On Wed, 12 Jun 2019 10:59:23 -0700 (PDT), trader_4
wrote:

On Wednesday, June 12, 2019 at 1:31:12 PM UTC-4, wrote:

I found this that explains a lot. We're on the right track of thinking
about what happens and that it's kind of a paradox as to how to detect
the loss of the "grid". They call this problem "islanding". This
talks about the ways they detect it, it's complicated and even includes
active action by inverters to deliberately try to destabilize the
grid so that it goes off kilter and all the other inverters can more
quickly detect it. It looks like they use voltage changes, freq changes
and power factor changes as possible parts of the algorithms and
that it's not a trivial problem. I think this gear is more for a larger
commercial array, but the same principles should apply to all inverters.


https://www.solectria.com/blog/anti-...-pv-inverters/

that is interesting

it is also what makes the frustrating situation for people that spent a lot of money for a solar system, and they still have no electricity when the grid is down, even when the sun is out.

m

Agree. When solar electric was first rolling out, I assumed that would be
a big advantage, that you could have power during the day with the grid
down. If someone could figure out a way to do that without batteries,
it would be a big selling advantage. The essence of the problem I guess
is that the sun varies and it would be difficult to maintain constant
power. Still, you'd think if it's say a 8KW system, couldn't they provide
2KW to whatever loads you wanted to have emergency power? If the sun
isn't sufficient, then it shuts down. If it gets sun sufficient for
3KW, then it turns back on. Software could impose off time delays
and lengthen the off times if starts cycling too much, etc. But I
guess a lot of people wouldn't pay much for that, having unpredictable
power that comes and goes and only during the day.

Probably the easiest way would be an inverter generator capable of
providing 120/240. It could just loaf along at idle when the sun was
shining and kick it up if a cloud came over or the sun went down.
You would still need transfer equipment tho.