Output selection for tuning of field oriented controllers: steady state analysis

This paper presents the use of local sensitivity analysis techniques to study which output signal of several proposed in the literature can lead to better performance of on-line tuning for rotor time constant variations using model reference adaptive control (MRAC) in indirect field oriented control (IFOC) of induction motors. The expectation is that the output with the highest sensitivity to rotor time constant should be the more suitable for IFOC controller MRAC tuning. We derive the output relative sensitivity functions for steady state operation for active power, reactive power, electromagnetic torque, and the ratio of reactive power and torque to rotor time constant and study their variability as a function of slip frequency. The relative sensitivity functions are used to study their usefulness for rotor time constant tuning. No signal can give uniform satisfactory sensitivity properties over the full range of machine operation. Suggestions are given on how to tackle this issue.