Effect of parameter and sensing errors on DTC IM drive operation

The direct torque control (DTC) of an induction motor drive carries out the closed-loop control of the stator flux magnitude and the motor torque. The feedback values are estimated by processing the inverter dc-link voltage and the stator currents through the motor voltage model. Any error in the model parameter (i.e. the stator resistance) and in transducing voltage and currents yields an incorrect estimation of the controlled variables, thus altering the drive operation. In this paper the various errors are considered and their effect on the drive operation is studied analytically. The study shows that some errors lead to instability of the drive whilst some others deteriorate its steady-state performance. The theoretical findings are substantiated by experimental results.