Stability Analysis of a Five-phase Induction Motor Drive Using Variable Frequency Technique

This paper presents stability analysis of a five phase induction motor drive using different control techniques such as Root locus, Bode plot and Nyquist plot. A dynamic model based on voltage- current and voltage-flux linkage relationship is developed. To evaluate the control performance of the five phase induction motor drive, a linearized model is used. The voltage -flux linkage model is derived from the dynamic model in d-q axes. To evaluate the control performance of the motor small perturbations are applied with the model. Five- phase induction motor drive may become unstable at low values of frequency. Transfer function of the drive is determined at different rotor frequencies and the effect on the stability of the drive is assessed using different control techniques. The value of the rotor frequency at which the drive becomes unstable is reported. The effect of variation of rotor frequency on the performance of the motor drive is analyzed. The analysis is carried out using Matlab codes.