Off Grid 3P 15k Quattro's with AC Coupled Solar

Q&A and troubleshooting
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1

Existing off grid system is as follows -

  • 3 x 48V/15k Quattros in 3 Phase - Switched as a group.
  • Cerbo GX
  • 110kwh of BYD Lithium.
  • 4 x 450/200 MPPT RS.
  • 3 x 5kw SMA Sunnyboy MPPT’s on the Quattro’s AC Output’s controlled w/ frequency shifting through the PV Inverter Assistant (1 x Sunnyboy on each phase).
  • Single phase 16kva Generator powering a 15k MultiPlus-II as a charger only onto the DC bus (networked to Cerbo w/ MK3 interface).

I had planned to add another 5kw Sunnyboy to L1 (2 in total on this phase, 1 on each of the other phase’s) - The PV inverter assistant mentions to that “each phase must have the same solar power installed” - What are the implications of not following this? Being that the AC coupled solar is a variable charge source between phases, I can’t understand how this is an issue?

I also plan to upgrade the single phase generator to a 3 phase unit into each of the Quattro’s - How does frequency shifting on the AC Output work when the Generator is running? Do I just program the generator to stop at around 95% SOC to allow the Quattro’s to be able to frequency shift, to throttle back the Sunnyboys when required?

Thanks in advance.

2

Good Morning,

You can use different pv inverter power in each phase but never more than the 1 to 1 rule, I use just 2 phases already for 11 years, the 3rd is still spare.

The generator running and solar is indeed a bit tricky, I would switch the gen off already at below 90% soc with solar, to give the PV inverters enough space for frequency control reduction.

Regards, Jeroen.