Improved modelling of microgrid distributed energy resources with machine learning algorithms

Mención Internacional en el título de doctorRenewable energy technologies are being increasingly adopted in many countries around the world. However, the deployment of these power generation systems is becoming more diverse than ever, from small generation units in individual houses to massive power production plants. In that spectrum, distributed energy resources (DERs) cover systems from the low- to the middle-power ranges. The operation, control and assessment of these technologies is becoming more complex, and structures such as microgrids (MGs) may provide a suitable ecosystem to manage them. The beginning of this thesis covers the fundamentals of MG systems. A review was conducted by analysing the MG in a layer perspective, where each layer corresponded to a topic such as operation, business or standards, among others. The advancements in electronics, computer power and storage capability have created a paradigm in which massive amounts of data are generated and computed. The electrical sector has introduced many data acquisition technologies to assess the grid and its components. Classical modelling approaches have applied physical, chemical or electrical algorithms to model the behaviours of DERs. Nevertheless, with the extensive amount of information at our disposal, data-driven techniques such as machine learning (ML) may provide more individualised models to simulate the behaviour of these power generation technologies with the particularities of both their components and their location. Following the MG review, its power generation technologies were analysed. The information from 1,618 MGs around the world have been aggregated and studied. Also, two MG infrastructure model generators have been proposed (considering the infrastructure as the power generation technology and their rated power of an MG.). One of the models is based on the statistical data aggregated in tables and the other is based on ML techniques. The latter, which provides more particularised results, is able to generate the most typical MG infrastructure for a given location and segment of operation. Ideally, each of the DERs of a MG should be modelled, but, given the time constraints of a PhD, only the principal renewable generation technologies have been studied. Hence, ML models of photovoltaic (PV) systems plus a battery and wind energy conversion systems (WECS) have been proposed. Various ML models for PV systems were developed in two studies. First, an ML model for PV power estimation was performed using data from two real PV farms and validated using deterministic models from the literature. The ML algorithm was performed using neural networks and automatic strategies to clean the data. Neural network accuracy when trained and tested in the same location yields solid results which can be applied in performance ratio tools for PV power stations. In the second study, various mathematical models are proposed. This study provides several models for computing the annual optimum tilt angle for both fixed PV arrays and solar collectors. The optimum tilt algorithm proposed can be calculated in the absence of meteorological or software tools. To generate these models, data were collected from 2,551 sites across the world. A regression analysis with polynomial fitting, neural networks and decision trees was performed. Despite the better performance of the ML models, the ease of use of polynomial algorithms is recommended for those sites with no access to computational tools or meteorological data. The performances of the models were validated using previous research algorithms. Also, an ML algorithm was proposed to estimate the state of charge of a lithium-ion battery. The available capacity in a battery is an important feature when operating these kinds of systems. Given the complex behaviours of a battery, data-driven algorithms are able to capture the dynamic behaviours of a battery. Based on the data obtained in different experiments performed in a laboratory, an ensemble method, gradient boosting algorithm, was trained to model the state of charge of the battery. Even though the state of health of the storage system was below the theoretical life expectancy, the model was able to provide solid results. The model was validated with non-trained data. Finally, data-driven techniques were applied to model different elements of WECS. The first study provided two power coefficient algorithms, one based on polynomial fitting and another based on neural networks. To train the models, data from a corrected blade element momentum algorithm was used and three sets of data representing different wind turbine ranges, from 2 to 10 MW, were generated. Both models were validated with three datasets of real wind turbines and compared with the existing literature equations. Compared to previous equations, errors were reduced by at least 55% with the best numerical approximation from the literature. This type of reduction has a great impact for WECS dynamic and transient studies. The second study proposed for WECS develops three different ML models: one estimates the power of individual WECS, the second aggregates the data from all the WECS and estimates their power and the last one estimates the power of an entire wind farm. Given the stochastic and dynamic behaviours of the systems modelled, data pre-processing should be performed. Along with default cleaning techniques, a Student-t copula has been proposed so outliers can be automatically removed. Results show that the neural network algorithms’ performances for the three models can be improved without excessive manual intervention in the development process. Traditionally, electrical, physical and chemical models have been applied to mimic the behaviour of power systems. Now, with the power of computer and storage systems, a new era of more customised models has begun. It is time to review the existing models and provide better solutions by using ML techniques. In this thesis, only a few DERs have been modelled, but the results show that huge improvements can be made and future work in this subject should be done. The ML models proposed can be applied either as individual models for performance assessment of each DER or as a complementary tool to dynamic or static studies, unit commitment and planning software, among others.Programa de Doctorado en Ingeniería Eléctrica, Electrónica y Automática por la Universidad Carlos III de MadridPresidente: Carlos Veganzones Nicolás.- Secretaria: María Ángeles Moreno López de Saa.- Vocal: Athanasios Kolio

