Patent Application
20130243590
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.
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,
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
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.
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.
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:
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
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 (
Referring now to
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
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
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
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.
Referring now to
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, 50m 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
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
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
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.
