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Garcia-Torres F.,Centro Nacional Del Hidrogeno | Bordons C.,Universidad Politecnica de Ingenieria | Vazquez S.,Universidad Politecnica de Ingenieria
Proceedings of the IEEE International Conference on Industrial Technology | Year: 2015

Microgrids appear as a key-solution to manage smart grids with high penetration of renewable energy generation and non-linear and unbalanced loads. Their flexibility allows the energy exchange with the utility network in grid-connected mode or the transition to an islanded operation mode from the main grid in case of disturbances or faults. While in grid-connected mode the main grid imposes the frequency and voltage, in the islanded mode the own microgrid must do the load balance between all the connected components to the microgrid and must supervise that the power flow inside the microgrid is done according to the power quality levels that all the devices of the microgrid require. In order to improve the power quality in these kind of applications, a novel control strategy based on Model Predictive Control (MPC) and Fourier analysis is presented in this paper applied to the voltage/frequency control of a Voltage Source Inverter (VSI). At each sample instant, the current demand in the microgrid is predicted through the estimation of the equivalent Thevenin's impedance in the microgrid. This fact allows the inverter controller to select the most appropriate gate-signal combination to maintain the reference frequency and the voltage in the microgrid. © 2015 IEEE. Source

Bordons C.,University of Seville | Garcia-Torres F.,Centro Nacional Del Hidrogeno | Valverde L.,University of Seville
RIAI - Revista Iberoamericana de Automatica e Informatica Industrial | Year: 2015

This paper deals with some issues related to optimal operation of microgrids, which are a group of loads, generators and energy storage systems that can be managed isolated or connected to the main grid, in a coordinated way in order to reliably supply electricity. The control problems and solution are addressed both for optimal dispatch and for the integration of the microgrid in the electricity market. Development of Model Predictive Controllers are presented for case studies that include several renewable sources (photovoltaic and wind) as well as hybrid storage using hydrogen. Some experimental results for a demonstration microgrid are presented, as well as simulations of scheduling in the electricity market. The results indicate that development of the appropriate controllers will allow a competitive participation of renewable energy in the new model of the electrical system. © 2014 CEA. Publicado por Elsevier España, S.L.U. Todos los derechos reservados. Source

Garcia F.,Centro Nacional Del Hidrogeno | Bordons C.,Universidad Politecnica de Ingenieria
IECON Proceedings (Industrial Electronics Conference) | Year: 2013

The transition from the current power system to a renewable energy-based smart grid will require of smaller units for managing the random aspects between the generation sources and load demand. The introduction of energy storage systems inside microgrids brings the opportunity to decide the optimal moment to purchase or sale energy to the grid. The use of different energy storage systems gives the chance to take the advantages of each system minimizing the disadvantages. © 2013 IEEE. Source

Deleebeeck L.,Technical University of Denmark | Gil V.,Technical University of Denmark | Ippolito D.,Technical University of Denmark | Campana R.,Centro Nacional Del Hidrogeno | And 2 more authors.
ECS Transactions | Year: 2015

Hybrid direct carbon fuel cells employ a classical solid oxide fuel cell together with carbon dispersed in a carbonate melt on the anode side. In a European project, the utilization of various coals has been investigated with and without addition of an oxidation catalyst to the carbon-carbonate slurry or anode layer. The nature of the coal affects both open circuit voltage and power output. Highest OCV and power densities were observed for bituminous coal and by adding manganese oxide or praseodymium-doped ceria to the carbon/carbonate mixture. Comparing the carbon black fueled performance of an anode supported (315 μm anodes) and cathode supported cell (15 μm anode) indicates a superior performance of the latter. Using un-catalyzed biomass (charcoal) as fuel results in an OCV of 941 mV and a maximum power density of 78 mW/cm2 at 755°C similar to the power output of manganese oxide catalyzed bituminous coal (73 mW/cm2). © The Electrochemical Society. Source

Amores E.,Centro Nacional Del Hidrogeno | Rodriguez J.,Centro Nacional Del Hidrogeno | Carreras C.,Centro Nacional Del Hidrogeno
International Journal of Hydrogen Energy | Year: 2014

In order to improve the production of environmental friendly hydrogen, new advanced alkaline electrolyzers must be designed to optimize their combination with renewable energies. In pursuing this goal, modeling of alkaline electrolyzers becomes a powerful design tool. In this paper is presented a mathematical model that describes the behavior of an alkaline electrolysis cell. Unlike most of the existing models in literature, the proposed model simulates the influence of both electrode/diaphragm distance and electrolyte concentration in regular operation. The role of these aspects is crucial when designing alkaline electrolyzers since the process efficiency is found to be very sensitive to them. The computations done with the model presented here were validated with in situ experimental data, reporting a great accuracy: the maximum error was around 1% from all polarization curves studied. Combination with renewable energies was also studied by introducing a solar PV profile and the error reported never exceeds 3%. The influence of the considered variables (temperature, electrode/diaphragm distance and electrolyte concentration) was quantified using sensitivity analysis. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Source

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