Circuit-type modelling of SiC power Mosfet in short-circuit operation including selective fail-to-open and fail-to-short modes competition

International audienceSiC Mosfet has very unique properties in extreme operation such as a well-known fail-to-short failure mode but in competition with a lesser known fail-to-open failure mode. These two modes are generally studied and modelled separately, whereas, in practice, they are coupled with the junction temperature of the chip. This paper presents a circuit-type modelling approach of these two modes simultaneously. This modelling allows to simulate the selectivity and competition between these two modes, one is clearly critical and the other is advantageously safe. The proposed model is then compared with short-circuit test of 1.2kV-80m MOSFET SiC

Gate leakage-current analysis and modelling of planar and trench power SiC MOSFET devices in extreme short-circuit operation

International audienceThe 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

Fault-tolerant inverter for on-board aircraft EHA

International audienceIn more-electrical aircraft, most of the flight surfaces are equipped with electro-hydrostatic actuators. A high reliability is mandatory, combined to fault-handling strategies for the VS inverter, which is a part of crucial importance of this equipment, controlling the power flows and the performances. The proposed topology uses a safe fourth-leg connected to the star tap of a standard PMSM winding. Fault-handling IGBT drivers and isolating AC switches are introduced in series with all the legs so as to confine a local inverter fault and to manage the post-fault operation. A modular and versatile design is proposed, based on a generic set of two legs including a local over-current / temperature monitoring and an optional self isolation capability under fault. In this paper, the authors present a complete lab test-bench, the DSP-FPGA digital control including a state chart and finally results in post-fault two-phase reconfiguration

Evaluation of High Power Converters by the Opposition Method

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Fault management of multicell Converters

International audienceComponent 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

Fail-safe capability of a high voltage IGBT inverter source

The aim of this paper is to explain the intrinsic fail-safe capability of a high-voltage IGBT inverter source. The inverter is an imbricated cells structure which provides redundancy. The major failures can be either 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). The IGBT failures are studied and show that no opening of the bondings can appear and consequently no risk of explosion. Owing to the imbricated cells structure, an IGBT failure can be withstand a few switching periods, with nevertheless non-optimized output waveforms. The design and the lab-test of a sensor able to perform monitoring and failure diagnosis are also presented. This real-time diagnosis allows either a safety stop or a remedial control strategy based on the reconfiguration of the control signals. The real-time reconfiguration allows to decrease internal stresses and to optimize the shape of the output voltage. In this case, a fail-safe operating may be gained for high power applications

A ZVS Imbricated Cell Multilevel Inverter with Auxiliary Resonant Commutated Poles

International audienceThe imbricated-cell multilevel converter is well suited to high power applications. It allows the series connection of n switches with natural voltage sharing between these switches enabled through the connection of n-1 flying capacitors. This paper deals with the application of soft-switching on this topology; to date, only the hard-switching mode has been studied. The use of soft switching enables an increase of the switching frequency (resulting in the size reduction of the flying capacitors) without a decrease of the converter efficiency. Of the soft switching methods considered, the Auxiliary Resonant Commutated Pole (ARCP) technique was chosen due to the relative ease in which it can be incorporated into the converter topology. Furthermore, this technique offers numerous advantages: loss reduction, no added stress to the switches and compatibility with PWM control. The main properties of the ARCP multicell converter are the same as the hard-switched topology: an increase of the apparent output switching frequency and natural self-balancing of the flying-capacitor voltages. This paper presents the results of both simulations performed and measurements taken from an experimental set-up in order to study the viable system functioning. The introduction of soft-switching strongly complicates the theoretical study of the balancing mechanisms, however. As a result, the authors depend on simulations to validate the natural balancing effect during soft switching. Lastly, a general method of loss measurement is presented. Results show that the converter losses are reduced by at least 30%

Switching faults and safe control on an ARCP multicell flying capacitor inverter

International audienceThe auxiliary resonant commutated pole (ARCP) multicell converter is a soft-switched variant of the multicell converter. It is shown in this paper that the ARCP technique can be very efficiently used in multicell flying capacitor converters. The main properties of the resulting soft switching multicell converter are very similar to those of the hard-switched version. They are presented and validated by simulations as well as experimental results. In practice, due to the damping, the ARCP multicell converter can suffer from switching faults as in two-level ARCP inverters, but in the case of a multicell converter failures can occur in different cells. So, the main control strategies are evaluated and the switching process is discussed step by step, taking account of the main imperfections of actual control circuits. When they can occur, the switching faults are described and analyzed. Finally, an original quasisoft switching control that should give a high safety of operation is proposed. Experimental results obtained with a 900 V-100 A ARCP multicell inverter leg are given and the performances are compared with those of a hard-switched multicell inverter leg of the same rating