Research On Study On New Energy Source Oriented Multi-port DC-DC Converter

The utilization of clean and renewable energy resources is widely studied and developed nowadays to cope with the shortage of fossil energy resources and environmental problems. However, in the construction of power systems oriented to new energy resources, there are many problems to be studied and solved, such as the random and intermittent characteristics inherited in solar and wind energy, the dynamic performance of fuel cell in electric vehicles, and the energy management problems in a multiple energy power system.The dissertation aims at the multiport converter that couples multiple energy units via high frequency transformer to meet the needs of electric vehicle’s energy management system.The necessity of a multiport converter that coordinates fuel cell, battery and supercapacitor energy unit to insure the system dynamics and economics is discussed. In the analysis of present status of multiport converter technique, some fundamentals such as basic DC/DC, uni/bi-directional converters, the DC bus-coupled and transformer-coupled multiport converter are summarized and discussed.According to the demand of the energy management of electric vehicle, a topology of a transformer-coupled three port electric vehicles energy management converter, with two ports repectively connected to battery and supercapacitor, and one port for vehicle’s electric load.The converter is mainly composed of a transformer with three windings and three phase-shift controlled active bridges. The converter can meet not only the requirement of low voltage input, low ripple current, and electrical isolation, but also can meet the needs of soft switching and easy controllability in engineering realization.The main research works are summarized as follows:(1) The operation principle of the converter is analyzed in detail, and the design method of magnetic components as three windings transformer is discussed.(2) The soft-switching conditions for the converter’s commutation is analyzed and verified by simulation.(3) The strategy and structure of the controller are studied, and decoupling control of energy flow among the multiple ports is realized, to achieve good dynamic and static performance, and correlation analysis and design are verified through the simulation.(4) A prototype system composed of an above-mentioned converter with its DSP-based controller is designed and constructed in the laboratory. The experiments performed on the prototype system verified the results derived from theoretical study.