The capacity of the PV module and the capacity ratio of the inverter are commonly referred to as the capacity ratio. The reasonable capacity ratio design, should be integrated with the consideration of specific projects, the main factors including irradiance, system loss, the efficiency of the inverter, the service life of inverter component installation angle and so on. Cause the inverter accounts for only about 5% of the system cost, in the distributed solar power plant system, rely on components over the capacity ratio as to reduce the quantity or power of the solar powered inverter, the investment income is very few, but also bring other problems, specific analysis is as follows.
1.Different regions have different irradiance
According to the standards of the national wind energy assessment center, Chinese solar energy resources are divided into four categories. Even in the same resource area, there is a big difference in annual radiation in different places. For example, in the area of Tibet and Qinghai which are the same type of resources, the annual radiation of the Tibet is 7998MJ/m2, while Qinghai is 6815MJ/m2. This means that the same system configuration, which is the same capacity ratio, the region’s power generation capacity of Tibet is 17% higher than Qinghai. To achieve the same amount of power generation, you can achieve by changing the capacitance ratio.
2.System loss
In the solar power system, the energy from the solar radiation to the PV module, through the DC cable, confluence box, DC distribution to the inverter, which has the loss of each link. That is, in the same assembly capacity and inverter capacity, loss due to various objective existence, the actual output capacity of the inverter is only about 90% of the rated capacity, even in the best time of light, the inverter is not full work.
3.Inverter efficiency
The efficiency of the inverter is not constant, there is the loss of power switching devices and magnetic losses; when it is in low power, the efficiency is relatively low; the highest efficiency at 40% to 60% power; when more than 60%, the efficiency gradually reduced. Therefore, the total power of the PV power should be controlled between 40% and 60% of the inverter power to achieve the best efficiency.
4.The service life of inverter
Solar power inverter is an electronic product, there is a great relationship between the reliability and the operating temperature of the inverter, the temperature of capacitors, fans, relays and other components increase of 10 degrees, while the failure rate can be increased by more than 50%. The operating temperature is related to power, according to statistics, the service life of inverter works in the 80-100% power power is about 20% lower than in the 40-60% power for a long time.
5.The best inverter operating voltage range
The operating voltage is about the rated voltage of the inverter, while the efficiency is the highest, the single-phase 220V inverter, the inverter input rated voltage is 360V, the three-phase 380V inverter, the inverter input rated voltage is 650V. Such as 3kva inverter, with 260W components, working voltage 30.5V, with 12 working voltage 366V, the total power of 3.12kW is the best. 30KW inverter with 260W components, connected to 126 components, each of the 21 strings, the voltage is 640.5V, the total power of 32.76kW is the best.
Above all, when the power of the system between the rated power of 40-60%, the highest efficiency and the longest service life. In order to achieve the best performance of the inverter, according to different lighting conditions, components and inverters have different ratio.
SSP3118C3 1.5KVA & 3KVA Solar Inverter Off Grid MPPT Transformerless Type
Key Features
1. Pure sine wave 3KVA solar inverter off grid MPPT
2. Cold start function
3. Remote panel available
4. Auto restart while AC is recovering
5. Overload and short circuit protection
6. Compatible to mains voltage or generator power
7. Selectable charging current based on applications
8. Configurable AC/Solar input priority via LCD setting
9. Built-in MPPT solar charge controller
10. Smart battery charger design for optimized battery performance
11. Selectable input voltage range for home appliances and personal computers
