Control de frecuencia en parques eólicos.

[ES]de generación convencional basada en grandes centrales de generación térmica por lo que es necesaria la contribución de este tipo de generación en el mantenimiento de las magnitudes básicas del sistema. El objetivo del T.F.G, será analizar el impacto de la generación eólica en la frecuencia del sistema, así como las diferentes propuestas para que este tipo de generación participe en el control de frecuencia. En primer lugar se describen los aspectos técnicos de la generación eólica. A continuación se analiza el control de frecuencia y se examinan diferentes mecanismos de contribución de la generación eólica al control de frecuencia. Finalmente se realizará un ejemplo práctico mediante el programa de simulación Matlab/Simulink con objeto de analizar de forma simplificada el comportamiento de control de frecuencia en sistemas eléctricos con generación eólica.

Aquellos que allí se parecen no son gigantes, sino molinos de viento

Nivel educativo: Grado. Duración (en horas): De 21 a 30 horas

Acordo Aeroespacial Teuto-Brasileiro (1969-1989; 1990-2001 e 2002-2011): uma cooperação complementar

Este projeto de dissertação se propõe a analisar a cooperação aeroespacial entre o Brasil e a Alemanha de 1969 a 2011 em três recortes temporais: 1969 a 1989, 1990 a 2001 e 2002 a 2011. Seguindo as bases teóricas de classificação da CID (Cooperação Internacional para o Desenvolvimento), e apoiada em pesquisa de campo conduzida em ambos os países, este trabalho apresenta um novo conceito de cooperação que, até onde a pesquisa bibliográfica aqui conduzida avaliou, constitui uma contribuição original deste trabalho: a Cooperação Complementar. A cooperação aeroespacial teuto-brasileira é pouco conhecida e divulgada, embora tenha completado vigorosas quatro décadas de exitosa existência. A conclusão de êxito desta cooperação encontrou lastro em pesquisa de campo conduzida pela autora no Brasil (IAE Instituto de Aeronáutica e Espaço) e na Alemanha (DLR Deutsche Zentrum für Luft- und Raumfahrt), consubstanciada por quatro entrevistas (SILVA, 2011a), (SILVA, 2011c), (SILVA, 2011d) e (SILVA, 2011e) realizadas junto a importantes representantes destes dois centros. Os conhecimentos extraídos por meio destas entrevistas agregaram, no entender desta autora, importantes informações à bibliografia específica e relativamente escassa disponível em ambos os países.O êxito defendido nesta dissertação fundamenta-se não apenas na longevidade advinda dos 40 anos de existência desta Cooperação, na sua capacidade de renovação e na complementaridade atingida, mas sobretudo pela consecução dos diversos objetivos técnico-científicos integrantes do escopo do referido Tratado, muitos dos quais responsáveis por importantes desdobramentos de tecnologias em outras áreas do saber, tais como o projeto DEBRA 25 (SCHUSTER, 2011), de energia eólica, e o projeto VLS (Veículo Lançador de Satélites), que utiliza como seus motores os foguetes desenvolvidos no escopo desta Cooperação.

Investigation into IGBT dV/dt during turn-off and its temperature dependence

In many power converter applications, particularly those with high variable loads, such as traction and wind power, condition monitoring of the power semiconductor devices in the converter is considered desirable. Monitoring the device junction temperature in such converters is an essential part of this process. In this paper, a method for measuring the insulated gate bipolar transistor (IGBT) junction temperature using the collector voltage dV/dt at turn-OFF is outlined. A theoretical closed-form expression for the dV/dt at turn-OFF is derived, closely agreeing with experimental measurements. The role of dV/dt in dynamic avalanche in high-voltage IGBTs is also discussed. Finally, the implications of the temperature dependence of the dV/dt are discussed, including implementation of such a temperature measurement technique. © 2006 IEEE.

National report of the frame survey 2012 on the Uganda side of Lake Victoria

This is a report on the results of the Frame Survey conducted in the Uganda side of Lake Victoria during August 2012 by the LVFO Institutions, namely: the Department of Fisheries Resources (DFR) Uganda and the National Fisheries Resources Research Institute (NaFIRRI) in close collaboration with the District Fisheries offices of Busia, Bugiri, Namayingo, Mayuge, Jinja, Buvuma, Buikwe, Mukono, Kampala, Wakiso, Mpigi, Kalungu, Masaka, Kalangala and Rakai. In the 2012 Frame survey some indicators of fishing effort including e.g. number of fishers, fishing crafts and long line hooks increased; whereas others like the number of gillnets less than 5 inches decreased by 10.4% from that recorded in 2010. The other indicators of fishing effort, which showed decrease in 2012 included illegal beach seines and undersized gillnets (<5 inch mesh size). However, a large proportion (66%) of long line hooks recorded in the 2012 survey were in the smallest size range (hook size >10), which target small Nile perch. The number of other illegal gears, i.e. cast nets and monofilament gillnets showed modest increases (25%) between 2010 and 2012 while beach seines decrease by 15%. Recent crackdown on illegal fishing activities as part of measures for recovery of the Nile perch stocks which are faced with depletion appear to have had an impact but much more needs to be done to eradicate illegal fishing. The fisheries in the Ugandan waters have remained predominantly near shore with 61% of all fishing crafts using paddles out of which 17% were tiny three plank, flat bottomed boats locally known as parachutes. The 2012 survey shows an increase in the number of fishing crafts using sails by 65% from 682 in 2010 to 1125 in 2012. This is an encouraging trend as more fishers are able to access distant fishing grounds using free wind power. The Mukene fishery in the Ugandan waters of Lake Victoria remained underdeveloped comprising only 15.2% of all fishing crafts, of which 31% were motorised which is a great improvement from the situation recorded in 2010. The Catamarans increased to 18 with a majority in Buikwe district where there is a private investor fishing specifically for Mukene. The Catamarans in Kalangala were reported not to be working because of the high operating cost compared to ordinary Mukene fishing boats.

