Patent Publication Number: US-2013243590-A1

Title: Systems and methods for determining thrust on a wind turbine

Description:
FIELD OF THE INVENTION 
     The present subject matter relates generally to wind turbines and, more particularly, to a system and methods for determining the thrust on wind turbine rotor blades. This information can be used during peak shaving in order to reduce loads while minimizing power losses. 
     BACKGROUND OF THE INVENTION 
     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 modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades are the primary elements for converting wind energy into electrical energy. The blades typically have the cross-sectional profile of an airfoil such that, during operation, air flows over the blade producing a pressure difference between the sides. Consequently, a lift force, which is directed from the pressure side towards the suction side, acts on the blade. The lift force generates torque on the main rotor shaft, which is geared to a generator for producing electricity. 
     At wind speeds below the rated wind speed of a wind turbine (i.e., the wind speed at which a wind turbine can achieve its rated power), the pitch angle of the rotor blades is typically maintained at the power position in order to capture the maximum amount of energy from the wind. However, as wind speeds reach and exceed the rated wind speed, the pitch angle must be adjusted towards feather to maintain the power output of the wind turbine at its rated power, thereby preventing components of the turbine, such as electrical components, from being damaged. Thus, the aerodynamic loads acting on the rotor blades continually increase with increasing wind speeds while the pitch angle of the rotor blades is maintained at the power position (i.e., until the rated wind speed is achieved) and then begin to decrease as the pitch angle is adjusted towards feather with wind speeds above the rated wind speed. Such control of the wind turbine typically creates a peak in the aerodynamic loading on a wind turbine at its rated wind speed. For example,  FIG. 1  illustrates a graph of wind speed (x-axis) versus loads (y-axis) for a typical wind turbine. As shown, aerodynamic loads on the wind turbine increase to a peak  10  at the rated wind speed (indicated by line  12 ) and then decrease as the rotor blades are pitched toward feather in order to maintain the wind turbine at its rated power. 
     To prevent the formation of such a peak  10 , peak shaving control methods are known that may be used to reduce the loads on a wind turbine at or near the rated wind speed. In particular, these control methods typically begin to adjust the pitch angle of the rotor blades at some point prior to the rated wind speed. For example, as shown in  FIG. 1 , by adjusting the pitch angle of the rotor blades towards feather prior to reaching the rated wind speed (line  12 ), the loads acting on the rotor blade at or near the rated wind speed may be reduced. Specifically, as shown in  FIG. 1 , the use of a peak shaving control method may create a peak shaving range  14  within the graph at which loads are reduced along a range of wind speed values. In part, the point to begin peak shaving is determined by thrust exerted on the rotor blades of the wind turbine by the wind. Thrust is not a measured value but can be calculated based on variables and constants such as wind speed, the design of the wind turbine, the configuration of the wind turbine (e.g., blade pitch), and the like. 
     While peak shaving control methods are useful for reducing the loads at or near the rated wind speed, they also result in significant power losses within the peak shaving range  14 . Specifically, the rate of change in which the loads acting on a wind turbine are adjusted within the peak shaving region  14  is relatively slow, which is characterized in graph by the rounded-off, curved section  16  within the peak shaving range  14 ). This slow rate of change results in significant power losses, as it takes longer for the wind turbine to achieve its rated power as the pitch angle is adjusted during peak shaving. 
     Accordingly, an improved system and/or method that provides for sufficient load reduction while minimizing power losses based on measured thrust values would be welcomed in the technology. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Aspects and advantages of embodiments 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. 
     In one aspect, the present subject matter discloses a method for determining thrust on a wind turbine. The method may generally include determining an amount of deflection of a rotor of a wind turbine having one or more rotor blades affixed to the rotor; correlating the amount of deflection of the rotor with thrust on at least one of the one or more rotor blades; and adjusting a pitch angle for at least one of the one or more rotor blades during peak shaving. 
     In another aspect, the present subject matter discloses a system for determining thrust on a wind turbine. The system may be comprised of a wind turbine comprising a rotor, wherein one or more rotor blades of the wind turbine are affixed to the rotor; and one or more sensors located on or within the rotor, wherein the one or more sensors measure deflection of the rotor. 