Del movimiento campesino al asociacionismo rural en el centro de Veracruz

The objective of this research was to analyze the historical factors that had an impact in the origin of the collective action of smallholder coffee farmers, and to study the process they followed to shape their peasant identity through agroecology to become constituted in the civil association Vinculación y Desarrollo Agroecológico en Café (VIDA) and to consolidate their collective work. The research is both theoretical and practical, and it was approached through literature review and field work by applying fifty-two semi-structured interviews and eight testimonies of social stakeholders. The emergence of VIDA was induced by the union, Unión General Obrero Campesina y Popular (UGOCP), in Ixhuatlán del Café; the merger with social leaders from Cosautlán de Carvajal; and the Universidad Autónoma Chapingo, who worked jointly to characterize coffee-producing territories and traditional agricultural knowledge, and to systematize the agroecological management of the coffee plantation. The result was the procurement of differentiated coffee for alternative international and national commerce. The mobilization of coffee farmers through their collective action allowed them to connect to other national and international institutional stakeholders, which provided organizational and economic efficiency and strengthened their political position in defense of the agrocological peasant way of life.El objetivo de la investigación fue analizar los factores históricos que incidieron en el origen de la acción colec­tiva de los pequeños cafeticultores, y estudiar el proceso que siguieron para forjar su identidad campesina por medio de la agroecología constituirse en la asociación civil Vinculación y Desarrollo Agroecológico en Café (VIDA) y consolidar su trabajo colectivo. La investigación es tanto teórica como práctica, se abordó mediante la revisión documental y trabajo de campo, lográndose aplicar cincuenta y dos entrevistas semiestructuradas y ocho testimonios de los actores sociales. El surgimiento de VIDA fue inducido por la Unión General Obrero Campesina y Popular (UGOCP) en Ixhuatlán del Café; la unión a líderes sociales de Cosautlán de Carvajal; y la Universidad Autónoma Chapingo, quienes trabajaron en conjunto para caracterizar los territorios cafeta­leros y los saberes tradicionales agrícolas, y sistematizar el manejo agroecológico del cafetal. El resultado fue la obtención de un café diferenciado para el comercio alternativo internacional y nacional. La movilización de los cafeticultores mediante su acción colectiva permitió vincularse a otros actores institucionales nacionales e internacionales. Los cuales les brindaron eficiencia organizacional y económica, y fortalecieron su postura política en defensa de la vida campesina agroecológica

Wind turbine power coefficient models based on neural networks and polynomial fitting

The power coefficient parameter represents the aerodynamic wind turbine efficiency. Since the 1980s, several equations have been used in the literature to study the power coefficient as a function of the tip speed ratio and the pitch angle. In this study, these equations are reviewed and compared. A corrected blade element momentum algorithm is used to generate three sets of data representing different ranges of wind turbines, going from 2 to 10 MW. With this information, two power coefficient models are proposed and shared. One model is based on a polynomial fitting, whereas the other is based on neural network techniques. Both were trained with the blade element momentum model output data and showed good behaviour for all operating ranges. In the results, compared to all the algorithms found in the literature, the proposed models reduced the power coefficient error by at least 55% compared to the best numerical approximation from the literature. An error reduction in the power coefficient parameter may have a large impact on many wind energy conversion system studies, such as those treating dynamic and transient behavioursPublicad

Influence of news interest, payment of digital news, and primary news sources in media trust. A moderated mediation model

This study investigated the mediating effect of the primary type of news source used by audiences on the relationship between inter-est in news and media trust. In addition, this study explored the moderating role of payments for digital news. Based on 12,252 respondents from six countries (the United Kingdom, the United States, France, Spain, Germany, and Finland), the study confirms that the type of news source chosen by audiences significantly mediates the relationship between interest and media trust. This mediation is not moderated by the payments for digital news. Furthermore, there is no direct association between payment and media trust, although data shows that direct effect of interest in media trust is slightly moderated by payment for digital new

Microgrid and Distributed Energy Resources Standards and Guidelines Review: Grid Connection and Operation Technical Requirements

This article belongs to the Special Issue Analysis of Microgrid Integrated with Renewable Energy SystemIn this review, the state of the art of 23 distributed generation and microgrids standards has been analyzed. Among these standards, 18 correspond mainly to distributed generation while five of them introduce the concept of microgrid. The following topics have been considered: interconnection criteria, operating conditions, control capabilities, power quality, protection functions and reference variables. The revised national standards cover ten countries on four continents, which represents 80% of the countries with the largest installed renewable capacities. In addition, eight other relevant international standards have been analyzed, finding IEEE 1547 as the most comprehensive standard. It is identified a clear need to define a common framework for distributed energy resources (DERs) and microgrid standards in the future, wherein topics, terminology, and values are expressed in a manner that may widely cover the entire diversity in a way similar to how it has already been expressed at the network transport level by the ENTSO-E codes

Incidencia del Objetivo de Desarrollo Sostenible 4 en Instituciones de Educación Superior: percepción de estudiantes de la Universidad Técnica de Machala: Incidência do Objetivo de Desenvolvimento Sustentável 4 em instituições de ensino superior: percepção dos alunos da Universidade Técnica de Machala / Incidence of Sustainable Development Goal 4 in higher education institutions: perception of students of the Technical University of Machala

