A Novel Direct Torque Control of Doubly-Fed Induction Generator Used for Variable Speed Wind Power Generation

In this paper, a novel direct torque control of doubly-fed wound rotor induction machines is proposed and applied to variable speed wind power generation systems. The proposed control strategy was developed based on the control of the rotor power factor. By keeping the rotor power factor equal to one, a switching-table-based hysteresis direct torque control system was built and the corresponding rotor voltage vector table was obtained. The validity of the proposed method was examined using the simulation of the variable speed winding power generation. Promising results were obtained and attractive advantages of the proposed control idea were illustrated including simple structure of the control system, low capacity of the inverter, reduced harmonic pollution to the power grids as well as the other advantages.