A direct field oriented induction machine drive with robust flux estimator for position sensorless control

The rotor flux is estimated for a direct field oriented induction machine drive using a voltage-current mode algorithm, or physical based algorithm. The estimated rotor flux is used to synthesize the components of the rotation matrix, sin(θ_e) and cos(θ_e ). These angles are critical in transforming the command currents to the stationary frame such that field orientation is maintained. The principles of rotor flux estimation are presented, followed by examination of low speed effects, parameter sensitivity, and criteria for selection of the filter time constant, T_c. Computer simulation and extensive experimental results are included