| In recent years,with the continuous improvement of people's ecological consciousness,new energy technologies has been developed greatly.As an birenergy-way flow interfaces,bidirectional DC-DC converter have been widely used in a variety of industrial applications.According to the applicaiton of the magnetic isolation between primary and secondary,bidirectional DC-DC converter is divided into two types of isolated and non-isolated.However,the converter power density of the isolated bidirectional DC-DC converter is low due to isolated transformers.In addition,four power switches are applied at least.The switching loss is large and the conversion efficiency is low.With the elimination of the isolation transformer,the non-isolated topology of the bi-directional DC-DC converter is simple and easy to control,which attracts people's attention.This paper proposed a bi-directional DC-DC converter system based on Buck/Boost topology and LC resonant network.The new bi-directional DC-DC converter topology has implemented zero voltage on and zero voltage off conditions in both Buck and Boost modes due to the addition of a soft-switched resonant network,which greatly reduces the power switch switching losses and improves the conversion efficiency.In this paper,the working modes of the two models are analyzed in detail,and the equivalent circuit diagram is given.The differences of the ZVS soft switching conditions are compared between the two operating modes and the main voltage,and current parameters of the converter are quantitatively analyzed.For the proposed new topology,this paper chooses the Boost mode as an example to analyze.By means of reasonable linear approximation,a method of analyzing ZVS soft-switching condition is proposed,and the realization mechanism of ZVS soft switch is discussed in detail,and the formula to ensure that the converter ZVS soft-switching condition is given.Afterwards,the PSIM software is used to simulate two different circuit parameters.The validity of the theoretical analysis is verified by comparing the simulation results.The influence of the parameters of the system on the output voltage is analyzed by MATLAB software under steady-state condition,and an effective system parameter optimization design method is proposed.In order to ensure the high efficiency of bi-directional DC-DC converter system,to ensure that the power switch operates in the ZVS soft-switching conditions,meanwhile to achieve converter constant output,an adaptive control strategy based on PFM modulation with input voltage is proposed in this paper.In order to improve the stability of the bidirectional DC-DC converter system and the response speed of the system,the PSIM software is used to analyze the bidirectional converter system.Based on the open-loop frequency characteristics of the system,the closed-loop PI regulator is designed and digital closed loop control of the system is realized.Finally,this article designes and builds a 1k W prototype.The main circuit and control circuit of the bidirectional DC-DC converter system are designed and the control program is programmed,and then the experiments are carried out.The experimental results are in agreement with the theoretical analysis and simulation results.Under the rated input and output conditions,the maximum efficiency of boost mode is 96.65%,and the maximum efficiency is 97.04% in buck mode. |
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