Very confused - Need help with ac coupling IP6048

[svanand]

I have a grid tied 8.4KW system (with APSystems microinverters) and want to add batteries to use during times when the sun doesnt shine
I have 45KWh of batteries (LiFePO4) and the sungoldpower ip6048 inverter. I selected this inverter since it can do ac coupling
My power usage is peak 8KW but typical only 2KW (I live in a hot place)

My plan was to wire the system like shown in the picture. My guess was that
- During the day when the sun is shining and full generation
Solar generation (8.4KW) feeds into home (2KW) and rest to charge batteries
When batteries are full, feed the remaining power to the grid
- During the day when the sun is not shining as much, or during the night
Solar generation (say 0KW or 1KW) feeds into home
Grid supplies additional power for use
- During peak summer months, same like day when sun isnt shining as much

Main points of confusion
- The inverter says peak 6KW, so does that mean that it can pass through the remaining (upto 8KW during hot nights) from the grid, and not trip
- If I have time-of-use metering (say free nights), can I turn off the battery use at 8pm and consume all the power from the grid


Thank you very much in advance

 

[sunshine_eggo]

Can the IP6048 frequency shift?
Can it sense surplus power on its output and use it for charging the battery?

If not, it can't be used for AC coupling.

For inverters capable of AC coupling, there is usually a buffer required. IIRC, it's generally 1:1 or sometimes 1:1.2, i.e., the Grid supplying inverter must be 20% greater than the GT PV.

It helps to remember that GT inverters are designed to output maximum available power to an essentially infinite sink, i.e., the grid. They do not self-regulate unless the sense a bad grid.

AC coupling elegible inverters sense the surplus AC on their output and use it to power the charger to charge the batteries. Once the batteries are full, the inverter shifts it's frequency somewhere far enough from 50/60Hz to cause the GT PV inverter to disconnect. If the inverter can't shift the frequency, the GT inverter wants to shove it's entire output at the "grid" inverter even if there's nowhere for the power to go (no loads and battery is full).

 

[svanand]

Can the IP6048 frequency shift?
Can it sense surplus power on its output and use it for charging the battery?

If not, it can't be used for AC coupling.

For inverters capable of AC coupling, there is usually a buffer required. IIRC, it's generally 1:1 or sometimes 1:1.2, i.e., the Grid supplying inverter must be 20% greater than the GT PV.

It helps to remember that GT inverters are designed to output maximum available power to an essentially infinite sink, i.e., the grid. They do not self-regulate unless the sense a bad grid.

AC coupling elegible inverters sense the surplus AC on their output and use it to power the charger to charge the batteries. Once the batteries are full, the inverter shifts it's frequency somewhere far enough from 50/60Hz to cause the GT PV inverter to disconnect. If the inverter can't shift the frequency, the GT inverter wants to shove it's entire output at the "grid" inverter even if there's nowhere for the power to go (no loads and battery is full).

The marketing brochure mentions AC coupling clearly, so Im guessing it can frequency shift, but not sure what happens if it sees the GT inverter producing more than it can feed back to grid
If my home load was under 6KW, I wouldnt be as worried and make it into a 'micro-grid' system and pull from grid only when there is no sun and batteries are dead

 

[sunshine_eggo]

The marketing brochure mentions AC coupling clearly, so Im guessing it can frequency shift, but not sure what happens if it sees the GT inverter producing more than it can feed back to grid
If my home load was under 6KW, I wouldnt be as worried and make it into a 'micro-grid' system and pull from grid only when there is no sun and batteries are dead

Does the unit list a max GT PV or AC Coupling power?

 

[svanand]

Does the unit list a max GT PV or AC Coupling power?

Unfortunately the manuals dont mention it. It does mention max ac input as 40A (im guessing it can consume 120*2*40=9.6KW from grid and pass it through) and Grid Output as 25A (im guessing it can output 120*2*20=4.8KW, but not sure if it is from battery to load/grid)
The manuals are quite confusing, thats why rather than looking at the sungoldpower model, Im also checking people's experience with the MPP solar inverter which seems to be exactly the same one

 

[sunshine_eggo]

Unfortunately the manuals dont mention it. It does mention max ac input as 40A (im guessing it can consume 120*2*40=9.6KW from grid and pass it through) and Grid Output as 25A (im guessing it can output 120*2*20=4.8KW, but not sure if it is from battery to load/grid)
The manuals are quite confusing, thats why rather than looking at the sungoldpower model, Im also checking people's experience with the MPP solar inverter which seems to be exactly the same one

The GT PV inverter will go on the AC output, not the input, so I would assume it's also limited to 25A.

