Electronic – How do solar inverter systems easily add AC power sources together?


I understand DC power more than AC power. I know that given multiple DC power generators, easiest way to sum them is by connecting them in series. In paralel you'd need every generator circuit to protect itself from reverse current coming from other generators.

But I'm currently learning about solar PV systems and noticed that 'net metering' is just us putting our inverter paralel to the grid.

Thing is I am really not knowledgeable enough about AC to make this oversimplification – is it really that easy?

Best Answer

Question isn't clear. What do you mean with "sum"?

Differences are pretty complicate but, I attempt the silly thing to describe it in 2 sentences.

If you place DC sources in series, you get the voltage equal to the sum of all the sources' voltages. If you place them in parallel - given a diode between each positive lead, to avoid short circuits (author's note: thanks to the user in the comments) - you get the voltage equal to the higher source voltage. About current: when they are in series they all supply an equal amount of current as far as they all can supply the requested amount; when they are in parallel instead, the one with higher voltage supplies the load alone until it lower the voltage (because can't sustain that power request) or fail.

AC is similar, actually more complicated. To start you MUST put the 2 sources in sync, otherwise any bad thing can happen. Usually what you do is checking the zero crossing point and use it to sync the two AC sources...

You probably see the AC being easier because solar inverters usually have connections to sync when connected in parallel.

That said, I invite you to start reading the basics and use your application as a learning tool, before attempting any experiment. Because it can be expensive and dangerous to hands on without the basic theory.