Update: The client decided to simply move the 2nd inverter next to the 1st one along with its batteries to enable parallel mode using data comms. Now, he needs to lay down new wires to connect the PVs from the 2nd inverter original site (250-400 m distance between PVs and inverters/batteries). The installers are planning to pull thicker 6mm^2 copper wires from the original site back to the new one , use 4mm^2 wires that are already laid down (connecting the 2nd inverter and PVs) and connect them. In my opinion this is a superior solution to running 2 inverters in any configuration and hoping that the phase synchronization without data comms works out long enough in grid outages before critical fault errors or worse events happen.
Parallel function of 2x50kW hybrid triple-phase Deye inverters without data comms
- Thread starter landau
- Start date
shadowmaker
Solar Wizard
As I already said my Deyes can't work during outages. Well, they can charge batts, but they can't supply any power to my loads as they are now. I'd need to flip one breaker "ON" to let them connect to my main panel. During outage they are still connected to each other through LOAD-ports, but that line has breaker before it connects to my main panel and it is currently "OFF" as I was afraid to test it when heating season was still on. I think I can try it now but I need to isolate it to something smaller than my whole main panel and monitor voltage.
timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
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- 21,280
Please be careful.
You have a nice system. And a lot of money and sweat invested in it.
I just don't want to see anything bad happen.
Brucey
Solar Wizard
Yes no need to prove the theory with expensive physical white smoke.
shadowmaker
Solar Wizard
They should use some online calculator for the wire size. My 44kWp array is 100m from my "Solar Corner" and I'm using 16x 25mm2 aluminium (+ one 16mm2 copper for ground) to get voltage loss under 1% which is a bit overkill as 2-3% is still ok. I have four strings and every string has four 25mm2 wires: two plus and two minus to transfer power to my inverters.
ksmithaz1
Solar / EV Junkie
Just curious, why not? Two identical frequency independent oscillators tied together will naturally synchronize if something doesn't hold them out of sync. The natural state should have them sync up. If the outputs are independent with a common neutral the strongest signal should pull them in. @Hedges or one of the other EE types should have some input on that, but in the distant past we had trouble keeping oscillators out of sync. I should ask my brother.
shadowmaker
Solar Wizard
I will. I haven't enabled them to work during outages just because I was a little afraid about magic smoke. Luckily outages are so rare here that I can even keep them as they now are and benefit their load sharing only, but I bet I can figure out something to get around this. Maybe I just ditch my FLA battery completely or use only one Deye during outages or something.
ksmithaz1
Solar / EV Junkie
I like this analogy. So say the truck is pulling two motorcycles tied together pulling a 4-wheel trailer at 10MPH, each with a cable on the two front corners. They disconnect from the truck, but both bikes maintain 10mph. They will stay in sync pulling the trailer as long as no outside force independently disconnects them for long enough to fall out of sync, and they stay reasonably equidistant on the road. One can pull a little harder than the other, you will be fine as long as they don't go too far out.
They can remain at the same pace as long as they can tell if the trailer is getting crooked.
Quattrohead
Solar Wizard
I think of it like me and my little brother being pulled along on our bikes behind the tractor and letting go, you stay together for a little bit but eventually one or other will slow down compared to the other and then where acway forms a concerned extremely bad things start to happen very quickly.
I'm not sure why you are concerned about your batteries being different, just set them all up as a single bank, monitor/control the lithium and let the lead acid ones lope along for the ride. It's not ideal but it should not damage anything.
I'm not sure why you are concerned about your batteries being different, just set them all up as a single bank, monitor/control the lithium and let the lead acid ones lope along for the ride. It's not ideal but it should not damage anything.
shadowmaker
Solar Wizard
In summer that would be ok as my batts are almost always full, but in winter my batts are always empty/close to empty and FLA hates that. If they are combined as a single bank, then I'd need to grid charge ~100kWh almost daily to keep my FLA happy. With separate banks that's not a problem.
Also sorry for the OP that we are discussing about my setup in your thread. But you can probably see the up and downside of my system and understand why it is important to use comms usually.
I don't mind the discussion at all, on the contrary it was the reason why I persuaded the client to bite the bullet and transfer the inverters together. Your configuration relies on the utility grid to sync them - an efficient solution if power outages are short and few. When you lose the utility grid those inverters can drift away due to some external pertubation of sufficient magnitude or by pure chance via statistical fluctutations - when we consider the limit in which t goes to infinity the probability for them falling out of sync (drifting away from eachother significantly) approaches unity/1.
The last statement is a metaphor about bad outcomes and non-zero probabilities. Given enough time their decoupling will happen if their frequencies/phases are not perfectly aligned and if there are fluctuations, those are realistic assumptions in this case.
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