| Press-pack IGBT is widely applied in high voltage and large capacity flexible DC converter valve because of failure short circuit.However,the internal structure of press-pack IGBT is complex and material properties are different.The conventional methods based on data statistics and physical failure model are difficult to accurately analyze the influence of internal structure and packaging material of press-pack IGBT,so accurate evaluation of the reliability of press-pack IGBT has important practical significance.A typical topology MMC for a large capacity flexible DC transmission system is used as an example to carry out the study of multiple physical field modeling and reliability evaluation methods for press-pack IGBT.The main contents of this paper are as follows:(1)In order to study the reliability of press-pack IGBT under multiple stresses,a single chip coupled model multi physical field is established.First,based on actual structure of the press-pack IGBT,a multi physical field simulation model of 3300V/50 A press-pack IGBT is built.Secondly,the influence of different conduction current,ambient temperature and external pressure on device are simulated and analyzed.Finally,power cycle experiment platform of press-pack IGBT is built to verify the validity of the finite element model,which lays the foundation for reliability evaluation of press-pack IGBT.(2)For conventional reliability methods,the failure rate of different packaging materials inside press-pack IGBT is not considered,so a reliability calculation method of press-pack IGBT considering fatigue life of internal materials is proposed based on multiple physical fields coupling failure mechanism.First,mechanism process of press-pack IGBT under fretting wear failure mode is studied.Secondly,reliability model of 3300V/50 A single chip press-pack IGBT is established,and weak parts of the device are analyzed.Finally,validity of the reliability model of single chip IGBT is verified by the power cycle aging test,and the life is obtained under the action of different stresses,such as different temperatures and pressures.(3)The reliability evaluation method of multi-chip IGBT based on multi physical field is proposed in order to accurately analyze the influence of the internal multi-chip interaction on IGBT.First,based on two actual structures of multi-chip press-pack IGBT,the multi physical field simulation model of the 3300V/1500 A device is established.Secondly,the reliability model of multi-chip press-pack IGBT is carried out.Finally,the inside IGBT chip failure rate of device is analyzed,and the reliabilities of two structures are compared and analyzed.(4)Existing reliability evaluation of MMC converter valve modules is difficult to calculate the effect of the system operating conditions on device failure,a reliability evaluation method of MMC converter valve modules based on fault tree analysis is presented.First,the MMC converter valve circuit model is built,current stress of devices are simulated and analyzed.Secondly,considering the influence of operating conditions on the failure rate of press-pack IGBT internal components,the fault tree model of MMC converter valve modules is established.Finally,the failure rate of IGBT is calculated,and the weak parts of MMC converter valve are identified.The research results of this paper lay a theoretical foundation for the reliability design of high-power press-pack IGBT devices,and provide technical support for the reliability evaluation of the large capacity flexible direct current converter valve module. |
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