Liquid spray injection in the expansion volume of a CO2 high voltage circuit breaker
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.
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.
Influence of the operating frequency on DC-DC converters for HVDC grids
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.
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.