Research On Parallel Current Sharing Technology Of Bidirectional DC/DC Converter

Bidirectional DC/DC converter has great demand in micro grid energy storage system,electric vehicle and charging pile.LLC resonant converter has been widely used in the field of bidirectional DC/DC converter for its advantages of high transmission efficiency,wide range of voltage regulation,and zero voltage of switch tube in full load.In view of the problem of high output ripple and power level limitation of LLC resonant converter,the interlaced parallel technology is combined with the input Parallel,output Parallel converter.This thesis mainly studies the interlaced parallel full bridge LLC resonant converter.In this thesis,the full bridge LLC resonant converter is deeply studied,and the simplified model of LLC converter is obtained by using the fundamental wave analysis method.The DC normalized voltage gain characteris tics,input impedance characteristics,soft switching characteristics are analyzed.The normalized voltage gain of the reverse operation is always less than 1,so the reverse operation can only work in the buck mode.By using a new mode of resonant convert er,the reverse gain is greater than 1 by changing the working mode of the rectifier switch network,and the reverse work of the converter can also be in the boost mode.For the large output current ripple in LLC resonant converter,it can be effectively reduced by staggering 90 degrees between the sub modules of the two full bridge LLC converters.The factors that cause the unbalanced output current are studied,and the influence of the three resonant parameters on the output current is analyzed in detail.The traditional single variable frequency conversion control mode is analyzed.Combining the active current sharing and passive current sharing scheme,a scheme is proposed to realize the self average flow of the converter with the output side joining the common inductor and the droop characteristic of the LLC converter.The theoretical deduction and simulation verification of the current mean flow error in the scheme are carried out to verify the allowable flow error.Within the scope.Based on the extended function description method,the small signal modeling of interleaving full bridge LLC resonant converter is carried out,and the open-loop transfer function is obtained and the closed loop compensator is designed.Based on Matlab/Simulink,the converter is simulated and verified,and a prototype is built to verify the feasibility and validity of the model.