DK178160B1

DK178160B1 - System and method for detecting and controlling rotor blade deflection

Info

Publication number: DK178160B1
Application number: DK201170531A
Authority: DK
Inventors: Jiajuan Zhang; Xiongzhe Huang; Roelant Van Der Bos; Wei Xiong; Danian Zheng
Original assignee: Gen Electric
Priority date: 2010-09-30
Filing date: 2011-09-26
Publication date: 2015-07-06
Also published as: CN102445339A; DE102011053893A1; DK201170531A

Abstract

A system for detecting the deflection of a rotor blade coupled to a hub of a wind turbine rotor is diselosed. In general, the system includes a cable at least partially extending substantially adjacent to a tip of the rotor blade. The cable may include a first end secured to the rotor blade or the hub and a second end coupled to a tensioning device. The cable may also be attached to at least one interior wall of the rotor blade between its ends such that the cable is displaced relative to the rotor blade as the blade deflects. The tensioning device may be secured to the rotor blade or the hub and may be configured to maintain a predetermined tension within the cable. Additionally, a sensor may be coupled to at least one of the cable or the tensioning device and may be configured to measure the displacement of the cable.

Description

SYSTEM AND METHOD FOR DETECTING AND CONTROLLING ROTOR

BLADE DEFLECTION

FIELD OF THE INVENTION

[0001] The present subject matter relates generally to wind turbines and particularly to rotor blade deflection. More particularly, the present subject matter relates to a system and method for detecting and controlling rotor blade deflection during operation of a wind turbine.

BACKGROUND OF THE INVENTION

[0002] Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modem wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known foil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.

[0003] To ensure that wind power remains a viable energy source, efforts have been made to increase energy outputs by modifying the size and capacity of wind turbines. One such modification has been to increase the length of the rotor blades. However, the magnitude of deflection of a rotor blade is generally a function of blade length, along with wind speed, turbine operating states and blade stiffness. Thus, longer rotor blades are typically subject to increased deflection forces and loading, particularly when a wind turbine is operating in high-speed wind conditions. This increased loading not only produces fatigue on the rotor blades and other wind turbine components but may also increase the risk of the rotor blades striking the tower. A tower strike can significantly damage a rotor blade and the tower and, in some instances, can even bring down the entire wind turbine. As such, a tower strike may result in considerable downtime to repair or replace damaged components.

[0004] Accordingly, there is a need for a system and method for detecting and controlling rotor blade deflection.

BRIEF DESCRIPTION OF THE INVENTION

[0005] 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.

[0006] In one aspect, the present subject matter includes a system for detecting the deflection of a rotor blade coupled to a hub of a wind turbine rotor. In general, the system includes a cable at least partially extending substantially adjacent to a tip of the rotor blade. The cable may include a first end fixed to the rotor blade or the hub and a second end coupled to a tensioning device. The cable may also be attached to at least one interior wall of the rotor blade between its first and second ends such that the cable is displaced relative to the rotor blade as the blade deflects. The tensioning device may also be secured to the rotor blade or the hub and may be configured to maintain a predetermined tension within the cable. Additionally, a sensor may be coupled to at least one of the cable or the tensioning device and may be configured to measure the displacement of the cable.

[0007] In another aspect, the present subject matter includes a method for detecting and controlling the deflection of a rotor blade of a wind turbine. The method may generally include measuring the displacement of at least one cable movably attached to an interior wall of the rotor blade as the rotor blade deflects, analyzing the displacement measurement to determine an operating parameter of the rotor blade and performing a corrective action when the operating parameter of the rotor blade exceeds a predetermined reference point.

[0008] 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 invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWING

[0009] A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

[0010] FIG. 1 illustrates a perspective view of a wind turbine;

[0011] FIG. 2 illustrates a perspective view of a rotor blade;

[0012] FIG. 3 illustrates a cross-sectional edge view of a rotor blade having an embodiment of a system for detecting the deflection of a rotor blade installed therein in accordance with aspects of the present subject matter, particularly illustrating the rotor blade in a neutral or non-deflected state;

[0013] FIG. 4 illustrates a cross-sectional edge view of a rotor blade including the embodiment of the system depicted in FIG. 3, particularly illustrating the rotor blade in a deflected state;

[0014] FIG. 5 illustrates a cross-sectional edge view of a rotor blade having another embodiment of a system for detecting the deflection of a rotor blade installed therein in accordance with aspects of the present subject matter, particularly illustrating the rotor blade in a deflected state;

[0015] FIG. 6 illustrates a cross-sectional edge view of a rotor blade having a further embodiment of a system for detecting the deflection of a rotor blade installed therein in accordance with aspects of the present subject matter, particularly illustrating the rotor blade in a deflected state;

[0016] FIG. 7 illustrates a cross-sectional view of a rotor blade including a plurality of cables attached thereto in accordance with aspects of the present subject matter; and,

[0017] FIG. 8 illustrates a flow diagram of one embodiment of a method for detecting and controlling the deflection of a rotor blade in accordance with aspects of the present subject matter.

DETAIFED DESCRIPTION OF THE INVENTION

[0018] Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

[0019] Referring to the drawings, FIG. 1 illustrates a perspective view of a wind turbine 10. As shown, the wind turbine 10 is a horizontal-axis wind turbine.

