Deye GEN input - microinverter / on-grid inverter

zolee

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Hello,

Anyone connected microinverter/on-grid inverter to the GEN port of DEYE inverter?
I'm currently installing 4.6 kW panels and a new 3 phase 8kW DEYE, but in the future I'd like to add a second array, but it's location is far from the DEYE planned place. I'm thinking about AC coupling the second array to shorten the DC cabling as much as possible. Will it work, and will it work in parallel with the main PV array?

Edit: I'm not exporting to the grid. Only Export to CT.

The manual for DEYE SUN-8K-SG04LP3-EU on page 35 says:
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 battery SOC exceeds seting value, Microinveter or grid-tied inverter will shut down.
*Micro Inv Input ON: when the battery SOC is lower than seting value, Microinveter or grid-tied inverter will start to
work.
AC Couple Fre High: If choosing“Micro Inv input”, as the battery SOC reaches gradually seting value (OFF), During the
process, the microinverter output power will decrease linear. When the battery SOC equals to the seting value (OFF),
the system frequency will become the seting value (AC couple Fre high) and the Microinverter will stop working.
MI export to grid cutsoff: Stop exporting power produced by the microinverter to the grid

Screenshot_20220314_093125.png

The basic application draving also shows the use of on-grid inverter on GEN port:
Screenshot_20220314_092756.png
 

zolee

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Thanks, that was somewhat helpful.
There are more videos on his channel explaining it, but I couldn't find one where he talks about power regulation and export limiting of the microgrid connection.
 

Hedges

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I'm currently installing 4.6 kW panels and a new 3 phase 8kW DEYE, but in the future I'd like to add a second array, but it's location is far from the DEYE planned place. I'm thinking about AC coupling the second array to shorten the DC cabling as much as possible.

I think long high-voltage PV DC run is preferable to long AC run.
Power loss at same voltage/current would be same. The benefit is MPPT DC input can operate over a wide voltage range, while AC has a limited range before it disconnects.

Not suitable for microinverters, because they run at lower single panel DC voltage, and would require a pair of wires per microinverter. A string inverter is typically 600Voc max, can be operated around 480Voc and 380 Vmp nominal, so smaller wire gauge and/or less power loss than for AC wire run.
 

houseofancients

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Thanks, that was somewhat helpful.
There are more videos on his channel explaining it, but I couldn't find one where he talks about power regulation and export limiting of the microgrid connection.
export limiting is a global inverter setting.
sunsynks ( deye/sol-ark) use frequency shifting to enable or disable the microinverters, but otherwise they are considered a powersource just like the batteries or dc solar panels
 

RCinFLA

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With a high frequency hybrid inverter, I would not use AC coupling from GT inverters directly to inverter AC output. Too much risk of damaging HF hybrid inverter.

Use the generator input port for AC coupling GT inverter input. It gives the HF hybrid inverter the ability to open the generator connect relay to immediately dump the GT inverters if it gets into trouble with too much back-feed surge current.

The worst-case situation is when grid is down and operating on batteries and GT inverters. If you have a lot of PV GT inverter's production, mostly consumed by house AC loads, then someone turns off a heavy house load leaving a large amount of PV overproduction back feed surge into AC coupled hybrid inverter. Freq shifting control cannot react fast enough to handle this situation.
 

houseofancients

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this is one of the specific roles of the smart load (aux) port on the deye/sol-ark/sunsynk.
you can either set it to smart load, or smart input
 

zolee

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In this video he explains more in depth about using the on-grid inverter on AUX port. Now it doesn't look that good like before. The main issue in on-grid setup is that the AUX is on a common busbar with the GRID, so when grid is present the inverter can't control the frequency.

I think long high-voltage PV DC run is preferable to long AC run.
Power loss at same voltage/current would be same. The benefit is MPPT DC input can operate over a wide voltage range, while AC has a limited range before it disconnects.
I prefer not having high voltage DC cables in my garden. But if I want to keep the grid connection I'm forced to DC, or accept the rough on/off relay control. I'm better to find a way to lay the DC cables safely.
The voltages are not the same, with DC it would be 500-600V, with AC it's only 230/380V which is easier/cheaper to control and protect. If I try to lower the DC voltages I'd ramp up the current into the non acceptable ranges (20-25A).
export limiting is a global inverter setting.
Yes, but in the case of on-grid mode it will just switch on/of the relay, it can't do fine control of the output of the "slave" on-grid inverter.
this is one of the specific roles of the smart load (aux) port on the deye/sol-ark/sunsynk.
Now I understand how it works.
With a high frequency hybrid inverter, I would not use AC coupling from GT inverters directly to inverter AC output. Too much risk of damaging HF hybrid inverter.
I wasn't planning to connect parallel with grid. My plan was using the AUX/GEN/MI input/output.
The worst-case situation is when grid is down and operating on batteries and GT inverters.If you have a lot of PV GT inverter's production, mostly consumed by house AC loads, then someone turns off a heavy house load leaving a large amount of PV overproduction back feed surge into AC coupled hybrid inverter. Freq shifting control cannot react fast enough to handle this situation.
At first the GT option looked like a no brainer. But as I think about it and read you opinions more and more it looks like the worst option in case of zero export. Either need to keep a heavy load active all the time and control it in some way (I have a water heater that is controlled by a PLC) or accept the on/off control by the inverter.
 

RCinFLA

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High frequency two stage inverters are more complicated to control, and delicate compared to low freq hybrid inverters. Making a true bi-directional high freq DC to high voltage DC converter is not easy. Most of the Chinese HF hybrid inverter versions don't even try. They put a parallel buck circuit to charge battery, and many do not allow AC coupling.

Low frequency hybrid inverters are PWM'g at the battery side MOSFET's. They are inherently bi-directional and can take reverse power flow on-the-fly. Their low freq heavy silicon-iron transformer can also take overload surge current much better than HF ferrite transformers. Ferrite transformers have a fairly abrupt saturation point. MOSFET's current shoots up to destructive levels when ferrite transformer core saturates due to overload.

Without a fast-reacting load dump, you are relying on battery to take back feed surge. Most hybrid inverters that allow AC coupling prevent full charging of battery when AC coupling is enabled to keep some reserve ability of batteries to take a back surge without battery voltage rising above inverter high batt voltage shutdown. You have to be sure battery AH and batt cable sizing is large enough to take the back surge without inverter DC input voltage rising too much during back flow push. Common mistake made is thinking you don't need much battery capacity because you have so much PV power capability available.

Freq shift control on GT inverters can take a few seconds before their output is cut back so something has to take the overproduction for at least that period of time. This is fine for normal sun intensity slow variations but not for worse case sudden overproduction situation.
 
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