Research On The Bi-directional Interleaved Resonant Converter

With the shortage of fossil energy,the problems of energy saving and emission reduction are paid more and more attent ion in the world,which makes micro-grid and electric vehicles develop vigorously.A large number of bidirectional DC/DC converters are used in the micro grid and electric vehicle to solve the energy storage and energy bidirectional flow problems.So the research of bidirectional DC/DC converter is important.Compared to traditional converters,the bidirectional resonant converter has the advantages of high operating frequency,small switching loss,small EMI noise,it is favored by experts and scholars.For the problem of the output current ripple of the resonant converter,the input par allel and output parallel half-bridge resonant converter is selected as the main circuit.The 90 degree interleaved parallel method is used in this paper,the output currents of the two phases are superposed together,so that the current ripple is greatly reduced.In this paper,the equivalent model of the resonant converter in forward direction is established based on the fundamental analysis method,and the DC voltage gain and impedance characteristics of the converter are analyzed.The sufficient and nec essary conditions for the realization of the soft switch of the converter are studied.The quantitative calculation method of the top and bottom limits of the dead time of the switch tube in forward and reverse operation is proposed.This method provides a theoretical basis for the selection of the dead time of the converter and improves the sufficient conditions for the realization of ZVS.A new equivalent model is established for the reverse operation of the converter.The gain characteristics and impedan ce characteristics of the converter are analyzed.And a quantitative calculation process of the top and bottom limits of the dead time for converter in reverse operation is designed.A control strategy is proposed to increase the reverse gain of the converter,which can make the voltage gain of the resonant sink greater than 1 in the reverse operation.And switches of the inverse side can realize ZVS,and switches of the rectifier side can realize ZCS.The correctness of the method is verified by simulatio n and experiment.The parameters of the two parallel phases can't be completely consistent,so current share can't achieve during the operation.In the paper,the influences of the resonant devices' tolerance and working frequency point are analyzed respectively in the forward and the reverse direction.By using the extended description function method,the precision small signal modeling of the converter in forward direction is carried out,and the result is compared with the simulation results to verify the correctness of the modeling method.Based on the model,the PID regulator is designed,and the stability of the converter is analyzed in the discrete domain.A simulation model of bidirectional interleaved parallel resonant converter is built in MATLAB to verify the theories above.An experimental prototype of 0.9k W is built,and the consistency between the experimental results and the theoretical results is analyzed.