Emergency AC Coupling a grid tie system?

[Bivitar]

Experts,

I currently have a 11.7 kWh grid tie system using Enphase IQ7+ Microinverters with no battery backup. I'm in Florida and the power cost is only $0.115/kWh so adding batteries is more for a post storm event when the grid is down for 3-8 days than a continuous use case.

I saw the Ecoflow Delta solar generator (link: https://ecoflow.com/collections/portable-power/delta) and I was looking at getting a couple to run a few items when the power is out.

But then I was thinking could these be used as AC batteries simply plugging the output into an outlet (would need a dual male ended cord) and plugging the Delta AC charge cable into another outlet (assuming on another breaker line)?

Of course cutting of the main breaker before doing this is a must!

My question for the experts is, would this work? Once the Deltas (assume 4) are charged and the sun is up will the IQ7+s throttle the solar panel power?

Thanks for any input!

 

[Picasso]

Just keep waiting you can upgrade your enphase to "black start" in 3-5 months. see also https://diysolarforum.com/threads/solar-newbie-checking-in-with-my-11-5kw-solar-panel-system.1573/

 

[Bivitar]

Thanks, I've been tracking the Enphase Ensemble system and that's on the upgrade list. Luckily this year we didn't get hit too hard during hurricane season.

I'd still like continue the discussion on the above, I saw Will was asking a similar question on another post. What I can find up to this point is it looks like it will work to trigger the micros but the technical question is what do the micros and the envoy do when the Deltas are full and production is greater than consumption?

 

[Picasso]

Without feedback on consummation (and thus controlling output) the iq7 will shut down when the frequency starts to rise, wait 5 mins and try and restart. you can find older videos with the enphase m175 units first came out years ago of people playing with them with honda eu2000 generators

 

[Bivitar]

the system has the Envoy with consumption CTs installed.

 

[newbostonconst]

I am in the process of using a Outback Radian GS4048 inverter to do my AC couple backup. The GS4048 it is supposed to frequency shift to throttle back my IQ7's. It was the cheapest legit method I could fine. The Radian is a 48 volt charger, will run a critical loads panel for backup, 4k inverter, upgradeable, and can start a generator to charge the batteries. Fits everything I want. I didn't buy the extra breaker panel because I think it can be done myself for under $100.

Not buying in on the Enphase system yet. They advertise it to be simple but then you see all the connections and it is just like the others.

 

[L-P-G]

You cannot AC couple a GT system to a generator. By design GT inverters will output 100% of the sun they receive (with some caveats more on this below). This means that if your micros sync to the generator (I say if because they require a clean sinewave that only inverter generators can produce) they'll start to pump out as much power as possible, in a system with batteries this power would flow backwards through the battery based inverter and recharge your batteries, when the batteries are full the battery based inverter will shutdown the solar production either by curtailing using frequency shift or via a contactor on the solar circuit. In a system without batteries all that power has to go somewhere, that somewhere is your loads and your generator.
If you have enough loads to use 100% of the power being produced ALL the time then you'd be fine, but most people don't so the power ends up backfeeding into your generator which will either break it or turn it into an electric motor.

IQ8s get around the extra power issue by using CT clamps on your home circuit to detect how much power to produce and curtail accordingly, but they still need the ensemble battery and gateway to island your house from the grid (since the grid is down you don't want to electrocute a lineman who thinks the cables are dead) and the battery is used to provide the jump start power needed to power on the Envoy and generate a sinewave for the micros to sync to.

 

[newbostonconst]

So the sequence is: run on grid....power goes out....run on battery....sun comes...up run on solar to charge batteries...batteries full....GS4048 frequency shifts to slow down solar production....night comes....run on battery....battery dies....start up gen...sun comes up....(this is were you see the problem) gen is running with solar.

To get around this use a current really in series with gen command to shut off gen when solar production gets over 1kw. Also my gen is a 50kw diesel old style huge generator head with no electronics so you can back feed it all you want. Smaller generators no.

Your other comment is back feeding the grid. The GS4048 does have 2 relays that feed the critical loads panel but Outback states that both relays can't be on at the same time.

Thanks LGP for your great comments and let me know if I am wrong....Have a good day.

 

[Bivitar]

A couple of things have gotten off my original questions.

- No gas generator is involved
- Auto fail over from grid to AC couple is not part of configuration.

Sequence would be:

- Big storm (Tropical Storm, Hurricane) rolls in
- Grid goes down
- Emergency power critical items off Ecoflow Delta battery generator(s)
- Storm over
- Grid looks like it will be down X days
- Turn main breaker off/ Manual Grid Disconnect switch
- Plug Delta output into house outlet to energize microinverters
- Plug Delta Input into outlet on different breaker
- Micros start pushing power

Sounds like everything would work until there is more power coming off panels than the house load + battery charging needs and that's the crux of my question on what happens inside the Envoy and/or the IQ7+ micros and if they self regulate or what happens.

The Deltas are a self contained 1.3 kWh battery, BMS, and 1800W inverter. Its doubtful they will frequency shift output based on battery charge state.

Hope that helps refine the question. I appreciate the other info. It looks like others are trying to find a cost-effective solution for a short term grid outage.

 

[Picasso]

My comment with the video/generators was to get you to research some of the other videos like it to see how enphase inverters respond when you black start them with you own inverter or generator. Yes you can black start with your inverter. What will happen who knows but most liky the enphases will go to a 3 stage output attempting to lower the frequancy, next the enphases will go to sleep if it cant control it. You also might get lucky and find that your inverter eats that extra power and charges you batt. You could find your batt attempting to charge at the rated power of your inverter....playing with power is something that can lower your life expectancy when taking advice that I spew, use caution.

