Torque ripple reduction in DTC of induction motor driven by 3-level inverter with low switching frequency

A torque ripple reduction technique of direct torque control (DTC) for high power induction motors driven by 3-level inverters with the inverter switching frequency limited around 0.5-l kHz level is presented. It is noted that conventional DTC algorithms to reduce torque ripple are devised for applications with relatively high switching frequency above 2-3 MHz. Such conventional algorithms cannot accomplish satisfactory torque ripple reduction for 3-level inverter systems with lower switching frequency. A new DTC algorithm, especially for low switching frequency inverter system, illustrates relatively reduced torque ripple characteristics all over the operating speed region. Simulation and experimental results show effectiveness of the proposed control algorithm