System and method for mitigating vibrations on a wind turbine in a non-operational state

Abstract

The present invention relates to systems and methods for mitigating vibrations on a wind turbine in a non-operational state. In particular, presently disclosed is a method for mitigating vibrations in one or more rotor blades of a wind turbine when the wind turbine is in a non-operational state. The method includes receiving a vibration signal indicative of vibrations occurring or potentially occurring on the one or more rotor blades. The method also includes determining that the vibration signal is above a vibration threshold. Further, the method includes continuously pitching the one or more rotor blades back and forth across a range of pitch angles for a particular period of time in order to mitigate the vibrations.

Description

Technical Field

[0001] This disclosure generally relates to wind turbine power generation systems, and more specifically to systems and methods for mitigating vibrations in wind turbines by continuously adjusting the pitch of one or more of their rotor blades, particularly when the wind turbine is in a non-operating state. Background Technology

[0002] Modern wind turbines are commonly used to supply electricity to the power grid. This type of wind turbine generally consists of a tower and a rotor mounted on the tower. The rotor, typically comprising a hub and multiple blades, rotates under the action of wind on the blades. This rotation generates torque, which is transmitted directly (“directly driven”) through the rotor shaft or via a gearbox to a generator. The generator then produces electricity that can be supplied to the power grid.

[0003] There is a trend toward making wind turbine blades longer to capture more wind and convert its energy into electricity. This results in blades that are more flexible and more prone to aeroelastic instabilities, such as blade vibration. Blade vibration poses a significant risk of potential damage throughout the wind turbine.

[0004] When a wind turbine is operating, the turbine controller can operate auxiliary systems, such as pitch or yaw systems, to reduce loads on the blades. This can counteract blade vibrations. However, aeroelastic instability issues can also be severe when the wind turbine is not operating, such as when it is idling or locked.

[0005] At least two types of vibration can occur during non-operational periods. The first type is vortex-induced vibration (VIV), which occurs when the angle of attack is approximately 90 degrees and the vortex breaks off at a frequency close to the blade's natural (eigen) frequency. The second type is stall-induced vibration (SIV), which occurs when the angle of attack approaches the stall angle (e.g., 15–20 degrees or other ranges, depending on the wind turbine design) and the flow interactions can cause blade vibration. The angle of attack can be understood as the geometric angle between the direction of wind flow and the chord line of the rotor blades. VIV and SIV are phenomena that can lead to blade failure or accelerated blade damage if not adequately designed or compensated for.

[0006] When the rotor is locked to prevent rotation (e.g., due to installation, commissioning, or maintenance tasks), the rotor blades may experience aeroelastic instabilities such as VIV and SIV. The rotor blades are susceptible to these vibrations when the angle of attack is within a certain range. Because the rotor is locked, its rotation cannot be used to reduce or suppress these vibrations. Furthermore, excessive loads can be applied to wind turbine components by changing the blade pitch of a locked rotor. For example, some pitch angles may be acceptable to suppress non-operational aeroelastic instabilities (such as SIV and VIV), but may result in unacceptable loads on certain wind turbine components. Therefore, some wind turbines employ aerodynamic devices attached to the rotor blades to reduce vortices and / or increase damping. However, these devices can increase the cost and time required for installation and removal.

[0007] U.S. Patent Publication No. 2020 / 0173418 discloses a method for reducing vibration in the rotor blades of a wind turbine when the turbine is in a stopped or locked state. This method requires the use of sensors to first measure one or more deformation parameters indicating vibration or oscillation (collectively referred to herein as vibration) induced in the rotor blades. The method uses a dedicated controller that communicates with the sensors to determine the presence of vibration based on the measured deformation parameters. This dedicated controller also communicates with an auxiliary pitch drive system and generates an output signal to operate the auxiliary pitch drive system to change the blade pitch between 0 and 90 degrees to reduce vibration. However, the method and system disclosed in '418 do not consider the loads that may be applied to the wind turbine components by changing the blade pitch of the locked rotor. Some pitch angles may be acceptable to suppress aeroelastic instabilities (e.g., SIV and VIV), but may result in unacceptable loads on some wind turbine components.

[0008] In view of the above-mentioned circumstances, this disclosure is directed to systems and methods for mitigating vibrations in wind turbines by continuously adjusting the pitch of one or more of its rotor blades, particularly when the wind turbine is in a non-operating state. Summary of the Invention

[0009] Aspects and advantages of the invention will be set forth in part in the description which follows, or will be apparent from the description, or may be learned by practice of the invention.

