A direct torque control of induction motor based on three-level NPC inverter

The multilevel inverter has attracted great interest in the high-voltage high-power field because of its less distorted output. In this paper, a direct torque control (DTC) technique based on a three-level neutral-point-clamped (NPC) inverter is presented. In order to solve the intrinsic neutral-point voltage-balancing problem and to obtain a high performance DTC, a special vector selection method is introduced and the concept of virtual vector is developed. By using the proposed control strategy, a quick and robust response AC drive can be achieved without sensing the neutral-point voltage. The strategy can be verified by simulation and experimental results