Design and analysis of ripple-based controls based on the discrete modeling and Floquet theory

Ripple-based controls can strongly reduce the required output capacitance in PowerSoC converter thanks to a very fast dynamic response. Unfortunately, these controls are prone to sub-harmonic oscillations and several parameters affect the stability of these systems. This paper derives and validates a simulation-based modeling and stability analysis of a closed-loop V 2Ic control applied to a 5 MHz Buck converter using discrete modeling and Floquet theory to predict stability. This allows the derivation of sensitivity analysis to design robust systems. The work is extended to different V 2 architectures using the same methodology.

Convertidor Cc-Cc Reductor Síncrono con Red de Cancelación de Rizado para un Amplificador de Envolvente de Alto Ancho de Banda y Alto Rendimiento

En este artículo se presenta un convertidor CC-CC de una etapa para un amplificador de envolvente de alto rendimiento y alto ancho de banda. Se ha aplicado la técnica de cancelación de rizado a un convertidor reductor síncrono para cancelar el rizado de corriente de salida y así poder disminuir la frecuencia de conmutación sin una reducción en el ancho de banda de gran señal. Se ha modelado el convertidor reductor con red de cancelación de rizado y se detalla el nuevo diseño del mismo, presentándose las ventajas del diseño propuesto así como la validación experimental. La función de transferencia del filtro de salida del convertidor reductor con red de cancelación de rizado se ha modelado y comparado con medidas experimentales, mostrando una buena correspondencia. Se ha validado experimentalmente el diseño propuesto para una frecuencia de conmutación de 4MHz para tensión de salida continua y con una referencia inusoidal. Asimismo, se incluye una validación experimental adicional, donde se compara el rendimiento de esta solución con el del diseño equivalente (mismo ancho de banda y rizado de tensión de salida) del convertidor reductor síncrono convencional.

Bidirectional multiple port dc/dc transformer based on a series resonant converter

In this paper a novel bidirectional multiple port dc/dc transformer topology is presented. The novel concept for dc/dc transformer is based on the Series Resonant Converter (SRC)topology operated at its resonant frequency point. This allows for higher switching frequency to be adopted and enables high efficiency/high power density operation. The feasibility of the proposed concept is verified on a 300W, 700 kHz three port prototype with 390V input voltage and 48V and 12V output voltages. A peak overall efficiency of 93% is measured at full load. A very good load and cross regulation characteristic of the converter is observed in the whole load range, from full load to open circuit. The sensitivity analysis of the resonant capacitance is also performed showing very slight deterioration in the converter performances when a resonant capacitor is changed ±30% of its nominal value.

Analysis and validation of a multiple output series resonant converter

In this paper a novel bidirectional multiple port dc/dc transformer topology is presented. The novel concept for dc/dc transformer is based on the Series Resonant Converter (SRC) topology operated at its resonant frequency point. This allows for higher switching frequency to be adopted and enables high efficiency/high power density operation. The feasibility of the proposed concept is verified on a 300W, 700 kHz three port prototype with 390V input voltage and 48V and 12V output voltages. A peak overall efficiency of 93% is measured at full load. A very good load and cross regulation characteristic of the converter is observed in the whole load range, from full load to open circuit. The sensitivity analysis of the resonant capacitance is also performed showing very slight deterioration in the converter performances when a resonant capacitor is changed ±30% of its nominal value.

Ripple cancellation technique applied to a synchronous buck converter to achieve very high bandwidth and very high efficiency envelope amplifier

This work presents a single stage converter for a high bandwidth and a high efficiency envelope amplifier. The current ripple cancellation technique is applied to a synchronous buck converter to cancel the output current ripple and to decrease the switching frequency without a reduction in the large signal bandwidth. The converter is modeled and the new design with ripple cancellation circuit is detailed. The advantages of the proposed design are presented and validated experimentally. The transfer function of the output filter of the buck converter with ripple cancellation circuit has been modeled and compared to measurements, showing a good correspondence. Experimental validation is provided at 4MHz of switching frequency for DC and variable output voltage for a sinusoidal and a 64QAM signal. Additional experimental validation of the efficiency improvement is provided, compared to the equivalent design (same bandwidth and output voltage ripple) of the conventional buck converter.

