EPIC - Energy Processing and Integrated Circuits
Total activity: 1029
Type
Research group
Type of group
UPC research group
Acronym
EPIC
URL
http://www.eel.upc.edu/investigacion/grupos-de-investigacion-1/electronica-industrial-y-de-pontencia/epic-energy-processing-and-integrated-circuits?set_language=es Open in new window
Objectives
Our research activity has been hitherto focused in energy processing integrated circuits, encompassing both CMOS technologies for future generation multicore processors and RF transmitters, as well as new devices for exploring the ultimate energy density limits. These activities have been driven by ultra-low-power battery operated devices now migrating into energy harvesting enabled wireless sensor networks, pushing down scalability limits through the concurrence of new devices (more than Moore, GaN, graphene), circuit and system perspectives with the aim of a transversal impact to various applications, namely, among others, both downscaled portable terminals and distributed sensors for wireless monitoring, and practically all applications within the integrated system and circuits area. New challenges include wireless networks-on-chip for next generation many-core processors for high performance computing, nano-satellite swarms, wireless energy transfer, smart grids
Keywords
Energy harvesting wireless sensor networks; Energy-aware graphene-enabled wireless communications at the nanoscale; Smart Grids; Wireless energy transfer for small satellite networks

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    A methodology to introduce sustainability into the Final Year Project to foster sustainable engineering projects  Open access

     Lopez Alvarez, David; Sanchez Carracedo, Fermin; Vidal Lopez, Eva Maria; Pegueroles Valles, Josep Rafel; Alier Forment, Marc; Cabre Garcia, Jose Maria; Garcia Almiñana, Jordi; García, Helena
    Annual Frontiers in Education Conference
    p. 2360-2366
    Presentation's date: 2014-10-24
    Presentation of work at congresses

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    The introduction of sustainability skills into higher education curricula is a natural effect of the increasing importance of sustainability in our daily lives. Topics like green computing, sustainable design or environmental engineering have become part of the knowledge required by today’s engineers. Furthermore, we strongly believe that the introduction of this skill will eventually enable future engineers to develop sustainable products, services and projects. The Final Year Project is the last academic stage facing students and a step towards their future professional engineering projects. As such, it constitutes a rehearsal for their professional future and an ideal opportunity for reflecting on whether their Final Year Project is sustainable or not, and to what extent. It also provides a good tool for reviewing the lessons learned about sustainability during the degree course and for applying them in a holistic and integrated way. In this paper, we present a guide that allows both students and advisors to think carefully about the sustainability of engineering projects, in particular the Final Year Project.

    The introduction of sustainability skills into higher education curricula is a natural effect of the increasing importance of sustainability in our daily lives. Topics like green computing, sustainable design or environmental engineering have become part of the knowledge required by today’s engineers. Furthermore, we strongly believe that the introduction of this skill will eventually enable future engineers to develop sustainable products, services and projects. The Final Year Project is the last academic stage facing students and a step towards their future professional engineering projects. As such, it constitutes a rehearsal for their professional future and an ideal opportunity for reflecting on whether their Final Year Project is sustainable or not, and to what extent. It also provides a good tool for reviewing the lessons learned about sustainability during the degree course and for applying them in a holistic and integrated way. In this paper, we present a guide that allows both students and advisors to think carefully about the sustainability of engineering projects, in particular the Final Year Project.

    Postprint (author’s final draft)

  • Capacitorless DC-DC converter

     Martínez García, Herminio; Grau Saldes, Antoni
    IEEE International Conference on Emerging Technologies and Factory Automation
    p. 1-6
    Presentation's date: 2014-09-19
    Presentation of work at congresses

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  • Versatility of power gyrator structures for energy processing in photovoltaic solar systems

     Martínez García, Herminio; Grau Saldes, Antoni
    IEEE International Conference on Emerging Technologies and Factory Automation
    p. 1-8
    Presentation's date: 2014-09-18
    Presentation of work at congresses

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  • Using constant switching frequency control in linear-assisted DC-DC switching converters

     Martínez García, Herminio; Grau Saldes, Antoni
    IEEE International Conference on Emerging Technologies and Factory Automation
    p. 1-6
    Presentation's date: 2014-09-18
    Presentation of work at congresses

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    The use of power DC-DC converters and gyrators structures for energy processing in photovotaic solar facilities  Open access

     Martínez García, Herminio
    International Symposium on Energy Challenges & Mechanics
    p. 1-5
    Presentation's date: 2014-08-21
    Presentation of work at congresses

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    This article provides a classification of high efficiency switching power-gyrator structures and their use as cells for energy processing in photovoltaic solar facilities. Having into account the properties of these topologies presented in the article, their inclusion in solar facilities allows increasing the performance of the whole installation. Thus, the design, simulation and implementation of a G-type power gyrator are carried out throughout the text. In addition, in order to obtain the maximum power from the photovoltaic solar panel, a maximum power point tracking (MPPT) is mandatory in the energy processing path. Therefore, the practical implementation carried out includes a control loop of the power gyrator in order to track the aforementioned maximum power point of the photovoltaic solar panel.

  • Power gyrator structures: Versatile cells for energy processing in photovoltaic solar facilities

     Martínez García, Herminio
    IEEE International Midwest Symposium on Circuits and Systems
    p. 447-450
    DOI: 10.1109/MWSCAS.2014.6908448
    Presentation's date: 2014-08-03
    Presentation of work at congresses

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    This paper provides a classification of high efficiency switching power-gyrator structures and their use as cells for energy processing in photovoltaic solar facilities. Having into account the properties of these topologies presented in the article, their inclusion in solar facilities allows increasing the performance of the whole installation. Thus, the design, simulation and implementation of a G-type power gyrator are carried out throughout the text. In addition, in order to obtain the maximum power from the photovoltaic solar panel, a maximum power point tracking (MPPT) is mandatory in the energy processing path. Therefore, the practical implementation carried out includes a control loop of the power gyrator in order to track the aforementioned maximum power point of the photovoltaic solar panel.

  • Design of a linear-assisted DC-DC switching regulator with constant switching frequency

     Martínez García, Herminio
    IEEE International Midwest Symposium on Circuits and Systems
    p. 455-458
    DOI: 10.1109/MWSCAS.2014.6908450
    Presentation's date: 2014-08-03
    Presentation of work at congresses

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    This article shows the proposal of a linear-assisted converter or linear-&-switching hybrid converter with a constant switching frequency. The control loop of the system is based on the current-mode technique. The main disadvantage of a converter with current-mode control is the inherent instability of the loop when switch duty ratios are greater than 0.5. In order to make stable the proposed linear-assisted converter, the article shows the technique based on a slope compensation.

