How does my breaker box handle micro-inverters/string?

[inowhavesolar]

Hello gang. I'm looking at buying a kit from GoGreenSolar, primarily because they offer permitting, blueprint design, code compliance, etc (ie: they do all the paperwork for the local city). Most of their kits are string-inverter based, or micro-inverter based.

My question is actually about basic electricity. Using either the string inverter, or micro-inverters, the wiring is the same in that both would backfeed into my main breaker box. What I don't understand is how do my lights/AC/fridge/etc pick the power coming from the inverter(s) over the power coming from the grid? If grid and inverters both dump to the main bus bars in the panel, how does "priority" work for all the breakers for the house?

 

[zanydroid]

There is no picking and it isn’t really necessary to think at this level of abstraction for loads. For parallel power sources, maybe. The microinverters and string inverters lock onto a voltage and frequency that is slightly above the grid (at their location in the branch circuit). This causes power to flow towards the bus bar and the grid.

From the busbar perspective, if there is more demand in the house than solar being produced then the grid acts as a source. If there is less demand then the grid acts as a sink.

Also from the busbar perspective, the grid tie inverters are designed to operate correctly in parallel with the grid and one another.

To put your question another way. There are many power plants on the grid. They are all paralleled with each other. How do your appliances pick which one to use?

 

[zanydroid]

That might have come off a bit dismissive.

There are indeed situations where digging in more makes sense.

I don't think the microinverters "literally" boost voltage to push more power into the grid, I think they do both voltage and phase shift (probably the most ELI5 usage of this "voltage goes up" thing is that you need to size the branch and feeder wiring for microinverters such that the voltage boost to cancel voltage drop is not so high that the microinverters fault out on invalid grid voltage)

The voltages, phase, net power, etc actually showing up at different power sources can be important if you are AC coupling power sources in unorthodox/naughty ways.

Some forum members use sensors detecting the power flow on specific feeders and branches to do automation.