Browsing by Author "Villate, Jose Luis"
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Item Adaptive simulation of unsteady flow past the submerged part of a floating wind turbine platform(International Center for Numerical Methods in Engineering, 2015) Jansson, Johan; Nava, Vincenzo; Sanchez, Miren; Aguirre, Goren; De Abreu, Rodrigo Vilela; Hoffman, Johan; Villate, Jose Luis; Muscari, Roberto; Broglia, Riccardo; Salvatore, Francesco; RENOVABLES OFFSHORE; Tecnalia Research & Innovation; GENERALOffshore floating platforms for wind turbines represent challenging concepts for designers trying to combine an optimal compromise between cost effectiveness and performance. Modelling of the hydrodynamic behaviour of the structure is still the subject of wide debate in the technical communities. The assessment of the hydrodynamics of the support structure is not an easy task as the floaters consist of an assembly of columns, braces and pontoons, commonly also with heave plates: Each of these components corresponds to a different hydrodynamic model and it further interacts with the other elements. This results in very complex non-linear modeling, which makes it necessary to resort to computational fluid dynamics (CFD) methods for the evaluation of the combined hydrodynamics. In the framework of the collaboration between the Basque Centre for Applied Mathematics (BCAM) and Tecnalia R&I, the interaction of the sea flow with a semisubmersible floating offshore wind platform have been calculated by using the open source solver Unicorn in the FEniCS-HPC framework when subject to a steady inflow. The prototype of the platform consists in a semi-submersible 4-columns column stabilized platform - NAUTILUS Floating Solutions concept-; columns are connected by a rigid ring pontoon provided with heave damping plates at the bottom. The novelty of the approach in FEniCS-HPC hinges upon an implicit formulation for the turbulence, a cheap free slip model of the boundary layer and goal-oriented mesh adaptivity [8, 6, 9, 20, 1]. We find that the results are consistent with experimental results for cylinders at high Reynolds number.Item A comprehensive study of a hybrid modulation technique for the neutral-point-clamped converter(2009) Zaragoza, Jordi; Pou, Josep; Ceballos, Salvador; Robles, Eider; Ibáñez, Pedro; Villate, Jose Luis; POWER ELECTRONICS AND SYSTEM EQUIPMENT; GENERALThis paper presents a hybrid modulation technique for the three-level neutral-point-clamped converter. A modulation strategy, based on two modulation signals per phase, was presented previously. This strategy completely removes the low-frequency voltage oscillations that appear at the neutral point (NP) in some operation conditions. However, it also has a major drawback: it significantly increases the switching losses of the converter. The proposal in this paper combines such a modulation strategy with sinusoidal pulsewidth modulation (SPWM). The main characteristic of this hybrid modulation is the reduction in switching losses at the cost of some low-frequency voltage oscillations at the NP. The amplitude of these oscillations can be controlled by varying the combination of the two strategies. The performance of the hybrid modulation is analyzed and compared with the original strategies. Power losses and oscillation amplitudes on the dc-link capacitors are evaluated. Experimental results show how the hybrid modulation performs by balancing the dc-link capacitors.Item The development of technology evaluation protocols for the equitable evaluation of marine renewable energy converters(2010) Ingram, David; Smith, George H.; Villate, Jose Luis; Jonstone, Cameron; Ferreira, Claudio Bittencourt; GENERALItem Experimental validation of multilevel converters for variable speed wind turbines(IEEE Computer Society, 2005) Villate, Jose Luis; Ceballos, Salvador; Robles, Eider; Ibañez, Pedro; Gabiola, Igor; GENERAL; POWER ELECTRONICS AND SYSTEM EQUIPMENT; RENOVABLES OFFSHORE; SGWind energy is undergoing a rapid development in size and capacity. Multilevel converters show interesting advantages in this field, such as high efficiency and low harmonic distortion. This work is focused on the analysis of these two features offering experimental results which verify the improvement of this kind of converters on the traditional two level topologies. Finally, we describe an experimental test bench where we intend to continue the validation of other features of multilevel converters such as performance under voltage sags and wind speed variations.Item Global review of recent ocean energy activities(2013) Melo, Ana Brito; Sweeney, Eoin; Villate, Jose Luis; GENERALOcean energy is regarded as an important future source of energy generation in many countries for transition to a low-carbon future. While commercial interest in ocean energy is growing significantly at a global level, there are considerable investment costs and bottlenecks that will need to be overcome. Research and funds are spread over many different wave and marine current energy concepts under development, and there is still no technology convergence, in contrast to what happened in wind energy. Although an important marine energy resource, discussion of offshore wind energy is not included in this manuscript. This article focuses on the latest developments in ocean energy-in particular, open-sea testing facilities set up by several countries as a measure to encourage deployment and streamlining procedures-and gives an overview of projects going into the water this past