Research On A Bidirctional DC-DC Converter For A Low Voltage Energy Storage Systerm

In recent years,environmental problems and energy crisis become more serious,which affects people’s health and the production of all walks of life.The development of electric vehicles,solar energy and other new energy sources has become an important measure to alleviate environmental pollution and energy crisis.In the new energy system,the bi-directional DC-DC converter,which is responsible for bidirectional energy flow management,is essential,and its efficiency and reliability directly determine the efficiency and reliability of the whole system.Based on the traditional push-pull topology,the DC-DC converter introduced the series resonant unit resonant with the leakage inductance of the transformer,which effectively avoids the problems of voltage spike and can ensure all switches achieve zero voltage turn on and zero current turn off within the whole input voltage and full load range.For low-voltage and high-current input occasions,the transformer of the proposed converter uses primary side series and secondary side parallel structure,which reduces the transformer turns ratio,transformer volume and leakage loss,further increasing the transmission power,improve the conversion efficiency.In this paper,the forward and backward operating process and the principle of the soft switch are analyzed.Then,the gain characteristics of the converter are analyzed,and the realization method of the converter used in AC bus and DC bus is analyzed.Then the losses of each part of the converter are modeled,and the efficiency of the converter is calculated under different loads by using the loss model.The calculated efficiency and actual efficiency are compared with each other,and the scheme of further efficiency optimization is given.Finally,a 2.5kW experimental platform was built in the laboratory to verify the correctness of the above theoretical analyses.The selection and manufacture method of the main power devices and the matters needing attention in PCB drawing are presented.Simulation and experimental verification are carried out.And the simulation and experimental results prove that the realization of soft switch,the bi-direction flow of energy and so on.At the same time,the overall efficiency of the system is given,which shows that the system has high efficiency both in the forward mode and backward mode.