A wind turbine blade icing monitoring system and method based on capacitance measurement

Abstract

The present invention discloses a wind turbine blade icing monitoring system and method based on capacitance measurement, which belongs to the technical field of wind power generation. It includes a sinusoidal signal power supply, a data processing system, a computer and a plurality of parallel plate capacitors; the parallel plate capacitors are arranged at both ends of the icing monitoring area on the blade surface and are perpendicular to the blade surface; the sinusoidal signal power supply is respectively connected to the data processing system and each power supply electrode plate, and each grounding electrode plate is respectively grounded; a voltage dividing resistor is provided between the sinusoidal signal power supply and each power supply electrode plate, a voltage measuring point is provided between the voltage dividing resistor and the power supply electrode plate, the voltage measuring point is connected to the data processing system, and the data processing system is connected to the computer. The present invention realizes the effective monitoring of the formation and development of icing on the blade surface in the target area, and can provide sensitive and accurate control signals for the start or stop of the blade anti-icing control system of the wind turbine.

Description

Technical Field

[0001] The present invention belongs to the technical field of wind power generation, and in particular relates to a wind turbine blade icing monitoring system and method based on capacitance measurement. Background Art

[0002] Wind farms in low wind speed areas and some high wind speed areas in the south 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 the south, when the temperature drops to 0℃, ice will appear 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 appears 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. For example, if thin ice on the blade surface can be detected, the deicing system will start running at a lower power, which can effectively remove ice and reduce the energy consumption of the deicing system. It has a significant effect on the intelligent operation and economic improvement of the entire deicing system. Therefore, how to accurately predict and monitor blade ice is a problem that needs to be solved urgently. 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 icing monitoring system and method based on capacitance measurement. The system has a simple structure and can effectively monitor the formation and development of ice on the blade surface in the target area, and can provide sensitive and accurate control signals for starting or stopping the blade anti-icing control system of the wind turbine.

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

[0006] The invention discloses a wind turbine blade icing monitoring system based on capacitance measurement, comprising a sinusoidal signal power supply, a data processing system, a computer and a plurality of parallel plate capacitors; the parallel plate capacitor comprises a power supply electrode plate and a grounding electrode plate, the power supply electrode plate and the grounding electrode plate are of the same size, and are arranged in parallel at both ends of an icing monitoring area on a blade surface and are perpendicular to the blade surface; all the power supply electrode plates in the plurality of parallel plate capacitors are arranged in sequence in a height direction, and adjacent power supply electrode plates are connected by an insulating plate; all the grounding electrode plates are arranged in sequence in a height direction, and adjacent grounding electrode plates are connected by an insulating plate;

[0007] The sinusoidal signal power supply is respectively connected to the data processing system and each power electrode plate, and each grounding electrode plate is respectively grounded; a voltage dividing resistor is arranged between the sinusoidal signal power supply and each power electrode plate, a voltage measuring point is arranged between the voltage dividing resistor and the power electrode plate, the voltage measuring point is connected to the data processing system, and the data processing system is connected to the computer.

[0008] Preferably, the data processing system includes a rectifier detector, a low-pass filter and an A / D converter, one end of the rectifier detector is connected to the voltage measuring point, and the other end is connected to the low-pass filter, the low-pass filter is connected to the A / D converter, and the A / D converter is connected to the computer.

[0009] Preferably, the power supply electrode plate and the ground electrode plate have a thickness of 1 to 1.5 mm and a height of 3 to 5 mm.

[0010] Further preferably, the thickness and length of the insulating plate are equal to those of the power supply electrode plate and the grounding electrode plate, and the height is 1 to 1.5 mm.

[0011] Preferably, the distance between the power supply electrode plate and the ground electrode plate is 5-10 mm.

[0012] Preferably, the number of parallel plate capacitors is ≥2.

[0013] Preferably, the computer is interconnected and communicates with the wind turbine blade anti-icing control system via a wireless communication module.

