Systems and methods for reducing vibrations in wind turbine blades using automatic tunable spring mass dampers

Abstract

A system and method are provided for reducing vibrations and loads in one or more rotor blades on a rotor hub of a wind turbine when the rotor hub is in a locked or idle condition. An electronically tunable spring mass damper is attached to a fixed location on one or more of the rotor blades. The spring mass dampers are maintained on the rotor blades during a locked or idle condition of the rotor hub. The method includes sensing movement of the mass member caused by vibrations induced in the blade. Based on the sensed movement of the mass member, the spring mass damper is automatically tuned to the amplitude of the vibration by operating the motor as a generator in a virtual damper mode, and / or the spring mass damper is automatically tuned to the frequency of the vibration by operating the motor as a motor-generator in a virtual spring mode.

Description

Technical Field

[0001] The present disclosure relates generally to wind turbine power generation systems and, more particularly, to systems and methods for damping vibrations and loads in a wind turbine, particularly when the rotor hub is not operating in a locked or idling condition. Background Art

[0002] Modern wind turbines are commonly used to supply electricity to an electrical grid. Wind turbines of this type generally comprise a tower and a rotor arranged on the tower. The rotor, which typically comprises a hub and a plurality of blades, is set to rotate under the influence of the wind on the blades, wherein the rotation generates a torque which is transmitted to a generator via a rotor shaft, either directly ("direct drive") or by using a gearbox. In this way, the generator produces electricity which can be supplied to an electrical grid.

[0003] There is a trend to make wind turbine blades longer and longer to capture more wind and convert wind energy into electricity. This results in blades that are more flexible and more prone to aeroelastic instabilities, such as vibrations of the blades, which can also lead to unstable blade oscillations. Vibrating blades create a major potential risk of damage to various components throughout the wind turbine.

[0004] When the wind turbine is operating, the wind turbine controller may (directly or indirectly) operate auxiliary drive systems, such as the pitch system, or generator torque, to reduce the loads on the blades and thereby counteract blade vibrations.

[0005] However, when the wind turbine is in a stationary state (idling or locked), the problem of aeroelastic instabilities can be severe. When the rotor is locked to prevent rotation (e.g. due to installation, commissioning or maintenance tasks), the blades can experience aeroelastic instabilities (including different types of vibrations when the angle of attack is within certain ranges). Because the rotor is locked, the rotation of the rotor cannot be used to reduce the loads that cause these vibrations.

[0006] During stationary conditions, at least two types of vibrations may occur. The first is vortex induced vibrations (VIV) at certain angles of attack and may or may not include cross-flow vortices that are shed at frequencies close to the blade eigenfrequency or system frequency. The second is stall induced vibrations (SIV) when the angle of attack is close to the stall angle and flow interactions may cause blade vibrations. The angle of attack may be understood as the geometric angle between the flow direction of the wind and the chord of the rotor blade. There may also be a cross-flow component to the flow.

[0007] Vortex and stall induced vibrations are phenomena that, if not adequately designed or compensated for, can lead to blade failure or accelerate blade damage.

[0008] Current solutions to the mentioned problems include using aerodynamic devices attached to the blades to reduce vortices and / or increase damping. However, this solution can increase the loads due to drag, as well as the cost and time of installing and removing such devices.

[0009] Another current practice for wind turbines when not producing power involves setting the pitch angle of the rotor blades to approximately 90 degrees when the rotor is yawed into the wind and prevented from rotating by means of locking pins. This particular pitch angle can reduce the loads on the blades (at least with respect to some wind conditions). However, when the pitch angle is set at the vane position, the locking pins can be subject to higher loads, and even in this position, all vibrations cannot be avoided, especially if the wind direction changes over time.

[0010] US Patent No. 9316202 proposes a method and system for preventing vibration of wind turbine blades when the rotor is locked or idling at low speed, which involves attaching a releasable cover to the blade, which provides a non-aerodynamic surface to an area of ​​the blade. The blade cover is described as a sleeve of mesh material that can be positioned on the blade by a service engineer using guidelines before installation or in the field.

[0011] The present disclosure provides an alternative effective means to reduce or prevent vibrations or oscillations in wind turbine blades when the wind turbine is in a non-operating mode where the rotor hub is unable to yaw and lock or idle through the use of unique vibration dampers, which will provide benefits in terms of cost, time and ease of installation, as well as effectiveness. Summary of the invention

[0012] Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

[0013] The present disclosure includes a method for preventing or at least reducing vibrations and loads in one or more rotor blades on a rotor hub of a wind turbine when the wind turbine is in a non-operating mode with the rotor hub in a locked or idling state. This mode of the wind turbine may occur, for example, during installation, repair, maintenance, disconnection from the grid, or any other scenario requiring the rotor hub to be locked to prevent rotation (i.e., at rest) or to allow idling.

[0014] The method includes attaching an electronically tunable spring mass damper at a fixed position on the blade during a locked or idling state of the rotor hub, the tunable spring mass damper having a mass member that moves along a travel path. The spring mass damper includes an electric motor that can be operated as a motor or a generator. For example, the electric motor can be a conventional DC motor that can also act as a generator. The method includes determining the amplitude and frequency of vibrations induced in the blade during the locked or idling state, and sensing the movement of the mass member caused by the vibrations induced in the blade. Based on the sensed movement of the mass member, the damping function of the spring mass damper is automatically tuned to adjust the amplitude of the vibration by operating the electric motor as a generator in a virtual damper mode. Alternatively or additionally, the spring mass damper stiffness is automatically tuned to the frequency of the vibration by operating the electric motor as a motor-generator in a virtual spring mode. In a particular embodiment, two tuning functions are performed.

[0015] In a particular embodiment, the spring mass damper includes a flywheel that is geared with the motor as the mass member moves along the travel path. In the virtual damper mode, the motor generates a counter torque on the flywheel that is proportional to the speed of the spring mass damper as the spring mass damper decelerates toward the end of the travel path, and in the virtual spring mode, the motor generates an additional torque or counter torque to the flywheel that is proportional to the position of the spring mass damper as the spring mass damper accelerates away from the end of the travel path. In this embodiment, in the virtual damper mode, the motor operates as a generator and charges the battery. In the virtual spring mode, the motor operates as a motor for one half cycle of the spring mass damper travel and as a generator in the other half cycle of the spring mass damper travel, similar to the physical kinetic energy behavior of expanding and contracting springs, where the motor energy losses are supplied by the battery.

[0016] The flywheel may be in geared engagement with a track that extends along and defines a travel path such that the flywheel is rotationally driven when the mass member moves along the travel path. The flywheel is coupled to a shaft that is coupled to the motor.

[0017] An advantage of the method is that the steps of automatically tuning the spring-mass damper are completely performed by the spring-mass damper without requiring external operator or device action.