However, it should be appreciated that the wind turbine 10 may be a vertical-axis wind turbine. In the illustrated embodiment, the wind turbine 10 includes a tower 12 that extends from a support surface 14, a nacelle 16 mounted on the tower 12, and a rotor 18 that is coupled to the nacelle 16. The rotor 18 includes a rotatable hub 20 and at least one rotor blade 22 coupled to and extending outward from the hub 20. As shown, the rotor 18 includes three rotor blades 22. However, in an alternative embodiment, the rotor 18 may include more or less than three rotor blades 22. Additionally, in the illustrated embodiment, the tower 12 is fabricated from tubular steel to define a cavity (not illustrated) between the support surface 14 and the nacelle 16. In an alternative embodiment, the tower 12 may be any suitable type of tower having any suitable height.

[0020] The rotor blades 22 may generally have any suitable length that enables the wind turbine 10 to function as described herein. For example, in one embodiment, the rotor blades 22 may have a length ranging from about 15 meters (m) to about 91 m. However, other non-limiting examples of blade lengths may include 10 m or less, 20 m, 37 m or a length that is greater than 91m. Additionally, the rotor blades 22 may be spaced about the hub 20 to facilitate rotating the rotor 18 to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. Specifically, the hub 20 may be rotatably coupled to an electric generator (not illustrated) positioned within the nacelle 16 to permit electrical energy to be produced. Further, the rotor blades 22 may be mated to the hub 20 by coupling a blade root portion 24 to the hub 20 at a plurality of load transfer regions 26. Thus, any loads induced to the rotor blades 22 are transferred to the hub 20 via the load transfer regions 26.

[0021] As shown in the illustrated embodiment, the wind turbine may also include a turbine control system or turbine controller 36 centralized within the nacelle 16. However, it should be appreciated that the controller 36 may be disposed at any location on or in the wind turbine 10, at any location on the support surface 14 or generally at any other location. The controller 36 may include suitable processors and/or other processing functionality configured to perform the methods, steps, operations, calculations and the like described herein. For example, in one embodiment, the controller 36 may be configured as a computer or other central processing unit. However, it should appreciated that, as used herein, the term “processor” need not limited to integrated circuits referred to in the art as being included in a computer, but broadly refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. It should be understood that the turbine controller 36 may also include memory, including, but not limited to, computer readable medium (e.g., random access memory (RAM), computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and/or other suitable memory elements. Such memory may be configured to store suitable computer-readable instructions that, when implemented by the processors of the controller, configure the controller to perform various different calculations and analyses and/or configure the controller to execute wind turbine control commands, such as corrective actions and the like. Further, the controller 36 may also include various input/output channels and/or devices for receiving inputs from sensors and other measurement devices and for sending control signals to various components of the wind turbine.

[0022] By executing wind turbine control commands, the controller 36 may generally be configured to control the various operating modes of the wind turbine 10 (e.g., start-up or shut-down sequences). The controller 36 may also be configured to control the blade pitch or pitch angle of each of the rotor blades 22 (i.e., an angle that determines a perspective of the rotor blades 22 with respect to the direction 28 of the wind) to control the load and power generated by the wind turbine 10 by adjusting an angular position of at least one rotor blade 22 relative to the wind. For instance, the controller 36 may control the pitch angle of the rotor blades 22, either individually or simultaneously, by transmitting suitable control signals to a pitch drive or pitch adjustment system 32. Specifically, the rotor blades 22 may be rotatably mounted to the hub 20 by one or more pitch bearing(s) (not illustrated) such that the pitch angle may be adjusted by rotating the rotor blades 22 along their longitudinal axes 34 using the pitch adjustment system 32. Further, as the direction 28 of the wind changes, the controller 36 may be configured to control a yaw direction of the nacelle 16 about a yaw axis 38 to position the rotor blades 22 with respect to the direction 28 of the wind. For example, the controller 36 may be configured to transmit control signals to a yaw drive mechanism (not illustrated) of the nacelle 16 such that the nacelle 16 may be rotated about the yaw axis 38.

[0023] During operation of the wind turbine 10, wind strikes the rotor blades 22 from a direction 28, which causes the rotor 18 to rotate about an axis of rotation 30.

As the rotor blades 22 are rotated and subjected to centrifugal forces, the rotor blades 22 are also subjected to various forces and bending moments. As such, the rotor blades 22 may deflect from a neutral, or non-deflected, position to a deflected position. For example, as shown in FIG. 1, the non-deflected blade clearance 40 represents the distance between the rotor blades 22 and the tower 12 when the blades 22 are in a non-deflected position. However, the forces and bending moments acting on the rotor blades 22 may cause the blades 22 to deflect towards the tower 12, reducing the overall blade clearance 40. As aerodynamic loads increase, excessive forces and bending moments can cause one or more of the rotor blades 22 to strike the tower 12 resulting in significant damage and downtime. However, even without a tower strike, excessive loading and bending moments can cause significant fatigue on the rotor blades 22 and other wind turbine components.

[0024] Referring now to FIG. 2, a perspective view of a rotor blade 22 is illustrated. As shown, the rotor blade 22 includes a root portion 24 used to mount the rotor blade 22 to the hub 20 (FIG. 1). The rotor blade 22 also includes a blade tip 42 disposed opposite the root portion 24. A blade body or shell 44 generally extends along a longitudinal axis 46 between the root portion 24 and the blade tip 42 and defines a leading edge 48 and a trailing edge 50 of the rotor blade 22. Additionally, as is generally understood, the rotor blade 22 may include a windward or high pressure side 52 and a leeward or low pressure/suction side 54.