[0010] In one aspect, this disclosure relates to a method for mitigating vibrations that occur or potentially occur on one or more rotor blades of a wind turbine when the turbine is in an inoperable state. The method includes receiving, via a controller, a vibration signal indicating vibrations occurring or potentially occurring on one or more rotor blades. The method also includes comparing the vibration signal with a vibration threshold via the controller. In response to a vibration signal exceeding the vibration threshold, the method includes continuously adjusting the pitch of one or more rotor blades back and forth across a pitch angle range for a specific time period to mitigate the vibration.

[0011] On the other hand, this disclosure relates to a wind turbine having a plurality of rotor blades on a rotatable hub. The wind turbine also includes one or more sensors configured to detect wind parameters affecting the plurality of rotor blades; a pitch system configured to change the pitch angle of one or more of the plurality of rotor blades; and a controller operatively in communication with the pitch system. When the wind turbine is in a non-operating or locked rotor state, the controller is configured to perform a plurality of operations, including, but not limited to, receiving a vibration signal indicating vibration occurring or potentially occurring on one or more of the plurality of rotor blades, comparing the vibration signal with a vibration threshold via the controller, and, in response to a vibration signal exceeding the vibration threshold, continuously adjusting the pitch of one or more of the plurality of rotor blades back and forth across a pitch angle range for a specific period of time to mitigate vibration.

[0012] These and other features, aspects, and advantages of the invention will become more readily understood with reference to the following description and the appended claims. Embodiments of the invention are illustrated in the accompanying drawings, which are incorporated in and form a part of this specification, and together with the description serve to explain the principles of the invention. Attached Figure Description

[0013] The complete and practical disclosure of the invention, including its preferred mode, is set forth in the description with reference to the accompanying drawings, for those skilled in the art, wherein: Figure 1 A perspective view of an embodiment of a wind turbine according to the present disclosure is shown; Figure 2 A simplified interior view of the nacelle of a wind turbine according to this disclosure is shown; Figure 3 The diagram shows multiple rotor blades of a wind turbine according to the present disclosure, on which sensors are mounted. Figure 4 A block diagram illustrating an embodiment of a controller for a wind turbine according to the present disclosure is shown; and Figure 5 A flowchart illustrating an embodiment of a method for mitigating vibrations in the rotor blades of a wind turbine according to the present disclosure is shown.

[0014] Reference characters are used repeatedly in this specification and drawings to indicate the same or similar features or elements of the invention. Detailed Implementation

[0015] Reference will now be made in detail to embodiments of the invention, one or more of which are illustrated in the accompanying drawings. Each example is provided to explain the invention rather than to limit it. Indeed, it will be apparent to those skilled in the art that various modifications and variations may be made to the invention without departing from its scope or spirit. For example, features shown or described as part of one embodiment may be used in conjunction with another embodiment to produce further embodiments. Therefore, the invention is intended to cover such modifications and variations as those falling within the scope of the appended claims and their equivalents.

[0016] Generally, this disclosure relates to a method for preventing or reducing vibration by continuously adjusting the pitch angle of one or more wind turbine blades back and forth across a specified range for a specified period of time. By continuously changing the pitch angle, the currently disclosed method reduces or prevents aerodynamic instabilities on the wind turbine blades.

[0017] Now refer to the attached diagram, Figure 1 A perspective view of an embodiment of a wind turbine 160 is shown. As shown, the wind turbine 160 includes a tower 170 extending from a support surface 150, a nacelle 161 mounted on the tower 170, and a rotor 115 coupled to the nacelle 161. The rotor 115 includes a rotatable hub 110 and at least one rotor blade 120 coupled to and extending outward from the hub 110. For example, in the example shown, the rotor 115 includes three rotor blades 120. However, in alternative embodiments, the rotor 115 may include more or fewer than three rotor blades 120. Each rotor blade 120 is spaced apart from the hub 110 to facilitate rotation of the rotor 115 to enable kinetic energy to be converted from wind into usable mechanical energy, and subsequently into electrical energy. For example, the hub 110 may be rotatably coupled to a generator 162 (…). Figure 2 The generator 162 is located within or forms part of the nacelle 161 to generate electricity. The wind turbine 160 can be placed at sea or on land.

[0018] Additionally, as shown, the wind turbine 160 includes a controller 200, which may be centrally located inside or outside the nacelle 161. However, in other examples, the controller 200 may be located within or outside any other component of the wind turbine 160. Furthermore, the controller 200 may be communicatively coupled to any number of components of the wind turbine 160 to control the operation of such components.

