Implementation of Speed Sensorless Vector Control Using Three-Phase Unfolding

This paper introduces a comprehensive approach to implement speed sensorless vector control for an induction machine using a non-isolated three-phase unfolding-based dcac converter. The unfolding topology comprises a non-inverting buck-boost converter and a voltage balancer circuit in the high-frequency switching dc-dc stage, coupled with a T-type inverter in the fundamental frequency switching unfolder stage. This topology offers reduced inverter losses, minimized dc-link capacitor requirements, and no transformer isolation, making it a promising alternative for two-stage motor drives. The model reference adaptive system (MRAS) is utilized for motor speed estimation, and the control scheme is validated through extensive experimental results on a 5 kW hardware prototype.