High-Voltage and EMC-Oriented Thermal Management System Design for 13.8 kV AC Flying Capacitor Converter Based-on 10 kV SiC MOSFETs

Abstract

Thermal management components-such as heat sinks, temperature sensors, fans, blowers, and pumps-typically include conductive parts that are referenced to ground or to a specific high-voltage node. Integrating these elements into a mediumvoltage converter is challenging due to the high electric-field intensity environment, particularly under high power-density constraints, which increase the risk of insulation failure. The use of wide bandgap devices further complicates the design, as parasitic capacitances between components and ground provide paths for common-mode currents driven by the high $d v / d t$ of fast-switching devices at high blocking voltages. Therefore, the thermal management system must address not only the temperature control issue, but also insulation coordination and the minimization of coupling capacitances to ground. This paper presents the thermal design for a 22 kV dc 7-level flying capacitor converter based on 10 kV SiC MOSFETs, with emphasis on controlling electric-field intensity and mitigating common-mode currents. The impacts of heat-sink referencing and cooling channel configuration on insulation and EMI are analyzed. Partial discharge experiments are presented to validate the proposed design.