A wind turbine blade surface icing status monitoring system and method

Abstract

The present invention discloses a wind turbine blade surface icing status monitoring system and method, belonging to the technical field of wind power generation. It includes a parallel surface laser generating system, a total reflection prism, a charge coupled element and a data processing and analysis system; the parallel surface laser generating system is arranged inside the blade root, the total reflection prism is embedded in the blade surface at the blade root, and the charge coupled element is arranged on the blade surface; the incident surface of the total reflection prism faces the parallel surface laser generating system, and the exit surface faces the charge coupled element; the charge coupled element is connected to the data processing and analysis system. The present invention can accurately monitor the initial stage of ice formation on the blade surface, that is, the thin ice formation stage, and can provide accurate start and stop signals for the operation of the wind turbine deicing system, and has good application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of wind power generation, and in particular relates to a system and method for monitoring the icing status of blade surfaces of a wind turbine generator set. Background Art

[0002] Many wind farms generally have serious freezing problems in winter and spring. The general characteristic of wind turbines being covered with ice is that the temperature is above -10℃. In the winter in southern regions, when the temperature drops to 0℃, ice will form on wind turbines and wind turbine blades. Blade icing changes the aerodynamic shape, weight distribution and frequency of the blades, breaks the load balance of the blades, and will cause problems such as vibration of the blades and wind rotors, which will have a direct impact on the operation, economy and safety of wind turbines.

[0003] When ice is deposited on the blades of a wind turbine, it is necessary to use methods such as hot air deicing and electric heating deicing to remove the ice on the blade surface to ensure the normal operation of the wind turbine under low temperature weather conditions. The intelligent deicing system for wind turbine blades needs to be based on the accurate prediction and monitoring of blade ice, and there is currently no particularly mature technology in this regard. Summary of the invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a wind turbine blade surface icing status monitoring system and method, which can accurately monitor the initial stage of icing on the blade surface, that is, the thin ice formation stage, and can provide accurate start and stop signals for the operation of the wind turbine deicing system.

[0005] The present invention is achieved through the following technical solutions:

[0006] The invention discloses a wind turbine blade surface icing state monitoring system, comprising a parallel surface laser generating system, a total reflection prism, a charge coupled device and a data processing and analysis system;

[0007] The parallel plane laser generating system is arranged inside the blade root, the total reflection prism is embedded in the blade surface at the blade root, and the charge coupled element is arranged on the blade surface; the incident surface of the total reflection prism faces the parallel plane laser generating system, and the exit surface faces the charge coupled element; the charge coupled element is connected to the data processing and analysis system.

[0008] Further preferably, the parallel surface laser generating system includes a laser emitter, an aperture filter, a convex lens, a concave prism and a surface laser filter; the laser emitter is arranged directly opposite the incident surface of the total reflection prism, and the aperture filter, the convex lens, the concave prism and the surface laser filter are arranged in sequence on the laser propagation path between the laser emitter and the incident surface of the total reflection prism.

[0009] Further preferably, the axis of the concave prism is placed horizontally, the plane of the concave prism faces the convex lens, and the arc surface faces the surface laser filter.

[0010] Further preferably, the aperture of the aperture filter is adjustable.

[0011] Further preferably, the surface laser filter includes a bracket, an upper baffle and a lower baffle; the bracket is fixed on the inner wall of the blade, the upper baffle and the lower baffle are movably connected to the bracket respectively, and the upper baffle and the lower baffle are made of opaque material.

[0012] Further preferably, a neutral density filter is provided between the surface laser filter and the incident surface of the total reflection prism.

[0013] Preferably, the height of the parallel plane laser emitted by the parallel plane laser generating system is 2 to 4 times the height of the charge coupled device.

[0014] Preferably, the data processing and analysis system comprises a signal processor and a computer, and the signal processor is connected to the charge coupled device and the computer respectively.