[0014] Preferably, the sinusoidal signal power supply, the data processing system, the computer, the voltage dividing resistor and the voltage measuring point are all arranged in the blade root.

[0015] The present invention discloses a method for monitoring ice coating on fan blades using the above-mentioned fan blade ice coating monitoring system based on capacitance measurement, comprising:

[0016] The sinusoidal signal power supply outputs sinusoidal alternating current through a voltage-dividing resistor to the power electrode plate of each parallel plate capacitor, the grounding electrode plate is grounded, and the voltage measuring point collects the terminal voltage of each parallel plate capacitor, which is sent to the computer after being processed by the data processing system; the computer monitors the ice covering the surface of the wind turbine blades according to the changing trend of the terminal voltage of the parallel plate capacitor.

[0017] Preferably, the plurality of parallel plate capacitors include a first capacitor and a second capacitor, the bottom surface of the first capacitor is connected to the blade, the second capacitor is arranged on the top of the first capacitor through an insulating plate, and the computer collects the output voltage of the sinusoidal signal power supply The terminal voltage of the first capacitor and the terminal voltage of the second capacitor And draw the time development curve respectively, and extract and The amplitude A of each sine wave in the time development curve 1c With A 2c ,as well as and The time development curve of The phase difference of the time development curve and Comprehensive monitoring of ice coverage on blade surfaces can be divided into the following situations:

[0018] 1) If and The time development curve of 1c With A 2c And the phase difference and The medium between the first capacitor and the second capacitor is air, and no ice is formed on the blade surface;

[0019] 2) If The time development curve of The time development curve of The amplitude of the time development curve A 1c and phase difference become smaller, and The amplitude of the time development curve A 2c and phase difference The ice layer remains unchanged, and ice appears between the power electrode plate and the ground electrode plate of the first capacitor, and the maximum height of the ice layer is lower than the height of the power electrode plate and the ground electrode plate of the first capacitor, that is, the ice layer only exists in the space between the power electrode plate and the ground electrode plate of the first capacitor;

[0020] 3) If and The time development curves of the capacitors all show waveform changes. At this time, ice is formed between the first capacitor and the second capacitor. Specifically:

[0021] 3.1) If and The amplitude of the time development curve A 1c With A 2c and phase difference and Both show a continuous downward trend. At this time, the ice grows in the height direction perpendicular to the blade surface. Ice appears between the first capacitor and the second capacitor, but neither is full of ice.

[0022] 3.2) If The amplitude of the time development curve A 1c and phase difference After decreasing, it tends to be stable. The amplitude of the time development curve A 1c and phase difference It still shows a trend of decreasing. At this time, the first capacitor is full of ice, while the second capacitor has ice but is not full of ice.

[0023] 3.3) If and The amplitude of the time development curve A 1c With A 2c and phase difference and Both tend to be stable, and the two time development curves are close to overlapping again. At this time, the first capacitor and the second capacitor are full of ice, and the height of the ice layer is not less than the total height of the first capacitor, the insulating plate and the second capacitor.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects:

[0025] The present invention discloses a wind turbine blade icing monitoring system based on capacitance measurement, wherein a plurality of parallel plate capacitors perpendicular to the blade surface are constructed on the blade surface, and the power supply electrode plates and the grounding electrode plates in the plurality of parallel plate capacitors are connected by insulators. The parallel plate capacitors do not interfere with each other, thereby improving the accuracy of segmented monitoring of icing formation and development, and are generally similar to a large capacitor. A parallel RC resonant circuit is constructed for each parallel plate capacitor based on the same sinusoidal signal power supply. The capacitance value depends only on the medium between the parallel electrode plates. Since the relative dielectric constants of air and ice are quite different (1 and 3 to 4, respectively), the change in capacitance value after icing in the electrode plates is significantly affected, thereby improving the accuracy of icing monitoring judgment in the downstream of the system. By monitoring the terminal voltage of each capacitor and processing it by a data processing system, the computer monitors the icing on the surface of the wind turbine blade according to the change trend of the terminal voltage of the parallel plate capacitor. The whole monitoring system is simple. The setting of multiple parallel plate capacitors can monitor the growth of ice in different directions parallel and perpendicular to the blade surface, realizing effective monitoring of the formation and development of ice on the blade surface in the target area, and providing sensitive and accurate control signals for the start or stop of the wind turbine blade anti-icing control system. At the same time, the power supply electrode plate and the grounding electrode plate of the parallel plate capacitor are small in height, and have little overall impact on the aerodynamic performance of the blade. Similar to a vortex generator, it is beneficial to suppress the movement of airflow in the span direction of the blade (similar to adding a cascade on the blade surface), improving the stability of airflow on the blade surface and the performance of the blade.

