In the photovoltaic power station system, the components and the photovoltaic inverter are two important components of the whole system. The price of the inverter is much higher than that of a single component. Many users have this idea, relying on the maximum input of the photovoltaic inverter. power, and increase the access of components to improve the overall power generation of the power station. But only the scientific ratio can bring the maximum operating efficiency to the power station. In fact, the ratio between photovoltaic modules and inverters needs to comprehensively consider a variety of factors, such as light conditions, installation site, component factors, and inverter factors.
【Light altitude factor】
The irradiance varies greatly in different regions, and the greater the solar elevation angle, the stronger the solar radiation. Second, the higher the altitude, the stronger the solar radiation. For example, in the Qinghai-Tibet Plateau, the solar radiation is the strongest, but the worse the heat dissipation of the photovoltaic inverter is, the inverter must be derated, so the proportion of photovoltaic modules is small.
【Installation site factors】
1. DC side system efficiency
The power station adopts different installation methods, and the DC side loss is very different. In a distributed photovoltaic power station, the components are connected to the inverter in DC. If the photovoltaic inverter is installed nearby, the DC cable is very short, and the efficiency of the DC side system can reach 98%. In a centralized ground power station, due to the long DC cables, the energy from solar radiation to photovoltaic modules must pass through DC cables, combiner boxes, DC distribution cabinets and other equipment. The efficiency of the DC side system is usually about 90%.
2. Grid voltage changes
The rated output maximum power of the inverter is not static. When the grid voltage drops, the inverter cannot reach the rated power. For example, a 33Kw inverter, the maximum output current is 48A, the rated power is 33kW, the rated output voltage is 400V, 48A*400V*1.732=33.kW, if the grid voltage drops to 360V, the inverter output power is 48A*360V *1.732=30.kW.
3. Inverter cooling conditions
There are requirements for the installation location of the photovoltaic inverter. Generally, it should be selected in a place with good ventilation and direct sunlight. If the above installation conditions cannot be met, derating must be considered, and fewer components must be matched.
【The component itself factor】
The design life of photovoltaic modules is 25 to 30 years, and most module factories will leave a positive tolerance of 0-5% in the production design, so that the modules can still reach 80% work efficiency after 25 years of use. Secondly, the power temperature system of the module is about -0.41%/℃, that is, when the temperature of the photovoltaic module drops, the power of the module will increase.
[Photovoltaic inverter's own factors]
1. Inverter working efficiency and lifespan
The efficiency of the inverter is not fixed, at 40% to 60% power, the efficiency is highest, and below 40% or more than 60%, the efficiency will decrease. The life of the inverter has a lot to do with the operating temperature. The temperature of the inverter is the highest during long-term high-power operation. According to the test, the life of the inverter when it works at 80-100% power for a long time is longer than that at 40-60% power. about 20% lower.
2. The best working voltage range of the inverter
When the working voltage is around the rated working voltage of the inverter, the efficiency is the highest, the single-phase 220V inverter, the inverter input rated voltage is 360V, and the three-phase 380V inverter, the inverter input rated voltage is 650V.
3. The output power and overload capacity of the inverter
The output power of photovoltaic inverters of different brands of the same power segment is also different. The inverters produced by some companies do not have overload capacity. Therefore, the ratio of photovoltaic inverters and components is not arbitrary, otherwise they will suffer from Invisible losses, various factors should be considered comprehensively when installing photovoltaic power plants.