Direct Torque Control with Space Vector Modulation for Induction Motors Fed by Cascaded Multilevel Inverters

Direct torque control (DTC) has achieved utilization on two-level inverters and three-level diode-clamped inverters, and it has high performance of speed control. But DTC hasn´t been utilized to cascaded multilevel inverters at present. In this paper, a novel space vector modulation (SVM) approach for cascaded multilevel inverters is presented firstly. Then by combining it with the DTC approach based on SVM, the approach of using DTC to cascaded multilevel inverters is presented. And it is verified by using a three-cell cascaded frequency control laboratory system. The proposed approach solves the issues that switching state table is difficult to generate and switching frequency is not fixed, which is arisen from using conventional DTC to cascaded multilevel inverters. It will be of benefit to the utilization of DTC on the speed control of induction motors fed by cascaded multilevel inverters