Sensorless field oriented control for double inverter fed wound rotor induction motor drive

A novel control technique for sensorless vector control operation of double inverter fed wound rotor induction motor is presented. Two current controllers control the stator side currents based on vector control algorithm. Another V/f type flux and frequency controller controls the rotor side frequency directly. A novel frequency command profile for the rotor side controller is suggested to make this sensorless drive operation reliable and less dependent on motor parameters at any rotor speed. A complete inverter power flow analysis is presented to show that the drive can deliver full torque from 0 to 2 p.u. speed for either direction of rotation. Thus, double the rated power can be extracted from the induction motor without overloading it. The proposed algorithm allows the drive to start on-the-fly without any rotor transducer.