Statistical Characteristics Of IGBT Chip’s Parameters And Their Influence On Current Sharing Of Parallel Chips

HVDC(High Voltage Direct Current)based on power electronic device has become an important development direction of the power grid in future.Press pack IGBT has gradually replaced traditional power electronic devices because of its characteristics of double-sided heat dissipation and short circuit at failure.However,the flow capacity of single IGBT chip can’t meet the requirements of the power grid,so the multi-chip parallel technology of Press pack IGBT chip has become one of the cores of the design of high power device.The research of ABB,Infineon,Siemens,Semikron and other companies shows that the current sharing of parallel IGBT chips is mainly affected by chip parameters,bus circuit,operating conditions and other factors.In this paper,the chip parameters with significant influence are mainly studied.Firstly,the statistical characteristics of the common dynamic and static parameters of press pack IGBT chips are revealed,and then the normal distribution model of single parameter is verified in sequence by using the P-P diagram.At the same time,the bivariate correlation is verified by using the Pearson correlation coefficient.Besides,the mediation analysis model and the neural network model are built to analyze the multivariable interaction between the chip parameters.Secondly,based on the operating waveform of single chip.this paper elaborates the rule of collector current variation during turn-on,steady and turn-off stages of single chip,reveals the quantitative influence rule of parameter dispersion of parallel IGBT chips on current distribution through statistical analysis.Then,the calculation formula of transconductance integral method for transient current during turn-on,that of saturation tube voltage drop shunt method for steady current and the linear fitting formula of the redistribution difference of transient current during turn-off are proposed.At the same time,the validity of the conclusions is verified by double-pulse experiments of two parallel chips,and then the screening strategies for parallel chips are proposed.Finally.the influence of temperature.pressure and current level on chip parameters and the rule of current sharing is analyzed in sequence.and the bimodal phenomenon waveform of turn-off at large current level is obtained.Additionally,two types of current competition of current waveform during turn-off are defined.the screening strategy for the changes in external conditions is proposed.Also,the screening strategy considering the turn-on,steady and turn-off process synthetically is given.The relevant research results of this paper can provide theoretical support for the screening of the internal chips in the press pack IGBT device.