Multiphase Current Controlled Buck Converter with energy recycling Output Impedance Correction Circuit (OICC)

This work is related to the output impedance improvement of a Multiphase Buck converter with Peak Current Mode Control (PCMC) by means of introducing an additional power path that virtually increases the output capacitance during transients. Various solutions that can be employed to improve the dynamic behavior of the converter system exist, but nearly all solutions are developed for a Single Phase Buck converter with Voltage Mode Control (VMC), while in the VRM applications, due to the high currents, the system is usually implemented as a Multiphase Buck Converter with Current Mode Control. The Output Impedance Correction Circuit (OICC) is used to inject or extract a current n-1 times larger than the output capacitor current, thus virtually increasing n times the value of the output capacitance during the transients. Furthermore, this work extends the OICC concept to a Multiphase Buck Converter system while comparing proposed solution with the system that has n times bigger output capacitor. In addition, the OICC is implemented as a Synchronous Buck Converter with PCMC, thus reducing its influence on the system efficiency

Fuente de Alimentación para los Imanes Superconductores del Acelerador de Partículas Europeo XFEL

En este artículo se presenta la fuente de alimentación que se está diseñando para alimentar los imanes superconductores del acelerador de partículas europeo XFEL que se está construyendo en Hamburgo, cuyas características le hacen el más avanzado del mundo. Un imán superconductor es una carga muy inductiva que debe ser controlada en corriente y que presenta una caída de tensión muy baja cuando está en modo superconductor. La fuente debe ser capaz de alimentar esta carga con una alta fiabilidad e incorporar varias protecciones que protejan esta carga tan especial.

Evaluación de la vulnerabilidad sísmica urbana basada en tipologías constructivas y disposición urbana de la edificación. Aplicación en la ciudad de Lorca, región de Murcia

Actualmente, diversos terremotos han puesto de manifiesto la importancia de planificar las ciudades y la gran influencia que tiene el comportamiento de los edificios como consecuencia de los resultados de pérdidas humanas y económicas. Ante la imposibilidad de evitar la ocurrencia de terremotos y de predecirlos con un margen pequeño de tiempo para tomar acciones a corto plazo, la reducción de la vulnerabilidad de los elementos expuestos es la medida más eficaz para prevenir los daños y para evitar el desastre. Existen varios estudios anteriores de Norman B. Green (1980), Teresa Guevara López (2009 y 2012) que recogen criterios ya generalizados dentro de la bibliografía sísmica y algunos aspectos procedentes de norma sísmicas precursoras en este campo (por ejemplo, las peruanas) para establecer inicialmente unos principios urbanístico-sísmicos. Además, varios proyectos relacionados con el riesgo sísmico, RisK-Ue (2003), SERAMAR (Lars Abrahamczyk et al., 2013) han desarrollado metodologías que clasifican la vulnerabilidad de los edificios teniendo en cuenta modificadores por comportamientos y configuraciones irregulares sísmicamente. El presente trabajo desarrolla una metodología empírica para identificar y caracterizar los parámetros urbanísticos que determinan una respuesta sísmica irregular de las edificaciones, graduar su relación con el daño tras un terremoto y poder así disminuir la vulnerabilidad sísmica de las ciudades. La metodología desarrollada en esta tesis doctoral se aplica en la ciudad de Lorca, Región de Murcia. Se realiza un trabajo de campo donde se clasifican los edificios según su tipología estructural y sus parámetros urbanísticos. A través de un estudio estadístico se analiza la correlación con el daño de las edificaciones tras el terremoto del 11 de mayo de 2011. Previamente se ha hecho una clasificación de los edificios según la clase de suelo en la que se encuentran según el Eurocódigo8 (Navarro et al, 2012). Por último, se aplica la metodología para obtener una estimación de la habitabilidad de los edificios en Lorca post sismo. Para esta clasificación se ha adoptado el criterio recogido en diversas recomendaciones internacionales, la mayoría de las cuales se basan en la documentación generada por el ATC- Applied Technology Council, distinguiendo entre edificios habitables (no daño-daño no estructural) y edificios no habitables (daño estructural). ABSTRACT Currently, various earthquakes have made clear first, the importance of city planning and secondly, the great influence that has the behaviour of buildings as a consequence of the results of human and economic losses. Faced with the impossibility of avoiding the occurrence of earthquakes and predicting its with a small margin of time to take action in the short term, the reduction of the vulnerability of exposed elements is the most effective measure to prevent damage and to prevent the disaster. There are several previous studies, Norman B. Green (1980), Teresa Guevara López (2009-2012) collecting criteria already widespread within the seismic bibliography and we can find some aspects from standard seismic precursor in this field (for example, the Peruvian) to initially establish urban - seismic principles. In addition, several projects related to seismic risk, RisK-EU (2003), SERAMAR (Lars Abrahamczyk et al., 2013) have developed methodologies that classify the vulnerability of buildings taking into account modifiers for behaviours and irregular configurations in seismical terms. This paper develops an empirical methodology to identify and characterize the irregular urban parameters seismically, graduate its relationship with the building damages after an earthquake and thus reduce the seismic vulnerability of cities. The methodology developed in this thesis applies in the city of Lorca, Region of Murcia. Fieldwork where buildings are classified according to their structural type and its urban performance parameters. Through a statistical study the correlation with damage of buildings is analyzed after the earthquake of May 11, 2011. Previously a classification of the buildings has been made according to the kind of soil according to the Eurocodigo 8 (Navarro et al, 2012). Finally, you get an estimate of the building habitability in Lorca. As a result, this classification adopted the criterion contained in various international recommendations, most of which are based on the documentation published by the ATC - Applied Technology Council, habitable buildings (not damage -damage non-structural) and non habitable buildings (structural damage).