     In another aspect, the present subject matter discloses yet another system for determining thrust on a wind turbine. The system may be comprised of a wind turbine comprising a hub, wherein one or more rotor blades of the wind turbine are affixed to the hub; one or more sensors located within the hub, wherein the one or more sensors measure deflection of the hub; and a controller, wherein the controller is configured to: receive a signal from said one or more sensors, said signal indicating an amount of deflection of the hub caused by thrust on the one or more rotor blades of the wind turbine; determine a value for the thrust on the one or more rotor blades of the wind turbine using said signal; and determine, using at least in part the value for the thrust on the one or more rotor blades of the wind turbine, a pitch angle for at least one of the one or more rotor blades during peak shaving. 
     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 DRAWINGS 
       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: 
         FIG. 1  illustrates one embodiment of a graph of wind speed (x-axis) versus loads (y-axis) for a typical wind turbine, particularly illustrating the use of a conventional linear peak shaving method to reduce loads on the wind turbine; 
         FIG. 2  illustrates a perspective view of one embodiment of a wind turbine; 
         FIG. 3  illustrates a perspective, internal view of one embodiment of a nacelle of a wind turbine; 
         FIGS. 4A through 4C  illustrate a portion of the rotor of a wind turbine having various sensors located within the hub to measure deflection of the hub caused by thrust on the one or more rotor blades of the wind turbine; 
         FIG. 5  illustrates a schematic diagram of one embodiment of a turbine controller of a wind turbine; 
         FIG. 6  illustrates a flow diagram of one embodiment of a method for determining the thrust on a wind turbine having one or more rotor blades affixed to a hub of the wind turbine by measuring deflection of the hub caused by the thrust; and 
         FIG. 7  illustrates a flow diagram of another embodiment of a method for determining the thrust on a wind turbine having one or more rotor blades affixed to a hub of the wind turbine by measuring deflection of the hub caused by the thrust. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     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. 
     In general, the present subject matter is directed to a system and methods for determining deflection of the hub of a wind turbine having one or more rotor blades attached to the hub by one or more sensors located within the hub and using the deflection to determine thrust on the one or more rotor blades of the wind turbine. In one aspect, the measured thrust value can be used at least in part to determine a pitch angle for at least one of the one or more rotor blades of the wind turbine in order to perform peak shaving. 
     Referring now to  FIG. 2 , a perspective view of one embodiment of a wind turbine  20  is illustrated. As shown, the wind turbine  20  generally includes a tower  22  extending from a support surface  24 , a nacelle  26  mounted on the tower  22 , a rotor  28  coupled to the nacelle  26 , and at least one rotor blade  32  coupled to and extending outwardly from the hub  30 . For example, in the illustrated embodiment, three rotor blades  32  are coupled to the hub  30 . However, alternative embodiments may include more or less than three rotor blades  32 . Each rotor blade  32  may be spaced about the hub  30  to facilitate rotating the rotor  28  to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. For instance, the hub  30  may be rotatably coupled to an electric generator  34  ( FIG. 3 ) positioned within the nacelle  26  to permit electrical energy to be produced. The rotor  28  can include the hub  30 , attachment means for affixing the one or more rotor blades  32  to the hub  30  including flanges, bolts, clamps, and the like, pitch adjustment mechanism  42  ( FIG. 3 ), and any means for coupling the hub  30  with the electric generator  34 . 
     The wind turbine  10  may also include a turbine control system or turbine controller  36  within the nacelle  26 , or at any other suitable location. In general, the turbine controller  36  may comprise a computer or other suitable processing unit. Thus, in several embodiments, the turbine controller  36  may include suitable computer-readable instructions that, when implemented, configure the controller  36  to perform various different functions, such as receiving, transmitting and/or executing wind turbine control signals. As such, the turbine controller  36  may generally be configured to control the various operating modes (e.g., start-up or shut-down sequences) and/or components of the wind turbine  20 . For example, the controller  36  may be configured to adjust the blade pitch or pitch angle of each rotor blade  22  (i.e., an angle that determines a perspective of the blade  22  with respect to the direction of the wind) about its pitch axis  38  in order to control the rotational speed of the rotor blade  32  and/or the power output generated by the wind turbine  20 . For instance, the turbine controller  36  may control the pitch angle of the rotor blades  32 , either individually or simultaneously, by transmitting suitable control signals directly or indirectly (e.g., via a pitch controller  40  ( FIG. 3 )) to one or more pitch adjustment mechanisms  42  ( FIG. 3 ) of the wind turbine  10 . During operation of the wind turbine  20 , the controller  36  may generally control each pitch adjust mechanism  42  in order to alter the pitch angle of each rotor blade  30  between 0 degrees (i.e., a power position of the rotor blade  30 ) and 90 degrees (i.e., a feathered position of the rotor blade  30 ). 
