A Reduced Switch Count Power Cell for Regenerative Cascaded H-Bridge (CHB) Converter

This paper proposes a new reduced switch-count power cell for a regenerative Cascaded H-Bridge (CHB) motor drive that reduces the number of switching devices per power cell from ten switches to six switches. The proposed power cell employs a Four-Switch Three Phase Inverter (FSTPI) at the front-end and a half-bridge inverter at the output of the power cell. The new configuration introduces four challenges: cell input current unbalance, input low order harmonics, DC-link voltage capacitor balancing, and switching harmonics. This paper analyzes and addresses these issues to ensure proper operation, control, and compliance with grid connection standards. The solutions are verified through simulation studies of a 3kV CHB motor drive and experimental validation with a single power cell setup. The results show the possibility of replacing the traditional power cell with a proposed cell, effectively reducing the required number of switches from ten to six.