| With the rapid advance of renewable energy and electric vehicle technology, the bi-directional DC/DC converters have been widely used in more and more applications like battery energy storage systems. This thesis does research on bi-directional DC/DC converters with wide input voltage range that are used to battery charging applications.In this thesis, several commonly used non-isolated and isolated bi-directional DC/DC topologies are reviewed, including phase-shifted full-bridge converter, Dual Active Bridge converter and full-bridge Series Resonant Converter(SRC). Then four potential topologies among those are analyzed based on loss break-down. Finally the two-stage Buck/Boost-SRC converter is chosen.SRC converter can hardly meet the requirement of wide voltage ratio range of bidirectional power conversion. In the thesis, a two-stage bi-directional DC/DC converter which combines the advantages of Buck/Boost and SRC is proposed. The converter will not only meet the requirement of wide voltage ratio range, but also keep the soft switching character of SRC. The operation principle and DC gain characteristics of Buck/Boost-SRC is analyzed, and the design method of resonant parameters is shown. In addition, frequency tracking control is designed to improve the control precision and efficiency of the converter. The implementation method and the close-loop design of frequency tracking control are studied.A5kW prototype is built based on the analysis above mentioned. The two-stage bi-directional Buck/Boost-SRC converter is tested with and without frequency tracking control. The verifying experiment results are compared with theoretical analysis. |
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