  • Observation of chaotic behavior in automatic tuning loops for continuous-time filters

     Martínez García, Herminio; Cosp Vilella, Jordi; Manzanares Brotons, Manuel
    IEEE International Midwest Symposium on Circuits and Systems
    p. 742-745
    DOI: 10.1109/MWSCAS.2013.6674756
    Presentation's date: 2014-08
    Presentation of work at congresses

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    he appropriate linear dynamic modeling of continuous-time filters (CTFs) with automatic tuning loops should be obtained to assure stability in case an improved design of the loop controllers is to be carried out. With this aim, starting from a general and systematic analysis in order to obtain an equivalent small-signal linearized incremental model, from which transfer functions between output variables and control voltages are derived, the subsequent design of compensated loops with enhanced stability and dynamic performance is required. This systematic procedure allows obtaining improved controllers for the two involved control loops. However, CTFs with automatic tuning loops are nonlinear feedback systems with potential instability. What is more, nonlinear phenomena, which cannot be predicted by a design-oriented small signal modeling approach, are observed in this kind of tuning systems. The purpose of this work is to highlight that when control parameters are varied, the system could present different kinds of dynamical nonlinear phenomena such as bifurcations and chaotic behavior, which cannot be predicted by the small signal design-oriented model.

  • Cooperative signal amplification for molecular communication in nanonetworks

     Abadal Cavalle, Sergi; Llatser Marti, Ignacio; Alarcon Cot, Eduardo Jose; Cabellos Aparicio, Alberto
    Wireless networks
    Vol. 20, num. 6, p. 1611-1626
    DOI: 10.1007/s11276-014-0696-z
    Date of publication: 2014-08-01
    Journal article

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    Nanotechnology is enabling the development of devices in a scale ranging from a few to hundreds of nanometers. Communication between these devices greatly expands the possible applications, increasing the complexity and range of operation of the system. In particular, the resulting nanocommunication networks (or nanonetworks) show great potential for applications in the biomedical field, in which diffusion-based molecular communication is regarded as a promising alternative to EM-based solutions due to the bio-stability and energy-related requirements of this scenario. However, molecular signals suffer a significant amount of attenuation as they propagate through the medium, thus limiting the transmission range. In this paper, a signal amplification scheme for molecular communication nanonetworks is presented wherein a group of emitters jointly transmits a given signal after achieving synchronization. This is achieved by means of quorum sensing (QS), a method used by bacteria to both sense their population and coordinate their actions. By using the proposed methodology, the transmission range is extended proportionally to the number of synchronized emitters. An analytical model of QS is provided and validated through simulation. This model is the main contribution of this work and accounts for the activation threshold (which will eventually determine the resulting amplification level) and the delay of the synchronization process.

  • De la teoría a la práctica: cinco años después de la integración de la competencia genérica de sostenibilidad en el Grado en Ingeniería Informática  Open access

     Garcia Almiñana, Jordi; Sanchez Carracedo, Fermin; Lopez Alvarez, David; Vidal Lopez, Eva Maria; Cabre Garcia, Jose Maria; García García, Helena; Alier Forment, Marc
    Jornadas de Enseñanza Universitaria de la Informática
    p. 253-260
    Presentation's date: 2014-07-09
    Presentation of work at congresses

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    La sostenibilidad es una de las competencias trans- versales básicas que todo ingeniero debería adquirir durante su formación. De hecho, seguir desarrollando ciencia y tecnología de espaldas a la sostenibilidad provocaría en poco tiempo un colapso de nuestro planeta. La puesta en marcha del Espacio Europeo de Educación Superior (EEES) ha propiciado una opor- tunidad única para replantearse diferentes aspectos educativos, entre los cuales destaca la inclusión de esta competencia en los planes de estudio. Existe literatura abundante sobre estrategias y pro- puestas teóricas para incluir esta competencia en las ingenierías. Sin embargo, pocos trabajos han sido llevados a cabo desde una perspectiva más práctica. La Facultat de Informàtica de Barcelona (FIB) posee amplia experiencia en el diseño de titulaciones adap- tadas al EEES y ha integrado la sostenibilidad en su plan de estudios de Grado en Ingeniería Informática. En este trabajo se revisa el proceso de diseño del plan de estudios de Grado en Ingeniería Informática de la FIB, aprobado en el año 2009, y se analiza la experiencia de integración de la sostenibilidad tras cinco años de funcionamiento del grado. Se comentan los mecanismos de organización y coordinación entre las asignaturas implicadas y, finalmente, se extraen las lecciones aprendidas.

    La sostenibilidad es una de las competencias transversales básicas que todo ingeniero debería adquirir durante su formación. De hecho, seguir desarrollando ciencia y tecnología de espaldas a la sostenibilidad provocaría en poco tiempo un colapso de nuestro planeta. La puesta en marcha del Espacio Europeo de Educación Superior (EEES) ha propiciado una oportunidad única para replantearse diferentes aspectos educativos, entre los cuales destaca la inclusión de esta competencia en los planes de estudio. Existe literatura abundante sobre estrategias y propuestas teóricas para incluir esta competencia en las ingenierías. Sin embargo, pocos trabajos han sido llevados a cabo desde una perspectiva más práctica. La Facultat de Informàtica de Barcelona (FIB) posee amplia experiencia en el diseño de titulaciones adaptadas al EEES y ha integrado la sostenibilidad en su plan de estudios de Grado en Ingeniería Informática. En este trabajo se revisa el proceso de diseño del plan de estudios de Grado en Ingeniería Informática de la FIB, aprobado en el año 2009, y se analiza la experiencia de integración de la sostenibilidad tras cinco años de funcionamiento del grado. Se comentan los mecanismos de organización y coordinación entre las asignaturas implicadas y, finalmente, se extraen las lecciones aprendidas.

    SUMMARY -- Sustainability is one of the basic professional skills that every engineer should incorporate during their training. In fact, developing science and technology without sustainability criteria would collapse our planet. The launching of the European Higher Education Area (EHEA) has provided a unique opportunity to rethink different educational aspects, including the integration of this skill into the curriculum. Abundant literature exists on strategies and theoretical proposals to include this skill into engineering. However, few studies have been done from a more practical perspective. The Barcelona School of Informatics (FIB) has wide experience in the design of degrees according to the EHEA, and has integrated sustainability into the Informatics Engineering degree. This paper reviews the process of the design of the FIB’s Informatics Engineering degree curriculum, approved in 2009, and analyses the experience of sustainability integration after five years. The organizational and coordination mechanisms between the subjects are discussed, and finally the lessons learnt are extracted.

  • Optimization of WPT efficiency using a conjugate load in non-impedance matched systems.

     Chabalko, Matthew; Alarcon Cot, Eduardo Jose; Bou Balust, Elisenda; Ricketts, David S.
    IEEE International Symposium on Antennas and Propagation
    p. 645-646
    DOI: 10.1109/APS.2014.6904653
    Presentation's date: 2014-07-06
    Presentation of work at congresses

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    Maximum power transfer and maximum efficiency are two important design constraints in wireless power transfer applications. Several works have investigated the proper load and impedance match conditions to optimize either efficiency or power transfer. In this paper we show that the optimal load for maximum power transfer and maximum efficiency is the same (a conjugate matched load) when the source resistance is zero. This is important, as many WPT systems have a relatively low, unknown source impedance. Since the optimal load for both efficiency and power is the same as the source impedance approaches zero, the designer can use a bi-conjugate load for a near optimal design for both maximum power and efficiency. As the source impedance becomes significant, the bi-conjugate matched system provides higher power, but at the expense of lower efficiency. Maximum efficiency is achieved with a non-bi-conjugate load, when the source impedance is non-negligible.