[0025] Referring now to FIGS. 3-7, various embodiments of a system for detecting the blade deflection of a rotor blade are illustrated in accordance with aspects of the present subject matter. In general, the system may include at least one cable extending at least partially within the rotor blade and having ends secured directly or indirectly to portions of the wind turbine rotor, such as to a portion of the hub or a portion of the rotor blade. The system may also include a tensioning device secured to a portion of the wind turbine rotor. The tensioning device may generally be configured to maintain a predetermined tension within the cable. Further, the system may also include a sensor configured to measure the displacement of the cable as the rotor blade deflects.

[0026] Referring particularly to FIGS. 3 and 4, there is illustrated one embodiment of a system 300 for detecting the deflection of a rotor blade 22 mounted to a hub 20 of a wind turbine rotor 18 (FIG. 1). Specifically, FIG. 3 illustrates a cross-sectional edge view of the rotor blade 22 in a neutral or non-deflected state with the system 300 installed therein. Similarly, FIG. 4 illustrates a cross-sectional edge view of the rotor blade 22 in a deflected state with the system 300 installed therein.

[0027] As shown in FIGS. 3 and 4, in one embodiment, the illustrated system 300 may include a first cable 302 disposed on the pressure side 52 of the rotor blade 22 and a second cable 304 disposed on the suction side 54 of the rotor blade 22. The cables 302, 304 may generally comprise any suitable cable, string and/or wire known in the art which is configured to function as described herein. For example, in one embodiment, the cables 302, 304 may comprise one of variety of different metal cables, such as stainless steel cables or coated steel cables (e.g., nylon coated stainless steel cables). Alternatively, the cables 302, 304 may comprise polymer or thermoplastic cables. In even further embodiments, the cables 302, 304 may comprise a fiber reinforced cable, such as a carbon-reinforced polymer cable.

[0028] Each of the cables 302, 304 may include a first end 306, 307 and a second end 308, 309. The first end 306, 307 of each cable 302, 304 may generally be fixed or secured to the rotor blade 22 in a location substantially adjacent to the tip 42 of the blade 22. Accordingly, as the blade tip 42 is deflected relative to the non-deflected longitudinal axis 46 of the rotor blade 22, the ends 306, 307 may be correspondingly displaced. Thus, as shown in FIGS, 3 and 4, the first end 306, 307 of each cable 302, 304 may be secured to interior walls 310, 312 of the rotor blade 22 substantially adjacent to the blade tip 42. It should be appreciated that, although the ends 306, 307 are shown as being secured to the rotor blade 22 at differing locations (e.g., on the interior wall 310 of the pressure side 52 and the interior wall 312 of the suction side 54), the first ends 306, 307 may also be secured to the rotor blade 22 at substantially the same location, such as directly at the tip 42. Additionally, in an alternative embodiment, the cables 302, 304 may extend through the rotor blade 22 at one or more locations substantially adjacent to the tip 42 such that the ends 306, 307 may be secured to an exterior portion of the rotor blade 22. Such an embodiment may be desirable to permit the tension in each of the cables 302, 304 to be adjusted from a location outside the rotor blade 22. Additionally, it should be appreciated that the first ends 306, 307 may be secured to the rotor blade 22 using any suitable means, such as by using clamping mechanisms, clips or any other fasteners generally known in the art.

[0029] Still referring to FIGS. 3 and 4, the second ends 308, 309 of the cables 302, 304 may generally be coupled to tensioning devices 314 configured to maintain substantially the same amount of tension within the cables 302, 304 as the rotor blade 22 deflects during operation of the wind turbine. In general, the tensioning devices 314 may be secured to any portion of the wind turbine rotor 18 (FIG. 1). For example, as shown in FIGS. 3 and 4, each tensioning device 314 may be secured to the rotor blade 22 at a location substantially adjacent to the root portion 24 of the blade 22, such as substantially adjacent to the pitch bearing (not illustrated). Alternatively, as shown in FIG. 5, the tensioning device 508 may be secured to a portion of the hub 20, such as on or adjacent to the blade entrance door (not illustrated) or at any other suitable location within the hub 20.

[0030] In general, the tensioning devices 314 may comprise any suitable device known in the art which is configured to maintain a predetermined tension between the ends of a cable, wire, string or any other elongated tension-carrying member. In one embodiment, the tensioning devices 314 may be configured to maintain a predetermined minimum tension within the cables 302, 304 such that the displacement of the cables may provide an accurate representation of the deflection of the rotor blade. In various embodiments, the tensioning device 314 may comprise a device or mechanism utilizing draw wire mechanics or similar technology in order to maintain the tension within an attached cable. Thus, suitable tensioning devices 314 may include draw wire devices, spring-loaded cable tensioners and any other automatic winding mechanisms known in the art. For instance, in a particular embodiment, each tensioning device 314 may include a spring-loaded drum or spool around which the second end 308, 309 of each the cables 302, 304 is wound. As such, when the first end 306, 307 of each cable 302, 304 is displaced relative to the tensioning devices 314 due to deflection of the tip 42 of the rotor blade 22, the tensioning devices 314 may be configured such that a portion of each cable 302, 304 winds around or unwinds from the spring-loaded drum or spool so as to maintain tension within the cables 302, 304. Accordingly, the tensioning device 314 may generally permit the portion of each cable 302, 304 extending between the first end 306, 307 and the tensioning device 314 to be lengthened/shortened or otherwise displaced as the rotor blade 22 deflects.

