Ampster
Renewable Energy Hobbyist
Perhaps that is the power line communications that many micros use.
EDIT: Subsequently clarified as Phase Locked Loop.
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How do you prevent back feeding the grid during outage?
- Thread starter donrichards
- Start date
EDIT: Subsequently clarified as Phase Locked Loop.
zanydroid
Solar Wizard
Phase locked loop
Traditionally it was a physical contactor/relay that isolates the utility input. I have not seen the contactor on some of the smaller all-in-one units, but it could be hidden. The logic of the contactor is that the inverter electronics will have some leakage which could still pose a threat to the utility.
zanydroid
Solar Wizard
The AIOs call it an internal transfer switch. I would imagine they are currently more reliable or something than an equivalent rating silicon switch. However they do click on and off at least once per day in some configs, so now I’m curious about their reliability/durability, and how serviceable they generally are. Preferably by the user since these things aren’t really convenient to cross ship for minor equipment swaps.
The equivalent contactor in EVSE only last like 5 years for entry level equipment. Granted the duty is much higher per day (though I guess if you have a really heavily loaded feeder on the critical loads panel it could be similar).
I don’t think a basic diode would work, as this is AC with all its complexities, and you have to allow “wrong” current to interact properly anyway with reactive loads unless they have a high level of PFC to buffer the grid from that responsibility.
The equivalent contactor in EVSE only last like 5 years for entry level equipment. Granted the duty is much higher per day (though I guess if you have a really heavily loaded feeder on the critical loads panel it could be similar).
I don’t think a basic diode would work, as this is AC with all its complexities, and you have to allow “wrong” current to interact properly anyway with reactive loads unless they have a high level of PFC to buffer the grid from that responsibility.
jasonhc73
Cat herder, and dog toy tosser.
There is always the "Off-Grid" setup using MPP Solar 6548s or EG4 6500s.
It may not be UL1749 but, it can't backfeed the grid anyway. They say they are UL1749, but it is moot. They can only pull power from the AC input. Then you run your load on the AC output side. You don't even need a net meter with these setups.
It may not be UL1749 but, it can't backfeed the grid anyway. They say they are UL1749, but it is moot. They can only pull power from the AC input. Then you run your load on the AC output side. You don't even need a net meter with these setups.
Ampster
Renewable Energy Hobbyist
I am sure it is not UL1749, which is not a standard related to Inverters. Perhaps you are thinking of UL1741 which is the interconnection section as well as UL1547
zanydroid
Solar Wizard
Yes this is actually something I’ve been wondering about… which hybrids have an easy to use air gapped off-grid mode, instead of using CTs. So you don’t get in (as much) trouble with interconnect agreements
Phase lock loop
OzSolar
Whatever you did, that's what you planned.
Numerous others have already mentioned that. I'm sure a few more will as well but it still won't change the fact that no one has bothered to explain what it is. LOL
Edit: The irony is that I'm likely not capable of understanding the explanation.
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timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
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- 18,769
Sounds like something my mother does when crocheting.
zanydroid
Solar Wizard
Basically something that synchronizes phase and frequency with an incoming signal. A grid tie inverter needs to generate output at the same frequency as grid, but with a controlled phase and voltage difference to push different amounts of apparent power back into the grid.
It's basically a circuit that converts frequency to voltage, and then that voltage back to frequency. It feeds that output frequency back to it's own input where the circuit then compares the two inputs and can isolate any difference. At this point the loop is locked. As the frequency at the main input changes, so then does the derived voltage in the middle. That voltage can then be used by the control circuitry to know when and by how much the frequency has changed.
Ampster
Renewable Energy Hobbyist
I may not be capable either. And in my estimation it has little to do with the title of this thread which is about how "you prevent" backfeeding the grid. That is, in my opinion, a very simple topic. Most of which is handled by standards which have been in existence for some time. "We" don't prevent backfeeding, it is either physical isolation or firmware/software which prevents backfeed.
jasonhc73
Cat herder, and dog toy tosser.
It does not have the capability to backfeed, so that's about as simple as it can be. You will still have to pay the basic grid connection fee though, you can't zero out that if you don't backfeed.
zanydroid
Solar Wizard
Are you talking about the off grid ones? Most should not be able to backfeed if they have the right power architecture. Very hard to confirm because there is no discipline on the part of those manufacturers to provide block diagrams of the internals.
But some off grid appear to be rebadged hybrids only allowed to backfeed overseas, which implies that the firmware or hardware still has the capability.
OzSolar
Whatever you did, that's what you planned.
No utilities that I know of will zero out the connection fee regardless of how many kWh you send back to them.
zanydroid
Solar Wizard
.
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OzSolar
Whatever you did, that's what you planned.
FFS please stop with the random posts that don't quote or reference anything specific. Quote what you are replying to or don't reply at all. You essentially render the entire thread useless when you do this. Anyone in the future trying to do research will not be able to make any sense of this thread.
Anyway... CCAs means what?
Anyway... CCAs means what?