     Referring now to  FIG. 3 , a simplified, internal view of one embodiment of the nacelle  26  of the wind turbine  20  shown in  FIG. 1  is illustrated. As shown, a generator  34  may be disposed within the nacelle  26 . In general, the generator  34  may be coupled to the rotor  28  for producing electrical power from the rotational energy generated by the rotor  28 . For example, as shown in the illustrated embodiment, the rotor  28  may include a rotor shaft  44  coupled to the hub  30  for rotation therewith. The rotor shaft  44  may, in turn, be rotatably coupled to a generator shaft  46  of the generator  34  through a gearbox  48 . As is generally understood, the rotor shaft  44  may provide a low speed, high torque input to the gearbox  48  in response to rotation of the rotor blades  32  and the hub  30 . The gearbox  48  may then be configured to convert the low speed, high torque input to a high speed, low torque output to drive the generator shaft  46  and, thus, the generator  34 . 
     Additionally, the turbine controller  36  may also be located within the nacelle  26 . As is generally understood, the turbine controller  36  may be communicatively coupled to any number of the components of the wind turbine  20  in order to control the operation of such components. For example, as indicated above, the turbine controller  36  may be communicatively coupled to each pitch adjustment mechanism  42  of the wind turbine  20  (one of which is shown) via a pitch controller  40  to facilitate rotation of each rotor blade  32  about its pitch axis  38 . 
     In general, each pitch adjustment mechanism  42  may include any suitable components and may have any suitable configuration that allows the pitch adjustment mechanism  42  to function as described herein. For example, in several embodiments, each pitch adjustment mechanism  42  may include a pitch drive motor  50  (e.g., any suitable electric motor), a pitch drive gearbox  52 , and a pitch drive pinion  54 . In such embodiments, the pitch drive motor  50  may be coupled to the pitch drive gearbox  52  so that the pitch drive motor  50  imparts mechanical force to the pitch drive gearbox  52 . Similarly, the pitch drive gearbox  52  may be coupled to the pitch drive pinion  54  for rotation therewith. The pitch drive pinion  54  may, in turn, be in rotational engagement with a pitch bearing  56  coupled between the hub  30  and a corresponding rotor blade  32  such that rotation of the pitch drive pinion  54  causes rotation of the pitch bearing  56 . Thus, in such embodiments, rotation of the pitch drive motor  50  drives the pitch drive gearbox  52  and the pitch drive pinion  54 , thereby rotating the pitch bearing  56  and the rotor blade  32  about the pitch axis  38 . 
     In alternative embodiments, it should be appreciated that each pitch adjustment mechanism  42  may have any other suitable configuration that facilitates rotation of a rotor blade  32  about its pitch axis  28 . For instance, pitch adjustment mechanisms  42  are known that include a hydraulic or pneumatic driven device (e.g., a hydraulic or pneumatic cylinder) configured to transmit rotational energy to the pitch bearing  56 , thereby causing the rotor blade  32  to rotate about its pitch axis  38 . Thus, in several embodiments, instead of the electric pitch drive motor  50  described above, each pitch adjustment mechanism  42  may include a hydraulic or pneumatic driven device that utilizes fluid pressure to apply torque to the pitch bearing  56 . 
     Referring still to  FIG. 3 , the wind turbine  20  may also include a plurality of sensors  58 ,  60  for monitoring one or more parameters and/or conditions of the wind turbine  20 . As used herein, a parameter or condition of the wind turbine  20  is “monitored” when a sensor  58 ,  60  is used to determine its present value. Thus, the term “monitor” and variations thereof are used to indicate that the sensors  58 ,  60  need not provide a direct measurement of the parameter and/or condition being monitored. For example, the sensors  58 ,  60  may be used to generate signals relating to the parameter and/or condition being monitored, which can then be utilized by the turbine controller  36  or other suitable device to determine the actual parameter and/or condition. 
     In several embodiments of the present subject matter, the wind turbine  20  may include one or more sensors  58 ,  60  configured to monitor a peak shaving parameter of the wind turbine  20 . As used herein, the term “peak shaving parameter” refers to any operating parameter and/or condition of a wind turbine  20  that may be directly or indirectly related to the pitch angle of a rotor blade such that the peak shaving control method described below with reference to  FIG. 5  may be performed. For example, in several embodiments, the peak shaving parameter may correspond to the power output of the wind turbine  20 . Thus, in such embodiments, the wind turbine  20  may include one or more power output sensors  58  configured to monitor the power output of the wind turbine  20 . For instance, the power output sensor(s)  58  may comprise sensors configured to monitor electrical properties of the output of the generator  34 , such as current sensors, voltage sensors or power monitors that monitor power output directly based on current and voltage measurements. Alternatively, the power output sensors  58  may comprise any other sensors that may be utilized to monitor the power output of a wind turbine  20 . For example, in one embodiment, the power output sensors  58  may comprise one or more strain gauges or torque sensors configured to detect torque on the output shaft of the generator  34 , which may then be correlated to the power output of the wind turbine  20 . 