Dynamic analysis of the brushless doubly-fed induction generator during symmetrical three-phase voltage dips

The Brushless Doubly-Fed Induction Generator (BDFIG) shows commercial promise as replacement for doublyfed slip-ring generators for wind power applications by offering reduced capital and operational costs due to its brushless operation. In order to facilitate its commercial deployment, the capabilities of the BDFIG system to comply with grid code requirements have to be assessed. This paper, for the first time, studies the performance of the BDFIG under grid fault ride-through and presents the dynamic behaviour of the machine during three-phase symmetrical voltage dips. Both full and partial voltage dips are studied using a vector model. Simulation and experimental results are provided for a 180 frame BDFIG.

A novel vector control approach for Single Phase Brushless Doubly Fed Machine

This paper proposed a novel control scheme for operating the Single Phase Brushless Doubly-Fed Machine (SPB) based on Stator-Flux-Oriented control algorithm. The SPB is a new type of Brushless Doubly-Fed Machine (BDFM) which shows a potential in applications which require adjustable speed such as Wind Power generation and speed adjustable Drive. The SPB can be applied to single-phase power system and the lower cost of the SPB makes the SPB suitable for low-rated power conversion applications. This paper develops the control scheme of the SPB with explicit mathematical analysis and block diagram of the controller. Experimental verification is also given. © 2011 IEEE.

Symmetrical low voltage ride-through of the Brushless Doubly-Fed Induction Generator

The Brushless Doubly-Fed Induction Generator (BDFIG) shows commercial promise for wind power generation due to its lower cost and higher reliability compared to the Doubly-Fed Induction Generator (DFIG). For the purposes of commercialisation, the BDFIG must meet grid codes at all times. Nowadays, all new wind generators have to ride through certain grid faults, and the Low-Voltage Ride Through (LVRT) capability has become one of the most important points on which to assess the performance a generator. This paper, for the first time, proposes a control scheme to enable the the BDFIG to ride through symmetrical voltage dips. Simulation results and experimental results on a prototype BDFIG show that the proposed scheme gives the capability to ride through low voltage faults. © 2011 IEEE.

Symmetrical low voltage ride-through of a 250 kW Brushless DFIG

The Brushless Doubly-Fed Induction Generator (Brushless DFIG) shows commercial promise for wind power generation due to its lower cost and higher reliability when compared with the conventional Doubly-Fed Induction Generator (DFIG). In the most recent grid codes, wind generators are required to be able to ride through a low voltage fault and meet the reactive current demand from the grid. Hence, a Low-Voltage Ride-Through (LVRT) capability is important for wind generators which are integrated into the grid. In this paper the authors propose a control strategy enabling the Brushless DFIG to successfully ride through a symmetrical voltage dip. The control strategy has been implemented on a 250 kW Brushless DFIG and the experimental results indicate that LVRT is possible without a crowbar.

黄土高原水土流失治理进展及其对策

黄土高原地区水土流失类型复杂,既有自然因素和人为因素,也有水力、风力、重力产生的变化。同时气候干旱、水资源缺乏成为植物生长和生态环境改善的最大障碍。在国家实施西部大开发的进程中,良好的生态环境成为生存与发展和建设小康社会的标志。无论从西部大开发的战略角度考虑,还是从退耕还林(草)政策实施8年以后,如何解决黄土高原地区人民群众衣食住行、经济发展问题及黄河减沙的角度来看,采取有效措施,加快该区的生态建设已势在必行。根据第十一个五年规划的建议,以生态恢复学和土壤侵蚀学的基本原理为指导,分析了黄土高原地区的重要性,探讨了黄土高原生态建设与经济发展的基本现状,因地制宜地提出了发展对策。

