A Bidirectional Multilevel Boost-Buck DC-DC Converter

A novel noninverting boost-buck dc-dc converter topology is presented, applicable when both sides of the converter need to have the same grounding. It is based on the back-to-back connection of two n-level active-clamped or diode-clamped converter legs, and allows bidirectional power flow. A simplified topology is proposed for unidirectional power flow applications. Two new pulse width modulation strategies with different advantages are proposed to operate the converter guaranteeing dc-link capacitor voltage balance in every switching cycle for all possible operating conditions and using small capacitance values. The semiconductor device losses are compared through analysis, simulation, and experiments to the losses in a conventional two-level boost-buck converter. The analysis yields a higher efficiency for the multilevel converter, especially as the number of levels increases. Experimental results are presented to validate the good converter performance in four- and five-level converter prototypes.