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This study is focused on evaluating the advantages of 6.5-kV SiC p-i-n diodes in a 4.16-kV, 8-MVA neutral point clamped (NPC) voltage source converter. Electrothermal models of the power semiconductors are elaborated based on measurement data of a SiC diode module prototype, as well as of commercial Si devices. These models are integrated into a converter simulation, where the junction temperatures of each device are used to determine the maximum power output under different device configurations. For the analysis, a parallel connection of two 6.5-kV insulated-gate bipolar transistors (IGBTs) as well as a series connection of two 3.3-kV IGBTs are considered as switches. The influence of the current change rate during the IGBT turn-on is also studied. SiC p-i-n diodes are used as a replacement for the NPC diodes of the converter and as antiparallel diodes in IGBT modules. The results obtained indicate that an increase in the output power of 17% can be achieved using SiC NPC diodes for the studied current change rates. Alternatively, for a constant output power, the switching frequency of the converter can be increased by 69%, reducing the converter size and system costs by the use of smaller filters. [ABSTRACT FROM AUTHOR]

The parallel connection of IGBTs is being applied in various low- and medium-voltage converters. The selection of the devices, the manual parametrization of gate units, and the substantial device derating are substantial disadvantages of state-of-the-art converters with parallel-connected insulated-gate bipolar transistors (IGBTs). A new, low-expensive, and automated delay-time compensation method without additional current measurements was introduced in the 2011 IEEE Energy Conversion Congress and Exposition. This paper briefly reviews the structure and function of this new scheme, shows the extension of the scheme for three parallel-connected IGBTs, and investigates the performance of the new delay-time compensation principle for sinusoidal current operation at different $\cos\phi$ and m_{a} values, as in a converter for drives. [ABSTRACT FROM AUTHOR]

This paper introduces a 6.5-kV 1-kA SiC PiN diode module for megawatt-range medium voltage converters. The analysis comprises a short description of the die and module technology and a device characterization. The effects of di/dt and temperature variation, as well as parasitic oscillations are discussed. A comparison of the results with a commercial Si diode (6.5 kV and 1.2 kA) is included. In the last section, an estimation of maximum converter output power, maximum switching frequency, losses and efficiency in a 3L-NPC converter operating with SiC and Si diodes is presented. The analyzed diode module exhibits a very good performance regarding switching loss reduction, which allows an increase of at least 16% in the output power of a 6-MVA converter. Alternatively, the switching frequency can be increased by 46%. [ABSTRACT FROM AUTHOR]

Recently developed insulated-gate bipolar transistor (IGBT) press-pack (PP) devices with a blocking voltage of 4.5 kV are being used in medium-voltage converters as an alternative to integrated gate-commutated thyristors (IGCTs). This paper presents an overview of PP packaging and both semiconductor technologies. A quantitative comparison of these devices is achieved through measurements for a 4.5-kV 1.2-kA IGBT and a 4.5-kV 4-kA IGCT. The laboratory test bench for the switching transient characterization at a dc-link voltage of 2.5 kV and currents up to 3 kA is described. Conduction, blocking, and switching behavior for junction temperatures up to 125 ^\circ\C are investigated. The IGCT and the IGBT are tested using a di/dt-limiting clamp circuit. In addition, the IGBT is tested in hard switching mode. [ABSTRACT FROM PUBLISHER]

This paper describes the design of a (4-ky, 4.16-MVA) three-level neutral-point-clamped-, three-level flying-capacitor-, four-level flying-capacitor-, and nine-level series-connected H-bridge voltage-source converter on the basis of state-of-the-art 6.5-, 4.5-, 3.3 and 1.7-ky insulated gate bipolar transistors. The semiconductor loss distribution and the design of semiconductors and passive components are compared for a medium switching frequency assuming a constant converter efficiency of about 99%. To evaluate the converter characteristics in high switching frequency applications, a second comparison is realized for the maximum switching frequencies assuming a constant expense of semiconductors in all converters. [ABSTRACT FROM AUTHOR]

The low-frequency line transformer in todays ac rail vehicles suffers from poor efficiency and a substantial weight. Future traction drives may operate directly from the mains without this transformer. A feasible concept for a transformerless drive system consists of series connected medium voltage converters applying modern high-voltage insulated gate bipolar transistors (HV-IGBTs). In a first design step, the switching characteristics and losses of 6.5-ky IGBTs are compared to 3.3-kV and 4.5-kV IGBTs which are already commercially used in traction applications. Based on the considered HIV-IGBTs, the properties of multilevel converters are analyzed and their applicability to the transformerless system is evaluated. The paper focusses on a loss analysis of the converters. Reliability aspects and harmonic spectra are briefly discussed. Taking these design aspects into account, the three-level neutral point clamped converter turns out to be a reasonable solution to realize line and motor converter modules in a transformerless traction system. [ABSTRACT FROM AUTHOR]