Wide-bandgap (WBG) semiconductor materials such as silicon carbide (SiC) and gallium-nitride (GaN) allow higher voltage ratings, lower on-state voltage drops, higher switching frequencies, and higher maximum temperatures. All these advantages make them an attractive choice when high-power density and high-efficiency converters are targeted. Two different gate-driver designs for SiC power devices are presented. First, a dual-function gate-driver for a power module populated with SiC junction field-effect transistors that finds a trade-off between fast switching speeds and a low oscillative performance has been presented and experimentally verified. Second, a gate-driver for SiC metal-oxide semiconductor field-effect transistors with a short-circuit protection scheme that is able to protect the converter against short-circuit conditions without compromising the switching performance during normal operation is presented and experimentally validated. The benefits and issues of using parallel-connection as the design strategy for high-efficiency and high-power converters have been presented. In order to evaluate parallel connection, a 312 kVA three-phase SiC inverter with an efficiency of 99.3 % has been designed, built, and experimentally verified. If parallel connection is chosen as design direction, an undesired trade-off between reliability and efficiency is introduced. A reliability analysis has been performed, which has shown that the gate-source voltage stress determines the reliability of the entire system. Decreasing the positive gate-source voltage could increase the reliability without significantly affecting the efficiency. If high-temperature applications are considered, relatively little attention has been paid to passive components for harsh environments. This thesis also addresses high-temperature operation. The high-temperature performance of two different designs of inductors have been tested up to 600_C. Finally, a GaN power field-effect transistor was characterized down to cryogenic temperatures. An 85 % reduction of the on-state resistance was measured at −195_C. Finally, an experimental evaluation of a 1 kW singlephase inverter at low temperatures was performed. A 33 % reduction in losses compared to room temperature was achieved at rated power. / <p>QC 20160922</p>
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:kth-192626 |
| Date | January 2016 |
| Creators | Colmenares, Juan |
| Publisher | KTH, Elkraftteknik, Stockholm |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, info:eu-repo/semantics/doctoralThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | TRITA-EE, 1653-5146 ; 2016:145 |
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