Frequency synchronization

Hello... I`m new here, Like your fourm vary mach .

I need help with my project.
I need to understand how Frequency synchronization in grid-tie inverter works.
when I say Frequency synchronization I meen Frequency synchronization bettwen the inverter output voltage and the grid voltage so I be able to feed the power back to the grid.

and now more question .
I understand that the inverter output voltage has to been slightly higher then the grid voltage. how much higher it has to be?? 1% more?

Your inverter lifting the grid by 1% is like a fly on the back of an elephant. The fly can flap his wings very hard but it will not move the elephant.

I don't think regulation voltage will make much difference to the power line. You should push a sign wave of current into the power line. The voltage will be what it is.
AND
Synchronization is the same thing. You can not change the power line so you must ride along.