EXPERIMENTAL INVESTIGATION ON FLUX ESTIMATION AND CONTROL IN A DIRECT TORQUE CONTROL DRIVE

A Direct torque control algorithm involves a decoupled control of torque and flux with the help of two independent control loops. Estimation of stator flux requires an integration of motor back emf which is achieved by a pure integrator.Accurate Flux estimation algorithm, choice of flux hysteresis controller bandwidth in the flux control loopand the value of reference flux are the determining factors in Direct Torque control induction motor drive.An enhancement in steady state performance can be achieved byan efficient flux estimation algorithm. For sensorless drives voltage model based integration algorithm are most suitable owing to their less dependency on machine parameters. In this paper a comparison of voltage model basedlow pass filter flux estimation algorithm in terms of steady state flux ripples and stator current harmonics is carried out.Furthermore the influence of flux hysteresis comparator band magnitude on drive performance is also investigated. The proposed study is investigated through simulation and experimentally validated on a test drive