A GaN-based switched-mode gate-drive unit for medium-voltage IGBTs

Beushausen, Steffen; de Doncker, Rik W. (Thesis advisor); Divan, Deepakraj M. (Thesis advisor)

1. Auflage. - Aachen : E.ON Energy Research Center, RWTH Aachen University (2021)
Book, Dissertation / PhD Thesis

In: E.ON Energy Research Center ; PGS, Power Generation and Storage Systems 92
Page(s)/Article-Nr.: 1 Online-Ressource : Illustrationen, Diagramme

Dissertation, RWTH Aachen University, 2021

Abstract

By the year 2010, 21 % of the primary energy consumption in the European Union was in the electricity sector, with a rising projection of up to 28 % by the year 2050. This increasing demand of electric energy, combined with the increasing decentralized generation due to renewables, calls for innovative solutions in the power generation, distribution and transmission sectors. To tackle some of the arising challenges associated with the increase in both demand and decentralized generation, the "Flexible Electrical Networks"(FEN) research campus of the German Federal Ministry of Education and Research (BMBF) was founded. Although in the end the challenges manifest predominantly on the system level, many issues can and need to be solved at the root, hence, at the component level. Thus, FEN focuses not only on system-level research, but also on component-level development for an improvement of the future power distribution. The component-level research of FEN started with work on both converters and components such as power semiconductor devices and medium-frequency transformers (MFTs) for high-power medium voltage (MV) direct current (DC) converters. The presented work was part of this research focused on the improvement of insulated-gate bipolar transistor (IGBT) characteristics in MV converter applications. A gallium nitride (GaN)-based switched-mode gate-drive unit (SMGDU) for MV-IGBTs was developed to optimize the dynamic behavior of the IGBT according to its application. The gate-drive unit (GDU) consists of a power stage with GaN high-electron-mobility transistors (HEMTs) in half-bridge configuration forming a buck converter with the gate-emitter capacitance of the IGBT as the output capacitance. It is able to switch with a frequency of up to 30 MHz to control the switching behavior of the IGBT during switching transients through a dynamic gate-current and -voltage adjustment. First, an open-loop approach was implemented to explore the possibilities of dynamically adjusting the IGBT’s switching transients to reduce device stress and switching losses. To achieve this dynamic adjustment, a field-programmable gate array (FPGA) changes the duty cycle of the SMGDUs output stage during the switching transients according to a pre-programmed profile. Next, a separate transient closed-loop controller that controls either the current or the voltage slope was implemented. Due to the short actuation times in the range of 1 μs to 2 μs, a purely analog implementation was chosen for the closed-loop transient controller. Finally, a combined closed-loop transient controller was implemented, effectively influencing both the voltage and current slew rates of the MV-IGBT. In conclusion, it has been found that the proposed SMGDU is able to dynamically control the switching transients of MV-IGBTs (UCES typically 3.3 kV to 6.5 kV), in particular to reduce peak power stress and switching losses. It is expected that the proposed gate driver, which can adapt the switching transients to the requirements of a given application, offers advantages towards electro-magnetic interference (EMI) reduction, filter size reduction, efficiency improvements and bearing lifetime of electrical machines in inverter fed drives.