 

[svanand]

The GT PV inverter will go on the AC output, not the input, so I would assume it's also limited to 25A.

Great, that answers one of my primary concerns.
So, during the day, if Im producing more than I consume, upto 25A can be fed back into the grid, any more, it will 'fault' (not good)
During the night, the batteries can provide upto 6KW to the load, and the rest is passed through from grid to load, and that is limited to 40A (or 9.6KW)

Hopefully this inverter can 'indicate' to my microinverters to stop production (or reduce) if it finds that my SolarProduction - Load is more than 25A, and it can avoid the fault

I will try to test it out (when I feel brave with mains voltage, or get an electrician to help me try out)

 

[sunshine_eggo]

I am not confident you can safely couple a 6kW inverter to a 9.6kW GT inverter. This is consistent across all brands that publish data.

AC-coupling and the Factor 1.0 rule [Victron Energy]

www.victronenergy.com

 

[svanand]

I am not confident you can safely couple a 6kW inverter to a 9.6kW GT inverter. This is consistent across all brands that publish data.

AC-coupling and the Factor 1.0 rule [Victron Energy]

www.victronenergy.com

THAT is a problem. So I bought a wrong ac coupled inverter and need to get one that can handle at least 8KW
Any recommendations (is SOL-ARK, SA-LIMITLESS-15K a viable option). This seems a lot expensive, anything cheaper you would recommend

 

[sunshine_eggo]

THAT is a problem. So I bought a wrong ac coupled inverter and need to get one that can handle at least 8KW
Any recommendations (is SOL-ARK, SA-LIMITLESS-15K a viable option). This seems a lot expensive, anything cheaper you would recommend

I don't know the limit, but the sol-ark series publishes their AC coupling limit. I think they have units smaller than 15K, but yeah... spendy.

 

[Ampster]

Hopefully this inverter can 'indicate' to my microinverters to stop production (or reduce) if it finds that my SolarProduction - Load is more than 25A, and it can avoid the fault

When the grid is up, it seems like your 9.6 kW GT inverter will trip your 25 Amp breaker. The breaker for a 9.6 kW system should be 50 Amps so even in a situation with the grid up you will have an overcurrent situation. This is a problem with the capacity of the 6048 inverter to pass through the GT solar to the grid.
This has nothing to do with frequency shift and AC coupling which only ocures in a grid down situation.

 

[svanand]

When the grid is up, it seems like your 9.6 kW GT inverter will trip your 25 Amp breaker. The breaker for a 9.6 kW system should be 50 Amps so even in a situation with the grid up you will have an overcurrent situation. This is a problem with the capacity of the 6048 inverter to pass through the GT solar to the grid.
This has nothing to do with frequency shift and AC coupling which only ocures in a grid down situation.

Hmm, so does it mean, I just connect 2 of these 6048 in parallel (it supports upto 6 in parallel apparently), we should be OK?
That would mean the existing 6048 isnt wasted, and I can accomplish my goal with just an additional 6048 which is a lot cheaper than the solark 15k

 

[sunshine_eggo]

Hmm, so does it mean, I just connect 2 of these 6048 in parallel (it supports upto 6 in parallel apparently), we should be OK?
That would mean the existing 6048 isnt wasted, and I can accomplish my goal with just an additional 6048 which is a lot cheaper than the solark 15k

That would seem to work. Might check with your vendor for confirmation.

 

[Ampster]

Hmm, so does it mean, I just connect 2 of these 6048 in parallel (it supports upto 6 in parallel apparently), we should be OK?

