Influence Mechanism And Optimization Method Of Stray Inductance Of DC Busbar In Power Electronic Transformer

Power electronic transformer is a new type of transformer that realizes energy transmission and power conversion through power electronics technology.Compared with traditional transformers,it has many advantages such as high power conversion efficiency,strong controllability and light size.It will be in the future power industry.Broad application prospects.In the power electronic transformer,the busbar is usually connected to the power switch module and the supporting capacitor group on the DC side.The use of the DC busbar can reduce the electromagnetic interference of the system and improve the stability of the system,but the stray inductance generated in the system work can also cause problems such as high peak voltage of the IGBT turn-off voltage and electromagnetic interference and even causing IGBT breakdown,affecting the life and working stability of the entire system.This paper mainly studies the modeling,extraction,influence and optimization of DC busbar stray inductance.Firstly,the working principle,equivalent model and low-inductance characteristics of DC busbar in power electronic transformer are analyzed.Based on the analysis of IGBT switching characteristics,the dynamic model of IGBT is established by Simplorer software.In addition,the established IGBT dynamic model is used to analyze the influence of stray inductance on the IGBT switching characteristics.It is found that the larger the stray inductance is,the longer the IGBT turn-off process is and the higher the voltage impact is.The effectiveness of the built IGBT model is verified from the side.Secondly,based on the detailed analysis of the turn-on and turn-off losses of IGBT modules,the influence of stray inductance on the power loss of IGBT modules is studied.A power loss calculation method considering the influence of stray inductance is proposed.Using the proposed loss calculation method,the Buck circuit is taken as an example to estimate the efficiency of the system under different stray inductances.It is found that the efficiency of the stray inductance decreases by about 0.04% for every 40 nH increase.Then,aiming at the low-stray inductance design of DC busbar of power electronic transformer,the influence of the same side layout and side layout of the capacitor group on the stray inductance is studied from the perspective of optimizing the layout of the DC side capacitor group.A side layout structure that reduces the stray inductance of the loop.Simulation and experimental results show that the capacitive component side layout can effectively reduce the loop stray inductance.At the same time,for the problem that the current variation rate is difficult to accurately extract and make the stray inductance calculation inaccurate during the IGBT turn-off process,based on the current-voltage waveform of the IGBT turn-off transient,an improved method for extracting stray inductance is studied.An optimization method for calculating stray inductance based on weighted least squares method.The simulation and experimental results show that the method can improve the accuracy of linearization extraction of IGBT turn-off current rate and reduce the calculation error of line stray inductance.Finally,for the problem of stray inductance extraction and multi-busbar optimal bridging scheme for multi-busbar simultaneous layout in power electronic transformers,two sets of DC busbars are analyzed,and multiple busbar coexistence and different bridging modes are analyzed.Based on the influence of stray inductance,the influence of geometric factors on stray inductance between multiple busbars is studied,and the stray inductance under different bridging modes of busbars is simulated.The research shows that as the distance between adjacent groups of busbars decreases,the stray inductance will decrease on the basis of the original stray inductance,and the stray inductance decreases when the upper and lower adjacent layouts are larger than the left and right phases.The situation of the neighboring layout;as the angle of the two DC busbars increases,the stray inductance increases,but the upper and lower layouts are more obvious than the corresponding busbar stray inductances in the left and right layout;the two busbars are bridged.When the two sets of symmetrical bridging methods are most reasonable,the stray inductance of the lower busbar can be obtained,and the mechanical connection of the busbar can be simplified.