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How much power in AC Coupling can be connected to the GEN port of a Deye Sun 8k Inverter?

rogerhimes1978

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I am analyzing whether to buy a Deye Sun 8K hybrid inverter. I want to know how much power in AC can be connected to the GEN port of this hybrid inverter beside the 10,400W PV max input in their spec sheet.
My current solar plant is 17.8 kWh all working with hoymiles inverters (40 x 440W panels).

I want to have as much as 30kWh of Batteries for backup and I would like my system to be able to work in off grid mode for prologned grid shutdown periods.

Someone suggested we could use the GEN Port of the Deye inverter in AC Coupling (panels using microinverters) in order to increase the system's charging capacity and general energy availability during the day, but I am afraid of burning the house's circuits because of overload or damaging inverter/batteries.
If anyone has experience with this inverter type and can offer a recommendation, i would appreciate your advice.
 
Generally speaking AC coupling happens on the output side of a hybrid inverter, not one of the inputs. Have you tried to find the installation manual for the inverter you’re looking into? The capacity on most units for AC coupling closely matches the output capacity of the inverter due to the unit needing the ability to take on the full power of the system it is coupled to for short durations without damage or shutting down. So an 8kW inverter should be able to AC couple roughly 8kW AC of PV (typically close to 9.5kW DC)
 
Generally speaking AC coupling happens on the output side of a hybrid inverter, not one of the inputs
As far as I know the gen port is bidirectional as are many of the ports on hybrid inverters. As you mention, AC coupling generally happens on the AC out side because when the grid is down the AC in relay opens so the AC in has no connection. The critical load s panel is typically where the GT grid dependant inverters are connected so that they can get the AC wave form from the hybrid grid forming inverter. At least that is how mine works and I but I understant the SolArk uses the Gen port and maybe that is the same with the Deye. . Your experience may be differenent in which case please share
As far as the OP's question about AC coupling capacity that is something that may depend on the battery capacity installed in the SolArk. I do not think it is related to inverter capacity but more about the battery capacity and the algorithm in the hybrid grid forming inverter. For example my Outback Skybox has an inverter capacity of 5k but an AC coupling capacity or 7kW If the Deye has the same algorithms it may work but no gaurantees because the Deye is not UL listed and the SolArk has a UL listing. Take your chances and report back so other users can benefit.
Other readers with experience AC coupling a Deye to a GT inverter may want to respond.
 
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If it is like Sol-Ark, I'm not sure that AC coupled PV can add to battery charging, because DC coupled PV goes to high-voltage rail. I think charging from grid or GT PV also goes to same HV rail, so DC/DC battery charger would be the limit.

I think AC coupled might work for additional AC loads, while DC coupled PV might work for additional battery charging.
Of course, a random SCC wouldn't communicate regarding desired current/voltage.
Could be buying multiple hybrids that are stackable would be the best way to add battery charging capacity.

And of course my favorite, orient multiple PV arrays differently. With 17.8kW split into two arrays 90 degrees apart, should peak around 12.6kW (STC), 10.7kW (PTC) so might fit a single inverter pretty well.
 
If it is like Sol-Ark, I'm not sure that AC coupled PV can add to battery charging, because DC coupled PV goes to high-voltage rail. I think charging from grid or GT PV also goes to same HV rail, so DC/DC battery charger would be the limit.
@RCinFLA gave an good explanation of that in another thread. I do not know about the SolArk but my Outback Skybox can use the AC coupled energy that passes through the Skybox to charge the batteries. It may be unique to the setting in the Skybox but conceptually is can happen. I do not understand it enough to know if the high voltage rail is an issue. As he explained there is a difference between how high frequency and low frequency inverters operate and that may relate to the "high voltage rail"?
 
It is a rule of thumb to have more kW battery inverter than grid-tie inverter. (grid-tie : battery_inverter ratio should be less than 1:1)

You can use the new big 16kW Deye/Sunsync unit ... but even this is not enough for the 17kW grid-tie array.
Maybe if you connect only about 15kW from it in the Deye AC Smart port ... and the rest in the AC_in port (this 2kW will not work in a blackout)

 
Seems to me handling of AC coupled PV would be limited to what it can charge from AC line.
It says 190A charging, which at 48V would be 9120W
Inverter is good for 8000W. Operating bidirectional, might be able to pull down 8000W from AC to HV DC bus.

17,800W (STC) of panels minus 10,400 limit DC coupled on PV input leaves 7,400W of PV to AC couple.

Sample menu page 41 shows example 8000W limit on generator port and AC couple on load side as a use of generator port.
From later block diagrams, appears either microinverters can be connected or loads for "smart load" control; a relay-controlled connection.

"Micro Inv Input: To use the Generator input port as a micro-inverter on grid inverter input (AC coupled), this feature will also work with "Grid-Tied" inverters. *Micro Inv Input OFF: when the ba�ery SOC exceeds se�ng value, Microinveter or grid-�ed inverter will shut down. *Micro Inv Input ON: when the ba�ery SOC is lower than se�ng value, Microinveter or grid-�ed inverter will start to work."


