APPARATUS FOR AND METHOD OF DETECTING ONE OR MORE PROPERTIES OF A ROTOR BLADE DURING OPERATION OF A WIND TURBINE

Abstract

Provided is an apparatus for detecting properties of a rotor blade of a wind turbine the apparatus including: at least one leaky feeder configured to be arranged around the tower, an electromagnetic transmitter connected to the at least one leaky feeder and configured for transmitting a first electromagnetic signal along the at least one leaky feeder, a reflector for diverting and/or focusing the first electromagnetic signal in a predetermined direction, thereby forming a reflected first electromagnetic signal, an electromagnetic receiver connected to the at least one leaky feeder and configured for receiving a second electromagnetic signal from the at least one leaky feeder, the second electromagnetic signal being reflected from the rotor blade, and a processing unit connected to the electromagnetic transmitter and the electromagnetic receiver and configured to determine the properties of the rotor blade by analysing the first electromagnetic signal and the second electromagnetic signal.

Claims

1. An apparatus for detecting one or more properties of a rotor blade during operation of a wind turbine, the wind turbine including a tower, a nacelle and the rotor blade, the apparatus comprising: at least one leaky feeder configured to be arranged around a circumference of the tower, an electromagnetic transmitter connected to the at least one leaky feeder and configured for transmitting a first electromagnetic signal along the at least one leaky feeder, a reflector for diverting and/or focusing the first electromagnetic signal in a predetermined direction, thereby forming a reflected first electromagnetic signal, an electromagnetic receiver connected to the at least one leaky feeder and configured for receiving a second electromagnetic signal from the at least one leaky feeder, the second electromagnetic signal being reflected from the rotor blade when the reflected first electromagnetic signal hits the rotor blade, and a processing unit connected to the electromagnetic transmitter and the electromagnetic receiver and configured to determine the one or more properties of the rotor blade by analysing the first electromagnetic signal and the second electromagnetic signal.

2. The apparatus according to claim 1, wherein the reflector is configured to be arranged between the circumference of the tower and the at least one leaky feeder.

3. The apparatus according to claim 1, wherein the at least one leaky feeder is configured to emit the first electromagnetic signal towards the tower.

4. The apparatus according to claim 1, wherein the reflector comprises a single integral reflector unit or a plurality of reflector units configured to be distributed around the circumference of the tower.

5. The apparatus according to claim 1, wherein the reflector is further configured to divert and/or focus the second electromagnetic signal towards a predetermined portion of the at least one leaky feeder.

6. The apparatus according to claim 1, further comprising a reflector adjustment unit for adjusting the predetermined direction.

7. The apparatus according to claim 1, wherein the at least one leaky feeder comprises a first leaky feeder and a second leaky feeder, the first leaky feeder being connected to the electromagnetic transmitter and the second leaky feeder being connected to the electromagnetic receiver.

8. The apparatus according to claim 1, wherein the at least one leaky feeder is geometrically configured to form an arc around the tower or a loop surrounding the tower.

9. The apparatus according to claim 1, wherein the at least one leaky feeder and/or the electromagnetic transmitter and/or the electromagnetic receiver are installed on the tower or inside the tower.

10. The apparatus according to claim 1, wherein the first electromagnetic signal and the second electromagnetic signal are radar signals or ultrasonic signals.

11. The apparatus according to claim 1, wherein the at least one leaky feeder is a coaxial leaky cable or a leaky waveguide.

12. The apparatus according to claim 1, wherein the one or more properties of the rotor blade comprises one or more of a rotor blade position, a rotor blade speed, a rotor blade distance from tower, a rotor blade size, a rotor blade soiling state, or structural changes inside the rotor blade.

13. The apparatus according to claim 1, further comprising a leaky feeder adjusting unit for adjusting an emission direction of the first electromagnetic signal from the at least one leaky feeder.

14. A wind turbine comprising: a tower, a nacelle, at least one rotor blade, and an apparatus, the apparatus having: at least one leaky feeder configured to be arranged around a circumference of the tower, an electromagnetic transmitter connected to the at least one leaky feeder and configured for transmuting a first electromagnetic signal along the at least one leaky feeder, a reflector for deverting and/or focusing the first electromagnetic signal in a predetermined direction, thereby forming a reflected first electromagnetic signal, an electromagnetic receiver connected to the at least one leaky feeder and configured for receiving a second electromagnetic signal from the at least one leaky feeder, the second electromagnetic signal being reflected from the rotor blade when the reflected first electromagnetic signal hits the rotor blade, and a processing unit connected to the electromagnetic transmitter and the electromagnetic receiver and configured to determine the one or more properties of the rotor blade by analysing the first electromagnetic signal and the second electromagnetic signal.

