Patent Application
20090311097
The present invention relates generally to wind power energy production, and more particularly to a method and system for improving the energy production and control of wind plants by the use of blade inflow angle.
The present application is related to co-pending patent applications entitled Wind Turbine Blade Flow Condition Measurement and Control, Attorney Docket No. 227-414, filed the same day as this application, and Wind Turbine Blade Mounted Composite Sensor Support, Attorney Docket No. 232-749, filed the same day as this application, both related applications incorporated by reference in their entirety.
Recently, wind turbines have received increased attention as an environmentally safe and relatively inexpensive alternative energy source. With this growing interest, considerable efforts have been made to develop wind turbines that are reliable and efficient.
Generally, a wind turbine includes a plurality of blades coupled to a rotor through a hub. The rotor is mounted within a housing or nacelle, which is positioned on top of a tubular tower or base. Utility grade wind turbines (i.e. wind turbines designed to provide electrical power to a utility grid) can have large rotors (e.g., thirty or more meters in diameter). Blades on these rotors transform wind energy into a rotational torque or force that drives the rotor of one or more generators, rotationally coupled to the rotor. The rotor is supported by the tower through a bearing that includes a fixed portion coupled to a rotatable portion. The bearing is subject to a plurality of loads including the weight of the rotor, a moment load of the rotor that is cantilevered from the bearing, asymmetric loads, such as, horizontal and shears, yaw misalignment, and natural turbulence.
In addition, wind turbines have a controller, which adjusts the pitch angle of the blade to optimize energy capture below rated winds, and regulate power above rated winds. The controller may utilize a fixed fine pitch angle in the variable speed region and adjusts the pitch in above rated wind speed, depending on the power output and rotational speed of the turbine. The preset pitch angles that are input in to the controller for fine pitch control are based on 2D wind tunnel aerodynamic coefficients. In the field, wind turbine blades experience induction from the rotor as well as 3D flow field conditions with turbulence that is not accounted for in the prediction models. Field data has indicated that the actual aerodynamic and acoustical performance can be significantly different than current prediction models and 2D steady state wind tunnel data predict. By having an actual measurement of the inflow angle, which is correlated to the angle of attack, the turbine blade pitch is more efficiently controlled with increased energy conversion efficiency and avoiding blade stall. The acoustical performance may also be adjusted based on this measurement to allow a lower noise operation when desired.
Several research institutes in the wind turbine industry have attempted to characterize the inflow angle and angle of attack of wind turbine blades, however, none have developed a system that uses state of the art technology for pressure measurement that utilizes digital temperature compensation which eliminates the need for span calibration systems on the turbine. In addition, no other system uses a pressure measurement for closed loop control of the blade pitch angle for optimum performance, or uses the blade flow parameter.
Therefore, what is needed is a method and system for measuring the actual inflow angle correlated to the angle of attack to the blade.
The object of the present invention is to provide a wind turbine blade measurement system that measures the aerodynamic inflow angle that is correlated to the angle of attack, such that the blade pitch can be controlled at the optimum angle utilizing a closed loop control.
According to a first embodiment of the invention, a wind turbine control system is disclosed that includes a wind turbine blade having an airfoil. The airfoil includes a pressure side, a suction side, a leading edge, a trailing edge, and a length between a root edge and a tip. The wind turbine control system further includes a probe support structure attached to the wind turbine blade, a pressure probe attached to the probe support structure at a predetermined position from the leading edge, and a control system configured to receive sensor inputs from the pressure probe. The control system is configured to process the sensor inputs to control blade pitch of the wind turbine blade.
According to a second embodiment of the invention, a wind turbine is disclosed that includes a wind turbine blade having an airfoil, the airfoil comprising a pressure side, a suction side, a leading edge, a trailing edge, and a length between a root edge and a tip. The wind turbine further includes a probe support structure attached to the wind turbine blade, a pressure probe attached to the probe support structure at a predetermined position from the leading edge, and a control system configured to receive sensor inputs from the pressure probe. The control system is configured to process the sensor inputs to control blade pitch of the wind turbine blade.
According to a third embodiment of the invention, a method of controlling a wind turbine having at least one wind turbine blade is disclosed that includes measuring air pressure at a fixed position from the at least one wind turbine blade, and adjusting a pitch angle of the at least one wind turbine blade in response to the measured air pressure.
