Comparative study of techniques used in the generation expansion planning

At the present time the generation expansion planning (GEP) has become a problem very difficult to solve for multiple reasons: many objectives, high uncertainties, very great planning horizon, etc. Its resolution by means of the exact traditional techniques, in numerous occasions, is not viable by the excessive time that is needed. For that reason, technical modern that allow the resolution in smaller time and with smaller accuracy in the solution are applied. Most of the approximate techniques are included inside a wider concept that is denominated Artificial Intelligence. In this article the more promising techniques of IA are studied indicating their applications in the PEG as well as their advantages and disadvantages

A comparison of transformer HF models and their application to PQ analysis

This research work is devoted to the comparison of some proposed high-frequency (HF) models of transformers and their application to power quality (PQ) studies. The models are classified according their structure, physical description and experimental methodology and set-up facilities needed to obtain the parameters

Supply security and the reliability of the spanish generator system in the next two decades based on the costs of fossil fuels and nuclear option

The supply security of the primary energy sources (coal, natural gas, enriched uranium...) and the reliability of the system in terms of the oscillations of the frequency and voltage are two aspects to assess in the Generation Expansion Planning. In this article, for the first criterion, the evolution of vulnerability and degree of independence of the generator system with respect to primary energy sources has been assessed by the indexes of Shannon-Weiner and energy independence, respectively. For the second approach, the evolution of the reserve margin by means the coverage index and the progression of the inertia and regulation capacity by means of its percentage regarding the total installed capacity. These four indexes have been applied on the obtained results of a stochastic lineal model developed with the software GAMS. In this model the nuclear technology has been considered as generation option in several scenarios of costs of the fossil fuels, coal and natural gas. Also, two of clean coal technologies with greater possibility of putting into service have been taken into account. The final conclusion would be that each technology carries out several functions in the generator system but not all them. That is, a generator system should have the greatest possible number of types of generation to be reliable and have supply security

Propagation of voltage sags in industrial power networks

The paper analyzes the propagation of voltage sags through the distribution network of an industrial company. For this, power quality is monitoring in high voltage, 44kV, and low voltage, 400V. The theory of M. Bollen is used for the study of the sags recorded by the meters at different points of the installation. It is necessary to know the connection of transformers in order to determine the transmission of the sags.The authors would like to thank the support of the Spanish Government under the research project ENE2007-68032-C04-04/CON

Internalisation of externalities in the spanish power generation sector. Impact of the national plan of allocation of emissions in the cost of generation

The electric generation produces damages (externalities or environmental costs) that are not contemplated in the costs of this activity. A way to include these damages in the cost is based on the emission rights. In these instruments the total amount of allowed contamination is fixed. It is assigned to the polluting agents by means of emission permissions, creating a market of these, in which the agents can exchange them based on their interests. In 2005, Spain undertook the National Plan of Allocation of Emission Rights 2005-2007 (PNA 2005-2007). This plan has established an emission limit to the electrical sector and it has been translated in the allocation of emission rights. If this emissions limit is surpassed they must acquire rights that cover the exceeded. Thus, the companies must reduce their emissions without increasing their costs. What mix of generation is have to be implement in order to minimize the emissions, avoiding to charge the emission rights in the total generation cost?. If it is impossible to cover the demand without this extra cost, how to diminish it? These questions can be responded using optimization methods

Implementation of a voltage sag characterization based on a DSP platform

Voltage sags are nowadays the first power quality problem in the distribution power system. This work evaluates the real implementation of a voltage sag characterization based on a DSP platform. Several classification methods for voltage sags have been presented in the literature. Here the Bollen’s classification is tested. Automation of sag assessment is desirable because manual analysis may be quite difficult. Thus, the fuzzy logic technique is chosen for this aim. This logic system generalizes the classical two-valued logic for reasoning under uncertainty. The fuzzy algorithm was first tested by simulation and then it was translated into C code in order to be implemented in a DSP based measurement platform, obtaining a satisfactory result.The authors would like to thank the support of the Spanish Government under the CICYT research project DPI2002-04416-C04-01

Mecanismos de relajación inducidos por el flavonoide ayanina en la aorta de ratas Wistar