[0018] According to certain embodiments, the position or movement of the mass member along the travel path is continuously or periodically sensed using one or more sensors with respect to the spring mass damper configuration. The position data is used for various tuning functions.

[0019] Another advantage of the present approach is that the spring mass damper is insensitive to temperature changes in operation.

[0020] In certain embodiments, the spring mass damper communicates with a remote central controller, wherein at least one operating parameter of the spring mass damper is remotely adjusted or controlled by the remote central controller. The spring mass damper may also communicate with a mobile smart device, which in turn communicates with the remote central controller, wherein an operator adjusts the operating parameter of the spring mass damper via the mobile smart device or via the remote central controller.

[0021] Each blade on a rotor hub of a wind turbine may be configured with one of the spring mass dampers, wherein each of the spring mass dampers is in communication with a wind turbine controller. The wind turbine controller may be in communication with a remote central controller.

[0022] The present invention also includes a wind turbine configured to reduce vibrations and loads in rotor blades during a non-operating mode. The wind turbine includes a plurality of rotor blades on a rotor hub, wherein in the non-operating mode of the wind turbine, the rotor hub is in a locked or idling state. The wind turbine also includes a spring mass damper attached at a fixed position on one or more of the rotor blades, the spring mass damper having a mass member that can move along a travel path. One or more sensors are configured within the spring mass damper to sense movement of the mass member along the travel path, wherein the movement is generated by vibrations or oscillations induced in the rotor blades during the locked or idling state of the rotor hub. A controller is used with the spring mass damper and is configured to perform one or both of the following: (a) automatically tune the spring mass damper to the amplitude of the vibration based on the sensed movement of the mass member by operating the motor as a generator in a virtual damper mode; or (b) automatically tune the spring mass damper to the frequency of the vibration by operating the motor as a motor-generator in a virtual spring mode.

[0023] In a certain embodiment, the spring mass damper is in communication with a remote central controller, wherein one or more operating parameters of the spring mass damper are remotely adjusted or controlled by the remote central controller.

[0024] In another embodiment, the spring mass damper may also communicate with a mobile smart device, wherein an operator adjusts operating parameters of the spring mass damper via the mobile smart device or via a remote central controller.

[0025] Each of the wind turbine's rotor blades may be configured with one of the spring mass dampers, each of the spring mass dampers being in communication with a wind turbine controller, which in turn is in communication with a remote central controller.

[0026] In a particular configuration, the spring mass damper includes a flywheel that is gearedly engaged with a motor as the mass member moves along the travel path, wherein in a virtual damper mode, the motor generates a reaction torque on the flywheel that is proportional to the speed of the spring mass damper as the spring mass damper decelerates toward the end of the travel path, and in a virtual spring mode, the motor generates an additional torque or reaction torque to the flywheel that is proportional to the position of the spring mass damper as the spring mass damper accelerates away from the end of the travel path.

[0027] In an embodiment, a flywheel may be in geared engagement with a track gear extending along the travel path such that the flywheel is rotationally driven as the mass member moves along the travel path, the flywheel being coupled to a shaft coupled to the motor.

[0028] In another embodiment, the spring mass damper further comprises a battery, wherein in virtual damper mode the electric machine operates as a generator and charges the battery, and in virtual spring mode the electric machine operates as a motor or generator, the losses of which are supplied by the battery.