[0019] For example, controller 200 may be communicatively coupled to one or more auxiliary systems, such as pitch drive system 107 for adjusting the pitch angle of rotor blades 120. Figure 2 Alternatively, the controller 200 may include a yaw drive system 180 for rotating the nacelle 161 relative to the tower 170 about an axis of rotation. Figure 2 ).

[0020] Still referencing Figure 1 The wind turbine 160 may also include a dedicated power source 140. Thus, in embodiments where the wind turbine 160 neither generates nor receives electrical power from the grid, the dedicated power source 140 may include a battery or supercapacitor (not shown) that stores a predetermined amount of energy to supply the controller 200 (or a dedicated controller) and one or more auxiliary systems described herein for a predetermined period of time. In an alternative example, the dedicated power source 140 may include a fuel generator, such as a diesel generator.

[0021] Now for reference Figure 2 This shows the following according to the present disclosure Figure 1 A simplified internal view of an embodiment of the nacelle 161 of the wind turbine 160. As shown, a generator 162 may be disposed within the nacelle 161 and coupled to a rotor 115 for generating electrical power from the rotational energy generated by the rotor 115. For example, the rotor 115 may include a main rotor shaft 163 coupled to a hub 110 for rotation therewith. The generator 162 may then be coupled to the rotor shaft 163 such that rotation of the rotor shaft 163 drives the generator 162. Additionally, as shown, the generator 162 may include a generator shaft 166 rotatably coupled to the rotor shaft 163 via an optional gearbox 164.

[0022] It should be recognized that the rotor shaft 163, gearbox 164 and generator 162 can be substantially supported within the nacelle 161 by a support frame or platform 165 positioned on top of the tower 170.

[0023] The nacelle 161 is rotatably connected to the tower 170 via a yaw drive system 180 in this manner, allowing the nacelle 161 to rotate about the rotation axis RA or the yaw axis YA, as shown below. Figure 2 As shown in the figure, the yaw drive system 180 includes a yaw bearing 181. Additionally, as shown, the yaw drive system 180 may generally include a plurality of yaw drives 182, each yaw drive 182 having a yaw motor 183, a yaw gearbox 184, and a yaw drive pinion 185 for engaging with the yaw bearing 181 to rotate the yaw bearing 181 about the yaw axis YA.

[0024] In addition, and still refer to Figure 2Each of the rotor blades 120 (only one shown) can be coupled to the hub 110 via a pitch drive system 107. In an embodiment, for example, the pitch drive system 107 may include a pitch bearing 100 between each rotor blade 120 and the hub 110. Additionally, as shown, the pitch drive system 107 may generally include at least one pitch drive pinion 108, a pitch drive motor 105, and a pitch drive gearbox 106. Thus, the pitch drive motor 105 drives the rotation of the pitch drive gearbox 106, and therefore drives the pitch drive pinion 108 to engage the pitch bearing 100, thereby causing the rotor blade 120 to rotate about the pitch axis PA. Therefore, when the pitch drive system 107 is actuated, the rotor blade 120 can perform a relative rotational movement relative to the hub 110. This rotational movement is performed about the pitch axis PA and can therefore be measured in degrees.

[0025] refer to Figure 1 and Figure 2 The wind turbine 160 may also include one or more wind parameter sensors 125, 126, 127, 128 for measuring various wind and / or operating parameters of the wind turbine 160. For example, such as Figure 2 As shown, sensors 125, 126, 127, and 128 can be positioned at any suitable location, such as on hub 110, on tower 170, on nacelle 161, on one or more rotor blades 120, etc. Wind parameters can be any one or a combination of the following: gusts, wind speed, wind direction, wind acceleration, wind turbulence, wind shear, wind direction change, wake, updraft, etc. Further, as an example, operating parameters may include rotor speed, generator speed, power output, torque, load, etc.

[0026] Furthermore, in embodiments, sensors 125, 126, 127, and 128 may include any other suitable sensors, such as light detection and ranging (LIDAR) sensors, accelerometers, proximity sensors, pressure sensors, angle-of-attack sensors, vibration sensors, miniature inertial measurement units (MIMUs), camera systems, fiber optic systems, anemometers, wind vanes, sounding and ranging (SODAR) sensors, infrared lasers, radiometers, pitot tubes, radiosondes, other optical sensors, and / or any other suitable sensors. It should be appreciated that, as used herein with respect to sensors 125, 126, 127, and 128, the term "determine" and its variations indicate that various sensors for wind turbines can be configured to provide direct or indirect measurements of the monitored parameter. Therefore, sensors 125, 126, 127, and 128 can, for example, be used to generate signals associated with the monitored parameter, which can then be used by controller 200 to determine the actual wind conditions.

