Photovoltaic module hot spot durability test

With the gradual expansion of the application field of photovoltaic power generation, various types and specifications of photovoltaic modules continue to enter the market. These components may behave very differently in actual use.

In particular, the hot spot effect may seriously affect the output performance of photovoltaic modules. The so-called hot spot effect network means that when one or several cells in the module are shaded or damaged, if the operating current exceeds the battery or battery pack, the short-circuit cable will be reduced. Then this part of the battery is placed in a reverse bias state, and the function in the circuit is affected by the power supply as the load consumes energy from the surface to form a local overheating phenomenon inside the component. The hot spot effect is an important factor that reduces the service life of the component and causes accidents in the photovoltaic system. The reason is that after the initial test is completed, the tested sample is continuously illuminated for 5 hours under the condition that can produce the worst hot spot effect, and finally the initial test is repeated, and the appearance, maximum output power and insulation resistance of the tested sample are compared before and after the hot spot Judging whether the sample has passed the hot spot durability test.

The key to the hot spot durability test is how to select the cells to be shaded, and to determine the corresponding shaded area when the delivered cells generate the maximum power consumption. Only in this way can the test be carried out under the strictest conditions. In order to ensure the reliability of the test results, two methods for selecting cells are provided in the relevant standards: (1) surface temperature method, under the illumination of a blanket light source of not less than 700 Wim, use an appropriate temperature detector to measure the hottest temperature 2) Covering and charging short-circuit current method, under the irradiance of not less than 700 W/m’, each battery is completely blocked in turn. Select one or one of them, and when it is blocked, the complex circuit of the photovoltaic module The magnitude of the current reduction is the largest, that is, to select the corresponding battery sheet when the short-circuit current value of the component after being shaded is the smallest due to the electric light of the sheet. The above two methods are used by people in the industry, but there is no report about the consistency of the results selected by the two methods. In this paper, two methods are used for selection. and analyze the results.