Patent ID: 7215035
Filing Date: 2007-05-08
Classification: F03D,H02J,H02P,Y02E

Abstract:
1. A method of converting wind generated electricity to constant frequency electricity for supplying it to a utility grid, comprising: using a wind turbine generator having a doubly fed induction generator; generating electricity from the rotor of the generator for supplying it to the utility grid when operating at a rotational speed of the generator above synchronous speed; supplying electricity to the rotor of the generator when operating at a rotational speed below the synchronous speed of the generator and facilitating the generation of electricity from the stator; converting the electricity from the rotor to dc electricity and converting the dc electricity to ac electricity at a constant unity power factor of at least 0.99; and adjusting the current of the ac electricity to or from the utility grid to be in phase with the utility grid voltage, comprising the steps of: sensing a line to neutral voltage from the utility grid; generating a normalized voltage value by dividing the sensed line to neutral voltages by the peak voltage of the utility grid; multiplying the normalized voltage value by a desired current signal to produce a reference signal that is in phase with the utility voltage; sensing the current of the ac electricity to or from the utility grid; subtracting the sensed current from the reference signal to generate an error signal; and comparing the error signal to a triangular shaped signal to generate a control signal; wherein the ac electricity is at a constant unity power factor of at least 0.99.