[0027] Now for reference Figure 3 This illustration shows an arrangement of a plurality of rotor blades 120 of a wind turbine 160 according to the present disclosure, on which load sensors 121 are mounted. In such embodiments, the load sensors 121 can be used to measure the deformation of one or more of the rotor blades 120. Furthermore, in embodiments, the load sensors 121 may be strain sensors that detect the deformation / strain parameters of the rotor blades 120. For example, as shown, Figure 3 The load sensor 121 shown corresponds to a fiber optic strain gauge mounted on each rotor blade 120 to measure strain at any part of the rotor blade 120 (e.g., the blade root 34).

[0028] Furthermore, as shown, load sensors 121 can be connected to each other via optical path 122 (e.g., optical fiber). Optical path 122 also allows load sensors 121 to communicate with sensor interrogation unit 124 or readout unit located in hub 110 or nacelle 161. Sensor interrogation unit 124 is configured to feed emitted light pulses (not shown) to optical path 122 and receive light pulses from load sensors 121. Sensor interrogation unit 124 is further configured to compare the emitted light pulses and the received light pulses to determine deflection in rotor blade 120. The number and location of load sensors 121 in rotor blade 120 (or other components) may vary depending on specific requirements.

[0029] More specifically, vibration of one or more of the rotor blades 120 can be determined when the strain or deformation parameters meet a strain or deformation threshold, which can be determined by the controller 200. In an embodiment, the controller 200 may include or be integrated with a sensor interrogation unit 124. Alternatively, the sensor interrogation unit 124 may be separate from the controller 200 and communicate data with it.

[0030] In some embodiments, the load sensor 121 may be provided with a temperature sensor. Temperature data from the temperature sensor may be considered by the sensor interrogation unit 124 or even by the controller 200, as temperature may affect the operation and characteristics of the load sensor 121.

[0031] Alternatively, for the example of an optical strain gauge, other types of load sensors 121 capable of indicating deformation of one or more of the rotor blades 120 or other components can be used. Examples include accelerometers or proximity sensors that communicate data with the controller 200. In other embodiments, the load conditions on various components of the wind turbine 160 can be determined indirectly.

[0032] Now for reference Figure 4A block diagram is shown illustrating suitable components that may be included in a controller (such as the controller 200 described herein) according to this disclosure. Therefore, Figure 4 The controller 200 shown may be a controller 200 or a separate controller. The separate controller may be configured to operate autonomously, i.e., independently of controller 200, at least under certain operating conditions, and may be able to perform tasks such as receiving and transmitting signals and processing data when controller 200 is in an inoperable state (such as when rotor 115 is locked and / or when wind turbine 160 is in idling mode).

[0033] Specifically, as shown, controller 200 may include one or more processors 202 and associated memory devices 206 configured to perform various computer-implemented functions (e.g., performing methods, steps, calculations, etc., and storing relevant data as disclosed herein). Processor 202 may further include a wind parameter estimator 204. Controller 200 may perform various functions, such as receiving, transmitting, and / or performing wind turbine control signals and controlling the overall operation of wind turbine 160. Controller 200 may be programmed to control overall operation based on information received from sensors 125, 126, 127, 128 (indications such as load, wind speed, wind direction, turbulence, component failure, etc.).

[0034] The controller 200 may also include a communication module 208 to facilitate communication between the controller 200 and components of the wind turbine 160 and their respective control systems. Further, the communication module 208 may include a sensor interface 210 (e.g., one or more analog-to-digital converters) to allow signals transmitted from sensors 125, 126, 127, 128 to be converted into signals that can be understood and processed by the controller 200. It should be appreciated that sensors 125, 126, 127, 128 may be communicatively coupled to the communication module 208 using any suitable means, such as, for example, wireless or wired connections (not shown).

[0035] As used herein, the term "controller" refers not only to integrated circuits included in a computer as known in the art, but also to microcontrollers, microcomputers, programmable logic controllers (PLCs), application-specific integrated circuits (ASICs), and other programmable circuits. Controller 200 is also configured to compute advanced control algorithms and communicate with various Ethernet or serial-based protocols (Modbus, OPC, CAN, etc.). Additionally, a memory device 206 configured with controller 200 may generally include memory elements, including but not limited to computer-readable media (e.g., random access memory (RAM)), computer-readable non-volatile media (e.g., flash memory), floppy disks, optical disc read-only memory (CD-ROM), magneto-optical disc (MOD), digital versatile optical disc (DVD), and / or other suitable memory elements. This memory device 206 may be generally configured to store suitable computer-readable instructions that, when executed by processor 202, configure controller 200 to perform the various functions described herein.

