http://hdl.handle.net/2117/114 2013-05-24T07:21:02Z http://hdl.handle.net/2117/19230 Title: Analyses of energy management strategies for a PEMFC/UC electric vehicle Authors: Bethoux, Olivier; Remy, G.; Riera Colomer, Jordi; Serra, Maria; Azib, T. Abstract: In this paper, two energy management strategies considering the hydrogen consumption of hybrid power sources using a PEM Fuel Cell (FC) and Ultracapacitors (UC) are described and compared. First, the Hybrid Electric Vehicle (HEV) architecture and the associated models with their control strategies are described. The two energy management strategies are evaluated based on the Energetic Macroscopic Representation (EMR). The comparison focuses on the global efficiency of the power sources energy management. In particular, a proposed strategy is to manage the UC State-OfCharge while stabilizing the FC around its maximal efficiency point. Finally, some simulations on a Fuel Cell / Ultracapacitors HEV show the differences between the compared control strategies. 2013-05-15T08:37:51Z http://hdl.handle.net/2117/19009 Title: Experimental analysis of a degraded open-cathode PEM fuel cell stack Authors: Strahl, Stephan; Gasamans Rodríguez, Noemí; Llorca Piqué, Jordi; Husar, Attila Peter Abstract: The well-known challenges to be overcome in PEM fuel cell research are their relatively low durability and high costs for the platinum catalysts. Thus, this work focuses on factors that impact durability and the links to the fuel cell performance. Therefore a degraded, open-cathode, 20-cell, PEM fuel cell stack, which was used in a laboratory test station for characterization experiments, was analyzed experimentally. Voltage transients during external perturbations, such as changing temperature, humidity and stoichiometries show that degradation affects individual cells quite differently throughout the lifetime of the stack. Electrochemical impedance spectroscopy (EIS) data presents non-reversible catalyst layer and membrane degradation of several cells. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) are in progress in order to validate the results of the electrical analysis and elucidate catalyst and membrane degradation. 2013-04-26T12:04:59Z http://hdl.handle.net/2117/18447 Title: Diseño de un convertidor CC-CC doble boost acoplado Authors: González, Sergio; Puleston, Paul; Fossas Colet, Enric Abstract: 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. 2013-03-20T17:35:55Z http://hdl.handle.net/2117/18284 Title: Diseño e implementación de un control supervisor para sistemas híbridos de generación basado en pilas de combustible Authors: More, J.J.; Puleston, Paul; Kunusch, Cristian; Riera Colomer, Jordi Abstract: 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 mediante un convertidor DC/DC unidireccional, mientras que los supercapacitores están conectados al bus mediante un convertidor bidireccional. E l 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 diseñando 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. 2013-03-13T17:38:29Z http://hdl.handle.net/2117/18129 Title: Modeling a coupled-inductor boost converter in the complementarity framework Authors: Carrero Candelas, Niliana Andreina; Batlle Arnau, Carles; Fossas Colet, Enric Abstract: We consider the modeling of switching circuits, consisting of passive elements, independent sources, which are subject both to externally induced switches (time events) and to state events. We focus on the use of the complementarity formalism for obtaining such hybrid (actually piecewise linear) models, assuming idealized current- voltage characteristics of the diodes and switches. In particular, a coupled-inductor Boost converter is modelled as a piece-wise complementarity system. We obtained also a discrete-time model which may be used for design and simulation purposes. In order to show the good performance of the model obtained, it is compared with the model of the converter obtained from the PSIM simulation software. 2013-03-07T12:59:39Z http://hdl.handle.net/2117/17923 Title: Distributed parameter model simulation tool for PEM fuel cells Authors: Sarmiento Carnevali, María Laura; Serra, Maria; Batlle Arnau, Carles Abstract: En este trabajo se ha desarrollado una herramienta de simulación para pilas de combustible tipo PEM, basada en un modelo de parámetros distribuidos. La herramienta está diseñada para realizar estudios de variaciones espaciales y temporales a lo largo de los canales de alimentación de reactantes. El trabajo muestra y analiza los resultados de simulación de una monocelda monocanal. Las variables estudiadas son las concentraciones de los reactantes, presiones, temperaturas, humidificación, contenido de agua de la membrana, corriente, entre otras que influyen significativamente sobre el rendimiento y durabilidad de las pilas PEM. 