Polarization type PID test method for photovoltaic module

Abstract

The invention relates to a photovoltaic module polarization type PID test method. The method comprises the following steps: S1, carrying out a stability test; appearance inspection and various tests are carried out on the photovoltaic module before the test is started; s2, pasting an insulating adhesive tape, then pasting a conductive adhesive tape on the upper surface and the lower surface of the photovoltaic module at positions which do not shield a battery piece, reserving a leading-out end, coating conductive gel on the upper surface of the photovoltaic module, covering the conductive gel with a transparent film, and finally pasting an aluminum foil on the back surface of the photovoltaic module; s3, placing the photovoltaic module in the steady-state solar simulator, and supporting a photovoltaic module back plate on the back surface by using a rubber pad; an electronic load is connected between positive and negative terminals of the photovoltaic module, and the normal working condition of the module is simulated; s4, the test time is 20 hours; and S5, after the test is finished, performing appearance inspection and various tests. According to the polarization type PID test method for the photovoltaic module, the total test time is shortened, and the resistance of the photovoltaic module to PID-p is represented.

Description

Technical Field

[0001] The present invention relates to the technical field of testing methods, and in particular to a polarization-type PID testing method for photovoltaic modules. Background Art

[0002] During the actual operation of photovoltaic modules in power plants, there is a potential difference between the inside of the module and the ground, which is more obvious in the photovoltaic modules in the area between the two ends of the inverter. The strong potential difference will cause the power generation performance of the photovoltaic modules to decay. When the ground is at a positive bias compared to the inside of the module, metal cations in the glass migrate towards the surface of the cell under the action of the potential, and shunt-type potential-induced degradation (PID-s) is likely to occur; when the ground is at a negative bias compared to the inside of the module, the battery charges inside the module accumulate on the surface of the passivation layer, and polarization-type potential-induced degradation (PID-p) is likely to occur. And the PID-p degradation is extremely unstable, and light (mainly ultraviolet light) can reactivate the orderly distribution and flow of internal charges and improve the damaged passivation layer structure.

[0003] Conventional PID testing scheme: Place the photovoltaic module in a high-temperature and high-humidity environmental chamber, connect a bias power supply between the module frame and the inside of the module, and conduct a PID test for at least 96 hours. In this testing method, the photovoltaic module is in a lightless environment, and polarization-type PID degradation is likely to occur, which cannot represent the actual PID resistance ability of the photovoltaic module in the power plant site.

[0004] CN202311750575.0 discloses a testing method for photovoltaic modules. By combining ultraviolet irradiation and PID testing, the working environment of light, heat, and humidity of the photovoltaic module is simulated, making the test results of the photovoltaic module more accurate. Moreover, the method of first performing ultraviolet testing on the photovoltaic module and then performing PID testing, compared with the method of simultaneously performing ultraviolet testing and PID testing, has higher performance for the photovoltaic modules passing the test and can better meet the requirements. Such a testing method has the following defects: on the one hand, the testing process of this scheme is cumbersome and time-consuming, and it cannot well simulate the actual working conditions of the photovoltaic module outdoors; on the other hand, the testing process of this scheme is still in a dark environment, without considering the on-site characteristics and recovery mechanism of the PID effect, and the test results cannot effectively conform to the actual working conditions of the photovoltaic module outdoors.

[0005] The PID test method for opened photovoltaic modules disclosed in CN202410115994.5 includes sample processing before PID, PID test, sample processing after PID, and result processing. Among them, the PID test includes: stabilizing the test module in a double 85 environment for 12 - 24 hours; applying voltage and maintaining it for 48 hours; the environmental test chamber stops for 18 - 24 hours to allow the temperature and relative humidity to drop naturally, and the applied voltage remains unchanged during the shutdown process; restart the environmental test chamber, run it to the double 85 environmental conditions, and maintain the applied voltage unchanged for 48 hours for testing; the result processing includes: using the comparison module as a reference, obtaining the defect change and power attenuation of the test module after experiencing PID, and then giving an evaluation conclusion. The method of the present invention effectively simulates the long-term potential impact of the natural PID performance of photovoltaic modules in a high-temperature and high-humidity environment by using the natural cooling after the environmental test chamber stops, and can effectively evaluate the long-term potential impact of the natural environment on the PID performance of photovoltaic modules. The above test method has the following defects: the test scheme is still in a dark environment and does not solve the situation where the PID test conditions do not match the actual environment, and cannot effectively investigate the actual resistance ability of photovoltaic modules to the PID effect.