[0036] Now for reference Figure 5 This document illustrates a flowchart of an embodiment of a method 300 for mitigating vibrations occurring or potentially occurring on one or more rotor blades of a wind turbine (such as wind turbine 106) when it is in a non-operating state, according to this disclosure. As used herein, the term "non-operating state" or similar terms are generally understood to encompass an operating mode in which the wind turbine 160 neither supplies electrical power to nor draws electrical power from the grid, and is therefore configured to operate independently of the grid. For example, a non-operating state may include an idling state and / or a locked state. More specifically, in the locked state, the rotor 115 (and therefore the hub 110) of the wind turbine 160 is locked from rotation, for example due to installation, commissioning, maintenance tasks, and / or any other reason. In an embodiment, in the idling state, the wind turbine 160 does not generate power but is not shut down, and therefore can still rotate. The wind turbine 160 may idle for any reason, including, for example, low wind speed, maintenance needs, grid management, and / or to avoid damage due to excessively high wind speeds.

[0037] Furthermore, in embodiments, method 300 may use, for example, the foregoing references of this disclosure. Figure 1-4 The controller 200 discussed is used to perform this. Therefore, in embodiments, this disclosure contemplates that the controller 200 remains communicatively connected to at least the pitch drive system 107 in a locked and / or idling state. Other aspects of this disclosure rely on the determination of vibrations induced in one or more rotor blades 120 of the wind turbine 160.

[0038] also, Figure 5The steps are described in a specific order for illustrative and discussion purposes. Those skilled in the art will understand using the disclosure provided herein that the individual steps of method 300 or any of the methods disclosed herein may be adapted, modified, rearranged, performed concurrently, or modified in various ways without departing from the scope of this disclosure.

[0039] Optionally, as shown at (302), controller 200 may be configured to detect changes in one or more wind conditions. Thus, in such embodiments, if a specific change in wind condition is detected, controller 200 may activate method 300 as described herein. For example, in some embodiments, controller 200 may be configured to determine whether the wind speed near wind turbine 160 exceeds a speed threshold, and if so, controller 200 may activate method 300. In some embodiments, wind conditions may also include gusts, wind direction, wind acceleration, wind turbulence, wind shear, wind direction change, wake, updraft, etc.

[0040] In an embodiment, the controller 200 is further configured to determine the state of the wind turbine 160. For example, in an embodiment, as shown at (304), the controller 200 is configured to determine that the wind turbine 160 is in a non-operating state, for example by receiving signals from one or more sensors. In this embodiment, in order to determine the state of the wind turbine 160, the controller 200 may receive signals from one or more sensors, such as Figure 1-4 Sensors 125, 126, 127, and 128 are depicted and described herein. For example, in embodiments and as mentioned above, sensors 125, 126, 127, and 128 may include any suitable sensors for measuring various wind and / or operating parameters of the wind turbine 160. Further, in embodiments, sensors 125, 126, 127, and 128 may provide the controller 200 with signals corresponding to any one or a combination of the following: gusts, wind speed, wind direction, wind acceleration, wind turbulence, wind shear, wind direction change, wake, updraft, rotor speed, generator speed, power output, torque, load, etc. In some embodiments, the controller 200 may be configured to determine the state of the wind turbine 160 by receiving, processing, and analyzing one or more signals from one or more sensors, as described above.

[0041] As shown at (306), method 300 includes receiving a vibration signal via controller 200 that indicates vibration occurring or potentially occurring on one or more rotor blades 120. For example, controller 200 may be configured to receive a signal representing the vibration signal from sensor 121 described herein. For example, in an embodiment, controller 200 may be configured to determine the vibration signal by processing an input signal from sensor 121, which may include strain parameters. Further, in an embodiment, the input signal may include a waveform of the strain parameters changing over time, which may be received from sensor interrogation unit 124 and / or from load sensor 121. Furthermore, in an embodiment, the vibrations described herein may generally include SIV and VIV, as well as any other suitable type of vibration.

[0042] In a further embodiment, any suitable input signal can be used to determine the vibration signal. For example, the controller 200 may also be configured to analyze various parameters indicating specific wind conditions that are more likely to cause vibration of the rotor blades 120. Examples of such parameters include, but are not limited to, gusts, wind speed, wind direction, wind acceleration, wind turbulence, wind shear, wind direction change, wake, updraft, etc.

