A Practical Solution for Torsional Vibrations Evasion in Variable Speed Drives

The paper presents a practical solution for an existing drive-train to avoid torsional vibrations for variable speed drives under SPWM modulation technique. Torsional natural frequencies can be a problem because either ill defined in design stage or one of the mechanical parameters has changed after the initial design stage. The proposed method comprises of dividing the frequency range into several partitions where in each partition a value of modulation frequency ratio mf is chosen. A criterion is developed to choose mf based on avoiding torsional excitations with the minimum converter losses. Torque harmonic distortion and converter losses are analyzed. Matlab/Simulink is used to validate the approach.