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What Are The Factors That Affect The Normal Operation Of Solar Photovoltaic Modules

What Are The Factors That Affect The Normal Operation Of Solar Photovoltaic Modules

Solar photovoltaic modules are the most important equipment in photovoltaic solar power generation. Special circumstances in the daily installation and operation and maintenance process will cause the hot spot effect and potential induced attenuation effect (PID) of photovoltaic modules, causing losses to customers. We should pay attention to controlling photovoltaic power plants to avoid these two effects when installing and maintaining power plants.

Hot spot effect

A shaded solar cell module in a series branch will be used as a load to consume the energy generated by other solar cell modules with light. The shaded solar cell module will generate heat at this time, which is the hot spot effect. This effect can severely damage solar cells. Part of the energy produced by the solar cell with light may be consumed by the shaded cell. The hot spot effect may only be a piece of bird droppings. In order to prevent the solar cell from being damaged due to the hot spot effect, it is best to connect a bypass diode in parallel between the positive and negative poles of the solar cell module

Tube to avoid the energy generated by the lighting components being consumed by the shaded components. When the hot spot effect is severe, the bypass diode may be broken down, causing the component to burn out, as shown in the figure below:

PID effect
The potential-induced attenuation effect is the long-term high-voltage effect of the battery module, which causes leakage current between the glass and the packaging material, and a large amount of charge strikes the surface of the battery chip, which deteriorates the passivation effect of the battery surface and causes the performance of the module to be lower than the design standard. When the PID phenomenon is severe, the power of a module will be attenuated by more than 50%, thereby affecting the power output of the entire string. The PID phenomenon is most likely to occur in coastal areas with high temperature, high humidity and high salinity.

After the PID effect is produced, some batteries have high resistance and the main reasons for the component PID phenomenon are as follows:
System design reason: The lightning protection grounding of the photovoltaic power station is realized by grounding the module frame at the edge of the square array, which causes a bias voltage between a single module and the frame. The higher the bias voltage of the module, the more serious the PID phenomenon will be. . For P-type crystalline silicon components, grounding the negative pole of the inverter with a transformer to eliminate the positive bias of the component frame relative to the cell will effectively prevent the occurrence of PID phenomenon, but the negative grounding of the inverter will increase the corresponding system construction cost;

Photovoltaic module reasons: high temperature and high humidity in the external environment cause leakage current between the solar cell and the ground frame, and a leakage current channel is formed between the packaging material, backplane, glass and frame. Changing the insulating film of EVA is one of the ways to realize the anti-PID of the module. Under the condition of using different EVA encapsulating film, the anti-PID performance of the module will be different. In addition, the glass in photovoltaic modules is mainly soda lime glass, and the effect of glass on the PID phenomenon of photovoltaic modules is still unclear;

Cell reason: The uniformity of cell sheet resistance, the thickness of the anti-reflection layer and the refractive index have different effects on PID performance. Among the above three aspects that cause the PID phenomenon, the module PID phenomenon caused by the potential difference between the module frame and the module in the photovoltaic system is recognized by the industry, but the mechanism for the module to generate the PID phenomenon in the module and the cell is not yet It is clear that the corresponding measures to further improve the anti-PID performance of components are still unclear.

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