Hi Yianie,
if you art refering to those stackable grid tie inverters which are plugged ito a ground fault receptical and convert wind or solar power to feed back into the grid, If not mistaken, they are not UL approved, ( here in the U.S.), thus you should not be using them for grid tying....I believe that kind of stuff is refered to as "Guerrilla power" doing something without approval.
Power companies can be very fickle...somethimes rightfully so and sometimes not.
It would be best just to keep the mill seperate and use a battery bank for seperate use.
From what I can tell grid tying requires a whole new can of worms to be opened, such as costly programmed inverters, smaller wire and larger number of turns for you stator, and then there's approval before the power company will allow it to be connected....and from what I'm hearing out there, the power comapny will usually shoot it down if its not UL approved.
All the best,
Gavin
