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In this paper we present a new dynamic multiscale model of an open-cathode Polymer Electrolyte Membrane Fuel Cell (PEMFC). The model describes two-phase water transport, electrochemistry and thermal management within a framework that combines a Computational Fluid Dynamics (CFD) approach with a micro-structurally-resolved model predicting the water filling dynamics of the electrode pores and the impact of these dynamics on the evolution of the electrochemically active surface area (ECSA). The model allows relating for the first time the cathode electrode structure to the cell voltage transient behavior during experimental changes in fuel cell temperature. The effect of evaporation rates, desorption rates and temperature changes on the performance of four different electrode pore size distributions are explored using steady-state and transient numerical simulations. The results are discussed with respect to water management and temperature control., This work is partially funded by the national project MICINNDPI2011-25649, as well as by the 7th Framework Programme of the European Commission in the context of the Fuel Cells and Hydrogen Joint Undertaking (FCH JU) through the project PUMA-MIND FP7 303419.

Paper presented at the “Fundamentals & Developments of Fuel Cells Conference 2013 (FDFC2013)”, April 16–18, 2013, Karlsruhe, Germany., The work presented in this article combines experimental analysis and theoretical studies of temperature effects on the performance of an open-cathode, self-humidified PEM fuel cell system for the design of optimal control strategies. The experimental analysis shows the great potential of improving the system performance by proper thermal management. The most significant temperature dependent parameter of the system under study is the exchange current density. On the one hand it is influenced positively by a temperature increase as this lowers the activation barrier. On the other hand a higher temperature causes a reduction of the electrochemical active sites in the cathode catalyst layer due to lower water content in the ionomer and primary pores. Dynamic models for fuel cell temperature, liquid water transport and the related electrochemistry have been developed and validated against the experiment. A cascaded Extremum Seeking control algorithm with a local PI controller is proposed to regulate the temperature to a fuel cell voltage maximum. However, the slow dynamics of the temperature related catalyst-drying effect on performance complicate the optimal thermal management with model-free control strategies., This work is partially funded by the national project MICINN DPI2011-25649, as well as by the 7th Framework Programme of the European Commission in the context of the Fuel Cells and Hydrogen Joint Undertaking (FCH JU) through the project PUMA-MIND FP7 303419. The work of P. Puleston was supported by CONICET and UNLP (Argentina), as well as Marie Curie FP7-2011-IIF, ACRES (299767/911767) (EU). Finally, the authors highly appreciate the support of the LEICI and the UNLP in enabling a research stay of S. Strahl at the laboratory in La Plata.

Presentado al 23º Congreso Argentino de Control Automático celebrado en Buenos Aires del 3 al 5 de octubre de 2012., En el presente artículo se muestra el desarrollo, implementación y resultados experimentales de un control supervisor para un sistema híbrido de generación de energía eléctrica basado en una pila de combustible tipo PEM. El núcleo de este sistema está formado por una pila de combustible tipo PEM y un banco de supercapacitores. La primera se encuentra vinculada a un bus de corriente continua mendiante un convertidor DC/DC unidireccional, mientras que los supercapacitores están conectados al bus mediante un convertidor bidireccional. El sistema se completa mediante un módulo de energía alternativa, en este caso una turbina eólica, junto con un electrolizador que genera el hidrógeno a ser utilizado por la pila de combustible. El control supervisor dise¿nando gestiona el flujo de energía garantizando que la carga conectada al bus siempre se encuentre correctamente alimentada. Por otro lado, debe asegurarse, de ser posible, de mantener cargados los supercapacitores, así como el reservorio de hidrógeno. Con estos objetivos el control supervisor es responsable de generar las referencias de potencia para cada subsistema, las cuales deben ser oportunamente satisfechas por controladores dedicados en cada uno de ellos. El esquema propuesto es implementado y evaluado experimentalmente en una estación de ensayo híbrida bajo condiciones extremas de funcionamiento., Este trabajo fue realizado con el apoyo de la Universidad Nacional de La Plata (UNLP), CONICET, y SECyT, de Argentina; con el aporte de FP7-PEOPLE-2011 Marie-Curie Action, Proyecto ACOFC (GA-293876); y por la Universitat Politècnica de Catalunya, el MICINN-CICYT proyecto DPI2011-25649, la CSIC, Programa de Investigación JAEDOC y la AECID con el proyecto A/026279/09, de España.

