Combined hydro-wind generation bids in a pool-based electricity market

Present regulatory trends are promoting the irect participation of wind energy in electricity markets. The final result of these markets sets the production scheduling for the operation time, including a power commitment from the wind generators. However, wind resources are uncertain, and the final power delivered usually differs from the initial power committed. This imbalance produces an overcost in the system, which must be paid by those who produce it, e.g., wind generators among others. As a result, wind farm revenue decreases, but it could increase by allowing wind farms to submit their bids to the markets together with a hydro generating unit, which may easily modify its production according to the expected imbalance. This paper presents a stochastic optimization technique that maximizes the joint profit of hydro and wind generators in a pool-based electricity market, taking into account the uncertainty of wind power prediction.En prens

Optimal security-constrained power scheduling by Benders decomposition

This paper presents a Benders decomposition approach to determine the optimal day-ahead power scheduling in a pool-organized power system, taking into account dispatch, network and security constraints. The study model considers the daily market and the technical constraints resolution as two different and consecutive processes. The daily market is solved in a first stage subject to economical criteria exclusively and then, the constraints solution algorithm is applied to this initial dispatch through the redispatching method. The Benders partitioning algorithm is applied to this constraints solution process to obtain an optimal secure power scheduling. The constraints solution includes a full AC network and security model to incorporate voltages magnitudes as they are a critical factor in some real power systems. The algorithm determines the active power committed to each generator so as to minimize the energy redispatch cost subject to dispatch, network and security constraints. The solution also provides the reactive power output of the generators, the value of the transformers taps and the committed voltage control devices. The model has been tested in the IEEE 24-bus Reliability Test System and in an adapted IEEE 118-bus Test System. It is programmed in GAMS mathematical modeling language. Some relevant results are reported.Publicad

Aerodynamic Optimization of High-Speed Trains Nose using a Genetic Algorithm and Artificial Neural Network

An aerodynamic optimization of the train aerodynamic characteristics in term of front wind action sensitivity is carried out in this paper. In particular, a genetic algorithm (GA) is used to perform a shape optimization study of a high-speed train nose. The nose is parametrically defined via Bézier Curves, including a wider range of geometries in the design space as possible optimal solutions. Using a GA, the main disadvantage to deal with is the large number of evaluations need before finding such optimal. Here it is proposed the use of metamodels to replace Navier-Stokes solver. Among all the posibilities, Rsponse Surface Models and Artificial Neural Networks (ANN) are considered. Best results of prediction and generalization are obtained with ANN and those are applied in GA code. The paper shows the feasibility of using GA in combination with ANN for this problem, and solutions achieved are included

Análisis intergubernamental del proyecto de Plan Hidrológico Nacional de España

Se aplica el análisis intergubernamental al proyecto de Plan Hidrológico Nacional de España, poniendo de manifiesto aspectos normativos, los actores intervinientes y sus diferentes racionalidades

Resolución de restricciones técnicas en la programación diaria de la generación mediante descomposición de Benders

