Structure Optimization Of Press Pack IGBT Based On Surrogate Model

Compared with the bonded IGBT,the press pack IGBT(Press pack IGBT,PPI)has the advantages of easy series connection,double-sided heat dissipation,and failure short-circuit mode,which has a good application prospect in HVDC flexible field.IGBT is the key component of HVDC flexible system,and its reliability is closely related to the reliability of HVDC flexible system.At present,most of the research on the reliability of PPI focuses on reliability modeling and adjusting the power loss of IGBT through control strategy to improve the reliability of IGBT.However,the research on improving the reliability by optimizing the structure of PPI has not attracted enough attention.Temperature is an important reason for the failure of PPI,and the temperature characteristic is closely related to the structure of the???IGBT.Therefore,the reliability of the device can be improved by optimizing the structure of the PPI.In this paper,taking toshiba's PPI as an example,the structure optimization method is adopted to reduce the unction temperature unevenness index and temperature fluctuation amplitude of IGBT,to improve the reliability of IGBT.to optimize the structure of the device to reduce the junction temperature unevenness and junction temperature swing,to improve the reliability of the device.To reduce the amount of calculation in the optimization process,the Kriging surrogate model is used instead of finite element simulation to improve the calculation efficiency.The main contents of this paper are as follows:(1)The contact thermal resistance of each component of the PPI is clarified,and a numerical analysis model for the temperature calculation of the PPI single-chip sub-module is established to calculate the temperature distribution,and the validity of the model is verified through experiments.A multi-chip PPI temperature calculation finite element model is established,and the influence of PPI shielding gas on temperature distribution is analyzed,and the junction temperature distribution characteristics of PPI are revealed.(2)Establish the thermal-mechanical coupling analysis model of the PPI single-chip sub-module,calculate the stress distribution of the single-chip sub-module under power cycle conditions,reveal the weak position of the PPI chip and calculate the life of the chip,and finally extract the influence of PPI fatigue The key factor of longevity provides support for the structural optimization of PPI.(3)Establish a single objective optimization algorithm based on the surrogate model,and prove the effectiveness of the optimization algorithm through mathematical examples.Finally,taking the reduction of the junction temperature unevenness index of the PPI as an example,the single objective optimization algorithm is used to adjust the thickness of each component of the PPI,and the optimization accuracy is improved by the mixed addition criterion.The simulation results show that the unevenness of junction temperature is reduced by 44.53% after optimization.(4)Establish a multiobjective optimization algorithm based on the surrogate model,and prove the effectiveness of the optimization algorithm through an example.Finally,to simultaneously reduce the junction temperature difference and junction temperature unevenness index of the PPI,a multiobjective optimization algorithm based on the proxy model is used to adjust the thickness of each component of the PPI.The simulation results show that the junction temperature difference and junction temperature unevenness of the optimized IGBT structure are better than the initial PPI structure.In this paper,the junction temperature characteristics of PPI are analyzed based on the finite element method,and the structure of PPI is optimized by using the surrogate model association intelligent optimization algorithm,which provides a reference for improving the reliability of PPI.