Browsing by Author "Santos, M."
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Item Centralized control of a wave energy farm(2012-04) Santos, M.; Salcedo, F.; Tedeschi, E.; Robles, E.; Villate, J. L.; POWER SYSTEMS; RENOVABLES OFFSHORE; GENERALAs long as an increased number of Wave Energy Converters are reaching their prototypal and pre-commercial stage it is fundamental to analyse in detail the issues arising from the grid integration of such devices. Point absorbers are among the most promising Wave Energy Converters. In this paper a point absorbers wave farm, connected to a weak grid, is simulated in order to evaluate how active and reactive power control strategies can help to fulfil the grid codes and to improve the behaviour of the farm as well as the efficiency of the internal grid. The real test case offered by bimep is used to model the internal grid of the farm. Different farm level control strategies, centralized and decentralized, are considered and compared. Both steady-state and dynamic analyses are carried out in order to assess the performance of the farm under its nominal operation and also to underline the detrimental effect of the energy source intermittency. Fault analyses are performed to evaluate the effect of voltage dips on the system operation.Item Control strategies for a wave energy converter connected to a hydraulic power take-off(2011-05) Ricci, P.; Lopez, J.; Santos, M.; Ruiz-Minguela, P.; Villate, J. L.; Salcedo, F.; Falcão, A. F.D.O.; RENOVABLES OFFSHORE; POWER SYSTEMS; GENERALAmong the various types of wave energy converters currently being developed, heaving point absorbers are one of the simplest and most promising concepts. A typical efficient energy conversion system for point absorbers is based on hydraulic power take-off (PTO) systems, consisting in a double-acting cylinder, a hydraulic motor and two or more accumulators. This paper presents a simple model of a heaving oscillating buoy extracting power by means of a hydraulic system. The hydrodynamic behaviour of the absorber is modelled through application of the linear water wave theory. Apart from the basic elements listed above, the model of the hydraulic system includes leakages and pressure losses and takes into account the compressibility of the fluid. Also, possible control accumulators are considered in order to improve the performance of the hydraulic system by means of properly controlled valves. Different control variables are analysed depending on the wave inputs considered in order to improve the power extraction of the converter. The results prove that it is possible to achieve a great enhancement of the power extraction with the implementation of these control strategies and that a possible combination of some of them might be beneficial for improved efficiency of the components.Item Grid connection improvements by control strategy selection for wave energy converters(2011-05) Santos, M.; Tedeschi, E.; Ricci, P.; Molinas, M.; Martin, J. L.; POWER SYSTEMSIn this paper a wave-to-wire approach to model the exploitation of ocean energy by point absorbers in heave is presented. Attention is focused on the impact that the control strategy of the Wave Energy Converter (WEC) has both on the power performance of the single device and on the grid power quality at the connection point, when point absorbers are arranged in wave farms. Two different control strategies are proposed and compared to theoretical ones such as the complex-conjugate method. Their effectiveness in improving the system overall power extraction while reducing each Power Take-Off’s rating and easing the Wave Farm grid integration is proved by time domain simulations, developed both at single-device level and at farm level.Item Micro-grids project, Part 1: Analysis of rural electrification with high content of renewable energy sources in Senegal(2009-10) Camblong, H.; Sarr, J.; Niang, A. T.; Curea, O.; Alzola, J. A.; Sylla, E. H.; Santos, M.; Tecnalia Research & Innovation; POWER SYSTEMSAfrica is the poorest continent in the world and this poverty is linked to the lack of access to energy of its population. A big part of inhabitants live in rural zones where the lack of energy and in particular of electricity is still more flagrant. The aim of the Micro-grids project was to promote the electrification of rural regions of Senegal by the installation of micro-grids with high content of renewable energies. This paper presents some results of this project. Surveys have been carried out in three regions of Senegal to study the needs of electrical energy of non-electrified rural villages' households. These surveys have led to the estimation of electricity needs of the concerned households. The potential in renewable energies of the three regions has also been examined. It has been concluded that the solar energy potential is excellent while the wind energy potential can be interesting in some specific sites. The biomass could also be an efficient source if livestock farming was properly managed in the future. Moreover, many events have been carried out in the three regions to analyse the obstacles for the development of micro-grids in the Senegalese energy context, and to establish suitable solutions to overcome these obstacles. The results presented in this paper have been used to design a rural electrification kit which is described in another paper. Now the Micro-grids' consortium hopes to set up a new project to apply the designed kit on some rural non-electrified villages.Item Microgrids project, Part 2: Design of an electrification kit with high content of renewable energy sources in Senegal(2009-10) Alzola, J. A.; Vechiu, I.; Camblong, H.; Santos, M.; Sall, M.; Sow, G.; Tecnalia Research & Innovation; POWER SYSTEMSSenegal is one of the less developed countries in the world (position 158 in a list of 174 countries). 