With the solar power technology keep improving, the solar panel production and inovation leading the industry to emerge with more and more solar system applications, like BIPV, agrivoltaic system, pv carport, pv ground mounting systems, solar battery storage,rooftop on grid solar system, all those applicaitons needs to consider basic solar panel and inverter current matching when configure the system, when solar panel power from 250w to 700w, the voltage and current has changed greatly, to match the change, inverter manufactures also needs to imporve their technology to keep up. Or, in cases, if you want to use given capacity inverter in your solar system, you would also need to consider the current issue to find the matching solar panels to be used.
01. Inverter Technical Parameter Analysis
In the datasheet of the inverter, we can find the following important data: the maximum current per MPPT, the number of MPPTs, and the maximum input numbers.
According to the data in the table above, it can be seen that the maximum inputs here is 8, and the number of MPPTs is 4. According to the circuit schematic diagram (as shown in the figure below), every two inputs of the inverter correspond to a group of MPPT. That is to say, each MPPT can carry a maximum of two solar panel strings. From the technical parameter table above, the maximum input current for each MPPT is 26A , which can be seen as 2 the situation:
1. When each MPPT is connected to two solar panel strings, the total input current of these two strings cannot exceed 26A. As the two strings are connected in parallel, the current of each string cannot exceed 13A. you need to check for your solar panel options to make sure the maximum current of the solar panel does not exceed 13A.
2. if you are using solar panel maximum current higher than 13A, you would have to consider using 1 string of solar panel to connect with the MPPT, that case, your solar panel installation capacity would be greatly limited (considering the MPPT voltage range would also limited the solar panel numbers in one string.).
02. Solar Panel Parameter Analysis
When selecting solar panels, the maximum power current (Impp) can be found in the technical parameter below. When multiple solar panel serial connected in a string, current remains the same for each solar panel in the string, this current can be used to verify whether it matches the input current of the inverter.
As shown in the table below, if the selected solar panel is 670Wp, the optimal working current is 17.37A.
03. Solar Panel And Inverter Current Matching Verifying
Based on the above analysis, if you are considering 670Wp solar panel in your solar system, the working current of each string is calculated at 17.37A. If each group of MPPTs is connected to two solar panel strings, the total current is 17.37 * 2=37.74A, which is bigger than the maximum input current allowed by the inverter of 26A. Therefore, each group of MPPTs cannot be connected to two strings, only one string can be connected. If one string is connected, the current is 17.37A ＜ 26A, which can meet the requirements.
If using 670Wp solar panel, the whole inverter can only connect up to four solar panel strings.
If you want to connect with 8 solar panel strings, you should reconsider your solar panel options, and the optimal working current of the solar panel should be ≤ 13.0A (26/2).
So, when choosing solar panels and inverters, the current matching should be considered firstly, to make the configuration right to ensure the normal operation of the system.
