Topologies and Operations of Hybrid-Type DC-DC Converters Interfacing DC-Current Bus and DC-Voltage Bus

Along with the application of current source converter (CSC), there will be more and more dc-current bus (DCB) for supporting power conversion. The DCB usually provides a common current, and the bidirectional voltage is employed to realize the bidirectional power transmission. In the current power system, the dc-voltage bus (DVB) is most widely used dc terminal. Then, it will be foreseeable that topologies that can connect the DCB and the DVB will be urgently needed in the future grid system, such as the dc grid and electric vehicle. However, to connect these two dc terminals, the middle ac power stage is usually required since the power transfer characteristics of these two dc terminals are incompatible. Thus, the hybrid-type dc-dc converter concept interfacing the DCB and the DVB will be discussed, and the potential hybrid dc-dc converters without or with electric isolation are presented in this article. Moreover, for these hybrid dc-dc converters, the basic principle for the modulation operation is proposed and analyzed. In addition, by using a nonisolated two-level bidirectional hybrid dc-dc converter and an isolated full-bridge hybrid dc-dc converter as examples, the modulation methods for bidirectional transferred power are illustrated in detail. Finally, the simulation and experiment results of the isolated full-bridge hybrid dc-dc converter are used to verify the effectiveness of the proposed hybrid dc-dc converter idea and the corresponding modulation methods.