[0029] The present invention also encompasses a system for reducing vibrations and loads in a rotor blade of a wind turbine during a non-operating mode, wherein the rotor hub of the wind turbine is in a locked or idling state. The system comprises a spring mass damper configured with the functionality described herein. Technical Solution 1. A method for reducing vibrations and loads in blades on a rotor hub of a wind turbine when the rotor hub is in a locked or idling state, the method comprising: attaching an electronically tunable spring-mass damper at a fixed position on the blade during the locked or freewheeling condition of the rotor hub, the tunable spring-mass damper having a mass member that moves along a travel path; The spring mass damper comprises an electric machine operable as a motor or a generator; determining an amplitude and frequency of vibrations induced in said blade during said locked or idling condition; sensing movement of the mass member caused by the vibration induced in the blade; and Based on the sensed movement of the mass member, one or both of the following are performed: (a) automatically tuning the spring mass damper to the amplitude of the vibration by operating the motor as a generator in a virtual damper mode; or (b) automatically tuning the spring mass damper to the frequency of the vibration by operating the motor as a motor-generator in a virtual spring mode. Technical Solution 2. A method according to Technical Solution 1, the method comprising performing both (a) and (b), wherein the spring mass damper comprises a flywheel that is gear-engaged with the motor when the mass member moves along the travel path, wherein, in the virtual damper mode, when the spring mass damper approaches the end of the travel path and decelerates at the end of the travel path, the motor generates a counter-torque on the flywheel, and in the virtual spring mode, when the spring mass damper accelerates away from the end of the travel path, the motor generates an additional torque or counter-torque on the flywheel. Technical Solution 3. A method according to Technical Solution 2, wherein, in the virtual damper mode, the motor operated as the generator charges the battery, and in the virtual spring mode, the motor operated as the motor-generator is powered by the battery. Technical Solution 4. A method according to Technical Solution 2, wherein the flywheel is gear-engaged with a track gear extending along the travel path, so that when the mass component moves along the travel path, the flywheel is rotationally driven, the flywheel is connected to a shaft, and the shaft is connected to the motor. Technical Solution 5. A method according to Technical Solution 1, wherein the step of automatically tuning the spring mass damper is completely completed by the spring mass damper without the need for action by an external operator or device. Technical Solution 6. A method according to Technical Solution 1, wherein the position or movement of the mass member along the travel path is continuously or periodically sensed using one or more sensors configured with respect to the spring mass damper. Technical Solution 7. A method according to Technical Solution 1, wherein the spring mass damper is operationally insensitive to temperature changes. Technical Solution 8. The method according to Technical Solution 1, wherein the spring mass damper communicates with a remote central controller, wherein at least one operating parameter of the spring mass damper is remotely adjusted by the remote central controller. Technical Solution 9. A method according to Technical Solution 8, wherein the spring mass damper also communicates with a mobile smart device, and the mobile smart device communicates with the remote central controller, wherein the operator adjusts the operating parameters of the spring mass damper via the mobile smart device or via the remote central controller. Technical Solution 10. A method according to Technical Solution 8, wherein each blade on the rotor hub is constructed with one of the spring mass dampers, each of the spring mass dampers communicates with a wind turbine controller, and the wind turbine controller communicates with the remote central controller. Technical solution 11. A wind turbine configured to reduce vibrations and loads in rotor blades during a non-operating mode of the wind turbine, comprising: a plurality of rotor blades on a rotor hub; in the non-operational mode of the wind turbine wherein the rotor hub is in a locked or idling state, the wind turbine further comprising a tunable spring-mass damper attached at a fixed position on one or more of the rotor blades, the spring-mass damper comprising a mass member movable along a travel path; one or more sensors configured with respect to the spring-mass damper to sense movement of the mass member along the travel path, wherein the movement is generated by vibrations or oscillations induced in the rotor blades during the locked or freewheeling condition of the rotor hub; The spring mass damper comprises an electric machine operable as a motor or a generator; and a controller constructed with respect to the spring-mass damper and configured to perform one or both of the following: (a) automatically tune the spring-mass damper to the amplitude of the vibration by operating the motor as a generator in a virtual damper mode based on the sensed movement of the mass member; or (b) automatically tune the spring-mass damper to the frequency of the vibration by operating the motor as a motor-generator in a virtual spring mode. Technical Solution 12. A wind turbine according to Technical Solution 11, wherein the spring mass damper communicates with a remote central controller, wherein one or more operating parameters of the spring mass damper are remotely adjusted by the remote central controller. Technical Solution 13. A wind turbine according to Technical Solution 12, wherein the spring mass damper also communicates with a mobile smart device, wherein an operator adjusts the operating parameters of the spring mass damper via the mobile smart device or via the remote central controller. Technical Solution 14. A wind turbine according to Technical Solution 11, wherein each of the rotor blades is constructed with one of the spring mass dampers, each of the spring mass dampers communicates with the wind turbine controller, and the wind turbine controller communicates with the remote central controller. Technical Solution 15. A wind turbine according to Technical Solution 11, wherein the spring mass damper includes a flywheel, and when the mass component moves along the travel path, the flywheel is gear-engaged with the motor, wherein, in the virtual damper mode, when the spring mass damper decelerates toward the end of the travel path, the motor generates a counter-torque to the flywheel, and in the virtual spring mode, when the spring mass damper accelerates toward or away from the end of the travel path, the motor generates an additional torque or counter-torque to the flywheel. Technical Solution 16. A wind turbine according to Technical Solution 15, wherein the flywheel is gear-engaged with a track gear extending along the travel path, so that when the mass component moves along the travel path, the flywheel is rotationally driven, the flywheel is connected to a shaft, and the shaft is connected to the motor. Technical Solution 17. A wind turbine according to Technical Solution 11, wherein the spring mass damper also includes a battery, wherein in the virtual damper mode, the motor operates as a generator and charges the battery, and in the virtual spring mode, the motor operates as a motor-generator and is powered by the battery. Technical solution 18. A system for reducing vibrations and loads in a rotor blade of a wind turbine during a non-operating mode of the wind turbine, wherein the rotor hub of the wind turbine is in a locked or idling state, the system comprising: a tunable spring-mass damper configured for attachment at a fixed location on one or more of the rotor blades, the spring-mass damper comprising a mass member movable along a travel path; one or more sensors configured with respect to the spring-mass damper to sense movement of the mass member along the travel path, wherein the movement is generated by vibrations or oscillations induced in the rotor blades during the locked or freewheeling condition of the rotor hub; The spring mass damper comprises an electric machine operable as a motor or a generator; and a controller constructed with respect to the spring-mass damper and configured to perform one or both of the following: (a) automatically tune the spring-mass damper to the amplitude of the vibration by operating the motor as a generator in a virtual damper mode based on the sensed movement of the mass member; or (b) automatically tune the spring-mass damper to the frequency of the vibration by operating the motor as a motor-generator in a virtual spring mode. Technical Solution 19. A system according to Technical Solution 18, wherein the spring mass damper includes a flywheel, and when the mass member moves along the travel path, the flywheel is gear-engaged with the motor, wherein, in the virtual damper mode, when the spring mass damper decelerates toward the end of the travel path, the motor generates a counter-torque to the flywheel, and in the virtual spring mode, when the spring mass damper accelerates toward or away from the end of the travel path, the motor generates an additional torque or counter-torque to the flywheel, and wherein the flywheel is gear-engaged with a track gear extending along the travel path, so that when the mass member moves along the travel path, the flywheel is rotationally driven, the flywheel is connected to a shaft, and the shaft is connected to the motor. Technical Solution 20. A system according to Technical Solution 18, wherein the spring mass damper also includes a battery, wherein in the virtual damper mode, the motor operates as a generator and charges the battery, and in the virtual spring mode, the motor operates as a motor-generator and is powered by the battery.

[0030] These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims.The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] A complete and open disclosure of the present invention including its best mode for one skilled in the art is set forth in the specification with reference to the accompanying drawings, in which:

[0032] Figure 1 showing a perspective view of a wind turbine;

[0033] Figure 2 shows a simplified view of a wind turbine blade equipped with a tunable spring mass damper;

[0034] Figure 3 is a perspective view of a tunable spring mass damper mounted to a wind turbine blade;

[0035] Figure 4 yes Figure 3 A more detailed perspective of the tunable spring mass damper;

[0036] Figure 5a yes Figure 4 Side view of the spring mass damper;

[0037] Figure 5b yes Figure 4 Bottom view of the spring mass damper;

[0038] Figure 5c yes Figure 4 Top view of the spring mass damper;

[0039] Figure 6 is a top view of an alternative embodiment of a tunable spring mass damper;

[0040] Figure 7 is a diagram of the control hardware for a tunable spring-mass damper;

[0041] Figure 8 is the control diagram for the tunable spring mass damper; and

[0042] Fig. 9 is a diagram of control hardware for a wind turbine utilizing multiple tunable spring mass dampers.

[0043] Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention. DETAILED DESCRIPTION

[0044] Reference will now be made in detail to embodiments of the present invention, one or more examples of which are shown in the accompanying drawings. Each example is provided by way of explanation of the present invention without limiting the present invention. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made in the present invention without departing from the scope or spirit of the present invention. For example, a feature shown or described as part of an embodiment may be used together with another embodiment to produce yet another embodiment. Therefore, it is intended that the present invention covers such modifications and variations within the scope of the appended claims and their equivalents.

[0045] Referring now to the accompanying drawings, Figure 1 A perspective view of one embodiment of a wind turbine 10 according to the present disclosure is shown. As shown, the wind turbine 10 generally includes a tower 12 extending from a support surface 14, a nacelle 16 mounted on the tower 12, and a rotor 18 coupled to the nacelle 16. The rotor 18 includes a rotatable hub 20 and at least one rotor blade 22 coupled to the hub 20 and extending outwardly from the hub 20. For example, in the illustrated embodiment, the rotor 18 includes three rotor blades 22. However, in alternative embodiments, the rotor 18 may include more or less than three rotor blades 22. Each rotor blade 22 may be spaced about the hub 20 to facilitate rotating the rotor 18 so that kinetic energy can be converted from the wind into usable mechanical energy and subsequently into electrical energy. For example, the hub 20 may be rotatably coupled to a generator 24 positioned within the nacelle 16 to allow electrical energy to be generated.

