Performance Analysis And Optimized Design Of Interleaved Boost Integrated Bidirectional CLLLC Resonant Converter

As a form of power grid which connected to distributed power sourve,the DC microgrid has attracted much attention for high reliability,simple control and low transmission loss.In DC micro-grid,as an interface equipment to realize energy interaction between energy storage system and high voltage dc bus,the isolated bidirectional DC-DC converter has become a research hotspot at the same time.In order to meet the basic requirements for wide input voltage range,low input current ripple and changing the direction of power transmission smoothly in DC micro-grid,a novel interleaved boost integrated bidirectional CLLLC(primary resonant capacitor-primary resonant inductor-magnetizing inductorsecondary resonant inductor-secondary resonant capacitor)resonant converter(IBIB-CLLLC resonant converter)is proposed in this paper,according to the application of isolated bidirectional DC-DC converter in DC micro-grid,the basic principle,performance analysis and optimized design of proposed converter are researched deeply.Futhermore,the widebandgap semiconductor device GaN-HEMT is used for high efficiency energy conversion.Firstly,this paper introduces the principle of proposed IBIB-CLLLC resonant converter,and establishes the corresponding differential equations based on its different operating modes in different times and derives the time domain mathematical expressions of each electrical quantity,further,the state trajectories of resonant tank under different duty cycle D are ploted by simulation and thereotical calculation respectively to verify the correctness of the theoretical derivation,then,the principle of the proposed converter is verified by experimentats.Secondly,for further research of the performance of the IBIB-CLLLC resonant converter,according to the time domain mathematical expressions of each electrical quantity,the gain characteristic,input current ripple characteristic and the range of soft-switching are analyzed in detail,hence,relevant mathematical models are derived.On this basis,a design method applied to the IBIB-CLLLC resonant converter is presented and a experimental proptotype based on GaN-HEMT with 96.6% peak efficiency is built as well.Moreover,the experimental results verify the correctness of theoretical analysis on the performance of proposed converter and the feasiblility of proposed design method.Since the introduction of input inductor L in proposed converter brings additional volume and loss,in order to improve the power density and reduce the loss of magnetic element,the analysis and design of coupling inductor are studied in this paper.By comparison,the way of negative coupling mode is selected owing to its lower loss,and the equivalent inductance under different operating modes of proposed converter with negative coupled inductor are obtained.Furthermore,the current ripple characteristics,soft-switching characteristics of IBIB-CLLLC resonant converter with negative coupled inductor are analyzed,and the relationship between core loss,core volume and coupling coefficiect ? is concluded as well.Then,comprehensively considering the soft-switching condition,core loss,power density and other factors,an effectively design guide of coupled inductor applied to the IBIB-CLLLC resonant converter is presented in this paper.Finally,according to the results of simulations and experiments,the feasibility and validity of the design guide of coupled inductor are verified.Besides,the introduction of coupling inductor is really helpful for reducing the volume and loss of input inductor and improve power density and efficiency of the proposed converter without influencing its inherent advantages.Above all,it is obviously the proposed IBIB-CLLLC resonant converter have wide volde gain,low input current ripple and can smoothly regulate the amplitude and direction of transferred power.In addition,compared with tranditional two-stage bidirectional resonant converters,it reduces the number of switches and switching losses,and the introduction of GaN-HEMT and corresponding optimized design method ensure the proposed converter with high efficieny,high power density.In a word,the proposed IBIB-CLLLC resonant converter is suitable for DC micro-gird with energy storage system.