En esta tesis se aborda el problema de la programación de la generación de energía eléctrica a corto plazo con restricciones de seguridad. La programación segura de la generación engloba dos problemas clásicos en la explotación de los sistemas eléctricos: la asignación horaria de la generación y el flujo de cargas óptimo con restricciones de seguridad. El objetivo de la tesis será definir en un entorno competitivo la asignación horaria de la generación teniendo en cuenta tanto las restricciones de despacho (límites de producción de potencia activa y reactiva de los grupos generadores, reserva rodante del sistema, límites de rampa) como las restricciones de red y de seguridad del sistema (ecuaciones completas de nudo de potencia activa y reactiva, límites de tensión en los nudos y límites de capacidad de las líneas, en el estado normal y en los distintos estados post-contingencia). En este trabajo la programación de la generación se formula como un problema matemático complejo que consta de: -función objetivo lineal a tramos basada en precios de oferta, -variables de decisión binarias (1/0): conexión o desconexión de grupos de generación,reactancias o condensadores en cada periodo de programación,variables continuas de operación: potencia activa y reactiva, tensión y ángulo de nudo,tomas de transformadores,. . . -acoplamientos temporales: gradiente de carga y la condición compleja de ingresos mínimos establecida en las reglas del mercado eléctrico español, -restricciones no-lineales: ecuaciones completas de nudo de potencia activa y reactiva y límites de capacidad de las líneas tanto en el estado normal como en los distintos estadospost-contingencia 'n-1'. La dificultad matemática que conlleva la presencia de variables binarias en un modelo no-lineal se resuelve mediante el uso de la Descomposición Generalizada de Benders. El acoplamiento temporal de la solución se reordena de forma que pueda ser tratado de forma óptima por el algoritmo de Benders. La tesis aplica el método basado en la Descomposición Generalizada de Benders a dos modelos diferentes. El Modelo Operador Único considera el mercado diario y el proceso de solución de restricciones técnicas como una única etapa. Por el contrario, el modelo de estudio OM-OS está basado en las reglas del mercado eléctrico español y resuelve el problema en dos etapas: la primera facilita la solución del mercado diario de casación bajo criterios exclusivamente económicos y la segunda, partiendo de la casación del mercado diario, resuelve el problema de las restricciones técnicas mediante el redespacho de la programación inicial. Ambos modelos determinan la producción de potencia activa y reactiva de las unidades de generación, el valor de las tomas de los transformadores, así como los dispositivos de control de tensión acoplados necesarios para minimizar el coste de producción del sistema sujeto a restricciones de despacho, de red y de seguridad. Los modelos han sido ensayados para diferentes casos del sistema IEEE de 24 nudos y de un sistema adaptado del IEEE de 118 nudos. Finalmente, en la tesis se desarrolla un procedimiento novedoso basado en la descomposición de Benders para ser aplicado a sistemas de potencia de gran dimensión. El método organiza el algoritmo de descomposición en tres niveles y resuelve eficazmente la programación de la generación con restricciones de seguridad. El primer nivel determina, exclusivamente, el acoplamiento (0/1) de las unidades de generación, reactancias y condensadores, el segundo nivel fija el valor de las variables de control del problema (potencia activa de los generadores, tensión de consigna de los generadores y tomas de los transformadores) y por último, el tercer nivel define el valor de las variables de estado para los estados normal y post-contingencia. El método se aplica al sistema peninsular español. Los modelos son programados en GAMS, lenguaje de programación y modelización de sistemas físicos. Se utilizan los optimizadores CONOPT y CPLEX para los problemas de programación no lineal y lineal entero-mixto, respectivamente.______________________________________________ In this thesis the short-term optimization of power production with security constraints is treated. The secure power scheduling involves two classical problems in the electric systems operation: the unit commitment and the security-constrained optimal power _ow. The objective of the thesis is the determination of the daily unit commitment in a competitive environment taking into account dispatch constraints (power reserve, ramp rate limits, real and reactive power output limits) as well as network and security constraints (bus voltages and transmission _ow limits in pre and post contingency states). In this work, power scheduling is posed as a complex mathematical problem which includes: linear objective function based on prices,binary decision variables: o_-line or on-line generating units, reactances or capacitorsduring period t,continuous variables for the operation processes: real and reactive power, bus voltage andbus angle, transformers taps,. . .time couplings: ramp rate limits and minimum incomes condition established in the Spanish electric market, non-linear constraints: complete load _ow equations and transmission capacity limits of lines in normal and post-contingency 'n-1' states. The mathematical di_culty due to the presence of binary variables in a non-linear model is solved using the Generalized Benders Decomposition. The time coupling is arranged so that it can be treated in a optimal way by the Benders algorithm. The thesis applies the Generalized Benders Decomposition approach to two di_erent models. The 'Unique Operator' Model considers the daily market and the technical constraints resolution process as a single one. On the contrary, the Model OM-OS is based on the Spanish electric market and deals with the problem in two stages, the _rst stage solves the daily market with economical criteria exclusively and the second stage applied the constraints solution algorithm to this initial dispatch. Both models determine the active and reactive power output of each generation unit, the transformer taps and the committed voltage control devices so as to minimize the total generation cost subject to dispatch, network and security constraints. The models have been tested in di_erent cases of the IEEE 24-bus Reliability Test System and an adapted IEEE 118-bus Test System. Finally, the thesis develops a novel procedure based on the Benders Decomposition to be applied to large-scale electric power systems. The method organizes the decomposition in three di_erent levels and allows to solve e_ciently the power scheduling with security constraints in large scale systems. The _rst level decides exclusively the commitment (0/1) of the generating units, reactances and capacitors, the second level _xes the control variables of the problem (generator real power, generator voltage magnitude and transformer taps) and last, the third level determines the values of the state variables for the normal and 'n-1' states. The method is applied to the Spanish Peninsular system. The models are programmed in GAMS mathematical modelling language, using CONOPT and CPLEX solvers for non-linear and linear mixed-integer programming problems, respectively

Increasing Wild Boar Density Explains the Decline of a Montagu’s Harrier Population on a Protected Coastal Wetland

