Design Of Wide Range Bidirectional Converter For Battery Energy Storage

In order to alleviate the energy crisis,combined with centralized and distributed generation system,the research and application of micro grid has become a hot spot.In the process of realizing the energy interaction between grid and battery,bidirectional converter plays a key role.The battery charging and discharging system needs to have the function of bidirectional energy flow to achieve a wide range of voltage input and output.In this paper,a 2.7kw wide range bidirectional AC/DC converter is designed for battery energy storage.According to the design requirements of the bi-directional converter,the overall scheme of the system is designed.The full bridge bi-directional AC/DC and CLLC bi-directional DC/DC are selected for cascading,and the DC bus is used for energy interaction to realize the decoupling of rectifier transformation and DC transformation functions,so as to facilitate the optimal design of wide range input and wide range output.Based on the principle analysis and circuit parameter design of bidirectional full bridge AC/DC,the corresponding small signal model is constructed,and the double closed-loop control loop is established to realize the stable regulation of forward rectifier and reverse inverter functions.For CLLC resonant converter,the forward and reverse working modes and gain characteristics are analyzed,the cavity parameters are optimized,the soft switch characteristics are realized,and the forward and reverse operation is ensured efficiently.The small signal modeling and closed-loop design are carried out by using the expansion function method to realize the stable adjustment and control of the converter.The bus voltage regulation control strategy is designed to complete the two-level integrated control,fully combining the advantages of two-level topology,to achieve wide range input and wide range output,and improve the system stabi lity.Combined with the traditional closed-loop control strategy and the optimal trajectory control strategy,a compound optimal trajectory control method is proposed to improve the transient characteristics of the whole system load shedding experiment.After theoretical research and simulation experiments,the overall design of the bi-directional converter is completed.Both the positive and negative directions can perform well.The control strategy optimizes the transient and steady-state performance of the converter.