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Design Steps Toward a 40-kVA SiC JFET Inverter With Natural-Convection Cooling and an Efficiency Exceeding 99.5%
KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.ORCID iD: 0000-0002-1755-1365
2013 (English)In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 49, no 4, 1589-1598 p.Article in journal (Refereed) Published
Abstract [en]

This paper describes the concept, design, construction, and experimental investigation of a 40-kVA inverter with silicon carbide junction field-effect transistors (JFETs). The inverter was designed to reach an efficiency exceeding 99.5%. The size of the heat sink is significantly reduced in comparison to silicon insulated-gate bipolar transistor designs, and the high efficiency makes it possible to use free-convection cooling. This could potentially increase reliability compared with solutions with fans. A very low conduction loss has been achieved by parallel connecting ten 85-m Omega normally-ON JFETs in each switch position. A special gate-drive solution was applied, forcing the transistors to switch very fast (approximately 10 kV/mu s), resulting in very low switching losses. As output power is almost equal to input power, special effort was done to precisely determine the amount of semiconductor power losses via comparative thermal measurements. A detailed analysis of the measurements shows that the efficiency of the inverter is close to 99.7% at 40 kVA.

Place, publisher, year, edition, pages
IEEE Press, 2013. Vol. 49, no 4, 1589-1598 p.
Keyword [en]
Silicon carbide, DC/AC inverters, parallel-connection, high-efficiency, efficiency measurements
National Category
Engineering and Technology
Research subject
Järnvägsgruppen - Elsystem
Identifiers
URN: urn:nbn:se:kth:diva-122677DOI: 10.1109/TIA.2013.2258132ISI: 000322030700012Scopus ID: 2-s2.0-84880888768OAI: oai:DiVA.org:kth-122677DiVA: diva2:623254
Note

QC 20130710

Available from: 2013-05-26 Created: 2013-05-26 Last updated: 2017-12-06Bibliographically approved
In thesis
1. On Gate Drivers and Applications of Normally-ON SiC JFETs
Open this publication in new window or tab >>On Gate Drivers and Applications of Normally-ON SiC JFETs
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, various issues regarding normally-ON silicon carbide (SiC)Junction Field-Effect Transistors (JFETs) are treated. Silicon carbide powersemiconductor devices are able to operate at higher switching frequencies,higher efficiencies, and higher temperatures compared to silicon counterparts.From a system perspective, these three advantages of silicon carbide can determinethe three possible design directions: high efficiency, high switchingfrequency, and high temperature.The structure designs of the commercially-available SiC power transistorsalong with a variety of macroscopic characteristics are presented. Apart fromthe common design and performance problems, each of these devices suffersfrom different issues and challenges which must be dealt with in order to pavethe way for mass production. Moreover, the expected characteristics of thefuture silicon carbide devices are briefly discussed. The presented investigationreveals that, from the system point-of-view, the normally-ON JFET isone of the most challenging silicon carbide devices. There are basically twoJFET designs which were proposed during the last years and they are bothconsidered.The state-of-the-art gate driver for normally-ON SiC JFETs, which wasproposed a few years ago is briefly described. Using this gate driver, theswitching performance of both Junction Field-Effect Transistor designs wasexperimentally investigated.Considering the current development state of the available normally-ONSiC JFETs, the only way to reach higher current rating is to parallel-connecteither single-chip discrete devices or to build multichip modules. Four deviceparameters as well as the stray inductances of the circuit layout might affectthe feasibility of parallel connection. The static and dynamic performance ofvarious combinations of parallel-connected normally-ON JFETs were experimentallyinvestigated using two different gate-driver configurations.A self-powered gate driver for normally-ON SiC JFETs, which is basicallya circuit solution to the “normally-ON problem” is also shown. This gatedriver is both able to turn OFF the shoot-through current during the startupprocess, while it also supplies the steady-state power to the gate-drivecircuit. From experiments, it has been shown that in a half-bridge converterconsisting of normally-ON SiC JFETs, the shoot-through current is turnedOFF within approximately 20 μs.Last but not least, the potential benefits of employing normally-ON SiCJFETs in future power electronics applications is also presented. In particular,it has been shown that using normally-ON JFETs efficiencies equal 99.8% and99.6% might be achieved for a 350 MW modular multilevel converter and a40 kVA three-phase two-level voltage source converter, respectively.Conclusions and suggestions for future work are given in the last chapterof this thesis.

Abstract [sv]

I denna avhandling behandlas olika aspekter av normally–ON junction–field–effect–transistorer (JFETar) baserade på kiselkarbid (SiC). Effekthalvledarkomponenteri SiC kan arbeta vid högre switchfrekvens, högre verkningsgradoch högre temperatur än motsvarigheterna i kisel. Ur ett systemperspektivkan de tre nämnda fördelarna användas i omvandlarkonstruktionen för attuppnå antingen hög verkningsgrad, hög switchfrekvens eller hög temperaturtålighet.Såväl halvledarstrukturen som de makroskopiska egenskaperna för kommersiellttillgängliga SiC–transistorer presenteras. Bortsett från de vanligakonstruktions–och prestandaproblemen lider de olika komponenterna av ettantal tillkortakommanden som måste övervinnas för att bana väg för massproduktion.Även framtida SiC–komponenter diskuteras.Ur ett systemperspektiv är normally-ON JFETen en av de mest utmanandeSiC-komponenterna. De två varianter av denna komponent som varittillgängliga de senaste åren har båda avhandlats.State–of–the–art–drivdonet för normally-ON JFETar som presenteradesför några år sedan beskrivs i korthet. Med detta drivdon undersöks switchegenskapernaför båda JFET-typerna experimentellt.Vid beaktande av det aktuella utvecklingsstadiet av de tillgängliga normally–ON JFETarna i SiC, är det möjligt att uppnå höga märkströmmar endastom ett antal single–chip–komponenter parallellkopplas eller om multichipmodulerbyggs. Fyra komponentparametrar samt strö-induktanser för kretsenkan förutses påverka parallellkopplingen. De statiska och dynamiska egenskapernaför olika kombinationer av parallellkopplade normally-ON JFETarundersöks experimentellt med två olika gate–drivdonskonfigurationer.Ett självdrivande gate-drivdon för normally-ON JFETar presenteras också.Drivdonet är en kretslösning till “normally–ON–problemet”. Detta gatedrivdonkan både stänga av kortslutningsströmmen vid uppstart och tillhandahållaströmförsörjning vid normal drift. Med hjälp av en halvbrygga medkiselkarbidbaserade normally–ON JFETar har det visats att kortslutningsströmmenkan stängas av inom cirka 20 μs.Sist, men inte minst, presenteras de potentiella fördelarna med användningenav SiC-baserade normally-ON JFETar i framtida effektelektroniskatillämpningar. Speciellt visas att verkningsgrader av 99.8% respektive 99.5%kan uppnås i fallet av en 350 MW modular multilevel converter och i en40 kVA tvånivåväxelriktare. Sista kaplitet beskriver slutsatser och föreslagetframtida arbete.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. x, 102 p.
Series
Trita-EE, ISSN 1653-5146 ; 2013:28
Keyword
Silicon Carbide, Normally-ON Junction Field-Effect Transistors (JFETs), Gate-Drive Circuits, Protection circuits, High-Efficiency Converters.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Järnvägsgruppen - Elsystem
Identifiers
urn:nbn:se:kth:diva-122679 (URN)978-91-7501-799-0 (ISBN)
Public defence
2013-06-14, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20130527

Available from: 2013-05-27 Created: 2013-05-26 Last updated: 2013-05-27Bibliographically approved

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