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 has been developed 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. However, the necessary current reconstruction exhibits sensitivity to errors in the machine parameters that has been documented during this investigation. This work 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.