During the short circuit of a vertical 4H-SiC power MOSFET, a high gate current starts to flow through the gate dielectric. We demonstrate that the Schottky emission is the main physical mechanisms.
Multicell converters were introduced ten years ago and, over this period, their properties have been thoroughly analyzed. Since then, this concept has lead to some other innovative topologies which ...are briefly presented in this paper. Different ways to introduce soft switching in multicell converters are investigated. The concept of distributing power over several switches, giving more degrees of freedom and using less passive components, is extended further with the stacked multicell topology. Finally, direct AC-AC converters using the multicell approach are described.
The aim of this paper is to explain the intrinsic short-circuit tolerance of an IGBT multicell inverter when a commutation failure occurs. Such a failure may either be a wrong gate voltage ...(malfunctioning of the driver board, auxiliary power supply failure, dv/dt disturbance) or an intrinsic IGBT failure (over-voltage/avalanche stress, temperature overshoot). IGBT stresses are studied and show that no opening of the bonding can appear and consequently no risk of explosion. That is why, owing to the imbricated cells structure, an IGBT short-circuit failure may be withstood for a few switching periods, with nevertheless nonoptimized output waveforms. The design, the lab-test of a sensor able to perform monitoring as well as the failure diagnosis are also presented. This real-time diagnosis allows either a safe stop or a remedial control strategy based on the reconfiguration of the PWM modulator. The reconfiguration strategy enables decrease of internal stresses and optimization of the output shape. A fail-safe operating may be gained for high power applications.
The test and the characterization of medium or high-power electronic converters, under nominal operating conditions, are made difficult by the requirement of high-power electrical source and load. In ...addition, the energy lost during the test may be very significant. The opposition method, which consists of an association of two identical converters supplied by the same source, one operating as a generator, the other as a receptor, can be a better way to do these test. Another advantage is the possibility to realize accurate measurements of the different losses in the converters under test. In the first part of this paper, the characteristics of the method concerning loss measurements are compared to those of the electrical or calorimetric methods, then it is shown how it can be applied to different types of power electronic converters, choppers, switched mode power supplies, and pulsewidth modulation inverters. In the second part, different examples of studies conducted by the authors, and using this method, are presented. They have varying goals, from the test of soft-switching inverters to the characterization of integrated gate-commutated thyristor (IGCT) devices mounted into 2-MW choppers.
Multilevel converters have many power devices and drivers. Thus, a direct reliability calculation based only on the first failure occurrence on one of the components clearly leads them to be devalued ...compared to two-level converters. However, taking into account that symmetrical multilevel converters such as the X -level active neutral point clamped (ANPC) family are based on imbricated and/or stacked switching cells on the one hand, with an additional center tap at the dc bus in three-phase operation on the other hand, several redundancies clearly appear which can be managed to increase the global reliability. For the first time, a general and theoretical methodology used to calculate reliability laws and failure rates and applied to compare two-, three-, and five-level topologies is proposed. Results show that the fault handling of three- and five-level three-phase topologies permits a great increase in reliability over a "relatively" short time duration, in addition to other benefits.
The power characteristics of wind turbines are nonlinear. It is particularly true for vertical-axis turbines whose provided power is very sensitive to the load. Thus, controlling the operating point ...is essential to optimize the energetic behavior. Several control strategies (maximum power point tracking) can be used for the energy conversion. If the wind-turbine characteristic C p (lambda) is supposed to be a priori known, it can be used for optimal control of the torque, speed, or system output power. On the contrary, if this characteristic is unknown, an operational seeking algorithm such as fuzzy logic has to be implemented. Several structures with different associated complexity degrees can be used, in particular, the structure of the ac-dc conversion, which can be either a pulsewidth-modulation voltage-source rectifier or a simple diode bridge. A comparative study of the corresponding control strategies and architectures is proposed in this paper regarding the tradeoffs between structure complexity and energy efficiency. The analysis is based on simulations and experiments
This paper proposes SiC MOSFET gate ageing-laws under repetitive short-circuit stress. Based on analytical studies, physical forms and preconditioning data, numerical fitting based on stress ...variables ΔTj, TPulse Gate Damage % and Esc is proposed. Accuracy and prediction capabilities of ageing-laws have been evaluated and compared. Resulting in suggesting a new ageing-law based on ΔTAl_Top metal-source. This one gives the best fitting accuracy. Finally, the ageing-law based directly on the short-circuit energy Esc appears to have the best in prediction capability.
This paper presents an experimental study on the ageing of insulated-gate bipolar transistor (IGBT) power modules. The aim is to identify the effects of power cycling on these devices with high ...baseplate temperatures (60 °C to 90 °C) and wide temperature swings (60 °C to 100 °C). These values for thermal stresses have been defined according to automotive applications. The test conditions are provided by two types of test benches that will be described in this paper. The changes in electrical and thermal indicators are observed regularly by a monitoring system. At the end of the test (reaching damage criterion or failure), different analyses are performed (acoustic scanning and SEM imaging), and the damage is listed systematically. Nineteen samples of 600-V 200-A IGBT modules were thus aged using five different power-cycling protocols. The final summary of results shows that ageing mechanisms mainly concern wire bonds and emitter metallization, with gradual impact depending on protocol severity.
Fault management of multicell converters Turpin, C.; Baudesson, P.; Richardeau, F. ...
IEEE transactions on industrial electronics (1982),
10/2002, Letnik:
49, Številka:
5
Journal Article
Recenzirano
Component counts and oversimplified reliability rules may lead to the conclusion that multilevel converters are less safe than two-level converters, just because they use more components. A better ...approach might be to consider that they use a different arrangement of components and also that the consequence of faults may be very different. This paper is focused on the study of the consequences of faults in hard-switching and soft-switching multicell converters. Solutions to minimize the consequences of major faults are described.
The purpose of this paper is to present a complete analysis of the gate leakage-current behaviour during short-circuit (SC) fault operation of 1200V SiC MOSFETs from five different manufacturers ...including planar and trench-gate structures. Ruggedness and gate leakage level are evaluated in function of the chip size. Finally, the gate leakage current is modelled and the robustness tested.
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