DTC of a CSI-fed induction motor with DC link based adaptive estimator

Direct torque control (DTC) of a current source inverter (CSI) fed induction motor is proposed in the paper. The main contribution of the paper is a flux estimator with only two inputs (the current and the voltage measured from DC link) and a modified integrator with an adaptive compensation. The stator current, voltage and resistance are determined by a reconstruction from DC link measurements, known characteristics of the inverter semiconductors and the current states of the inverter switches. The rectifier is controlled by a PI current controller. The rectifier current reference is resolved from the torque and the rotor flux references in the similar way as in the standard vector control scheme to obtain fast DC link current response at all speeds. For the torque control, the optimal current switching-vector table is used. Simulation and experimental results are provided to confirm the performance of the proposed control algorithm. Some of these results are compared with those obtained with the vector control method of the same drive.