Research On Overall Performance Optimization Of DAB Converter Under V2G Background

With the large-scale integration of new energy generation and the popularity of electric vehicles,Vehicle-to-Grid(V2G)technology,which enables energy interaction between the power grid and electric vehicles,has attracted widespread attention and research.Dual Active Bridge(DAB)DC-DC converters,as a classic topology,have the advantages of high power density.structural symmetry,and simple control,making them ideal for use in bidirectional charging and discharging devices in V2G technology.However.under the background of V2G wide voltage range,the traditional single phase shift control has the problems of low operation efficiency and single optimization objective of optinal control strategy.Therefore,this study focused on DAB converters and proposed a multi-objecive optimization control strategy to improve their comprehensive performance within a wide voltage range,which was verified through simulation and experiments.Specific research contents are as follows:Firstly,the traditionnl single-phase-shift and triple-phase-shift control of DAB converters were analyzed,and mathematical models were established for transmission power,current stress,return power,and soft switching conditions.Through model analysis,it can he seen that when the voltage conversion ratio of single-phase-shift control increases,the range of soft switch becomes narrow,the current stress and backflow power will increase,leading to the deterioration of DAB converter performance.By increasing control variables,triple-phase-shift control can improve the problems in single-phase-shift control with a larger optimization range,although the working modes will increase and the analysis will be more complicated.Secondly,To improve the comprehensive performance of DAB converters,this study proposed a multi-objective optimization scheme based on triple-phase-shift control,which was aimed at layered optimization of current stress,return power,and soft switching characteristics.Firsttly the minimum current stress obtained by the Lagrange Multiplier Method(LMM)combined with Karush-Kuhn-Tucker(KKT)condition under the soft switching condition.Taking the minimum current stress with a certain tolerance as a new constraint,LMM and Genetic Algorithm(GA)were used to solve the multi-constraint optimization of reflux power.This scheme can obtain the analytical solution of phase shift Angle of the full power segment,and the control is simple.Compared with the previous optimization control strategy,the optimization objective is increased,and the performance optimization of DAB converter is more comprehensive with a smaller reflux power on the basis of the minimum current stress.Finally,a simulation model and experimental platform were constructed for the DAB converter,and the software and hardware design of the experimental platform were introduced in detail.The characteristics of the DAB converter under different voltage conversion ratios and transmission powers using different control strategies were compared and analyzed,verifying the effectiveness of the proposed multi-objective optimization control strategy.