A modified hysteresis-based DTC strategy for synchronous reluctance motors in high speed range

This paper presents a modified hysteresis-based direct torque control (DTC) for synchronous reluctance machines. The proposed method is utilized to achieve high torque capability in flux weakening region. It will be shown that hysteresis-based DTC is established by two hysteresis comparators. A higher torque capability is fulfilled by switching only the optimized voltage vector during torque dynamic condition, instead of alternating between two vectors. The selection of optimized voltage vector can be implemented by modifying the flux error status generated by the stator flux comparator before it is fed to the switching table. The main benefit of the proposed method is its simplicity because it requires only a minor modification to conventional hysteresis-based DTC and does not require a space vector block. The effectiveness is verified by simulation.