[0043] Still referencing Figure 5 As shown at (308), method 300 further includes comparing a vibration signal with a vibration threshold via a controller. For example, in an embodiment, controller 200 is configured to determine the vibration threshold based on one or more factors related to the design limits and / or safety of wind turbine 160. For example, the vibration threshold may represent a vibration level that could potentially damage wind turbine 160. Therefore, in some embodiments, the vibration threshold may be adjusted based on various factors such as wind turbine size, location, geometry, component strength, and other environmental factors.

[0044] In some embodiments, the specific turbine component of interest may vary when considering whether the vibration level is likely to cause damage to the wind turbine 160, and may include, for example, rotor blades 120 (such as blade root 34), nacelle 161, tower 170, rotor hub locking device (not shown), or any other component subjected to wind-induced loads. This determination may be made, for example, by controller 200 in real time based on input from strain / deformation sensor 121 discussed above.

[0045] As shown at (310), if the vibration signal exceeds a vibration threshold, the controller 200 is configured to cause one or more rotor blades 120 to continuously pitch across a pitch angle range for a specific period of time to mitigate vibration. As used herein, “continuous pitch,” “continuous pitch adjustment,” or similar terms are generally understood to mean that one or more rotor blades 120 continuously rotate around the pitch axis PA across a pitch angle range for a specific period of time without stopping. In some embodiments, the pitch angle range may span less than 20 degrees, such as less than 15 degrees, less than 10 degrees, or less than 5 degrees. Furthermore, in embodiments, the controller 200 may be programmed to optimize the pitch angle range. For example, the controller 200 may use statistical analysis or machine learning to optimize the pitch angle range.

[0046] Additionally, in embodiments, controller 200 may be configured to determine the size and / or average value of a pitch angle range suitable for reducing vibrations as described herein. Furthermore, as described herein, the size of the pitch angle range generally refers to a specific degree defined by a lower pitch angle and an upper pitch angle, while the average value of the pitch angle range generally refers to its ordinary and general meaning as the center value of a set of values ​​(e.g., the center value of the pitch angle range).

[0047] In some embodiments, once the pitch angle range for rotor blade 120 is calculated based on the parameters identified herein, controller 200 can generate pitch commands to continuously adjust rotor blade 120 across the pitch angle range spanning the average angle of attack for rotor blade 120. Therefore, in embodiments, this disclosure is configured to ensure that SIV / VIV angles of attack and other vibrations that may occur on rotor blade 120 are avoided along the entire wingspan.

[0048] In some embodiments, the controller 200 may be configured to continuously pitch one or more rotor blades 120 at varying pitch rates. In other embodiments, the pitch rate may remain constant. In still other embodiments, the pitch rate may vary over a specific period of time during which the controller 200 continuously pitches one or more rotor blades 120.

[0049] The specific time period during which the controller 200 continuously pitches the rotor blades may also vary in the different embodiments described herein. In some embodiments, the controller 200 may be configured to continuously pitch one or more rotor blades 120 whenever the controller 200 determines that a vibration signal exceeds a vibration threshold, as shown at (308). In other embodiments, the controller 200 may be configured to continuously pitch one or more rotor blades 120 for a specific time period, such as at least 10 seconds, at least 20 seconds, at least 30 seconds, at least 40 seconds, at least 50 seconds, at least one minute, or at least two minutes.

[0050] In some embodiments, the controller 200 may be configured to continuously pitch each rotor blade 120 based on different pitch angle ranges, which may be periodically updated based on detected changes in wind parameters. For example, the average pitch angle range for each rotor blade 120 may be based on an optimal angle of attack, which may be determined by the initial blade orientation and / or varying wind parameters at different relative rotational positions.

[0051] Still referencing Figure 5 As shown at (312), method 300 may optionally include comparing the vibration signal with a vibration threshold via controller 200 and confirming whether the vibration signal remains above the vibration threshold. In an embodiment, if controller 200 determines that the vibration signal no longer exceeds the vibration threshold, controller 200 may stop continuously adjusting the rotor blades 120 across the pitch angle range. In an alternative embodiment, as shown at (314), if the vibration signal remains above the vibration threshold, controller 200 may be configured to modify at least one of the size of the pitch angle range or the average value of the pitch angle range, for example, to further reduce vibration. In some embodiments, modifying the size of the pitch angle range may include decreasing or increasing the size of the pitch angle range.

