A High Gain Zero Current Ripple DC-DC Converter With Hybrid Coupled Inductor And Switched Capacitor

Nowadays,the energy issue is becoming more and more prominent.Traditional fossil energy sources have gradually replaced by new renewable energy sources.Fuel cells,as the carrier of new energy sources,have the characteristics of low output voltage and wide range of input voltage changes.In order to satisfy the requirements of fuel cell's on-grid,a high gain DC-DC converter is needed in the rear stage.How to break through the limit duty cycle of traditional boost converter and further increase the gain of converter becomes the focus of research.Firstly,the advantages and disadvantages of several high gain DC-DC topologies are analyzed.A new converter topology is proposed,in which switched capacitor voltage doubling unit and active clamping unit are added to the coupled inductor DC converter.On the one hand,this circuit can greatly enhance the DC voltage gain of the converter,avoiding the limit duty cycle of the traditional boost converter when the gain is high;on the other hand,it reduces the voltage stress of the switch tube and the diode,so the device of low voltage level can be selected.At the same time,the leakage inductance of-the coupling inductor can also restrain the reverse recovery current of the output diode.The active clamping unit is introduced to solve the problem of voltage spike caused by leakage inductance of coupling inductance.Simultaneously,all switches can be turned on at zero voltage,and the switching loss can be reduced.Secondly,in order to solve the problem of large input current ripple,the input inductance and intermediate capacitance are added to form a new topology.The zero ripple characteristics of input current are realized.Secondly,the characteristics of the converter,such as operating mode and converter gain,are analyzed theoretically after adding inductor and capacitor.The correctness of the theoretical analysis is verified by PSIM simulation.Finally,an experimental prototype with a power of 500W was fabricated,and the theoretical analysis of the proposed converter was verified by experiments.The experimental results show that the proposed converter can realize the grid-connected voltage of 380V in the voltage fluctuation range of input voltage 24V-48V,and realize the ZVS conduction of the two switching tubes,and the maximum efficiency of the converter can reach 96.8%.