Research On Control Of Energy Storage System Based On Dual Active Bridge-Isolated Bidirectional DC-DC Controller

This master’s thesis focuses on the analysis and optimization of control strategies for isolated bidirectional full-bridge DC-DC converters.The research aims to improve the performance and efficiency of these converters through the design,development,and testing of various control strategies.The thesis consists of five chapters,each addressing a specific aspect of the problem.Chapter 1 introduces the dual active bridge-isolated bidirectional DC-DC converter as a key component in power electronics,facilitating energy transfer between two DC power sources with galvanic isolation.The importance of control in achieving optimal performance,efficiency,and system stability is emphasized.The complex behavior and nonlinear characteristics of the converter make designing an efficient control strategy challenging.Consequently,this research focuses on exploring and developing advanced control techniques for energy storage systems based on the dual active bridge-isolated bidirectional DC-DC converter.Chapter 2 delves into the analysis of the Single Phase Shift(SPS)control principle.It examines the on-off and off-states of switches and diodes in each stage and establishes mathematical expressions for inductor current,transmission power,backflow power,and inductor current peak value.The relationship between these variables and phase shift is analyzed,demonstrating that while backflow power reduction is possible,elimination is not.Increasing the voltage matching value,k,close to 1 leads to decreased backflow power,inductor current peak value,converter losses,and higher transmission efficiency.The theoretical analysis is validated through simulation.Chapter 3 focuses on Double Phase Shift(DPS)control.It analyzes switch states,deduces expressions for inductor current,and primary and secondary side voltages of the transformer in each stage.Mathematical expressions for transmission power and backflow power are obtained.The chapter explores minimum backflow power control methods based on a single closed loop and subsection minimum backflow power.Simulation verification demonstrates the effectiveness of both methods in reducing backflow power and stabilizing the output voltage.The single closed loop method exhibits a smaller inductor current peak value and higher system transmission energy efficiency compared to DPS control.Chapter 4 examines Triple Phase Shift(TPS)control.The principle of dividing one cycle into eight stages is analyzed,considering switch tube conduction,turn-off,current magnitude,and direction in each stage.Mathematical models for transmission power,output current,and backflow power are established under steady-state conditions.An optimization strategy for backflow power is derived based on the mathematical model,and a corresponding simulation model is built.A comparison of isolated bidirectional full-bridge DC-DC converters under single-phase,double-phase,and triple-phase control reveals that while single-phase control is simple,it results in higher backflow power and inductor current.Double-phase and triple-phase control achieve almost zero backflow power,with triple-phase control offering the highest transmission efficiency despite its more complex control principle.Chapter 5 presents the experimental principles and prototype construction of the isolated bidirectional full-bridge DC-DC converter.Parameter indicators,switch device selection,and design of the high-frequency transformer are discussed.Detailed descriptions of the main circuit,drive circuit,and associated sub-circuits are provided,including isolation,power supply,and drive sub-circuit design.The phase-shift program with a dead zone is programmed,and the experimental prototype undergoes initial testing.The control circuit,drive circuit,and main circuit are debugged step by step,with provided experimental waveforms.The integrated and tested prototype achieves an output power of 2.8 k W.Experimental waveforms under the three control modes validate the theoretical analysis.Overall,this research contributes to the advancement of power electronics and the development of more efficient and reliable energy storage systems by analyzing and optimizing control strategies for isolated bidirectional full-bridge DC-DC converters.