Reduction of parameter sensitivity in an induction motor current regulator using integrated pilot sensors in the low-side switches

A closed-loop synchronous-frame current regulator for an induction machine drive that is capable of delivering high-quality performance characteristics using integrated pilot current sensors in the three low-side switches of a three-phase bridge inverter has been developed. However, the necessary current reconstruction exhibits sensitivity to errors in the machine parameters, which has been documented during this investigation. This paper presents a technique for introducing a gated integrator into the controller gain amplifier that compensates for parameter errors using feedback information from all three of the phase currents during the periodic intervals when it is available. A numerical singularity in the current reconstruction algorithm during light-load operation is overcome by introducing an alternative first-order current estimator that is activated over narrow angular spans of the fundamental component vector rotation. This paper also presents an in situ technique to compensate gain differences between the three pilot devices in the inverter unit. The effectiveness of these improvements is verified using experimental results.