[0006] According to the PID test cases of photovoltaic testing laboratories, many photovoltaic modules show extremely unstable states after the PID test, and the power attenuation exceeds 5% required by IEC 61215. However, after the final stability test (cumulative ultraviolet light of 2 kwh / m2), their power will return to the attenuation range required by the standard. This is mainly due to the excessive difference in aging stress between the PID test and the normal working environment of photovoltaic modules, and the modules are in a metastable state after the PID test. According to the requirements for the PID test in IEC 61215-2:2021, when the power attenuation of the module exceeds 5% after the test, a final stability test is required to eliminate the influence of PID-p on the test results, resulting in a relatively long overall test process, high test costs, and large consumption of labor costs. Summary of the Invention

[0007] The technical problem to be solved by the present invention is: to solve the problems existing in the above background technology, a polarization-type PID test method for photovoltaic modules is provided, which avoids the influence of the dark environment of the previous PID test on the test results, restores the actual working conditions of photovoltaic modules in the power station according to the PID attenuation mechanism of photovoltaic modules, reduces the overall test time, and characterizes the resistance ability of photovoltaic modules to PID-p within 20 hours of effective time.

[0008] The technical solution adopted by the present invention to solve its technical problems is: a polarization type PID test method for photovoltaic modules, comprising the following steps: S1. Select 4 photovoltaic modules and conduct a stability test under natural sunlight or a steady-state solar simulator; then conduct an appearance inspection, electrical performance test, wet leakage current test, and electroluminescence test on the photovoltaic modules before the start of the test; S2. Stick insulating tapes with a width of 10 mm along the gaps between the upper and lower surfaces of the photovoltaic modules and the frame, then stick conductive tapes at positions on the upper and lower surfaces of the photovoltaic modules that do not block the cells and reserve lead-out ends, apply conductive gel on the upper surface of the photovoltaic modules, then cover the conductive gel with a transparent film, and finally stick aluminum foil on the back of the photovoltaic modules; S3. Place the photovoltaic modules in a steady-state solar simulator, and use rubber pads to support the backplane of the photovoltaic modules; connect an electronic load between the positive and negative terminals of the photovoltaic modules to simulate the normal working condition of the modules; connect the lead-out end of the conductive tape on the back of the photovoltaic modules to the negative terminal of the module, and connect the lead-out end of the conductive tape on the front of the photovoltaic modules and the negative terminal of the photovoltaic modules to the grounding terminal of the bias power supply; S4. Place the photovoltaic modules in a steady-state solar simulator with an ultraviolet irradiation ratio of 5% in the wavelength range of 290 nm - 400 nm, set the irradiance to 100 W / m 2 , set the temperature of the photovoltaic modules to 60 °C, turn on the heating air box, and turn on the bias voltage after the temperature of the photovoltaic modules reaches the set value. Set two photovoltaic modules to positive bias voltage and two photovoltaic modules to negative bias voltage, and the test time is 20 hours; S5. After the test is completed, let the temperature of the photovoltaic modules naturally drop to room temperature, and then turn off the light source and the bias voltage; remove the transparent film, conductive gel, insulating tape, and conductive tape of the photovoltaic modules under a light source with a wavelength greater than 600 nm, and conduct an appearance inspection, wet leakage current test, electrical performance test, and electroluminescence test.

[0009] Further defined, in the above technical solution, the stability test operation in S1 is to conduct an electrical performance test on 4 photovoltaic modules after every 5 kWh / m2 of irradiance, and obtain the maximum value Pmax, minimum value Pmin, and average value Paverage of the power of three consecutive tests. Use (Pmax - Pmin) / Paverage < 1% for determination, and if the condition is met, the stability meets the requirements.

[0010] Further defined, in the above technical solution, the appearance inspection in S1 is carried out according to MQT01 of IEC 61215-2:2021; the wet leakage current test is carried out according to MQT 15 of IEC 61215.

[0011] Further defined, in the above technical solution, in S4, a positive bias voltage is set for the two photovoltaic modules, the surface of the photovoltaic module is grounded, and the internal circuit of the photovoltaic module is the system voltage compared to the ground; a negative bias voltage is set for the two photovoltaic modules, the surface of the photovoltaic module is grounded, and the internal circuit of the photovoltaic module is a negative system voltage compared to the ground.