  • Global MPPT scheme for photovoltaic string inverters based on restricted voltage window search algorithm

     Boztepe, Mutlu; Guinjoan Gispert, Francisco; Velasco Quesada, Guillermo; Silvestre Berges, Santiago; Chouder, Aissa; Karatepe, Engin
    IEEE transactions on industrial electronics
    Vol. 61, num. 7, p. 3302-3312
    DOI: 10.1109/TIE.2013.2281163
    Date of publication: 2014-07-01
    Journal article

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    String inverter photovoltaic (PV) systems with bypass diodes require improved global maximum power point tracking (GMPPT) algorithms to effectively reach the absolute maximum power operating point. Several GMPPT algorithms have been proposed to deal with this problem, but most of them require scanning wide voltage ranges of the PV array from nearly zero voltage to open-circuit voltage that increases the scanning time and, in turn, causes energy loss. This paper presents a novel GMPPT method which significantly restricts the voltage window search range and tracks the global power peak rapidly in all shading conditions. Simulation tests and experimental comparisons with another GMPPT algorithm are presented to highlight the features of the presented approach.

  • Diseño de una plataforma docente para el estudio de los sistemas de recolección de energía (energy harvesting) en los Grados de Ingeniería

     Martínez García, Herminio
    Annual Seminar on Automation, Industrial Electronics and Instrumentation
    p. 1-6
    Presentation's date: 2014-06-27
    Presentation of work at congresses

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    El presente artículo presenta el diseño e implementación física de una plataforma docente recolectora y acondicionadora de energía práctica para aplicaciones de energy harvesting. Concretamente, muestra la realización de un sistema de acondicionamiento de energía solar fotovoltaica a partir de un modelo concreto de panel solar. Con el fin de conseguir una plataforma lo más eficiente posible, se ha implementado un sistema de seguimiento del punto de máxima potencia (MPPT) del panel fotovoltaico que optimiza el rendimiento del mismo, adentrando, a su vez, al estudiante de Ingeniería en este tipo de algoritmos. Además, la plataforma recolectora posee regulación de salida, ofreciendo así una tensión de salida constante, independientemente tanto de variaciones de carga como de la tensión de entrada.

  • Simulación mediante “hardware in the loop” de un convertidor buck

     Velasco Quesada, Guillermo; Casellas Beneyto, Francisco; Guinjoan Gispert, Francisco; Esteban, Jordi; Martínez García, Herminio; Pique Lopez, Robert
    Seminario Anual de Automática, Electrónica Industrial e Instrumentación
    p. 6007.1-6007.5
    Presentation's date: 2014-06-26
    Presentation of work at congresses

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    Estudio eléctrico y térmico en transistores IGBT en paralelo con control de reparto de corriente  Open access

     Perez Delgado, Raul; Roman Lumbreras, Manuel; Velasco Quesada, Guillermo
    Annual Seminar on Automation, Industrial Electronics and Instrumentation
    p. 1007-1-1007-6
    Presentation's date: 2014-06-26
    Presentation of work at congresses

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    En este artículo se analiza el comportamiento eléctrico y térmico de transistores PT-IGBT conectados en paralelo utilizando un control activo de reparto equilibrado de corriente. El estudio de la estructura interna y de las ecuaciones que describen el funcionamiento de un transistor IGBT muestra la capacidad de modificar el funcionamiento del transistor según la relación tensión-corriente colector-emisor (VCE-ICE) variando el valor de la tensión puerta-emisor (VGE). Finalmente se comparan los resultados de funcionamiento de los transistores con control de reparto de corriente con los obtenidos sin aplicar ninguna acción de control.

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    Linear–assisted DC/DC regulator with modified current-mode one-cycle control  Open access

     Martínez García, Herminio
    Annual Seminar on Automation, Industrial Electronics and Instrumentation
    p. 1-4
    Presentation's date: 2014-06-26
    Presentation of work at congresses

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    Abstract—Linear-assisted DC/DC converters are structures that allow to take advantages of the two classic alternatives in the design of power supply systems: Voltage linear regulators (classic NPN topology or LDO –low dropout–) and switching DC/DC converters. This paper shows the proposal of a modified currentmode one-cycle control for linear-assisted DC/DC converters. The modified current-mode one-cycle control technique is proposed in order to obtain the duty cycle of the linear-assisted converter switch. The proposed structure can provide an output with suitable load and line regulations. The paper shows the design of the proposed modified current-mode one-cycle linear-assisted regulator and simulation results that validate the aforementioned proposal.

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    Gestión de energía en sistemas híbridos Red-PV-diesel en el proyecto MED-Solar  Open access

     Velasco Quesada, Guillermo; Casellas Beneyto, Francisco; Guinjoan Gispert, Francisco; Pique Lopez, Robert; Martínez García, Herminio; Pineau, A.; Graillot, A.
    Seminario Anual de Automática, Electrónica Industrial e Instrumentación
    p. 3010.1-3010.6
    Presentation's date: 2014-06-26
    Presentation of work at congresses

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    El presente trabajo aborda el diseño de la estructura de un sistema de gestión de energía eléctrica aplicable a sistemas eléctricos híbridos formados por la red eléctrica y sistemas de generación fotovoltaica, generación diésel y almacenamiento. La implementación de estos sistemas híbridos y sus sistemas de gestión será, dentro del marco del Proyecto MED-Solar, en tres países del área del Máshrek (Líbano, Palestina y Jordania), con el fin de demostrar que este tipo de instalaciones puede reducir parte de la problemática energética presente en estos países y, por tanto, mostrarse atractiva para diversos sectores económicos.

  • Banco de pruebas para verificar el rendimiento estático y dinámico del MPPT

     Velasco Quesada, Guillermo; Casellas Beneyto, Francisco; Guinjoan Gispert, Francisco; Pique Lopez, Robert
    Seminario Anual de Automática, Electrónica Industrial e Instrumentación
    p. 3016.1-3016.6
    DOI: -
    Presentation's date: 2014-06-26
    Presentation of work at congresses

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    Simulación mediante “hardware in the loop” de un convertidor Buck  Open access

     Casellas Beneyto, Francisco; Esteban, J.; Guinjoan Gispert, Francisco; Pique Lopez, Robert; Martínez García, Herminio; Velasco Quesada, Guillermo
    Annual Seminar on Automation, Industrial Electronics and Instrumentation
    p. 1-5
    Presentation's date: 2014-06-26
    Presentation of work at congresses

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    El presente artículo describe la implementación un convertidor reductor mediante su simulación por un ordenador estándar trabajando en tiempo real. El objetivo es determinar las limitaciones operativas y verificar la viabilidad como equipo HIL ("hardware in the loop") en una aplicación de electrónica de potencia de un ordenador estándar trabajando con un sistema operativo en tiempo real. Para verificar comportamiento del convertidor reductor simulado en tiempo real mediante el equipo HIL se utiliza como referencia el mismo convertidor reductor con modelado basado en SPICE. Finalmente se somete al modelo a diferentes ensayos para determinar el límite en los parámetros de la simulación que provoca el procesador trabajando en tiempo real.

