A Three-Level dc-dc Converter for Bipolar dc Power Grids: Analysis and Experimental Validation

The concept of bipolar dc power grids has emerged, mainly due to the improvements in efficiency and offered flexibility when compared with unipolar architectures. Though, concerns of asymmetrical loads affecting voltage unbalances is the key challenge to overcome. In this context, power electronics play an important influence since the features of the topology contribute to define the quality of the bipolar dc power grids. This paper presents the application of a bipolar bidirectional three-level (BB3L) dc-dc converter as a contribution to mitigate the aforementioned concern of bipolar dc power grids. The proposed BB3L dc-dc converter is introduced, and an insightful description of its principle of operation is presented throughout the paper. Since the BB3L dc-dc converter operates with three voltage levels, it is possible to diminish the blocking voltage of the switching devices, representing an important feature of such topology. Additionally, it can operate with the voltage and current variables controlled with the double of the switching frequency, also representing an added value of such topology. The distinct possibilities of operation are presented, both in buck-mode and boost-mode, and an experimental validation is presented to validate the main features of the BB3L dc-dc converter for bipolar dc power grids.