Supervisor:
Stig Munk-Nielsen

Co-Supervisor:
Asger Bjørn Jørgensen

Assessment Committee:
Zhe Chen

Lars Helle, Vestas

Jacek Rabkowski, Warsaw University of Technology

Moderator:
Fangzhou Zhao

Abstract:

Power electronics converters based on fully-controlled power semiconductor devices play a crucial role in industrial applications for satisfying the requirement of solid power controllability. As the demand for power rating keeps growing, they are developing towards higher voltage for the purpose of saving copper loss and cost, which leads to the widespread use and promising future of medium voltage (MV) (1 kV - 35 kV) converters.

As is widely known, the performance of power device is of great significance to converters. Till now, silicon (Si) insulated-gate-bipolar-transistors (IGBTs) still dominate in the field due to their standardized fabrications, mature designs, and improved performances. Compared with the Si devices, Silicon Carbide (SiC) devices enable operation at higher blocking voltage, temperature and higher switching speed while less power loss. Thanks to the development of SiC technology, MV SiC metal-oxide-semiconductor field-effect transistor (MOSFET) rated from 3.3 kV to 15 kV has attracted a lot of attentions due to its superior switching characteristics and becomes the most promising power device to challenge Si IGBT’s hegemony. Consequently, to prompt this evolution, it is essential to research the reliable gate driver (GD) design and series connection design for complying with the voltage standard.

In this background, the Ph.D. project aims to identify the hardware design challenges when developing MV converters with MV SiC MOSFETs and proposes to utilize self-powered concept for easing the common mode noise and isolation burden of GD design. Furthermore, series-connection of MV SiC MOSFETs is researched based on the self-powered design, which is categorized into two groups named as direct and indirect series-connections based on intended synchronous and asynchronous switching operations. Maintaining the advantage of fast switching of SiC devices also brings on a significant challenge for the voltage balancing (VB) design of direct series-connection, and the project aims to establish corresponding models and provide effective VB solutions.