acceleration sensor in a rotor blade of the wind turbine; opto-electronically converting an acceleration signal of the fiber-optic acceleration sensor; and filtering the opto-electronically converted acceleration signal by means of an analog anti-aliasing filter.