Research On Interleaved Current-fed Push-pull Converter

In recent years,with the development of new energy power generation technology,fuel cells,wind energy,solar energy,biomass energy and other new energy resources are in the stage of large-scale applications because of their easy access,pollution-free,renewable and other characteristics.However,in the new energy generation system,the output voltage is low,and can not be directly connected to the grid or provide local load power supply.The DC-DC converter is needed to raise the low output voltage to a higher DC voltage,and then through the inverter grid-connected or power generation.Supply DC load.Therefore,it is very important to choose a suitable DC-DC converter.The current-fed push-pull converter has the advantages of low conduction loss,electrical isolation,simple structure,high utilization ratio of transformer,self-boosting capability and continuous input current,etc.It is suitable for low-voltage input occasions in front-end of new energy generation.Moreover,interleaving technology has the characteristics of reducing input current ripple and improving voltage gain.It is very suitable for new energy generation system with low voltage and high current input and high voltage output.Therefore,according to the research of the interleaved parallel DC-DC boost converter,a new type of interleaved parallel current-fed push-pull converter is proposed based on the push-pull converter.Compared with the traditional current-fed push-pull topology,the proposed structure is relatively simple.It only needs to add a simple clamp branch to effectively absorb the energy of the leakage inductance of the transformer,which can reduce the voltage stress across the power MOSFET,and realize zero-voltage-switching(ZVS)of all power MOSFETs.Firstly,the working principle and steady-state characteristics of the new converter are studied in detail.The important parameters of the circuit such as the voltage stress of the power MOSFET and the diode are derived,and are compared with the steady-state performance of the single-phase converter.The simulation results show that the proposed new converter has the advantages of ZVS turn-on,low voltage stress,small current ripple and so on.Furthermore,in order to realize the grid connection of new energy generation,based on the proposed new topology,an interleaved parallel current-fed DC/AC converter is reconstructed and the corresponding interleaved phase-shift DC/AC modulation strategy is proposed,which can reduce the switching loss of the DC/AC converter.In addition,the small-signal model of the proposed converter is established,and the dual-loop controller is designed.The parallel current sharing and phase-locked grid-connected strategy are discussed.The theoretical analysis,the simulation and experimental results verify the rationality of the design.Finally,an 800 W prototype has been designed and built.The experimental results verify the correctness and effectiveness of the proposed theory.