Simple Commutation Torque Ripple Reduction Using PWM With Compensation Voltage

In this article, a combination of a two- and three-phase switching method to reduce switching loss is presented. In the conduction region, the conventional two-phase switching topology is used to reduce switching loss. On the other hand, in the short commutation region, the proposed modified three-phase switching strategy that incorporates a voltage compensation method is used to reduce torque ripple. The design of the proposed torque compensation method is based on the back electromotive force (EMF). The goal is to optimize the phase current slope by using the phase voltage and back EMF at the start and end point of the commutation region. Assuming that the slope of the back EMF in the commutation region is almost the same as a sinusoidal waveform, a proper pulsewidth modulation duty ratio can be determined to control the current slope. Experiments with a practical brushless dc motor and drive were performed to verify the performance of the proposed method.