Research On Control Strategy And Current Sharing Characteristics Of Interleaved Parallel Bidirectional LLC Resonant Converter

Now LLC resonant converters are widely used due to their primary zero-voltage turn-on(ZVS)and secondary zero-current turn-off(ZCS)characteristics.However,traditional LLC resonant converters do not have the symmetry of bidirectional energy transfer.Therefore,a resonant converter of the CLLLC topology has been proposed to implement soft switching in both forward and reverse modes of operation.At the same time,the staggered parallel connection mode is introduced to achieve the purpose of increasing the transmission power and reducing the output current ripple.Firstly,the fundamental wave analysis method is used to analyze the working principle,modal and gain characteristics of the bidirectional LLC resonant converter,and its resonance parameter and frequency influence on the gain are analyzed according to its gain formula.On this basis,the extended description function method is used to derive the small-signal model of the bidirectional LLC resonant converter,and the corresponding compensator is designed to realize the closed-loop control of the voltage,so that the output voltage is quickly stabilized at the ideal output voltage.Secondly,for the problem of uneven current caused by the difference in the actual two-phase resonance parameters,the gain of a phase is adjusted by controlling the phase shift angle to realize the two-phase current sharing.However,the difference between the two-phase resonance parameters and the adjustment of the phase shift angle will cause the output current to be distorted,the output current ripple becomes larger,and the transmission efficiency is lowered.Therefore,the phase difference of the two-phase output current is changed by changing the two-phase stagger angle,and the current ripple is reduced.By theoretically,there is a stagger angle to minimize the output current ripple,and the phase shift angle,the stagger angle and The curve of the output current ripple as a function of the resonance parameter.Finally,by comparing the efficiency curves of the bidirectional LLC resonant converter under the full load range under different control strategies,the optimal control strategy is obtained,and the high efficiency in the full load range is achieved.A 400V-48 V,1kW prototype is built to verify the correctness and feasibility of the proposed solution.