Research On Distributed Energy Storage Converter Based On Bidirectional Zero Current Switching

With the development of distributed DC microgrids,the importance of energy storage systems has become more and more prominent.As the key link connecting the microgrid DC bus and energy storage system,improving the efficiency of bidirectional DC-DC converter has important research significance.Under the application background of DC microgrid low-voltage energy storage system,this thesis proposes a distributed energy storage converter based on bidirectional zero current switching(Zero Current Switching,ZCS),which has good soft switching characteristics and maintain zero current switching characteristics on the side of low-voltage and large-current during bidirectional operation.Therefore,the switching loss under bidirectional operation can be reduced,and the operating efficiency of the converter can be improved.Firstly,the working principle and characteristics of traditional dual-active bridge(DAB)converter and bidirectional LLC resonant converter are briefly introduced.The working principle and operation mode of the bidirectional zero-current switching DC-DC energy storage converter are deduced and explained in detail.And its power transmission characteristics,voltage gain characteristics and soft switching characteristics are analyzed.The switching device losses are compared with DAB converter and bidirectional LLC resonant converter,and a simulation model is built for verification.Secondly,based on the operating characteristics of the bidirectional zero-current switching DC-DC converter,the design and selection methods of hardware parameters are deduced from the perspective of current peak value and switching tube loss optimization.The converter was improved to further reduce the loss,and the effectiveness of the improved measures was verified in the simulation.On the basis of the control method proposed in this dissertation,two different improved control strategies are proposed,their characteristics and working principles are analyzed,and their correctness and effectiveness are verified by simulation.Then,for the high-voltage application scenarios in the DC microgrid,a multi-winding converter solution based on the bidirectional zero-current switching DC-DC converter is proposed,and its working principle is explained in detail.The problem of capacitor voltage equalization in series modules of this converter is analyzed.The application advantages of the multi-winding converter are analyzed by comparing with the scheme of directly using SiC MOSFET.The working principle of the three-winding converter and the effectiveness of the voltage equalization control are verified by simulation.Finally,according to the principle of the above analysis,set up the experimental platform,and the hardware and software were designed for the bidirectional zero-current switching DC-DC converter and the three-winding converter.And the main component parameters of the circuit were determined.The feasibility and effectiveness of the proposed converter are verified through experiments,and the dynamic response performance of the converter is tested.