# Improvement on the Laminated Busbar of NPC Three-Level Inverters based on a Supersymmetric Mirror Circulation 3D Cubical Thermal Model

• He, Feng-You (Dept. of Information and Electrical Engineering, China University of Mining and Technology) ;
• Xu, Shi-Zhou (College of Electronic and Electrical Engineering, Henan Normal University) ;
• Geng, Cheng-Fei (Dept. of Information and Electrical Engineering, China University of Mining and Technology)
• Accepted : 2016.07.11
• Published : 2016.11.20

#### Abstract

Laminated busbars with a low stray inductance are widely used in NPC three-level inverters, even though some of them have poor performances in heat equilibrium and overvoltage suppression. Therefore, a theoretical method is in need to establish an accurate mathematical model of laminated busbars and to calculate the impedance and stray inductance of each commutation loop to improve the heat equilibrium and overvoltage suppression performance. Firstly, an equivalent circuit of a NPC three-level inverter laminated busbar was built with an analysis of the commutation processes. Secondly, on the basis of a 3D (three dimensional) cubical thermal model and mirror circulation theory, a supersymmetric mirror circulation 3D cubical thermal model was built. Based on this, the laminated busbar was decomposed in 3D space to calculate the equivalent resistance and stray inductance in each commutation loop. Finally, the model and analysis results were put into a busbar design, simulation and experiments, whose results demonstrate the accuracy and feasibility of the proposed method.

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