Research On Stray Inductance Of DC Busbar In Power Electronic Transformer

Power Electronic Transformer(short for PET)use the power electronics and power electronic converter technology to transform and control the energy.Compared with the traditional power transformers,it has some advantages,such as high energy conversion efficiency,small pollution to the power grid,high control ability and small size and light weight,which have broad prospects in the future development of the power grid.Commonly used in the power electronic transformer busbar power module and the support capacitor.The DC busbar in the work will produce stray inductance,stray inductance in the IGBT turn-off moment will cause instantaneous voltage surge and strong electromagnetic interference,which will reduce the power module switching performance,and even damage the power module,thus it will affect PET's reliable work and life expectancyAiming at the voltage spike caused by stray IGBT during turn-off,this paper first analyzes the structure and application principle of DC bus,and uses the Simplorer software to accurately model the IGBT used in this paper,The actual parameters of the IGBT fitted to the model built.On this basis,the software builds a half-bridge circuit simulation model to compare the effects of different stray inductances on the turn-on and turn-off transient behavior of IGBTs,and illustrates the unfavorable effects of stray inductances on the converter.Secondly,the relationship between stray inductance of DC busbar and its structure and capacitance layout is studied.Q3 D software was used to extraction the stray inductances of busbars with different sizes,openings,grooving,bending and device layout that are common structures in model.Combined with the analysis of current flow paths in busbars,the relationship of different busbar structures and the size of the different stray inductance is found and a low inductance busbar structure optimization method based on improving the current flow channel is proposed.This method is used to optimize the design of a busbar structure of an active power filter.The stray inductance of the busbars before and after optimization is measured experimentally and the correctness of the optimization method is verified.In addition,the relationship between the layout of the busbar capacitor and the stray inductance is studied.The results show that the stray inductance of the DC side and the two ends of the capacitor is smaller than the layout of DC side and the capacitor in same side.The stray inductance is smaller when compared the layout of the capacitor in different side with it same side.Then design a set of modular busbars verify that the above two capacitor layout method can effectively reduce the total number of stray inductance in the busbar.Finally,the influence of the busbar temperature and the frequency of the incoming current on the stray inductance is studied.Firstly,the mechanism of temperature rise in busbar is analyzed and the influence of temperature on the physical parameters of busbar material is pointed out.It is found that temperature has little effect on stray inductance,but will lead to the increase of busbar equivalent resistance and then reduce the ampacity of busbar.The effect of current frequency on the bus bar stray inductance is analyzed by Q3 D software.The skin effect and the proximity are analyzed.It is found that the stray inductance decreases slightly with the increase of the current frequency.However,the equivalent resistance of busbar is increases.