Multi-mode SHEPWM with low switch frequency for traction application

To eliminate current harmonics and improve voltage utilization. When traction motor was run in high speed area, a new method is proposed that solve the harmonics component is high and transition which from SPWM to SHEPWM then to six-step mode on the condition of low switch frequency. The method was introduced, principles were analyzed and formulas were derived in this paper. The validity of the proposed method has been verified by simulation and experiments. The advantages of this strategy are it not only reduced the harmonics and torque ripple but also achieved transition from SPWM to six-mode on the condition of the switch frequency. It is no more than 1 kHz.