On Grid Solar Plant

On grid solar plant requires synchronization with the frequency and phase of the grid, which is not a problem, can be achieved as part of inversion equipment. In the absence of Grid synchronization can be avoided to save cost. For any design, consider the parameters of Load characteristics, Voltages and maximum currents, other calculations can be derived. A grid-tied inverter just needs to pick up voltage and frequency from the grid, these parameters can also be picked from an external UPS or a generator. You will need to design the system as per the usage and know more about grid-tied inverters before designing such a system.

Grid Inverters can take reference from any AC Source, inverters, generators etc.
Size of such alternate source can be as small as 1 KW.
In absence of Grid, first Breaker connecting to Grid must be switched off before switching over to generator or any other source as reference.
In absence of Grid no power shall be fed to Grid, potential safety risks.
After switching over to say generator as reference, the power generated from solar can be stored in Batteries or fed to other Auxiliary load not connected to Grid.
Size of such Battery storage is limited mostly by budget, for full day storage the highest size can be 3 times the plant Wp capacity, e.g. 1MWp can take 3 MWh of Battery storage for full 1 day Grid back up.
Inverter will deliver the power depending on irradiation available & load connected.
Once Grid comes back the generator should be switched off before switching back to Grid.