    El presente artículo describe la implementación un convertidor reductor mediante su simulación por un ordenador estándar trabajando en tiempo real. El objetivo es determinar las limitaciones operativas y verificar la viabilidad como equipo HIL (

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    Design of an on-chip hybrid DC-DC converter  Open access

     Martínez García, Herminio
    Annual Seminar on Automation, Industrial Electronics and Instrumentation
    p. 1-4
    Presentation's date: 2014-06-26
    Presentation of work at congresses

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    This paper shows the design of a hybrid on-chip VLSI DC-DC converter for low to medium integrated circuit power consumption that combines a switching and a linear regulator in parallel. The main goal is to take the best of both approaches, obtaining good power efficiency as in switching converters with small voltage output ripple as in linear converters. While the switching regulator is used to drive most of the load current, the linear regulator supplies the required current to filter out the steady state ripple due to inductor switching without the need of a filtering output capacitor. In addition, the latter regulator supplies the required current when the load changes abruptly and the inductor current is momentarily insufficient. The design has been tested with simulations using a standard 180 nm CMOS technology showing good performance.

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    Gestión de energía en sistemas híbridos red–FV–Diésel en el proyecto MED-Solar  Open access

     Velasco Quesada, Guillermo; Casellas Beneyto, Francisco; Guinjoan Gispert, Francisco; Pique Lopez, Robert; Martínez García, Herminio; Pineau, A.; Graillot, A.
    Annual Seminar on Automation, Industrial Electronics and Instrumentation
    p. 1-6
    Presentation's date: 2014-06-25
    Presentation of work at congresses

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    El presente trabajo aborda el diseño de la estructura de un sistema de gestión de energía eléctrica aplicable a sistemas eléctricos híbridos formados por la red eléctrica y sistemas de generación fotovoltaica, generación diésel y almacenamiento. La implementación de estos sistemas híbridos y sus sistemas de gestión será, dentro del marco del Proyecto MED-Solar, en tres países del área del Máshrek (Líbano, Palestina y Jordania), con el fin de demostrar que este tipo de instalaciones puede reducir parte de la problemática energética presente en estos países y, por tanto, mostrarse atractiva para diversos sectores económicos.

  • Design and implementations of a microcontroller-based intelligent field transmitter

     Martínez García, Herminio; Grau Saldes, Antoni
    Workshop on Complexity in Engineering
    p. 22-25
    Presentation's date: 2014-06-16
    Presentation of work at congresses

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    In this article the design of a prototype of an Intelligent Transmitter of Field (ITF) is presented. The objective of the work is approaching the engineering students, in the area of Automatic Control, to the functional and technological challenges intrinsic to this type of implementations. Aspects like power consumption of the electronic circuits, energy supply through the wires of communication of the transmitter, the coexistence in these wires of analogical signals of measurement and digital signals of communication, etc., are essential to get the foreseen objective. The article seeks, also, to contribute to a didactic solution for a problem that has been one of the main challenges in instrumentation field.

  • The Use of constant switching frequency control for a linear-assisted DC-DC switching converter

     Grau Saldes, Antoni; Martínez García, Herminio
    Workshop on Complexity in Engineering
    p. 26-29
    Presentation's date: 2014-06-16
    Presentation of work at congresses

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    This article shows the proposal of a linear–assisted converter or linear–&–switching hybrid converter with a constant switching frequency. The control loop of the system is based on the current–mode technique. The main disadvantage of a converter with current–mode control is the inherent instability of the loop when switch duty ratios are greater than 0.5. In order to make stable the proposed linear–assisted converter, the article shows the technique based on a slope compensation.

  • A modified current-mode one-cycle control used for linear–assisted DC/DC regulator

     Martínez García, Herminio; Grau Saldes, Antoni
    Workshop on Complexity in Engineering
    p. 30-33
    Presentation's date: 2014-06-16
    Presentation of work at congresses

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    Linear-assisted DC/DC converters are structures that allow to take advantages of the two classic alternatives in the design of power supply systems: Voltage linear regulators (classic NPN topology or LDO –low dropout–) and switching DC/DC converters. This paper shows the proposal of a modified current-mode one-cycle control for linear-assisted DC/DC converters. The modified current-mode one-cycle control technique is proposed in order to obtain the duty cycle of the linear-assisted converter switch. The proposed structure can provide an output with suitable load and line regulations. The paper shows the design of the proposed modified current-mode one-cycle linear-assisted regulator and simulation results that validate the aforementioned proposal.

  • Linear–assisted DC/DC converters with variable frequency: On their control strategies

     Martínez García, Herminio; Grau Saldes, Antoni
    Workshop on Complexity in Engineering
    p. 56-61
    Presentation's date: 2014-06-16
    Presentation of work at congresses

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    Linear-assisted DC/DC converters (or linearswitching hybrid DC/DC converters) consist of a voltage linear regulator (classic NPN or nMOS topologies and LDO) connected in parallel with a switching DC/DC converter. In order to control these hybrid structures, different strategies exist, allowing to fix the switching frequency as a function of some parameters of the linear regulator. This article compares two control strategies that, although can be applied to the same circuital structure of linear-assisted converter, are sensibly different. The first one, reported in previous literature, cancels completely the average current through the linear regulator in steady state to achieve a reduction of the losses. Thus the efficiency of the whole system increases and almost equals the one of the standalone switching converter. The proposed approach, in spite of a slightly increment of linear regulator’s losses, reduces the output ripple due to the crossover distortion of linear regulator output stage.

  • Chaotic behaviour in on-chip automatic tuning loops for continuous–time filters

     Martínez García, Herminio
    Workshop on Complexity in Engineering
    p. 52-55
    Presentation's date: 2014-06-16
    Presentation of work at congresses

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    Continuous-time filters (CTF) with automatic tuning loops are nonlinear feedback systems with potential instability. While an appropriate small signal linear dynamic modeling of the tunable filter should be obtained for design purpose, its ability to predict the real nonlinear dynamic behavior of the system is limited. In order to overcome this problem, a general and systematic procedure is used to obtain a large signal nonlinear model. The obtained model can accurately predict nonlinear phenomena such as bifurcations and chaotic behavior. From this model, some numerical simulations results are presented in this paper. As far as the authors know, the observation of these phenomena in CTF with tuning loops has not been previously presented. Thus, the results obtained in this work can provide some help to obtain improved controllers (with higher bandwidth and better performance) for the two involved control loops.

  • Parametric filters laboratory with a noise generator and data acquisition

     Martínez García, Herminio
    Workshop on Complexity in Engineering
    p. 97-100
    Presentation's date: 2014-06-16
    Presentation of work at congresses

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    Audio filtering systems are used in commercial applications involving equalizers. However, some of the topologies used can be modified to be used in audio signal treatment applications. Parametric filter topologies allow the user to modify independently the central frequency of the filter, the bandwidth and the gain. Using a microprocessor and programmable components will allow the user to modify the parameters of the filter and to acquire the filtered signal so it can be processed in other stages. To improve the functionality of the system, a server will be implemented to process the data sent by the user, will be sent afterwards to the microcontroller. Finally, the results obtained will be thrown back to the user.

