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Two Effects That Affect the Normal Operation of Solar Photovoltaic Modules

Two Effects That Affect the Normal Operation of Solar Photovoltaic Modules

November 11,2020.
Solar photovoltaic modules are the most important equipment in photovoltaic power generation. Special circumstances in the process of daily installation, operation and maintenance will cause the hot spot effect and potential induction attenuation effect (PID) of photovoltaic modules, causing losses to most owners. Therefore, attention should be paid to the control of photovoltaic power plants to avoid installation and maintenance of power plants When, these two effects.

1. Hot spot effect
The shaded solar cell module in the series branch will be used as a load to consume energy generated by other solar cell modules. The shaded solar cell module will generate heat at this time, which is a hot spot effect.
This effect can seriously damage solar cells. The shadow cell consumes part of the energy generated by the solar cell through light. The hot spot effect may be just a piece of bird droppings.
In order to prevent damage to the solar cell due to the hot spot effect, it is best to connect a bypass diode in parallel between the anode and cathode of the solar cell module to prevent the energy generated by the optical module from being consumed. Shadow module. When the hot spot is severely affected, the bypass diode may be damaged, causing the component to burn out.

2. PID effect
The potential-induced attenuation effect is the long-term high-voltage effect of the battery module, which will cause leakage current between the glass and the packaging material, and generate a large amount of charge corrosion on the surface of the battery chip, thereby making the passivation worse. It will affect the surface of the battery and cause the performance of the battery module to drop below the design standard. When the PID phenomenon is serious, the power of the module will be attenuated by more than 50%, thereby affecting the power output of the entire light string. The PID phenomenon is most likely to occur in coastal areas with high temperature, high humidity and high salinity.
After the PID effect occurs, some batteries will have higher resistance, and the main reasons for the analysis of the solar photovoltaic module manufacturers that cause the module PID phenomenon are as follows:

The first reason is the reason of the system design: the lightning protection grounding of the photovoltaic power station is realized by grounding the module frame at the edge of the square array, which will generate a bias voltage between a single module and the frame. The higher the bias voltage of the module, the PID phenomenon will appear. The more serious. For P-type crystalline silicon components, using a transformer to ground the negative pole of the inverter to eliminate the positive bias of the component frame relative to the battery will effectively prevent the PID phenomenon, but the negative grounding of the inverter will increase the corresponding system construction costs;

The second reason is the photovoltaic module: the high temperature and high humidity in the external environment will cause leakage current between the solar cell and the grounded frame, and the leakage current path will be formed between the packaging material, the back sheet, the glass and the frame. Changing the insulating film EVA is one of the methods to realize the anti-PID of the module. In the case of using different EVA packaging films, the anti-PID performance of the module will be different. In addition, the glass in photovoltaic modules is mainly lime-soda glass, and the effect of glass on the PID phenomenon of photovoltaic modules is still unclear.

The third is the reason for the battery: the uniformity of the battery sheet resistance, the thickness of the anti-reflection layer and the refractive index have different effects on the 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 has been recognized by the industry, but the mechanism of the module generating the PID phenomenon in the PID phenomenon has been recognized by the industry. Recognized. It is obvious that the modules and units have not yet been determined, and the corresponding measures to further improve the anti-PID performance of the components are still unclear.

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