Building off grid system to fool enphase inverters without grid connection.

[Hedges]

If your battery inverter does frequency-shift, and if the microinverters have UL-1741-SA frequency-watts, I think that does what you want.

If you have some inverters online that don't do frequency-watts, just switch off/on line, I think some loading conditions will cause cycling, while some other load conditions could operate smoothly. Depending on whether the frequency-watts ones can carry the load (or load exceeds all production.)

 

[Ampster]

My M215s currently have the factory default grid profiles (I believe it is IEEE1547).

What grid profile would I use to replace that - and would the M215-IQ7s modulate/buffer as previously described?
Would switching them out incrementally have any detrimental effect?

My understanding is that the older M215 micros are UL1741 compliant. I believe UL1741SA includes the modulation referred to above. I also believe that is the same as CA Rule 21. I am not familiar with 1747? EDIT: I researched 1747 and it does relate to some inverter interactions but the key standards for AC coupling seem to be the 1741 specs. Since the topic of this post is fundamentally AC coupling, that would be the operative spec to pay attention to.
I also don't know what mixing 1741SA and 1741 inverters would do except perhaps dampen the fluctuations of the old M215's as the turn off and on. It's really only an issue when the grid is down.

 

[Hedges]

I believe UL-1741-SA includes a ride-through for 299 seconds during minor frequency and voltage excursions.
I think frequency-watts is an option that inverters might or might not implement, and has to be enabled.

Here's a guy with IQ-7 doing frequency-watts

Adding storage to my Enphase system

Are they splitting the load evenly? Nope! Load shifts from #1 to #2 every 2 or 3 seconds. I suspect this is occuring because I have not performed the "AC Output Voltage Configuration and Calibration" procedure. I tried to, but I do not have many computers running windoze, which is required to...

diysolarforum.com

 

[Ampster]

I believe UL-1741-SA includes a ride-through for 299 seconds during minor frequency and voltage excursions.
I think frequency-watts is an option that inverters might or might not implement, and has to be enabled.

Presumably "ride through" is to protect the grid from sudden shutdowns and probably not important to an off grid situation which is the subject of this thread. I guess the need for a battery to facilitate that " ride through" requirement is one of the factors in designing an AC coupled system?
I don't remember the sequence that Outback implemented AC coupling and notified me that they were UL1741SA compliant. The former would involve functionality and the actual certification could have come at a later date. I never had to "implement" frequency-Watt on either my Skybox or my IQ7s when I configured either of them for my AC coupled system .
It is clear to me that to have functional AC coupling an inverter manufacturer would want to implement frequency- Watt response because that is the only way a grid forming hybrid could control GT inverters.

 

[GVSolar]

Thanks.

I'll read up on your references and continue my research... perhaps I will buy one of the aforementioned kits and replace one of the M215s under test conditions.

Maybe even send a note to Enphase, now that I've successfully registered the Envoy with them. Their installer web page keeps telling me there's an error - even though all the micros are showing operational and producing power - their toolkit says "no communication with utility meter" (duh). It doesn't seem to be hip to the fact that I'm off-grid. And no way to configure a system as off-grid - at least that I can find.

I guess they want me to hook up to PG&E and buy an Encharge instead.

Best.

 

[GVSolar]

I found this - it gives a pretty good explanation of those various grid profiles:

http://media3.ev-tv.me/UL-1741-Supplement-A_Webinar.pdf

 

[Hedges]

"What does UL 1741 SA test?
Mandatory
• Anti-Islanding
• Low/High Voltage Ride Through
• Low/High Frequency Ride Through
• Ramp Rate
• Specified Power Factor
• Volt/Var mode
Optional (Depends on SRD)
• Frequency Watt
• Volt Watt"

So "frequency-watts" is optional. Later slides show what this function means.

 

[Roadstermac]

https://enphase.com/sites/default/files/M215_Installation_Manual_NA.pdf

"The Enphase Microinverter has field-adjustable voltage and frequency trip points that may need to be set, depending upon local requirements. Only an authorized installer with the permission and following requirements of the local electrical authorities should make adjustments."

https://documents.wholesalesolar.com/media/enphase-m250-with-mc4-micro-inverter-manual-1733006541.pdf

https://enphase.com/sites/default/files/M215_DS_EN_60Hz.pdf

What I haven't found is how to adjust the trip points. Maybe a password and one of their communication devices. I also don't know if time to reconnect is adjustable.

For strictly off-grid use, adjusting the frequency limit of each one slightly differently would give you gradual throttling of power. If reconnect time was changed to be short, this should give nice interaction with a battery inverter.

Hi. Sorry. Do you know hoo to connect any kind of IQ7s with an isolated Growatt?

 

[Hedges]

Does the Growatt support AC coupling by shifting frequency?
Several brands of battery inverter have that feature, but I don't know about Growatt.

IQ7 has profiles where its wattage output is reduced as frequency is increased. I think the company limits which profiles can be installed in any given location (for local regulations.)

 

[Ampster]

Does the Growatt support AC coupling by shifting frequency?

Yes, that is the important question along with any manufacturers recomendations about the relationship between AC coupling capacity, battery capacity and DC coupled capacity. AC coupling is not simple and each inverter manufacturer has a different algorithm that affects the above parameters.