Sensorless V/f control with MRAS speed estimator for a five-phase induction machine under open-circuit phase faults

This paper introduces a sensorless scalar controller with MRAS speed estimator based on simple Proportional Resonant PR controllers to provide a disturbance-free operation to a five-phase induction machine under phase open and based on optimal current control. The machine speed is estimated using MRAS observer based on rotor flux (RF-MRAS). Under open phase, the torque-producing fundamental sequence current is used to estimate the required third sequence current components to ensure equal remaining healthy currents. Two PR controllers are then used to determine the corresponding third sequence voltage components. The used optimization criterion ensures maximum fundamental torque, minimum torque ripples, and equal line currents. The proposed controller is verified using a 1.5hp prototype machine for both dynamic and steady-state cases.