Optimal Power Dispatch of Dispersed Sources in Direct-Current Networks with Nonlinear Loads

The problem of the optimal power dispatch of dispersed generators in direct-current networks under the presence of nonlinear loads (constant power terminals) is addressed through a combinatorial optimization strategy by using a master-slave solution methodology. The optimal power generation in the dispersed is solved in the master optimization stage through the application of the vortex-search algorithm. Each combination of the power outputs at the dispersed generation sources is provided to a power flow methodology known as the hyperbolic power flow approach for direct current networks. The main advantage of the proposed optimization method corresponds to the possibility of solving a complex nonlinear programming problem via sequential quadratic programming, which can be easily implemented at any programming language with low computational effort and high-quality results. The computational tests of the master-slave optimization proposal are evaluated in a 21-bus system, and the numerical results are compared with the implementation of the exact nonlinear programming model in the General Algebraic Modeling System (i.e., GAMS). All the computational results are conducted through the MATLAB programming environment licensed by Universidad Tecnologica de Pereira for academic usag

CLASIFICADORESINTELIGENTESPARA DETERMINAR LA AFECTACIÓN A LA CALIDAD DE LA ENERGÍA ELÉCTRICA

En el presente trabajo se presenta el modelado matemático y la simulación de algunos de los fenómenos que afectan la calidad de la energía, para posteriormente aplicárseles la Transformada Discreta de Wavelet y así obtener la distribución de energía de los 10 primeros coeficientes de detalle de tal forma que al hacer un procesamiento de estos datos se obtengan patrones característicos de cada señal. Con estospatrones entrenan variosclasificadores inteligentes y poder determinar cuál de estos presenta mejor resultados en cuanto a la predicción de la clase a la que pertenece cada uno de los patrones mencionados. Por otra parte,teniendo calculadas las distribuciones de energía de los coeficientes de detalle se procede a la formulación de un indicador general de calidad de la energía y compararlo con los índices existentes

A quadratic convex approximation for optimal operation of battery energy storage systems in DC distribution networks

This paper proposes a quadratic convex model for optimal operation of battery energy storage systems in a direct current (DC) network that approximates the original nonlinear non-convex one. The proposed quadratic convex model uses Taylor’s series expansion to transform the product between voltage variables in the power balance equations into a linear combination of them. Numerical simulations in the general algebraic modeling system (GAMS) for both models show small diferences in the daily energy losses, which are lower than 3.00%. The main advantage of the proposed quadratic model is that its optimal solution is achievable with interior point methods guaranteeing its uniqueness (convexity properties of the solution space and objective function), which is not possible to guarantee with the exact nonlinear non-convex model. The 30-bus DC test feeder with four distributed generators (with power generation forecast via artifcial neural networks with errors lower than 1% between real and predicted generation curves) and three batteries is used to validate the proposed convex and exact models. Numerical results obtained by GAMS show the efectiveness of the proposed quadratic convex model for diferent simulation scenarios tested, which was confrmed by the CVX tool for convex optimization in MATLA

Aplicación de la cadena de Markov a transformadores de tensión y pararrayos ubicados en las subestaciones de interconexión eléctrica S.A. E.S.P.- ISA -

La técnica de Markov es una de las técnicas más utilizadas para realizar análisis de confiabilidad, disponibilidad, mantenibilidad y seguridad de sistemas o partes de estos, donde las fallas dependen de eventos secuenciales o para los cuales las estrategias de mantenimiento son complejas. Para seleccionar la estrategia de mantenimiento adecuada es necesario conocer el ciclo de vida del equipo, es decir, realizar un análisis por medio de métodos estadísticos que permitan modelar el equipo en estados de deterioro y calcular tasas de fallas y reparación, como lo hace el modelo de Markov. En este trabajo se presenta la aplicación del modelo de Markov para transformadores de tensión y para pararrayos de una empresa del Sector Eléctrico Colombiano utilizando la metodología propuesta en la norma internacional IEC 61165:2006 – Application of Markov Techniques, dicho modelo incluye las condiciones de operación de los equipos mencionados, modos de falla y actividades de mantenimiento. La información necesaria para la realización del trabajo se encuentra en una base de datos con registros desde 1998 hasta el 2008 de los equipos en los que se encuentran reportes sobre actividades de mantenimiento, registro de fallas, ubicación del equipo, edad, entre otros; además se contó con la asesoría de expertos en mantenimiento de ambos equipos, de tal forma que el modelo desarrollado refleja el comportamiento esperado

Assembling the Dead, Gathering the Living: Radiocarbon Dating and Bayesian Modelling for Copper Age Valencina de la Concepción (Seville, Spain)

The great site of Valencina de la Concepción, near Seville in the lower Guadalquivir valley of southwest Spain, is presented in the context of debate about the nature of Copper Age society in southern Iberia as a whole. Many aspects of the layout, use, character and development of Valencina remain unclear, just as there are major unresolved questions about the kind of society represented there and in southern Iberia, from the late fourth to the late third millennium cal BC. This paper discusses 178 radiocarbon dates, from 17 excavated sectors within the c. 450 ha site, making it the best dated in later Iberian prehistory as a whole. Dates are modelled in a Bayesian statistical framework. The resulting formal date estimates provide the basis for both a new epistemological approach to the site and a much more detailed narrative of its development than previously available. Beginning in the 32nd century cal BC, a long-lasting tradition of simple, mainly collective and often successive burial was established at the site. Mud-vaulted tholoi appear to belong to the 29th or 28th centuries cal BC; large stone-vaulted tholoi such as La Pastora appear to date later in the sequence. There is plenty of evidence for a wide range of other activity, but no clear sign of permanent, large-scale residence or public buildings or spaces. Results in general support a model of increasingly competitive but ultimately unstable social relations, through various phases of emergence, social competition, display and hierarchisation, and eventual decline, over a period of c. 900 years