[0046] The wind turbine 10 may also include a wind turbine controller 24 centered within the nacelle 16. However, in other embodiments, the controller 24 may be located within any other component of the wind turbine 10 or at a location outside the wind turbine 10. In addition, the controller 24 may be communicatively coupled to any number of components of the wind turbine 10 in order to control the operation of such components and / or implement corrective or control actions. For example, the controller 24 may communicate with a separate pitch drive system associated with each rotor blade 22 in order to pitch such blades about a corresponding pitch axis 28. In this regard, the controller 24 may include a computer or other suitable processing unit. Therefore, in several embodiments, the controller 24 may include suitable computer-readable instructions that, when executed, configure the controller 24 to perform various different functions, such as receiving, transmitting and / or executing wind turbine control signals. Therefore, the controller 24 may generally be configured to control various operating modes (e.g., startup or shutdown sequences), de-rating or up-rating of the wind turbine, and / or individual components of the wind turbine 10.

[0047] The present disclosure relates to situations in which the wind turbine 10 is not operating (e.g., not generating electrical power) and the rotor 18 (and therefore the rotor hub 20) is locked from rotation or is idling (e.g., due to installation, commissioning, maintenance tasks, or any other reason). In the locked or idling state of the rotor 18, the controller 24 may remain communicatively coupled to at least the pitch drive system. Alternatively, during the locked or idling state of the rotor, the "controller" functionality may also be provided by a separate dedicated controller. The dedicated controller may be configured to operate autonomously, i.e., independently of the wind turbine controller 24, at least under some operating conditions, and may be capable of performing tasks such as receiving and transmitting signals and processing data when the wind turbine controller 24 is otherwise unavailable.

[0048] Figure 1 The wind turbine 10 may be placed in an offshore or onshore location.

[0049] As used herein, the term "controller" refers not only to what is known in the art as an integrated circuit included in a computer, but also to microcontrollers, microcomputers, programmable logic controllers (PLCs), application specific integrated circuits, and other programmable circuits. The controller is also configured to calculate advanced control algorithms and couple to a variety of Ethernet or serial-based protocols (Modbus, OPC, CAN, etc.). In addition, the (multiple) storage devices configured with respect to the controller may generally include (multiple) storage elements, which include but are not limited to computer-readable media (e.g., random access memory (RAM)), computer-readable non-volatile media (e.g., flash memory), floppy disks, compact disk read-only memories (CD-ROMs), magneto-optical disks (MODs), digital versatile disks (DVDs), and / or other suitable storage elements. Such (multiple) storage devices may generally be configured to store suitable computer-readable instructions that, when executed by (multiple) processors 402, configure the controller to perform various functions as described herein.

[0050] Refer again Figure 1 Each of the rotor blades 22 includes a spring mass damper 44 according to aspects of the present disclosure mounted on the rotor blade 22 , such as at a fixed location closer to the blade tip than to the blade root.

[0051] Figure 2 is a view of a conventional rotor blade 22 including opposing blade roots 30, leading edges 36, trailing edges 38, suction sides 42, and pressure sides 40. Also indicated is the chord-wise dimension 34 of the blade 22. A spring mass damper 44 is mounted chord-wise to the suction side 42 of the blade 22 generally adjacent to the blade tip 32. The spring mass damper may also be mounted only to the suction side 42 of the rotor blade 22. The spring mass damper 44 is explained in more detail below.

[0052] Figure 3 is a perspective exterior view of an embodiment of a spring mass damper 44 on a rotor blade 22, and in particular illustrates an embodiment of an attachment system 45 for securing the spring mass damper to the blade. The attachment system includes opposing clamp shells 46 that conform to the outer pressure side surface 40 and suction side surface 42 of the blade. The clamp shells 46 extend across the chord-wise width of the rotor blade 22 and include a leading edge flange 48 and a trailing edge flange 50. The spring mass damper 44 includes a base 56 that extends over one of the clamp shells 46 between the flanges 48, 50. The base 56 is bolted to the flanges using bolts 52, wherein the bolts 52 are also used to bolt the opposing flange 48 and the opposing flange 50 together.

[0053] It should be appreciated that the spring mass damper 44 may be mounted to the rotor blade using any suitable non-permanent attachment system including mechanical fasteners, adhesives, inflatable devices, and the like.

[0054] The spring mass damper 44 includes a housing 54 mounted to a base 56, wherein working components of the spring mass damper 44 are housed within the housing 54, as described in more detail below. The housing 56 includes side walls 68, end walls 70, and a top 60. It should be appreciated that the housing 56 may have any geometric shape.

[0055] Reference Figure 4 Perspective drawing and Figure 5a-5c 6, provide an embodiment of a spring mass damper 44 according to aspects of the present invention. The spring mass damper 44 is configured to reduce vibrations and loads in the rotor blades during a non-operating mode of the wind turbine, wherein the rotor hub is in a locked or idling state. The spring mass damper 44 is installed to at least one of the rotor blades, and preferably all of the rotor blades (as discussed above), before or shortly after the wind turbine is placed in the non-operating mode or during installation of the wind turbine. As the operating conditions experienced by the wind turbine change during the locked or idling state, the spring mass damper 44 is capable of tuning (amplitude / stroke length and frequency) to the excitation frequency or system frequency of the corresponding rotor blade, as explained in more detail below.

[0056] The spring mass damper 44 includes a mass member 47 that moves along a travel path within the spring mass damper 44. The term "mass member" is used herein to collectively refer to the mass of all members on (and including) the frame 72 that move along a track 64 within the spring mass damper 44, as described in more detail below. The track 64 defines a maximum travel length of the travel path, such as Figure 7 Depicted in.

[0057] The illustrated embodiment of the spring mass damper 44 includes a flywheel 74 in geared engagement with a motor 80. The spring mass damper is tuned by controlling and varying the force applied by the motor 80 to the mass member 47 as the mass member 47 moves back and forth along the travel path defined by the track 64, as discussed in more detail below. This tuning function is performed by the spring mass damper 44 via an internal electronic controller 100 ( Figure 6 and Figure 7 ) is done automatically and completely. Thus, when the environmental or operating conditions experienced by the wind turbine during the non-operating mode change, resulting in changes in the vibrations or oscillations induced in the blades, the spring mass damper 44 is effectively and automatically tuned with respect to the changes in vibrations or oscillations.

