Hello everyone, i would like to design a wind turbine for my university project. I didn't understand very well the work princeple of double fed induction generator.

Here is the connection schematic:
As i understood, the stator must be induced by rotor in order to generate energy. if the rotor is energized by stator how it can be produce magnetic field at the begining. Because there wouldn't be energy in the rotor windings. According this condition rotor windings are energized by grid power for generate magnetic field at the begining, isn't that right?

I would be very glad if you could help me to understand.