Control of stator torsional vibration in PM brushless AC drives due to non-sinusoidal back-EMF and cogging torque by improved direct torque control

This paper presents a comparative study of the stator frame torsional vibration induced in indirect- and direct-torque controlled permanent magnet brushless AC drives with non-sinusoidal back-EMF waveforms. An improved direct torque controller, which accounts for the influences of non-ideal back-EMF and cogging torque, is proposed. Its effectiveness in minimizing low order stator frame torsional vibration is validated and confirmed experimentally.