[0058] The flywheel 74 is rotatably configured on the frame 72, which moves linearly relative to the rotor blades 22 along a chordal travel path within the housing 54. The flywheel 74 is coupled to a shaft 76 supported for rotation by bearings 88. The flywheel 74 is gearedly engaged with a first track gear 64 that may be mounted to the base 56, as shown in FIG. Figure 4 The track gear 64 extends longitudinally along the base 56 and effectively defines the travel length of the path within the spring mass damper 44. The flywheel 74 has a geared outer circumferential surface 78 that meshes with the track gear 64. Thus, as the mass member moves linearly back and forth along the track gear 64, the edge vibrations or oscillations induced in the rotor blades cause the flywheel 74 to rotate.

[0059] Although not shown, the flywheel 74 may also be in geared engagement with a second track gear mounted on the underside of the top 60 of the housing 54 .

[0060] In the depicted embodiment, the flywheel 74 is directly geared to the track gear 64 (which may include an additional upper track gear). It should be appreciated that an intermediate gear may be used between the flywheel 74 and the track gear 64.

[0061] In addition to the weight of the components on (including) the frame 72, the mass member 47 may also include additional ballast weight 93 that may be added to or removed from the frame 72, such as Figure 6 As described in the embodiments of the present invention.

[0062] The frame 72 may include a number of rollers 86 fixed thereto that ride along a bottom rail 58 mounted on (or integrally formed with) the base 56 and a top rail 62 supported by or formed on the top 60 of the housing 56. Side rollers 87 may be mounted on the frame 72 to roll along the side walls 68 of the housing 54. Thus, the frame 72 may be supported for direct rolling engagement with the housing 54 and the base 56 via the rollers 86, 87.

[0063] Counteracting torsion springs 90 are provided to oppose the back-and-forth movement of the frame 72 (and the attached members) relative to the track gears 64, 66, which also results in damping of blade vibrations and oscillations. One end of each spring 90 is fixed to the frame 72, and the other end of the spring 90 is fixed to the shaft 76. Therefore, when the shaft 76 rotates in either direction, it "tensions" one of the torsion springs 90 to generate an opposing force that resists the rotation of the shaft 76 (and therefore the rotation of the flywheel 74 fixed to the shaft 76). When the mass member 47 reverses direction on the track 64, the spring 90 begins to "relax" and therefore provides an acceleration force on the mass member 47 toward the opposite end of the track 64. The damping and acceleration force of the spring 90 is a function of the "stiffness" (i.e., the spring constant (k)) of the spring.

[0064] The motor 80 is mounted on the frame 72 and is in geared engagement (directly or indirectly) with the flywheel 74. For example, the motor 80 may be in direct geared engagement with the outer circumferential surface 78 of the flywheel 74. In the depicted embodiment, the motor is driven by a gear 84, which is also in geared engagement with the outer circumferential surface 78 of the flywheel 74.

[0065] In the particular embodiment depicted in the figure, the electric machine 80 is a motor-generator 82. More particularly, the motor-generator 82 can be a DC motor that operates in either a motor mode or a generator mode depending on the current passing through the machine. A suitable DC motor for this application is the RE50 DC motor (200 watts) from Maxon Motors. The motor-generator 82 is geared (directly or indirectly) with the flywheel 74 and is driven by the flywheel 74.

[0066] Reference Figure 7 The operating principle of the electric machine 80 (motor-generator 82) is explained. The operating theory of the electric machine 80 is similar to the operating theory of the regenerative braking system known and understood by those skilled in the art. When the rotor blade vibrates or oscillates, the mass member 47 of the spring mass damper 44 moves back and forth along the track 64 in the travel path. The travel path has a maximum length (SL ) defined by the length of the track 64. max ). The length of the travel path corresponds to the amplitude of the blade vibration, while the frequency of the back and forth motion of the mass member 47 corresponds to the vibration frequency of the blade. The mass member 47 decelerates as it approaches the end of its travel path. This deceleration causes the motor to "overspeed" and become a generator, wherein the energy generated by the generator is stored in the battery 124 (i.e., the current generated by the generator charges the battery 124). The spring mass damper 44 utilizes this generator aspect of the motor in a "virtual damper mode" 130 of operation.

[0067] A characteristic of a generator is that the current from the generator produces a reaction torque (anti-torque) that is proportional to the magnitude of the current at a given load on the generator (e.g., a battery). Torque control of the generator works by varying the effective load placed on the generator (e.g., in this case, the charging rate of the battery). A higher charging rate on the battery corresponds to more current from the generator, and a proportionally greater anti-torque / damping capacity of the spring-mass damper 44. Likewise, a lower charging rate corresponds to less current from the generator, and a proportionally lower anti-torque / damping capacity of the spring-mass damper 44. Controlling the component of the generator current that is proportional to the speed of the spring-mass damper effectively and automatically tunes the damping of the spring-mass damper 44. This principle is utilized in the present invention to provide a remote electrically tuned damper capability for the spring-mass damper 44 (i.e., the virtual damper 130).

[0068] Still refer to Figure 6 , the mass member 47 has an effective stroke length in the chord-wise direction across the blade, wherein relatively low amplitude blade vibrations or oscillations result in a shorter stroke (a shorter path of travel of the frame 72 on the track gear 64), and relatively large amplitude vibrations or oscillations result in a longer stroke of the mass member 47. As discussed above, tuning the spring mass damper 44 with respect to stroke length is achieved by controlling the motor-generator 82 in the virtual damper mode 130. Tuning the device to limit the travel (i.e., stroke length) at higher vibration / oscillation amplitudes is an important safety feature so that the travel of the mass member 47 does not exceed the maximum stroke path / length defined by the track 64 in the spring mass damper 44. On the other hand, it is desirable to tune the spring mass damper 44 to maximize its performance at lower amplitudes. Therefore, the tuning scheme is intended to increase the stroke at lower amplitudes to maximize the performance of the spring mass damper 44, while limiting the stroke at higher amplitudes to avoid damage to the spring mass damper 44. Thus, depending on the amplitude of vibrations / oscillations induced in the rotor blades by the operating conditions experienced by the wind turbine, a desired stroke length is set or defined for the spring mass damper 44 to reduce the amplitude of the vibrations.

[0069] The mass member 47 (including the spring 90) is selected so that the resonant frequency of the spring mass damper 44 is "hard-wired" to the expected VIV frequency of the wind turbine blade 22. However, the VIV effect can occur at different strengths and resonant frequencies, depending on the strength and direction of the gusts. Therefore, automatic adjustment of the spring mass damper for different VIV frequencies is desirable and provided by the present spring mass damper 44.