2013-02-22T10:19:50Z http://hdl.handle.net/2117/17811 Title: On the stability of discrete-time active damping methods for VSI converters with a LCL input filter Authors: Orellana Barceló, Marcos; Griñó Cubero, Robert Abstract: The use of LCL filters with VSI converters is interesting since they present good attenuation of current ripple at high frequencies. Nevertheless, they also present a high resonance peak which can cause undesired oscillations, and even instability problems. Passive and Active Damping are methods which try to reduce those resonance effects. In this paper, Passive Damping is briefly reviewed and Active Damping is formally analyzed in continuous-time and, specially, in discrete-time. It will be shown that the one period delay included in sampled-data control systems and the grid impedance play a very important role in stability conditions. The presented results are useful to design discrete-time Active Damping controllers. Moreover, important implications for higher level controls can be deduced since the Active Damping is the first control loop in the power converter's controller. 2013-02-18T10:06:12Z http://hdl.handle.net/2117/17761 Title: Design of linear controllers applied to an ethanol steam reformer for PEM fuel cell applications Authors: García, Vanesa Mariel; Serra, Maria; Llorca Piqué, Jordi; Riera Colomer, Jordi Abstract: This paper focuses on the design of a controller for a low temperature ethanol steam reformer for the production of hydrogen to feed a Protonic Exchange Membrane (PEM) fuel cell. It describes different control structures for the reformer and treats the control structure selection of this Multiple Input Multiple Output (MIMO) system. For each control structure, decentralised 2x2 controllers are implemented and a Proportional Integral (PI) control action is implemented in each control loop. The PI parameters are tuned and the performance of the different linear controllers is compared though simulation. For the evaluation of the proposed controllers, the response time for different initial conditions and changes in the references is analysed, as well as the behaviour of the controlled system in front of disturbances. 2013-02-14T12:25:53Z http://hdl.handle.net/2117/17705 Title: Influencia de los parámetros de diseño de un inversor fotovoltaico en la estabilidad de una microred Authors: Rodríguez Villarreal, José Raúl; Biel Solé, Domingo; Guinjoan Gispert, Francisco Abstract: El incremento de la generación de energía distribuida en la red eléctrica ha despertado inquietudes respecto a la estabilidad de la misma. Los generadores fotovoltaicos conectados a la red eléctrica tienen que lidiar con variaciones en el consumo y la generación en la red, esto puede afectar el desempeño y la estabilidad de los generadores y de la red. Este documento presenta el efecto de los par´ametros de un generador fotovoltaico y la relación generación/consumo en la estabilidad de una microred. Además, se ajusta la ganancia del controlador de corriente del generador en función del consumo con el fin mantener la estabilidad de la microred para diferentes escenarios de generación/consumo. 2013-02-13T10:37:59Z http://hdl.handle.net/2117/17580 Title: Repetitive control for systems with time-delays and application to robotic servo motor Authors: Na, Jing; Ren, Xuemei; Costa Castelló, Ramon; Griñó Cubero, Robert; Guo, Y. Abstract: In many industrial robotic applications there is a need to track periodic reference signals and/or reject periodic disturbances. This paper presents a novel repetitive control design for systems with constant time-delays in both forward and feedback control channels. An additional delay is introduced together with plant delays to construct an internal model for periodic signals, and a simple proportional control is utilized to stabilize the closed-loop system. Sufficient stability conditions of the closed-loop system and the robustness analysis under modeling uncertainties are studied. Experimental results are included to evaluate the validity and effectiveness of the proposed method. 2013-02-05T12:41:32Z http://hdl.handle.net/2117/17577 Title: Analysis and design of a robust odd-harmonic repetitive controller for an active filter under variable network frequency Authors: Ramos Fuentes, Germán Andrés; Costa Castelló, Ramon; Olm Miras, Josep Maria Abstract: Frequencyvariationsintheelectricalnetworkmaycauseadramaticperformancedecayinrepetitive controlledactivefiltersintendedtoremoveodd-harmonicdistortioninsingle-phaseACloads.This work presentsanodd-harmonicrepetitivecontrollerforashuntactivepowerfilterthataddressessuch a performanceproblem.Thisisachievedbymeansofanadaptivechangeofthesamplingperiodofthe digitalcontroller.However,thisactionimpliesstructuralchangesthatmayresultinanoverall destabilizationoftheclosed-loopsystem.Hence,asmall-gaintheorem-basedrobustcontroldesign techniqueallowstoobtainacontrollerwhichassuresBIBOstabilityintherequiredsamplingperiod interval.Experimentalresultsvalidatetheproposal. 