Dr. Mohamed Mahmoud Anwar Mohamed Sharawy :: Publications:

Self-excited induction generators usually suffer from variable output voltage frequency and magnitude as the wind speed varies when it is used in stand-alone Wind Energy Conversion Systems (WECS). In this paper, it is proposed to use doubly-fed induction generators (DFIGs) instead of squirrel cage induction generators. The proposed controller is based on feeding part of the output power to the rotor circuit. The frequency of the injected voltage is adjusted at each mechanical speed to produce stator frequency at the nominal value. The magnitude of the injected voltage is adjusted to control the output voltage. The capability of the proposed controller is verified using a simulation model. The simulation results confirm that the proposed control maintains both the magnitude and frequency of the output voltage constant at the nominal values irrespective of the wind speed variations. The proposed controller is implemented for the sub-synchronous speeds and a further study is now conducted to extend the capability to the super-synchronous range.