Hybrid Control Strategy Of Bidirectional Full-Bridge CLLC Resonant Converter

The lack of traditional energy sources and the deteriorating domestic ecological environment make new energy research urgent.New energy technologies represented by wind energy,solar energy and biomass energy are becoming the main force in the development of energy technology,and electric power plays an important role.Electronic technology has also developed rapidly.How to eliminate switching loss,reduce electromagnetic interference,and improve energy conversion efficiency have always been the focus of the power electronics industry.The two-way DC/DC converter,which is the key link of energy conversion,has naturally become a breakthrough point to solve these problems.Efficient high frequency bidirectional DC/DC converters will become important.The traditional LLC resonant converter is a representative of the bidirectional DC/DC converter,and its technology has become increasingly mature.On the basis of inheriting the advantages of the traditional LLC resonant converter,the CLLC resonant converter adds an additional capacitor to the right side of the resonant network section than the conventional LLC resonant converter,which makes it positive in the forward direction.The DC gain at the resonant frequency point is less than one,and the DC gain at the reverse second resonant frequency point is greater than one in the reverse run.Make it more suitable for use in forward buck,reverse boost working environments.However,the process and depth of the analysis of its characteristics are not sufficient.The paper supplements its corresponding characteristics.In order to adapt to the wide range of input voltage and more applications of new energy,combined with the characteristics of variable frequency control and phase shift control,a hybrid control strategy is used to carry out experimental research,which provides a control strategy of reference plan for CLLC resonant converter application research.Firstly,the fundamental wave analysis method is used to obtain the DC gain and the first and second resonance frequencies of the resonant converter in forward and reverse running.The full-bridge CLLC resonant converter forward frequency conversion isanalyzed.The working process of running and forward phase shifting.Then the CLLC resonant converter is compared with the traditional LLC resonant converter,the difference between the two resonant networks is described,and the role of the extra capacitor on the low-voltage side of the CLLC in the operation of the CLLC converter is analyzed.It is clear that the work area of CLLC converter is stable.Secondly,the rationality analysis of the hybrid control strategy is carried out.The forward frequency conversion open loop operation,reverse frequency conversion open loop operation and forward phase shift open loop operation of the CLLC resonant converter are simulated,and the feasibility and correctness of the hybrid control strategy are verified.According to the experimental conditions,the specific technical indicators of the research is determined,and the parameters of the selected main circuit is designed and calculated.Finally,the control system hardware and system software of CLLC resonant converter are analyzed and designed.On this basis,the experimental platform is built and the converter is tested.The preliminary verification results are obtained.The experimental results are consistent with the theoretical analysis.The rationality of the experimental parameter design and the feasibility of the hybrid control strategy are verified.