[0031] The cables 302, 304 may also be attached substantially adjacent to the interior walls 310, 312 of the rotor blade 22 between the first and second ends 306, 307, 308, 309 such that the cables 302, 304 are movable or may otherwise be displaced relative to the rotor blade 22. Thus as shown in FIGS. 3 and 4, the first cable 302 may be movably attached to an interior wall 310 of the pressure side 52 of the rotor blade 22 and the second cable 304 may be movably attached to an interior wall 312 of the suction side 54 of the rotor blade 22. It should be appreciated that, by movably attaching the cables 302, 304 substantially adjacent to the interior walls 310, 312, the displacement of the cables 302, 304 may generally constitute a relatively accurate representation of the degree of blade deflection of the rotor blade 22 occurring during operation of the wind turbine.

[0032] To permit such attachment of the cables 302, 304, it should be appreciated that the system of the present subject matter may include means for attaching the cables 302, 304 to the interior walls 310, 312 of the rotor blade 22. In general, the means for attaching the cables 302, 304 may include any known mounting device and/or mounting configuration that permits the cables 302, 304 to slide, move and/or otherwise be displaced relative to the rotor blade 22 as the rotor blade 22 deflects. Thus, as shown in the embodiment illustrated in FIGS. 3 and 4, the means for attaching the cables 302, 304 may comprise a plurality of guide supports 316 secured to the interior walls 310, 312 which are configured to support the cables 302, 304 at various locations along the walls 310, 312. For example, suitable guide supports 316 may include guide rings, pulleys, eyelets, hooks, brackets and any other suitable mounting devices which are configured to support the cables 302, 304 along the interior walls 310, 312 and also permit the cables 302, 304 to be displaced relative to the rotor blade 22. Alternatively, the means for attaching the cables 302, 304 may comprise one or more elongated cable supports 510 (FIG. 5) configured to support the cables 302, 304 substantially adjacent to the interior walls 310, 312 along a particular length. Such elongated cable supports 510 may generally comprise any elongated member having a longitudinally defined opening, channel, recess or similar aperture into which the cables 302, 304 may be inserted and movably supported. For example, in several embodiments, suitable elongated cable supports 510 may include tubes, pipes and/or cable guides secured along a length of the interior walls 310, 312. In a further embodiment, the means for attaching the cables 302, 304 may include one or more channels defined in the rotor blade 22, itself, into which the cables 302, 304 may be inserted and movably supported. Various other suitable mounting devices and/or configurations that may be utilized to movably attach the cables 302, 304 to the interior walls 310, 312 of the rotor blade 22 should be apparent to those of ordinary skill in the art.

[0033] Referring still to FIGS. 3 and 4, the system 300 may also include one or more sensors 318 configured to measure the displacement of each cable 302, 304 as the rotor blade 22 is deflected. The sensors 318 may generally comprise a length gauge or any other sensor known in the art for directly or indirectly measuring the linear displacement of an object. Thus, in several embodiments, suitable sensors 318 for use within the scope of the present subject matter may include displacement transducers, linear encoders, string pot sensors, draw wire sensors, yoyo pot sensors, linear potentiometers and linear length sensors. The disclosed sensors 318 may also be configured to convert any measurements taken into to electronic signals which can be transmitted to the wind turbine controller 36 (FIG. 1), via any suitable wired or wireless connection, such that the measurements can be analyzed in order to determine rotor blade deflection, which will be described in greater detail below.

[0034] To facilitate the measurement of the cable displacements, it should be appreciated that, in several embodiments, the sensors 318 may be coupled to the cables 302, 304 and/or the tensioning device 314. For example, as shown in FIGS. 3 and 4, in embodiments in which the tensioning devices 314 are configured as draw wire devices or any other automatic winding mechanisms, the sensors 318 may be directly coupled to each tensioning device 314 so that the linear displacement of each cable 302, 304 may be measured by detecting or otherwise sensing the rotation of the tensioning devices 314 as the cables 302, 304 are wound thereon or unwound therefrom. As such, it should be appreciated that the sensors 318 may generally be configured as any draw wire sensor or similar sensor known in the art. Alternatively, as shown in FIG. 6, the sensors 614 may be connected to each cable 602, 604, such as a through a secondary cable or other suitable connective member 616, so that the linear displacement of the cables 602, 604 may be measured.

[0035] Referring more particularly to FIG. 4, the operation of the disclosed system 300 will be generally described. As the rotor blade 22 deflects during operation of the wind turbine, the tip 42 of the blade 22 is displaced a deflection distance 320 relative to its typical non-deflected longitudinal axis 46. For example, it is often the case that the rotor blade 22 is deflected in the direction of the tower 12 (FIG. 1) of the wind turbine (i.e., in the direction of the suction side 54 of the rotor blade 22). As such, the first and second cables 302, 304, being secured at their first end 306, 307 substantially adjacent to the tip 42, are also displaced respective distances 322, 324 in relation to the total deflection of the rotor blade 22. In particular, the first cable 302, being attached to the pressure side 52 of the rotor blade 22, may be elongated or pulled away from the tensioning device 314 a displacement distance 322 as the blade 22 is deflected in the direction of the suction side 54. For example, in one embodiment, a portion of the cable 302 may be unwound from the tensioning device 314 as the cable 302 displaces in response to the deflection. Similarly, the second cable 304, being disposed on the suction side 52 of the rotor blade 22, may be shortened or drawn into the tensioning device 314 a displacement distance 324 as the rotor blade 22 deflects. Thus, in the particular embodiment of FIGS. 3 and 4, a portion of the cable 304 may be wound around the tensioning device 314 as a result of the rotor blade 22 deflecting. Of course, it should be appreciated that, depending on the configuration of the rotor blade 22 and the relative positioning of the cables 302, 304 and tensioning devices 314, the displacement distance 322 of the first cable 302 may be equal to or may differ from the displacement distance 324 of the second cable 304.