[0070] Still refer to Figure 7, when the mass member 47 stops at the end of the travel path and reverses direction, the physical spring pulls the mass back to the center of the spring mass damper, releasing the stored energy. In addition, as the mass passes the center of the spring mass damper, the spring provides a restoring force that stores the kinetic energy of the mass. This spring behavior can be replicated by an electric motor and a battery. When the mass member stops and reverses direction, the electric motor can act as a motor to accelerate the mass. Conversely, when the mass member passes the center of the spring mass damper, the electric motor changes to a generator mode, absorbing the energy of the mass. This effect is produced by controlling the component of the current in the motor that is proportional to the position of the spring mass damper. Ideally, there is no net energy exchange between the motor and the mass member, similar to a physical spring; in a real system, the electrical losses that occur due to the current flow originate from the battery or "virtual damper mode". The spring mass damper 44 utilizes this motor-generator aspect of the electric motor 80 in the "virtual spring mode" 128 of operation. By controlling the virtual spring mode 128 , the spring mass damper 44 may be electronically and automatically tuned to any resonant frequency of blade vibrations excited by the VIV.

[0071] It should be appreciated that the electric machine 80 may be operated simultaneously in the virtual damper mode 130 (where energy is generated and stored in the battery 124 ) and the virtual spring mode 128 (where energy is charged and discharged from the battery 124 ).

[0072] like Figure 7 As reflected in FIG. 1 , control of the motor-generator in the virtual damper mode 130 and the virtual spring mode 128 is via the controller 100 and the inverter 126 , wherein the inverter 126 converts DC power from the battery to AC power during motor operation and converts AC power from the generator to DC power stored by the battery 124 during the generator operation mode 130 .

[0073] Figure 8 An embodiment is depicted for tuning the spring mass damper 44 in a virtual damper mode 130 and a virtual spring mode 128. The tuning function may be performed by the controller 100 discussed above.

[0074] exist Figure 8 As discussed, the purpose of the tunable damping is to tune the stroke length of the mass member with respect to the vibration amplitude and to ensure that the displacement of the mechanism along the stroke path does not exceed the displacement of the track gear 64 ( Figure 7 ) corresponds to the command stroke length (SL cmd One or more sensors 92 (discussed below) determine the position (x) of the mass member 47 along the track 64 and calculate the actual peak amplitude of the mass member 47 and compare it to the commanded stroke length (SL cmd) to generate an error signal which is assigned a negative value and sent to a proportional integral control (PI control). The signal from the PI control is multiplied by the mechanism velocity, effectively making the output from the PI control an electronically controlled damping parameter that is sent to the summing point. Thus, the damping is tuned until the desired mechanism displacement is achieved.

[0075] exist Figure 8 In the virtual spring member of , the electronic spring is essentially created by adjusting the virtual spring stiffness and multiplying it by the position of the mass member. The control goal of the virtual spring tuning is to ensure that the resonant frequency of the mechanism matches the active VIV blade frequency. To detect this condition, the position (x) of the mass member relative to the blade is measured by sensor 92, thereby determining the frequency of the mass member 47. The spatial position of the acceleration of the blade is measured by blade sensor 94 (e.g., accelerometer), thereby determining the blade frequency. When there is an exact ninety degree phase shift from the blade acceleration to the mass member displacement, the frequencies of the blade and mass member are aligned. An alternative way to look at this statement is that if the blade acceleration signal is all in the "real" axis (cosine), then at the resonant frequency, the mass member displacement should all appear in the "imaginary" axis (sine). This means that under this condition, any cosine component of the mass member displacement will be zero. In practice, the virtual spring stiffness is adjusted by integral (I) control until this condition is achieved. To detect this condition, a single-phase second-order generalized integration algorithm with an embedded frequency-locked loop is used to synthesize a tracking signal (θ) aligned with the blade acceleration. attach ). A cosine is generated from this tracking signal, multiplied by the position of the mass member (x), and pushed to the I control. The algorithm acts as a gradient descent cosine transform that modifies the virtual spring parameters until the "real" component of x is driven to zero, at which point the spring mass damper resonant frequency is tuned to the VIV blade frequency.

[0076] The signal from I control is multiplied by the negative value of the position (x) of the mass member and passed to the summing point and combined with the damping parameter signal discussed above to generate a current command signal (I cmd The current control is performed by a power electronic inverter 126 with current sensor feedback ( Figure 7 ) provides closed-loop proportional-integral (PI) control of the motor windings, where V ac-dc 1 represents the command voltage from the controller 100 , which is implemented by the inverter for control of the motor in the virtual damper mode 130 and the virtual spring mode 128 .

[0077] exist Figure 4 and 5aIn the embodiment of the spring mass damper 44 depicted in FIG. 5c, a single motor 82 is utilized to provide the tunability. It should be appreciated that multiple motors 82 may be utilized to achieve the desired tunability within the constraints of the available space on the frame 72. For example, in Figure 6 In the embodiment depicted in , two motors 82 are engaged with the flywheel 74 , with both motors 82 communicating with a common controller 100 .

[0078] The controller 100 may be a dedicated onboard component of the spring mass damper 44. The controller 100 may have a dedicated power source, such as a rechargeable battery 102, or in alternative embodiments may be supplied with power from a source in the wind turbine.

[0079] Reference Figure 6 , a sensor array 92 is disposed on the frame 72 and is in communication with the controller 100. The array 92 may include one or more sensors. In a particular embodiment, three local sensors are configured in the array 92.

[0080] The first local sensor in the array 92 may be a position sensor configured to sense the instantaneous position of the mass member 47 along the track 64 to determine the current operating state of the spring mass damper 44. This sensor is the primary sensor used to provide feedback to the controller 100 for the tuning functions discussed above. This first sensor may be, for example, an incremental rotary encoder.

[0081] The second local sensor in the array 92 may be a neutral position sensor configured to provide a pulse (or other indication) at the neutral position of the mass member 47 corresponding to the middle of the travel path. This sensor may be used as a check to ensure that the first sensor (e.g., encoder) is aligned correctly. If the encoder is not consistent with the neutral position sensor, the encoder is reset to ensure the correct neutral position. The second sensor may be, for example, an inductive or Hall effect sensor on the moving frame 72, and a magnet on the base 56. When the sensor travels over the magnet, a pulse is generated.

[0082] The third local sensor in the array 92 may be an extreme position sensor, such as an inductive / Hall effect sensor. This sensor is located on the mass member 47 (e.g., on the frame 72) in a manner that does not respond to the neutral position sensor. The magnet for this third sensor is placed at the extreme of the travel path / length. If a pulse is detected from this sensor, action is taken to maximize the generator torque damping effect to counteract the motion because the moving frame is in danger of exceeding its designed travel.

[0083] The controller 100 may communicate with a remotely located central controller 112 (either directly or via the wind turbine controller 24) for receiving or exchanging control commands or data therewith. For example, the central controller 112 may generate control commands to change certain operating parameters of the spring mass damper 44, such as stroke length, response characteristics of the spring mass damper, power mode, etc. The controller 100 may communicate with a mobile handheld controller 116 (e.g., a mobile smart device) directly or via an intermediate controller. The mobile controller 116 may run an application that allows an operator to monitor the operation of the spring mass damper 44 and / or control its operating parameters. In the depicted embodiment, the mobile controller 116 and the central controller 112 may communicate directly with the spring mass damper controller 100 via a wireless network 120. In this case, the spring mass damper 44 would also include wireless transmission and reception capabilities.

