Revised Topology and Control Strategy of Three-Phase Cascaded Bridgeless Rectifier

This paper proposes the improved topology and control strategy of three-phase cascaded bridgeless rectifier (CBR) suitable to serve as the rectifier stage for a medium/high voltage multilevel converter. Compared with traditional H-bridge based multilevel rectifiers, the proposed topology adopts much fewer fully-controlled devices, which greatly reduces the control complexity, thus increasing the system reliability and cutting down the implementation cost. A hierarchical control strategy is presented to achieve desired power factor and balance the output dc voltages. By appropriately distributing the ac voltage of the rectifier among bridgeless modules and H-bridge modules, input current zero-crossing distortion is avoided, guaranteeing a satisfactory current quality. Simulations results have validated the proposed theories.