Presentado al 23º Congreso Argentino de Control Automático celebrado en Buenos Aires del 3 al 5 de octubre de 2012., El convertidor de CC a CC doble boost acoplado (C2B) es de interés en aplicaciones emergentes que demandan alto rendimiento y alta relación de conversión, evitando valores extremos del ciclo de trabajo de la llave. El C2B consta de dos convertidores boost en cascada, operando con una sola llave y acoplados magnéticamente a través de sus inductores. Este acoplamiento condiciona fuertemente la relación de conversión del convertidor, dada su dependencia con la corriente de carga. Se analiza su principio de funcionamiento distinguiendo cuatro modos de operación. A través de un modelo general de gran señal es posible conocer el comportamiento de la relación de conversión del convertidor con cambios de carga en diferentes puntos de operación. Estos resultados son volcados al diseño de un prototipo, legitimando el análisis en un prototipo experimental.

Presentado al Fuel Cells Science & Technology: Scientific Advances in Fuel Cell Systems celebrado en Copenague del 8 al 9 de octubre de 2008., This work proposes an experimental methodology for modeling water diffusion transport in a PEMFC, which is applied to a commercially available fuel cell stack. The effective water vapor diffusion coefficient and its dynamical variation for the stack under no load conditions will be determined for the purpose of isolating the transfer of water across the 5 layer MEA (which include the two gas diffusion layers the two catalysts layers and the membrane) in relation to temperature and membrane resistance. This coefficient is dependent on the material properties of the components in the fuel cell, as well as on the membrane temperature and water content. The dynamics of the membrane temperature and water content will be established experimentally. The controlled variables in this experiment are the water vapor partial pressures at the inlets and the temperature of the fuel cell. Experimental procedure is to independently vary the water vapor partial pressures and fuel cell temperature to obtain the water transport across the membrane, membrane resistance, and total resistance. The experimental setup for this study is based on a 21 cell PEMFC stack with a forced flow open cathode. An environmental chamber controls the fuel cell temperature and the inlet dew point temperature of the cathode reactant. The anode reactant inlet water vapor partial pressure is maintained by a membrane based humidifier which is controlled with a dew point sensor. The measured variables are the outlet dew point temperatures, membrane resistance through continual high frequency electrochemical impedance spectroscopy (EIS), and total resistance through full frequency spectrum EIS at steady state conditions. The study determines the in situ effective diffusion coefficient and membrane resistance from 10ºC to 70ºC and 10% to 100% relative humidity. The dynamics of the membrane temperature and water content will be used to determine the movement of water in the 5 layer MEA., This work was supported by the project 'Avances en el modelo y diseño de controladores para sistemas basados en pila de combustible PEM' (4800).