[0026] Furthermore, the power supply electrode plate and the grounding electrode plate have a height of 3 to 5 mm, which enables accurate monitoring when ice and de-icing are initially formed, with high sensitivity.

[0027] Furthermore, when ice is just beginning to form, the thickness of the ice film is small, so the corresponding size of the corresponding electrode plate is relatively small. If it is too large, a small ice layer will appear between the electrode plates, which may have little effect on the change of the capacitance value and low sensitivity.

[0028] Furthermore, the number of parallel plate capacitors is ≥2 and can be set according to actual needs. By constructing multiple independent capacitors, each capacitor can measure the ice coverage within the corresponding height range. If the size of a single capacitor is too large, it will affect the detection effect. Multiple capacitors are independently stacked to test the thickness of ice.

[0029] Furthermore, except for a number of parallel plate capacitors arranged on the surface of the blade, the rest of the capacitors in the system are arranged in a larger space in the blade root, which will not increase the weight of the blade and will not affect the performance of the blade.

[0030] The method disclosed in the present invention for monitoring wind turbine blade icing using the above-mentioned capacitance-measurement-based wind turbine blade icing monitoring system has a high degree of automation, realizes effective monitoring of the formation and development of ice on the blade surface in the target area, and can provide sensitive and accurate control signals for starting or stopping the blade anti-icing and de-icing control system of the wind turbine generator set.

[0031] Furthermore, by monitoring the voltage across the parallel plate capacitor and performing changes in the amplitude and phase difference of the voltage sine function, icing judgment is made. The development of icing on the blade surface corresponding to different changing characteristics of the amplitude and phase difference is proposed, and the icing monitoring sensitivity is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the overall structure of the system of the present invention;

[0033] Figure 2 for Figure 1 A partial enlarged view of;

[0034] Figure 3 Schematic diagram of the dimensions of the electrode plate and the insulating plate.

[0035] In the figure: 1 is a sinusoidal signal power supply; 2 is a voltage measuring point; 3 is a first voltage-dividing resistor; 4 is a second voltage-dividing resistor; 5 is a first electrode plate; 6 is a second electrode plate; 7 is a third electrode plate; 8 is a fourth electrode plate; 9 is a first insulating plate; 10 is a second insulating plate; 11 is a blade; 12 is a blade root; 13 is a rectifier detector; 14 is a low-pass filter; 15 is an A / D converter; 16 is a computer; 17 is a first capacitor; 18 is a second capacitor. DETAILED DESCRIPTION

[0036] 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:

[0037] like Figure 1 The wind turbine blade icing monitoring system based on capacitance measurement of the present invention constructs a parallel plate capacitor on the blade surface of the wind turbine blade (11) where icing detection / monitoring is required. This embodiment is described with two capacitors. If three or more capacitors are required, the principle is the same.

[0038] like Figure 2 The first capacitor 17 located at the bottom and directly fixedly connected to the surface of the blade 11 is composed of a first electrode plate 5 and a second electrode plate 6 arranged in parallel and of the same size, and the second capacitor 18 is also composed of a third electrode plate 7 and a fourth electrode plate 8 arranged in parallel and of the same size. The first electrode plate 5 and the third electrode plate 7 are not directly connected, but are connected with a first insulating plate 9 in the middle. Similarly, a second insulating plate 10 is connected between the second electrode plate 6 and the fourth electrode plate 8, that is, two adjacent but independent parallel plate capacitors are constructed.

