Search

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.

Cascaded H-Bridge (CHB) topology is one of the attractive topologies in high-power medium-voltage motor drive applications due to its modularity and scalability. Research in high power regenerative motor drives has gained significant attention with the increasing demand for efficient energy use. In a cascaded H-Bridge (CHB) converter, the regenerative capability can be introduced by replacing diode front end (DFE) with active front end (AFE) topologies. However, this results in a huge increase in the number of power semiconductors, gate drivers, and heat sink size and thus increases the overall size and cost of the regenerative CHB motor drives. To overcome the aforementioned challenges, different power cell designs have been introduced to reduce the switch count, allowing the design of more suitable-sized and more economical drives. This paper comprehensively reviews the reduced switch-count power cell designs, including single-phase and three-phase grid connections. Each reduced switch-count cell design is analyzed, and its advantages and disadvantages are studied in detail. The challenges that arise with each design and the method to address the challenges are discussed.