Asymmetrical behavior of a double-fed induction generator: Modeling, discrete event simulation and validation

The aim of this paper is to present a discrete event simulation of a three-phase wound-rotor induction machine in order to show the efficiency of the proposed method to take into account the different winding unbalances. In fact, these machines are used in large power wind turbine generators in which the fault detection becomes more and more a serious issue. Early fault detection in the machine windings could be of great use for protection and predictive maintenance design. Therefore the classical abc reference frame model of the induction machine is translated in block-scheme to be interpreted by the discrete-event system simulator. The time-domain analysis is transformed in frequency-domain by interpolation to translate the discrete event magnitude in fixed sampling frequency and then application of normalized FFT to obtain the machine current spectrum. The technique is applied to a 5.5 kW wound-rotor induction machine in normal operation and with winding (stator, rotor, stator+rotor) unbalances. The simulation results are compared to experiments to evaluate the accuracy of the proposed simulation technique.