| The popularization of automobiles has promoted the rapid development of social economy and modern civilization,but also brought serious problems of energy security and environmental pollution.Energy conservation and environmental protection have become the theme of automobile technology development.Government subsidies and car factories have boosted the development of electric cars.Bidirectional on-board charger is an electric vehicle battery charging and discharging equipment,its energy conversion is mainly achieved by isolating DC/DC converter.The power battery should be charged according to the battery charging characteristics to provide a wide range of voltage,discharge under the changing battery voltage can still provide a stable power.Based on this,an isolated bidirectional converter which can be applied to the vehicle charger is designed to meet the requirements of bidirectional power transmission,wide gain and high efficiency.Firstly,based on the research status of bidirectional isolated DC/DC converter at home and abroad,two additional switching tubes are introduced into LLC resonant converter,and a bidirectional DC/DC converter with wide output voltage range is proposed.The forward and backward operation of the proposed converter is controlled by constant frequency.The different control strategies and working principles are analyzed in detail.Secondly,according to the working principle,the gain expressions of forward and reverse operation of the converter are derived respectively.The soft switch range of the converter is analyzed and the parameters are designed accordingly.The operating characteristics and principle of the bidirectional DC/DC converter were simulated and verified by PSIM software,and the software and hardware design of the converter with the power of 3k W was completed.Finally,an experimental prototype of bidirectional resonant converter with power of3 k W,input of 400 V and output of 105-420 V was built.The experiment was carried out under different working modes and different loads,and the efficiency curve was drawn.The results show that the highest peak efficiency of the converter is 97.7% in forward operation and 97.6% in reverse operation,which verifies the feasibility and superiority of the proposed converter. |
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