Study On The Electromagnetic Transient Analysis And IGBT Intelligent Drive Of High-Power Converter

Insulated Gate Bipolar Transistors(IGBTs)are voltage-controlled power semiconductor devices,which are widely used in medium-to high-power power electronic equipment.It combines the advantages of GTRs and MOSFETs.It has the advantages of high switching frequency,simple driving circuit,high input impedance,and low output impedance.The reliable application of high-power IGBT is the basis of various power electronic converters.At present,the main problems in the theory and application of IGBT-based large-capacity power electronic technology include:1)Insufficient understanding of switching characteristics of power semiconductor devices;2)The design of the power circuit is too idealized and empirical;3)the electromagnetic transition process of the device and equipment is unclear;4)the failure mechanism of the device and equipment are not clear,and it is difficult to troubleshoot after the failure.This dissertation mainly focuses on the above four issues,and studies the electromagnetic transient analysis technology and IGBT intelligent drive technology of high-power power electronic converter equipment.The specific research content is:The basic structure,electrical characteristics and safe working area of high power IGBTs and PiN diodes,based on the semiconductor physical mechanisms,were studied in depth,and some typical failures of high-power IGBTs encountered in scientific research work were analyzed and summarized that reveals the key issues in the application of high-power IGBT reliability.The measuring method and modeling of the stray inductance in high power laminated bus-bars for high-power IGBT converters was studied.From the perspective of electromagnetic field energy,the physical meaning of the partial inductance in the laminated busbar was analyzed.Based on this,a partial stray inductance measuring method,considering the spatial transient field,was proposed.Then,based on the application background of two different laminated busbars,the partial stray inductance of the busbar is analyzed and modeled,and the proposed stray inductance measurement method is verified.1)A set of high-power three-level inverter laminated busbars was used as the research object.The PEEC method was used to model the partial inductance of the three-level four commutation loops.The distribution of stray inductance in the commutation loop was mainly studied.Finally,the measuring method and modeling method were verified by simulations and experiment.2)A laminated busbar with an unbalanced parallel branch for electric vehicle inverters was adopted as a research object,a transient analysis method,using inductive energy storage and energy release was proposed to perform transient non-uniform current flow of IGBT terminals.The analysis also uses the PEEC method to establish a partial stray inductance model of the busbar.At the same time,the model simplification method is given.Finally,experiments and simulations verifies transient analysis and modeling methods.For the electromagnetic transient coupling problem of the back-to-back three-level converter rectifier and the power device of the inverter,the equivalent circuit model of the bus bar was established applying the PEEC method.The theoretical and experimental analysis of the IGBT overvoltage stress caused by the electromagnetic coupling problem in each switching transient state was performed,and an IGBT coupled overvoltage model was established.Aiming at the commutation loop with over-voltage risk,a pulse-delay transient decoupling method based on FPGA is proposed,and the problem of delay time selection is verified through experiments.For over-voltage problems of IGBT in high power electronic equipment,the mechanism of IGBT overvoltage generation is studied in depth from the semiconductor physics level,and a carrier extraction model is established at IGBT turn off transient.At the same time,an IGB overvoltage suppression method based on gate voltage modulation is proposed,and an intelligent digital driver board based on FPGA is designed.And the gate voltage modulation method are verified by experimental.Combined with the practical application,two feasible schemes based on look-up table method and single-pulse modulation are given.For short-circuit faults and open-circuit faults,which are commonly seen in IGBTs in high-power power electronic devices.Internal parasitic capacitance distribution of IGBT are analyzed deeply,and the changes in the gate charge under normal operation,various faults are modeled and analyzed.An IGBT on-line fault diagnosis strategy based on gate charge Qg is proposed.Through IGBT self-check before power on and real-time online fault detection,the protection and locating of 7 typical faults are realized.Finally,an FPGA-based digital intelligent driver board was designed to verify various types of faults.