[RE-wrenches] Will IQ8 microinverters backfeed a generator during grid interruptions

[Zeke Yewdall]

One way to find out... put a big load on the generator (so you don't
actually backfeed it) then turn on the PV array and see if it'll
synchronize with the generator.  My understanding is that most generators
under 100kW are not good enough power quality to trick a grid-tie inverter
to thinking they are the grid, and the grid tie inverter will not turn on.
Still.... we put isolation relays on systems with generators to keep the PV
array from ever seeing generator power, or wire the PV array in upstream of
the generator transfer switch.

I did hear of SMA taking all of the safeties off the software for a string
inverter, and it would backfeed a small generator just fine.  It's the
UL1741 safeties, not the electronics of the grid inverter that prevent it.
They said the generator made the worse noises they'd ever heard when it was
trying to sink 5kW of power instead of sourcing it.  Probably would have
self destructed after more than a few seconds.

A lot of small diesel mini-grid systems on islands and up in Alaska do
interface grid-tied inverters with diesel generators, in the 50kW to 1MW
range.  But they usually have special addiitional controls to allow this
and prevent backfeeding the generator. And they have to open up the UL1741
grid window to allow the grid tie inverters to connect.  This was all
before zero sell was a common thing though, so I wonder if a zero sell
grid-tie inverter could do it with just the grid window opened up.   This
would only work if you were off grid... probably could be be modifying the
grid window if you still had grid sometimes.

Zeke
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