- Jan 1, 1970
Home guy, try this wikipedia article for starters:
Here is an excerpt from that page:
"Inverters take DC power and invert it to AC power so it can be fed into
the electric utility company grid. The grid tie inverter must
synchronize its frequency with that of the grid (e.g. 50 or 60 Hz) using
a local oscillator and limit the voltage to no higher than the grid
Repeat: *no higher than the grid voltage!*
That's good for a first order approximation. The fact is that water doesn't
run down hill and electricity does *not* flow from low potential to high. The
inverter's instantaneous voltage *must* be higher than the grid for current to
flow into the grid.
Think about turning a bicycle crank, one without a clutch makes the point
better. You're not doing any work unless you're applying pressure to the
pedals. If you do nothing it drives you.
I realize wikipedia has its detractors, but it is peer reviewed and if
that statement were as blatantly inaccurate as you believe, it would
have been amended by now.
I'm going to put forth an analogy, and welcome feedback on it. It may or
may not be an accurate analogy, but this is the way I look at it: The
grid is a big freeway. Picture 6 lanes in one direction, with all the
cars moving along at 60 mph. The speed represents voltage. The number of
cars represents amps.
Now, you're going to add your little PV supply to it, so you cruise down
the onramp and merge into traffic. You match the speed (voltage) of 60.
But, you've added some current to the grid. Not a big percentage, but
some. You don't have to go 61 mph to get on the freeway, in fact, it
would be disruptive to do so.
No, you can't get on the "freeway" unless you're going faster than 60. If
you're going slower, they're actively pushing you off.
Y'all are welcome to take shots at this, I'm curious whether it seems
like a good analogy or not. But either way, I think the wikipedia
article is a good starting point for those that want to understand it
without an EE degree or reading Kirchoff as a bedtime story.
It's OK for a first order, but not for discussing the details people are
trying to get into here.