[0036] Still referring to FIG. 4, as each of the cables 302, 304 are displaced, the sensors 318 measure their linear displacement (i.e., distances 322, 324), so that such measurements may then be utilized to estimate and/or calculate the deflection distance 320. For example, the sensors 318 may be configured to transmit the displacement measurements to the turbine controller 36 (FIG. 1) via a wired or wireless connection so that the measurements can be analyzed by the controller 36. Thus, in one embodiment, the turbine controller 36 may be provided with suitable computer-readable instructions that, when executed, enable the controller 36 to correlate the displacement measurements to the deflection distance 320 using any suitable mathematical expression and/or model stored within the controller’s memory. The development of such a mathematical expression and/model is within the capability of those skilled in the art, and therefore will not be discussed in any detail herein. However, in general, it should be appreciated that the mathematical expression and/or model may take into account one or more of a plurality of different factors including, but not limited to, the distance between the blade tip 42 and the tensioning devices 314 and/or the sensors 318, the distance between the center line of the cables 302, 304 and the interior walls 310, 312 of the rotor blade 22, the total length of the rotor blade 22 and the length of the cables 302, 304. In alternative embodiment, the turbine controller 36 may be programmed with one or more look-up tables correlating the displacement measurements to the deflection distance 320 of the rotor blade 22.

[0037] It should be appreciated that, although the system 300 was generally described above as including cables 302, 304 having first ends 306, 307 secured substantially adjacent to the blade tip 42 and tensioning devices 314 secured in the area of the root portion 24, the positioning of such components may be reversed.

Thus, in an alternative embodiment, the tensioning devices 314 maybe disposed substantially adjacent to the tip 42. In such an embodiment, the first ends 306, 307 of the cables 302, 304 may be fixed to the root portion 24 of the rotor blade 22 or may be fixed to a portion of the hub 20. Additionally, as is described in greater detail below with reference to FIG. 7, the disclosed system 300 need not include both a first cable 302 and a second cable 304. For example, in one embodiment, the system may only include a single pressure side cable 302 or a single suction side cable 304 movably attached within the rotor blade 22. Alternatively, the disclosed system may include multiple cables, such as two or more cables, movably attached to the pressure and suction sides 52, 54 of the rotor blade 22.

[0038] Referring now to FIG. 5, there is illustrated a cross-sectional edge view of rotor blade 22 including another embodiment of a system 500 for detecting the deflection of a rotor blade 22 mounted to a hub 20 of a wind turbine rotor 18 (FIG. 1). In general, the system 500 may include the same or similar components to those described above with reference to FIGS. 3 and 4. However, unlike the above described embodiment, the system 500 includes a cable 502 having first and second ends 504, 506 that are both spaced apart from the tip 42 of the rotor blade 22. In particular, the first and second ends 504, 506 may be disposed at locations within the rotor blade 22 and/or the hub 20 such that cable 502 may be movably attached to the interior walls 310, 312 of both the pressure side 52 and the suction side 54 of the rotor blade 22. For example, as shown in FIG. 5, the first end 504 and the second end 506 (through the tensioning device 508) of the cable 502 may be secured to a portion of the hub 20 such that the cable 502 may be looped around or otherwise attached along the interior walls 310, 312 of both the pressure side 42 and suction side 54 of the rotor blade 22. In another embodiment, the ends 504, 506 of the cable 502 may be secured to opposing sides 52, 54 of the rotor blade 22 as an alternative to being secured within hub 20. Additionally, in further embodiments, the first end 504 of the cable 502 may be secured within the hub 20 while the second end 506 is secured to a portion of the rotor blade 22, and vice versa.

[0039] The system 500 may also include means for attaching the cable to the interior walls 310, 312 of the rotor blade 22 such that the cable 502 is displaced relative to the rotor blade 22. As described above, such means may comprise various different mounting devices and/or configurations (e.g., one or more guide supports 316 and/or one or more elongated cable supports 510). Thus, as shown, a plurality of guide supports 316 (e.g., guide rings, pulleys, eyelets, hooks, brackets and the like) may be secured to the interior walls 310, 312 of the rotor blade 22 and may be configured to support the cable 502 at various locations along the length of the rotor blade 22. For example, one the guide supports 316 may be disposed substantially adjacent to tip 42 of the rotor blade 22. As such, the cable 502 may be movably attached to the rotor blade 22 at the tip 42 so that displacements of the cable 502 may accurately reflect the total deflection of the rotor blade 22. The system 500 also includes elongated cable supports 510 mounted to interior walls 310, 312 of the rotor blade 22. As indicated above, suitable elongated cable supports 510 may include tubes, pipes, cable guides, and any other suitable member having a longitudinally defined opening, channel, recess or similar aperture into which the cable 502 may be inserted and movably supported along a length of the rotor blade 22.

[0040] It should be appreciated that the operation of the system 500 illustrated in FIG. 5 is substantially similar to that described above with reference to FIGS. 3 and 4. Thus, as the rotor blade 22 deflects a deflection distance 320 from its non-deflected longitudinal axis, the cable 502 is correspondingly displaced a displacement distance 512. Specifically, when the tip 42 of the rotor blade 22 defects in the direction of the suction side 54 of the blade 22, the cable 502 is extended or pulled away from the tensioning device 508. This linear displacement of the cable 502 may then be measured by the sensor 514 and utilized by the turbine controller 36 (FIG. 1) to estimate the deflection distance 320 of the rotor blade tip 42.

