diy solar

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Going offline or grid black out, with pre-existing setup

brandnewb

brandnewb

Going for serious. starting as newb
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So my brother @Hedges has already, ages ago it seems, suggested the SMA sunny island units for when one wants to go offline.

I am amongst one of those that thought too late that going offline is a good idea.

SO now I have 11 x 3 phase APsystems micro inverters.

Sure our grid is reliable thus far. But I need to prep for when it's not.

So I am considering SMA.

But what are your thoughts?

SMA seems to have a bad rep when I look at the google reviews.
Also I am still waiting for days for my account to be created so that I can access their technical resources.

If it can work I would like to work with these Germans. I already know and love their bradwurst and women.
 
What bad do people say about SMA?

I haven't been using any members-only technical resources (FAQ or forums?) at SMA; maybe I should look.
I've submitted a handful of support inquiries.

Do the APsystems microinverters support "frequency-watts" or what we over here call "UL-1741-SA" or "Rule 21"?
That is where output wattage ramps down as frequency is shifted up by the grid (or by Sunny Island).
That is what's needed to behave nicely in a backup or offline system.

Still doesn't guarantee good operation; many people do the same with SolArk as the grid-forming inverter, but the latest Enphase IQ8 microinverters cause problems. Possibly due to aggressive anti-islanding tests.


Checking the "SMA Self Help & Knowledge" section, I thought it would help with export limit, but not very useful!!

"Configuring Active Power Limitation

In this article you will find out how to configure the limitation of the active power feed-in according to the parameters.
Apr 26, 2023•Knowledge​

Configuring Active Power Limitation
Configuring-Active-Power-Limitation
In this article you will find out how to configure the limitation of the active power feed-in according to the parameters.

Description
For the configuration of the active power limitation, please contact your installer.

Disclaimer
<etc.>"
 
What is the model/part number of the micros? The QT2 model is compliant but I don’t know what you have.

QT2
“CA Rule 21 (UL 1741 SB) compliant”

Sunny islands have only a few negatives. 1. Cost per kw. 2. Only a single AC input.

The only reason I would ever use SI’s in an AC coupling setup, is if the owner already had SB’s PV inverters. The real advantage of SI’s is when ac coupled using SB’s, it allows a 2:1 AC coupling to SI inverter ratio due to the SMA communication integration. Typically mixed manufacturer AC coupling has a 1:1 ratio limitation.

Due to being 3 phase and already owning non-SMA PV inverters, there is 0 technical benefit to using SI’s. I know you want them, but will be buying SI’s in groups of 3 due to having a 3 phase service. There are 3 phase battery inverter or AIO options with better pricing and more kw output for the money. The SI’s are a LF inverter that would be excellent in a unbalanced 3 phase application. If the 3 phase loads are somewhat balanced, a HF inverter would suffice. If starting motors larger than normal home appliances, the SI would be my choice.

SMA is hands down a great company for after market support/service. You can never go wrong with them, it just cost more.
 
Last edited:
eleceng1979 said:
What is the model/part number of the micros? The QT2 model is compliant but I don’t know what you have.

QT2
“CA Rule 21 (UL 1741 SB) compliant”

Sunny islands have only a few negatives. 1. Cost per kw. 2. Only a single AC input.

The only reason I would ever use SI’s in an AC coupling setup, is if the owner already had SB’s PV inverters. The real advantage of SI’s is when ac coupled using SB’s, it allows a 2:1 AC coupling to SI inverter ratio due to the SMA communication integration. Typically mixed manufacturer AC coupling has a 1:1 ratio limitation.

Due to being 3 phase and already owning non-SMA PV inverters, there is 0 technical benefit to using SI’s. I know you want them, but will be buying SI’s in groups of 3 due to having a 3 phase service. There are 3 phase battery inverter or AIO options with better pricing and more kw output for the money. The SI’s are a LF inverter that would be excellent in a unbalanced 3 phase application. If the 3 phase loads are somewhat balanced, a HF inverter would suffice. If starting motors larger than normal home appliances, the SI would be my choice.

SMA is hands down a great company for after market support/service. You can never go wrong with them, it just cost more.
Click to expand...
Ok thanks for pitching in. I will not be blinded by what google reviews have to say then. I will let their customer service make up my mind.

Which is fair I think,
 
Hedges said:
Do the APsystems microinverters support "frequency-watts" or what we over here call "UL-1741-SA" or "Rule 21"?
That is where output wattage ramps down as frequency is shifted up by the grid (or by Sunny Island).
That is what's needed to behave nicely in a backup or offline system.
Click to expand...
wow, I have absolutely no idea.

My thinking is that a "self grid" "island" " should be aboe to deal with what ever AC comes in. either3, split or single phase.
 
brandnewb said:

OUCH!! Hardcore dissatisfaction.

I will say though that I have gotten my account created in the meantime. So not I am enabled just to see how good their (technical) support is.
Click to expand...

The reviews for Belgium looked really bad.
Here in the US, I find response extremely slow but resolution has been OK in the end.
They have repaired a Sunny Boy for me under warranty, replacing PCB with blown trace.
Another guy who bought Sunny Island that came from DC Solar bankruptcy, they replaced entire inverter (seems no longer trying to repair.)
I got a replacement SpeedWire interface for TriPower that I had bought through eBay.

