Abstract:
A method and system for repairing a wind turbine component in a wind turbine is provided. A damaged region of a drive assembly affects the wind turbine component. The method includes the steps of, providing a replacement wind turbine component, providing a mount for the replacement wind turbine component, and installing the replacement wind turbine component and mount in an undamaged region of the drive assembly. The replacement wind turbine component and mount are located to avoid interaction with the damaged region.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates generally to wind turbines, and more specifically to repair of pitch control components. 
         [0002]    At least some known wind turbines have pitch control systems comprised of a bearing coupled between a blade and a hub with a pitch motor positioning the blade attached to the bearing. The bearing may include a row of teeth that engage a gear of the motor. The motor&#39;s gear turns or pitches the blade by interacting with the teeth on the pitch bearing. Over time some of the bearing&#39;s teeth can become damaged, worn or may break off Current known solutions to repair a pitch control component require the removal of the affected blade or the entire rotor. In either case, a large crane is required for removal, and cranes of this type are costly. In addition, the wind turbine is taken off-line until the repairs can be completed. 
         [0003]    In some wind turbines, the blades are up to 60 meters in length, but may be designed to be up to 100 meters, so removal to change a damaged pitch control system can be costly and time consuming. Other known wind turbines are offshore, requiring extensive equipment to remove a blade and replace the pitch control system components. Wind turbines hub heights can be over 120 meters and in high winds, making it dangerous for workers to be on the wind turbines. 
         [0004]    A malfunctioning pitch control system can also cause a blade to move out of a pitch setting such that the blades of the wind turbine asymmetrically load the hub and rotor shaft. If the rotor begins to move within the stator due to the asymmetric loading, there is a possibility of the rotor contacting the stator, for example, in direct drive application with the turbine rotor being attached directly to the generator. An electrical transient can occur if the rotor and stator contact, and the wind turbine may then have to be taken off-line. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0005]    In one aspect of the present invention, a method for repairing a wind turbine component in a wind turbine is provided. A damaged region of a drive assembly affects the wind turbine component. The method includes the steps of, providing a replacement wind turbine component, providing a mount for the replacement wind turbine component, and installing the replacement wind turbine component and mount in an undamaged region of the drive assembly. The replacement wind turbine component and mount are located to avoid interaction with the damaged region. 
         [0006]    In another aspect of the present invention, a method for repairing a wind turbine component in a wind turbine is provided. A damaged region of a drive assembly affects the wind turbine component. The method includes the steps of, providing a replacement wind turbine component, providing a mount for the replacement wind turbine component, installing the mount in a portion of the drive assembly, and installing the replacement wind turbine component on the mount. The replacement wind turbine component and mount are located to avoid interaction with the damaged region. 
         [0007]    In still another aspect of the present invention, a system for repairing a wind turbine component in a wind turbine is provided. A damaged region of a drive assembly affects the wind turbine component. The system includes a replacement wind turbine component and a mount for the replacement wind turbine component. The replacement wind turbine component and mount are installed in a location of the drive assembly so as to avoid interaction with the damaged region. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective illustration of an exemplary wind turbine; 
           [0009]      FIG. 2  is a partially cut-away perspective illustration of a portion of the wind turbine shown in  FIG. 1 ; 
           [0010]      FIG. 3  is a cross-sectional view illustration of a portion of a rotor hub of the wind turbine shown in  FIGS. 1-2  illustrating an exemplary embodiment of a pitch system; and 
           [0011]      FIG. 4  is a is a cross-sectional view illustration of a portion of a rotor hub of the wind turbine shown in  FIGS. 1-2  illustrating an exemplary embodiment of a repaired pitch system; and 
           [0012]      FIG. 5  is a flowchart illustrating steps of the method to repair a wind turbine component, according to aspects of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    As used herein, the term “blade” is intended to be representative of any device that provides reactive force when in motion relative to a surrounding fluid. As used herein, the term “wind turbine” is intended to be representative of any device that generates rotational energy from wind energy, and more specifically, converts kinetic energy of the wind into mechanical energy. As used herein, the term “wind generator” is intended to be representative of any wind turbine that generates electrical power from rotational energy generated from wind energy, and more specifically, converts mechanical energy converted from kinetic energy of wind to electrical power. As used herein, the term “windmill” is intended to be representative of any wind turbine that uses rotational energy generated from wind energy, and more specifically mechanical energy converted from kinetic energy of wind, for a predetermined purpose other than generating electrical power, such as, but not limited to, pumping a fluid and/or grinding a substance. 