85% of its rural population does not have access to electricity and there's no doubt that this is an important barrier for socio-economic development. In this context, the project Microgrids aims at contributing to solve this problem. This project is part of the Intelligent Energy - Europe Programme supported by the European Commission. Its objective is the promotion and dissemination of the use of micro-grids with high content of Renewable Energy Sources (RES) for the electrification of villages far away from the grid in Senegal. One of the results of the project was the analysis of rural electrification needs, which is described in another paper [Camblong H, Sarr J, Niang AT, Curea O, Alzola JA, Sylla EH, Santos M. Microgrids project, part 1: analysis of rural electrification with high content of renewable energy sources in Senegal. Renewable Energy, submitted for publication.]. This paper presents the design of an electrification kit based on the information provided by that analysis [Analyse des besoins locaux pour l'électrification de zones rurales au Sénégal. Technical report of Microgrids project; 2007. Available from: http://www.microgrids-eie.com.]. After identifying necessary previous conditions for the sustainability of any electrification project, a methodology is proposed for the design of the electrification kit. This methodology is applied to a typical village and results are extended to differently sized villages in the areas of Thies, Fatick and Kaolack. Economic considerations are also included to establish the relationship between electrification costs and paying capability of the communities. Now the Microgrids' consortium hopes to set-up a new project to apply the designed kit on some rural non-electrified villages.Item Open access simulation toolbox for the grid connection of offshore wind farms using multi-terminal HVDC networks(Institution of Engineering and Technology, 2017) Ugalde-Loo, C. E.; Adeuyi, O. D.; Wang, S.; Liang, J.; Jenkins, N.; Ceballos, S.; Santos, M.; Vidaurrazaga, I.; D'Arco, S.; Bergna, G.; Barenys, M.; Parker, M.; Finney, S.; Gatti, A.; Pitto, A.; Rapizza, M.; Cirio, D.; Lund, P.; Castro, A.; Azpiri, I.; POWER ELECTRONICS AND SYSTEM EQUIPMENT; POWER SYSTEMS; SISTEMAS FOTOVOLTAICOSDecarbonisation of the European electricity system can become dauntingly costly due to transmission and distribution network issues arising from the integration of intermittent renewable generation sources. It is expected that wind energy will be the principal renewable source by 2050 and, as such, a number of initiatives in the academia and in the industry are being carried out to propose solutions to best accommodate the wind resource. This paper presents work carried out by DEMO 1 partners within the EU FP7 project BEST PATHS. A MATLAB/Simulink toolbox consisting of the necessary building blocks for the simulation and integration of offshore wind farms using enabling technologies such as multiterminal high-voltage direct-current grids is presented. To illustrate the toolbox capabilities, a number of system topologies is studied. System performance is assessed and measured against a set of key performance indicators. To ensure knowledge dissemination, the toolbox has been made available as open access in the BEST PATHS project website.Item Protection systems for multi-terminal HVDC grids(2018-04) Larruskain, D. M.; Valverde, V.; Torres, E.; Buigues, G.; Santos, M.; POWER SYSTEMSNowadays the protection of Voltage Sourced Converters (VSC-HVDC) is still a challenge as the high fault currents can damage seriously the converters. Nevertheless, the protection of HVDC grids is more complicated than point-to-point links, because of the specific requirements of HVDC grids. The protection system must detect and clear the faults within a demanding time. Moreover, HVDC circuit breakers are still not available, complicating the selective protection of the grid. Accordingly, since the protection of HVDC grids is so demanding, this issue is one of the biggest obstacles to develop HVDC grids. In this paper the protection system for HVDC grids is presented, including the measurement technology, fault detection and location algorithms and HVDC circuit breaker technology.Item Tuning of controllers in grid-connected multilevel converters(2012) Robles, E.; Ceballos, S.; Pou, J.; Salcedo, F.; Santos, M.; RENOVABLES OFFSHORE; POWER ELECTRONICS AND SYSTEM EQUIPMENT; POWER SYSTEMSThis paper analyzes and compares different control tuning strategies for a grid connected converter in a Back-To-Back (BTB) topology, based on Neutral Point Clamped (NPC) converters. The NPC is modeled and linearized around an operation point characterized by the DC-link voltage and the quadrature current component. In this research, a Voltage Oriented Control (VOC) strategy is used with Proportional-Integral (PI) controllers. Current and voltage control loops are tuned designing fast and simple controllers. It is evidenced that the best tuning method depends on the features of the control loop, therefore, each PI has its own tuning method. Furthermore, the nonlinearity of the DC-link voltage performance shows some particularities in the tuning of the voltage PI that make the method less direct. Finally, the results are verified through simulation models.