Multi-Physics And Multi-Time Scale Modeling And Solution Methodology Of An Insulated Gate Bipolar Transistor Based Power Electronics System

Power electronic device or system plays an essential role in efficient energy conversion and utilization.Moreover,large-capacity power electronic device or system is fundamental in developing national key equipments in China.Insulated Gate Bipolar Transistor(IGBTs)is the dominant component in modem power electronics systems.Accurate analysis and calculation of the(dynamic)performance of IGBTs are the precondition to provide theoretical and technical guidelines for an IGBT design.Therefore,in order to enhance the designing and manufacturing level of an IGBT and the whole power electronic product to strength its competitiveness in the international market,it is urgent to study and develop the multi-physics model and solution methodology of IGBTs.The multi-physics field of IGBTs and the related power electronics systems is extremely complex.First,the turn-on and turn-off transients of an IGBT is a very small time scale current field governed by the carrier ambipolar diflfusion equation(ADE)and the law of charge conservation.Second,the displacement current and skin effect of electromagnetic processes at very small time scales can not be neglected,and must be modelled based on three-dimensional eddy fields.Third,the current field,the eddy current field,and the thermal field are inter coupled together.Fourth,from the physical nature of the field,these multi-physics fields(current field,eddy field and thermal field)are complicated three-dimensional ones.Fifth,not only the time scales of different physics fields are different,but also those of the same physics field such as the current field of the carrier transport equation even in the turn-on,turn-off;and continuous turn-on periods are different.Nevertheless,the aforementioned issues and complications are the current topical issues in the computational electromagnetics study,and are still challenging for further investigation.It should be pointed out that the study of large-capacity power electronic devices and systems is mainly in the line of interactions of large time scale heat,electric,and stress multi-physics fields;and only lukewarm efforts are given to those of middle and small time scale multiple physics quantities.As a consequence,the multi-physics field coupling mechanism in multi-time scales of large capacity power electronic devices is still unclear to some extent.In this regard,based on a key project of national natural science foundation of China entitled"Modeling and Operational Mechanism of Multi time Scale dynamics of a Mixed Large-capacity Hybrid Power Electronic Systems",this disertation focuses on modeling and solution methodology of multi time scale and multi-physics fields of IGBTs.More specially,The main works and research findings are summarized as:1.The model and solution methodology of multi-time scale current field of an IGBT module.In the line of this study,the two-dimensional distribution and the nonlinear characteristics of the carriers are firstly considered in the carrier ambipolar diffusion equation(ADE).Also,the developed numerical model considers different complex operating conditions including full carrier injection and true dynamics.In order to take account of the external circuit stray inductance and stray capacitance in considerations for a small time scale transients,a coupled ADE-external circuit model is developed and the corresponding solution methodology is developed.In addition,for different engineering application perspectives,a diversity of simplified models and solution methodologies of the aforementioned complex ones are further developed.2.The numerical model and solution methodology of three-dimensional electric field and temperature field of IGBT module based on network topological approach.IGBT has the advantages of high power density and low loss,and have been widely used in high frequency and high power applications.Junction temperature is a key parameter for predicting IGBT reliability and a key stress source for IGBT failure.Therefore,a dynamic thermal field model of IGBT to accurately predict the junction temperature of the device is invaluable in engineering application.In this regard,a general network topological approach methodology suitable for IGBT temperature field analysis and calculation is proposed,including the numerical techniques to deal with the boundary conditions of different media.Subsequently,a thermal model based on network topological approach for medium-time scale IGBT temperature field is developed,and the effects of nonlinear and three-dimensional heat distribution of media characteristic parameters are considered.Finally,the coupling analysis and calculation of the dynamic thermal-current field of a typical IGBT module are conducted using the just developed model and methodology.The accuracy and solution speed of the presented works are verified by comparing the numerical results of the presented model and methodology,and the commercial software ANSYS.3.The theory and algorithm of broadband ENOR reduction.The underlying principle of the finite element method,the finite difference method,or the proposed multiple network method is to transfer the partial differential equation in a continuous domain into a large algebraic equation set in a discrete domain,and then solve it.For complex three-dimensional multi-physics field problems,the order of the discrete algebraic equation set is extremely huge.Consequently,the solution of the corresponding algebraic equation set requires a huge amount of computational resources and times.Therefore,the existing numerical methods are inconvenient for the analysis and calculation of engineering field problems to some contents.As a result,the reduction theory and algorithm for large-scale algebraic equation set(model)have recently become topical issues of computational electromagnetics.For this purpose,to respond to the"broadband"characteristics of the IGBT transient multi-physics behaviors,a broadband ENOR reduction algorithm is introduced,and applied to the proposed IGBT thermal model for order reduction.The proposed reduced order algorithm(bro adband ENOR)is structured on the classical ENOR reduced order algorithm.By introducing the working frequency widening technique and the adaptive parameter adj ustment algorithm,the proposed reduced model can exactly reproduce the broadband dynamic response characteristic of an extremely complex responses.4.The coupled finite element-distribution circuit model and solution methodology of multi-time scale three-dimensional eddy field in an IGBT module.As the switching frequency increases,the frequency band of the electromagnetic performances of a IGBT based power electronics device for energy conversion and utilization becomes extremely wide.Consequently,the time scale of the dynamic process is reduced from millisecond to microsecond,and even nanosecond.Accordingly,the displacement current and the skin effect of the electromagnetic process under small time scales in an IGBT module(including the body)must be considered.Also,the neighboring effect of the lead is significant.In this point of view,the conventional lumped circuit model is no longer applicable to the analysis and simulation of electromagnetic processes under multiple time scales,especially in small time scale.In this regard,the coupled three dimensional eddy current field and external circuit model is finally studied.In order to consider the displacement current and the neighboring effect of the lead,the finite element method is used for three-dimensional eddy field in the body of an IGBT module.In order to consider the stray parameters of the circuit of the system or device,the distributed circuit model is developed.To solve the aforementioned coupled field-circuit model,an iterative solution methodology is proposed.Numerical results on a case study using the proposed model and solution methodology are reported to show the feasibility of the presented work...