Further aspects of the method and system are disclosed herein. The features as discussed above, as well as other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.
Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which a preferred embodiment of the invention is shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art.
The wind turbine 100 includes a wind turbine control system (not shown) that adjusts wind turbine functions to control power production of the wind turbine 100. The wind turbine control system includes hardware and software configured to perform turbine functions as appreciated by one of ordinary skill in the art. The wind turbine functions include, but are not limited to regulation of blade rotational speed. The blade rotational speed may be controlled by adjusting parameters including the blade pitch and generator torque.
As shown in
The pressure measurement system 200 may be located at any position along the length L along the leading edge 201 of the airfoil portion 205. In one embodiment, the pressure measurement system 200 is positioned between approximately 60% and 80% of the length L from the root portion 209. In another embodiment, the pressure measurement system 200 is position between approximately 65% and 75% of the length L from the root portion. In yet another embodiment, the pressure measurement system 200 is positioned at approximately 75% of the length L from the root portion. In this exemplary embodiment, the turbine blade 108 includes one pressure measurement system 200. In another embodiment, the turbine blade 108 may include one or more pressure measurement systems 200 positioned along the leading edge 201 of the turbine blade 108.
As further seen in
As also seen in
The probe support structure 302 extends from the blade 108 and bends at a bend angle a at a position P proximate to the pressure probe 300. The position P is sufficient to place the pressure probe 300 outside of interference from the support structure 302. For example, the position P may be approximately 35 to 80 cm from the pressure probe 300. In this exemplary embodiment, the bend angle a is approximately 10 degrees. In another embodiment, the bend angle α may be more or less than 10 degrees, as determined by the expected inflow angle at the desired measurement location. In yet another embodiment, the bend angle α may vary between 0-20 degrees. The bend angle α allows the probe 300 to obtain a more accurate inflow angle measurement. The inflow angle measurement range of the probe 300 is at least 0-20 degrees in any direction from the centerline of the probe 300.
The turbine blade 108 further includes a pressure scanner 312 having a high frequency response for receiving pressure inputs from the probe 300. The pressure scanner 312 is disposed within the turbine blade 108. The pressure scanner 312 is configured to receive pressure inputs from the pressure probe 300. In this exemplary embodiment, the probe support structure 302 includes fluid passages in fluid communication between the pressure probe 300 and the pressure scanner 312 for providing the pressure inputs from the pressure probe 300 to the pressure scanner 312. The pressure scanner 312 provides pressure inputs or indication of inflow angle to the wind turbine control system (not shown). In another embodiment, the pressure probe 300 may include transducers and/or other sensors and electronics to provide electrical pressure data directly to the wind turbine control system.
Referring to
The wind turbine 100 may further include a heating system (not shown) configured to ensure that the pressure probe 300 is substantially free of ice and/or snow. In one embodiment, the wind turbine 100 includes an ant-icing system configured to ensure the pressure probe 300 is substantially free of ice and/or snow during operation.
The wind turbine 100 may further include a lightning protection system (not shown). In one embodiment, the lightning protection system is configured to protect the pressure probe 300 and related components from damage from lightning strikes.
The wind turbine control system receives a measurement of inflow angle from the pressure probe 300 through the pressure scanner 312. The inflow angle, as well as other parameters and inputs, are used by the wind turbine control system to adjust the blade pitch to optimize energy capture and avoid stall conditions by the wind turbine 100. The turbine control system may use the measurement of the inflow angle to adjust blade pitch to a desired value to improve energy capture and avoid stall conditions. An iterative or adaptive method may be used in the adjustment of pitch based on inflow angle and measured power produced by the wind turbine 100. The measurement of inflow angle may also be used by the wind turbine control system to reduce the inflow angle at times of desired low noise operation.
The wind turbine control system may include additional probes and sensors (not shown). In another embodiment, the wind turbine control system may include a system of static pressure taps that are flush with the blade surface. The probes may be positioned along the turbine blade radially on the leading edge to produce an indication of the angle of attack. In yet another embodiment, the wind turbine control system may include a mechanical wind vane inflow angle measurement device.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
