Research On Bidirectional DC/DC Converter Based On LCLC Resonant Network

With the popularization of new energy technology,photovoltaic energy storage system is increasingly popularized.As the key link of photovoltaic-energy storage systems,bidirectional DC/DC converters have become more and more popular.Bidirectional DC /DC converters can be divided into isolated and non-isolated types.The non-isolated structure has the characteristics of small volume,low cost and simple control,which has attracted more and more attention.Combining with the isolation structure and principle of the soft-switching resonant converter,a non-isolated bidirectional converter topology with a LCLC resonant network is proposed based on the double half bridge structure in this paper.The MOSFETs in the circuit have the characteristics of ZVS-on and ZCS-off,and the half-bridge capacitor can naturally equalize voltage.The proposed structure has the advantages of small volume and low cost.In this paper,the working characteristics of the proposed structure are analyzed.First of all,combining the working principle of T type circuit,the proposed LCLC-T type structure is theoretically analyzed.Secondly,the circuit parameters are calculated in detail and PSIM software is used to verify the designed parameters.Thirdly,the constraint condit ions of soft switching state in the full load range of the circuit are analyzed,and the soft switching range of the proposed structure is determined.The small signal modeling of the LCLC convert is proposed by using Generalized State-Space Averaging(GSSA)method;Besides,the paper design the PI compensator circuit based on transfer function;What’s more,a compensation circuit based on analog and digital circuit system is designed according to the compensation function,which improves the dynamic response speed of the system.Finally,a LCLC prototype are built with Si C device according to the theoretical results.The performance of the prototype with a rated power of 1k W is tested.Experiment results show that the soft switch can be realized under full load and half load condition.The experimental results agree with the theoretical analysis.Under the rated condit ion,the effic iency of the prototype can reach 95.65% under the Boost mode and 96.04% under the Buck mode.