Will two Growatt SPF 6000 ES PLUS inverters connected in parallel still utilise solar and grid power at the same time?

[agrogers]

The short question is:
1. The SPF 6000 ES Plus manual says "Solar and utility grid can power loads at the same time"
2. However does this still apply when two are connected in parallel?

The reason I ask is that I currently have two 'Must' inverters where the manual says both solar and grid can power loads simultaneously (SUB mode). However this does not work for us and I believe it is because they are connected in parallel. The manual is referring only to single unit operation. I queried their support and when I pointed this out the service guy stopped communicating with me. I discovered this, perhaps on this forum, when a person commented about a Growatt inverter that also operated the same way. So I am nervous I will end up with two new, better quality inverters with exactly the same problem. Hard to get good support on these topics here in Myanmar.

https://www.ginverter.com/upload/file/SPF_6000_ES_Plus_User_Manual_EN_202212.pdf

 

[Hedges]

The manual you linked page 27 does show parallel connection of both grid and loads.

It says battery cable lengths must be identical.
It doesn't say that about AC wiring, but that should be too.

If you do draw more current from grid than one can pass through, you may have problems.
Schneider doesn't try to do that, apparently because switching won't be exactly simultaneous. They use a higher current external relay.
My Sunny Island support it, but despite 40' of 6 awg exactly matched, I saw about 3:1 imbalance in current. That was due to Square-D QO breakers. Some other DIN rail breakers were better matched.

You may be able to find a higher wattage single inverter. SolArk in the US has 12kW models. Deye or another may have it for your market.

 

[agrogers]

Thanks for the reply. I think you might have missed my main query... or I misunderstood your answer. Yes, pg 27 confirms the parallel connection. Connecting up to 6 units is pretty cool. I might need to do 3 phase one day. Your comments about battery cable length is good - I have not been careful with that. But I dont think that is my issue. And you are right, I just found a 12kw Deye over here - I have read they are good quality but expensive.

My confusion is whether or not two of these inverters connected in parallel can continue to run in "SUB" mode. That is, they use solar only until it is not enough and will then get the extra from the grid.

I wondered whether this inverter (or inverters of this type generally) connected in parallel usually can (or cannot) operate the way I described.

 

[Hedges]

If "SUB" mode means the inverter does zero-export based on CT around its grid input, that ought to (might) work with inputs and outputs paralleled. Each would regulate its inverter output up to maximum, but never exporting.

That does require they be grid-interactive, able to sync output to grid. Any grid-tie inverter can do that much. There is also the possibility that with outputs also paralleled, they tussle with each other to supply loads. Or, the output of one backfeeds through the other to grid. The other sees that and reduces output to zero, but the one doing it has no idea it is backfeeding through the other.

What happened when you tried?

Can you split your loads into two separate circuits, so outputs aren't paralleled?

I have not tried this with my Sunny Island; that would be DC coupled PV pushing battery above voltage inverters want, so they export.
I have all AC coupled PV. On-grid, they export any surplus. The zero-export solution is a 3rd party meter with CT at grid connection, and communications telling GT PV Sunny Boys to reduce output. That would work independent of however many Sunny Islands with grid relays in parallel, but if current imbalance exceeded what one relay could handle that would be a problem.

Some inverters like mine have simulated output resistance (voltage droop at higher current) to facilitate load sharing. Others like Victron do not, and say AC wires must be perfectly matched (even for off-grid use.) That could also affect this issue.

It may be a system with CT at grid connection can do what you want, if export must be avoided.

 

[agrogers]

This is not a grid tied system - so no export.

By SUB I mean "Solar energy provides power to the loads as first priority. If solar energy is not sufficient to power all connected loads, solar and utility will power loads at the same time. Battery provides power to the loads only when solar energy is not sufficient and there is no utility."

I will do a bit more research with the extra info you supplied. Thanks.

 

[agrogers]

Now installed these and I can confirm that the inverters in parallel do work as they should... solar first and then utility if needed... with a strange exception which I describe here https://diysolarforum.com/threads/w...6000-es-in-parallel-be-wasting-15-amps.78691/

There is 15A of wasted current going somewhere but I cant work out where.