Factors affecting the power generation of photovoltaic power plants

For investors in photovoltaic power stations, each additional kilowatt-hour of electricity generated by the power station will result in additional kilowatt-hours of income. Because the power generation of the power station is directly related to the investment return cycle, investors are most concerned about the power generation of the power station. The power generation of a photovoltaic power station will be affected by many factors, such as: the quality of photovoltaic modules, inverters, cables, module installation orientation, inclination, dust and shadow shielding, photovoltaic module and inverter matching system scheme, power grid quality, etc.

The impact of shadow occlusion on power generation

Among the many factors that affect the power generation of photovoltaic power generation systems, shadow occlusion is a relatively common one. Common occlusions mainly include telephone poles, trees, guardrails, bird droppings, dust, and front and rear occlusion of components.

During the construction of many power stations, it is often impossible to completely avoid shadows. Many people think that a small shadow area will not have a big impact. In fact, this is not the case. If a part of a component or a component is blocked, the entire string of components will be affected. This is the barrel effect of a series circuit. In a string of components, the current of each component is the same, and the maximum current is determined by the smallest component. of. Therefore, as long as one component is blocked, the output power of the entire string will be affected. In severe cases, it will cause the components to produce hot spot effects, reduce the power generation efficiency and service life of the components, and even cause the components to be partially burned, posing certain safety risks. Therefore, it is not only necessary to avoid shadows during power plant design, but also to pay attention to post-operation and maintenance and to regularly clean components.

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                                                                           Occlusion of components by different shadows

The impact of system capacity ratio on power generation

The capacity ratio refers to the ratio of the installed capacity of the photovoltaic system to the rated capacity of the inverter. If the photovoltaic system is designed with a capacity ratio of 1:1 and the output power of the photovoltaic modules does not reach the nominal power, the capacity of the inverter will be wasted. At present, over-configuration design is often used to improve the comprehensive utilization rate of photovoltaic systems, reduce system electricity costs, and increase power station revenue. But this does not mean that the capacity ratio can be expanded infinitely to save inverter investment, because the cost of the inverter accounts for only about 5% of the entire photovoltaic system. Too much over-configuration is not only uneconomical, but also leads to inverter The inverter operates at the limit, resulting in loss of power generation. Therefore, rationally designing the system capacity ratio is conducive to improving the economy of the photovoltaic power generation system. In areas with different types of resources, due to different solar resource conditions and different regional temperature and other characteristics, calculations need to be made based on the specific local conditions. The following are recommended volume ratios for different areas.

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The impact of improper cable selection on power generation

If the inverter is compared to the brain of a photovoltaic power station, the cable is the nervous system of the photovoltaic system, connecting photovoltaic modules, inverters, combiner boxes, grid cabinets and other equipment into a whole. Therefore, reasonable cable selection is crucial to the entire photovoltaic system.
When designing and selecting cables, you must choose the appropriate wire diameter. Especially for large-scale photovoltaic power stations, which occupy a large area and have long lines. If the AC cable wire diameter is too thin, it will cause overloading and heating of the cable, which will not only affect the power generation, but also There may be safety hazards such as short circuit and fire. Another thing to note is that for cables with the same carrying capacity, the cross-sectional area of aluminum cables is much larger than that of copper cables, so it is necessary to consider whether the AC end of the inverter can be connected.

The AC output side of the inverter is designed based on copper wires, and it is recommended to use copper core cables. However, using aluminum core cables will save certain investment costs compared to copper core cables, so many installers will use aluminum core cables. However, you must use copper-aluminum transition terminals that meet standard requirements, because copper-aluminum joints are prone to electrochemical corrosion, causing poor contact between copper and aluminum, increasing resistance, and affecting the efficiency of the entire photovoltaic system. Long-term operation will cause the temperature of the joint to rise, accelerate corrosion, and even burn out.

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Corrosion of copper and aluminum joints

Cable selection has a direct impact on the power generation of photovoltaic power stations. Choosing appropriate cable types and specifications, as well as cables with good load capacity, weather resistance and durability, can minimize power loss, improve power generation efficiency, and ensure the normal operation of photovoltaic power stations and maximize power generation.

The impact of grid power quality on power generation

The power quality of the power grid includes: voltage deviation, current deviation, frequency deviation, voltage fluctuation or flicker, three-phase imbalance, temporary or transient overvoltage, waveform distortion, voltage sag, etc.

1. Grid voltage is out of range

The voltage and frequency of the grid are not constant and will change with changes in load and power flow, and the output voltage of the inverter follows the grid voltage. However, when the grid voltage and frequency fluctuate beyond a certain range, the inverter will stop working.

2. Voltage fluctuations, flicker and harmonics

In some mechanical processing factories, there are high-power equipment such as cranes, electric welding machines, and gantry milling machines, as well as in some electric arc furnace factories. Between the startup and shutdown of the equipment, the electric energy changes very drastically. At the same time, it is accompanied by a large number of harmonics, which exist in the power grid. Harmonics and unbalanced negative sequence components will cause the photovoltaic system output active power to fluctuate, and the higher the grid voltage distortion rate, the smaller the photovoltaic system output active power; it will also output current distortion, and the higher the grid voltage distortion rate, the photovoltaic system output The greater the current THD. When the grid voltage fluctuates violently, the inverter’s adjustment capability is limited, which may cause the photovoltaic inverter to restart frequently. In serious cases, the power components in the inverter may explode due to overvoltage and the electrolytic capacitor may explode due to overcurrent.

From the above points, the power generation of photovoltaic power stations not only depends on the power generation performance of the photovoltaic power station itself, but is also closely related to subsequent operation and maintenance. Correct operation and maintenance can not only increase power generation, but also extend the service life of equipment and power stations.

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