Dynamic Response of Wound Rotor Induction Generator for Wind Energy Application

Abstract

The magnitude and frequency of the output voltage can be controlled by varying the effective rotor resistance of a wound rotor induction generator (WRIG), over a wide speed range. For a given stator load impedance, both the frequency and the voltage can be maintained constant as the speed is varied, without changing the excitation capacitance. When the stator load is variable, simultaneous voltage and frequency control requires the excitation capacitance to be changed as the rotor resistance is varied. Simulations performed on a 1.8-kW  wound rotor induction machine confirm the feasibility of the method of control. Simulated implementation of a closed-loop control scheme for a WRIG using chopper-controlled rotor resistance is also discussed. With a properly tuned proportional-plus-integral (PI) controller, satisfactory dynamic performance of the WRIG is obtained. The implemented  scheme may be used in a low-cost variable-speed wind energy system for providing good-quality electric power to remote regions.

Index Terms—Induction generators, slip-ring machines, voltage and frequency control.