Nos publications scientifiques
Power Hardware In-the-Loop validation of DC-DC power converter for offshore wind energy
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.
Tuning of Droop Parameters Using Virtual Capacitor Control to Improve Voltage Dynamics
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.
Comparaison and assessment of implementation techniques for dynamics MMC type models
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.
Numerical modelling and influence of defects on space charges in epoxy resin under HVDC stresses
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.
Characteristics of creeping discharges along epoxy surface in fluoronitrile/co2 gas mixture under lightning impulse
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.
Study of convective condensation in a thermosiphon loop
In this article, we focus on the condenser of a loop thermosiphon designed to cool power electronic component. The objective here is to condense Novec 649, our chosen working fluid for this loop. It is a fluid recently developed by 3M, which is known for having low environmental impact and non-flammable. We first present a theoretical analysis with the calculation and the hypotheses leading to the design of the multi-tubular condenser. Then we present a full size thermosiphon built for experimental validation. A discussion then addresses some of the design hypotheses. Three main parameters are studied : the tilting angle of the condenser (from horizontal to vertical orientations), the temperature of the coolant and finally the mass flow effect at different saturation temperatures. In our setup, we dissipate up to 2.4 kW at the evaporator level. The produced vapor is then condensed in the heat exchanger using cold water flowing at countercurrent. A number of measurements are made via thermocouples and pressure sensors located at both ends of the condenser to measure the average heat exchange coefficient.
Electro-thermal simulation methodology for HVDC cable GIS termination
This paper presents a simulation methodology that can be used to evaluate the electric stresses in GIS/cable termination under different operating conditions including polarity reversal and superimposed impulses.
Follow up of space charge distributions in HVDC cable during a Pre-Qualification test using the Pulse ElectroAcoustic technique and the Thermal Step Method
In order to better understand the evolution of space charge and electric field distortions during the application of electro-thermal stresses to a HVDC cable system, the present paper shows the follow up of periodic space charge characterizations on a HVDC cable during part of a Pre-Qualification test using both the Pulse ElectroAcoustic technique and the Thermal Step Method. The focus is on the evolution of space charges distributions during load cycles and high load sequences according to the Cigré TB496 recommendation.
Development and Set-up of a Non-intrusive Technique for measuring Space Charges in Specimens of dc cables
This paper presents a procedure for designing a power converter to produce power pulses in the conductive parts of a cable (core or shield) for non-invasive space charge measurements with a thermal wave.
Pole-to-ground fault protection strategy for HVDC grids under symmetrical monopolar configuration
An experimental study of breakdown and pre-breakdown phenomena in liquid nitrogen (LN2) is performed in this paper, in order to provide useful knowledge for the design of high voltage superconducting systems.
