BLDC Sideband Harmonic Suppression Based on Carrier Synchronization at Commutation Time

For the high-speed brushless direct current (BLDC) motor driven by square wave, especially for high-speed applications, sideband current harmonics will be produced due to the limited switching frequency of inverter and the limitation of low carrier-fundamental frequency ratio, resulting in additional torque ripples. Meanwhile, a higher switching frequency not only lead to more switching loss and harmonics, but also increase the cost. Therefore, this study mainly intend to improve the pulse width modulation (PWM) commutation technology through the carrier phase-shifting control. The sideband harmonic current component under the natural sampling mode was firstly analyzed, then an improved PWM modulation method-carrier synchronous commutation was proposed to reduce and control the current harmonic component, by periodically resetting the phase of the carrier at the commutation time to improve the utilization of the PWM pulse and reduce the sideband harmonics, so as to reduce the torque fluctuation. In the end, the simulation and experimental verification and comparison are also carried out to prove the suppression effect of carrier synchronous commutation on the current sideband harmonics and torque ripples.