Improved virtual vector direct torque control of induction motor based on three-level NPC inverter

This paper describes the direct torque control method based on improved virtual vector modulation. Neutral-point voltage is used as feedback in control process. Through adjusting the operation time of each vector, the neutral-point voltage variation can be greatly limited and the voltage shifting can be eliminated. The DTC system with a high performance is constructed on the improved technique. Simulation results prove that the improved algorithm is feasible and suitable to the three-level DTC drive based on NPC inverter.