Optimizing PV use through active demand side management

With recent technological developments within the field of power conditioning and the progressive decrease of incentives for PV electricity in grid-connected markets, new operation modes for PV systems should be explored beyond the traditional maximization of PV electri city feed-in. An example can be found in the domestic sector, where the use of modern PV hybrid systems combin ed with efficient electrical appliances and demand side management strategies can significantly enhance the PV value for the user. This paper presents an active demand side management system able to displace the consumer’s load curve in response to local (PV hybrid system, user) and external conditions (external grid). In this way, th e consumer becomes an “active consumer” that can also cooperate with others and the grid, increasing even more the PV value for the electrical system.

Improving photovoltaics grid integration through short time forecasting and self-consumption

The uncertainty associated to the forecast of photovoltaic generation is a major drawback for the widespread introduction of this technology into electricity grids. This uncertainty is a challenge in the design and operation of electrical systems that include photovoltaic generation. Demand-Side Management (DSM) techniques are widely used to modify energy consumption. If local photovoltaic generation is available, DSM techniques can use generation forecast to schedule the local consumption. On the other hand, local storage systems can be used to separate electricity availability from instantaneous generation; therefore, the effects of forecast error in the electrical system are reduced. The effects of uncertainty associated to the forecast of photovoltaic generation in a residential electrical system equipped with DSM techniques and a local storage system are analyzed in this paper. The study has been performed in a solar house that is able to displace a residential user?s load pattern, manage local storage and estimate forecasts of electricity generation. A series of real experiments and simulations have carried out on the house. The results of this experiments show that the use of Demand Side Management (DSM) and local storage reduces to 2% the uncertainty on the energy exchanged with the grid. In the case that the photovoltaic system would operate as a pure electricity generator feeding all generated electricity into grid, the uncertainty would raise to around 40%.

