I.A.C. Instituto de Astrofísica de Canarias

Peer Reviewe

La Teoria de la Relativitat

Peer Reviewe

I.A.C. Instituto de Astrofísica de Canarias

Peer Reviewe

Solar energy systems course for Energy Engineering students in the context of the European higher education area

The Bologna Process is a voluntary intergovernmental European cooperation initiative that led to the creation of the named European Higher Education Area (EHEA). EHEA was formed to promote mobility, increase academic recognition and attract students and staff from around the world to Europe. In this framework, since 2009, the Barcelona College of Industrial Engineering (Escuela Universitaria de Ingeniería Técnica Industrial de Barcelona – EUETIB) of the Technical University of Catalonia – BarcelonaTech (UPC) is offering the 4-year Bachelor Degree in Energy Engineering since 2009 with a total number of ECTS credits of 240. Current article deals with the inclusion of the sizing and design of solar energy systems in the context of this degree. In particular, and although this topic was eventually abandoned in the initial degree curriculum, the paper deals with the development of a 3rd-year course, Energy Integration, that focuses on this topic.Peer ReviewedPostprint (published version

Comparative aspects in control strategies for hybrid DC-DC converters

Linear-switching 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.Postprint (published version

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

El apropiado modelizado dinámico lineal de filtros de tiempo continuo (CTFs) con lazos de sintonía automática debe llevarse a cabo para poder asegurar la estabilidad cuando queremos diseñar controladores de lazo mejorados. Con este objetivo, a partir de un análisis general y sistemático que permite obtener un modelo incremental linealizado equivalente para pequeña señal, se derivan las funciones de transferencia entre las variables de salida y las tensiones de control. Ello permite, a continuación, un posterior diseño de los compensadores de lazo con mejora en la estabilidad y en las prestaciones dinámicas. Este procedimiento sistemático permite conseguir mejores controladores para los dos lazos de control involucrados. Sin embargo, los CTFs con lazos de sintonía o ajuste automático son sistemas realimentados no lineales que tienden a ser inestables. Es más, fenómenos no lineales, que no pueden predecirse con un enfoque mediante modelos de pequeña señal orientados al diseño, pueden ser observados en este tipo de sistemas de sintonía. El propósito de este trabajo es poner de manifiesto que cuando se varían los parámetros de control, el sistema puede presentar diferentes tipos de fenómenos no lineales dinámicos tales como bifurcaciones y comportamiento caótico, que no pueden ser predichos por el modelo en pequeña señal orientado al diseño.The 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.Peer Reviewe

The use of power DC-DC converters and gyrator structures for Energy Processing in Photovoltaic Solar Facilities

Este artículo ofrece una clasificación de las estructuras giradoras de potencia conmutadas de alta eficiencia (high efficiency switching power-gyrator structures), y su uso como células para el procesado de energía en instalaciones solares fotovoltaicas. Teniendo en cuenta las propiedades de estas topologías presentadas en el artículo, su inclusión en instalaciones solares, permite aumentar el rendimiento de toda la instalación. Así pues, el diseño, simulación e implementación de un girador de potencia de tipo G se lleva a cabo a lo largo de todo el texto. Además, con el fin de obtener la máxima potencia del panel solar fotovoltaico, un sistema de seguimiento del punto de máxima potencia (MPPT, maximum power point tracking) es necesario en el camino de procesado de energía. Por lo tanto, la aplicación práctica llevada a cabo incluye un circuito de control del girador de potencia con el fin de realizar el seguimiento del punto de máxima potencia antes mencionado del panel solar fotovoltaico al que está conectado

Design of an on-chip hybrid DC/DC converter

This paper presents 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 DC/DC 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 second 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.Postprint (published version

LEGION-based image segmentation by means of spiking neural networks using normalized synaptic weights implemented on a compact scalable neuromorphic architecture

© . This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/LEGION (Locally Excitatory, Globally Inhibitory Oscillator Network) topology has demonstrated good capabilities in scene segmentation applications. However, the implementation of LEGION algorithm requires machines with high performance to process a set of complex differential equations limiting its use in practical real-time applications. Recently, several authors have proposed alternative methods based on spiking neural networks (SNN) to create oscillatory neural networks with low computational complexity and highly feasible to be implemented on digital hardware to perform adaptive segmentation of images. Nevertheless, existing SNN with LEGION configuration focus on the membrane model leaving aside the behavior of the synapses although they play an important role in the synchronization of several segments by self-adapting their weights. In this work, we propose a SNN-LEGION configuration along with normalized weight of the synapses to self-adapt the SNN network to synchronize several segments of any size and shape at the same time. The proposed SNN-LEGION method involves a global inhibitor, which is in charge of performing the segmentation process between different objects with different sizes and shapes on time. To validate the proposal, the SNN-LEGION method is implemented on an optimized scalable neuromorphic architecture. Our preliminary results demonstrate that the proposed normalization process of the synaptic weights along with the SNN-LEGION configuration keep the capacity of the LEGION network to separate the segments on time, which can be useful in video processing applications such as vision processing systems for mobile robots, offering lower computational complexity and area consumption compared with previously reported solutions.The authors would like to thank the Consejo Nacional de Ciencia y Tecnologia (CONACyT) and the IPN for the financial support to realize this work under project SIP-20180251. This work was also supported in part by the Spanish Ministry of Science and Innovation and the European Social Fund (ESF) under Projects TEC2011-27047 and TEC2015-67278-R.Peer ReviewedPostprint (author's final draft

Approach to the implementation and modeling of LDO-assisted DC-DC voltage regulators

This paper presents the design of an LDO-assisted DC-DC voltage regulator in Cadence Virtuoso® based on a 350-nm CMOS technology. This kind of voltage regulator consists of a switching converter together with a classic or LDO (low dropout) linear voltage regulator. While the linear regulator provides the constant output voltage, the switching converter conducts nearly all the current provided to the output load, and keeping the regulator current close to zero where the higher efficiency is achieved. In addition, this paper shows the modeling in Matlab/Simulink. Notice that, this modeling is mandatory in order to predict and assure the stability of the circuit. In addition, it will help to improve the transient response and performance of the circuit.Peer ReviewedPostprint (published version