[0041] Referring now to FIG. 6, there is illustrated a cross-sectional edge view of a rotor blade 22 including further embodiment of a system 600 for detecting the deflection of a rotor blade 22 mounted to a hub 20 of a wind turbine rotor 18 (FIG. 1). In general, the system 600 may include the same or similar components to those described above with reference to FIGS. 3 and 4. Thus, the system 600 may include first and second cables 602, 604, with each cable 602, 604 including a first end 606, 607 secured to the rotor blade 22 substantially adjacent to the tip 42 and a second end 608, 609 coupled to a tensioning device 610. However, unlike the embodiment of FIGS. 3 and 4, a single tensioning device 610 is coupled to both cables 602, 604. In particular, as shown, the tensioning device 610 may comprise a spring, such as any suitable tension or compression spring, coupled at one end to the second end 608 of the first cable 602 and at the opposing end to the second end 609 of the second cable 604. As such, when the rotor blade 22 deflects, causing the cables 602, 604 to displace, the spring may expand and/or contract, as necessary, to maintain tension within the cables 602, 604.

[0042] Additionally, as shown in FIG. 6, the tensioning device 610 may be spaced apart from the root portion 24 such that it is secured to the rotor blade 22 at a predetermined length 612 from the interface of the rotor blade 22 and the hub 20. As such, the cables 602, 604 may be movably attached (e.g., using one or more guide supports 316 and/or elongated cable supports 510) to only a portion of the interior walls 310, 312 of the rotor blade 22. In general, it should be appreciated that the predetermined length 612 may correspond to any percentage of the total blade length of the rotor blade 22. For example, in various embodiments, the length 612 may be equal from about 10% to about 50% of the total blade length, such as from about 15% to about 40% of the total blade length or from about 20% to about 30% of the total blade length and all other subranges therebetween. However, in alternative embodiments, the predetermined length 612 may be equal to less than about 10% of the total blade length or greater than about 50% of the total blade length.

[0043] Additionally, in a particular embodiment, the predetermined length 612 may correspond to the portion of the rotor blade 22 that is generally not subject to substantial deflection during operation of a wind turbine. For example, in various rotor blade configurations, a portion of the rotor blade 22 extending from the root 24 may be designed to be significantly stiffer than the remainder of the rotor blade 22 and, thus, may not be subject to deflection during operation. As such, the predetermined length 612 may be chosen such that the tensioning device 610 is disposed substantially adjacent to the point on the rotor blade 22 at which deflection typically begins within the blade 22 during operations of the wind turbine. Of course, it should be appreciated that the point at which blade deflection initially occurs within a rotor blade 22 will generally vary from rotor blade to rotor blade and may depend on numerous factors including, but not limited to, the total length of the rotor blade 22, the stiffness of the rotor blade 22 and the operating parameters of the wind turbine.

[0044] It should also be appreciated that the operation of the system 600 illustrated in FIG. 6 is substantially similar to that described above with reference to FIGS. 3-5. However, unlike the earlier described embodiments, the sensors 614 are shown as being coupled to the cables 602, 604 instead of being coupled to the tensioning device 610. For example, a secondary cable or other suitable connective member 616 attached to each sensor 614 may be utilized to couple the sensors 614 to portions of each cable 602, 604. Thus, as the cables 602, 604 are displaced as a result of blade deflection, the sensors 614 may be capable of measuring their displacement distances 618, 620 by sensing or detecting the displacement of the secondary cable or connective member 614. Such measurements may then be correlated to the deflection distance 320 in order to determine the total blade deflection of the rotor blade 22.

[0045] Referring now to FIG. 7, there is illustrated a cross-sectional view of a rotor blade 22 including an embodiment of the disclosed system 700 installed therein in accordance with aspects of the present subject matter, particularly illustrating several of the plurality of different locations at which the cables 702 of the present subject matter may be movably attached within the rotor blade 22. As shown, the rotor blade 22 generally includes a leading edge 48, a trailing edge 50, a pressure side 52 and a suction side 54. The rotor blade also includes a shear web 56 positioned between top and bottom spar caps 58. As is generally known, the spar caps 58 and shear web 56 may extend longitudinally along the rotor blade 22 from the root portion 24 to the tip 22 (FIG. 2).

[0046] As shown in FIG. 7, a plurality of cables 702 may be movably attached along the interior walls 310, 312 of the pressure and suctions sides 52, 54 of the rotor blade 22. For example, a pair of cables 702 may be mounted to the interior walls 310, 312 of the pressure and suction sides 52, 54 substantially adjacent to the leading edge 48 of the rotor blade 22. Additionally, a pair of cables 702 may be mounted to the interior walls 310, 312 substantially adjacent to the trailing edge 50 of the rotor blade 22. Moreover, one or more cables 702 may also be movably attached to the interior of the spar caps 58 or on a location of the shear web 56. Thus, as shown, a pair of cables 702 may be mounted to interior walls 704 of top and bottom spar caps 58.

[0047] As was generally described above, each of the cables 702 may be movably attached within the rotor blade 22 using any suitable mounting and/or attachment mechanism known in the art, such as one or more guide supports 316 and/or one or more elongated cable supports 510. As shown in FIG. 7, such guide supports 316 and/or elongated cable supports 510 may generally have any cross section that permits the cables 702 to be movably or slidably supported substantially adjacent to an interior wall/surface of the rotor blade 22. For example, suitable cross-sections may include triangular cross-sections, circular or oval cross-sections, hooked or “J” shaped cross-sections, rectangular or square cross-sections and the like.