[0084] Fig. 9 A control scheme is also depicted in which each rotor blade 22 of a wind turbine has one of the spring mass dampers 44 mounted thereon. Each damper 44 may have its own dedicated controller 100 that communicates with the wind turbine controller 24 via a wireless network 121 or a wired connection. The wind turbine controller 24 may in turn communicate with the central controller 112 via a wireless network 118. The mobile smart device 116 may communicate with the wind turbine controller 24 directly or via the central controller 112 (and wireless network 120).

[0085] It should be appreciated that various control schemes and architectures may be utilized to provide automatic tuning capabilities of the spring mass dampers 44 on the rotor blades 22 as well as remote adjustment or monitoring of operating states or parameters of the spring mass dampers 44 .

[0086] In certain embodiments, one or more sensors 95, 115 located on the blades 22 or other static locations of the wind turbine may be utilized to provide data indicative of vibrations or oscillations induced in the rotor blades during a locked or idling condition of the rotor 18. The oscillations or vibrations may be directly detected or measured by a displacement sensor 95 (e.g., an accelerometer or strain gauge) located directly on the rotor blades. The vibration of the blade may be determined when a strain or deformation parameter satisfies a strain or deformation threshold, which may be determined by the controller 100 (or any of the other controllers 112, 116).

[0087] The sensors 95, 115 may communicate with the central controller 112 directly or via the wind turbine controller 24, such as Fig. 9To conserve the internal power source (e.g., battery 102) in the spring mass damper 44, it may be desirable for the device 44 to be placed in a low power sleep mode until the vibrations or oscillations induced in the blades reach a threshold level as determined by the central controller 112 based on data from the sensors 95, 115. Once the threshold is met, the central controller 112 may issue an “on” command to the spring mass damper 44, either directly or via the wind turbine controller 24.

[0088] Alternatively, the oscillations or vibrations may be predicted or inferred based on data from sensors disposed on the wind turbine to measure wind speed, wind direction, yaw position of the rotor hub, etc. To this end, the wind turbine may include one or more wind parameter sensors 115 ( Figure 1 ) for measuring various wind parameters in the wind direction upwind of the wind turbine. (Multiple) actual wind parameters may be any one or a combination of the following: gusts, wind speed, wind direction, wind acceleration, wind turbulence, wind shear, wind turning, wake, wind upwelling, etc. In addition, one or more sensors 115 may include at least one lidar sensor for measuring upwind parameters. The lidar sensor may be located on the wind turbine tower 12, on one or more of the wind turbine blades 22, on the nacelle 16, on the meteorological mast of the wind turbine, or at any other suitable location. In some other embodiments, the wind parameter sensor 115 may be located at any suitable location near the wind turbine 10. The sensor 115 may be configured to measure wind parameters in front of at least one specific portion, which is typically the most important section of the blade 22 in terms of the contribution of those sections to the aerodynamic torque on the blade 22. These sections may include, for example, sections near the tip of the blade.

