CN103278512A - Device and method for online detection on structural damage of solar panel by utilizing microwaves - Google Patents

Abstract

A device and method for using microwaves to detect solar panel structural damage on-line. The active microwave resonant cavity of the device includes a vector network analyzer, a frequency scanning source, a first isolator, a first adjuster and a resonant cavity connected in sequence; The microwave signal processing system includes a coupling probe placed in the resonant cavity, an attenuator, a second adjuster, a second isolator and a signal microprocessor circuit that are sequentially connected to the coupling probe; the method is: through the resonant cavity The microwave signal enters the surface of the solar panel under test, part of it is absorbed and reflected, and part of it penetrates the panel to the metal background and produces full emission. The echo signal is picked up by the coupling probe, and the echo signal is obtained by the signal microprocessor circuit in real time. The frequency offset Δf of the resonant cavity can know the structural damage degree of the tested solar battery panel; the invention can realize real-time online monitoring of the solar battery panel damage and meet the requirements for non-destructive testing of solar battery panels on the production line.

Description

A device and method for online detection of solar panel structural damage using microwaves

technical field

The invention relates to the technical field of solar panel structure damage detection, in particular to a device and method for online detection of solar panel structure damage by using microwaves.

Background technique

In 2008, my country's solar panel production was 2895MW, and in 2009 it reached 4382MW, accounting for 40% of global production. my country has become the world's largest producer of solar panels. In 2010, the domestic output of photovoltaic cells reached 7GW, of which more than 90% were exported. According to the market development trend of solar panel materials predicted by China Renewable Energy Society, the global demand in 2013 will be three times that of 2008. There are about 443 solar panel and module manufacturers in China, which have formed a whole industrial chain production enterprise from silicon preparation to solar module production, and their production capacity has leapt to the forefront of the world. At present, the demand for green energy is growing rapidly, and the output of solar panels in China continues to expand rapidly, which will definitely trigger the demand for damage detection equipment for battery panel structures.

Structural damage detection of solar panels is a key process in the production process of solar panels or components. Since silicon solar panels are usually sliced from polycrystalline or single crystal rods, damage may occur in every link of the production process , resulting in defects such as hidden cracks, fragments, chipping, virtual welding, and section grids. If the slice thickness is reduced, the amount of silicon material used can be reduced, the cost can be reduced, and energy consumption can be reduced. But what follows is an increase in the breakage rate and stricter control requirements for all aspects of production, otherwise it will be counterproductive. The silicon wafer thickness of most manufacturers is about 200 microns, and Yingli Group has achieved a thickness of about 180 microns. The general sequence of the battery preparation process is silicon film forming surface preparation, diffusion junction formation, back junction removal, upper and lower electrodes fabrication, peripheral corrosion, evaporation anti-reflection film, and finally silicon solar cells. Among them, the role of the electrode is to output electric energy, and the anti-reflection film is to increase the output power. Due to the many steps in the production process and the strict requirements on the preparation conditions, the quality defects of the battery are difficult to avoid. The performance is as follows: 1) There may be scratches and cracks in the formed film; 2) There is a gap between the adhesive surface of the silicon film and the anti-reflection film; 3) There may be air holes in the evaporated anti-reflection film. Most of these defects are invisible to the naked eye, so a sensitive and accurate device that can detect incipient defects is needed. The defects of the solar panel greatly affect the service life and efficiency of the battery, and it becomes very important to improve the quality of the solar panel. If the damage can be found after the completion of each production link, the operation status of the production equipment can be adjusted in time, thereby improving the pass rate and product grade of the product, which requires a large number of online structural damage detection equipment.

At present, there are two types of detection principles: infrared scanning detection and electroluminescence detection. The infrared scanning detection method uses a laser light source with a certain wavelength to scan the solar panel point by point, and the corresponding photosensitive element detects the defect. This method takes a long time to detect large-scale solar panels, the imaging is rough, and the scanning mechanism is complicated. The electroluminescence detection method is to use the forward current of the PN junction of the solar cell panel to recombine electrons and holes to release energy in the form of emitted photons. At the same time, due to the existence of junction resistance, heat is also generated and infrared radiation is emitted. If there is no electron migration in the defective part, there will be obvious dark spots on the solar panel, and the camera method is used to obtain the image of the damage of the solar panel. This method does not require a scanning mechanism, and the device structure is relatively simple, but it also has the disadvantages of high cost, limited color display, influence by ambient light, and complicated process. Moreover, most of the solar panel defect detection equipment produced by domestic manufacturers is offline and used for random inspection, and cannot be detected online, which makes it difficult to meet the increasingly stringent requirements of photovoltaic companies. On-line detection of solar panel damage has become the focus of current research.