[0015] The method disclosed in the present invention for monitoring the icing state of blade surfaces of wind turbines using the above-mentioned blade icing state monitoring system comprises:

[0016] The parallel plane laser generating system emits a parallel plane laser, which changes direction after total reflection by a total reflection prism and irradiates the charge coupled device on the blade surface to form a line laser. When an ice layer is formed on the blade surface between the exit surface of the total reflection prism and the charge coupled device, the ice state is monitored and the maximum ice thickness is calculated based on the changes in the intensity and shape of the line laser on the charge coupled device.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects:

[0018] The present invention discloses a wind turbine blade surface icing status monitoring system. By measuring the laser intensity distribution of the line laser formed by the parallel plane laser emitted by the parallel plane laser generating system on the charge coupled element, the icing condition on the blade surface can be detected and the maximum thickness of the ice layer in the icing layer can be calculated. The parallel plane laser generating system is constructed inside the blade root, which is less affected (or can be ignored) by the yaw of the wind turbine blades and other operations; at the same time, the icing status can be monitored during the normal operation of the wind turbine. Combining the physical properties of laser and parallel plane laser, the sensitivity of the charge coupled element to the capture of laser intensity (spatial resolution is on the order of 10 to 100 um) and the recording, processing and analysis of the light intensity signal, combined with the high spatial resolution of the photodiode on the charge coupled element, the relatively small thickness of the icing layer can be captured. At the same time, the thickness of the icing layer can be accurately calculated according to the position of the change point of the laser intensity curve. Combined with the changes in the surface shape in the span direction of the blade, if the upper edge of the ice enters the propagation area of ​​the parallel plane laser on the propagation path of the parallel plane laser (the direct monitoring area in front of the non-charged coupled device), it can also be detected, thus realizing the monitoring of the ice coverage status over a longer area in the span direction of the blade.

[0019] The present invention can study the temporal development law of ice layer thickness, and provide a high-precision and accurate initial signal for the formulation of wind turbine deicing control strategy and the start or stop of the deicing system, which is beneficial to the efficient deicing of wind turbines and ensures the healthy, safe and reliable operation of wind turbines.

[0020] Furthermore, the parallel surface laser generating system has a simple structure through a laser emitter, an aperture filter, a convex lens, a concave prism and a surface laser filter, and can obtain the parallel surface laser required for monitoring.

[0021] Furthermore, the aperture of the aperture filter is adjustable, so that the beam cross-section of the laser after passing through the aperture filter is a circle of a set diameter, meeting monitoring requirements in different situations.

[0022] Furthermore, the surface laser filter has a simple structure, and the height of the surface laser can be easily adjusted by moving the upper baffle and the lower baffle to meet monitoring needs in different situations.

[0023] Furthermore, a dimming filter is provided between the surface laser filter and the incident surface of the total reflection prism, so as to prevent the charge coupled device from being damaged due to excessive intensity of the incident laser.

[0024] Furthermore, the height of the parallel plane laser emitted by the parallel plane laser generating system is 2 to 4 times the height of the charge coupled device, which can realize the monitoring of the ice coating state when the blade is slightly waving.

[0025] The method disclosed in the present invention for monitoring the icing status of blade surfaces using the above-mentioned wind turbine blade surface icing status monitoring system can accurately monitor the initial stage of icing on the blade surface, i.e., the thin ice formation stage, and can provide accurate start and stop signals for the operation of the wind turbine deicing system, thereby ensuring the healthy, safe and reliable operation of the wind turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a partial system schematic diagram of the present invention;

[0027] Figure 2 This is a schematic diagram of the ice monitoring system arranged on the blade surface;

[0028] Figure 3 A top view of the case where the laser is perpendicular to the incident surface of the ice layer and there is no gap between the ice layer and the charge coupled device;

[0029] Figure 4 This is a side view of the case where the laser is perpendicular to the incident surface of the ice layer and there is no gap between the ice layer and the charge coupled device;

[0030] Figure 5 It is a two-dimensional light intensity distribution diagram when the laser is perpendicular to the incident surface of the ice layer and there is no gap between the ice layer and the charge-coupled device;

[0031] Figure 6 A top view of the case where the laser is not perpendicular to the incident surface of the ice layer and there is no gap between the ice layer and the charge coupled device;

[0032] Figure 7 This is a side view of the case where the laser is not perpendicular to the incident surface of the ice layer and there is no gap between the ice layer and the charge coupled device;

[0033] Figure 8 It is a two-dimensional light intensity distribution diagram when the laser is not perpendicular to the incident surface of the ice layer and there is no gap between the ice layer and the charge-coupled device;