15. A method of detecting one or more properties of a rotor blade during operation of a wind turbine, the wind turbine comprising a tower and a nacelle, the method comprising: arranging at least one leaky feeder around a circumference of the tower, transmitting a first electromagnetic signal along the at least one leaky feeder, diverting and/or focusing the first electromagnetic signal in a predetermined direction, thereby forming a reflected first electromagnetic signal, receiving a second electromagnetic signal from the at least one leaky feeder, the second electromagnetic signal being reflected from the rotor blade when the reflected first electromagnetic signal hits the rotor blade, and determining the one or more properties of the rotor blade by analysing the first electromagnetic signal and the second electromagnetic signal.

Description

DETAILED DESCRIPTION

[0055] FIG. 1 shows a partial cross-sectional view of a wind turbine 1 including an apparatus 10 for detecting one or more properties of a rotor blade 4 in accordance with embodiments of the invention.

[0056] More specifically, the wind turbine 1 comprises a tower 2, which is mounted on a non-depicted fundament. A nacelle 3 is arranged on top of the tower 2. In between the tower 2 and the nacelle 3 a yaw angle adjustment device (not shown) is provided, which is capable of rotating the nacelle around a vertical yaw axis Z. The wind turbine 1 further comprises a wind rotor 5 having one or more rotor blades 4 (in the perspective of FIG. 1 only two blades 4 are visible). The wind rotor 5 is rotatable around a rotational axis Y. In general, when not differently specified, the terms axial, radial and circumferential in the following are made with reference to the rotational axis Y. The rotor blades 4 extend radially with respect to the rotational axis Y. The wind turbine 1 comprises an electric generator 6 having a stator 11 and a rotor 12. The rotor 12 is rotatable with respect to the stator 11 about the rotational axis Y to generate electrical power. The electric generator 6 and the generation of electrical power through embodiments of the present invention is not a specific object of embodiments of the present invention and will therefore not be described in further detail.

[0057] The apparatus 10 for detecting one or more properties of the one or more rotor blades 4 during operation of the wind turbine comprises: at least one leaky feeder 20 arranged around a circumference of the tower (2), [0058] an electromagnetic transmitter 30 connected to the at least one leaky feeder 20, [0059] a reflector 35 for diverting and/or focusing electromagnetic signals leaked or emitted by the at least one leaky feeder 20, [0060] an electromagnetic receiver 40 connected to the least one leaky feeder 20, [0061] at least one final resistance/impedance 50 or termination connected to the least one leaky feeder 20, and [0062] a processing unit 300 connected to the electromagnetic transmitter 30 and the electromagnetic receiver 40.

[0063] The leaky feeder 20 is an elongate communication component, which leaks an electromagnetic wave that is transmitted along the component. The leaky feeder 20 may be constituted by a leaky coaxial cable or a leaky waveguide or a leaky strip line. The leaky feeder 20 is connected to an electromagnetic transmitter 30 in order to transmit a first electromagnetic signal 100 along the leaky feeder 20.

[0064] Referring also to FIG. 2, the leaky feeder 20 comprises a plurality of slots (not shown) that allow the first electromagnetic signal 100 to leak out of the leaky feeder 20 along its entire length towards the reflector and on towards the rotor blade 4 (target object). The slots may, according to possible embodiments, be regularly distributed along the length of the leaky feeder 20. According to other possible embodiments of the present invention, the leaky feeder 20 is a normal coaxial cable with low optical coverage of the outside conductor (mesh or slots/apertures), which also leaks electromagnetic waves.

[0065] The leaky feeder 20 may be provided with a heating system (not shown) in case severe over icing conditions are possible. Heating may be provided by air flowing between inside and outside conductors or by electrical current which runs in inner or outer conductors of the leaky feeder 20.

[0066] The first electromagnetic signal 100 may, according to possible embodiments, be a radar signal or an ultrasonic signal. In cases where the first electromagnetic signal 100 is a radar signal or an ultrasonic signal, the leaky feeder 20 may be configured as a coaxial leaky cable. According to other embodiments, particularly where the first electromagnetic signal 100 is of higher frequency, the leaky feeder 20 may be configured as a leaky waveguide.

[0067] In general, according to different embodiments of the present invention, the first electromagnetic signal 100 may be of any frequency, provided that it can be transmitted to the rotor blade 4 and be reflected by the reflector 35 and the rotor blade 4.

[0068] When the reflected first electromagnetic signal 100′ impinges on or hits the rotor blade 4, a reflected second electromagnetic signal 200 is transmitted towards the leaky feeder. The plurality of slots of the leaky feeder 20 allow the second electromagnetic signal 200 to leak into the leaky feeder 20 and propagate towards the electromagnetic receiver 40.

