Study On EMI Filter Of High Power Charging Module Based On AC-LINK Technology

With the intensification of the global environmental pollution and fossil energy crisis,the demand of energy-saving and emission reduction is increasingly grown.As traffic tools with no exhaust pollution and low energy consumption,new energy electric vehicles obtain great opportunities for development,greatly promoting charging power technology continuing to progress,which is a basic support equipment.At present,various types of electric vehicle charging power are actively developed both at home and abroad.High power DC charging module can achieve fast charging and is becoming the mainstream direction and research hotspot.As a high power energy conversion device,charging module based on AC-link technology possess complex internal structure and control method,and its semiconductor power devices' high dv/dt,di/dt can cause serious conducted interference.EMI filter is a commonly used measure to suppress the switching power supply conducted interference,in this paper,the EMI filter of high power charging module based on AC-link technology is studied.The research status of switching power supply EMI filter and conducted interference at home and abroad is introduced,and the purpose and significance of this paper are briefly described in this thesis.At the same time,the main work and the arrangement of this paper are explained.The topology,the basic working principle and the control strategy of high power charging module based on AC-link technology are introduced,and the mechanism of conducted interference of charging module,the interference sources and propagation path of the common mode and differential mode interference are analyzed.Secondly,the research on the conducted interference test of high power charging module is carried out.The conducted interference of the charging module is tested by the current probe method,and the common mode interference and differential mode interference are separated.The general requirements of the conducted interference test of the charging module are given and the single-phase Artificial Mains Network provided by CISPR,which is suitable for high current situation,is extended to three-phase.The charging module conducted interference test program based on the current probe method is designed,giving a detailed result processing method.In this way,the conducted interference of the charging module is tested,and the common mode interference and differential mode interference spectrum are obtained by using three-phase common mode and differential model scalar separation method.Through the comparison with the standard limit,the disturbance superscalar and the electromagnetic compatibility rectification direction are determined.Then,the improved design of three-phase EMI filter is studied.Based on the three-phase EMI filter insertion loss simulation analysis method,the three-phase EMI filter of the charging module under the condition of high current is optimized.Based on the impedance amplitude curves provided by the manufacturer,the high frequency equivalent circuit of capacitors is established.The common mode inductance,leakage inductance and the differential mode inductance impedance amplitude curves are tested by the impedance analyzer,the corresponding high frequency equivalent circuit are established.In addition,the parasitic parameters of the PCB traces are extracted by the electromagnetic analysis software.According to the EMI filter insertion loss test circuit provided by CISPR 17,the common mode and differential mode simulation model are set up to analyze the insertion loss.Based on the simulation results and the charge module conducted interference test results,the original EMI filter design is optimized.The improved filter and the charging module using the filter are tested and verified.Finally,a simulation method of conducted disturbance of charging module which adapts to complex control mode and topology is researched,the insertion loss of the EMI filter used in the charging module is analyzed.The conducted interference circuit analysis model of the charging module including the EMI filter,the bus equivalent circuit model,the IGBT circuit model,the high frequency equivalent circuit model of the transformer and so on is established in the system simulation software,the control algorithm model is set up in Simulink,the simulation model of charging module conducted interference is obtained by joint modeling.The influence of EMC key elements or parameters such as bus parasitic parameters,power device parasitic capacitance and driving signal rise time on the conducted interference of the charging module is simulated and discussed.The insertion loss of the three-phase EMI filter in the charging module is simulated by joint modeling,and compared with the insertion loss obtained when the filter is separately modeled.The joint modeling provides a reference method for simulating the effect of some EMC design or parameters on the conducted interference of the charging module in the design stage.