| Press-packed IGBT(PPI)devices have been widely used in various types of high-voltage and large-capacity power converters and control equipment in smart grids,which,compared with traditional IGBT modules,have the advantages of high-power density,double-sided heat dissipation,failure short circuit,and easy series connection.The development of PPI with independent intellectual property rights can help to break the technology blockade from foreign companies,which has important strategic significance and economic value for the development of the advanced transmission technology.The Current sharing problem is one of the key challenges during the independent development process of the PPI devices,the imbalance of the parallel chip currents inside IGBT device may cause the chip overheating and device failure.Because the chip branches inside the device are enclosed and densely distributed,there is still no accurate method to measure the current of the parallel chips inside the device.Therefore,it is of great significance to study the measurement method of densely distributed branch currents inside the device and to master the distribution of each chip in the process of device operation for guiding chip screening and package design.This thesis focuses on the difficult problem of chip current sharing measurement inside PPI devices.By combining theoretical analysis with experimental measurement,it is studied from three aspects,the mutual inductance characteristic and design method of circular Rogowski coils,the development of current measurement system of parallel chip inside PPI devices,and influence principle and regulation method of packaging structure on current sharing,A high precision current measurement system for PPI devices is developed,which breaks through the bottleneck of the current measurement error of the existing measurement methods for PPI IGBT devices.Firstly,the characteristics of mutual inductance between circular Rogowski coil and current carrying conductor are analyzed and the design method of dimension parameters is proposed.Aiming at the circular Rogowski coil with arbitrary size parameters and turns,the concise analytical formula of mutual inductance of Rogowski coil expressed by complex polynomial of order N was derived.On this basis,the spatial distribution characteristics of mutual inductance deviation of circular Rogowski coil was revealed,such as mapping relation between internal and external Rogowski coil,and zero deviation line.The application range is extended to complex working conditions such as discontinuously wired Rogowski coil,cross sectional area and inclined current carrying conductor.The design method of size parameters and turns number for circular Rogowski coil is proposed considering the measurement error,and the embedded chip currents measuring system based on circular PCB(Printed circuit board)Rogowski coil for 4.5kV/100A PPI device and 18kV SiC device is developed.Secondly,the wiring method of square Rogowski coil densely distributed in PPI device is proposed.The equivalence relation between mutual inductance and two-dimensional electrostatic field is established,the turns arrangement for Rogowski coil with arbitrary shape is acquired by solving the boundary problem of electrostatic field and discretization of the turns number N.Furthermore,the wiring method of segmented turns is proposed to split the single outer edge of the original single-turn rectangular coil into multiple outer edges,which enhances the anti-interference ability of Rogowski coil.On this basis,the integrated design method of multi-Rogowski coil is proposed.The space electromagnetic field interference is effectively restrained by the same layer lead of positive and negative leads,full coverage of double shield layer,and single point grounding of Rogowski coil.The measurement error of single Rogowski coil is only 1.8%.The current measurement system based on square Rogowski coil is applied to the 3.3kV/1500A PPI device.Finally,A regulation method of current sharing of parallel branches inside PPI device is proposed and verified by square Rogowski coil.Based on the established circuit model of parallel branch magnetic field coupling,the error formula for calculating branch current distribution by the flux method compared with the energy method is proposed under the model of parallel filament conductor segments with single-ended injection and single-ended outflow.The formula shows that calculation results of the two methods are only different in amplitude,but the distribution law is consistent.The current distribution formula of parallel conductors with external loops is deduced,and the influence of external loops on current distribution is only related to the mutual inductance between external loops and internal branches.For the device packaging structure considering the busbar,the ideal current sharing condition of the parallel branch inside the device is obtained,and the equivalent branch inductance characterization method of the unbalanced current of the parallel branch is mastered.On this basis,a current sharing regulation method using arc-shaped grooved busbars is proposed.The imbalance factor of parallel branch currents decreases with the increase of the groove angle.The measurement results of square Rogowski coils verify the effectiveness of the proposed regulation method.This thesis fills in the gap in the field of accurate measurement of the currents of densely distributed parallel chips inside the PPI devices,solves the problem that the previous measurement method cannot be used in industry due to the lack of measurement accuracy.The proposed measurement method of parallel chip currents lays the foundation for chip screening,packaging design,and reliability improvement in the process of independent development of domestic power electronic devices. |
PDF Full Text Request