[0048] Referring still to FIG. 7, it should be appreciated that the cables 702 need not be disposed at the exact locations shown in the illustrated embodiment. Rather, the cables 702 of the present subject matter may be movably attached at any suitable location within the rotor blade 22, including, but not limited to, any location on the interior walls 310, 312 of the rotor blade 22, any location on the interior wall 704 of the spar caps 58 or any location along the shear web 56. Moreover, it should also be appreciated that, although six cables 702 are shown in the illustrated embodiment, the system 700 of present subject matter may generally include any number of cables 702 mounted within the rotor blade 22, such as less than six cables or greater than six cables. For example, in the embodiment illustrated in FIGS. 3 and 4, only a single pressure side cable (e.g., first cable 302) may be included within the system 300. Alternatively, the system 300 of FIGS. 3 and 4 may include multiple pressure and suction side cables.

[0049] In general, it should be appreciated that the various embodiments described above need not be viewed in isolation. Rather, the various components, mounting configurations (including the relative positioning of the components) and other features illustrated or described as part of one embodiment may be utilized together with one or more features of another embodiment to yield a different embodiment.

[0050] It should also be appreciated that, in alternative embodiments of the present subject matter, the cables of the disclosed system may comprise Bowden cables or may otherwise be configured as pushrods or similar mechanisms. In such embodiments, it should be apparent that the displacement of the cable(s) may be detected and measured without the inclusion of a tensioning device.

[0051] Referring now to FIG. 8, there is illustrated a flow diagram of one embodiment of a method for detecting and controlling the deflection of a rotor blade 22 of a wind turbine 10 (FIG. 1). As shown, the method generally includes measuring the displacement of at least one cable mounted to an interior wall of the rotor blade as the rotor blade deflects 802, analyzing the displacement measurement(s) to determine an operating parameter of the rotor blade 804 and performing a corrective action when the operating parameter of the rotor blade exceeds a predetermined reference point 806. In particular, as indicated above, cable displacement measurements taken by the disclosed sensors 318, 514, 614 maybe transmitted to the turbine controller 36. Such displacement measurements may then be analyzed by the turbine controller 36 to determine a particular operating parameter of the rotor blade 22 (e.g., blade deflection, blade loading and tower clearance), which can then be utilized as a control parameter for issuing control commands and/or performing corrective actions designed to reduce the blade deflection occurring within the rotor blade 22. For example, the performance of corrective actions may permit a wind turbine 10 to be adaptable in response to varying operating conditions, such as highly variable wind conditions. Thus, in one embodiment, the controller 36 may be configured to perform a corrective action as a safeguard against the risk of tower strikes, component fatigue and various other issues that may arise as a result of excessive blade deflection and/or loading of the rotor blade 22.

[0052] As described above, suitable mathematical expressions and/or look-up tables may be stored within the turbine controller 36 for correlating cable displacement measurements to the blade deflection (i.e., deflection distance 320) of the rotor blade 22. In addition, the controller 36 may also be provided with suitable computer-readable instructions corresponding to mathematical expressions and/or look-up tables for correlating the cable displacement measurements and/or the blade deflection to various other operating parameters of the rotor blade 22. For example, in one embodiment, the determined blade deflection may be utilized to estimate the blade load or wind load acting on the rotor blade 22. Specifically, as should be understood by those of ordinary skill in the art, the total load acting on the rotor blade 22 may be estimated or approximated using beam theory, such as by using known dynamic beam equations having variables including, but not limited to, the determined blade deflection, the Modulus of Elasticity of the rotor blade 22, the Moment of Inertia and the length of the rotor blade 22, or using any other suitable mathematical model. As another example, the determined blade deflection may be utilized to calculate the distance or clearance between the rotor blade 22 and the tower 12 (FIG. 1) of the wind turbine 10. In particular, since the non-deflected blade clearance 40 (FIG. 1) may be known, the tower clearance may be calculated by subtracting the determined blade deflection from the non-deflected blade clearance 40. It should be appreciated by those of ordinary skill in the art that various other operating parameters of the rotor blade 22 may be estimated and/or approximated utilizing the turbine controller 36 by correlating the cable displacement measurements and/or the blade deflection to such operating parameters using suitable mathematical models and/or look-up tables.

[0053] As indicated above, in addition to being configured to determine blade deflection and other operating parameters of the rotor blade 22, the controller 36 may also be configured to issue a control command to components of the wind turbine 10 or otherwise perform a corrective action in order to reduce or prevent blade deflection based on a comparison of the determined operating parameter with a predetermined reference or control point. For example, in one embodiment, the controller 36 may be configured to perform a corrective action in response to a determined blade deflection of one or more of the rotor blades 22 that exceeds a predetermined blade deflection threshold. Alternatively, the controller 36 may be configured to perform a corrective action in response to blade loading of one or more of the rotor blades 22 that exceeds a predetermined load threshold. As should be readily apparent to those of ordinary skill in the art, various other operating parameters, having corresponding reference points and/or thresholds, may also be utilized as control parameters for performing corrective actions on the wind turbine 10.

[0054] In general, the extent or magnitude of blade deflection and/or blade loading required before it may be desirable for the controller 36 to perform a corrective action may vary from wind turbine to wind turbine. For example, the predetermined blade deflection threshold and the predetermined load threshold may vary depending on numerous factors including, but not limited to, the operating conditions of the wind turbine 10, the stiffness of the rotor blades 22, the length of the rotor blades 22 and the non-deflected blade clearance 40. Thus, it should be appreciated that particular reference points or threshold values must be chosen depending on the particular application in which the system and methods of the present subject matter are being utilized.

