Induction generators phasor simulation in dq coordinates with unbalanced operating conditions

This paper discusses the modeling for simulation based studies of induction generators in the context of power system electromechanical transient analysis and under voltage/current imbalance. Difficulties arise since voltage/current imbalance implies the presence of sinusoidal signal in the synchronous reference frame, which prevents dq variables to be directly associated to phasors and, consequently, to conduct phasor based simulations. An average phasor model is developed for the induction generator which decomposes the electrical part of the model into positive and negative sequence dq reference frames and neglect torque oscillations induced by current imbalance. The average model is developed in Matlab/Simulink applied to a simplified distributed generation system and its performance is evaluated by comparing to continuous (sinusoidal) simulations developed with Alternative Transients Program (ATP).