Before component testing, it is necessary to use reference cells or standard components to calibrate the light intensity of the solar simulator light source, that is, to adjust the irradiance of the simulator so that the short-circuit current of the standard battery reaches the required value. Adjust to the datum point required by the magnitude transfer scheme. The calibration of standard batteries must meet the requirements of IEC60904-4 traceability standard. Figure 1 shows the value transfer scheme of the reference battery specified by the IEC60904-4:2009 standard, which is the current version. Figure 2 shows the value transfer scheme of the reference battery specified by the IEC60904-4:2017 standard, which is expected to be released in June 2019.
At present, the outdoor method, differential spectral response method, and simulator method are generally used internationally (respectively through secondary standard absolute radiometer, standard detector, and absolute spectral spectrophotometer) to transmit the calibration value of the battery standard to the reference battery. During the use of the battery standard sheet, the greater the number of transfers, the greater the uncertainty of the calibration value.
There are two types of standard calibration methods for commonly used component testers. One is absolute measurement, that is, the reference battery method test. Generally, third-party testing institutions use this calibration method, and use the standard to perform daily spot checks on the test system. Verification; the other is relative measurement, that is, the reference board method test. Generally, manufacturing companies use this scheme to send the components that are basically the same as the product to a qualified third-party testing agency, and use the absolute measurement method to give the component’s value. Electrical performance parameters, and then the manufacturer uses this component as the first-level standard, and copies the second-level standard for mass production and testing in the workshop. The standard plate belongs to the level of work reference.
The calibration operation and operation of the solar simulator is mainly divided into three steps:
(1) Calibration: Turn on the power, turn on the computer control system, and calibrate the light intensity of the solar simulator. There are generally two ways to calibrate the light intensity, one is to calibrate the light intensity by ISC, and the other is to calibrate the light intensity by Pmax;
(2) Test: After the light intensity calibration, place the component to be tested in the corresponding position correctly, connect the positive and negative terminals of the component to the positive and negative terminals of the tester respectively, click the test start button to start the light source, The simulated sunlight irradiates the component under test, and at the same time, the tester controls the current change of the component by quickly adjusting the size of the component load, and obtains different current and voltage corresponding values;
(3) Calculate and give test results: The internal software of the system makes the entire I-V curve according to these data and other parameters (such as measured component temperature, etc.), and gives the electrical properties such as current, voltage, power and fill factor at the maximum power point parameter. The more points that the electronic load adjusts during the test, the more accurate the I-V curve of the test, but the higher the performance requirements of the equipment, and the longer the test time will be. Generally, a transient simulator test with a pulse width of more than 80ms is selected.
Pay attention to the following points during operation:
(1) Testers should avoid looking directly at the light source to avoid eye damage, and choose to wear protective glasses as needed;
(2) The test table is clean, free of ash layers, foreign objects, and obstructions, and the grounding wire is well connected;
(3) The lead fixture of the tester should be in reliable contact with the component terminals to minimize the contact resistance;
(4) Wipe the light area of the tester, light intensity reference cells and standard battery components to keep them clean, and at the same time, the quality management personnel check whether the temperature compensation value set by the tester matches the temperature compensation coefficient of the standard sheet;
(5) The temperature of the sample to be tested is stable enough, generally controlled at (25±2) °C;
(6) The test environment is relatively sealed, not affected by sunlight and other light, and there is no large airflow fluctuation in the test area.
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