  • Modified current-mode one-cycle control for linear–assisted DC/DC regulator

     Martínez García, Herminio; Cosp Vilella, Jordi
    IEEE International Symposium on Circuits and Systems
    p. 2688-2691
    DOI: 10.1109/ISCAS.2014.6865727
    Presentation's date: 2014-06-04
    Presentation of work at congresses

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    Linear-assisted DC/DC converters are structures that allow to take advantages of the two classic alternatives in the design of power supply systems: Voltage linear regulators (classic NPN topology or LDO –low dropout–) and switching DC/DC converters. This paper shows the proposal of a modified current-mode one-cycle control for linear-assisted DC/DC converters. The modified current-mode one-cycle control technique is proposed in order to obtain the duty cycle of the linear-assisted converter switch. The proposed structure can provide an output with suitable load and line regulations. The paper shows the design of the proposed modified current-mode one-cycle linear-assisted regulator and simulation results that validate the aforementioned proposal.

  • Advances in non-radiative resonant inductive coupling wireless power transfer: a comparison of alternative circuit and system models driven by emergent applications

     Bou Balust, Elisenda; Sedwick, Raymond; Hu, Patrick; Alarcon Cot, Eduardo Jose
    IEEE International Symposium on Circuits and Systems
    p. 2037-2040
    DOI: 10.1109/ISCAS.2014.6865565
    Presentation's date: 2014-06-01
    Presentation of work at congresses

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    Recent research in wireless power transfer (WPT) using resonant inductive coupling has demonstrated very high efficiencies at large distances compared to the transmitting element dimensions, thereby increasing the number of potential applications of WPT. Since resonant inductive coupling is a very multidisciplinary field of research, different approaches have been proposed to predict the behaviour of these systems from the physical theory of resonators (coupled-mode theory) and circuit theory. Although the equivalence of these models for a point-to-point link has already been studied together with the performance metrics Power Transferred to the Load (PTL) and Power Transfer Efficiency (PTE), the new challenges and applications of this technology emphasize the necessity of analytical models to predict and assess the behavior of Multiple Input - Multiple Output (MIMO) links. In this article we revisit the current analytical models from the MIMO perspective, derive the analytical equations for the equivalent performance metrics PTE and PTL and demonstrate how to maximize them in a non-radiative resonant wireless power transfer link from a circuit-centric point of view, providing design guidelines in terms of optimal source and load impedances. This work concludes with a prospective discussion on open challenges of WPT. © 2014 IEEE.

  • Unveiling nonlinear dynamics in resonant inductively coupled wireless power transfer

     Bou Balust, Elisenda; El Aroudi, Abdelali; Fisher, Peter; Alarcon Cot, Eduardo Jose
    IEEE International Symposium on Circuits and Systems
    p. 2612-2615
    DOI: 10.1109/ISCAS.2014.6865708
    Presentation's date: 2014-06-01
    Presentation of work at congresses

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    Coupled magnetic resonance is considered to be a key enabling technology for mid-range wireless power transfer. Models and systems have hitherto considered linear resonators as underlying dynamics, thereby limiting practical deployability due to the extreme sensitivity in front of parameter mismatch and resonance detuning. In this work, structural nonlinear modeling of constituent elements of the resonant link-resonant coils- is considered to unveil the existence of nonlinear dynamic regimes. The methodology considered to explore the nonlinear behavior is based on a behavioral model consisting of state equations, Floquet theory and Filippov method to study the stability of the periodic regime through the associated monodromy matrix. The ultimate aim of the investigation is a design-oriented parameter space exploration which characterizes the border of occurrence of the different dynamic modes in wireless power transfer links. © 2014 IEEE.

  • Circuit area optimization in energy temporal sparse scenarios for multiple harvester powered systems

     Gomez Cid-fuentes, Raul; Cabellos Aparicio, Alberto; Alarcon Cot, Eduardo Jose
    IEEE International Symposium on Circuits and Systems
    p. 2486-2489
    DOI: 10.1109/ISCAS.2014.6865677
    Presentation's date: 2014-06-01
    Presentation of work at congresses

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    Multi-source energy harvesters are gaining interest as a robust alternative to power wireless sensors, since the sensor node can maintain its operation regardless of the fact that one of its energy sources might be temporarily unavailable. Interestingly, and less explored, when the energy availability of the energy sources present large temporal variations, combining multiple energy sources reduce the overall sparsity. As a result, the performance of a multiple energy harvester powered sensor node is significantly better compared to a single energy source which harvests the same amount of energy. In this context, a circuit area optimization framework for multiple source energy harvesting powered systems is proposed. This framework takes advantage of this improvement in performance to provide the optimal amount of energy harvesters, the requirements of each energy harvester and the required energy buffer capacity, such that the overall area or volume is minimized. As the results show, by conducting a joint design of the energy harvesters and the energy buffer, the overall area or volume of a sensor node can be significantly reduced. © 2014 IEEE.

  • Fuzzy logic controller design for battery energy management in a grid connected electro-thermal microgrid

     Arcos Aviles, Diego Gustavo; Vega Muñoz, Christian; Guinjoan Gispert, Francisco; Marroyo Palomo, Luis; Sanchis Gúrpide, Pablo
    IEEE International Symposium on Industrial Electronics
    p. 2014-2019
    DOI: 10.1109/ISIE.2014.6864926
    Presentation's date: 2014-06-01
    Presentation of work at congresses

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    A fuzzy logic controller strategy for battery energy management in a grid connected electro-thermal residential microgrid is presented. The fuzzy control policy manages the power of the microgrid storage elements in order to minimize a set of quality indices involving, among others, the power profile exchanged with the mains. Numerical simulations using real measured data generation and consumption are provided to both validate the control design and to highlight the benefits of including thermal elements in the overall energy management strategy of the system. © 2014 IEEE.

  • Temperature gradient sensor from pulsed power supply duty cycle in ultra-low-power energy harvesting system

     Jove Casulleras, Roger; Ramos Castro, Juan Jose; Corimanya, H; Camps Carmona, Adriano Jose; Alarcon Cot, Eduardo Jose; Amezaga Sarries, Adria; Bou Balust, Elisenda
    Electronics Letters
    Vol. 50, num. 11, p. 826-828
    DOI: 10.1049/el.2014.0399
    Date of publication: 2014-05-22
    Journal article

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    Directly interfacing sensors that link sensors to micro-controllers without a signal conditioning circuit or an analogue-to-digital converter on the one side and energy harvesting systems on the other side are two key enabling technologies to create self-powered autonomous low-cost and low-maintenance sensor networks. In this reported work, both technologies are concurrently combined in such a way that the duty cycle of the pulsed power supply provided by the harvesting system itself yields in turn a temperature gradient sensor functionality. Originally conceived to power a low-power satellite beacon in a CubeSat project, it has found application, among other applications, in automatic air conditioning and heating systems aiming smart buildings.

