DOUBLY FED INDUCTION GENERATOR USING BACK-TO-BACK PWM CONVERTERS AND ITS APPLICATION TO VARIABLE-SPEED WIND-ENERGY GENERATION

The paper describes the engineering and design of a doubly fed inducti on generator (DFIG), using back-to-back PWM voltage-source converters in the rotor circuit. A vector-control scheme for the supply-side PWM converter results in independent control of active reactive power draw n the supply, from ensuring sinusoidal supply currents. Vector control of the rotor-connected converter provides for wide speed-range operat ion; the vector scheme is embedded in control loops which enable optim al speed tracking maximum energy for capture from the wind. An experim ental rig, which represents a 7.5kW variable speed wind-energy generat ion system is described, and experimental results are given that illus trate the excellent performance characteristics of the system. The pap er considers a grid-connected system; a further paper will describe a stand-alone system.