[0012] The beneficial effects of the present invention are as follows: A photovoltaic module polarization type PID test method proposed by the present invention avoids the influence of the dark environment of the previous PID test on the test results. According to the PID attenuation mechanism of the photovoltaic module, it restores the actual working conditions in the photovoltaic module power station, reduces the overall test time, and characterizes the resistance ability of the photovoltaic module to PID-p within 20 hours of effective time. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0014] Figure 1 is the structural schematic diagram of the present invention;

[0015] Figure 2 is the flow schematic diagram of the test method of the present invention;

[0016] Figure 3 is the initial electroluminescence image of Sample 1;

[0017] Figure 4 is the final electroluminescence image of Sample 1;

[0018] Figure 5 is the initial electroluminescence image of Sample 2;

[0019] Figure 6 is the final electroluminescence image of Sample 2;

[0020] Figure 7 is the initial electroluminescence image of Sample 3;

[0021] Figure 8 is the final electroluminescence image of Sample 3;

[0022] Figure 9 is the initial electroluminescence image of Sample 4;

[0023] Figure 10 is the final electroluminescence image of Sample 4;

[0024] Figure 11is the initial electroluminescence image of sample 5;

[0025] Figure 12 is the final electroluminescence image of sample 5.

[0026] The reference numerals in the drawings are: 1, frame; 2, insulating tape; 3, conductive tape; 4, conductive gel; 5, transparent film; 6, aluminum foil; A, photovoltaic module; 7, load; 8, bias power supply; 9, junction box. Detailed implementation manners

[0027] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] See Figures 1-12 Shown is a polarization-type PID test method for a photovoltaic module, including the following steps: S1. Select 4 photovoltaic modules A and conduct a stability test under natural sunlight or a steady-state solar simulator; then conduct an appearance inspection, electrical performance test, wet leakage current test and electroluminescence test on the photovoltaic module A before the start of the test; S2. Along the gaps between the upper and lower surfaces of the photovoltaic module and the frame 1, stick insulating tapes 2 with a width of 10 mm, then stick conductive tapes 3 on the upper and lower surfaces of the photovoltaic module A at positions that do not block the solar cells and reserve lead-out ends, coat conductive gel 4 on the upper surface of the photovoltaic module A, then cover the transparent film 5 on the conductive gel 4, and finally stick aluminum foil 6 on the back of the photovoltaic module A; S3. Place the photovoltaic module A in a steady-state solar simulator, and rely on the backplane of the photovoltaic module with a rubber pad; connect an electronic load between the positive and negative terminals of the photovoltaic module A to simulate the normal working condition of the module; connect the lead-out end of the conductive tape 3 on the back of the photovoltaic module A to the negative terminal of the module, and connect the lead-out end of the conductive tape 4 on the front of the photovoltaic module A and the negative terminal of the photovoltaic module A to the ground terminal of the bias power supply; S4. Place the photovoltaic module A in a steady-state solar simulator with a 5% ultraviolet irradiation ratio of 290 nm - 400 nm, set the irradiance to 100 W / m 2 , set the temperature of the photovoltaic module A to 60 °C, turn on the heating air box, and turn on the bias voltage after the temperature of the photovoltaic module A reaches the set value. Two photovoltaic modules are set to positive bias voltage, and two photovoltaic modules are set to negative bias voltage, and the test time is 20 hours; S5. After the test is completed, let the temperature of the photovoltaic module naturally drop to room temperature, and then turn off the light source and the bias voltage; remove the transparent film 5, conductive gel 4, insulating tape 2 and conductive tape 3 of the photovoltaic module under a light source with a wavelength greater than 600 nm, and conduct an appearance inspection, wet leakage current test, electrical performance test and electroluminescence test.

[0029] Among them, the stability test operation in S1 is to perform electrical performance tests on 4 photovoltaic modules after every 5 kWh / m2 of irradiation, and obtain the maximum value Pmax, the minimum value Pmin, and the average value Paverage of the power for three consecutive tests. The judgment is made using (Pmax - Pmin) / Paverage < 1%. If the condition is met, the stability meets the requirements. The appearance inspection in S1 is carried out according to MQT01 of IEC61215-2:2021; the wet leakage current test is carried out according to MQT 15 of IEC 61215. In S4, positive bias voltages are set for two photovoltaic modules, the surface of photovoltaic module A is grounded, and the internal circuit of photovoltaic module A is at the system voltage compared to the ground; negative bias voltages are set for two photovoltaic modules, the surface of photovoltaic module A is grounded, and the internal circuit of photovoltaic module A is at a negative system voltage compared to the ground.

