Abstract
This paper aims to point out and demonstrate the opportunities enabled by wide-bandgap (WBG) devices for multilevel converters, contributing to the international technology roadmap for WBG power semiconductors (ITRW). The emergence of silicon carbide (SiC) and gallium nitride (GaN) devices offers new opportunities to push the boundaries of power converter performances. Featuring high single-device blocking voltage and ultra-low switching loss, WBG devices can enable a group of multilevel converters with simplified structures and a higher number of levels to be practically implemented in applications with various power levels. This paper highlights how the use of WBG devices can reduce the number of required devices in the simplified multilevel topologies, how the capacitor voltage balance can be achieved with the newly proposed redundant level modulation (RLM) enabled by the ultra-low switching loss of WBG devices and how the switching frequency and efficiency can be improved with WBG multilevel converters. A 1.2 kV/100 kW, three-phase demonstrator implemented with a simplified four-level active neutral point clamped (ANPC) structure and commercial SiC power modules is studied to show the opportunities brought by WBG devices for multilevel converters. A voltage balancing scheme based on the RLM and a power loss analysis are presented for this configuration.
Highlights
This paper aims to point out and demonstrate the opportunities enabled by wide-bandgap (WBG) devices for multilevel converters, contributing to the international technology roadmap for WBG power semiconductors (ITRW)
WIDE-BANDGAP (WBG) power devices developed over the past decades, such as silicon carbide (SiC) and gallium nitride (GaN) devices, offer new opportunities pushing the boundaries of power converter performances [1]
Researchers are still actively deriving multilevel topologies with more voltage levels [2], [3] to cope with the trend of higher voltage systems (e.g. 800 V dc instead of 400 V dc, medium voltage instead of low voltage due to increased power demand in various applications), while mitigating the impact on converter performance caused by the higher switching voltage and switching loss, which is justified in the scaling law for multilevel converters presented in [8]
Summary
WIDE-BANDGAP (WBG) power devices developed over the past decades, such as silicon carbide (SiC) and gallium nitride (GaN) devices, offer new opportunities pushing the boundaries of power converter performances [1]. SiC devices bring new opportunities for this group of multilevel topologies because of their higher singledevice blocking voltage (e.g. 10+ kV in SiC MOSFETs and 15+kV in SiC IGBTs, in contrast to 6.6 kV in Silicon (Si) IGBTs) [16] and significantly lower switching losses. These two features of SiC devices exactly combat the two weaknesses (i.e., higher voltage rating device and capacitor voltage balancing) mentioned above in simplified and highernumber-of-level topologies, which can enable these topologies to be practically implemented. To demonstrate the benefits of SiC devices, a quantified device loss analysis is conducted against commercial Si counterparts
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