All grid-connected wind generator through a three-phase alternating current (AC) motor mechanical energy is converted into electrical energy. The generator is divided into two main types. Frequency synchronous generator operation and it is connected to exactly the same frequency of the grid, the synchronous generator is also known as an alternator. Asynchronous generator running frequency is slightly higher than the grid frequency, the asynchronous generator often referred to as induction generator.

    The induction generator and the synchronous generator has a non-rotating member is referred to as a stator, both the stator similar to the stator of the two motors are connected to the grid, but are posted by the three-phase windings on a laminated core. composition energized to generate a magnetic field at a constant speed rotation. Although both motor similar to the stator, the rotor is completely different. The rotor of the synchronous motor is a DC winding, called the excitation winding, the excitation winding to create a constant magnetic field for locking a rotating magnetic field created by the stator winding. Therefore, the rotor can always rotate to a constant a constant speed synchronized with the stator magnetic field and the grid frequency. In some designs, the rotor magnetic field is generated by the permanent magnet machine, but for large generator is not commonly used.

    The rotor of the induction motor type for example, it is a squirrel cage-shaped windings are short-circuited at both ends of a. The rotor with the outside world is not electrically connected to the rotor current relative movement of the rotating stator magnetic field generated by the rotor cutting. If the rotor speed is exactly equal to the speed of the speed of the stator magnetic field (with a synchronous generator), so that there is no relative movement, there is no induced current of the rotor. Accordingly, the overall speed of the induction generator is always rotating magnetic field speed is slightly higher than the stator, the speed difference is called slip, during normal operation. It was about 1%.