Hybrid Hysteresis Controller for Long Voltage Vector Activation in Dual-Inverter DTC Induction Motor Drive

Abstract

Direct Torque Control (DTC) is widely used in induction motor drives due to its fast torque response, simple control structure, and direct regulation of electromagnetic torque and stator flux. However, the torque regulation performance of conventional DTC strongly depends on the selected voltage vector. In a dual-inverter fed induction motor drive, several voltage vector magnitudes can be produced, including short and long voltage vectors. Short voltage vectors may provide limited torque correction, especially during high torque demand or rapid torque reference changes. This paper presents a hybrid hysteresis controller for long voltage vector activation in a dual-inverter DTC induction motor drive. The proposed controller combines the conventional torque-flux hysteresis control of DTC with an additional torque-error-based hysteresis activation logic. When the torque error exceeds the defined threshold, the proposed controller activates long voltage vector selection to provide stronger torque correction. The system is evaluated using MATLAB/Simulink under a torque reference step from 1 Nm to 4 Nm. The simulation results show that the proposed hybrid hysteresis controller maintains the estimated torque closer to the reference value, improves the speed response, and provides stronger voltage excitation compared with the conventional vector selection condition. The proposed method maintains the simple structure of DTC while improving the torque correction capability of the dual-inverter drive.