     In other embodiments, the peak shaving parameter may correspond to loads acting on the wind turbine  20 . In such embodiments, the wind turbine  20  may include one or more load sensors  60  configured to monitor the loads acting on and/or through one or more of the components of the wind turbine  20 . For example, the load sensors  60  may be configured to directly or indirectly measure thrust loads on one or more of the components of the wind turbine  20 , such as by monitoring thrust loads on the rotor  28  by monitoring wind speed using an anemometer or any other suitable wind speed sensor. In addition, the load sensors  60  may be configured to directly or indirectly measure the moments acting on and/or through one or more of the components of the wind turbine  20  (e.g., by monitoring the bending moments acting on the tower and/or the blades and/or by monitoring the nodding moments acting on machine head), such as by using strain gauges, accelerometers, position sensors, optical sensors and/or the like to monitor the deflections of one or more wind turbine components caused by bending moments. For example, as shown in  FIG. 3 , one or more load sensors  60  may be mounted within the rotor blades  32  and/or the tower  14  to monitor any bending moments acting on such components. Of course, it should be appreciated that the load sensors  60  may comprise any other suitable sensors configured to monitor any other loads acting on the wind turbine  20 . 
     It should also be appreciated that, in alternative embodiments, the peak shaving parameter may comprise any other suitable operating parameter and/or condition of a wind turbine  20  that may be directly or indirectly related to the target pitch angle required for peak shaving. In such embodiments, the wind turbine  20  may include any suitable sensors that permit such peak shaving parameter to be monitored. In addition, it should be appreciated that the peak shaving parameter may comprise a combination of operating parameters and/or conditions of a wind turbine  20 , such as a combination of power output and loads. 
     In various aspects, deflection of the hub  30  caused by thrust on the one or more rotor blades  32  can be measured by various sensors located within the hub  30  including, for example, one or more laser deflection sensors, one or more distance measurement sensors, one or more strain gauges, and the like. Various combinations of such sensors can also be used in one aspect to measure hub deflection. 
       FIGS. 4A through 4C  illustrate a portion of the rotor  28  of a wind turbine  20  having various sensors located within the hub  30  to measure deflection of the hub  30  caused by thrust  402  on the one or more rotor blades  32  of the wind turbine  20 . Generally, thrust loads  402  bend the blades  32  toward the tower  22  of the wind turbine  20 . This bending of the blades  32  also causes bending or deflection of the hub  30  to which the blades  32  are affixed. Generally, the front part  302  of the hub  30  is extended and the back part  304  of the hub  30 , which is connected to the main shaft  44 , is slightly compressed. Sensors can be positioned at various locations, both radially and axially, within the hub  30  to measure the deflection caused by the thrust  402 . For example,  FIG. 4A  illustrates a portion of the rotor  28  of a wind turbine  20  having one or more laser deflection sensors  404  located within the hub  30  to measure deflection of the hub  30  caused by thrust  402  on the one or more rotor blades  32  of the wind turbine  20 . One or more of the laser deflection sensors  404  can be located at various locations in the hub  30  to measure deflection of the hub  30 . Generally, the laser deflection sensor  404  is comprised of a laser source and receiver  406  and a mirror  408 . Deflection of the hub caused by thrust on the one or more rotor blades  32  of the wind turbine  20  causes the location of the reflected laser on the receiver to change. This change can cause the laser deflection sensor  404  to transmit a signal that correlates with the changed location. For example, this signal may be transmitted to the turbine controller  36  where the signal can be correlated with the amount of thrust on the wind turbine  20 . This signal can be transmitted to the turbine controller  36  via wired (including fiber optic) or wireless communications medium, or combinations thereof. 
