Bi-directional DC/DC Converter Control Strategy Optimization And Modular Research

At present,The bidirectional full-bridge DC/DC converters used in distributed generation systems produce large backflow power and current stress in the traditional single phase shift control,resulting in increased losses.In this dissertation,by defining the backflow power,phase shift ratio and the relationship between the input voltage and the output voltage,a backflow power optimization control strategy with minimum backflow power is established.By the expanded modular technology,the optimized single-module circuit can be applied to a wider demand conditions in the environment.In this dissertation,the working principle of DAB(Dual Active Bridge)Converter under traditional phase shift control mode was first analyzed,and then the relationship between energy flow direction and phase shift angle was studied,based on what the backflow power problem generated by energy flow was discussed,especially the greater influence produced by the unmatch of input and output voltage amplitude.Discussing its implementation of soft-switching conditions,and build its small signal modeling,and finally through simulation verification.Aiming the problem that the backflow power is too large and the soft-switch range is too small,a dual-phase-shifting control model was proposed and optimized by the analysis of its working principle.Under the same transmission power,the smallest backflow power was solved and the optimization effect is verified by a simulation model.For the simulation results,the main parameters of the circuit are given,and the hardware part of the main circuit is designed,including the sampling circuit,the driving circuit and the protection circuit.The main circuit is controlled by DSP and the software part is designed,including the main program,Program,PID algorithm and so on.Finally,a dual-module ISOP connected DAB circuit was built.The backflow power generated by traditional phase shift control,the normal and optimized doal-phase-shifting control were compared,and the validity and feasibility was verified by comparing with the principle analysis.The output of the single module and the dual module are tested respectively to verify the stability.