Research On Full Bridge Isolated Bidirectional Dc-Dc Converter

Based on the bidirectional DC-DC converter applied in the field of new energy and battery energy storage system,this paper mainly focuses on three typical topologies,including Voltage-Fed DAB converter,LC series resonant DAB converter and multi-port bidirectional DC-DC converter.Working principle,control strategy and power transmission characteristics of the converter has been deeply analyzed.Firstly,the working principle of Voltage-Fed DAB converter under the phase-shift control strategy is analyzed by establishing the equivalent circuit model.The power transfer characteristics of the converter are deduced in detail according to the analysis of the working modes in one switching cycle,the relationship between transmission power,backflow power and phase shift duty cycle can also be obatained.According to the definition of the soft switching,the condition that switches in the primary and secondary full-bridge converter achieve zero voltage turn-on is deduced,and the situations of the soft switching under different voltage ratio are also analyzed.The approximate equivalent circuit model of LC series resonant DAB converter is estatlished under the fundamental wave analysis method,and the power transfer expression of the converter is deduced.The working principle,power transmission characteristics,the realization conditions of the soft switching and three types of soft switching mode under the single phase-shifting control strategy are elaborated in detail,and the peak resonant current is deduced to facilitate the design of the resonant cavity.Compared with the non-resonant DAB converter,LC series resonant DAB converter can also realize soft switching,while the inductance current is closer to the sine wave,which makes the turn-off current of the switches smaller,reduce the turn-off loss,and can improve the system electromagnetic compatibility features as well.The working principle of the three-port bi-directional DC-DC converter topology is analyzed.The power transmission characteristics of the three-port converter are deduced through the equivalent circuit of Y-type and A-type.In order to realize the power decoupling control among the ports,the circuit topology and control strategy of multi-port bidirectional DC-DC converter are proposed.Using the Y-type equivalent circuit,the conditions for achieving independent control of each port in the system are deduced through theoretical analysis.Aiming at the application of multi-port bidirectional DC-DC converter in the new battery energy storage system,the independent control of the difference current of each series battery module is adopted to realize the partial power control of the system and improve the energy utilization efficiency of the energy storage system.Based on the working principle of converter and parameter design method,the Matlab/Simulink is used to verify the validity of the working princple,at the same time,hardware experimental platforms of three types of DC-DC converter topology has been built.The experimental waveforms under different given currents and voltage conversion ratio are deeply analyzed,the experimental results verify the correctness and feasibility of the proposed circuit topology and its control strategy.