Research On Soft-switching Techniques Of Isolated Multi-ports DC/DC Converters

As the energy crisis and environmental pollution have been aggravated, the new energy andelectric vehicle are thought to be the preferable solutions to this problem. In these applications,several new energy sources and traditional energy sources are integrated to power the load, along withthe batteries and super capacitors. In such system, to interface various sources or loads with differentvoltage stages, a galvanic multi-ports dc/dc converter (MPC) is of practical use, which leads to asimpler configuration and lower cost. To further improve the system power density, the converterswitches also need to achieve zero-voltage-switching (ZVS) so that the switching loss can reduce andsystem efficiency increase. This paper just centers on the soft-switching techniques of MPC.The triple active bridge (TAB) dc/dc converter which is derived from the dual active bridge(DAB) dc/dc converter can be appropriate for these systems. But either TAB and DAB converter’soutput and input currents ripple are large. Therefore, based on the proposed boost-integrated DABconverter in this paper, a boost-integrated TAB converter has been proposed too. The proposed twoconverters have the advantages of being able to achieve ZVS and simple control strategy, and they aresuitable for the applications with low current ripple requirement. In this dissertation, based on theresearch on DAB converter, the operation principle and ZVS conditions of the TAB converter and theBoost-integrated TAB converter are described in detail. Specially, the ZVS condition is deduced onthe basis of particular calculation and analysis of the resonant process that occurs at the moment ofswitching, which is in consideration of the junction capacitors of switches. Finally, a1kW and a1.2kW prototype converter and a1.2kW simulation model have been built to verify the theoreticalanalysis.