[0052] Further embodiments of this disclosure may include deactivation method 300, for example, when the vibration signal no longer exceeds a vibration threshold and / or when a specific change in nearby wind conditions is detected. For example, after continuous pitch control across a pitch angle range for a specific period of time, controller 200 may be configured to measure wind conditions, and upon detecting a change in wind conditions, controller 200 may stop continuous pitch control across the pitch angle range. In such embodiments, examples of measured wind conditions may include gusts, wind speed, wind direction, wind acceleration, wind turbulence, wind shear, wind direction change, wake, updraft, etc. In some embodiments, controller 200 may be configured to deactivate method 300 when an increase in one or more of the measured wind conditions described above is detected. In alternative embodiments, controller 200 may be configured to deactivate method 300 when a decrease in one or more of the measured wind conditions described above is detected.

[0053] In some embodiments of this disclosure, the controller 200 may also be configured to coordinate the pitching of the rotor blades 120 in phases to reduce varying levels of vibration throughout the wind turbine 160. For example, the rotor blades 120 may pitch in phases to reduce vibrations caused by tilting, yaw, forward and backward movements, etc.

[0054] For any of the embodiments described herein, controller 200 may be programmed to use a predefined setting as the default method if measurement feedback is unavailable or becomes unavailable.

[0055] Furthermore, in embodiments, the methods described herein can be used to supplement an automatic pitch control system as described in U.S. Application Serial No. 12 / 012,934, which is incorporated herein by reference in its entirety. Therefore, in embodiments where the automatic pitch control system may become ineffective, such as when the wind turbine 160 is experiencing vibrations of a certain level, the method 300 described herein can be used to introduce continuous pitch adjustment to the automatic pitch control system instead of reverting to a feathering state. In such embodiments, as mentioned, method 300 may involve continuous pitch adjustment across a pitch angle range based on an automatically calibrated pitch angle. For example, the average of the pitch angle range may be the automatically calibrated pitch angle. A further aspect of this embodiment may include manually or automatically switching between the method 300 described herein and the automatic pitch control system based on the vibration level.

[0056] In some embodiments, method 300 can supplement the automatic pitch control system by using continuous pitch adjustment near the feathering position in high wind conditions. Therefore, the systems and methods of this disclosure provide a reduced risk of SIV or VIV compared to maintaining the rotor blades 120 in the feathering position when automatic pitch adjustment is not feasible due to strong winds. In this embodiment, method 300 may include continuously pitching the rotor blades 120 about the feathering position, such as from about 85 degrees to about 95 degrees. As described above, this embodiment may also allow dynamic switching between automatic pitch adjustment and continuous pitch adjustment based on wind speed conditions.

[0057] Further aspects of the invention are provided by the subject matter of the following provisions: A method for mitigating vibrations that occur or potentially occur on one or more rotor blades of a wind turbine when the turbine is in an inoperable state, the method comprising: receiving, via a controller, a vibration signal indicating that the vibrations occur or potentially occur on the one or more rotor blades; comparing, via the controller, the vibration signal with a vibration threshold; and, in response to the vibration signal being higher than the vibration threshold, continuously adjusting the pitch of the one or more rotor blades back and forth across a pitch angle range for a specific time period to mitigate the vibrations.

[0058] The method according to any of the foregoing provisions further includes, after continuously adjusting the pitch back and forth across the pitch angle range for the specific time period, confirming whether the vibration signal remains above the vibration threshold.

[0059] The method described according to any of the foregoing clauses further includes modifying at least one of the size or average value of the pitch angle range.

[0060] The method according to any of the foregoing clauses further includes continuously modifying at least one of the size or average value of the pitch angle range until the vibration signal drops below the vibration threshold.

[0061] The method described according to any of the foregoing clauses further includes using at least one of statistical analysis or machine learning to optimize the pitch angle range.

[0062] The method according to any of the foregoing clauses, wherein the specific time period is at least about 10 seconds.

[0063] The method according to any of the foregoing clauses, wherein the pitch angle range is less than about 15 degrees.

[0064] The method according to any of the foregoing provisions further includes maintaining the pitch rate of the continuous pitch adjustment of the one or more rotor blades at a constant rate.

[0065] The method according to any of the foregoing provisions further includes continuously varying the pitch rate of the one or more rotor blades.

[0066] The method according to any of the foregoing clauses further includes: determining whether the wind speed near the wind turbine exceeds a speed threshold; and when the wind speed near the wind turbine exceeds the speed threshold, starting to receive the vibration signal.

[0067] The method according to any of the foregoing clauses further includes measuring the vibration signal using at least one sensor or determining at least one of the vibration signals via the controller.

