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Fronius ECO Configuration for East-West system


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I hope you can help me. I am trying to configure an east-west system, 778 JA Solar 270 W panels in total, 389 per side with Fronius ECO 27 inverters and I don't seem to be able to find the right string configuration.
If I try to use the maximum number of strings, the MPP voltage too low and the current to high:

Or if I try to reduce the number of strings, the open circuit voltage becomes too high:

I have tried using different panels and number of panels per string or having a south-facing system, but nothing seems to work with this inverter.
I seem to be in an impasse and any recommendation will be much appreciated! I am also attaching my design file for reference. 

Thanks for your help!


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Hi ZhAta,

it is true that formally the MPP voltage is too low and the current is too high if you connect 6 x 22 JA Solar JAP6(K)-60-270/4BB modules to a Fronius Eco 27.0-3-S. With the check temperatues of 15°C (U_Mpp_Max), 70°C (U_MPP_Min) and -10°C (U_OC) there is no way around it.

You could have 5 x 24 modules, then the current limit isn't hit and the MPP voltage limits are fine, but still the Open Circuit voltage will be exceeded.

But the question is, how much energy do you loose if you connect your system like this? I simulated your system with one-minute resolution (to get a realistic estimation of the clipping losses) and it looks ok:


The down-regulation on account of the MPP voltage is relatively high, 1287 kWh, but it is still only -0,76% of you energy that you loose. It is then up to you, the planner, to decide if you want to accept these losses. If you are bound to these specific modules and this inverter, I guess you have to :)

You can try different configurations, simulate them and see what you prefer.

Hope that helps, kind regards,



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