The Research Of Discrete Phase Shift Controlled Dual Active Bridge DC-DC Converter

With the vigorous development of society and economy,the burning of fossil fuels has brought serious air pollution problems.The development of renewable energy is an important measure to achieve the goal of " emission peak and carbon neutrality" in the medium and long term.Thus,the construction of a new power system with renewable energy as the main body is currently a research hotspot.In a new power system,the energy storage system plays an important role in promoting a high proportion of new energy consumption,ensuring the safe supply of power and improving the operating efficiency of the power system.The dual active bridge(DAB)DC-DC converter is an important intermediate link in the DC bus and energy storage system,and the improvement of its dynamic performance and efficiency is of great significance for the improvement of the performance of the entire system.Therefore,this paper aims to optimize the dynamic performance and efficiency of the DAB DC-DC converter.Firstly,in order to improve the dynamic response speed of the DAB converter,based on the traditional phase-shift control,the discretized idea of pulse train control is combined,the discrete-phase-shift(D-PS)controlled DAB converter is proposed and researched.Secondly,based on the single-phase-shift(SPS)control,the control principle and implementation method of discrete-single-phase-shit(D-SPS)control are researched,the main parameters and combination rule of control pulse groups of D-SPS control are analyzed,and the design process of D-SPS controller is introduced.The effectiveness of D-SPS control about improving dynamic performance is verified by simulation.Then,in order to improve the efficiency of the DAB converter,an efficiency optimization method of discrete-extended-phase-shit(D-EPS)control is proposed.Based on the D-EPS control,the backflow power and the peak-to-peak of inductor current are selected as optimization targets for the efficiency optimization method of D-EPS control.The phase-shift ratios of different control methods are analyzed and calculated,the efficiency of these control methods is analyzed and compared through experimental results,and the effectiveness of D-EPS control with peak-to-peak current optimization in improving converter efficiency is verified.At the same time,the dynamic performance of D-EPS control and EPS control are compared through experimental results,and the excellent dynamic performance of D-EPS control is verified.Finally,a D-EPS control method without dc-bias is proposed for the problem of magnetic saturation of DAB converter.In practice,the influence of the equivalent resistance is considered with the proposed control method,and the design principle and steps are introduced.Then,taking the D-EPS control without dc-bias as the research object,the energy iterative model and the discrete time model which based on the output voltage are established,the stability of the proposed method is proved from different perspectives,and multi-period state behaviors and boundary collision bifurcation behaviors are researched in this paper.