Robust H8 design for resonant control in a CVCF inverter application over load uncertainties

CVCF (constant voltage, constant frequency) inverters are electronic devices used to supply AC loads from DC storage elements such as batteries or photovoltaic cells. These devices are used to feed different kinds of loads; this uncertainty requires that the controller fulfills robust stability conditions while keeping required performance. To address this, a robust H8 design is proposed based on resonant control to track a pure sinusoidal voltage signal and to reject the most common harmonic signals in a wide range of loads. The design is based on the definition of performance bounds in error signal and weighting functions for covering most uncertainty ranges in loads. Experimentally, the H8 controller achieves high-quality output voltage signal with a total harmonic distortion less than 2%Peer ReviewedPostprint (published version

Digital repetitive control under varying frequency conditions

Premi extraordinari doctorat curs 2011-2012, àmbit d’Enginyeria IndustrialThe tracking/rejection of periodic signals constitutes a wide field of research in the control theory and applications area and Repetitive Control has proven to be an efficient way to face this topic; however, in some applications the period of the signal to be tracked/rejected changes in time or is uncertain, which causes and important performance degradation in the standard repetitive controller. This thesis presents some contributions to the open topic of repetitive control working under varying frequency conditions. These contributions can be organized as follows: One approach that overcomes the problem of working under time varying frequency conditions is the adaptation of the controller sampling period, nevertheless, the system framework changes from Linear Time Invariant to Linear Time-Varying and the closed-loop stability can be compromised. This work presents two different methodologies aimed at analysing the system stability under these conditions. The first one uses a Linear Matrix Inequality (LMI) gridding approach which provides necessary conditions to accomplish a sufficient condition for the closed-loop Bounded Input Bounded Output stability of the system. The second one applies robust control techniques in order to analyse the stability and yields sufficient stability conditions. Both methodologies yield a frequency variation interval for which the system stability can be assured. Although several approaches exist for the stability analysis of general time-varying sampling period controllers few of them allow an integrated controller design which assures closed-loop stability under such conditions. In this thesis two design methodologies are presented, which assure stability of the repetitive control system working under varying sampling period for a given frequency variation interval: a mu-synthesis technique and a pre-compensation strategy. On a second branch, High Order Repetitive Control (HORC) is mainly used to improve the repetitive control performance robustness under disturbance/reference signals with varying or uncertain frequency. Unlike standard repetitive control, the HORC involves a weighted sum of several signal periods. With a proper selection of the associated weights, this high order function offers a characteristic frequency response in which the high gain peaks located at harmonic frequencies are extended to a wider region around the harmonics. Furthermore, the use of an odd-harmonic internal model will make the system more appropriate for applications where signals have only odd-harmonic components, as in power electronics systems. Thus an Odd-harmonic High Order Repetitive Controller suitable for applications involving odd-harmonic type signals with varying/uncertain frequency is presented. The open loop stability of internal models used in HORC and the one presented here is analysed. Additionally, as a consequence of this analysis, an Anti-Windup (AW) scheme for repetitive control is proposed. This AW proposal is based on the idea of having a small steady state tracking error and fast recovery once the system goes out of saturation. The experimental validation of these proposals has been performed in two different applications: the Roto-magnet plant and the active power filter application. The Roto-magnet plant is an experimental didactic plant used as a tool for analysing and understanding the nature of the periodic disturbances, as well as to study the different control techniques used to tackle this problem. This plant has been adopted as experimental test bench for rotational machines. On the other hand, shunt active power filters have been widely used as a way to overcome power quality problems caused by nonlinear and reactive loads. These power electronics devices are designed with the goal of obtaining a power factor close to 1 and achieving current harmonics and reactive power compensation.Award-winningPostprint (published version

Clasificación de la matematización de la economía desde un punto de vista socioepistemológico

La ciencia económica, al igual que las ciencias físicas analizan y predicen los diferentes tipos de fenómenos, ésta última utiliza el Cálculo como herramienta de predicción. En la búsqueda de entender ¿cómo el Cálculo originado en la práctica social de predecir se incorpora a otras prácticas sociales asociadas a la Economía? encontramos cómo los economistas clasifican la matematización de la economía en base al uso de diferentes conceptos matemáticos. Considerando el análisis socioepistemológico de la matematización de la economía y el análisis a posteriori de las situaciones que se le aplicaron a estudiantes de economía, podemos proponer desde nuestra visión socioepistemológica una evolución distinta del proceso de matematización de la ciencia económica, considerando el uso de herramientas y las prácticas sociales entre otros elementos

Práctica social de predecir y el uso de herramientas en estudiantes de economía

El papel que juega el Cálculo infinitesimal en los cursos que se imparten a nivel superior en las diferentes licenciaturas a través de su planes y programas de estudio, y en las bibliografías que utilizan para la enseñanza de éste, nos dicen que el cálculo debe ser una herramienta para resolver diferentes problemáticas que se le presenten tanto en la licenciatura así como en el ejercicio de su profesión, éstas pretensiones desde nuestro punto de vista no se están logrando. En base a la problemática anterior se formuló una epistemología inicial para diseñar situaciones de variación que permitan a los estudiantes reconstruir conceptos microeconómicos a través de supuestos epistemológicos que justifican la naturaleza de éstas y a su vez consideran que el funcionamiento mental debe estar en correspondencia con la modelación y el uso de herramientas predictoras

Energy management strategies for hybrid energy storage systems based on filter control: analysis and comparison