[0034] Fig. 9 A top view of the case where the laser is not perpendicular to the incident surface of the ice layer and there is a gap between the ice layer and the charge coupled device;

[0035] Fig.10 It is a side view of the case where the laser is not perpendicular to the incident surface of the ice layer and there is a gap between the ice layer and the charge coupled device;

[0036] Fig.11 It is a two-dimensional light intensity distribution diagram when the laser is not perpendicular to the incident surface of the ice layer and there is a gap between the ice layer and the charge-coupled device;

[0037] Fig.12 It is a schematic diagram of the distribution of the laser intensity of the parallel laser passing through the ice layer and not passing through the ice layer along the height direction of the charge coupled device;

[0038] Fig.13 Schematic diagram of the photodiode and line laser irradiation on the charge-coupled device.

[0039] In the figure: 1-blade; 2-blade root; 3-total reflection prism; 4-charge coupled device; 5-parallel surface laser; 6-laser transmitter; 7-aperture filter; 8-convex lens; 9-concave prism; 10-surface laser filter; 11-neutral density filter; 12-line laser; 13-signal processor; 14-computer; 15-ice layer; 16-photosensitive diode. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, the contents of which are intended to explain the present invention rather than to limit it:

[0041] The wind turbine blade surface icing state monitoring system of the present invention arranges a laser and a parallel surface laser generating system in a relatively large area inside the blade root 2 of the wind turbine blade 1. Figure 2 As shown, the laser emitter 6 emits a laser beam of a specific wavelength and a stable intensity, which serves as a light source for monitoring ice on the surface of the blade 1. The cross section of the laser beam output by the laser emitter 6 is not absolutely circular. In order to eliminate the adverse effects of the beam cross section shape on downstream measurements, an aperture filter 7 is arranged downstream of the laser emitter 6. The structure of the aperture filter 7 is similar to the aperture of a camera, and the diameter of the light-transmitting circular hole in the center thereof can be adjusted, so that the beam cross section of the laser after passing through the aperture filter 7 is a circle with a set diameter.

[0042] The circular laser beam is converged to the charge-coupled device 4 arranged perpendicularly to the surface of the wind turbine blade 1 through the convex lens 8. The focal length of the convex lens 8 depends on the relative distance between the laser platform and the ice monitoring position, that is, the distance between the center of the convex lens 8 and the charge-coupled device 4 is its focal length f1. An optical element needs to be set between the convex lens 8 and the charge-coupled device 4 to form a parallel surface laser 5 perpendicular to the surface of the blade 1 and with a fixed height. In the direction parallel to the surface of the blade 1, the cross-sectional height of the parallel surface laser 5 gradually decreases, and finally converges on the charge-coupled device 4 to form a line laser 12.

[0043] A concave prism 9 is placed behind the convex lens 8, with its axis parallel to the span direction of the blade 1. One side of the concave prism 9 is arc-shaped, and the other side is flat. The laser beam enters from the center of the concave prism 9 and forms a fan-shaped laser on the other side. The angle of the fan-shaped laser depends on the focal length of the concave prism 9: the smaller the focal length, the narrower the fan-shaped laser, that is, the less likely it is to diverge.

[0044] A surface laser filter 10 is arranged at an appropriate position behind the concave prism 9. The surface laser filter 10 is composed of two stainless steel baffles with smooth and sharp edges that can be moved up and down. The fan-shaped surface laser passes through the baffles to form an approximately parallel surface laser 5. (The distance between the laser filter 10 and the charge coupled device 4 can be considered as a parallel surface laser 5 with a constant height).

[0045] Since the charge coupled device 4 is relatively sensitive to light intensity, its photosensitive element, the photodiode 16, has a limited range of measuring light intensity. In order to avoid damage caused by excessive intensity of the incident laser, a neutral density filter 11 with appropriate light transmittance can be set in front of it to greatly reduce the light intensity density of the parallel plane laser 5 passing through the neutral density filter 11, so that it can be captured smoothly and safely by the charge coupled device 4.

[0046] according to Figure 1 The parallel plane laser 5 formed as shown and parallel to the chord direction of the blade 1 needs to change the propagation direction through the total reflection prism 3 embedded in the blade 1 at the blade root 2. The cross section of the total reflection prism 3 is an isosceles right triangle, and the 90° direction change can be achieved by using the total reflection principle of light. Compared with the size of the blade root 2, the total reflection prism 3 is much smaller. By embedding it in the blade 1 material at the blade root 2, the influence on the structure and aerodynamic performance of the blade 1 can be ignored.