       FIG. 4B  illustrates a portion of the rotor  28  of a wind turbine  20  having one or more distance measurement sensors  410  located within the hub  30  to measure deflection of the hub  30  caused by thrust  402  on the one or more rotor blades  32  of the wind turbine  20 . One or more of the distance measurement sensors  410  can be located at various locations, both radially and axially, in the hub  30  to measure deflection of the hub  30 . For example, the one or more distance measurement sensors  410  can comprise one or more optical (including laser and photoelectric), mechanical, inductive, ultrasonic, and the like distance measurement devices. Generally, deflection of the hub caused by thrust on the one or more rotor blades  32  of the wind turbine  20  causes the distances within the hub  30  to change, which can be detected by the one or more distance measurement sensors  410  and converted into a signal that correlates with the changed distances. This signal may be transmitted to the turbine controller  36  where the signal can be correlated with the amount of thrust on the wind turbine  20 . This signal can be transmitted to the turbine controller  36  via wired (including fiber optic) or wireless communications medium, or combinations thereof. 
       FIG. 4C  illustrates a portion of the rotor  28  of a wind turbine  20  having one or more strain gauges  412  located within the hub  30  to measure deflection of the hub  30  caused by thrust  402  on the one or more rotor blades  32  of the wind turbine  20 . One or more of the strain gauges  412  can be located at various locations, both radially and axially, in the hub  30  to measure deflection of the hub  30 . Generally, deflection of the hub caused by thrust on the one or more rotor blades  32  of the wind turbine  20  causes the distances within the hub  30  to change, which can be detected by the one or more strain gauges  412  and converted into a signal that correlates with the changed distances. This signal may be transmitted to the turbine controller  36  where the signal can be correlated with the amount of thrust on the wind turbine  20 . This signal can be transmitted to the turbine controller  36  via wired (including fiber optic) or wireless communications medium, or combinations thereof. 
       FIGS. 4A-4C  illustrate non-limiting examples of sensors that can be used to detect deflection of the hub  30  cause by thrust  402 . It is to be appreciated that any other sensor, transducer or measurement device, now existing or later developed, that can detect or measure deflection of the hub  30  is contemplated within the scope of embodiments of the present invention. 
     Referring now to  FIG. 5 , there is illustrated a block diagram of one embodiment of suitable components that may be included within the turbine controller  36  (or the pitch controller  40 ), or any other controller that receives a signal from the sensors located within the hub  30 , in accordance with aspects of the present subject matter. As shown, the turbine controller  36  may include one or more processor(s)  62  and associated memory device(s)  64  configured to perform a variety of computer-implemented functions (e.g., performing the methods, steps, calculations and the like disclosed herein). As used herein, the term “processor” refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. Additionally, the memory device(s)  64  may generally comprise memory element(s) 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 device(s)  64  may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s)  62 , configure the turbine controller  36  to perform various functions including, but not limited to, directly or indirectly (via the pitch controller  40 ) transmitting suitable control signals to one or more of the pitch adjustment mechanisms  42 , monitoring the peak shaving parameter(s) of the wind turbine  20 , determining target pitch angles for the rotor blades  32  based on the peak shaving parameter(s) and various other suitable computer-implemented functions. 
     Additionally, the turbine controller  36  may also include a communications module  66  to facilitate communications between the controller  36  and the various components of the wind turbine  10 . For instance, the communications module  66  may serve as an interface to permit the turbine controller  36  to transmit control signals to each pitch adjustment mechanism  42  for controlling the pitch angle of the rotor blades  32 . Moreover, the communications module  66  may include a sensor interface  68  (e.g., one or more analog-to-digital converters) to permit signals transmitted from the sensors (e.g.,  58 ,  60 ,  404 ,  410 ,  412 ) to be converted into signals that can be understood and processed by the processors  62 . The turbine controller  36  may be communicatively coupled to one or more sensors  58 ,  50   m    404 ,  410 ,  412  configured to monitor a peak shaving parameter of the wind turbine  20 , such as the power output of the wind turbine  20 , and/or the loads acting on the wind turbine  20  including deflection of the hub  30  caused by thrust loading  402  on at least one of the one or more rotor blades of the wind turbine  20 . Thus, the turbine controller  36  may be configured to receive signals from such sensors  58 ,  60 ,  404 ,  410 ,  412  associated with the peak shaving parameter. Alternatively, the turbine controller  36  may be provided with suitable computer readable instructions that, when implemented by its processor(s)  62 , configure the turbine controller  36  to calculate and/or estimate one or more of the peak shaving parameters of the wind turbine  20  based on information stored within its memory  64  and/or based on other inputs received by the turbine controller  36 . 