[0039] like Figure 3 The electrode plates and insulating plates of the two parallel plate capacitors have the same thickness W and length L, and the thickness W is about 1 mm. In the height direction, the heights h1 and h3 of the electrode plates remain the same. Since accurate monitoring and feedback signals to the anti-icing control system of the wind turbine are required when the ice is initially formed, h1 and h3 can be selected within the range of 3 to 5 mm. For such a small capacitor, the height h2 of the insulating plate can be 1 mm. The spacing d of the electrode plates can be selected to be 5 to 10 mm.

[0040] Two independent RC series resonant circuits are constructed based on the above two parallel plate capacitors. For the first capacitor 17, the wires are connected to the first electrode plate 5 and the second electrode plate 6 respectively, and then pass through the blade 11 and are fixed along the inner surface of the blade 11 and guided to the blade root 12 of the blade. The connecting wire of the second electrode plate 6 is grounded, and a sinusoidal signal power supply 1 is fixed in the blade root 12. A first voltage-dividing resistor 3 is connected to a suitable position between the first capacitor 17 and the sinusoidal signal power supply 1 by a wire, and the first voltage-dividing resistor 3 is fixed on the inner surface of the blade root 12. Similarly, an RC series circuit is constructed between the third electrode plate 7, the fourth electrode plate 8, the second voltage-dividing resistor 4 and the sinusoidal signal power supply 1.

[0041] A voltage measuring point 2 of the first capacitor 17 is set between the first voltage-dividing resistor 3 and the first electrode plate 5, and a voltage measuring point 2 of the second capacitor 18 is set between the second voltage-dividing resistor 4 and the third electrode plate 7, which are respectively connected to different channels of the rectifier detector 13. The monitoring voltage signal passes through the low-pass filter 14 and the A / D converter 15 and then enters the computer 16 for storage and analysis.

[0042] For the monitoring circuit of the first capacitor 17, the terminal voltage U 1c have:

[0043]

[0044]

[0045]

[0046]

[0047]

[0048] Where: X 1c is the impedance of the first capacitor 17, w and They are the frequency and initial phase of the output voltage of sinusoidal signal power supply 1 respectively.

[0049] For a parallel plate capacitor, the capacitance C1 of the first capacitor 17 is:

[0050]

[0051] Where: r1 is the relative dielectric constant of the medium between the first electrode plate 5 and the second electrode plate 6, and k is the electrostatic force constant. From the above formula, it can be seen that when the size of the parallel electrode plate is determined, its capacitance value only changes with the relative dielectric constant ε r change.

[0052] For the second capacitor 18, we also have:

[0053]

[0054]

[0055]

[0056]

[0057] Among them, ε r2 is the relative dielectric constant of the medium between the third electrode plate 7 and the fourth electrode plate 8. The resistance value of the first voltage-dividing resistor 3 is the same as that of the second voltage-dividing resistor 4, that is, R1=R2.

[0058] From the above formula, we can see that when ice appears between the capacitor's electrode plates, the relative dielectric constant of the medium will change from pure air (ε r =1) transition to pure ice (ε r =3~4), the appearance of ice increases the capacitance value, resulting in the terminal voltage (U 1c or U2c ) decreases, and the power supply output voltage The phase difference ( or ) becomes smaller.

[0059] Combination Figure 1 It can be seen that the computer 16 collects and records the output voltage of the sinusoidal signal power supply 1 The terminal voltage of the first capacitor 17 and the terminal voltage of the second capacitor 18 Draw the time development curves of these three signals respectively and extract and The amplitude of each sine wave (A 1c With A 2c ),as well as and Curve and The phase difference of the curve ( and ), comprehensively monitor the ice coverage on the blade surface:

[0060] 1. If and The time development curves of (almost) coincide with each other, that is, the amplitude A 1c With A 2c And the difference and It remains unchanged, indicating that the medium between the electrode plates of the two capacitors is air and there is no ice formed on the blade surface.

