Research On Multiphase Step-up Half-bridge Converter

In the new energy field,there are many low-voltage and high-current input sources.The fuel cell is a typical low-voltage and high-current input source.Firstly,according to the basic characteristics and requirements of the fuel cell power supply system and the research results of related scholars at home and abroad,this paper studies the current research status of multiphase high power isolated boost-type power converters,and compares,analyzes and summarizes the multiphase isolated conversions.The topological form of the device,the basic modulation method,the soft switching method to improve efficiency,and the rectification method.Firstly,based on the fuel cell power supply system,this paper designs a pre-stage DC/DC converter suitable for low-voltage high-current input sources such as fuel cells.The isolated boost converter has high DC voltage gain and low input current fluctuation.The steady-state operating characteristics and the soft-switching process are analyzed in detail.The steady-state operation process includes the analysis of the ideal mode of operation and the operation modal analysis after the transformer parasitic parameters are added.The soft-switching process is based on the principle of resonance and deduces the switching device theory.The conditions for soft switching are implemented.Based on the steady-state analysis,the state-space average method is used to model the converter’s multi-state small signal system,and the dynamic control model of the converter control system is obtained,and further based on the classical control theory,the boost in the average current mode.The half-bridge converter is designed with double closed-loop voltage and current loop controllers,so that the system can meet the requirements of the dynamic and static performance,and finally put the results of theoretical design into the matlab platform,the simulation to verify the feasibility of theoretical design.Based on the theoretical analysis,the power device selection,the design of the inductance and the transformer of the magnetic element,and the selection of the capacitance element were performed.The current-voltage sampling circuit and the driving circuit of the switching device were further designed.Based on the theoretical analysis and hardware design,based on the saber simulation software,the converter simulation model was built to observe the dynamic and static performance of the system.The simulation results were consistent with the theoretical analysis and verified the rationality of the theoretical design.The 900 W prototype experiment was used to test the dynamic and static characteristics of the converter under actual conditions,which further validated the feasibility of the theoretical design.