Patent Application
20170175710
This application claims priority to European Application No. 15201294.4 having a filing date of Dec. 18, 2015 the entire contents of which are hereby incorporated by reference.
The following relates to a method, a wind turbine and to a device for calibrating a yaw system of a wind turbine. In addition, a related computer program product and a computer readable medium are suggested.
A wind turbine in operation will not always experience wind perpendicular to a rotor plane. When the rotor plane (which is also referred to as heading) of a wind turbine is not perpendicular to the wind, the efficiency will decrease. Therefore, actual wind turbines comprise a yaw system designed to automatically adjust their heading, like, e.g., rotating the rotor plane perpendicular to the incoming wind or to maintain an angle relative to the wind to maximize the surface area of the turbine rotor (“yawing”).
Usually, the yaw system is part of a nacelle, which may be involved in a yawing movement, i.e. being rotatable mounted on top of a tower via at least one yaw bearing. A rotor is attached to an upwind side of the nacelle. The rotor is coupled via a drive train to a generator housed inside the nacelle. The rotor includes a central rotor hub and a plurality of blades mounted to and extending radially from the rotor hub defining the rotor plane.
It is important for wind power plant operators to know an actual position or direction of the rotor plane or heading of the respective wind turbine, the plane or heading being correlated with an actual position or direction of the nacelle. The actual direction of the nacelle is also referred to as a yaw direction or a yaw position or, in relation to a predefined direction (e.g. a cardinal direction), as a yaw angle. Alternatively the yaw angle may be defined as the direction of the nacelle in relation of the direction of the incoming wind.
Information concerning the yaw direction is a commonly used basis for analyzing data concerning a wind turbine or performing sector management control like, e.g.,
In order to determine, e.g., an absolute yaw angle, a wind turbine may be equipped with a yaw encoder, measuring the relative yaw direction in relation to a stationary object like, e.g., a tower being secured to a foundation at ground level. The yaw encoder is typically calibrated by determining a reference yaw direction or reference yaw angle after finalization of the wind turbine installation (also referred to as “initial calibration”).
In some scenarios the initial calibration of the yaw angle is incorrect or less accurate due to applying a rough estimate or rule of thumb to determine a cardinal direction as a basis or reference for the yaw angle calibration.
A further reason for an inaccurate yaw angle calibration is a wind turbine installation based on a design including powerful permanent magnets, eliminating the possibility of applying magnetic compasses to determine the yaw direction or yaw angle. A magnetic compass, as a further general disadvantage, comprises inaccurateness per se, in particular at installations located at high geographic latitudes.
Alternatively, compasses based on GPS (Global Positioning System) or other satellite-based positioning systems have been applied to determine the reference yaw direction of the wind turbine. However, these systems may require special skills by specific service teams and service time being restricted to specific test and measurement applications.
Further on, the aforementioned systems may bear the risk that a specific yaw position or yaw direction offset may be overwritten or deleted in a wind turbine configuration like, e.g., a software parameter list. There might be also a risk of the yaw sensor being changed during service of damage. In such kind of situation there might be a risk of a not properly calibrated yaw position and that a wrong yaw position might be read out.
An aspect relates to an improved approach for optimizing the yaw system of a wind turbine.
In order to overcome this problem, a method is provided for calibrating a yaw system of a wind turbine, comprising the following steps:
Determining the true position of the sun means deriving information representing an actual position of the sun at the sky. This information may also represent a sun position vector, i.e., information representing a direction towards the true sun position in relation to, e.g., the geographic position of the wind turbine.
Calibrating means determining a reference yaw direction or a reference yaw angle based on, e.g., sun position information. As an example the cardinal direction “North” may be determined as reference yaw direction based on the proposed solution.
The proposed solution provides an economical and in particular a reasonable priced method for calibrating or re-calibrating the yaw system of a wind turbine.
It is one aspect of embodiments of the invention presented that the true sun position might be used as a reliable and absolute direction indicator during calibration of the yaw system.
In an embodiment, the turbine specific information comprises at least one out of the following:
A geographic position may be defined by using a geographic coordinate system. As an example, the geographic position may be defined according to
Calendar information may be local day and local time according to the geographic position of the individual wind turbine.
Calibration information may be already existing information, e.g.
As an example, the aforementioned turbine specific information may be assigned to a lookup table stored in a memory of the wind turbine.
In another embodiment, the method comprises
In an embodiment the true sun position is determined with the help of at least one sun position sensor.
In a further embodiment,
In a next embodiment,
It is also an embodiment that the method is executed during an unwinding procedure of the nacelle.
Pursuant to another embodiment, during determination of the true sun position disturbing effects are minimized or removed.
Disturbing effects might be blade shadow effects during normal operation of the wind turbine as well as night- and cloud effects being removed or minimized by using appropriate algorithms or filter.
The problem stated above is also solved by a wind turbine comprising
The problem stated above is also solved by a device comprising and/or being associated with a processor unit and/or hard-wired circuit and/or a logic device that is arranged such that the method as described herein is executable thereon.
Said processing unit may comprise at least one of the following: a processor, a microcontroller, a hard-wired circuit, an ASIC, an FPGA, a logic device.
The solution provided herein further comprises a computer program product directly loadable into a memory of a digital computer, comprising software code portions for performing the steps of the method as described herein.
