Dear Vivekanandan,

I think you mean Micro Grid instead of the general concept of Smart Grid, don't you?

DG units have to control the frequency and voltage of the micro grid the same as typical power plants. Note that the output power of the most of DG units such as Wind Turbines, and PV panels is stochastic and thus it needs to consider the load balance constraint in each time of the day.

I recommend you study the papers regarding micro grid issues.

Regards,

Morteza Shabanzadeh

http://mortezash.blogfa.com/