 

[Bivitar]

Update: I was (finally) able to get through to a knowledgeable rep at Enphase...

TLDR: It won't work.

Details:

Micros won't turn on: Delta output is 120V 60Hz (US version) or 230V 50Hz (Int'l version). The IQ7 micros need 240V 60Hz input to sync.

AC Coupling is problematic: If the first issue wasn't a problem, without an input scheme to control micro production like frequency shifting or dump loads, if the production is greater than the load the system would be overloaded.

That all said, IF an inverter has the ability to AC frequency shift, then according to the enphase document, "Modern battery-based inverters have the ability to gradually change their frequency when operating in offgrid mode when the batteries are reaching a full charge. When this option is enabled on the grid-forming, battery-based inverter, you can set the IQ Microinverters to gradually decrease and increase power output accordingly. "

 

[svetz]

I'm a bit late to the party, but yeah... AC coupling has a bunch of caveats. There's a bit more on it in this thread: https://www.diysolarforum.com/threads/incrementally-adding-ac-batteries.588/

Enphase is also coming out with their "Ensemble" system later this year... it's a battery, ATS, and brain that allow you to have solar power when the grid is out. There's a few threads discussing that:

• Solar newbie checking in with my 11.5kw solar panel system
• Think it works?
• AC Coupling for off grid applications
• Grid tie with hybrid inverter and no batteries - possible?

 

[Bivitar]

Great info! I've been tracking Ensemble for awhile. It was the recent Ecoflow Delta Kickstarter that got me going down the proverbial rabbit hole.

Thanks for sharing.

 

[newbostonconst]

Update: I was (finally) able to get through to a knowledgeable rep at Enphase...

TLDR: It won't work.

Details:

Micros won't turn on: Delta output is 120V 60Hz (US version) or 230V 50Hz (Int'l version). The IQ7 micros need 240V 60Hz input to sync.

AC Coupling is problematic: If the first issue wasn't a problem, without an input scheme to control micro production like frequency shifting or dump loads, if the production is greater than the load the system would be overloaded.

That all said, IF an inverter has the ability to AC frequency shift, then according to the enphase document, "Modern battery-based inverters have the ability to gradually change their frequency when operating in offgrid mode when the batteries are reaching a full charge. When this option is enabled on the grid-forming, battery-based inverter, you can set the IQ Microinverters to gradually decrease and increase power output accordingly. "

So your other options are all expensive....Sol-ark, Schneider, Magnum, Tesla, OutBack.......

You problem is the AC frequency shift will only be done with the expensive stuff.

A gas backup generator seems like your cheapest option.

 

[L-P-G]

So the sequence is: run on grid....power goes out....run on battery....sun comes...up run on solar to charge batteries...batteries full....GS4048 frequency shifts to slow down solar production....night comes....run on battery....battery dies....start up gen...sun comes up....(this is were you see the problem) gen is running with solar.

To get around this use a current really in series with gen command to shut off gen when solar production gets over 1kw. Also my gen is a 50kw diesel old style huge generator head with no electronics so you can back feed it all you want. Smaller generators no.

Your other comment is back feeding the grid. The GS4048 does have 2 relays that feed the critical loads panel but Outback states that both relays can't be on at the same time.

Thanks LGP for your great comments and let me know if I am wrong....Have a good day.

Do you have the mate3 controller? I belive you can program one of the relays to be turned off while gen power is enabled. To said relay connect the coil of a large contactor, use the contactor to break the output line of your GT connection to your panel. This will prevent your GT system from running in parallel with your genny

A couple of things have gotten off my original questions.

- No gas generator is involved
- Auto fail over from grid to AC couple is not part of configuration.

Sequence would be:

- Big storm (Tropical Storm, Hurricane) rolls in
- Grid goes down
- Emergency power critical items off Ecoflow Delta battery generator(s)
- Storm over
- Grid looks like it will be down X days
- Turn main breaker off/ Manual Grid Disconnect switch
- Plug Delta output into house outlet to energize microinverters
- Plug Delta Input into outlet on different breaker
- Micros start pushing power

Sounds like everything would work until there is more power coming off panels than the house load + battery charging needs and that's the crux of my question on what happens inside the Envoy and/or the IQ7+ micros and if they self regulate or what happens.

The Deltas are a self contained 1.3 kWh battery, BMS, and 1800W inverter. Its doubtful they will frequency shift output based on battery charge state.

Hope that helps refine the question. I appreciate the other info. It looks like others are trying to find a cost-effective solution for a short term grid outage.

Small solar batteries like that invert using nothing but electronics, this means if you back feed them they will break. Inverters that can back feed have an h bridge and a transformer which makes them heavy and give them the ability to backfeed.

I know you already got an answer from enphase but there is one other option. The envoy has multiple grid profiles that can be contofigured and some of them are zero export profiles meaning they will only output as kucb power as being used. BUT those profiles still require a sine wave to start the micros and a small amount of power sometimes backfeed due to timing in controls so your small solar gen will definitely be damaged.

The last part that we haven't addressed, in the US power is 2 legs of 120v each at 180 degrees out of phase. This gives you 220v, the micros require both legs be active with a clean sinewave to operate, your solar gen would need to be able to output on both legs and no feeding the same 120v on both legs wouldn't work because they're not out of phase so they wouldn't add up to 220v

Moral of the story, get the proper inverter and what you want is definitely doable. With your current equipment it is not.

 

[newbostonconst]

L-P-G, yes I have a Mate3s....It is the only way to update to firmware to be able to do AC coupling with the GS4048. The GS units are shipped with firmware that doesn't do ac coupling.