[0047] The parallel plane laser 5 redirected by the total reflection prism 3, within a specific distance before reaching the charge coupled device 4 (the ice coverage monitoring area on the surface of the blade 1), the lower part of the parallel plane laser 5 is close to the surface of the blade 1, that is, between the total reflection prism 3 and the charge coupled device 4, the lower part of the parallel plane laser 5 is not blocked by the surface shape of the blade 1 in front of the ice coverage monitoring area.

[0048] like Figure 2 and Figure 5 As shown, the height of the parallel laser 5 is 2 to 4 times the height of the charge coupled device 4, which can realize the ice coating state monitoring when the blade 1 is slightly waving.

[0049] The charge coupled device 4, also known as CCD, is a widely used digital camera image sensor. It is composed of a certain number of photodiodes 16 arranged evenly, such as Figure 5 , the photodiodes 16 are closely arranged and extremely small in size. From a macroscopic point of view, each photodiode 16 can be understood as a single point (referred to as a pixel). The photodiode 16 senses light, converts the light intensity into a digital signal, and transmits it to the computer 14 for storage and analysis after being processed by the signal processor 13. By setting the sensitivity and the light measurement intensity range of the charge coupled element 4, weaker light such as sunlight can be processed as background light, and the laser intensity far exceeding the background light can be accurately captured.

[0050] like Figure 5As shown, the charge coupled element 4 is composed of M×N photosensitive diodes 16, and its output data is transmitted to the computer 14 and processed into an M×N data matrix. The value of each element in the matrix is ​​proportional to the measured light intensity of the corresponding photosensitive diode 16. By plotting a two-dimensional graph of the data matrix, a cloud graph of the light intensity distribution on the charge coupled element 4 can be obtained. Figures 3 to 11 On the two-dimensional light intensity cloud map, you can intuitively see the location where the laser appears and the laser intensity (thickness).

[0051] In the ice-covering monitoring area of ​​the blade, since ice-covering is always formed gradually from an ice-free state, the ice-covering state can be determined and monitored by recording, processing and determining the intensity distribution state of the line laser 12 .

[0052] Figures 3 to 11 Several typical situations of parallel laser 5 passing through ice layer 15 in front of charge coupled device 4 are shown:

[0053] 1) If Figures 3 to 5 , the ice layer 15 is formed in front of the charge coupled device 4 (without a gap in the middle), and the laser is perpendicular to the parallel plane laser 5 on the incident surface of the ice layer. The laser is not refracted in the ice layer 15, and the absorption of the laser by the ice layer 15 will cause the corresponding laser intensity to weaken, that is, the laser intensity distribution of the entire line laser 12 will present a line segment + strong at the top and weak at the bottom, as shown in FIG. Figure 4 According to the position of the laser intensity segmentation point and the pixel size of the charge coupled device 4, the thickness of the ice layer 15 can be inferred.

[0054] 2) If Figures 6 to 8 , the ice layer 15 is formed in front of the charge coupled device 4 (without a gap in the middle), and the laser is not perpendicular to the parallel surface laser 5 on the incident surface of the ice.

[0055] 3) If Figures 9-11 There is an air gap between the ice layer 15 and the charge coupled device 4. The laser incident surface and the laser emission surface of the ice layer 15 are irregular (in the natural environment, it is difficult to form a similar Figures 3 to 5 Each of the regular ice surfaces is parallel to the charge coupled device 4.

[0056] For the above cases 2) and 3), the laser will be reflected on the ice surface, refracted and reflected (or totally reflected) inside the ice layer 15 at the incident surface and inside the ice layer 15. On the one hand, the various optical behaviors of the laser passing through the ice layer 15 cause the laser position captured by the charge coupled element 4 to deviate to the left or right from the laser position without ice blocking the upper part, and due to the reflection on the ice surface and the absorption of the ice layer, the intensity of this part of the laser intensity is reduced (or the intensity is zero due to total reflection of the laser). According to the position of the change point of the laser intensity curve, the maximum thickness of the ice layer 15 can be determined, that is, the position of the deviation point in the laser intensity matrix (such as the i-th row) is determined. The maximum thickness of the ice layer 15 is (Mj)×h, where h is the spatial distance corresponding to a single pixel (equal to the height of the charge coupled element 4 divided by M rows).

