Dual Buck Bidirectional Inverter Based On Digital Control

With the increasing emphasis on environmental protection and sustainable development,renewable energy,represented by distributed energy,has been greatly developed.The large amount of access of distributed energy resources will have a great impact on the power grid.In order to deal with the influence of the distributed energy sources,many scholars have put forward the use of DC micro grid system to accept a variety of distributed energy sources.In addition,some scholars put forward the electric vehicle battery as the energy storage device of vehicle-to-grid(V2G)system which involved in the regulation of the grid by charging and discharging mode,can also stabilize the impact of distributed energy access.Whether DC micro grid system or V2G system,the bidirectional DC/AC converter is one of the most important aspects.Bidirectional DC/AC converter is usually the traditional full bridge structure which has shoot-through problem in bridge legs.And the inductor current flows through the body-diode,which have problem of serious loss and reverse recovery.This leads to the reduction of the reliability and efficiency of the bidirectional DC/AC converter.Dual Buck inverter(DBI)receives more and more scholars' attention due to the elimination the of the shoot-through problem and optimization of the freewheeling diode.This paper presents a Dual Buck bidirectional DC/AC converter which have the advantages of Dual Buck inverter.Through the analysis and comparison of the existing Dual Buck inverter topology,a full bridge grid connected dual Buck inverter is selected for bidirectional research,and the simulation results verify the feasibility of the proposed topology.However,this topology has a serious problem of body-diode operation and electromagnetic interference,so this paper proposes an improved bidirectional DC/AC converter topology based on this topology,that is,the Dual Buck bidirectional inverter.By adding two diodes,this topology reduces common mode interference and changes the mode of operation of the rectifier so that the path of the current through the diode is eliminated.Then,this paper analyzes the principle of the dual Buck bidirectional inverter,and the analysis shows that the topology has less electromagnetic interference.The model and the digital controller of grid connected inverter and rectifier PFC mode is designed,and the suitable control algorithm is selected according to the existing control strategy of bidirectional DC/AC converter.In the rectifier PFC mode,voltage loop using PI controller is designed.Among them,the current loop of the grid connected inverter is verified by the PI control algorithm and the predictive current algorithm respectively,and the experimental results show that the predictive current algorithm has a better steady-state performance.The voltage loop of the rectifier PFC mode is used for the PI controller with fast dynamic response.Then,the input current harmonics are analyzed,and the three harmonic suppression algorithm is proposed to suppress the harmonic currents.The simulation results show that the proposed control scheme makes the control system has fast dynamic response and good steady-state performance.Finally,a prototype based on TMS320F28069 is designed to verify the feasibility of the Dual Buck bidirectional inverter and the effectiveness of the control strategy.