So it does look like you can connect microinverters (or string inverters) to the generator port.
But I don't think this will boost peak battery charging rate.
I don't think it will boost peak AC power available to loads, because the current has to pass through Deye from generator port to load port.
It should allow up to 8kW from GT PV inverters to feed load while up to 9kW from DC coupled PV charges battery.

Possibly, GT PV on "Load" rather than on "Generator" port would support higher peak AC power. That is the normal way AC coupling works. Usually AC coupled watts is limited to battery inverter watts as MrZed says, because battery has to suck down the excess power sometimes. My SMA inverters spec AC coupled can be 2x battery inverter, but I don't think they could handle a "load dump" where AC loads go from 100% of that power to zero instantly.

But for these high-frequency battery inverters that do support AC coupling, members have said they have difficulty instantly reversing direction of power flow, and for this reason GT PV is instead connected to the generator port, where relay can be opened to disconnect them immediately.
 
Maximum GT inverter AC coupling input to generator port is determined by the 50A current rating of the pass-through connect relay.
 
It is a rule of thumb to have more kW battery inverter than grid-tie inverter. (grid-tie : battery_inverter ratio should be less than 1:1)
I think battery capacity is a more important factor to allow the hybrid grid forming inverter to have a buffer in order to absorb the GT output until the algorithm in the hybrid can turn down or turn off the GT inverter. My Outback Skybox can AC couple up to 7.2kW or GT AC coupled output but it only has a 5kW inverter. I think it depends on each manufacturer, their hardware and firmware that determines the ratio. The above rule of thumb should never be relied on without confirming the exact ratio of each inverter one is considering.
 
Maximum GT inverter AC coupling input to generator port is determined by the 50A current rating of the pass-through connect relay.
That works while the grid is up because the grid is the buffer. That would be 12kW of GT grid dependent AC coupled capacity for the Deye to manage when the grid is down and I have not seen many hybrids that can do that much. However the SolArk 15k can do 19.2 of AC coupling so anything is possible .
 
And so it likely depends on the largest AC load that might get shut off at one time. That's how much battery inverter has to suck down (for a few seconds).
 
And so it likely depends on the largest AC load that might get shut off at one time. That's how much battery inverter has to suck down (for a few seconds).
Yes that is just one of the variables that the system designers have to deal with. And of course that is completely out of their control but presumably they have to test for that scenerio.
Here is a back of the knapkin guess about what that load might look like in my setup. My inverter is 5kW and my AC coupled AC capacity is 7.2 kW. So it is possible for my system. when off grid, to serve 12.2 kW of loads. The only loads big enough to create that current might be my 30 Amp (9.6kW) EV charger and my oven that is on at 50 Amp {12kW) breaker. If the grid goes down I will probably not be charging my car at that current and will be sure to tell my wife to not do any baking, especially in both ovens.
 
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It is a rule of thumb to have more kW battery inverter than grid-tie inverter. (grid-tie : battery_inverter ratio should be less than 1:1)

You can use the new big 16kW Deye/Sunsync unit ... but even this is not enough for the 17kW grid-tie array.
Maybe if you connect only about 15kW from it in the Deye AC Smart port ... and the rest in the AC_in port (this 2kW will not work in a blackout)

they now have a 50kw version too..
posted a intro movie about it a while back
 
I think battery capacity is a more important factor to allow the hybrid grid forming inverter to have a buffer in order to absorb the GT output until the algorithm in the hybrid can turn down or turn off the GT inverter. My Outback Skybox can AC couple up to 7.2kW or GT AC coupled output but it only has a 5kW inverter. I think it depends on each manufacturer, their hardware and firmware that determines the ratio. The above rule of thumb should never be relied on without confirming the exact ratio of each inverter one is considering.
I think you are right and both parameter is important.

It needs to be able to store excess power.
So the inverter/rectifier is the first limit.
If you put 10kW grid-tie behind it ... you need to be able to store what it is generating.
Yes in 0,2sec it can stop the grid-tie with high Hz sine wave ... but a sudden drop of load can be too much for it (like full load and main breaker pops).
The 1:1 rule is from Victron. And I think it is even better to go under it.

And to store this power, it needs a big battery charger. As big as the inverter.

Also you need enough space in your battery to store it. This is why over 90-95% SoC it raises Hz to shut down grid-tie inverters.
 
If grid drops and GT power too much for inverter to absorb the Sol-Ark immediately opens generator relay to dump GT inverter. It also has option for additional load dump.

Deye and Sol-Ark has a lot more HV DC capacitor storage. I know the 8k models have fourteen 1000 uF HV DC caps. That is about 14x more than the normal Chinese HF inverters like MP solar, etc. Still not a large amount to absorb a large overload but enough to give it some time to take protective action.
 
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