[0069] The reflector 35 is arranged in the vicinity of the leaky feeder 20 in order to divert and/or focus the first electromagnetic signal 100 leaked from the leaky feeder 20 in a predetermined direction towards a position, where the rotor blade 4 will be passing by. In other words, the reflector 35 forms a reflected (and focused) first electromagnetic signal 100′ which in turn is reflected by the rotor blade and back towards the leaky feeder 20 as the second electromagnetic signal 200. By focusing the leaked first electromagnetic signal 100, an improved signal to noise ratio may be obtained with less energy consumption. For this to work optimally, it is important to arrange the leaky feeder 20 and the reflector 35 in an appropriate spatial relation to each other such that leaky feeder 20 does not block or attenuate the reflected first electromagnetic signals 100′. Isolation between receiver (Rx) and transmitter (Tx) signals is improved as well.

[0070] The processing unit 300 analyses the first electromagnetic signal 100 and the second electromagnetic signal 200 for determining the properties of the rotor blade 4, such as position, speed, distance from tower, direction, size and soiling state of the rotor blade 4. According to known (radar) principles with regard to amplitude, phase, Doppler effect and ToF (Time of Flight), the processing unit 300 is able to compare the first electromagnetic signal 100 and the second electromagnetic signal 200 caused by a moving object (i.e., the rotor blade 4) and consequently to determine the speed and/or position and/or direction and/or size of such object. The position of the object may be an angle with respect to a rotational axis or the three-dimensional position with respect to a system of Cartesian axes.

[0071] As shown in FIG. 2, an embodiment of the apparatus 10 may comprise only one leaky feeder 20. The leaky feeder 20 extends between a first end 21 and a second end 22. The first end 21 is connected to an electromagnetic transmitter 30. The second end 22 is connected to an electromagnetic receiver 40. The apparatus 10 is used for detecting the position of a rotor blade 4 of the wind turbine 1. According to embodiments of the present invention, the positions of all the rotational blades 4 of the wind turbine 1 are detectable.

[0072] The leaky feeder 20 must not be connected directly to the electromagnetic transmitter 30 and to the electromagnetic receiver 40, e.g., a non-leaky feeder cable (i.e., a normal coaxial cable) may be interposed between the leaky feeder 20 and the electromagnetic transmitter 30 and/or the electromagnetic receiver 40. A normal coaxial cable may be connected directly to the electromagnetic transmitter 30 and to the electromagnetic receiver 40 or it may be used for interconnection.

[0073] According to other embodiments of the present invention, the target object may be the nacelle 2 for the detection of the position of the nacelle about the vertical yaw axis Z.

[0074] According to further embodiments of the present invention, other target objects may be detected in an area comprising a wind turbine 1, for example animals or intruders or changing waves (in offshore applications).

[0075] The leaky feeder 20 and reflector 35 of FIG. 2 are shown as rectilinear elements. Although rectilinear elements may be used, it should be understood that the leaky feeder 20 and reflector 35 may be geometrically configured as arcs or loops surrounding the circumference of the tower 2.

[0076] Such a configuration is shown in FIG. 3, where both the reflector 35 and the leaky feeder 20 are geometrically configured as concentric circular loops surrounding the tower 2. Here, the reflector 35 is arranged directly on the outer surface of the tower 2 and the leaky feeder is arranged with some distance to both the tower surface and the reflector 35. Generally, the reflector 35 and the leaky feeder 20 will be arranged at somewhat different heights in order to prevent that the leaky feeder 20 blocks the focused signal from the reflector 35.

[0077] According to other embodiments of the present invention, any other geometrical configuration is possible, provided that the first electromagnetic signal 100 can be transmitted towards the target object and the second electromagnetic signal 200 can be reflected by the target object towards the leaky feeder 20.

[0078] The leaky feeder 20, the electromagnetic transmitter 30, and the electromagnetic receiver 40 are installed on the tower 2.

[0079] According to other embodiments of the present invention, the leaky feeder 20, the electromagnetic transmitter 30, and the electromagnetic receiver 40 may not be directly installed on the wind turbine 1, but instead distanced from the wind turbine 1.

[0080] FIG. 4, FIG. 5, and FIG. 6 show various exemplary embodiments of a reflector 35. In the exemplary embodiment shown in FIG. 4, the leaky feeder 20 is arranged in a central focus point of the reflector 35. In the exemplary embodiment shown in FIG. 5, the leaky feeder 20 is arranged in an offset focus point of the reflector 35. In the exemplary embodiment of FIG. 6, a bi-focus arrangement is used where the leaky feeder 20 is arranged in a first focus point of the reflector 35 while a second focus point is positioned where the rotor blade 4 (or another object that is to be detected) is expected to pass by.

[0081] According to other embodiments of the present invention (not shown, the apparatus 10 may comprise a plurality of leaky feeders 20 with more than two leaky feeders 20. Such plurality of leaky feeders 20 comprising a first and a second group of leaky feeders 20 respectively connected to one or more electromagnetic transmitters 30 and to one or more electromagnetic receivers 40. Each of the plurality of leaky feeders 20 may be conveniently geometrically configured for optimally following the trajectories of the target objects or of a plurality of target objects.

[0082] 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.

[0083] 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.