  • Design and comparison of flipped active inductors with high quality factors

     Saberkari, Alireza; Ziabakhsh, Soheil; Martínez García, Herminio; Alarcon Cot, Eduardo Jose
    Electronics Letters
    Vol. 50, num. 13, p. 925-927
    DOI: 10.1049/el.2014.0488
    Date of publication: 2014-05-19
    Journal article

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    A new design based on the flipped-structure for RF active inductors is presented. The conventional flipped-active inductor (FAI) composed of only two transistors is considered as a starting structure. However, it suffers from low-voltage swing, which increases the nonlinearity. Additionally, it requires high power consumption to achieve adequate inductance and quality factor values. A circuit topology named cascoded FAI (CASFAI) based on the basic FAI is proposed. A common-gate transistor added in the feedback path of the proposed CASFAI results in an increase of the voltage swing and linearity as well as the feedback gain. The performance metrics of such active inductors are benchmarked by analytical models and validated in the ADS using a 0.18 µm CMOS process. The results indicate that the CASFAI can achieve a notably higher quality factor and higher inductance values while consuming less power in comparison to the basic FAI.

  • Nonlinear dynamics and bifurcation behavior of a 2-DOF spring resonator with end stopper for energy harvesting

     El Aroudi, Abdelali; Blokhina, Elena; O'Connell, D.; Fu, B; Frizzell, R; Feely, Orla; Alarcon Cot, Eduardo Jose
    International Conference on Structural Dynamics and Diagnosis
    p. 08006-1-08006-6
    DOI: 10.1051/matecconf/20141608006
    Presentation's date: 2014-05
    Presentation of work at congresses

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    In this paper, the model of a two-degree-of-freedom (2-DOF) spring resonator with end stopper for an energy harvesting application is presented. Then we characterize its nonlinear dynamical behavior by numerical simulations when some suitable parameters are varied. The system is formed by two resonators subject to external vibrational excitation and with an end stopper. We present the continuous time dynamical model of the system in the form of a switched fourth order differential equation. Harmonic vibrations are considered as the main ambient energy source for the system and its frequency response representing the RMS value of the displacement is first computed. The dynamical behavior is unveiled by computing state-space trajectories, timedomain series and FFT spectra and frequency response as the excitation amplitude is varied.

  • Nonlinear dynamics of an ambient noise driven array of coupled graphene nanostructured devices for energy harvesting

     El Aroudi, Abdelali; Lopez Suarez, Miquel; Alarcon Cot, Eduardo Jose; Rurali, Riccardo; Abadal, Gabriel
    International Conference on Structural Dynamics and Diagnosis
    p. 01001-1-01001-4
    DOI: 10.1051/matecconf/20141601001
    Presentation's date: 2014-05
    Presentation of work at congresses

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    Nonlinearities have been shown to play an important role in increasing the extracted energy of energy harvesting devices at the macro and micro scales. Vibration-based energy harvesting on the nano scale has also received attention. In this paper, we characterize the nonlinear dynamical behavior of an array of three coupled strained nanostructured graphene for its potential use in energy harvesting applications. The array is formed by three compressed vibrating membrane graphene sheet subject to external vibrational noise excitation. We present the continuous time dynamical model of the system in the form of a double-well three degree of freedom system. Random vibrations are considered as the main ambient energy source for the system and its performances in terms of the probability density function, RMS or amplitude value of the position, FFT spectra and state plane trajectories are presented in the steady state non-equilibrium regime when the noise level is considered as a control parameter.

  • Linear–assisted DC/DC converters with modified current-mode control applied to photovoltaic solar systems

     Martínez García, Herminio
    International Conference on Renewable Energies and Power Quality
    p. 1-5
    Presentation's date: 2014-04-08
    Presentation of work at congresses

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    This article shows the proposal of a current-mode one-cycle control for linear-assisted DC/DC converters. Linearassisted DC/DC converters are structures that allow to take advantages of the two classic alternatives in the design of power supply systems: voltage linear regulators (classic NPN topology or LDO –low dropout–) and switching DC/DC converters. The current-mode one-cycle control technique is proposed in order to obtain the duty cycle of the linear-assisted converter switch. The proposed structure can provide an output with suitable load and line regulations. Thus, the paper shows the design and simulation results of the proposed current-mode one-cycle linear-assisted converter.

  • The use of power gyrator structures as energy processing cells in photovoltaic solar facilities

     Martínez García, Herminio
    International Conference on Renewable Energies and Power Quality
    p. 1-5
    Presentation's date: 2014-04-08
    Presentation of work at congresses

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    This paper will provide a classification of high efficiency switching power-gyrator structures and their use as cells for energy processing in photovoltaic solar facilities. Having into account the properties of these topologies presented in the article, their inclusion in solar facilities allows increasing the performance of the whole installation. Thus, the design, simulation and implementation of a G-type power gyrator are carried out throughout the text. In addition, in order to obtain the maximum power from the photovoltaic solar panel, a maximum power point tracking (MPPT) is mandatory in the energy processing path. Therefore, the practical implementation carried out includes a control loop of the power gyrator in order to track the aforementioned maximum power point of the photovoltaic solar panel.

  • Design-oriented analysis of quantization-induced limit cycles in a multiple-sampled digitally controlled buck converter

     Bradley, Mark; Alarcon Cot, Eduardo Jose; Feely, Orla
    IEEE transactions on circuits and systems I: regular papers
    Vol. 61, num. 4, p. 1192-1205
    DOI: 10.1109/TCSI.2013.2283671
    Date of publication: 2014-04-01
    Journal article

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    Digital control of switching power converters is an area which has seen increased attention in recent years. However, quantization in the feedback loop from the analog-to-digital (A/D) converter and the digital pulse width modulator (DPWM) may cause limit cycle oscillations to manifest, which are generally seen as being undesirable. This paper presents an analysis of the limit cycle behavior found in a multiple-sampled digitally controlled buck converter. The limit cycles which may arise in the system are characterized and conditions to prevent these oscillations from occurring are presented. © 2004-2012 IEEE.

  • Maximum power point tracking based on slidingmode control for output-series connected converters in photovoltaic systems

     Cabal, Cédric; Martínez Salamero, Luis; Séguier, Lionel; Alonso, Corinne; Guinjoan Gispert, Francisco
    IET power electronics
    Vol. 7, num. 4, p. 914-923
    DOI: 10.1049/iet-pel.2013.0348
    Date of publication: 2014-04-01
    Journal article

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    A perturb and observe algorithm based on both the power-current characteristic of a photovoltaic (PV) panel and the sliding-mode control of the input inductor current of an associated converter is investigated in a static application. A single ended primary inductance converter (SEPIC) converter charging a battery from a PV generator illustrates the procedure whose effectiveness is proved with experimental results. The reported technique is appropriate for distributed maximum power point tracking of PV systems with output series connected DC-DC switching converters. In these systems, each converter is supplied by an independent PV panel at the input port whereas its output port is connected in series with the output ports of the other converters. The proposed converter interconnection is based on a transformer-less SEPIC because of the capability of this converter to step-up or step-down the input voltage. The resulting system allows maximum power extraction from each PV source even in cases of non-uniform irradiance. © The Institution of Engineering and Technology 2014.

