PI tuning of five-phase drives with third harmonic injection

The tuning of PI gains for a five-phase induction motor with indirect field oriented control and third harmonic injection is analyzed. Third harmonic injection allows to increase the output torque density. A study of the local linearized system shows that rotor time constant detuning and drive load play a crucial role in transient behavior. Also, it is shown that the PI tuning has to be obtained as a balance between conflicting interests. Some measures of the transient performance are presented and used to derive guidelines for setting the PI controller. The proposed guidelines involve a numerical procedure applicable to any drive with third harmonic injection, with either constant or variable ratio to the fundamental component. The results are illustrated by a set of simulation experiments.