[0061] 2. If The time development curve of The curve did not change, that is Curve A 1c and become smaller, and The amplitude and phase of the curve remain unchanged, indicating that ice has appeared in the electrode plate of the first capacitor 17 attached to the blade surface, and the maximum height of the ice layer is lower than the height h3 of the first electrode plate 5, that is, the ice only exists in the electrode plate space of the first capacitor 17.

[0062] 3. If and The time development curves of both capacitors show waveform changes, indicating that ice has appeared in the electrode plate space of the two capacitors. Specifically:

[0063] 3.1 If and The amplitude of the curve (A 1c With A 2c ) and phase difference ( and ) show a continuous downward trend, indicating that the ice grows in the height direction perpendicular to the blade surface, resulting in ice appearing in the electrode plate spaces of the two capacitors, but the electrode plate spaces of the two capacitors are not filled with ice;

[0064] 3.2 If The amplitude of the curve (A 1c ) and phase difference After decreasing, it tends to be stable. The amplitude of the curve (A 1c ) and phase difference It still shows a decreasing trend, indicating that the parallel plate space of the first capacitor 17 is filled with ice, while ice appears in the second capacitor (18), but does not fill the parallel plate space;

[0065] 3.3 If and The amplitude of the curve (A 1c With A 2c ) and phase difference ( and ) tend to be stable, and the two curves are close to coincidence again, indicating that both electrode plates are full of ice, and the height of the ice layer is not less than the total height of the capacitor and the insulating plate (h1+h2+h3).

[0066] After analyzing and monitoring the signals of ice formation and development, the computer 16 can transmit the relevant data to the anti-icing system of the wind turbine generator set by wireless transmission, and provide a start-stop signal for starting or stopping the system.

[0067] 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 ice coating on fan blades using a fan blade ice coating monitoring system based on capacitance measurement, characterized in that: The system comprises: a sinusoidal signal power supply (1), a data processing system, a computer (16), and a plurality of parallel plate capacitors; the parallel plate capacitors comprise a power supply electrode plate and a grounding electrode plate, the power supply electrode plate and the grounding electrode plate having the same size and being arranged in parallel at both ends of an ice cover monitoring area on the surface of a blade (11) and being perpendicular to the surface of the blade (11); all the power supply electrode plates in the plurality of parallel plate capacitors are arranged in sequence in the height direction, and adjacent power supply electrode plates are connected via an insulating plate; all the grounding electrode plates are arranged in sequence in the height direction, and adjacent grounding electrode plates are connected via an insulating plate; The sinusoidal signal power supply (1) is respectively connected to the data processing system and each power supply electrode plate, and each grounding electrode plate is respectively grounded; a voltage dividing resistor is provided between the sinusoidal signal power supply (1) and each power supply electrode plate, a voltage measuring point (2) is provided between the voltage dividing resistor and the power supply electrode plate, the voltage measuring point (2) is connected to the data processing system, and the data processing system is connected to the computer (16); The method comprises the following steps: The sinusoidal signal power supply (1) outputs sinusoidal alternating current through a voltage dividing resistor to the power electrode plate of each parallel plate capacitor, the grounding electrode plate is grounded, and the voltage measuring point (2) collects the terminal voltage of each parallel plate capacitor and sends it to the computer (16) after being processed by the data processing system; the computer (16) monitors the ice coating on the surface of the fan blade according to the change trend of the terminal voltage of the parallel plate capacitor; The plurality of parallel plate capacitors include a first capacitor (17) and a second capacitor (18), wherein the bottom surface of the first capacitor (17) is connected to the blade (11), and the second capacitor (18) is arranged on the top of the first capacitor (17) through an insulating plate. The computer (16) collects the output voltage of the sinusoidal signal power supply (1). , the terminal voltage of the first capacitor (17) and the terminal voltage of the second capacitor (18) And draw the time development curve respectively, and extract and The amplitude A of each sine wave in the time development curve 1c With A 2c ,as well as and The time development curve of The phase difference of the time development curve and , comprehensively monitor the ice coverage on the blade (11) surface, which is divided into the following situations: 1) If and The time development curve of 1c With A 2c And the phase difference and remains unchanged, at which time the medium between the first capacitor (17) and the second capacitor (18) is air, and no ice is formed on the surface of the blade (11); 2) If The time development curve of The time development curve of The amplitude of the time development curve A 1c and phase difference become smaller, and The amplitude of the time development curve A 2c and phase difference remains unchanged, at which time ice appears between the power electrode plate and the ground electrode plate of the first capacitor (17), and the maximum height of the ice layer is lower than the height of the power electrode plate and the ground electrode plate of the first capacitor (17), that is, the ice only exists in the space between the power electrode plate and the ground electrode plate of the first capacitor (17); 3) If and The time development curves of the capacitors 17 and 18 all show waveform changes. At this time, ice is formed between the first capacitor (17) and the second capacitor (18). Specifically: 3.1) If and The amplitude of the time development curve A 1c With A 2c and phase difference and Both show a trend of continuous downward change, at which time the ice grows in a height direction perpendicular to the surface of the blade (11), and ice appears between the first capacitor (17) and the second capacitor (18), but neither is fully covered with ice; 3.2) If The amplitude of the time development curve A 1c and phase difference After decreasing, it tends to be stable. The amplitude of the time development curve A 1c and phase difference Still showing a trend of decreasing, at this time, the first capacitor (17) is full of ice, while the second capacitor (18) has ice but is not full of ice; 3.3) If and The amplitude of the time development curve A 1c With A 2c and phase difference and Both tend to be stable, and the two time development curves are close to overlapping again. At this time, the first capacitor (17) and the second capacitor (18) are both filled with ice, and the height of the ice layer is not less than the total height of the first capacitor (17), the insulating plate and the second capacitor (18).