         [0014]      FIG. 1  is a perspective view of an exemplary embodiment of an exemplary wind turbine  10 . Wind turbine  10  described and illustrated herein is a wind generator for generating electrical power from wind energy. In some known wind turbines, wind turbine  10  is any type of wind turbine, such as, but not limited to, a windmill (not shown). Moreover, wind turbine  10  described and illustrated herein includes a horizontal-axis configuration. In some known wind turbines, wind turbine  10  includes a vertical-axis configuration (not shown). Wind turbine  10  may be coupled to an electrical load (not shown), such as, but not limited to, a power grid (not shown), and may receive electrical power therefrom to drive operation of wind turbine  10  and/or its associated components and/or may supply electrical power generated by wind turbine  10 . Although only one wind turbine  10  is shown in  FIGS. 1-3 , in some embodiments a plurality of wind turbines  10  are grouped together, to form a “wind farm”. 
         [0015]    Wind turbine  10  includes a body  12 , sometimes referred to as a “nacelle”, and a rotor (generally designated by  14 ) coupled to body  12  for rotation with respect to body  12  about an axis of rotation  16 . In the exemplary embodiment, nacelle  12  is mounted on a tower  18 . The height of tower  18  is any suitable height enabling wind turbine  10  to function as described herein. Rotor  14  includes a hub  20  and a plurality of blades  22  (sometimes referred to as “airfoils”) extending radially outwardly from hub  20  for converting wind energy into rotational energy. Although rotor  14  is described and illustrated herein as having three blades  22 , rotor  14  may include any number of blades  22 . 
         [0016]      FIG. 2  is a partially cut-away perspective view of a portion of an exemplary wind turbine  10 . Wind turbine  10  includes an electrical generator  26  coupled to rotor  14  for generating electrical power from the rotational energy generated by rotor  14 . Generator  26  is any suitable type of electrical generator, such as, but not limited to, a wound rotor induction or permanent magnet generator. Rotor  14  includes a rotor shaft  28  coupled to rotor hub  20  for rotation therewith. Generator  26  is coupled to rotor shaft  28  such that rotation of rotor shaft  28  drives rotation of the generator rotor, and therefore operation of generator  26 . In the exemplary embodiment, the generator rotor has a rotor shaft  30  coupled thereto and coupled to rotor shaft  28  such that rotation of rotor shaft  28  drives rotation of the generator rotor. In the exemplary embodiment, generator rotor shaft  30  is coupled to rotor shaft  28  through a gearbox  32 , although in other embodiments generator rotor shaft  30  is coupled directly to rotor shaft  28 . The rotation of rotor  14  drives the generator rotor to thereby generate variable frequency AC electrical power from rotation of rotor  14 . 
         [0017]    In some embodiments, wind turbine  10  includes a brake system (not shown) for braking rotation of rotor  14 . Furthermore, in some embodiments, wind turbine  10  includes a yaw system  40  for rotating nacelle  12  about an axis of rotation  42  to change a yaw of rotor  14 . Yaw system  40  is coupled to and controlled by a control system(s)  44 . In some embodiments, wind turbine  10  includes anemometry  46  for measuring wind speed and/or wind direction. Anemometry  46  is coupled to control system(s)  44  for sending measurements to control system(s)  44  for processing thereof. In the exemplary embodiment, control system(s)  44  is mounted within nacelle  12 . Alternatively, one or more control systems  44  may be remote from nacelle  12  and/or other components of wind turbine  10 . Control system(s)  44  may be used for, but is not limited to, overall system monitoring and control including, for example, pitch and speed regulation, high-speed shaft and yaw brake application, yaw and pump motor application, and/or fault monitoring. Alternative distributed or centralized control architectures may be used in some embodiments. 
         [0018]      FIG. 3  is a cross-sectional view of a portion of hub  20  illustrating an exemplary embodiment of a pitch system  24 . Wind turbine  10  includes variable blade pitch system  24  for controlling a pitch angle of rotor blades  22  with respect to a wind direction. Pitch system  24  is coupled to control system(s)  44  for control thereby. Blade  22  and pitch system  24  are coupled to bearing  80  housed in hub  20 . Bearing  80  has an inner race  82  and a concentric outer race  84 . Inner race  82  is coupled to blade  22  and outer race  84  is coupled to pitch system  24 . An annular groove  86  is defined between inner race  82  and outer race  84  and includes at least one material  88  which reduces friction when inner race  82  and outer race  84  move with respect to each other. Material  88  is at least one of rollers or balls (not shown) or a lubricant (not shown). Alternatively, blade  22  is coupled to outer race  84 , and inner race  82  is coupled to hub  20  wherein pitch system  24  drives outer race  84  to control the position of blade  22 . 