In addition, the problem stated above is solved by a computer-readable medium, e.g., storage of any kind, having computer-executable instructions adapted to cause a computer system to perform the method as described herein.
The solution provided herein further comprises at least one sun position sensor for determining a true or actual position of the sun, the at least one sun position sensor comprising
Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:
One possible embodiment of the light sensitive sensor 230 is a photosensitive resistor.
Alternatively a CCD sensor (Charge-Coupled Device) may be used.
The ground plate 210 may further comprise a marker 250 being aligned with the longitudinal axis 245 indicating a current direction (also referred to as “orientation”) of the sun position sensor 200. In
According to the proposed solution, the sun position sensor 200 can be rotated according to a rotation axis arranged in a perpendicular order to the ground plate 200. In
According to the scenario as shown in
In contrast, according to the exemplary scenario as shown in
That measured or registered difference of intensity of light dependent on the orientation of the sun position sensor 200 is the basis for determining the true position of the sun according to the proposed solution.
According to one possible embodiment of the proposed solution the sun position sensor 200 as shown in
The following steps may be applied for calibrating a yaw position of the wind turbine according to the proposed solution:
In a first step a position of the sun may be estimated (“estimated sun position”) based on current configuration information/data of the wind turbine. These configuration data may also include current calibration data which might be information resulting from a former calibration step executed in the past.
In a second step the wind turbine is yawed according to the estimated sun position, i.e. the nacelle including a rotor hub of the wind turbine is yawed in a way that the heading or yaw direction of the wind turbine is line with the estimated sun position. Consequently, due to the fixed attachment, the orientation of the sun position senor 200 is changing accordingly.
In a third step the estimated sun position is verified with the true sun position by analyzing the registered intensity of light measured by the sun position sensor 200. For that, further movement, i.e., yawing of the nacelle in both possible yawing directions might be necessary to determine a maximum of the measured intensity of light or to determine a minimum of shadow covering the light sensitive sensor 230. By identifying a maximum of light intensity (alternatively a minimum of shadow intensity) the true position of light may be determined.
In case of misalignment between the estimated and the true position of the sun a new calibration or re-calibration of the yaw system may be initiated during a forth step.
The composition or design of the sun position sensor 400 is such that as the sun moves over the sky and/or the wind turbine yaws, the shadow emitted or projected by the circular disk 420 will cover at least partly the light sensitive area of a certain number of the light sensitive sensors 430 while the remaining light sensitive sensors 430 will be fully exposed to sunlight. Based on such available information, i.e. which of the light sensitive sensors 430 are covered by an individual percentage of shadow (“shadow coverage”) or not it is possible by data processing to derive a heading vector (“sun position vector”) indicating the direction towards the true position of the sun.
Further information might be necessary for an accurate determination of the true position of the sun like, e.g., at least one out of the following:
According to an advanced embodiment, continuous measurements, i.e. continuous analyzing of the shadow coverage of the light sensitive sensors 430 will allow an averaging of the results and thus providing a very accurate derivation of the true position of the sun.
The exemplary operating scenario of FIG. SA is representing a chronological situation around mid-day. Due to the shadow typically emitted by the circular disk 420 at the time of mid-day a first number (indicated by a reference number 430A) of the light sensitive sensors is covered at least partly by the shadow (indicated by an arrow 520) and a second number (indicated by a reference number 430B) of the light sensitive sensors are not covered by the shadow 520. Based on individual measurement signals provided by the light sensitive sensors 430 an actual sun position vector (indicated by an arrow 530) can be derived pointing towards a true position of the sun.
Further to that, as already explained above, an estimated sun position can be determined based on available (e.g. stored) wind turbine specific information.
In case of a misalignment between the true sun position and the estimated sun position a new calibration or re-calibration of the yaw system can be initiated.
Two further exemplary scenarios are shown in
As an advantage, by using a sun position sensor 400 as shown in
According to a further possible embodiment of the provided solution (not shown) the sun position sensor as shown in
The basic principle of all possible embodiments of the proposed solution is based on a measurement of ambient light intensity. Thus, during processing the resulting measurement signals it has to be distinguished between normal daylight, electrical lights sources and direct sunlight wherein the intensity of light is the desired parameter to be used to control wind turbine operation.
Further disturbing effects may be caused by lightning in connection with electrical wires associated with the sensors. These disturbing effects may be avoided by using, e.g., optical fiber cables.
A block 610 is representing an operational step of measuring the current light intensity by using a sun position sensor according to the proposed solution. A resulting measurement signal 615 is provided to a processing step (represented by a block 620) applying algorithms for filtering or removing disturbing effects like, e.g., blade shadow effects, night- and clouds-effects.
A resulting signal 625, representing, e.g., a derived true sun position is forwarded to a further operational step indicated by a block 640.
A further block 630 is representing an operational step of determining an estimated sun position based on, e.g.,
The estimated sun position 635 is provided to the operational step 640 representing an operational step of calculating a possible misalignment between the provided true sun position 625 and the provided estimated sun position 635. Thereby, in case of a calculated misalignment between both sun positions 625, 635 the operational step 640 also represents a further calibration step or re-calibration step based on the calculated misalignment.
Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.
For the sake of clarity, it is to be understood that the use of ‘a’ or ‘an’ throughout this application does not exclude a plurality, and ‘comprising’ does not exclude other steps or elements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 15201294.4 | Dec 2015 | EP | regional |