year. In addition, the article highlights the importance of collaborative research and development on ocean energy projects and the unique role of the Ocean Energy Systems Implementing Agreement as an intergovernmental organization promoting the use of ocean energy (wave, marine currents, tidal, ocean thermal gradients and salinity gradients) for energy extraction.Item Hybrid modulation technique for the neutral-point-clamped converter(2007) Zaragoza, Jordi; Pou, Josep; Ceballos, Salvador; Villate, Jose Luis; Gabiola, Igor; POWER ELECTRONICS AND SYSTEM EQUIPMENT; GENERALThis paper presents a hybrid modulation technique for the three-level neutral-point-clamped converter. A modulation strategy that was presented previously is able to remove completely the lowfrequency voltage oscillations that appear on the neutral point for some operation conditions. However, such a modulation strategy has an important drawback; it increases significantly switching losses on the converter. The hybrid modulation proposed here combines such a modulation with sinusoidal PWM. The main characteristic of this hybrid modulation is the capacity to reduce switching losses at the cost of having some low-frequency voltage oscillations on the neutral point. The amplitude of these oscillations can be controlled thanks to the degree of mixture between the two strategies. Performance of the hybrid modulation is analyzed in this paper and compared with the original strategies. Switching losses are evaluated by simulation, and some experimental results show how the hybrid modulation performs with balancing the dc-link capacitors.Item Hybrid modulation technique for the neutral-point-clamped converter(2007) Zaragoza, Jordi; Pou, Josep; Ceballos, Salvador; Villate, Jose Luis; Gabiola, Igor; POWER ELECTRONICS AND SYSTEM EQUIPMENT; GENERALThis paper presents a hybrid modulation technique for the three-level neutral-point-clamped converter. A modulation strategy that was presented previously is able to remove completely the low frequency voltage oscillations that appear on the neutral point for some operation conditions. However, such a modulation strategy has an important drawback; it increases significantly switching losses on the converter. The hybrid modulation proposed here combines such a modulation with sinusoidal PWM. The main characteristic of this hybrid modulation is the capacity to reduce switching losses at the cost of having some low-frequency voltage oscillations on the neutral point. The amplitude of these oscillations can be controlled thanks to the degree of mixture between the two strategies. Performance of the hybrid modulation is analyzed in this paper and compared with the original strategies. Switching losses are evaluated by simulation, and some experimental results show how the hybrid modulation performs with balancing the dc-link capacitors.Item Influence of a sensorless algorithm position estimation error on the control of a Doubly Fed Induction Machine(2007) Kortabarria, Iñigo; De Alegría, Iñigo Martínez; Andreu, Jon; Martín, José Luis; Villate, Jose Luis; GENERALParameter variations, model inaccuracies and noise in measurements introduce rotor position estimation errors in sensorless algorithms in Doubly Fed Induction Machines. Depending on the chosen control algorithm, these position estimation errors may generate important errors on the control of active power and reactive power of the Doubly Fed Induction Machine. This paper presents a vector control method on stator flux reference frame able to compensate position estimation errors in the sensorless algorithm.Item Measuring progress towards ocean energy commercialisation(2023-11) Ruiz-Minguela, Pablo; Wong, Pui Wah; Noble, Donald R.; Jeffrey, Henry; Villate, Jose Luis; RENOVABLES OFFSHORE; GENERALThe EU aims to achieve climate neutrality by 2050 through the European Green Deal and its commitment to global climate action under the Paris Agreement. Transitioning to a carbon-neutral society requires increasing the share of renewable energy across different sectors. Ocean energy can contribute to job creation, economic revitalization, and grid balancing. However, public funding and financial instruments are necessary to reduce risks, advance technology, and to support demonstration and pre-commercial projects in the ocean energy sector. The SEETIP Ocean project, supported by the European Commission through the Horizon Europe framework programme, aims to accelerate the deployment of the ocean energy sector by promoting collaboration among stakeholders. As part of the project, an analysis is being conducted to assess technological progress, identify implementation gaps, and update the Strategic Research and Innovation Agenda (SRIA) for Ocean Energy. The analysis reveals reasonable progress in research and innovation, albeit with smaller project sizes compared to current SRIA recommendations, and the need for increased support from national programmes. Some topics have been covered more than proposed funding and number of projects, while others not at all. This highlights the need for effective communication and collaboration between both the European Commission and Member State funders and their programmes. In addition, public support and funding is crucial to lower investment risks and propel ocean energy technologies towards commercialisation. With appropriate funding and policy support, the European ocean energy sector could strengthen its position as a worldwide leader and harness the socio-economic benefits from the sector.