[0089] Further aspects of the invention are provided by the subject matter of the following clauses: Clause 1: A method for reducing vibrations and loads in blades on a rotor hub of a wind turbine when the rotor hub is in a locked or idling state, the method comprising: attaching an electronically tunable spring-mass damper at a fixed position on the blade during the locked or freewheeling condition of the rotor hub, the tunable spring-mass damper having a mass member that moves along a travel path; The spring mass damper comprises an electric machine operable as a motor or a generator; determining an amplitude and frequency of vibrations induced in said blade during said locked or idling condition; sensing movement of the mass member caused by the vibration induced in the blade; and Based on the sensed movement of the mass member, one or both of the following are performed: (a) automatically tuning the spring mass damper to the amplitude of the vibration by operating the motor as a generator in a virtual damper mode; or (b) automatically tuning the spring mass damper to the frequency of the vibration by operating the motor as a motor-generator in a virtual spring mode. Clause 2: A method according to clause 1, the method comprising performing both (a) and (b), wherein the spring mass damper includes a flywheel that is gear-engaged with the motor as the mass member moves along the travel path, wherein in the virtual damper mode, the motor generates a reaction torque on the flywheel when the spring mass damper approaches the end of the travel path and decelerates at the end of the travel path, and in the virtual spring mode, the motor generates an additional torque or reaction torque on the flywheel when the spring mass damper accelerates toward or away from the end of the travel path. Clause 3: The method of clause 1 or 2, wherein in the virtual damper mode, the electric machine operating as the generator charges a battery, and in the virtual spring mode, the electric machine operating as a motor-generator is powered by the battery. Clause 4: A method according to any one of clauses 1-3, wherein the flywheel is gear-engaged with a track gear extending along the travel path so that when the mass member moves along the travel path, the flywheel is rotationally driven, the flywheel is connected to a shaft, and the shaft is connected to the motor. Clause 5: The method of any of clauses 1-4, wherein the step of automatically tuning the spring mass damper is performed entirely by the spring mass damper without external operator or device action. Clause 6: The method of any of clauses 1-5, wherein the position or movement of the mass member along the travel path is continuously or periodically sensed using one or more sensors with respect to the spring mass damper configuration. Clause 7: The method of any of clauses 1-6, wherein the spring mass damper is operationally insensitive to temperature changes. Clause 8: The method of any of clauses 1-7, wherein the spring mass damper is in communication with a remote central controller, wherein at least one operating parameter of the spring mass damper is remotely adjusted by the remote central controller. Clause 9: A method according to any one of clauses 1-8, wherein the spring mass damper also communicates with a mobile smart device, and the mobile smart device communicates with the remote central controller, wherein an operator adjusts the operating parameters of the spring mass damper via the mobile smart device or via the remote central controller. Clause 10: The method of any of clauses 1-9, wherein each blade on the rotor hub is configured with one of the spring mass dampers, each of the spring mass dampers being in communication with a wind turbine controller, the wind turbine controller being in communication with the remote central controller. Clause 11: A wind turbine configured to reduce vibrations and loads in rotor blades during a non-operating mode of the wind turbine, comprising: a plurality of rotor blades on a rotor hub; in the non-operational mode of the wind turbine wherein the rotor hub is in a locked or idling state, the wind turbine further comprising a tunable spring-mass damper attached at a fixed position on one or more of the rotor blades, the spring-mass damper comprising a mass member movable along a travel path; one or more sensors configured with respect to the spring-mass damper to sense movement of the mass member along the travel path, wherein the movement is generated by vibrations or oscillations induced in the rotor blades during the locked or freewheeling condition of the rotor hub; The spring mass damper comprises an electric machine operable as a motor or a generator; and a controller constructed with respect to the spring-mass damper and configured to perform one or both of the following: (a) automatically tune the spring-mass damper to the amplitude of the vibration by operating the motor as a generator in a virtual damper mode based on the sensed movement of the mass member; or (b) automatically tune the spring-mass damper to the frequency of the vibration by operating the motor as a motor-generator in a virtual spring mode. Clause 12: The wind turbine of clause 11, wherein the spring mass damper is in communication with a remote central controller, wherein one or more operating parameters of the spring mass damper are remotely adjusted by the remote central controller. Clause 13: The wind turbine according to one of clauses 11-12, wherein the spring mass damper is also in communication with a mobile smart device, wherein an operator adjusts the operating parameters of the spring mass damper via the mobile smart device or via the remote central controller. Clause 14: The wind turbine of any of clauses 11-13, wherein each of the rotor blades is configured with one of the spring mass dampers, each of the spring mass dampers being in communication with the wind turbine controller, the wind turbine controller being in communication with the remote central controller. Clause 15: A wind turbine according to any of clauses 11-14, wherein the spring mass damper includes a flywheel, which is geared with the motor when the mass member moves along the travel path, wherein in the virtual damper mode, when the spring mass damper decelerates toward the end of the travel path, the motor generates a counter-torque to the flywheel, and in the virtual spring mode, when the spring mass damper accelerates toward or away from the end of the travel path, the motor generates an additional torque or counter-torque to the flywheel. Clause 16: A wind turbine according to any one of clauses 11-15, wherein the flywheel is geared with a track gear extending along the travel path so that the flywheel is rotationally driven when the mass member moves along the travel path, the flywheel is connected to a shaft, and the shaft is connected to the motor. Clause 17: A wind turbine according to any of clauses 11-16, wherein the spring mass damper further comprises a battery, wherein in the virtual damper mode, the electric machine operates as a generator and charges the battery, and in the virtual spring mode, the electric machine operates as a motor-generator and is powered by the battery. Clause 18: A system for reducing vibrations and loads in a rotor blade of a wind turbine during a non-operating mode of the wind turbine, wherein the rotor hub of the wind turbine is in a locked or idling state, the system comprising: a tunable spring-mass damper configured for attachment at a fixed location on one or more of the rotor blades, the spring-mass damper comprising a mass member movable along a travel path; one or more sensors configured with respect to the spring-mass damper to sense movement of the mass member along the travel path, wherein the movement is generated by vibrations or oscillations induced in the rotor blades during the locked or freewheeling condition of the rotor hub; The spring mass damper comprises an electric machine operable as a motor or a generator; and a controller constructed with respect to the spring-mass damper and configured to perform one or both of the following: (a) automatically tune the spring-mass damper to the amplitude of the vibration by operating the motor as a generator in a virtual damper mode based on the sensed movement of the mass member; or (b) automatically tune the spring-mass damper to the frequency of the vibration by operating the motor as a motor-generator in a virtual spring mode. Clause 19: A system according to clause 18, wherein the spring mass damper includes a flywheel, and the flywheel is gear-engaged with the motor when the mass member moves along the travel path, wherein in the virtual damper mode, the motor generates a counter-torque to the flywheel when the spring mass damper decelerates toward the end of the travel path, and in the virtual spring mode, the motor generates an additional torque or counter-torque to the flywheel when the spring mass damper accelerates toward or away from the end of the travel path, and wherein the flywheel is gear-engaged with a track gear extending along the travel path so that the flywheel is rotationally driven when the mass member moves along the travel path, and the flywheel is connected to a shaft, and the shaft is connected to the motor. Clause 20: A system according to any of clauses 18-19, wherein the spring mass damper also includes a battery, wherein in the virtual damper mode, the motor operates as a generator and charges the battery, and in the virtual spring mode, the motor operates as a motor-generator and is powered by the battery.

[0090] This written description uses examples to disclose the invention, including the best mode, and also to enable those skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. If such other examples include structural elements that do not differ from the literal language of the claims, or if such other examples include equivalent structural elements that do not differ significantly from the literal language of the claims, such other examples are intended to be within the scope of the claims.

Claims

1. A method for reducing vibrations and loads in blades on a rotor hub of a wind turbine when the rotor hub is in a locked or idling state, the method comprising: attaching an electronically tunable spring-mass damper at a fixed position on the blade during the locked or freewheeling condition of the rotor hub, the tunable spring-mass damper having a mass member that moves along a travel path; The spring mass damper comprises an electric machine operable as a motor or a generator; determining an amplitude and frequency of vibrations induced in said blade during said locked or idling condition; sensing movement of the mass member caused by the vibration induced in the blade; as well as Based on the sensed movement of the mass member, one or both of the following are performed: (a) automatically tuning the spring mass damper to the amplitude of the vibration by operating the motor as a generator in a virtual damper mode; or (b) automatically tuning the spring mass damper to the frequency of the vibration by operating the motor as a motor-generator in a virtual spring mode.

2. The method of claim 1, comprising performing both (a) and (b), wherein: The spring mass damper includes a flywheel in geared engagement with the motor as the mass member moves along the travel path, wherein in the virtual damper mode, the motor generates a reaction torque on the flywheel as the spring mass damper approaches the end of the travel path and decelerates at the end of the travel path, and in the virtual spring mode, the motor generates an additional torque or reaction torque on the flywheel as the spring mass damper accelerates away from the end of the travel path.

3. The method according to claim 2, wherein: In the virtual damper mode, the electric machine operating as the generator charges a battery, and in the virtual spring mode, the electric machine operating as a motor-generator is powered by the battery.

4. The method according to claim 2, wherein: The flywheel is in geared engagement with a track gear extending along the travel path so that the flywheel is rotationally driven when the mass member moves along the travel path, the flywheel being coupled to a shaft coupled to the motor.

5. The method according to claim 1, wherein: The step of automatically tuning the spring mass damper is performed entirely by the spring mass damper without requiring external operator or device action.

6. The method according to claim 1, wherein: The position or movement of the mass member along the travel path is continuously or periodically sensed using one or more sensors in relation to the spring-mass-damper configuration.

7. The method according to claim 1, wherein: The spring mass damper is operationally insensitive to temperature changes.

8. The method according to claim 1, wherein: The spring mass damper is in communication with a remote central controller, wherein at least one operating parameter of the spring mass damper is remotely adjusted by the remote central controller.

9. The method according to claim 8, wherein: The spring mass damper is also in communication with a mobile smart device, which is in communication with the remote central controller, wherein an operator adjusts the operating parameters of the spring mass damper via the mobile smart device or via the remote central controller.

10. The method according to claim 8, wherein: Each blade on the rotor hub is configured with one of the spring mass dampers, each of the spring mass dampers is in communication with a wind turbine controller, which is in communication with the remote central controller.

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