En aquest projecte es presenta el disseny, la implementació i la validació d’una plataforma experimental per al desenvolupament de simulacions utilitzant la tècnica PHIL (Power Hardware in the Loop). Una simulaci´o PHIL consisteix en modelar i simular un sistema elèctric en temps real mitjançant programari específic i afegir-hi en un dels seus nodes un element real on els resultats de la simulació hi seran emulats. Al mateix temps, el comportament mesurat en aquest component serà incorporat a la següent iteració de la simulació, tancant el llaç. La principal aplicació d’aquest tipus d’estudi ´es saber com afecten les possibles contingències que es poden produir en una xarxa elèctrica sobre un component del qual no es disposa d’un model matemàtic conegut i, al mateix temps, veure l’efecte que aquest element tindrà sobre la resta del sistema. Per tal de poder implementar aquesta plataforma s’ha de simular un sistema elèctric en temps real per obtenir i enviar les condicions que s’hauran d’aplicar sobre el component real. En aquest projecte s’ha utilitzat el Power Systems Simulation for Engineering (PSS®E) per a la simulaci´o i el protocol TCP/IP sobre ethernet per enviar les dades. Al mateix temps, s’han d’utilitzar convertidors d'electrònica de potència que, amb un control dissenyat adequadament, seran capaços de sintetitzar la tensió rebuda de la simulació. En aquest cas s’ha utilitzat un equip de dos convertidors VSC (Voltage Source Converter ) de 10 kVA de potència nominal en configuració back-to-back. En aquest projecte, a m'és a més de fer-se un estudi previ de les simulacions PHIL i dels seus principals components, s’han estudiat els convertidors de potència que cal emprar així com el disseny del seu control mitjançant simulacions amb el programari Matlab Simulink®. Finalment, s’ha implementat una plataforma experimental on s’han comprovat els resultats obtinguts a partir de l’estudi previ i s’han executat simulacions PHIL per comprovar-ne el seu correcte funcionament i el seu potencial per a futurs estudis.

CONAPPICE 2006 — Selected Papers Presented at the 2nd National Congress on Fuel Cells (CONAPPICE 2006), Madrid, Spain, 18-20 October 2006., This article presents the data and the description of a fuel cell stack that failed due to gasket degradation. The fuel cell under study is a 7 cell stack. The unexpected change in several variables such as temperature, pressure and voltage indicated the possible failure of the stack. The stack was monitored over a 6 h period in which data was collected and consequently analyzed to conclude that the fuel cell stack failed due to a crossover leak on the anode inlet port located on the cathode side gasket of cell #2. This stack failure analysis revealed a series of indicators that could be used by a supervisional controller in order to initiate a shutdown procedure., This work was supported by projects: 'Diseño de controladores para el proceso electroquímico en pilas de combustible de tipo PEM' (4796), 'Avances en el modelo y diseño de controladores para sistemas basados en pila de combustible PEM' (4800)., This work has been partially funded by project CICYT DPI2004-06871-C02-01, from the Spanish MEC.

Due to environmental concerns related to climate change, fiscal incentives from governments around the world, and falling prices of proved and ever-improving technology, the use of renewable energy sources has been rising considerably over the past years. A considerable amount of these sources, among which solar is to be highlighted, is used by gridconnected generators that are installed in electrical distribution systems. Solar photovoltaic generators are characterised for using an intermittent source of energy. Since they do not have any moving parts and therefore no inertia, variations in irradiance levels directly and instantaneously affect output power. Therefore, fluctuations in generated power from PV systems result in unbalancing between consumption and generation. In such context, this project aims to study the impact of high PV systems penetration in voltage and unbalance levels of electrical distribution feeders, such as percentages of unbalance and rise in pu voltage that can be expected under a certain penetration level of distributed PV generation, feeder sensitivity to photovoltaic penetration, times of the day when maximum unbalance can be expected… among others. After a literature review that defines power quality issues and the power-flow analysis method, the methodology for the analysis is presented. Two software tools, OpenDSS and MATLAB, have been integrated to program the code that is necessary to run the simulations that will provide the necessary results. The general characteristics of the resulting code are reviewed. Three types of analysis have been implemented: 1. Snapshot analyses, which provide the state of the system under certain loading conditions; 2. Feeder sensitivity to PV penetration analyses, which calculate the highest unbalance that occurs in the feeder under increasing PV penetration conditions; and 3. Time-series simulations, which use time-series solar irradiance and load data drawn from real sources to simulate realistic situations. These analyses have been performed on two very different feeders: on a smaller, 37-Bus delta-connected distribution feeder from IEEE, and on a bigger, 2998-Bus wye-connected distribution feeder from EPRI. The results of these simulations and the conclusions regarding the main objectives are then presented. Outgoing