Tag Archives: Wave Dragon

Medium-voltage power converter interface for Wave Dragon wave energy conversion system


Muller, N., Kouro, S., Glaria, J., and Malinowski, M. – 2013 IEEE Energy Conversion Congress and Exposition (ECCE), September 2013

Abstract

This paper presents a medium-voltage power converter system for the Wave Dragon ocean energy conversion platform. The proposed converter configuration is an alternative to the classic back-to-back low voltage converter implemented in the original prototype. The converter configuration merges several diode rectifiers with boost converters operating with low voltage at the generators side, with a single neutral point clamped converter (NPC) operating at medium-voltage at grid side. The control schemes for generator and grid side converters are analyzed, and simulation results are presented as preliminary validation. The proposed configuration provides a simple and cost-effective interface for wave energy conversion systems with several generators, such as Wave Dragon.

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Experimental Update of the Overtopping Model Used for the Wave Dragon Wave Energy Converter


S. Parmeggiani, J.P. Kofoed, and E. Friis-Madsen – Energies, April, 2013

Abstract

An overtopping model specifically suited for Wave Dragon is needed in order to improve the reliability of its performance estimates. The model shall be comprehensive of all relevant physical processes that affect overtopping and flexible to adapt to any local conditions and device configuration. An experimental investigation is carried out to update an existing formulation suited for 2D draft-limited, low-crested structures, in order to include the effects on the overtopping flow of the wave steepness, the 3D geometry of Wave Dragon, the wing reflectors, the device motions and the non-rigid connection between platform and reflectors. The study is carried out in four phases, each of them specifically targeted at quantifying one of these effects through a sensitivity analysis and at modeling it through custom-made parameters. These are depending on features of the wave or the device configuration, all of which can be measured in real-time. Instead of using new fitting coefficients, this approach allows a broader applicability of the model beyond the Wave Dragon case, to any overtopping WEC or structure within the range of tested conditions. Predictions reliability of overtopping over Wave Dragon increased, as the updated model allows improved accuracy and precision respect to the former version.

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Experimental Study Related to the Mooring Design for the 1.5 MW Wave Dragon WEC Demonstrator at DanWEC


S. Parmeggiani, J.P. Kofoed, and E. Friis-Madsen – Energies, April, 2013

Abstract

The paper presents the results of an experimental study identifying the response of a 1.5 MW Wave Dragon to extreme conditions typical of the DanWEC test center. The best strategies allowing for a reduction in the extreme mooring tension have also been investigated, showing that this is possible by increasing the surge natural period of the system. The most efficient strategy in doing this is to provide the mooring system with a large horizontal compliance (typically in the order of 100 s), which shall be therefore assumed as design configuration. If this is not possible, it can also be partly achieved by lowering the floating level to a minimum (survivability mode) and by adopting a negative trim position. The adoption of the design configuration would determine in a 100-year storm extreme mooring tensions in the order of 0.9 MN, 65% lower than the worst case experienced in the worst case configuration. At the same time it would lead to a reduction in the extreme motion response, resulting in heave and pitch oscillation heights of 7 m and 19° and surge excursion of 12 m. Future work will numerically identify mooring configurations that could provide the desired compliance.

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