Photovoltaic modules are the most important equipment in photovoltaic power generation. If special circumstances occur during daily z section steel installation and operation and maintenance, it will cause hot spot effect of photovoltaic modules and potential induced attenuation effect (PID), causing losses for the majority of owners. Care should be taken to control the PV plant to avoid these two effects when installing and routinely maintaining the plant.
hot spot effect
The solar cell module that is shielded in a series branch will be used as a load to consume the energy generated by other illuminated solar cell components. The shaded solar cell component will heat up at this time, which is the hot spot effect. This effect can seriously damage the solar cell. Part of the energy generated by a solar cell with light may be consumed by the obscured battery. The hot spot effect may be just a piece of bird droppings. In order to prevent the solar cell from being damaged by the hot spot effect, it is preferable to connect a bypass diode between the positive and negative terminals of the solar cell module to prevent the energy generated by the photovoltaic module from being consumed by the shielded component. When the hot spot effect is severe, the bypass diode may be broken down and the assembly burned out.
The potential-induced attenuation effect is that the battery assembly has a long-term under high voltage, causing leakage current between the glass and the packaging material, and a large amount of electric charge is struck on the surface of the battery sheet, so that the passivation effect on the surface of the battery is deteriorated, resulting in lower than the design standard of the component. When the PID phenomenon is serious, it will cause the PV module power to attenuate by more than 50%, thus affecting the power output of the entire string. High temperature, high humidity, high salinity and coastal areas are most prone to PID phenomenon.
The high resistance of the battery causes the PV component PID phenomenon:
First, the system design reason: the lightning protection grounding of the photovoltaic power station is realized by grounding the component frame at the edge of the square array, which causes a bias voltage to be formed between the single component and the frame. The higher the bias voltage of the component occurs, the PID phenomenon occurs. The more serious it is. For the P-type crystalline silicon component, the grounding of the negative pole of the inverter with the transformer eliminates the forward bias of the component frame relative to the cell, which effectively prevents the occurrence of the PID phenomenon, but the grounding of the negative pole of the inverter increases the corresponding system. Construction costs.
Second, the reason for the photovoltaic components: high temperature, high humidity environment, the leakage current is formed between the battery chip and the ground frame, and a leakage current channel is formed between the packaging material, the back plate, the glass and the frame. The use of a modified insulating film, ethylene vinyl acetate (EVA), is one of the ways to achieve component anti-PID, and the anti-PID performance of the components may vary under different EVA encapsulation films. In addition, the glass in the photovoltaic module is mainly calcium soda glass, and the influence of glass on the PID phenomenon of the photovoltaic module is still unclear.
The third reason is the battery piece: the uniformity of the cell sheet resistance, the thickness of the anti-reflection layer and the refractive index have different effects on the PID performance. In the above three aspects of causing the PID phenomenon, the component PID phenomenon caused by the component frame in the photovoltaic system and the potential difference inside the component is recognized by the industry, but in the component and the battery chip, the component generates the PID phenomenon. The mechanism is still unclear, and the corresponding measures to further improve the anti-PID performance of photovoltaic modules are still unclear.