A Novel Discontinuous PWM Method With Hybrid Three-Step Commutation to Reduce Common-Mode Voltage for Direct Matrix Converter

The conventional discontinuous pulsewidth modulation (PWM) can provide several advantages in a direct matrix converter (DMC), such as less switching number and less execution time for modulation signals' calculation. However, it suffers from high common-mode voltage (CMV), which may cause damage to the DMC-based system. This article proposes a novel discontinuous PWM (DPWM) method to not only mitigate CMV but also further improve the conversion efficiency. In this method, the switching sequence is obtained in a new way using two medium and two small input line voltages, increasing the conversion efficiency. Besides, the proposed DPWM employs a rotating vector instead of a zero vector, which causes the CMV to reduce by 50% compared with the conventional DPWM. Notably, the proposed DPWM provides the above advantages while maintaining low total harmonic distortion (THD). Simulations and experiments have been conducted to verify the proposed DPWM method's effectiveness. The results of these tests support the claims made in the paper regarding the reduction of CMV, improved efficiency, and low THD.