Research On Three Port Bi-directional DC/DC Converter And Efficiency Optimization Strategy For Hybrid Energy Storage System

With the development of science and technology,people pay more and more attention to the issue of energy and environment.It has become a global consensus to vigorously develop renewable energy such as wind energy and solar energy.Nowadays,many countries are committed to the construction of the global energy internet,and the energy router is the key node equipment in the energy internet.The key of energy router to achieve energy allocation is the hybrid energy storage system,which plays a role in peak and valley filling.Therefore,it is important to study the topology,control strategies and efficiency optimization strategies of the hybrid energy storage system.Based on the background of home energy router,this paper designs and improves the topology of power converter for hybrid energy storage system,and designs a control method to achieve closed-loop control for the problems in the work of energy storage system,which improves the efficiency of the system.Firstly,according to the requirements of home energy router applications,the power converter of hybrid storage system is studied.An interleaved parallel three-port bidirectional DC/DC power converter is studied,and a simplified equivalent model is established.At the same time,the phase shift control mode is determined and the power transmission is quantitatively calculated.The working principle and process of the low voltage side-interleaved parallel full-bridge circuit are analyzed in detail,and the current direction in each working time is determined,which lays a theoretical basis for hardware design.The topology is validated by simulation.Secondly,a three port power converter based on coupled inductor is studied to optimize the performance and power density of the topology,The use of coupling inductance instead of staggered shunt inductance reduces the volume of inductive elements and increases the power density of the system.The influence of inductive coupling state and coupling coefficient on the circuit is studied.The staggered shunt coupled full bridge circuit is modeled,and the influence of equivalent inductance at each time on the dynamic response rate of the circuit and input current ripple is analyzed.Then,an efficiency optimization control strategy is studied to solve the problem that the voltage of supercapacitor will affect the system efficiency with the change of charging and discharging.Based on the principle that the boost function of the low voltage side of the topology used in this paper can control the voltage square wave of the transformer port,an optimal control strategy is designed for the system.It achieves power decoupling and power transmission between ports,stable input of DC bus voltage,current stress of switch tube and optimization of system efficiency.Finally,the control strategy is verified by simulation.Finally,a hardware test platform for the staggered parallel-coupled threeport power converter of hybrid storage system is established.The working principle,working characteristics and efficiency optimization control strategies of the topology proposed in this paper are validated through hardware experiments.