[EN] Introduction: This study shows the relaxant effect induced by ayanin in aorta rings from Wistar rats linked to nitric oxide/ cyclic-GMP pathway. This flavonoid is the prevalent compound obtained from Croton schiedeanus Schlecht (Euphorbiaceae), specie used in Colombian folk medicine for the treatment of arterial hypertension. Objectives: To identify possible action mechanisms of vascular relaxation induced by ayanin (quercetin 3,4',7-trimethyl ether). Methodology: Isolated aorta rings from Wistar rats obtained at the Animal House of the University of Salamanca were contracted with KCl (80 mM) or phenylephrine (PE, 10-6 M) and exposed to ayanin (10-6-10-4 M). Then, the effect of ayanin was assessed in deendothelized rings contracted with PE and in intact rings contracted with PE previously incubated with: ODQ (10-6 M), L-NAME (10-4 M), L-NAME plus D- and L-arginine (10-4 M), indomethacin (5x10-6 M), dipyridamole (3x10-7 M), glibenclamide (10-6 M), propranolol (10-6 M), verapamil (10-7 M) or atropine (3x10-5 M). In addition, the relaxant effect of acetylcholine (Ach, 10-8-3x10-4 M), and sodium nitroprusside (SNP, 10-9-3x10-5 M) was assessed in the presence and absence of ayanin (10-6 M). Results: Ayanin induced a greater concentration-dependent relaxation in vessels contracted with phenylephrine (pEC50: 5.84±0.05), an effect significantly reduced by deendothelization and by both ODQ and L-NAME. L-arginine was able to reverse the effect of L-NAME. Indomethacin weakly inhibited ayanin response. Dipyridamole, glibenclamide, propranolol, verapamil, and atropine did not affect ayanin relaxation. Ayanin did not have any effect on the relaxation elicited by acetylcholine (ACh), while weakly decreasing the relaxation induced by sodium nitroprusside (SNP). Conclusion: Ayanin induces endothelium-dependent relaxation in the rat aorta mainly related to nitric oxide/cGMP pathway, according to the response observed in the presence of L-NAME, L-arginine and ODQ.Introdución: Este estudio muestra el efecto vasodilatador inducido por ayanina en anillos de aorta de ratas Wistar vinculado con la vía óxido nítrico/GMP-cíclico. Este flavonoide es el compuesto mayoritario aislado de Croton schiedeanus Schlecht (Euphorbiaceae), especie utilizada en la medicina popular colombiana para el tratamiento de la hipertensión arterial. Objetivos: Identificar los posibles mecanismos vasodilatadores inducidos por la ayanina (quercetin 3,4',7-trimetileter). Metodología: Se adicionó ayanina (10-6 - 10-4 M) a anillos aislados de aorta procedentes de ratas Wistar contraídos con KCl (80 mM) o fenilefrina (10-6 M). Luego se evaluó el efecto de la ayanina en anillos sin endotelio contraídos con fenilefrina y en anillos íntegros, contraídos con fenilefrina, previamente incubados con: ODQ (10-6 M), L-NAME (10-4 M), L-NAME más L- o D-arginina (10-4 M), indometacina (5x10-6 M), dipiridamol (3x10-7 M), glibenclamida (10-6 M), propranolol (10-6 M), verapamilo (10-7 M) o atropina (3x10-5 M). Además se examinó la relajación inducida por acetilcolina (Ach, 10-8-3x10-4 M) y nitroprusiato de sodio (SNP, 10-9-3x10-5 M) en presencia y ausencia de ayanina (10-6 M). Resultados: La ayanina produjo una mayor relajación en los anillos contraídos con fenilefrina (pEC50: 5.84±0.05), efecto que se redujo en anillos sin endotelio o en anillos íntegros preincubados con ODQ y L-NAME. L-arginina fue capaz de revertir la respuesta inducida por L-NAME. La indometacina inhibió discretamente la relajación generada por la ayanina. El dipyridamol, la glibenclamida, el propranolol, el verapamilo y la atropina no modificaron el efecto de la ayanina. La ayanina no afectó la relajación inducida por la acetilcolina y débilmente disminuyó la inducida por el nitroprusiato de sodio. Conclusión: La ayanina induce una relajación dependiente del endotelio en la aorta de rata, efecto vinculado principalmente con la vía de óxido nítrico/GMP cíclico, de acuerdo con la respuesta observada en presencia de LNAME, ODQ y L-arginina

Índices de biodiversidad aplicados al análisis de la seguridad de suministro en sistemas de potencia

ABSTRACT: The evolution of the vulnerability of the Spanish power generation system with respect to the primary energy resources has been assessed by three new indexes developed from biodiversity analysis. The first of these indexes measures, in percentage, the uniformity of the primary energy resources in the system. The second one quantifies the diversity by means of the equivalent number of primary energy resources that are present in similar proportions in the system. The third one allows the calculation of the diversity reduction in the system with the non-evenness of these primary energy resources. They have been applied to the energy results of a stochastic linear model, developed with the software GAMS, in order to demonstrate their usefulness. In this model several generation technologies have been considered (nuclear, clean coal technologies, etc), and also several scenarios of fossil fuel costs. The number of primary energy resources that have to be used depends on the degree of uniformity of the system and on their influence on diversity. In the Spanish case, if nuclear generation is not considered as an energy source, the diversity of the system will diminish significantly in the future, making the system more vulnerable.RESUMEN: La evolución de la vulnerabilidad del sistema de generación de potencia en España, con respecto a los recursos primarios de energía, ha sido evaluada por medio de tres nuevos índices desarrollados a partir del análisis de la biodiversidad. El primero de estos índices mide, en porcentaje, la uniformidad de los recursos primarios en el sistema. El segundo cuantifica la diversidad por medio del número equivalente de recursos primarios que se encuentran en proporciones similares en el sistema. El tercero permite el cálculo de la reducción de la diversidad en el sistema con la desigualdad de esas fuentes primarias de energía. Los índices han sido aplicados a los resultados de un modelo estocástico lineal desarrollado con el logicial GAMS, a fin de demostrar su utilidad. En este modelo se han considerado varias tecnologías de generación (nuclear, tecnologías limpias de carbón, etc.), así como también varios escenarios de costos de combustibles fósiles. El número de recursos energéticos primarios que deben ser utilizados depende del grado de uniformidad del sistema y de sus influencias en la diversidad. En el caso español, si la generación nuclear no es considerada como una fuente de energía, la diversidad del sistema disminuirá significativamente en el futuro, haciendo más vulnerable al sistema

Artificial neural networks approach to the voltage sag classification

The authors would like to thank the support of the Spanish Government under the CICYT research project DPI2002-04416-C04-01

The role of the dc-bus in voltage sags experienced by three-phase adjustable-speed drives

This research work is devoted to the critical evaluation of the role of the dc-bus in the behavior of threephase adjustable-speed drives with voltage sags. In particular, the dc-link voltage variation under voltage sag and its dependence on bus capacity, dc-link resistance and inductance and source impedance. The analysis can be used to introduce additional capacitance in the dc-link in order to increase the ride-through capability of the ASD. Both an electromagnetic transient model and a set-up facility have been introduced. This test platform can be used in order to study the sensitivity of ASD to different disturbances.The authors would like to thank the support of the Spanish Government under the research project ENE2007-68032-C04-04/CON