how to achieve grid synchronization ?, how to calculate phase?how to calculate grid voltage?

We are doing a project called Digital Control of Grid-Connected Converters. My part of this project about the grid Synchronization.

I have couple questions if you can write like 2 pages about the answer of these questions ?

grid Synchronization is AC not DC.

How do you achieve grid Synchronization? Essay question

How to calculate the phase ?calcu

How to calculate grid voltage ?calcu

By using these equations , i wants to know how to use these three functions

wg=2 pi fq

Phase locked loop ? essay question