I've seen high reliability from SMA hardware. The two Sunny Boy failures I had, out of 5 over many years, calculated out to 32 years MTBF. All the rest of SB I have, zero failures but not enough operating time to be significant. The interface card might have been DOA but highly unlikely because configured and operating before; I did accidentally connect a Sunny Boy with 400VDC reverse polarity to TriPower (instead of connecting PV string), which blew a fuse into reverse polarity clamping diode but maybe made a transient.

I mostly don't rely on support, just RTFM, plug the equipment in and configure (I got installer's grid-guard code, also Personal Unlocking Key for each inverter that uses SpeedWire.)

Other brands, people keep talking about firmware updates to get them to work for various features. Mine use the firmware which was already there just out of the box. They do offer updates, only installed once looking for "Rule 21" in TriPower (feature apparently already there, not with that name.)

brandnewb said:
wow, I have absolutely no idea.
Click to expand...

Find out, the ramp down of watts as frequency increases is key to a nice AC coupled system.

brandnewb said:
My thinking is that a "self grid" "island" " should be aboe to deal with what ever AC comes in. either3, split or single phase.
Click to expand...

There will be a neutral and 1, 2, or 3 hot lines. The inverter(s) have to provide that many connections.

Often, single-phase GT PV inverters with 2 wires can go across any one phase for any of those three types, are configured to recognize either by jumpers or by voltage & phase angle when 3rd wire for Neutral is connected.

Battery inverters that I've seen are set up for just one of those. Often stackable, so a 120V model can work in group of two or three for 120/240V split-phase or 120/208Y 3-phase. For you, 230V single phase could do 230/400Y 3-phase. And then some are split-phase or 3-phase in one box.
 
eleceng1979 said:
What is the model/part number of the micros?
Click to expand...
thanks for pitching in. I do not have those details at hand. they are on my roof.

I will say though that although I have gotten accepted an account at SMA and I was able to create an 'issue' with ticket number and all.


I still hear nothing.

also It should not matter what current system I have. at least that is what I think. Just hook up any and all dc to ac 3 phase inverter should work in my books.

But if I am mistaken then please push a bit harder on me and then I will go get those details by climbing on the roof.
 
Hedges said:
Find out, the ramp down of watts as frequency increases is key to a nice AC coupled system.
Click to expand...
why would that be the important bit here?

The important bit would be for the system that I intend to introduce to take over from the grid.

The focus should not be the current system and it's specifics.

The focus should be the intend system and it's ability to take over.

Please forgive me if I am missing some important stuff. I am hanging in here
 
An off-grid or backup system ideally harvests from PV exactly the amount of power needed for loads plus battery charging. Charge current tapers off to maintain desired absorption or float voltage, or to allow BMS to balance.

That comes automatically with DC coupled; SCC regulates voltage.

With AC coupled (GT PV inverter delivering power to AC wires, battery inverter forming island grid and charging batteries from island grid), the GT PV inverter knows nothing about battery voltage or power consumption. It just delivers 100% of available power as AC, whether the grid wants it or not. Frequency-shift power control is battery inverter gradually ramping frequency above 60 Hz, and GT PV inverter ramping power down in response. Frequency hovers between 61 Hz and 62 Hz for my older equipment. Between 60.5 Hz and 61 Hz for UL-1741-SA Rule 21 equipment (which includes many brands other than SMA.)

If you don't have frequency-watts working, then GT PV delivers 100% of available power and battery makes a run to 100% SoC and beyond. If BMS doesn't disconnect first, battery inverter ramps up frequency trying to do frequency-watts and knocks GT PV offline. Battery then runs down. The cycle repeats.

If you buy an all-in-one hybrid, it won't work this way (unless also AC coupled to existing GT PV inverters.)
If you want to buy a battery inverter to convert your grid-tie system to backup, this is a brand-agnostic way to do it.
Some brands (e.g. Enphase) have other proprietary communication to make it work. IQ8, I think may only work well within their own ecosystem. IQ7 many people have successfully AC coupled with other brand battery inverters.
 
Ok, I will admit defeat.

I am not smart enough to wrap my head around this within 4 hours of brain focus.

ShallI just go ahead anyway? with 3 x SMA SI? even though I have not gotten an official response that my scenario is supported?
 
No. Not until you determine how your existing GT PV will behave with a grid-forming battery inverter. Or if you will connect PV panels to something else.

You may want to go with a hybrid, especially if you rewire PV panels to it.

If your GT PV does do frequency-watts, and if it works well enough with grid-forming inverter, then 3x SI could be nice. But some GT PV inverters do anti-islanding so aggressively that it doesn't work (people using Enphase IQ8 with SolArk, for instance.)
 
My employer tried to fly me to Taiwan. To visit a customer fab where I wouldn't be allowed to touch anything anyway.

First time, I got out of it by catching Covid. Second time, by electrocuting myself. I'm running out of creative ideas (any suggestions?)

I work best with familiar lab and materials around me.
You just need to figure out what your equipment can do. If your microinverters function on-grid without support equipment, and if they can work at 60 Hz 120/208Y (or higher voltages that I might make with 3-phase transformers), you could ship me one and I'll try AC coupling it.

In Europe, 3x Sunny Island will cost $15k. In the US, we can get them for half that due to liquidation sales. Something else could be more economical for you unless you need all the watts.
 
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