[0055] It should also be appreciated that the particular corrective action performed by the controller 36 can take many forms. For example, the corrective action may include altering the pitch angle of one or more rotor blades 22 for a partial or full revolution of the rotor 18. As indicated above, this may be accomplished by controlling a pitch adjustment system 32. As is generally understood, altering the pitch angle of a rotor blade 22 may reduce blade deflection by increasing out-of-plane stiffness.

[0056] In another embodiment, the corrective action may include yawing the nacelle 16 to change the angle of the nacelle 16 relative to the direction 28 (Fig. 1) of the wind. A yaw drive mechanism (not illustrated) is typically used to change the angle of the nacelle 16 so that the rotor blades 22 are properly angled with respect to the prevailing wind. For example, pointing the leading edge 48 of a rotor blade 22 upwind can reduce loading on the blade 22 as it passes the tower 12.

[0057] Alternatively, the corrective action may comprise modifying the blade loading on the wind turbine 10 by increasing the torque demand on the electrical generator (not illustrated) positioned within the nacelle 16. This reduces the rotational speed of the rotor blades 22, thereby potentially reducing the aerodynamic loads acting upon the surfaces of the blades 22.

[0058] It should be readily appreciated, however, that the controller 36 need not perform one of the corrective actions described above and may generally perform any corrective action designed to reduce blade deflection. Additionally, the controller 36 may be configured to perform multiple corrective actions simultaneously, which may include one or more of the corrective actions described above.

[0059] This written description uses examples to disclose the invention, including the best mode, and also to enable any person 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. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

A system for detecting the deflection of a rotor blade connected to a hub of a wind turbine rotor, comprising: a cable extending at least adjacent to a tip of the rotor blade and comprising a first end and a second end , wherein the first end is attached to one of the rotor blades and the hub; a clamping device attached to one of the rotor blades and the hub, wherein the clamping device is connected to the other end of the cable and configured to maintain a predetermined tension in the cable between the first end and the second end; and a sensor connected to at least one of the cable and the clamping device, the sensor being designed to measure a displacement of the cable, wherein the cable is attached to at least one inner wall of the rotor blade between the first end and the second end, so that the cable shifts relative to the rotor blade as the rotor blade deflects.

A system according to claim 1, wherein the first end of the cable is attached to the rotor vane substantially adjacent to the tip of the rotor vane.

A system according to claim 2, wherein the clamping device is attached to the rotor vane substantially adjacent to a root portion of the rotor vane.

The system of claim 1, wherein the cable comprises a first cable and a second cable, wherein the first cable is attached to an inner wall of a pressure side of the rotor wing and the second cable is attached to an inside wall of a suction side of the rotor wing.

The system of claim 4, wherein the first cable and the second cable each comprise a first end and a second end, the first ends of the first and second cables being attached to the rotor vane substantially adjacent to the tip of the rotor vane, and the the other ends of the first and second cables are connected to a single clamping device or separate clamping devices.

The system of claim 1, wherein the first end of the cable and clamping device is attached to the rotor blade or hub, such that the cable is secured to an inner wall of a pressure side of the rotor wing and an inner wall of a suction side of the rotor blade.

The system of claim 1, wherein the cable comprises a plurality of cables attached to the at least one inner wall of the rotor blade between the first end and the second end such that the plurality of cables are displaced relative to the rotor wing as the rotor wing deflects.

The system of claim 7, wherein at least one cable of the plurality of cables is attached to an inner wall of a pressure side of the rotor blade, and at least one other cable of the plurality of cables is attached to an inner wall of a suction side of the rotor blade.

A system according to any one of claims 1-8, wherein the clamping device comprises a wire pulling device or a spring.

A system according to any one of claims 1-9, further comprising means for securing the cable to the inner wall of the rotor blade, such that the cable is displaced relative to the rotor wing as the rotor blade deflects.

The system of claim 10, wherein the means for attaching the cable to the inner wall of the rotor blade comprises at least one guide support.

The system of claim 11, wherein the mites for securing the cable to the inner wall of the rotor blade comprise at least one elongated cable support.

A system according to any one of claims 1-12, wherein the sensor comprises at least one of a displacement transducer, a linear encoder, a string pot sensor, a wire pull sensor, a yoyo pot sensor, a linear potentiometer, a length measuring instrument or a linear length sensor.

A system according to any one of claims 1-13, further comprising a turbine control unit, wherein the turbine control unit is designed to make a correction to control the load on the rotor blade or avoid collision with the tower as the rotor blade deflects.

A method of detecting and controlling the deflection of a rotor vane by a wind turbine, comprising: measuring a displacement of at least one cable fixed movably to an inner wall of the rotor vane when the rotor vane deflects using a system according to a of claims 1-14; analyzing the displacement measurement to determine an operating parameter of the rotor blade; and to make a correction when the rotor blade operating parameter exceeds a predetermined reference point.

The method of claim 15, wherein the operating parameter comprises blade load and the predetermined reference point comprises a predetermined load threshold.

The method of claim 15, wherein the operating parameter comprises blade deflection and the predetermined reference point comprises a predetermined blade deflection threshold.

A method according to any of claims 15-17, wherein the correction comprises changing the pitch angle of the rotor blade.

The method of any one of claims 15-17, wherein the correction comprises bending a nacelle of the wind turbine.

A method according to any one of claims 15-17, wherein the correction comprises changing the blade load of the rotor blade.