Research On Wide Gain Bidirectional DC/DC Isolation Converter For Electric Vehicle Charging Pile

With the rapid development of country’s economy,the shortage of resources and the deterioration of environment are becoming increasingly serious.Green environmental protection has gradually become a focus of attention.The technology of new energy electric vehicles has gradually matured,and it has become a general trend to gradually replace fueled vehicles.Among them,the isolated bidirectional DC/DC converter is widely used in the V2 G field as the connection bridge between the high-voltage DC bus and the electric vehicle.In actual working conditions,when the DC bus charges the battery through the bidirectional DC/DC converter,the battery side needs to have a wide range of voltage gain.When the battery discharges the DC bus in reverse,the bus side must have a stable DC voltage output.Participate in peak-shaving and valley-filling of the grid voltage through DC/AC converters,alleviating the intermittency and volatility of new energy power generation.In this paper,a three-level bidirectional full-bridge multi-resonant converter is proposed in view of the demand for bidirectional DC converters in the field of V2 G.The work has the following aspects:First,introduces several basic topologies used in charging piles at domestically and internationally,and then according to the current research status,the three-level hybrid clamp structure is combined with the multi-resonant network after adding auxiliary inductors.Proposed a three-level bidirectional full-bridge multi-resonant DC/DC converter suitable for high-voltage levels and a wide range of voltage gain.The gain range is significantly improved,and the problem of wide voltage range required for charging is effectively solved by single-stage conversion.The converter can realize ZVS turn-on of the full-range switch tube,and the resonant cavity structure is left and right symmetrical,the improved synchronous frequency conversion control strategy can meet the technical requirements of electric vehicle V2 G.Then,according to the relationship between the working frequency of the converter and resonant frequency of the resonant cavity,the forward and reverse operation states of the converter are divided into two modes respectively,and their working processes are analyzed.The relationship between the gain and resonant frequency of the multi-resonant converter and the parameters of the resonant network is deduced,and the characteristics of the converter can use the fundamental current and the third harmonic for power transmission simultaneously are obtained.Finally,using the 2k W experimental platform as an example,according to the performance index of the converter,hardware and software design was carried out.In the PSIM software,forward and reverse open-loop and closed-loop simulations of the designed converter were performed,and the experimental platform was used for experimental verification.The converter can achieve twice the voltage gain in the frequency range of72 k Hz-125 k Hz when it is running in the forward direction.Compared with the LLC resonant converter,it is obviously improved,and the rationality of the designed three-level bidirectional full-bridge multi-resonant converter is verified by experiments,the rationality of the designed three-level bidirectional full-bridge multi-resonant converter is verified.