Study On Stray Inductance Characteristic Of Laminated Busbar In Large Capacity Converter

Optimizing the commutation stray parameters is recognized by academics and industry as an important means to improve the robustness and reliability of power electronic converter.The laminated busbars work as the most important part of the commutation loop,of which the variation of stray inductance and electromagnetic field distribution is very complicated under different excitation conditions.At present,the design process of laminated busbars in large-capacity power electronic devices lacks theoretical and systematic research.This paper focuses on the performance of stray inductance of laminated busbar,and deeply studies the theory analysis methods of stray inductance.The research includes the mathematical modeling of the frequency characteristics of the multilayer busbar,the relationship between the stray inductance and the high frequency capacitance,the field-circuit coupling analysis method considering the stray inductance.Firstly,in order to quantitatively calculate the stray inductance and characterize the distribution of the electromagnetic field,the distribution of the eddy current field in the middle conductor of multilayer bus bars is analyzed.The interaction between the eddy current field and the electromagnetic field is studied.The calculation formula of the stray inductance under different excitation frequencies is given.Based on the variation of the stray inductance at different frequencies,the non-linear relationship between switching-off transient voltage overshoot and the current changing rate is studied.The proposed theory is validated by the finite element numerical calculation method and the large-capacity power electronic device field-circuit coupling simulation platform.Secondly,adding high-frequency capacitors at the input port of busbar can further reduce the area of the commutation loop.In order to optimize the selection of high-frequency capacitors,from the perspective of the impedance characteristics of the busbars in the frequency domain and the transient process of the power devices in the time domain,the influence caused by decoupling capacitors on the transient commutation process of high capacity power electronic devices is analyzed.Finally,combined with the experimental results of stray inductance extraction under different working conditions of the actual bus,the influence of testing conditions on the experimental extraction of stray inductance was studied.Based on the measured data,the finite element method for extracting stray inductance of busbar with a complex structure is validated.In order to achieve a fast and accurate analysis of large-capacity power electronic converter,field-circuit coupling simulation method of large-capacity power electronic devices is studied by using power electronic simulation software,finite element analysis software and device model.The effectiveness of the analytical method is verified by comparing the experimental results of the platform with the simulation results.In this paper,the mathematical model of stray inductance frequency characteristics of laminated busbar is studied,and the optimization method of stray inductance in commutation circuit is analyzed.A field-circuit coupling analysis method suitable for large-capacity power electronic devices is proposed,which overcomes the limitation of independent analysis of electromagnetic field and external circuit,and improves the design optimization efficiency of laminated busbar in large-capacity power electronic devices.Finally,the feasibility and accuracy of the field-circuit coupling analysis method applied to the design process of large-capacity power electronic devices are proved by comparing the results of experimental waveforms with simulation waveforms in multi-time scales.