| Press-pack IGBT(PPI)is widely used in flexible DC transmission converter valves and is key components in flexible DC transmission equipment due to its advantages of compact structure,short circuit failure,higher reliability and higher power density.PPI is composed of multiple sub-modules in parallel connection and has the characteristics of complicated internal structure,strong coupling of multiphysics field,and multiple time scales.The research about device reliability usually take the thermal resistance,average junction based on the end parameters,and the turn-on voltage to describe the device's aging state,which is hard to present the coupling relationship between the internal stress and the aging state.Focusing on this problem,this paper studies the current distribution characteristics under the coupling of the internal temperature and pressure distribution of the device.Based on the coupling of electro-thermal and mechanics,the current distribution calculation model of the multi-chip parallel device is established.Based on that,a state monitoring model for multi-chip parallel PPI devices was proposed.The main content of this paper includes the following aspects:(1)The causes of the uneven current in the multi-chip parallel PPI is analyzed.It built an experimental platform for measuring the difference of current distribution under different temperature imbalance and different pressure imbalance,which is the preparation for exploring the characteristic of current distribution under different temperature imbalance and different pressure imbalance.By measuring and comparing the static and dynamic characteristics of different chips,the chips for subsequent experiments were selected.(2)The current distribution in the multi-chips parallel PPI under different temperature imbalance and pressure imbalance is obtained through experiments.And,the law of the difference in current distribution with temperature difference and pressure difference is analyzed.First,for the problem of current imbalance caused by the uneven temperature distribution,the trend of current imbalance with the degree of uneven temperature was analyzed in detail by experiments,which found there is a linear relationship between the degree of current imbalance and the temperature imbalance.Then,the characteristic of unbalance current distribution under different pressure distribution was analyzed,which found that the degree of current imbalance becomes worse with the increase of pressure difference when the reference pressure is selected.Finally,the characteristic of the current imbalance under the coupling effect of temperature and pressure was analyzed,which found the current imbalance level go worse when the difference of temperature rises under various pressure distribution.(3)To analyze the characteristics of temperature distribution and current distribution under different aging conditions and prepare for health state monitor,a multi-physics coupling model of the 3300V/1500 A multi-chip PPI device was established.And,its validity of the model was verified,which provides tools for analyzing the characteristics of electrical and thermal parameters under different aging conditions.(4)The models for current distribution calculation based on temperature distribution or pressure distribution are constructed separately.Then,a current distribution model for current distribution based on different temperature distributions and different pressure distributions was built by combining the two models constructed before.The validity of the model is verified.Finally,with the help of the finite element simulation,the variation of the electrical and thermal parameters of the device under different aging degree are analyzed.And,the group of parameters that can be used to reflect the health status of the device is selected.A health condition monitoring model based on the characteristics of electro-thermal distribution was proposed. |
PDF Full Text Request