I only talked about the AC pass through from your GT inverter and I do not know all the details of how the power going to and from one sub panel to two 6048s. Presumably your GT inverter would be connected to the sub panel with a 50 Amp breaker and its generation would cover the load in the sub panel and any excess would be exported from the sub panel to the EG4s. i presume the EG4s would each be connected to the sub panel with separate 25 Amp breakers

That would mean the existing 6048 isnt wasted, and I can accomplish my goal with just an additional 6048 which is a lot cheaper than the solark 15k

I do not know what the capacity of the EG4s is in terms of AC coupling to GT inverters when the grid is down. i agree with the concept that @sunshine_eggo mentioned about certain relationships betwee the grid forming (EG4) inverter(s) and the GT (grid dependent) inverter(s). If it were me, I would want to verify that capability with a user who is actually doing it while the grid is down. The term AC coupling can be used in many ways and I tend to think of it only in a situation when the grid is down and that is where it is complicated and frequency Watts becomes important in terms of the interaction. Since in that situation there is no grid to act as a buffer and the GT inverter output can only go to the loads or the batteries or the GT needs to be modulated or shut down.
The answer to whether it will accomplish you goal may depend on whether you just need functionality when the grid is up or when the grid is down. I would not trust a "yes it will work" answer from a vendor unless your question is very well articulated in terms of grid up or grid down. My prior inverter had a very mature and robust AC coupling algorithm which worked very well. I have discoverd challenges with the SolArk being able to leverage my GT inverters when the grid is down. Since grid down only happens a few times a year, I have some workarounds and the battery capacity of my SolArk installation is enough to last me several days even if I wee to get no generation from AC coupling my GT inverters.

 

[Hedges]

I am not confident you can safely couple a 6kW inverter to a 9.6kW GT inverter. This is consistent across all brands that publish data.

AC-coupling and the Factor 1.0 rule [Victron Energy]

www.victronenergy.com

With one notable exception.

Page 128,
"Observe the following:
PAC max of the PV inverter = 2 x PAC nom of the Sunny Island
PAC max of the wind power inverter = PAC nom of the Sunny Island"

https://files.sma.de/downloads/SI4548-6048-US-BE-en-21W.pdf

Unfortunately, for US model this is only off-grid. On-grid, that would be too much current passing though relay.
The European model operates at twice the voltage, so GT PV power can be twice island forming battery inverter power.

I presume the load-dump situation can only dump about 1x Sunny Island's power at a time, since it couldn't swallow 2x prior to completing frequency shift.

 

[eleceng1979]

you have the wrong inverter or at the least need further help from the manufacturer.
1. UL database has no certificate records for this manufacturer, their product name, and website makes claims to be certified, yet no callout in manual specs. The voltage codes used in the software setup do not match any approved UL codes.
2. The inverter has no freq shift adjustment. I doubt the inverter output is bi directional. Hooking PV grid tie inverter to output will more than likely end with a smoke show. The inverter cannot regulate its output to reject/reduce ac coupled power
3. The ac coupling feature enable “probably” uses the ac generator input to accomplish this, on the front side of the inverter. It seems like a marketing gimmic to say it is ac couple compatible, but due to #1 above it is not the normal ac coupling and some gimmic/hack to bring it into the gen port. All of this is assumptions. You need help from the manufacturer, not a forum.

 

[svanand]

you have the wrong inverter or at the least need further help from the manufacturer.
1. UL database has no certificate records for this manufacturer, their product name, and website makes claims to be certified, yet no callout in manual specs. The voltage codes used in the software setup do not match any approved UL codes.
2. The inverter has no freq shift adjustment. I doubt the inverter output is bi directional. Hooking PV grid tie inverter to output will more than likely end with a smoke show. The inverter cannot regulate its output to reject/reduce ac coupled power
3. The ac coupling feature enable “probably” uses the ac generator input to accomplish this, on the front side of the inverter. It seems like a marketing gimmic to say it is ac couple compatible, but due to #1 above it is not the normal ac coupling and some gimmic/hack to bring it into the gen port. All of this is assumptions. You need help from the manufacturer, not a forum.

Sadly, the manufacturer (sungoldpower) just says ac coupling is not supported, so i have to look at other options, what I have is a $2000 paperweight (and a heavy one at that)
Unfortunate that they mention ac coupling in highlights in their page but refuse to support it

 

[solar8484]

Did Sungold explicitly tell you in writing that AC coupling is not supported in ip6048? If so, that seems like outright fraud as their web pages clearly show otherwise and you can dispute it with your credit card company.

 

[eleceng1979]

If you think false advertising about AC coupling is fraud, provide me their UL certificate.

 

[zanydroid]

Sorry to hear about this outcome with the inverter.

IMO AC coupling is very bleeding edge on these budget inverters. Might need to check back in a year and see how the two or three threads on the AC coupling budget inverters net out.

LVX6048WP (spelling?) and megarevo 8K. Not sure what else.