The Filter-Based Method (FBM) is one of the most simple and effective approaches for energy management in hybrid energy storage systems (HESS) composed of batteries and supercapacitors (SC). The FBM has evolved from its conventional form in such a manner that more flexibility and functionalities have been added. A comparative study and analysis of the most recent and relevant proposals based on the FBM for HESS are provided in this paper. In this way, the improvements for this energy management system (EMS) are in the form of adaptive filters, rules, Fuzzy logic control, sharing coefficients, and additional control loops. It is shown how these enhancements seek to avoid the premature degradation of the storage devices that are caused by deep discharge, overcharge, and fast current variations in the case of batteries and overcharge in the SC case. Therefore, the enhancements are focused on keeping the battery and SC working within safe operational limits. This paper presents new comparisons regarding the SoC evolution in the storage devices, specifically how the SC SoC is used in the EMS to establish the power sharing. Numerical simulations are added to compare the performance of the different EMS structures. The analysis of the results shows the effectiveness of the FBM in achieving power allocation and how the latest proposed improvements help to add flexibility to HESS as well as to avoid premature degradation of the storage devicesPeer ReviewedPostprint (published version

Prevalencia de síndrome premenstrual en estudiantes de medicina de la Universidad Militar Nueva Granada

El Síndrome premenstrual (SPM) es el término utilizado para una variedad de síntomas físicos y emocionales cíclicos que se producen en la fase lútea del periodo menstrual. La prevalencia exacta de SPM se desconoce, pero según publicaciones internacionales se estima que se presenta en un 20 a 40% de las mujeres en edad reproductiva, representando una causa importante de limitaciones en el desempeño laboral y académico de una buena parte de la población femenina. A la fecha, en nuestro país no existen estudios prospectivos para definir la dimensión del problema en términos de prevalencia y severidad del SPM en población estudiantil. Se pretende realizar un estudio observacional de las mujeres entre 18 y 25 años de edad, estudiantes de la carrera de medicina de la universidad militar nueva granada con el fin de determinar la frecuencia del SPM, los factores de riesgo y la severidad del mismo. Se realizara una selección mediante criterios de inclusión y de exclusión predeterminados y un muestreo a conveniencia, luego del cual, a quienes sean aptas para ingresar al estudio, se les realizaran previo consentimiento informado por escrito una encuesta inicial para información demográfica y de factores de riesgo, luego se realizara una valoración de la salud física, mental, y de la afectación de la misma mediante el uso estudio médico Short Form 36 (SF 36) y además se solicitara el diligenciamiento del registro diario de sintomatología diseñado para tal fin (DRSP) para tres ciclos menstruales, se realizara seguimiento mensual con recolección de datos y determinación de adherencia. Para el diagnostico se tendrán en cuenta los criterios del DSM I

Validation of calibrated energy models: Common errors

Nowadays, there is growing interest in all the smart technologies that provide us with information and knowledge about the human environment. In the energy ¿eld, thanks to the amount of data received from smart meters and devices and the progress made in both energy software and computers, the quality of energy models is gradually improving and, hence, also the suitability of Energy Conservation Measures (ECMs). For this reason, the measurement of the accuracy of building energy models is an important task, because once the model is validated through a calibration procedure, it can be used, for example, to apply and study different strategies to reduce its energy consumption in maintaining human comfort. There are several agencies that have developed guidelines and methodologies to establish a measure of the accuracy of these models, and the most widely recognized are: ASHRAE Guideline 14-2014, the International Performance Measurement and Veri¿cation Protocol (IPMVP) and the Federal Energy Management Program (FEMP). This article intends to shed light on these validation measurements (uncertainty indices) by focusing on the typical mistakes made, as these errors could produce a false belief that the models used are calibrated

Towards a new generation of building envelope calibration

Building energy performance (BEP) is an ongoing point of reflection among researchers and practitioners. The importance of buildings as one of the largest activators in climate change mitigation was illustrated recently at the United Nations Framework Convention on Climate Change 21st Conference of the Parties (COP21). Continuous technological improvements make it necessary to revise the methodology for energy calculations in buildings, as has recently happened with the new international standard ISO 52016-1 on Energy Performance of Buildings. In this area, there is a growing need for advanced tools like building energy models (BEMs). BEMs should play an important role in this process, but until now there has no been international consensus on how these models should reconcile the gap between measurement and simulated data in order to make them more reliable and affordable. Our proposal is a new generation of models that reconcile the traditional data-driven (inverse) modelling and law-driven (forward) modelling in a single type that we have called law-data-driven models. This achievement has greatly simpli¿ed past methodologies, and is a step forward in the search for a standard in the process of calibrating a building energy model

Flow and fracture in water-saturated, unconstrained granular beds

International audienceSpecialty section: This article was submitted to Interdisciplinary Physics, a section of the journal Frontiers in Physics The injection of gas in a liquid-saturated granular bed gives rise to a wide variety of invasion patterns. Many studies have focused on constrained porous media, in which the grains are fixed in the bed and only the interstitial fluid flows when the gas invades the system. With a free upper boundary, however, the grains can be entrained by the ascending gas or fluid motion, and the competition between the upward motion of grains and sedimentation leads to new patterns. We propose a brief review of the experimental investigation of the dynamics of air rising through a water-saturated, unconstrained granular bed, in both two and three dimensions. After describing the invasion pattern at short and long time, a tentative regime-diagram is proposed. We report original results showing a dependence of the fluidized zone shape, at long times, on the injection flow rate and grain size. A method based on image analysis makes it possible to detect not only the fluidized zone profile in the stationary regime, but also to follow the transient dynamics of its formation. Finally, we describe the degassing dynamics inside the fluidized zone, in the stationary regime. Depending on the experimental conditions, regular bubbling, continuous degassing, intermittent regime or even spontaneous flow-to-fracture transition are observed