[0057] Figures 3 to 11 and Fig.12 The situation where only a single ice layer appears in the ice detection area is described. In the actual operation of the wind turbine, ice may appear at the same time, that is, there is more than one ice layer in the ice detection area. After the parallel plane laser 5 passes through the first ice layer, the laser passes through the ice layer again and may capture a more complex laser intensity distribution on the charge-coupled element 4. However, in general, the complex laser intensity distribution appears more in the range of the maximum thickness mapping of the ice layer 15. For the upper part of the parallel plane laser 5 without ice cover and captured by the charge-coupled element 4, its intensity distribution characteristics can be predicted, that is, it should be a line segment with constant intensity on the laser intensity cloud map, and the bottom of the line segment is regarded as the change point of the laser intensity curve. Within the ice detection range, regardless of whether there is a single or multiple ice layers, what shape, and whether it is in direct contact with the charge-coupled element 4, the ice state can be monitored and the maximum ice thickness can be calculated.

[0058] It should be noted that the above is only a part of the implementation of the present invention, and equivalent changes made to the system described in the present invention are all included in the protection scope of the present invention. Those skilled in the art of the present invention can replace the specific examples described in a similar manner, as long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they all belong to the protection scope of the present invention.

Claims

1. A method for monitoring the icing status of blade surfaces of wind turbines using a blade surface icing status monitoring system, characterized in that: The system comprises a parallel-plane laser generating system, a total reflection prism (3), a charge-coupled device (4) and a data processing and analysis system; The parallel-plane laser generating system is arranged inside the blade root (2); the total reflection prism (3) is embedded in the surface of the blade (1) at the blade root (2); and the charge-coupled element (4) is arranged on the surface of the blade (1); the incident surface of the total reflection prism (3) faces the parallel-plane laser generating system, and the exit surface faces the charge-coupled element (4); the charge-coupled element (4) is connected to the data processing and analysis system; The parallel surface laser generating system comprises a laser emitter (6), an aperture filter (7), a convex lens (8), a concave prism (9) and a surface laser filter (10); the laser emitter (6) is arranged directly opposite to the incident surface of the total reflection prism (3); the aperture filter (7), the convex lens (8), the concave prism (9) and the surface laser filter (10) are arranged in sequence on the laser propagation path between the laser emitter (6) and the incident surface of the total reflection prism (3); The axis of the concave prism (9) is placed horizontally, the plane of the concave prism (9) faces the convex lens (8), and the arc surface faces the surface laser filter (10); The surface laser filter (10) comprises a bracket, an upper baffle and a lower baffle; the bracket is fixed on the inner wall of the blade (1), the upper baffle and the lower baffle are respectively movably connected to the bracket, and the upper baffle and the lower baffle are made of opaque material; The data processing and analysis system comprises a signal processor (13) and a computer (14), wherein the signal processor (13) is connected to the charge coupled device (4) and the computer (14) respectively; The method comprises: The parallel surface laser generating system emits parallel surface laser (5), which changes direction after being totally reflected by a total reflection prism (3) and irradiates a charge coupled device (4) on the surface of a blade (1), thereby forming a line laser (12); when an ice layer (15) is formed on the surface of the blade (1) between the exit surface of the total reflection prism (3) and the charge coupled device (4), the ice state is monitored and the maximum ice thickness is calculated according to the changes in the intensity and shape of the line laser (12) on the charge coupled device (4).

2. The method for monitoring the icing status of blade surfaces using a wind turbine blade surface icing status monitoring system according to claim 1, characterized in that: The aperture of the aperture filter (7) is adjustable.

3. The method for monitoring the icing status of blade surfaces using a wind turbine blade surface icing status monitoring system according to claim 1, characterized in that: A dimming mirror (11) is provided between the surface laser filter (10) and the incident surface of the total reflection prism (3).

4. The method for monitoring the icing status of blade surfaces using a wind turbine blade surface icing status monitoring system according to claim 1, characterized in that: The height of the parallel plane laser (5) emitted by the parallel plane laser generating system is 2 to 4 times the height of the charge coupled device (4).

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