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How to design a large scale pv system

Michalis Angeli

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Hello, I would like to ask ho to design a large scale pv system. I am working on a 1 MW  (999.78 kW) project.
More specific i use 1754 panels Trina 570 W and 8 inverters sungrow 250-HX.

I am trying to define the system and i can't to define my strings in programm. I have 7 inverters with 18 panels in series in 11 mppt inputs and 21 panels in series in the last mppt input.

And obviously, at 8th inverter i have again 18 panels series in 11 mppt inputs and the last one mppt input has 23 panels in series.

Calculations: 18 * 11 + (21*1) = 219 panels in each inverter. These strings refer to the 7 first inverters.
18*11 + (23*1) = 221 panels in each inverter. These strings refer to the last inverter.

This scenario, described above i would like to define in programm, but i don't mangage it.

Although, the power sharing it's okay the message the inverter is strongly oversized, prevented me to proccess.

I use the same panels in the whole system. The reason that i use subarrays is because i try to define my system as i described above. Is there any ohter way to design that system to avoid the solution with subarrays given that the orientation and azimuth stay the same.

I attach some pictures from my system in order to help you.

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Dear Michalis Angeli

The error message indicates that the inverter power is strongly oversized, with a Pnom ratio of 0.5. The Pnom ratio is the ratio between installed Nominal PV Power (125 kWp) and the inverter (250 kW). Normally the Pnom ratio is around 1.25.

You correctly use the subarrays, MPPTs and Power sharing, though the installed Nominal PV Power is too small compared to the inverter.


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Dear Linda,

I have changed my type of inverter, and i am trying to define the system and I face this problem "The array MPP Voltage may not attain the inverter minimum voltage for full power". 

Shoul I increase the modules in series? But if i go forward with this solution, the total number of modules will increase and i don't want this happen.

Note that the problem is the same ony in sub-arrays #2,4,6 etc. In this sub-arrays I have 2 strings from 20 panels in each one.


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By clicking on the Sizing button you will see a graphic with the Array Voltage Sizing, showing the different limitations to consider when choosing inverter and sizing your system. You can consider choosing another inverter with another voltage range.

An orange message is a warning, but you can still run your simulation. 

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  • 5 months later...

Your string configuration should match the voltage and current requirements of your inverters. For the Sungrow 250-HX, you’ll need to check the maximum and minimum input voltage and the MPPT voltage range to ensure that your strings of 18 and 21 (or 23 for the last MPPT input) panels are within these specifications. It’s common practice to slightly oversize PV arrays relative to the inverter capacity to account for losses and to maximize energy production, especially in areas with less-than-ideal solar irradiance. However, too much oversizing can lead to inverter clipping during peak production times. The message about the inverter being “strongly oversized” suggests that your current design may exceed the inverter’s capacity more than is typical or recommended.

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