Electrical Field Analysis and Insulation Evaluation of a 6 kV H-bridge Power Electronics Building Block (PEBB) using 10 kV SiC MOSFET Devices

As a consequence of higher blocking voltage and power density by using SiC devices, detailed analysis and careful design of electrical insulation are required. High partial discharge initiated from high electric field regions damages the insulation materials and leads to insulation failure. Therefore, the study of the electric field intensity distribution in all components of a high power density SiC-based converter and among multiple converters, if modular multilevel converter used, is needed. In this paper, a three-dimensional model developed in ANSYS of a high power density H-Bridge PEBB, benefiting from 10 kV SiC MOSFETs on a 6 kV DC bus, is presented. Using the finite element method, the electric field distribution inside the converter is calculated, and critical areas with high electric field intensities prone to initiate partial discharges are identified. Moreover, by using this model, geometry-based modifications are investigated to relieve high electric field regions. Finally, partial discharge tests have been applied to multiple critical parts, like the laminated bus and the interconnectors. It helps evaluate various insulation designs, provide some design guidelines and improvement suggestions for such application as well.