Research On Control Optimization Of Bidirectional Single Stage Isolated AC-DC Converter For V2G

With the market share of new energy vehicles becoming higher and higher,in order to utilize the battery energy storage system of new energy vehicles efficiently and solve the increasingly serious power grid stability problems,the vehicle to grid(V2G)technology has emerged.In V2 G technology application system,the electric charge and discharge device plays an important role.The single-stage high frequency isolated bidirectional AC-DC converter studied in this paper has some advantages of dual active bridge(DAB)and single phase matrix converter(SPMC).Compared with the traditional two-stage AC-DC converter,the converter has only one-stage energy conversion structure and no intermediate DC link.It avoids the use of large volume and short life electrolytic capacitor.It has high power density and transmission efficiency in theory,and has good soft switching characteristics and easy to realize modularization.Firstly,the paper introduces the components of the converter and the DC side variable duty ratio modulation method based on single H bridge modulation(SHBM),analyzes the working state and soft switch characteristics of the forward transmission of power,deduces the characteristics of power linear control,open-loop unit power factor,establishes the average model and builds the output voltage closed-loop simulation.Secondly,considering the delay of controller and calculation error in practical application,it is difficult to meet the voltage second balance in half switching period in traditional modulation strategy.Switches of single-phase matrix converter topology in primary side lose ZCS soft switching.Therefore,a new optimal modulation strategy is proposed by introducing modulation coefficient.Based on the other advantages of traditional modulation strategy,switches of SPMC topology can realize ZVS soft switching.Then,based on the proposed optimal modulation strategy,considering the boundary conditions of inner mode and outer mode,the Lagrange multiplier method and Karush–Kuhn–Tucker(KKT)condition method are used to design the current stress optimization strategy.Compared with the traditional modulation strategy,the current stress of the switch can be reduced;in order to make the converter have the power factor adjustable function,the single-phase dq current decoupling control is studied,and this method can control both active power and reactive power transmission.Finally,the experimental platform of 1k W bidirectional AC-DC converter is built,which includes power circuit(including high frequency isolation transformer),software and hardware of control circuit,driver circuit design,etc.The basic working characteristics,modulation strategy and current stress optimization algorithm of the bidirectional AC-DC converter are verified by the platform.