[0068] According to any of the foregoing provisions, the method further includes measuring wind conditions and stopping the pitch adjustment when a specified wind condition is detected after continuously adjusting the pitch back and forth across the pitch angle range for the specified time period.

[0069] The method according to any of the foregoing clauses, wherein the wind condition includes at least one of gusts, wind direction, wind acceleration, wind turbulence, wind shear, wind direction change, wake, or updraft.

[0070] According to any of the foregoing provisions, the method of continuously adjusting the pitch of the one or more rotor blades back and forth across the pitch angle range for the specific time period further includes coordinating the pitch adjustment between the multiple blades based on at least one of the phase or load on at least one of the one or more rotor blades or other turbine components.

[0071] A wind turbine includes: a plurality of rotor blades on a rotatable hub; one or more sensors configured to detect wind parameters affecting the plurality of rotor blades; a pitch system configured to change the pitch angle of one or more of the plurality of rotor blades; and a controller operatively communicating with the pitch system, wherein, when the wind turbine is in a non-operating or locked rotor state, the controller is configured to perform a plurality of operations including: receiving a vibration signal indicating vibration occurring or potentially occurring on the one or more of the plurality of rotor blades; comparing the vibration signal with a vibration threshold via the controller; and, in response to the vibration signal being higher than the vibration threshold, continuously adjusting the pitch of one or more of the plurality of rotor blades across a pitch angle range for a specific time period to mitigate the vibration.

[0072] According to any of the foregoing provisions, in a wind turbine, after one or more rotor blades of the plurality of rotor blades are continuously pitched back and forth across the pitch angle range for the specified time period, the controller is further configured to confirm whether the vibration signal remains above the vibration threshold.

[0073] According to any of the foregoing provisions, the wind turbine, wherein the controller is further configured to modify at least one of the size or average value of the pitch angle range.

[0074] According to any of the preceding clauses, the wind turbine, wherein the controller is further configured to continuously modify at least one of the size or average value of the pitch angle range until the vibration signal drops below the vibration threshold.

[0075] According to any of the foregoing provisions, the wind turbine, wherein the plurality of operations further includes using at least one of statistical analysis or machine learning to optimize the pitch angle range.

[0076] According to any of the foregoing provisions, the continuous back-and-forth pitch adjustment of one or more rotor blades across the pitch angle range for the specified time period is further defined as coordinating the pitch adjustment among the multiple blades based on at least one of the phases on the one or more rotor blades and / or other turbine components or the calculated or measured loads.

[0077] This written description uses examples to disclose the invention, including the best mode, and also enables those skilled in the art to practice the invention, including making and using any device or system and performing any of the combined methods. The patentable scope of the invention is defined by the claims and may include other examples that would occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they comprise structural elements that are not different from the literal language of the claims, or if they comprise equivalent structural elements that are not substantially different from the literal language of the claims.

Claims

1. A method for mitigating vibrations that occur or potentially occur on one or more rotor blades of a wind turbine when the wind turbine is in an inoperable state, the method comprising: Vibration signals indicating vibrations occurring or potentially occurring on the one or more rotor blades are received via a controller; The controller compares the vibration signal with a vibration threshold. as well as In response to the vibration signal being higher than the vibration threshold, the one or more rotor blades are continuously adjusted back and forth across the pitch angle range for a specific period of time to mitigate the vibration.

2. The method according to claim 1, further comprising, after continuously adjusting the pitch of the one or more rotor blades back and forth across the pitch angle range for the specific time period, confirming whether the vibration signal remains above the vibration threshold.

3. The method of claim 2, further comprising modifying at least one of the size or average value of the pitch angle range.

4. The method of claim 3, further comprising continuously modifying at least one of the size or average value of the pitch angle range until the vibration signal drops below the vibration threshold.

5. The method of claim 1, further comprising using at least one of statistical analysis or machine learning to optimize the pitch angle range.

6. The method according to claim 1, wherein, The specific time period is at least approximately 10 seconds.

7. The method according to claim 1, wherein, The pitch angle range is less than approximately 15 degrees.

8. The method of claim 1, further comprising maintaining the pitch rate of the one or more rotor blades continuously pitched at a constant rate.

9. The method of claim 1, further comprising continuously varying the pitch rate of the one or more rotor blades.

10. The method of claim 1, further comprising: Determine whether the wind speed near the wind turbine exceeds a speed threshold; as well as When the wind speed near the wind turbine exceeds the speed threshold, the vibration signal is received.

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