calisparky6
Member
but how does the back feed work? cause technically the bus is being fed by the utility and the pv system. right?
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Pwer from PV systems go to the grid?
- Thread starter jjhoward
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ty
Senior Member
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- 3rd Rock from the Sun
but how does the back feed work? cause technically the bus is being fed by the utility and the pv system. right?
The inverter is the 'brains' of the system. These inverters are simply amazing in what they do.
The bus is being fed by both. That's why the bus size is important, and calculations have to be done.
Open Neutral
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It gets complex....I'm learning the hard way how much so.
First, grid-tie inverters are basically current sources. They push their rated out current back into the grid, relying it seems, on the very low input impedance of the grid to consume such. An elaborate system turns off everything if the grid fails. This helps keep the utility linemen alive as they respond to downed wires.
By law, the utility has to pay you that power. Whether that is a good deal for the homeowner is debatable; look at the payback interval for those PV arrays.
Clearly it gets much more ...interesting... when the grid tie output gets to be a non-trivial percentage of the total load.
Standby inverters have a different world to deal with. The impedance of their load [your house] varies widely; so they are voltage sources.
Further, they seem to work on 48V PV arrays, not the 150V+ the grid-tie ones want.
Some manufacturers say they do both in one box. I don't yet know how.
First, grid-tie inverters are basically current sources. They push their rated out current back into the grid, relying it seems, on the very low input impedance of the grid to consume such. An elaborate system turns off everything if the grid fails. This helps keep the utility linemen alive as they respond to downed wires.
By law, the utility has to pay you that power. Whether that is a good deal for the homeowner is debatable; look at the payback interval for those PV arrays.
Clearly it gets much more ...interesting... when the grid tie output gets to be a non-trivial percentage of the total load.
Standby inverters have a different world to deal with. The impedance of their load [your house] varies widely; so they are voltage sources.
Further, they seem to work on 48V PV arrays, not the 150V+ the grid-tie ones want.
Some manufacturers say they do both in one box. I don't yet know how.
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