         [0019]    In some embodiments, pitch system  24  includes one or more actuators. The pitch actuators include any suitable structure, configuration, arrangement, means, and/or components, such as, but not limited to, electrical motors, hydraulic cylinders, springs, and/or servomechanisms. Moreover, the pitch actuators are driven by any suitable means, such as, but not limited to, hydraulic fluid, electrical power, electro-chemical power, and/or mechanical power, such as, but not limited to, spring force. In some embodiments, the pitch actuators are driven by energy extracted from at least one of a rotational inertia of rotor  14  and a stored energy source (not shown) that supplies energy to components of wind turbine  10 . In the exemplary embodiment, pitch system  24  includes a pitch drive gear  90  and a toothed pitch ring gear  92  coupled to hub  20  and blades  22  via bearing  80 . Pitch system  24  utilizes actuators for changing the pitch angle of blades  22  by rotating blades  22  coupled to inner race  82  with respect to hub  20  and outer race  84 . More specifically, in the exemplary embodiment, the pitch actuators include a pitch drive gear  90  that is coupled to a pitch ring gear  92 . Pitch ring gear  92  is coupled to blade  22  such that rotation of pitch drive gear  90  rotates blade  22  about an axis of rotation  94  to thereby change the pitch of blade  22 . 
         [0020]    As described earlier, the teeth of pitch ring gear  92  can become damaged or worn, no longer providing the correct functionality. Known repairs for this issue involve replacing or turning the pitch bearing to engage the pitch drive pinion with undamaged gear teeth. To change the bearing, the blade and or rotor must be removed, resulting in a difficult and costly operation involving high capacity cranes with high reaches. 
         [0021]    The method and system, according to aspects of the present invention, include providing a pitch drive mount that can be brought up into the hub and attached to the hub either using self-fixturing or separate tooling to drill and tap mounting holes in the hub, thus enabling a pitch drive to be applied to one of the undamaged section of the pitch ring gear teeth. Typically, only about one quadrant  310  of the pitch ring gear teeth are actually driven by the pitch drive gear  90 , and often the damage is restricted to less than that, sometimes only one to a few teeth. The method of the present invention enables several repairs over the life of the turbine without ever having to drop the rotor or reposition the bearing 
         [0022]      FIG. 4  is a cross-sectional view of a portion of hub  20  illustrating an exemplary embodiment of a repaired pitch system  24 , according to aspects of the present invention. A damaged region  410  of the pitch ring gear  92 , can be avoided by moving the pitch drive gear to a new quadrant or section of the pitch ring gear  92 . In this embodiment a new pitch drive gear  420  has been moved to a position within quadrant  430 . Only the ring gear teeth in quadrant  430  will be used in this example, thereby avoiding the damaged region  410 . It is to be understood that other quadrants or other incremental changes within the same quadrant could be employed as new positions for the pitch drive gear  420 , as long as the damaged region  410  is avoided. As non-limiting examples, the pitch drive gear  420  could be moved at least 15 degrees or at least 45 degrees away from the original position of pitch drive gear  90 . In addition, the pitch drive gear  90  could be moved to the new location or a replacement pitch drive gear  420  and/or motor could be installed in a new location. 
         [0023]    The pitch drive is typically permanently mounted in the hub, set to properly bear on the pitch ring gear teeth correctly in line, and often incorporates a sensor or sensors (not shown) to feedback bearing position and stops for the rotation of blade  22 . The mount for the replacement pitch drive can incorporate the ability to pick up the sensor(s) and stops, and can include locating features to ensure good engagement of the pinion and adjustment capability for the backlash and internal clearance. These features may be included with a housing that is designed to fit within the hub curvature. Mounting holes may be provided that can be used to bolt into the hub. Drilling and tapping the mounts for the housing in the hub can be done using the housing for fixturing or a separate fixturing tool that picks up on the same curvature and flange on the hub as it will finally mount to. 
         [0024]      FIG. 5  illustrates an exemplary method, according to the present invention, which may comprise the following steps: 
         [0025]    Providing a pitch drive at step  510 . The pitch drive may include the existing drive or a replacement drive. 
         [0026]    Providing a pitch drive mount at step  520 . The mount may be an existing mount or a replacement mount. 
         [0027]    Installing the original or replacement pitch drive and mount on an undamaged region of the pitch bearing ring gear at step  530 . This step  530  can include installing the drive and mount in a new quadrant or in a new location that avoids use of the damaged section of ring gear teeth. 
         [0028]    Disconnecting the original pitch drive from the ring gear at step  540 . If the original pitch motor and/or gear are to be used in the new location this step may be performed before steps  510 - 530 . 
         [0029]    Returning the wind turbine to service at step  550 . This is an optional step and can be performed as desired. 
         [0030]    The above-described method and system to repair pitch control components facilitate repairs required by the blade pitch system. The exemplary embodiment is a cost-effective way to repair a pitch control system in a wind turbine. Furthermore, the exemplary embodiment of repairing pitch control components minimizes or eliminates the use of a large crane, reduces the need for dangerous and expensive maintenance work on the turbine, and decreases the time required for repairs to minimize the amount of time a wind turbine is off-line. 
         [0031]    The apparatus is not limited to the specific embodiments described herein, but rather, components of the method may be utilized independently and separately from other components described herein. For example, the repair process may also be used with other control systems for controlling bearings (e.g., yaw), and is not limited to practice with only wind turbine blade assemblies as described herein. Rather, the present invention can be implemented and utilized in connection with many other pitch or yaw applications. 
         [0032]    While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.