Direct Torque Controlled Induction Motor Drive Based on Cascaded Three Two-Level Inverters

Abstract

In this paper, a new and an effective voltage switching-state algorithm to Direct Torque Control (DTC) of induction motor drive is proposed, which makes less torque and flux ripple at various operating frequency conditions. In conventional DTC , the torque and flux ripples are difficult to reduce as the applied voltage vector is independent of rotor speed especially at low speeds. To overcome this problem, the proposed technique introduces a voltage switching-state algorithm for four-level inversion using cascading three two-level inverters, in which choice of inverter voltage states is the function of rotor speed. From simulation results, the torque and flux ripple are decreased with proposed DTC when compared with the conventional DTC technique at various operating frequencies.