Contents of the invention

In order to solve the problems existing in the above-mentioned prior art, the object of the present invention is to provide a device and method for online detection of solar panel structural damage using microwaves. The detection device and method of the present invention can realize real-time online monitoring of solar panel damage , to meet the requirements of non-destructive testing of battery panels on the production line.

The principle of the present invention is: the microwave transmission power used by the detection system is generally between several milliwatts and tens of milliwatts, and the heating effect of microwaves on different materials can be ignored, so it can be considered that the microwave transmission power and the reception power are basically the same, that is, No power loss. On the other hand, the relative permittivity of a solar panel (silicon material) is about 11.9, and the relative permittivity is 1 when the defect is air. When the relative permittivity is large, the reflectivity is small and the absorptivity is large; when the relative permittivity is small, the opposite is true. When microwaves propagate inside a dielectric material, the material will be polarized. However, the magnetic permeability of silicon and air are both 1, and the loss tangent is 0, so there is only a difference in relative permittivity. In the microwave frequency range, the dielectric constant of the crack is lower than that of the non-crack, and a small change in the measured object will cause a large change in its composite dielectric constant. Therefore, according to the relative dielectric constant of the measured substance Changes in electric constant to determine its damage.

To achieve the above object, the present invention adopts the following technical solutions:

A device for utilizing microwaves to detect solar panel structural damage on-line, comprising an active microwave resonator, a microwave signal processing system, and a damage LED indicator light 13; the active microwave resonator includes a vector network analyzer 1, a frequency The scanning source 2, the first isolator 3-1, the first adjuster 4-1 and the resonant cavity 6; the microwave signal processing system includes a coupling probe 7 placed in the resonant cavity 6, and a coupling probe 7 The attenuator 11, the second modulator 4-2, the second isolator 3-2 and the signal microprocessor circuit 12 are connected in sequence.

The first adjuster 4 - 1 is connected to the resonant cavity 6 through a coaxial cable 5 .

The detection method of the above-mentioned device that utilizes microwaves to detect solar panel structural damage on-line firstly fixes the resonant cavity 6 of the device above the solar panel to be tested, and then controls the frequency scanning source 2, the first The isolator 3-1, the first adjuster 4-1 and the resonant cavity 6 emit microwave signals 8 with a frequency of 3-20 GHz and enter the surface of the solar panel 9 to be tested through the opening of the resonant cavity, part of which is absorbed and reflected, and part of which is transmitted The tested solar cell panel 9 reaches the surface of the metal background 10 and undergoes total reflection, and then the echo signal is picked up by the coupling probe 7, and the echo signal passes through the attenuator 11, the second adjuster 4-2 and the second isolator 3 -2 processing, and the resonant cavity frequency under the pre-calibrated non-defect condition is compared by the signal microprocessor circuit 12 to obtain the real-time resonant cavity frequency offset Δf, and the measured resonant cavity frequency offset Δf can be known by the instant resonant cavity frequency offset Δf The structural damage degree of the solar battery panel, and display the corresponding damage situation LED indicator light 13.

The invention applies the active microwave resonant cavity to the damage detection of the solar battery panel. The resonant cavity is not only a sensor but also a component of the oscillator. The device can be fixed on the production line to allow the battery panel to be detected to pass through. When a defective battery plate passes under the resonant cavity, it is only necessary to measure the instantaneous frequency offset Δf of the resonant cavity to detect whether the corresponding battery plate is defective. Utilizing the microprocessor circuit, higher detection accuracy can be obtained. The microwave transmission power of the system is about 10mW, and the scattered microwave radiation during operation has no pollution to the environment and human body, has high safety and is not affected by ambient light, and has low cost. Moreover, the microwave defect measurement technology has the advantages of fast, continuous, no contact with the measured object, high resolution, safety and convenience.

