A Modulation Method With Current Zero-Crossing Distortion Elimination and Voltage Balance Control for the RSHMC Converter

Hybrid multilevel converters have gained more popularity due to their unique superiority. Thus, the reduced switch hybrid multilevel (RSHMC) converter is adopted in this article which consists three H-bridge cells and a Vienna rectifier. The RSHMC converter combines the advantages of these two topologies and can output higher voltage level by adopting fewer switching devices compared with other multilevel converters. However, the Vienna rectifier of the RSHMC converter has the inherent current zero-crossing distortion (CZCD) problem, which will increase the total harmonic distortion of the grid-side current. Thus, a modulation method based on phase disposition-pulsewidth modulation is proposed to eliminate the CZCD of the RSHMC converter by selecting redundant switching states. Besides, in order to ensure the normal operation of the RSHMC converter, the proposed modulation method can also realize the voltage balance control of the floating capacitor and the neutral point which is also realized by selecting the switching states to charge or discharge. Consequently, the RSHMC converter can operate normally with balanced voltage and without CZCD after adopting the proposed modulation method. Finally, the feasibility and correctness of the proposed modulation method are verified by simulation and experimental results.