La educación en función al Objetivo de Desarrollo Sostenible 4 proporciona varios lineamientos para una educación de calidad, constando de metas e indicadores aplicados en las Instituciones de educación superior a fin de lograr mejoras académicas con miras a largo plazo, que puedan beneficiar e incrementar la calidad de vida de la población. El objetivo de esta investigación se centra en la valoración de la percepción por parte de los estudiantes de la Universidad Técnica de Machala en la provincia de El Oro, vinculando la trayectoria académica hacia la sostenibilidad que ejerce la globalización hoy en día. El tipo de investigación que se empleó es descriptivo con corte transversal, a través de un análisis de resultados que fueron arrojados mediante el uso del software estadístico Stata para así obtener un modelo econométrico de Regresión Lineal Múltiple con datos extraídos de encuestas dirigidas a la comunidad estudiantil de la Facultad de Ciencias Empresariales. RESUMOA educação baseada no Objetivo de Desenvolvimento Sustentável 4 traz diversas diretrizes para uma educação de qualidade, consistindo em metas e indicadores aplicados nas instituições de ensino superior para alcançar melhorias acadêmicas com visão de longo prazo, que podem beneficiar e aumentar a qualidade de vida da população. O objetivo desta pesquisa se concentra na avaliação da percepção dos alunos da Universidade Técnica de Machala, na província de El Oro, vinculando a trajetória acadêmica à sustentabilidade que a globalização exerce hoje. O tipo de pesquisa utilizada é descritiva com corte transversal, através de uma análise dos resultados que foram lançados através do uso do software estatístico Stata para obter um modelo econométrico de Regressão Linear Múltipla com dados extraídos de pesquisas direcionadas ao comunidade estudantil da Faculdade de Ciências Empresariais. ABSTRACTEducation according to the Sustainable Development Goal 4 provides several guidelines for quality education, consisting of goals and indicators applied in higher education institutions in order to achieve long-term academic improvements that can benefit and increase the quality of life of the population. The objective of this research focuses on the assessment of the perception of the students of the Technical University of Machala in the province of El Oro, linking the academic trajectory towards the sustainability that globalization exerts today. The type of research used is descriptive with transversal cut, through an analysis of the results that were obtained through the use of the statistical software Stata to obtain an econometric model of Multiple Linear Regression with data extracted from surveys directed to the student community of the Faculty of Business Sciences

Educación agrícola, pueblos indios y nueva ruralidad en los umbrales del siglo XXI

1 archivo PDF (429 páginas)Los trabajos que integran este volumen son resultado de la selección de ensayos y ponencias realizados por los cursantes del Diplomado en Derecho Rural, Derecho Ambiental y Derechos de los Pueblos Indios (celebrado entre septiembre y diciembre de 1998), así como de las conferencias y ponencias presentadas en el Primer Coloquio Internacional. Los Pueblos Indios, la Educación Agrícola y la Nueva Ruralidad en los umbrales del Siglo XXI

Identification of patterns for space-time event networks

This paper provides new tools for analyzing spatio-temporal event networks. We build time series of directed event networks for a set of spatial distances, and based on scan-statistics, the spatial distance that generates the strongest change of event network connections is chosen. In addition, we propose an empirical random network event generator to detect significant motifs throughout time. This generator preserves the spatial configuration but randomizes the order of the occurrence of events. To prevent the large number of links from masking the count of motifs, we propose using standardized counts of motifs at each time slot. Our methodology is able to detect interaction radius in space, build time series of networks, and describe changes in its topology over time, by means of identification of different types of motifs that allows for the understanding of the spatio-temporal dynamics of the phenomena. We illustrate our methodology by analyzing thefts occurred in Medellín (Colombia) between the years 2003 and 2015.Work supported by Red de Violencia y Criminalidad - Universidad Nacional Abierta y a Distancia UNAD, Bogotá Colombia and Universidad Nacional de Colombia sede Bogotá

Interculturalidad y currículum intercultural para la educación superior en México

In this article, the concept of interculturality is exposed, as well as its importance at present in order to move towards the construction of an intercultural nation, it is taken up and analyzed as the first point towards this purpose, the way in which intercultural universities are implemented in Mexico and its educational model, based on this, an intercultural curriculum proposal for higher education institutions that responds to the social and cultural contexts of where they are located is outlined. Finally, it is stated that education must respond to the social needs and demands of different cultural groupsEn el artículo se expone el concepto de interculturalidad, así como su importancia en la actualidad para lograr encaminarnos hacia la construcción de una nación intercultural, se retoma y analiza como primer punto hacia este fin, la forma en que se implementan las universidades interculturales en México y su modelo educativo, con base en ello se esboza una propuesta de currículum intercultural para las instituciones de educación superior que responda a los contextos sociales y culturales de donde estas se encuentren. Finalmente, se plantea que la educación debe responder a las necesidades y demandas sociales de los distintos grupos culturales