A virtual power plant model for time-driven power flow calculations

This paper presents the implementation of a custom-made virtual power plant model in OpenDSS. The goal is to develop a model adequate for time-driven power flow calculations in distribution systems. The virtual power plant is modeled as the aggregation of renewable generation and energy storage connected to the distribution system through an inverter. The implemented operation mode allows the virtual power plant to act as a single dispatchable generation unit. The case studies presented in the paper demonstrate that the model behaves according to the specified control algorithm and show how it can be incorporated into the solution scheme of a general parallel genetic algorithm in order to obtain the optimal day-ahead dispatch. Simulation results exhibit a clear benefit from the deployment of a virtual power plant when compared to distributed generation based only on renewable intermittent generation.Peer ReviewedPostprint (published version

Reliability analysis of distribution systems with photovoltaic generation using a power flow simulator and a parallel Monte Carlo approach

This paper presents a Monte Carlo approach for reliability assessment of distribution systems with distributed generation using parallel computing. The calculations are carried out with a royalty-free power flow simulator, OpenDSS (Open Distribution System Simulator). The procedure has been implemented in an environment in which OpenDSS is driven from MATLAB. The test system is an overhead distribution system represented by means of a three-phase model that includes protective devices. The paper details the implemented procedure, which can be applied to systems with or without distributed generation, includes an illustrative case study and summarizes the results derived from the analysis of the test system during one year. The goal is to evaluate the test system performance considering different scenarios with different level of system automation and reconfiguration, and assess the impact that distributed photovoltaic generation can have on that performance. Several reliability indices, including those related to the impact of distributed generation, are obtained for every scenario.Postprint (published version

A Solid State Transformer model for power flow calculations

This paper presents the implementation of a Solid State Transformer (SST) model in OpenDSS. The goal is to develop a SST model that could be useful for assessing the impact that the replacement of the conventional iron-and-copper transformer with the SST can have on the distribution system performance. Test distribution systems of different characteristics and size have been simulated during different time periods. The simulations have been carried out assuming voltage-dependent loads and considering that power flow through either the HV/MV substation transformer or any of the MV/LV distribution transformers can be bidirectional. Simulation results prove that a positive impact should be expected on voltages at both MV and LV levels, but the efficiency of current SST designs should be improved.Postprint (author's final draft

Las relaciones interpersonales en el marco de la familia: Algunas reflexiones metodológicas.

This paper seeks to identify and discuss some of the problems involved in the study of the psychosocial aspects of aging within the family. It sets out to provide a framework for methodological debate. A number of ideas are put forward as tentative proposal for solving certain problems, e.g. the search for comparative data, from which is derived the principle that the sample should be made up from different data sources related to the same field of study. Clearly the onus is upon the individual researcher to decide upon the most suitable solution in each case. Our analysis aims to draw attention to the need to conduct research in close accordance with scientific procedure, in spite of the dificulties which might arise in the context within which the research is being carried out

Defensa y salvaguarda de las artesanías tradicionales y populares. Formas de cooperación para esta defensa

En número dedicado a: Arte popular en América y España. Índice

Las relaciones interpersonales en el marco de la familia: algunas reflexiones metodológicas

This paper seeks to identify and discuss some of the problems involved in the study of the psychosocial aspects of aging within the family. It sets out to provide a framework for methodological debate. A number of ideas are put forward as tentative proposal for solving certain problems, e.g. the search for comparative data, from which is derived the principle that the sample should be made up from different data sources related to the same field of study. Clearly the onus is upon the individual researcher to decide upon the most suitable solution in each case. Our analysis aims to draw attention to the need to conduct research in close accordance with scientific procedure, in spite of the dificulties which might arise in the context within which the research is being carried out.Este articulo pretende identificar y comentar algunos puntos problemáticos de la investigación de aspectos psico-sociales del envejecimiento en el marco de la familia. Está concebido como una base de discusión metodológica. Algunas de las reflexiones se presentan como propuestas tentativas para la solución de determinados problemas como, p.e., la búsqueda de información contrastada, de la que se deriva que la muestra debiera estar formada por diferentes fuentes de informzación sobre un mismo tema. Evidentemente, corresponde al investigador decidir en cada caso las mejores vias de solución. La finalidad de nuestra reflexión consiste en llamar la atención sobre la necesidad de realizar proyectos de investigación que se ajusten con la mayor precisión al procedimiento científico, a pesar de las dficultades que se pudieran presentar en función del marco en que se realicen

Control del potencial de erosión de un suelo artificial, proveniente de una planta de aguas residuales domésticas

Proyecto de Graduación (Licenciatura en Ingeniería en Construcción) Instituto Tecnológico de Costa Rica, Escuela de Ingeniería en Construcción, 2016.The geotechnical characterization of an artificial soil has been made. The mud used was taken from a domestic waste water treatment plant. For evaluating this characterization, tests on consistency limits, granulometry through hydrometers, Proctor standard, permeability and specific gravity were made. An environmental characterization of this artificial soil was also made. Data from a parallel investigation for a possible usage of this material in agricultural activities of this same material was used for this characterization. A complementary part of this investigation is focused in analyzing the erosion potential of this artificial soil due to the effects of rainfall. In order to measure soil erosion, a hydrologic simulator was designed in order to control the intensity of rainfall that could reproduce precipitations able to produce soil erosion. The simulator has a hydraulic system that controls the pressure of its four sprinklers. This way, intensity inside the simulator can be quantified. An acrylic tray with an exposed area of 0, 25 m2 and a thickness of 0, 1 m, was built in order to place the soil material and to simulate a slope. This tray has a canoe in its base that allows measuring runoff and soil erosion; as well as holes of the bottom where the infiltration was measured. Finally, many tests were made by adding different kinds of cement to this artificial soil material. The purpose of this was to find the optimal percentage of cement to lower erosion of the new artificial soil taking into consideration price minimal costs as well