Research On A Bi-directional AC-DC Converter Based On Active Clamp Magnetic Reset

The environmental problems caused by the traditional rough development mode restrict the economic sustainability and social health.The electric power industry,based on coal-fired power generation,has become one of the chief ‘pollutant sources'.Under the background of energy-saving and emission reduction,renewable energy has got wide concern and sustained investment.In recent years,micro-grid system attracts many scholars due to its ability of optimizing renewable energy sources.Micro-grid itself can not store energy.Moreover,natural conditions fluctuates renewable energy power generation.Thus,energy storage batteries are needed in micro-grid system to ensure the system's power balance and stability.The main content of this paper is to study the AC-DC converters capable of bidirectional power transmission applied as the interface between AC grid and storage batteries.Firstly,this article proposes a single-stage three-phase current-source bidirectional AC-DC converter after a significant derivation.The converter without coupling capacitor has two transformers in series.And current SVPWM is used to control the presented converter.Owing to the lack of applying six sectors current SVPWM strategy in the proposed converter,a twelve sectors current SVPWM strategy based on the detailed analysis of the relationship between current vectors and switching modes is presented.And the division of twelve sectors and the specific calculation of synthetic current vectors are given after that.The improved SVPWM strategy reduces the number of power transistors working in high frequency.Then,active clamp magnetic reset of the transformers is introduced.In order to realize unit power factor in grid-side,controlling of grid-side currents is important.The converter's mathematical models in three-phase static coordinate system and two-phase rotating coordinate system are given.On top of the direct current control strategy based on dq coordinate,the settings and digital realization of PI regulator are analyzed.After that,the simulation model of the converter is established In PLECS.By combining the simulation results,the text describes the mechanism of current ripple difference at different positions and gives explanation of current distortion occurring when two phase voltages are equal in rectifier mode.At the end of this article,voltage and current stresses of power transistors are analyzed according to the working characteristics of the converter.In addition,the main circuit parameters and control circuits are designed.In the laboratory a 2kW prototype is built to verify the analysis ahead.