Design Of 6.6kW Charger For New Energy Electric Vehicles

With the rapid development of new energy electric vehicles,the charger as one of the key components of new energy electric vehicles has been gradually replaced by high-power chargers from the early low-power 1.2kW/1.3kW.Based on this,this paper mainly studies and The topology circuit structure and control strategy of a 6.6kW charger are designed to make it stable,reliable,fast and safe for charging electric vehicles.Through the reading of a large number of references and market research,the differences in function,performance and technical indicators of the 6.6kW charger and the low-power charger are analyzed,so that a 6.6kW new energy electric vehicle charger is designed.The theory,simulation analysis and experimental verification of the main circuit topology and control method are carried out.The on-board charger studied in this paper adopts a dual-end structure,that is,the front-end adopts an AC-DC structure,and the back-end adopts a DC-DC structure.In the front-end AC/DC topology,in order to meet the requirements of the grid side,as well as the problems of large power loss and low charging efficiency on the traditional Boost-PFC rectifier bridge,this paper analyzes and compares the traditional rectifier topology circuit structure.Using the topology structure of the front-end rectifier circuit totem bridgeless PFC and interleaved parallel technology,the working principle and control method of the topology structure are analyzed in detail.For the reverse recovery problem of the body diode during the operation of the topology circuit,the theory It is analyzed that the power tube current is controlled by turning on or off,which solves the problem of reverse recovery of the body diode and realizes synchronous rectification.Finally,the main circuit parameters are designed,and the average current control is used to simulate the main circuit topology.The simulation results show that the topology has high power factor,low total harmonic content,low current stress on the power device,and low ripple coefficient.Etc.In the back-end DC/DC topology,in order to meet the requirements of battery charging,and the main circuit topology has a wide range of voltage regulation function,low power loss,high power density and other requirements,this paper uses a half-bridge LLC resonant converter topology.The working principle and characteristics of the topology are analyzed in detail,and the FHA equivalent model is established using Fundamental Harmonic Analysis(FHA).Aiming at the virtual gain brought by the secondary leakage of the transformer,this paper corrects the DC voltage gain expression and optimizes the design of the main circuit parameters.At the same time,for the problem of slow dynamic response speed of LLC resonant converter controlled by traditional voltage mode,a charging current control strategy with fast dynamic response speed is adopted.This control strategy introduces a resonant current signal in the control loop and the current feedback module is added to improve the dynamic response speed,analyzes the control method in detail,and designs the control loop parameters.Finally,the correctness of the theory is verified through simulation.Finally,the back-end LLC resonant converter is verified by experiments.The experimental results show that the charging current control strategy can achieve the functions of zero voltage turn-on(ZVS)and zero current turn-off(ZCS).At the same time,its input voltage dynamic response speed is nearly 44% faster than the voltage mode control strategy,and the voltage overshoot is reduced by 50%;the load dynamic response speed is 44% faster than the voltage mode control strategy,and the voltage drop is reduced by 57%.It can be seen that the charging current control strategy has a faster dynamic response speed,which verifies the theoretical analysis in this paper.