  • Some limits in peer assessment

     Domingo Peña, Joan; Martínez García, Herminio; Gomariz Castro, Spartacus; Gamiz Caro, Juan
    Journal of technology and science education
    Vol. 4, num. 1, p. 12-24
    Date of publication: 2014-03-25
    Journal article

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    Nowadays, the educational methodology known as ‘peer assessment’ constitutes one of the pillars of formative assessment at the different levels of the educational system, particularly at the University level. In fact, in recent years, it has been increasingly used to enhance students' meaningful learning, as it is considered to be an element of social learning, in which students benefit from the lessons learned by other classmates, and draw upon the ability to assess the quality of the learning, contrasting it with the level of knowledge that each has about the subject/course being evaluated, and using common evaluation criteria. In this regard, this paper represents the experience of two groups of students. It allows us to determine how many peer assessments should be required of students in a particular course in order to constitute a serious, reliable activity. On the other hand, from the point of view of the student, the assessments are evaluated to the extent that they are seen as a required and mandatory exercise that must be carried out by students simply to pass the course. In the latter case, the activity can become extremely trivial and banal. Statistical analysis of the results indicates that three peer assessments per student appraised represents an adequate number. On the other hand, more than thirty peer assessments fail to contribute to learning, nor do they represent serious activities.

  • N3Sim: Simulation framework for diffusion-based molecular communication nanonetworks

     Llatser Marti, Ignacio; Demiray, D.; Cabellos Aparicio, Alberto; Altilar, D. Turgay; Alarcon Cot, Eduardo Jose
    Simulation modelling practice and theory
    Vol. 42, p. 210-222
    DOI: 10.1016/j.simpat.2013.11.004
    Date of publication: 2014-03-01
    Journal article

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    Diffusion-based molecular communication is a promising bio-inspired paradigm to implement nanonetworks, i.e., the interconnection of nanomachines. The peculiarities of the physical channel in diffusion-based molecular communication require the development of novel models, architectures and protocols for this new scenario, which need to be validated by simulation. N3Sim is a simulation framework for nanonetworks with transmitter, receiver, and harvester nodes using Diffusion-based Molecular Communication (DMC). In DMC, transmitters encode the information by releasing molecules into the medium, thus varying their local concentration. N3Sim models the movement of these molecules according to Brownian dynamics, and it also takes into account their inertia and the interactions among them. Harvesters collect molecules from the environment to reuse them for later transmissions. Receivers decode the information by sensing the particle concentration in their neighborhood. The benefits of N3Sim are multiple: the validation of channel models for DMC and the evaluation of novel modulation schemes are just a few examples. (C) 2013 Elsevier B.V. All rights reserved.

  • Low cost photovoltaic array emulator design for the test of PV grid-connected inverters

     Chavarria Roe, Javier; Biel Sole, Domingo; Guinjoan Gispert, Francisco; Poveda Lopez, Alberto; Masana Nadal, Francisco; Alarcon Cot, Eduardo Jose
    International Multi-Conference on Systems, Signals and Devices
    p. 1-6
    DOI: 10.1109/SSD.2014.6808860
    Presentation's date: 2014-02-11
    Presentation of work at congresses

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    This paper presents a low cost photovoltaic array emulator design based on a DC-DC Boost converter. This design arises from the need to study in the laboratory new PV inverters based on SiC devices in order to improve their performances. The lack of space for installation of real photovoltaic panels and the high costs of the commercial emulators require of alternative systems which allow the reproduction of the characteristic curves of the panels as well as their dependence on changing environmental conditions. The emulator design is applied to a full-bridge single phase grid-connected inverter. Simulation results are provided to confirm the proper operation of the PV emulator. © 2014 IEEE.

  • Class E2 resonant non-radiative wireless power transfer link: a design-oriented joint circuit-system co-characterization approach

     Bou Balust, Elisenda; Nagashima, Tomoharu; Sekiya, Hiroo; Alarcon Cot, Eduardo Jose
    International Multi-Conference on Systems, Signals and Devices
    p. 1-4
    DOI: 10.1109/SSD.2014.6808902
    Presentation's date: 2014-02-11
    Presentation of work at congresses

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    Resonant Inductive CouplingWireless Power Transfer is a key technology to provide an efficient and harmless wireless energy channel to consumer electronics, biomedical implants and wireless sensor networks. Many applications have been proposed for this technology, but the interplay between the Resonant Inductive Coupling magnetic link and the power electronics front-end is still unclear. In this paper, we propose a design-oriented joint circuit-system approach to design a high-efficiency resonant inductive coupling wireless power transfer link embedded in a class E2 DC-DC converter. © 2014 IEEE.

  • Performance analysis of dual-frequency buck converter for integrated power management

     Shirmohammadli, V.; Saberkari, Alireza; Alarcon Cot, Eduardo Jose
    Power Electronics, Drive Systems and Technologies Conference
    p. 402-407
    DOI: 10.1109/PEDSTC.2014.6799409
    Presentation's date: 2014-02
    Presentation of work at congresses

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    The use of dual-frequency (DF) buck converter architecture consisting of a merged structure of high and low frequency buck cells is presented as a candidate topology for integrated power management to obtain favorable tradeoffs in terms of efficiency, switching ripple, and bandwidth. It is shown that having two degrees of freedom in designing the DF buck helps to achieve high efficiency and low output ripples, simultaneously. A comparison analysis is done with regards to the aforementioned performance indexes with the standard and three-level buck converters and the results are validated in HSPICE in a 0.35 µm CMOS process.

  • On the Scalability Limits of Communication Networks to the Nanoscale  Open access