La polémica elástico–plástico. Enfoques alternativos para abordar dos clases de problemas estructurales

Este trabajo presenta algunos de los resultados de una larga reflexión en cuyo origen se encuentra en buena medida el enorme incentivo que ha supuesto la forma polémica que usa José Luis de Miguel en sus escritos. La controversia sobre las capacidades de los enfoques elástico y plástico para resolver problemas de proyecto de estructuras me han permitido tener una mejor comprensión sobre algunos de estos, sobre los que he mantenido polémicas públicas en el pasado, y de los que traigo dos aquí a colación, a saber, - las posibilidades que aportan ambos enfoques en las tareas de análisis (y comprobación) frente a las muy diferentes tareas de proyecto (o definición), - las consecuencias que el empleo de uno u otro de los enfoques suponen para la comprobación de la capacidad de resistencia de los edificios frente a la torsión —accidental o no— inducida por la acción sísmica. En ambos casos mi discrepancia con José Luis ha sido sólo parcial, y fundamentalmente metodológica. En este trabajo incorporo mis resultados más recientes que, en el segundo caso, no han logrado por desgracia alcanzar todos los objetivos.

África en el horizonte: Cooperación técnica y universitaria, y desarrollo

La presentación se inicia con una caracterización de la situación africana desde la peerspectiva de su rápida evolución reciente con especial énfasis en los ámbitos educativos. Presenta las posibilidades de incidencia que aporta una investigación compartida con socios africanos y que esté orientda a cuestiones críticas para el desarrollo. Muesta la actividad reciente de las Universidades Españolas orientada a reeenfocar sus activos en Cooperación para el Desarrollo en dichas perspectivas, y una herramienta para la difusión y fomento de la colaboración: el Observatorio de la Cooperación Universitaria para el Desarrolo: OCUD. Presenta finalmente como varios ejemplos y resultados recientes de dicha actividad realizada desde grupos de la Universidad Politécnica de Madrid.

Desing and development of a robotic platform for the evaluation of search algorithms

Plant diseases represent a major economic and environmental problem in agriculture and forestry. Upon infection, a plant develops symptoms that affect different parts of the plant causing a significant agronomic impact. As many such diseases spread in time over the whole crop, a system for early disease detection can aid to mitigate the losses produced by the plant diseases and can further prevent their spread [1]. In recent years, several mathematical algorithms of search have been proposed [2,3] that could be used as a non-invasive, fast, reliable and cost-effective methods to localize in space infectious focus by detecting changes in the profile of volatile organic compounds. Tracking scents and locating odor sources is a major challenge in robotics, on one hand because odour plumes consists of non-uniform intermittent odour patches dispersed by the wind and on the other hand because of the lack of precise and reliable odour sensors. Notwithstanding, we have develop a simple robotic platform to study the robustness and effectiveness of different search algorithms [4], with respect to specific problems to be found in their further application in agriculture, namely errors committed in the motion and sensing and to the existence of spatial constraints due to land topology or the presence of obstacles.

On Galileo’s Tallest Column

The height at which an unloaded column will fail under its own weight was calculated for first time by Galileo for cylindrical columns. Galileo questioned himself if there exists a shape function for the cross-section of the column with which the latter can attains a greater height than the cylindrical column. The problem is not solved since then, although the definition of the so named “constant maximum strength” solids seems to give an affirmative answer to Galileo’s question, in the form of shapes than can attains infinite height, even when loaded with a useful load at the top. The main contribution of this work is to show that Galileo’s problem is (i) an important problem for structural design theory of buildings and other structures, (ii) not solved by the time being in any sense and (iii) a interesting problem for mathematicians involved in related but very different problems (as Euler’s tallest column). A contemporary formulation of the problem is included as a result of a research on the subject.

On the layout of a least weight single span structure with uniform load. Some comments and improvements

Beghini et al (Struct Multidisc Optim doi:10.1007/s00158-013-1030-6, 2013) have published a very interesting paper arriving to practically the same nearly optimal solutions for the so named “bridge prob- lem” that the Writers published a year before, but using an alternative and remarkable approach to the problem. In spite of this general agreement, the Writers think that some details of the paper can be improved and there are results that can be given a clear and mean- ingful interpretation thanks to an old and practically unknown theorem on optimal slenderness.