It is hard to explain the various pieces, and they changed over the years.
If you are needing to understand grid connected PV inverter systems I suggest the following Arizona Public Service (APS) sample system design (see the 3-line diagram for grounding details):
I generally use a #6 equipment grounding conductor rather than the minimum #8 because it needs less protection. The utilities in Arizona insist on the equipment grounding conductor running from the inverter to the main grounding conductor, bypassing their expensive bi-directional digital KWH meter. However, the utilities are paying substantial rebates.