2013-02-05T10:44:08Z http://hdl.handle.net/2117/17575 Title: An educational approach to the internal model principle for periodic signals Authors: Costa Castelló, Ramon; Olm Miras, Josep Maria; Vargas, Hector; Ramos Fuentes, Germán Andrés Abstract: This article presents an educational approach to resonant control and repet- itive control, which are Internal Model Principle-based control techniques speci cally de- signed for the tracking/rejection of periodic signals. The analytical formulation is com- pleted by a set of simulations and physical experiments on a mechatronic educational plant integrated in a virtual/remote laboratory. The laboratory features are oriented to realize the limited performance of classic PID control to reject non-constant disturbances and, at the same time, to show the effectiveness of the Internal Model Principle for the rejection of periodic disturbances by means of resonators and repetitive control. Assess- ment based on students' perception reveals it as a useful distance learning tool. The laboratory is integrated in Automatl@bs, a Spanish interuniversity network of web-based laboratories devoted to distance learning of control engineering. 2013-02-05T10:20:37Z http://hdl.handle.net/2117/17574 Title: Diagnosis tools for PEMFC using humidification interruption tests Authors: Primucci, Mauricio Ariel; Serra, Maria; Riera Colomer, Jordi Abstract: This article presents different diagnosis tools for Proton Exchange Membrane Fuel Cells based on the analysis of their dynamic evolution when the humidification of the inlet gases is interrupted. The diagnosis is aimed to know the internal state of the fuel cell with respect to the water distribution. The proposed diagnosis procedures combine the information of the time response with that extracted from Electrochemical Impedance Spectroscopy and consist in monitoring the evolution of a set of performance indicators during the humidification interruption. The article presents a study for the selection of these performance indicators, which are related to the physical phenomena inside the PEMFC, and describes the patterns that correspond to proper or improper water distribution. 2013-02-05T10:01:02Z http://hdl.handle.net/2117/17559 Title: Study of hydrogen purge effects on performance and efficiency of a PEM fuel cell system Authors: Strahl, Stephan; Husar, Attila Peter; Riera Colomer, Jordi Abstract: Experimental analysis and CFD modeling is used in this work to analyze system efficiency related to hydrogen purge based water management in an open-cathode PEM fuel cell system. Excess water in a deadended anode decreases hydrogen concentration at the active catalyst surface and thus causes fuel cell performance losses. Purging the anode with hydrogen removes water and nitrogen that diffused through the membrane but also means wasting energy and thus decreasing overall system efficiency. Experiments with a 100W open-cathode stack have revealed that the need for a hydrogen purge strongly depends on the operation conditions and the state-of-health of the fuel cell and therefore the decision to perform a purge has to be evaluated online. A dynamic 2D CFD model of a single cell within the stack is used to investigate water distribution and transport within the cell before, during and after performing a purge at different operating conditions, linked to cell performance. Moreover, the model is capable of studying water transfer dynamics across the membrane and along the channel, including liquid water saturation. Altogether, the presented experimental and modeling work helps to improve the understanding of water transport in a PEM fuel cell and thus facilitates the development of strategies for increasing system efficiency and optimizing the water management by properly controlling the hydrogen purge. 2013-02-01T12:00:24Z http://hdl.handle.net/2117/17523 Title: Control repetitivo digital de sistemas con frecuencia incierta o variante en el tiempo Authors: Costa Castelló, Ramon; Ramos Fuentes, Germán Andrés; Olm Miras, Josep Maria Abstract: El control repetitivo digital es una t´ecnica basada en el principio del modelo interno que permite seguir y/o rechazar se˜nales peri´odicas. Una hip´otesis clave en los dise˜nos tradicionales de control repetitivo es que la frecuencia de tales se˜nales es constante y conocida, siendo su principal desventaja la elevada degradaci´on de prestaciones que aparece cuando dicha frecuencia es incierta o var´ıa con el tiempo. En este trabajo se presenta una revisi´on de las principales estrategias introducidas hasta la fecha para resolver este problema. 2013-01-25T12:52:40Z