Research And Design Of Three-Port DC-DC Converters

With the increasing demand for energy source and deterioration of ecological environment,it has become the top priority to fully develop new energy sources for energy supply.However,renewable energy sources are generally affected by environmental factors and the output tends to be discontinuous,unstable and unpredictable.Therefore,it is important to introduce energy storage modules.Since the traditional one input one output topologies are unable to meet the interface requirements of the system,the researches on three-port and multi-port structures emerge.In view of the photovoltaic input systems,this thesis summarizes and proposes the direct combination method and the direct composition method,whose composition forms and constituted topologies are studied.In this thesis,the principle and characteristics of direct combination method are introduced firstly,and a new three-port converter based on BUCK-BOOST bi-directional converter and LDO module is constructed.The mode analysis,control design and experimental test are carried out in detail.The test results show that the three-port converter,which is composed of direct combination method,has the advantages of direct energy transfer,simple control,diverse structure selection and easy cascade expansion.Secondly,the principle and characteristics of direct construction method are summarized and studied.Based on the analysis of applicable structure and composition principle,a novel BUCK threeport converter based on flying capacitor circuit is constructed to verify the correctness of the direct construction method based on energy path reconstruction.The mode analysis,control design and experimental test are also carried out in detail.The test results show that the three-port converter,which is composed of direct composition method,has the advantages of simple structure,high system power density,high circuit multiplexing rate,and easy centralized control.Finally,the detailed design flow is given by taking the new BUCK three-port converter as an example,and the prototype is debugged and tested.Through the analysis of the test results,it can be seen that the two new three-port converters proposed in this thesis can realize the energy flow of three ports,the stable output and smooth switching of each mode.