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Fault-tolerant multilevel inverters outperform known fault-tolerant 2-level inverters regarding efficiency and power density. The most promising fault-tolerant multilevel inverters for system voltages below 2 kV are the flying capacitor and the active neutral point clamped type. They differ regarding required voltage overrating of semiconductors, tolerance for open and short-on failure types and maximum...
This paper presents a new gate driver concept that consists of an integrated measurement of the junction temperature and the load current of a power module during inverter operation. For junction temperature measurement the gate driver identifies the temperature sensitive on-chip internal gate resistor by means of a small identification signal that is modulated onto the positive gate voltage. To determine...
This paper presents impacts of the characteristics of Metal Oxide Varistors (MOV) for selecting and calculating the suited amount of MOVs to enable semiconductors to act as DC-Breakers. The specific structure of zinc oxide shows dependencies in its voltage and current characteristics which exhibits a hysteresis.
This paper presents an overcurrent and short-circuit (SC) detection method for high current SiC MOSFET modules. It adapts the existing desaturation detection (= UCE,desat method) known from IGBTs. These adjustments include separate detection paths for hard switching faults (HSF) and fault under load (FUL) as well as overcurrent. The necessity of a junction temperature compensation for detecting each...
Increasing the channel width of an IGBT is an obvious way to lower the Vce, sat value without any influences on the switching losses of the device. Consequently, the achievable benefit of IGBTs is limited due to the corresponding increase of the desaturation current, which threaten the short circuit robustness. This paper presents the benefits of an IGBT which could be realized, if the feature of...
The modular multilevel converter (MMC) provides a lot of features such as low harmonic voltage content, a high power quality or easy scalability. Due to its several advantages, it is a well-suited topology for high-voltage direct current (HVDC) applications. In a meshed DC grid, a current flow control is essential. In this paper, an MMC based HVDC current flow controller is described which allows...
In this paper different gate drive concepts to eliminate parasitic turn-on for SiC MOSFETs are discussed. Experimental results show a potential for lowering switching losses of SiC MOSFETs during fast switching operation, reduction of turn-off overvoltage across the bodydiode. Finally increased requirement on the gate drive unit are discussed.
This paper introduces the fault behavior of full bridge modular multilevel converters (MMCs) considering a non-simultaneous blocking of the two half bridges in each sub-module. In order to protect IGBTs in the full bridge sub-module, both sides of a full bridge sub-module are not blocked at same time point. It is assumed that the first blocking of both sides is random in each sub-module, so there...
Increasing the channel width of an IGBT is an obvious method in order to decrease the on-state losses significantly due to the lower Vce,sat-value. The accordingly higher desaturation current leads to the development of faster short circuit detection methods, such as the new 2D — short circuit detection method, which is able to detect a fault event far ahead of the desaturation process of the power...
This paper investigates the characteristic thermal properties of IGBT power modules and develops a very robust health monitoring concept to identify an aged chip-solder within a voltage source inverter. It is shown that at an optimum excitation frequency the power module structure enables a selective identification of an increased thermal chip-solder resistance Rth, 1 with a maximum Rth, 1 measuring...
Various fault-tolerant inverter structures have been proposed, which are mostly reconfigured by fault-isolating fuses. The inverter design requirements for safe fuse blowing are investigated. Moreover, the effects of differing fuse characteristics and the influence on semiconductors during fuse interruption are evaluated in theory and with a practical setup.
This paper analyzes the influence of the threshold voltage on the parallel connection of three phases of a high power SiC MOSFET module. The current mismatch and the resulting switching loss distribution between paralleled phases will be investigated. Two different gate-drive circuit concepts will be tested. The influence of the choice of the gate-resistor arrangement will be presented regarding the...
This paper investigates the combined use of basic cell types (half and full bridges) in a Modular Multilevel Converter in order to achieve an improved MMC performance. Based on an MMC without any additional features (only considering the power transmission capability), an optimal design is presented for additional capabilities such as DC fault ride-through capability or safe operation during reduced...
In the currently predominant AC-Grid, energy reserves are provided by the inertia of rotating synchronous generators. In a potential DC-Grid, there is no such inherent energy reserve and thus additional energy storage (ES) is required to ensure grid stability. The Modular Multilevel Converter (MMC) is an emerging technology for HVDC-Grid applications and offers a convenient way of connecting ES to...
Efficient HV DC-DC converters are one key component of a future HVDC backbone grid. In this paper three promising MMC based HV DC-DC converter topologies, namely the front-to-front converter, the HVDC auto transformer and the modular multilevel DC converter are compared in terms of functionality, conversion efficiency and topology effort.
This paper proposes a new protection scheme for the HVDC circuit, which is based on the MMC topology with the double thyristor switches sub-modules. Although the MMC with double thyristor switches in each sub-module has the ability to clear the short circuit fault, the duration of AC and DC short circuit currents is not controllable. Former work solved the problem of the long duration of the AC short...
For every power semiconductor chip designer, there is a trade-off between reaching a low Vce, sat value and a low desaturation current in order to produce more ruggedness against short circuit failures. If the width of the gate channel of an IGBT is increased, there is a hidden potential that can be used to increase the conduction performance significantly at the expense of an simultaneous higher...
In this paper two tapping topologies will be compared in terms of efficiency and utilization of the installed semiconductors. Both topologies consist of a shunt connected two stage concept with a resonant DC/DC converter, followed by a medium power inverter on the low voltage side to supply an AC grid.
This paper researches the performance benefits of replacing the Si IGBTs and diodes in a power module for automotive drives with either 650 V or 900 V SiC MOSFETs. Evaluating the mean conduction and switching losses in a load profile allows a comparison of both voltage classes in order to show which class offers the lower overall losses in the given application. Furthermore, the influence on the switching...
In this paper the short-circuit robustness of state of the art SiC MOSFETs is analysed and their short-circuit behaviour is compared to that of a modern IGBT. A simplified thermal model of the chip itself is used to explain the difference between the behaviour of IGBT and SiC MOSFET under short-circuit conditions. Further, this model is used to derive the requirements for short-circuit detection methods...
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