Description of drawings

The accompanying drawing is a schematic diagram of the detection device of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in the accompanying drawings, a device of the present invention that utilizes microwaves to detect solar panel structural damage on-line includes an active microwave resonant cavity, a microwave signal processing system, and a damage LED indicator 13; the active microwave resonant cavity includes sequentially connected The vector network analyzer 1, the frequency scanning source 2, the first isolator 3-1, the first adjuster 4-1 and the resonant cavity 6; the microwave signal processing system includes a coupling probe placed in the resonant cavity 6 The pin 7, the attenuator 11, the second adjuster 4-2, the second isolator 3-2 and the signal microprocessor circuit 12 are sequentially connected with the coupling probe 7. The first adjuster 4 - 1 is connected to the resonant cavity 6 through a coaxial cable 5 . The solar cell panel 9 is the detection object, and the metal background 10 is set to allow total reflection of the microwave, otherwise the echo signal cannot be picked up.

As shown in the accompanying drawings, the present invention uses microwaves to detect the device detection method of solar panel structure damage on-line. First, the resonant cavity 6 of the device is fixed above the solar panel to be tested, and then the frequency scanning source 2 is controlled by a vector network analyzer 1. , the first isolator 3-1, the first adjuster 4-1 and the resonant cavity 6 transmit microwave signals 8 with a frequency of 3 to 20 GHz and enter the surface of the solar panel 9 to be tested through the opening of the resonant cavity, part of which is absorbed and reflected , a part penetrates the measured solar cell panel 9 to the surface of the metal background 10 and undergoes total reflection, and then picks up the echo signal through the coupling probe 7, and the echo signal passes through the attenuator 11, the second adjuster 4-2 and the second The isolator 3-2 processes, and compares the resonant cavity frequency under the no-defect condition calibrated in advance by the signal microprocessor circuit 12 to obtain the real-time resonant cavity frequency offset Δf, through which the real-time resonant cavity frequency offset Δf can be obtained The structural damage degree of the tested solar cell panel is known, and the corresponding damage situation LED indicator light 13 is displayed.

Example

Select six intact solar silicon wafers with a size of 125*125mm, and make the following defects through a wire cutting machine: (1) intact silicon wafers; (2) small holes with a diameter of 1mm; (3) holes with a diameter of 1.5mm; (4) A hole with a diameter of 2mm; (5) A scratch with a length of 5mm; (6) A crack with a length of 5mm.

Using the above-mentioned device to measure the resonant frequency offset evaluation results of six samples with different damage conditions are shown in Table 1:

Table 1

In Table 1, indicator light 1 is green light; indicator light 2 is red light, indicating that the solar silicon wafer is damaged.

It can be seen from the experimental results that the threshold of the device to measure defects is 1mm. Defects smaller than or equal to 1 mm are not easy to cause a shift in resonance frequency and cannot be measured; while defects larger than 1 mm have obvious shifts in resonance frequency and are easy to measure.

Claims (3)

1. A device that utilizes microwaves to detect solar panel structural damage on-line, characterized in that: it includes an active microwave resonant cavity, a microwave signal processing system, and a damage situation LED indicator light (13); the active microwave resonant cavity includes sequentially connected A vector network analyzer (1), a frequency sweep source (2), a first isolator (3-1), a first adjuster (4-1) and a resonant cavity (6); the microwave signal processing system includes The coupling probe (7) placed in the resonant cavity (6), the attenuator (11), the second adjuster (4-2), the second isolator (3- 2) and the signal microprocessor circuit (12). 2. A device for online detection of solar panel structural damage using microwaves according to claim 1, characterized in that: the first adjuster (4-1) and the resonant cavity (6) are connected through a coaxial cable (5 )connect. 3. The detection method of the device for online detection of solar panel structure damage by using microwaves according to claim 1 or 2, characterized in that: firstly, the resonant cavity (6) of the device is fixed above the solar panel to be tested, and then the vector The network analyzer (1) controls the frequency scanning source (2), the first isolator (3-1), the first adjuster (4-1) and the resonant cavity (6) to transmit microwave signals with a frequency of 3 to 20 GHz ( 8) Enter the surface of the measured solar panel (9) through the opening of the resonant cavity, a part is absorbed and reflected, and a part penetrates the measured solar panel (9) to the surface of the metal background (10) and undergoes total reflection, and then passes through the coupling The probe (7) picks up the echo signal, which is processed by the attenuator (11), the second adapter (4-2) and the second isolator (3-2), and is processed by the signal microprocessor circuit ( 12) Comparing with the pre-calibrated resonant cavity frequency in the case of no defect, the real-time resonant cavity frequency offset Δf can be obtained, and the structural damage degree of the tested solar panel can be known through the instant resonant cavity frequency offset Δf, and displayed Corresponding damage status LED indicator light (13).

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