Theoretical And Experimental Research On Synchronous Rectification Technology Of Buck-Boost Converter

Micro photovoltaic grid-connected inverter as a single micro power unit,with its flexible,intelligent,efficient and other characteristics is deeply welcomed by people.A drag four isolated micro grid-connected photovoltaic inverter scheme is proposed in the condition of a wide understanding of photovoltaic power generation technology industry background as well as photovoltaic grid connected inverter circuit topology.Two key problems of the proposed scheme have been studied in indepth.The first problem is the control problem of the former stage converter.In order to realize the converting of the former stage converter that used to convert the output voltage of the PV.The Buck-Boost converter which can be lifted up and down is adopted in this scheme.Dynamic modeling is established for the discontinuous current mode and the current continuous mode of Buck-Boost converter.Then the closed-loop control system of Buck-Boost converter with discontinuous current mode is designed.And at last a closed-loop control system simulation platform in Matlab/Simulink platform for verification is built.Secondly,the problem is the conversion efficiency of the grid-connected inverter.The conversion efficiency of grid-connected inverter is ascribed to the conversion efficiency of former stage converter substantially.The transmission loss of rectifier diode of the front stage Buck-Boost converter is especially significant in the engineering application of this paper.In order to solve this problem,the synchronous rectifier technology is adopted in this paper.The core issue of Synchronous rectification technology is synchronous rectification driving circuit designing,which based on the extensive research of existing synchronous rectification drive circuit.The characteristics of all kinds of synchronous rectification driving circuits are analyzed.And the existing synchronous rectification driving circuit of the advantages and disadvantages are summarized too.The current status of the research on the driving circuit of the current type self driving synchronous rectifier is analyzed in the paper,and the problems of the current type self driving synchronous rectifier are summarized emphatically.For the problems of large power consumption,limiting to a specific topology and circuit parameters cannot adapting with current synchronous rectification driving methods,a new type of adaptive current self driven synchronous rectification driving circuit scheme is presents in this paper.The circuit principle and design idea of this scheme is analysed detailed.The analysis is mainly through the saving mechanism of the proposed scheme,parameter adaptive mechanism and accurate closed off mechanism principle.On the condition of analyzing the principle of the scheme,the principle of the circuit’s parameter optimization is given.The simulation platform of the scheme is built on the Psim.And the mechanism of reducing consumption,adaptive mechanism and shutdown mechanism are verified.A Buck-Boost converter experimental prototype for proving the theory design is built finally.Then the efficiency of the adaptive current type self driven synchronous rectification driving circuit of Buck-Boost converter and the Schottky diode rectifier Buck-Boost converter are compared.Experimental results verify the correctness of the design theory.