[Abstract] We studied the rapid decline in the number of breeding pairs (geometric growth rate λ = 0.86; 14 % annual decrease) of a semi–colonial ground–nesting bird of prey, the Montagu's harrier (Circus pygargus), after twelve years of rapid population growth (λ = 1.15; 15 % rate of annual increase) in a protected coastal wetland in Eastern Spain. The study was conducted from 1992–2017, and the range of values in population size was: 2–37 breeding pairs. We contrasted 20 biologically–sound hypotheses (including local and regional factors) to explain the trend over time in the annual number of pairs. The most parsimonious model included a surrogate of wild boar (Sus scrofa) density in the region during the previous year and the annual number of Montagu's harrier pairs breeding inland in the study province during the focal year. Syntopic western marsh harriers (C. aeruginosus) were not found to have any effect on the numbers of Montagu's harriers either in our modelling or when we performed a quantitative and qualitative study both for years t and t–1. Our final 'best' models did not include spring rainfall, regional forest fires or local land use changes. The impact of wild boars on breeding success, together with conspecific attraction, could have resulted in the dispersal of coastal wetland birds to larger populations in dense inland shrub lands where levels of wild boar nest predation were more likely lower.[Resumen] Hemos estudiado el rápido descenso del número de parejas reproductoras (tasa de crecimiento geométrico λ = 0,86; 14 % de disminución anual) de un ave semicolonial que nidifica en el suelo, el aguilucho cenizo (Circus pygargus), tras 12 años de rápido crecimiento demográfico (λ = 1,15; 15 % de tasa de aumento anual) en un humedal costero protegido situado en el este de España. El periodo de estudio fue 1992–2017, con un intervalo de valores del tamaño de población de 2–37 parejas reproductoras. Hemos contrastado 20 hipótesis razonables desde el punto de vista biológico (teniendo en cuenta factores locales y regionales) para explicar la tendencia del número anual de parejas. El modelo más parsimonioso incluyó un indicador de la densidad regional del jabalí (Sus scrofa) durante el año anterior y el número anual de parejas de aguilucho cenizo que se reprodujeron en el interior de la provincia del estudio, durante el año en cuestión. En nuestro modelo no se observó que el aguilucho lagunero occidental (C. aeruginosus) sintópico tuviera efecto alguno en el número de aguiluchos cenizos; tampoco lo tuvo en los análisis cuantitativos y cualitativos relativos a los años t y t–1. Las precipitaciones de primavera, los incendios forestales en la región y los cambios en el uso del suelo a escala local tampoco aparecieron en nuestros mejores modelos finales. Los efectos de jabalíes en el éxito reproductor, junto con la atracción de individuos conespecíficos, podrían haber provocado la dispersión de las aves de los humedales costeros a poblaciones más numerosas presentes en zonas arbustivas de interior, donde probablemente la depredación de nidos por jabalí sea inferior.Xunta de Galicia; GRC2014/050Xunta de Galicia; ED431C 2018/5

Aerodynamic Optimization of a High-speed Train using Genetic Algorithms

Genetic algorithms (GA) have been used for the minimization of the aerodynamic drag of a train subject to front wind. The significant importance of the external aerodynamic drag on the total resistance a train experiments as the cruise speed is increased highlights the interest of this study. A complete description of the methodology required for this optimization method is introduced here, where the parameterization of the geometry to be optimized and the metamodel used to speed up the optimization process are detailed. A reduction of about a 25% of the initial aerodynamic drag is obtained in this study, what confirms GA as a proper method for this optimization problem. The evolution of the nose shape is consistent with the literature. The advantage of using metamodels is stressed thanks to the information of the whole design space extracted from it. The influence of each design variable on the objective function is analyzed by means of an ANOVA test

Multi-objective Aerodynamic Optimization of High-speed Trains in Tunnels

A genetic algorithm (GA) is employed for the multi-objective shape optimization of the nose of a high-speed train. Aerodynamic problems observed at high speeds become still more relevant when traveling along a tunnel. The objective is to minimize both the aerodynamic drag and the amplitude of the pressure gradient of the compression wave when a train enters a tunnel. The main drawback of GA is the large number of evaluations need in the optimization process. Metamodels-based optimization is considered to overcome such problem. As a result, an explicit relationship between pressure gradient and geometrical parameters is obtained

Surrogate-based optimization of the nose shape of a train subjected to crosswind

Optimización multi-objetivo frente a varias direcciones del viento incidente del testero de un tren de alta velocida

Genetically aerodynamic optimization of the nose shape of a high-speed train entering a tunnel

The optimization of the nose shape of a high-speed train entering a tunnel has been performed using genetic algorithms(GA).This optimization method requires the parameterization of each optimal candidate as a design vector.The geometrical parameterization of the nose has been defined using three design variables that include the most characteristic geometrical factors affecting the compression wave generated at the entry of the train and the aerodynamic drag of the train