Kyo-Beum Lee, Joong-Ho Song, Ick Choy, and Ji-Yoon Yoo, "Torque ripple reduction in DTC of induction motor driven by 3-level inverter," The Transactions of the Korean Institute of Power Electronics, vol. 5, no. 6, pp. 620–631, Dec. 2000. > Paper

A torque ripple reduction technique of direct torque control(DTC) for high power induction motor driven by 3-level inverters with

the inverter switching frequency limited around 0.5-1.0kHz level is presented. It is noted that conventional DTC algorithms to

reduce torque ripple are devised for applications with relatively high switching frequency above 2-3kHz. Such conventional

algorithms can not 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 operation speed region. Simulation and experimental results show the effectiveness of the proposed control algorithm.