2. The method for monitoring wind turbine blade icing using a wind turbine blade icing monitoring system based on capacitance measurement according to claim 1, characterized in that: The data processing system comprises a rectifier detector (13), a low-pass filter (14) and an A / D converter (15); one end of the rectifier detector (13) is connected to the voltage measuring point (2), and the other end is connected to the low-pass filter (14); the low-pass filter (14) is connected to the A / D converter (15); and the A / D converter (15) is connected to a computer (16).

3. The method for monitoring wind turbine blade icing using a wind turbine blade icing monitoring system based on capacitance measurement according to claim 1, characterized in that: The thickness of the power supply electrode plate and the grounding electrode plate is 1-1.5 mm, and the height is 3-5 mm.

4. The method for monitoring wind turbine blade icing using a wind turbine blade icing monitoring system based on capacitance measurement according to claim 3 is characterized in that: The thickness and length of the insulating plate are equal to those of the power supply electrode plate and the grounding electrode plate, and the height is 1-1.5 mm.

5. The method for monitoring wind turbine blade icing using a wind turbine blade icing monitoring system based on capacitance measurement according to claim 1, characterized in that: The distance between the power supply electrode plate and the grounding electrode plate is 5-10 mm.

6. The method for monitoring wind turbine blade icing using a wind turbine blade icing monitoring system based on capacitance measurement according to claim 1, characterized in that: The number of parallel plate capacitors is ≥ 2.

7. The method for monitoring wind turbine blade icing using a wind turbine blade icing monitoring system based on capacitance measurement according to claim 1, characterized in that: The computer (16) is interconnected and communicates with the wind turbine blade anti-icing control system via a wireless communication module.

8. The method for monitoring wind turbine blade icing using a wind turbine blade icing monitoring system based on capacitance measurement according to claim 1, characterized in that: The sinusoidal signal power supply (1), the data processing system, the computer (16), the voltage dividing resistor and the voltage measuring point (2) are all arranged in the blade root (12).

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