     Referring now to  FIG. 6 , there is illustrated one embodiment of a method for determining the thrust on a wind turbine having one or more rotor blades affixed to a hub of the wind turbine by measuring deflection of the hub caused by the thrust. As shown, the method generally includes step  602 , receiving a signal with a controller, wherein the signal indicates the amount of deflection of the hub. As described herein, such deflection can be detected by one or more various sensors located within the hub including, for example, one or more laser deflection sensors, one or more distance measurement sensors, one or more strain gauges, and the like. The various sensors can convert the detected deflection to a signal that can be transmitted to the controller. At step  604 , the detected deflection can be correlated with thrust on at least one of the one or more rotor blades of the wind turbine. Such correlation can be performed by the controller using tables, graphs, and the like for various designs, configurations and materials used to construct the wind turbine.  FIG. 7  illustrates the steps of the method of  FIG. 6 , further including the step (step  702 ) of determining a target pitch angle for at least one rotor blade of the wind turbine based on the determined thrust and (step  704 ) adjusting the pitch angle for the rotor blade during peak shaving. 
     By providing the ability to more quickly adjust the loads acting on a wind turbine  20 , the power output that may be achieved using the disclosed methods can be higher than the power output that may achieved using conventional peak shaving methods where thrust is an estimated or calculated value rather than a directly measured value. For example, in some embodiments, an increase in annual energy production (AEP) of about 1 to 2% may be obtained using the disclosed methods for peak shaving as opposed to the conventional peak shaving methods. However, it is also believed that increases in AEP of greater than about 1 to 2% may also be achieved using the disclosed methods. 
     As indicated above, it should be appreciated that, in several embodiments, the disclosed methods may be implemented automatically using the turbine controller  36  or any other suitable processing unit. For example, the rotor blades  32  may be maintained in the power position until the predetermined peak shaving threshold is reached. However, once the predetermined peak shaving threshold is reached, the turbine controller  36  may automatically adjust the pitch angle of the rotor blades  32 , such as by directly or indirectly (via the pitch controller(s)  40 ) transmitting control signals to the pitch adjustment mechanisms  42 , based on the peak shaving parameter(s) of the wind turbine  20 . For instance, as described above, in one embodiment, data correlating hub deflection with thrust may be stored within the memory of the controller  36 . In such an embodiment, the controller  36  may be configured to automatically determine the peak shaving parameter (e.g., by analyzing measurement signals from the sensors  58 ,  60 ,  408 .  410 ,  412  described above) and then calculate the target pitch angle for each rotor blade  32  based on the measured thrust. The calculated pitch angles may then be used as the basis for adjusting the actual pitch angles of the rotor blades during peak shaving. 
     As described above and as will be appreciated by one skilled in the art, embodiments of the present invention may be configured as a system, method, or computer program product. Accordingly, embodiments of the present invention may be comprised of various means including entirely of hardware, entirely of software, or any combination of software and hardware. Furthermore, embodiments of the present invention may take the form of a computer program product on a computer-readable storage medium having computer-readable program instructions (e.g., computer software) embodied in the storage medium. Any suitable non-transitory computer-readable storage medium may be utilized including hard disks, CD-ROMs, optical storage devices, or magnetic storage devices. 
     Embodiments of the present invention have been described above with reference to block diagrams and flowchart illustrations of methods, apparatuses (i.e., systems) and computer program products. It will be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, respectively, can be implemented by various means including computer program instructions. These computer program instructions may be loaded onto a general purpose computer, special purpose computer, or other programmable data processing apparatus, such as the processor(s)  62  discussed above with reference to  FIG. 5 , to produce a machine, such that the instructions which execute on the computer or other programmable data processing apparatus create a means for implementing the functions specified in the flowchart block or blocks. 
     These computer program instructions may also be stored in a non-transitory computer-readable memory that can direct a computer or other programmable data processing apparatus (e.g., processor(s)  62  of  FIG. 5 ) to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including computer-readable instructions for implementing the function specified in the flowchart block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions that execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. 
     Accordingly, blocks of the block diagrams and flowchart illustrations support combinations of means for performing the specified functions, combinations of steps for performing the specified functions and program instruction means for performing the specified functions. It will also be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, can be implemented by special purpose hardware-based computer systems that perform the specified functions or steps, or combinations of special purpose hardware and computer instructions. 
     Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps or operational flow; plain meaning derived from grammatical organization or punctuation; the number or type of embodiments described in the specification. 
     Throughout this application, various publications may be referenced. The disclosures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art to which the methods and systems pertain. 
     Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these embodiments of the invention pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the embodiments of the invention are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe exemplary embodiments in the context of certain exemplary combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.