IEEE Workshop on Wide Bandgap Power Devices and Applications in Asia (WiPDA Asia 2018)

298 / 2017-12-07 23:43:40

Extra Device Capacitance in Three-level Converters and Loss Re-evaluation via Conventional DPT Data

Plenary track > Hard-switched and soft-switched applications

In this paper, an extra junction capacitance and its associated switching commutation path are found in three-level ac/dc converters, which were overlooked due to the off-state of the related device within half line cycle. The impact of this effect on power loss is analyzed, showing an underestimated switching loss in the traditional loss calculation of three-level converters. Through a proposed loss re-evaluation approach based on energy data of conventional double pulse tester (DPT), the corrected switching loss matches experimental results obtained from a 650 V enhancement-mode Gallium Nitride (GaN) based Vienna-type rectifier. And the dominant extra switching loss is found to be Coss loss instead of overlap loss in WBG converters. Thus, the effect is severe in high-speed WBG three-level converters.