In this paper we present a new test bench called micro-OBIC used to characterized wide band gap semi-conductor. Micro-OBIC allows to scan an Optical Beam Induced Current (OBIC) signal with a microscopic spatial resolution. We used micro-OBIC to characterize peripheral protection such as MESA, JTE or JTE in high voltage SiC device.
This paper reports the device design, fabrication and characterisation of 10 kV-class BJT. Manufactured devices have been packaged in single BJT, two paralleled BJTs and Darlington. The static and switching characteristics of the resulting devices have been measured. The BJTs (2.4mm² active area) show a specific on-resistance as low as 198 mΩ·cm² at 100 A/cm² and room temperature for a βMax of 9.6, whereas the same active area Darlington beats the unipolar limit with a specific on-resistance of 102 mΩ·cm² at 200 A/cm² (β=11) for a βMax of 69. Double pulse tests reveal state of the art switching with very sharp dV/dt and di/dt. Turn-on is operated at less than 100 ns for an EON lower than 4mJ, whereas the turn-off takes longer times due to tail current resulting in EOFF of 17.2 mJ and 50 mJ for the single BJT and Darlington respectively when operated at high current density. Excellent parallelisation have been achieved.
Most high voltage gas circuit breakers (HVCB) in operation use SF6 as the arc interruption medium because of its high dielectric strength and good arc interruption properties. However, SF6 also displays a high global warming potential which motivates the investigation of possible alternatives to this gas.
This paper attempts a detailed comparison of some of the solutions for black start of the Offshore Wind Power Plants with Diode Rectifier based HVDC transmission.
This paper proposes an analytical methodology that allows to assess rapidly the comparison of DC-DC converters. It was applied to evaluate two modular DC-DC structures, one isolated circuit and one non isolated circuit, focusing in the variation of the operating frequency for different DC voltage transformation ratios.
he paper describes the development of a power converter small scale mock-up and a real time model of an off-shore wind farm. A Power Hardware In-the-Loop validation is proposed for a demonstration of grid architecture and control principles. The paper presents the design methodology of the PHIL test bench and underlines the contribution of PHIL in the design flow of power converter development for DC grid application. Experimental results of preliminary PHIL tests are presented.
This paper proposes a new approach to tuning voltage droop parameters in an MMC-based multi-terminal HVDC system. Using the new degree of freedom offered by the virtual capacitor control, the transient behavior of the DC voltage can be improved without adverse effects on the connected AC grids.
Modeling Modular Multilevel Converters requires a special attention due to the strong associations between the accuracy and the complexity of models on one hand and the accuracy and simulation speed on the other hand. This paper investigates different implementation techniques for MMC models and gives an overview about their development and rapidity.
Space charge accumulation on High Voltage Direct Current Gas Insulated Substations can produce electrical field reinforcements in the insulation that need to be taken into account in the equipment design. The TSM (Thermal Step Method) is one of the experimental techniques allowing to determine space charge distributions in insulating materials. However localized defects (i.e. microvoids, delaminations etc) cannot usually be detected by this technique. A new numerical approach to study the influence of structural defects on Thermal Step Method currents is proposed. The method is based on a Finite Element numerical simulation allowing to simultaneously solve electrical and thermal equations. The effect of three different defects were studied. It results that ring defects, with diameters smaller than 0.4 mm, produce less than 10% of change on TSM current signals. This confirms the difficulty to detect small defects by this method. It was also observed that delaminations can produce variations in signal as high as 70%, and even generate signals of opposing sign from the case without defect.
This paper deals with creeping discharges propagating over solid insulator samples in presence of a fluoronitrile mixture consisting of 10% of fluoronitrile and 90% of CO2, under positive and negative standard lightning impulse voltages, in point-plane geometry. The solid samples used are disks made of filled epoxy resin used for real GIS insulators. The experimental results are compared with those obtained with SF6 at pressure ranging 0.1 to 0.3 MPa, while the pressure of fluoronitrile mixture is chosen to match an equivalent dielectric strength of SF6. Different characteristic parameters are investigated namely the maximum length of creeping discharges versus the gas/mixture pressure and voltage polarity. In SF6, two regimes of discharges that depend on the voltage polarity are evidenced. Under positive impulse, the mixture presents similar properties as SF6. However, under negative polarity the maximum discharge length in SF6 is much longer than in the fluoronitrile mixture.
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