Robust Non-Linear Direct Torque and Flux Control of Adjustable Speed Sensorless PMSM Drive Based on SVM Using a PI Predictive Controller

Abstract

This paper presents a new sensorless direct torque control method for voltage inverter – fed PMSM. The control method is used a modified Direct Torque Control scheme with constant inverter switching frequency using Space Vector Modulation (DTC-SVM). The variation of stator and rotor resistance due to changes in temperature or frequency deteriorates the performance of DTC-SVM controller by introducing errors in the estimated flux linkage and the electromagnetic torque. As a result, this approach will not be suitable for high power drives such as those used in tractions, as they require good torque control performance at considerably lower frequency. A novel stator resistance estimator is proposed. The estimation method is implemented using the Extended Kalman Filter. Finally extensive simulation results are presented to validate the proposed technique. The system is tested at different speeds and a very satisfactory performance has been achieved.