[0030] This application has the following advantages compared with the traditional test method: By using the conductive gel 4 and the aluminum foil 6, the surface potential distribution of the module is made uniform, simulating the system bias voltage under the working state of the module; the external light and electronic load enable the photovoltaic module to work under normal conditions, simulating the working condition of the module under outdoor sunlight; the key point of its protection is that by coating the transparent conductive gel 4, the photovoltaic module can receive light and a uniform system bias voltage on the surface at the same time, avoiding the influence of uneven surface voltage of the conventional PID test module and the module being in a dark room on the PID test results.

[0031] Examples: Sample 1 is a control module without testing, Samples 2 and 3 are subjected to the +1500V system voltage polarization type PID test, and Samples 4 and 5 are subjected to the -1500V system voltage polarization type PID test. The test data are as follows: Table 1 is the pre-test of the samples; Table 2 is the initial electrical performance data of the samples; Table 3 is the electrical performance data of the samples after stability; Table 4 is the final electrical performance data of the samples; Table 5 is the post-test of the samples.

[0032]

[0033] Table 1

[0034]

[0035] Table 2

[0036]

[0037] Table 3

[0038]

[0039] Table 4

[0040]

[0041] Table 5

[0042] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, shall be covered by the protection scope of the present invention.

Claims

1. A polarization type PID test method for a photovoltaic module, characterized in that, The steps are as follows: S1. Select 4 photovoltaic modules and conduct stability tests under natural sunlight or a steady-state solar simulator; before the tests, conduct visual inspections, electrical performance tests, wet leakage current tests, and electroluminescence tests on the photovoltaic modules; S2. Along the gaps between the upper and lower surfaces of the photovoltaic modules and the frames respectively, stick insulating tapes with a width of 10 mm, then stick conductive tapes at positions on the upper and lower surfaces of the photovoltaic modules that do not cover the cells and leave lead-out ends, apply conductive gel on the upper surface of the photovoltaic modules, then cover the conductive gel with a transparent film, and finally stick aluminum foil on the back of the photovoltaic modules; S3. Place the photovoltaic modules in a steady-state solar simulator, and use rubber pads to support the backplane of the photovoltaic modules at the back; connect an electronic load between the positive and negative terminals of the photovoltaic modules to simulate the normal operating conditions of the modules; connect the lead-out ends of the conductive tapes on the back of the photovoltaic modules to the negative terminals of the modules, and connect the lead-out ends of the conductive tapes on the front of the photovoltaic modules and the negative terminals of the photovoltaic modules to the ground terminal of the bias power supply; S4. Place the photovoltaic modules in a steady-state solar simulator with an ultraviolet irradiation ratio of 5% in the wavelength range of 290 nm - 400 nm, set the irradiance to 100 W / m 2 , set the temperature of the photovoltaic modules to 60 °C, turn on the heating blower, and turn on the bias voltage after the temperature of the photovoltaic modules reaches the set value. Set two photovoltaic modules to positive bias voltage and two photovoltaic modules to negative bias voltage, and the test time is 20 hours; S5. After the test, let the temperature of the photovoltaic modules naturally drop to room temperature, and then turn off the light source and the bias voltage; remove the transparent film, conductive gel, insulating tape, and conductive tape from the photovoltaic modules under a light source with a wavelength greater than 600 nm, and conduct visual inspections, wet leakage current tests, electrical performance tests, and electroluminescence tests.

2. The photovoltaic module polarization type PID test method according to claim 1, characterized in that: In the stability test operation in S1, after an irradiation dose of every 5 kWh / m2, the electrical performance of 4 photovoltaic modules is tested to obtain the maximum value Pmax, the minimum value Pmin, and the average value Paverage of the power in three consecutive tests. It is judged by (Pmax - Pmin) / Paverage < 1%. If the condition is met, the stability meets the requirements.

3. A polarization type PID test method for a photovoltaic module according to claim 1, characterized in that: In the appearance inspection in S1, it is carried out according to MQT01 of IEC 61215-2:2021; the wet leakage current test is carried out according to MQT 15 of IEC 61215.

4. A photovoltaic module polarization type PID test method according to claim 1, characterized in that: In S4, two positive bias voltages are set for the two photovoltaic modules, the surface of the photovoltaic module is grounded, and the internal circuit of the photovoltaic module is the system voltage compared with the ground; two negative bias voltages are set for the two photovoltaic modules, the surface of the photovoltaic module is grounded, and the internal circuit of the photovoltaic module is the negative system voltage compared with the ground.

Images