     Llatser Marti, Ignacio
    Universitat Politècnica de Catalunya
    Theses

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    Los nanosistemas, sistemas integrados con un tamaño total de unos pocos micrómetros, son capaces de interactuar en la nanoescala, pero su corto radio de acción limita su utilidad en escenarios prácticos. Las nanoredes, que surgen de la interconexión de nanosistemas, amplían su ámbito de operación permitiendo la comunicación entre nanosistemas, aumentando de esta forma sus aplicaciones potenciales. Con el fin de dotar de capacidades de comunicación a los nanosistemas, su subsistema de comunicación debe reducirse a unos pocos micrómetros. Existen dudas sobre la viabilidad de miniaturizar las antenas metálicas actuales a un tamaño tan pequeño, especialmente porque su frecuencia de resonancia sería extremadamente alta (en el espectro óptico), lo que causaría a una gran atenuación de las ondas radiadas. Como alternativa, se han propuesto dos nuevos paradigmas para implementar comunicaciones inalámbricas entre nanosistemas: las comunicaciones moleculares y las comunicaciones inalámbricas basadas en grafeno. Por un lado, las comunicaciones moleculares consisten en el intercambio de moléculas entre nanosistemas, inspirado en la comunicación entre células vivas. En las comunicaciones moleculares basadas en difusión (DMC), las moléculas emitidas se propagan por el medio mediante un proceso de difusión hasta que alcanzan el receptor. Por otro lado, el grafeno (una lámina de átomos de carbono de un átomo de espesor) permite implementar antenas de grafeno plasmónicas, o grafenas. Debido a efectos plasmónicos, grafenas con un tamaño de unos pocos micrómetros radian ondas en la banda de terahercios, dando lugar al paradigma de las comunicaciones inalámbricas basadas en grafeno (GWC). Para averiguar cómo escalan las redes de comunicación a medida que se reducen sus dimensiones, esta tesis se presenta un análisis de la escalabilidad de las redes de comunicaciones hacia la nanoescala, siguiendo un modelo general con la menor cantidad posible de hipótesis. Hemos propuesto dos esquemas de detección en DMC: detección de amplitud y detección de energía. Hemos identificado importantes métricas de rendimiento y calculado su escalabilidad con respecto a la distancia de transmisión, que difiere significativamente respecto a las comunicaciones inalámbricas tradicionales. Estas nuevas tendencias de escala requieren el diseño de nuevos protocolos de red especialmente adaptados a las redes de DMC. El análisis de la propagación de ondas plasmónicas en grafenas permite determinar sus propiedades de radiación. En particular, la frecuencia de resonancia de las grafenas no sólo es más baja que en antenas metálicas, sino que también aumenta más lentamente a medida que reducimos su longitud. Por otra parte, la frecuencia de resonancia de las grafenas puede ser ampliamente controlada en función de parámetros como las dimensiones de la grafena, el tiempo de relajación del grafeno y el potencial químico. Además, proponemos un montaje experimental que permite la medición de grafenas alimentadas con una fuente fotoconductora. También hemos analizado los efectos de la absorción molecular en el canal de terahercios a corto alcance, el escenario de operación de las grafenas. La absorción molecular es un proceso por el cual moléculas presentes en la atmósfera absorben parte de la energía de las ondas radiadas por las grafenas, degradando su rendimiento. Hemos cuantificado esta degradación derivando parámetros de rendimiento en este escenario, que muestran novedosas tendencias de escalabilidad en función de la distancia de transmisión. Por último, hemos encontrado que la capacidad de canal de GWC escala mejor a medida que el tamaño de la antena se reduce con respecto a las comunicaciones inalámbricas tradicionales. En consecuencia, las GWC requerirán una potencia de transmisión más baja para lograr un cierto rendimiento. Estos resultados establecen un marco general que puede servir de guía para diseñar las futuras redes de comunicaciones inalámbricas entre nanosistemas.

    Nanosystems, integrated systems with a total size of a few micrometers, are capable of interacting at the nanoscale, but their short operating range limits their usefulness in practical macro-scale scenarios. Nanonetworks, the interconnection of nanosystems, will extend their range of operation by allowing communication among nanosystems, thereby greatly enhancing their potential applications. In order to integrate communication capabilities into nanosystems, their communication subsystem needs to shrink to a size of a few micrometers. There are doubts about the feasibility of scaling down current metallic antennas to such a small size, mainly because their resonant frequency would be extremely high (in the optical domain) leading to a large free-space attenuation of the radiated EM waves. In consequence, as an alternative to implement wireless communications among nanosystems, two novel paradigms have emerged: molecular communication and graphene-enabled wireless communications. On the one hand, molecular communication is based on the exchange of molecules among nanosystems, inspired by communication among living cells. In Diffusion-based Molecular Communication (DMC), the emitted molecules propagate throughout the environment following a diffusion process until they reach the receiver. On the other hand, graphene, a one-atom-thick sheet of carbon atoms, has been proposed to implement graphene plasmonic RF antennas, or graphennas. Graphennas with a size in the order of a few micrometers show plasmonic effects which allow them to radiate EM waves in the terahertz band. Graphennas are the enabling technology of Graphene-enabled Wireless Communications (GWC). In order to answer the question of how communication networks will scale when their size shrinks, this thesis presents a scalability analysis of the performance metrics of communication networks to the nanoscale, following a general model with as few assumptions as possible. In the case of DMC, two detection schemes are proposed: amplitude detection and energy detection. Key performance metrics are identified and their scalability with respect to the transmission distance is found to differ significantly from the case of traditional wireless communications. These unique scaling trends present novel challenges which require the design of novel networking protocols specially adapted to DMC networks. The analysis of the propagation of plasmonic waves in graphennas allows determining their radiation performance. In particular, the resonant frequency of graphennas is not only lower than in metallic antennas, but it also increases more slowly as their length is reduced to the nanoscale. Moreover, the study of parameters such as the graphenna dimensions, the relaxation time of graphene and the applied chemical potential shows the tunability of graphennas in a wide frequency range. Furthermore, an experimental setup to measure graphennas based on feeding them by means of a photoconductive source is described. The effects of molecular absorption in the short-range terahertz channel, which corresponds to the expected operating scenario of graphennas, are analyzed. Molecular absorption is a process in which molecules present in the atmosphere absorb part of the energy of the terahertz EM waves radiated by graphennas, causing impairments in the performance of GWC. The study of molecular absorption allows quantifying this loss by deriving relevant performance metrics in this scenario, which show novel scalability trends as a function of the transmission distance with respect to the case of free-space propagation. Finally, the channel capacity of GWC is found to scale better as the antenna size is reduced than in traditional wireless communications. In consequence, GWC will require lower transmission power to achieve a given performance target. These results establish a general framework which may serve designers as a guide to implement wireless communication networks among nanosystems.

  • Técnicas de control para la mejora de la estabilidad en redes eléctricas con convertidores electrónicos operando a potencia constante

     Fossas Colet, Enric; Guinjoan Gispert, Francisco; Doria Cerezo, Arnau; Olm Miras, Josep Maria; Griño Cubero, Roberto
    Competitive project

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  • Transferencia de energía inalámbrica: acoplamiento inductivo resonante

     Poveda Lopez, Alberto; Vidal Lopez, Eva Maria; Martínez García, Herminio; Alarcon Cot, Eduardo Jose
    Competitive project

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  • Premi al Millor Projecte de Final de Carrera CETIB 2013

     Martínez García, Herminio
    Award or recognition

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  • Access to the full text
    Design of an on-chip linear-assisted DC-DC voltage regulator  Open access

     Cosp Vilella, Jordi; Martínez García, Herminio
    IEEE International Conference on Electronics, Circuits and Systems
    p. 353-356
    Presentation's date: 2013-12-10
    Presentation of work at congresses

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    This article shows the design of an on-chip CMOS linear-assisted DC-DC regulator. It results a good alternative topology to classic switching DC-DC power converters. In the presented technique, an auxiliary linear regulator is used to cancel the output voltage ripple and provides fast responses for load and line variations. On the other hand, a switching converter, connected in parallel, allows supplying almost the whole output current demanded by the load. The objective of this linear-assisted regulator or hybrid topology is to achieve a high efficiency of switching converters, with suitable load and line regulation features, typical of linear regulators. In this kind of on-chip applications, CMOS is the current prevailing technology. Thus, in order to implement on-chip power supply systems and on-chip power management systems with low-to-medium current consumption, this structure has good features.

    Postprint (author’s final draft)