Component power is related to what equipment, and how should it be designed? In a photovoltaic grid-connected system, the power of components is related to the inverter, and the power matching between components and inverters is not a fixed ratio of 1:1. It needs to be combined with the project Comprehensive consideration of the specific situation, the main influencing factors are irradiance, system loss, inverter efficiency, inverter life, inverter voltage range, component installation angle, etc.
1. Component installation tilt angle and azimuth angle
When the plane of the object is completely perpendicular to the light, the received power is the largest. If the object is placed obliquely, the plane of the object and the light form a certain angle, and the received power will be discounted. For the same area, the received power will be much less. The angle between the module and the sun is perpendicular, and the power is maximum.
2. The irradiance of the installation area
The output power of the module is related to the irradiance. In areas with good solar energy resources, due to the lack of clouds on sunny days, good air quality, and high atmospheric transparency, the solar radiation reaching the surface of the module is much higher than the average value of areas with poor resources.
3. Installation altitude
The higher the altitude, the thinner the air, and the smaller the weakening effect of the atmosphere on solar radiation, and the stronger the solar radiation reaching the ground. For example, the Qinghai-Tibet Plateau is the region with the strongest solar radiation in China. Where the air is thinner, the heat dissipation of the inverter will be worse. If the altitude exceeds a certain height, the inverter will have to derate.
4. DC side system efficiency
In a photovoltaic system, energy is transmitted from solar radiation to photovoltaic modules, through DC cables, combiner boxes, and DC power distribution to the inverter, and all links have losses. Different design schemes, such as the use of centralized, string, and distributed schemes, have very different DC side losses.
5. Inverter heat dissipation conditions
Generally, the inverter should be installed in a well-ventilated place and avoid direct sunlight, which is conducive to heat dissipation. If the inverter has to be installed in a closed place that is not conducive to heat dissipation due to site restrictions, the derating of the inverter must be considered, and fewer components should be equipped.
6. Component factors
Positive power tolerance: In order to ensure that the attenuation of photovoltaic modules does not exceed 20% in 25 years, many module factories have a positive tolerance of 0-5% for the modules that have just been shipped. For example, the actual power of a 265W module may be 270W.
Negative temperature coefficient: The power temperature system of the module is about -0.41%/℃, the power of the module will increase when the temperature of the module drops. A 250W module may have a maximum output power of more than 250W in areas with the best sunshine in my country, such as northern Ningxia, northern Gansu, and southern Xinjiang, without considering equipment loss.
Double-sided module: The double-sided module can not only receive the radiation power of sunlight on the front side, but also receive the reflected radiation power of sunlight on the back side. Different objects have different reflectivity to sunlight in different spectral bands. Snow, wetland, wheat, desert, different ground features have different reflectance in the same band, and the same ground features have different reflectance in different bands
7. Inverter factors
Inverter efficiency: The efficiency of the inverter is not a constant value. There are power switching device losses and magnetic losses. At low power, the efficiency is relatively low. When the power is 40% to 60%, the efficiency is the highest. When it exceeds 60%, Efficiency gradually decreases. Therefore, the total power of the photovoltaic power should be controlled between 40% and 60% of the inverter power to obtain the best efficiency.
Inverter life: Photovoltaic inverters are electronic products, and their reliability has a lot to do with the operating temperature of the inverter. Among them, if the temperature of components such as capacitors, fans, and relays increases by 10°C, the failure rate may increase by more than 50%. . The operating temperature is also related to the power. According to statistics, the long-term operation of the inverter at 80-100% power is about 20% lower than that at 40-60% power.
The best working voltage range of the inverter: the working voltage is around the rated working voltage of the inverter, the efficiency is the highest, the single-phase 220V inverter, the rated input voltage of the inverter is 360V, the three-phase 380V inverter, the inverter The rated input voltage of the converter is 650V.