巴丹吉林沙漠近40a风沙活动规律浅析

Based on the data of wind from 11 meteorological observation stations in recent 40 years, the paper analyzed the temporal and spatial distribution characteristics of resultant drift potential in the Badain Jaran Desert. The 84 sand samples were collected and analysed from three compound crescentic dunes developped on southeast part of The Badain Jaran Desert. Through the statistics and computation of wind data and the analysis of Grain Size over compound crescentic dunes in The Badain Jaran Desert, this paper analyzed the characteristics of the blown sand activities in in this area. The following viewpoints were obtained: 1　Most parts of The Badain Jaran Desert are dominated by northwest wind and sub－dominated by west wind, while prevailing wind in southeast part of The Badain Jaran Desert is southeast, different froms other places. 2 The Badain Jaran Desert is strongly zoned from its surounding meteorological observation stations. It has impressively high DP and RDP value. Except for Ding Xin Station in medium wind power environment, the left stations are all belongs to high wind－power districts. 3 From the seventies till now, the value of DP and RDP in The Badain Jaran Desert shows a decending trend except for the RDP value of Guai Zihu Station in the north. This trend indicates that the wind power for the moment of The Badain Jaran Desert is far lower than it in the seventies. 4 Adopting sand rose map for classification of wind environments in defferent parts of The Badain Jaran Desert, Ejinaqi is Narrow unimodal wind regimes, Ding xin, Bayinmaodao and Ayouqi districts obtuse bimodal and Guaizihu complex. 5 Resultant drift directions in most parts of the Badain Jaran desert are southeast, which indicates annual net sand in these areas drifted from the northwest to the southeast of the desert, which consists with the analysis results of grain size of predecessors. RDD in Ayouqi staion shows the net sand drifted from the southeast to the northwest in the recent 40 years, which may attribute to the reason that, the Badain Jaran desert lies in the zone influenced by both northwest and southeast wind, the southeast monsoon was strengthened and northwest wind became weaker than a former time. So, if sand mareria is sufficient, there are two different drift directions, namely two sorts of sand source, existed in Badain Jaran desert at least. 6 Based on analysis results of meteorologic data and grain size, blown sand activities is that, in most parts of Badain Jaran desert in the past 40 years, northwest wind transported net sand from the northwest part to the southeast part of The Badain Jaran Desert.And besides this, analysis of collected sand samples also shows that, in the southeast part of Badain Jaran desert, grain size do fined from southeast to northwest. Combining results of meteorologic data in the southeast part, it can infered that southeast monsoon took blown sand to the inner desert from its southeast part.

A genetic algorithm based economic dispatch (GAED) with environmental constraint optimisation

The role of renewable energy in power systems is becoming more significant due to the increasing cost of fossil fuels and climate change concerns. However, the inclusion of Renewable Energy Generators (REG), such as wind power, has created additional problems for power system operators due to the variability and lower predictability of output of most REGs, with the Economic Dispatch (ED) problem being particularly difficult to resolve. In previous papers we had reported on the inclusion of wind power in the ED calculations. The simulation had been performed using a system model with wind power as an intermittent source, and the results of the simulation have been compared to that of the Direct Search Method (DSM) for similar cases. In this paper we report on our continuing investigations into using Genetic Algorithms (GA) for ED for an independent power system with a significant amount of wind energy in its generator portfolio. The results demonstrate, in line with previous reports in the literature, the effectiveness of GA when measured against a benchmark technique such as DSM.

Energia eólica

Actualmente, é indiscutível a importância das energias ditas renováveis no contexto da produção mundial de energia, destacando-se, dentro destas, a energia eólica pelas suas inúmeras vantagens. Neste artigo descrevem-se as vantagens e desvantagens deste tipo de energia e apresenta-se uma discussão da evolução da potência instalada de acordo com os dados fornecidos pelos organismos correspondentes. Pretende-se, além disso, explicar a evolução da potência instalada na Europa e, mais especificamente, no caso de Portugal, explicar a baixa potência instalada tendo em conta o elevado potencial eólico disponível. The importance of renewable energies in the context of the world energy production is nowadays unquestionable, namely in the case of the eolic energy, due to its specific advantages. In this paper, the advantages and disadvantages of this type of energy are described, and a discussion of the evolution of the wind power installed is presented according to the data published by the different organisms involved. It is intended to show and explain the evolution of the wind power capacity installed in the European Union. Finally, it is discussed the Portuguese specificity characterized by a low wind power installed despite the high eolic potential available.

Electrical machine characterisation and analysis for renewable energy applications

There has been an increased use of the Doubly-Fed Induction Machine (DFIM) in ac drive applications in recent times, particularly in the field of renewable energy systems and other high power variable-speed drives. The DFIM is widely regarded as the optimal generation system for both onshore and offshore wind turbines and has also been considered in wave power applications. Wind power generation is the most mature renewable technology. However, wave energy has attracted a large interest recently as the potential for power extraction is very significant. Various wave energy converter (WEC) technologies currently exist with the oscillating water column (OWC) type converter being one of the most advanced. There are fundemental differences in the power profile of the pneumatic power supplied by the OWC WEC and that of a wind turbine and this causes significant challenges in the selection and rating of electrical generators for the OWC devises. The thesis initially aims to provide an accurate per-phase equivalent circuit model of the DFIM by investigating various characterisation testing procedures. Novel testing methodologies based on the series-coupling tests is employed and is found to provide a more accurate representation of the DFIM than the standard IEEE testing methods because the series-coupling tests provide a direct method of determining the equivalent-circuit resistances and inductances of the machine. A second novel method known as the extended short-circuit test is also presented and investigated as an alternative characterisation method. Experimental results on a 1.1 kW DFIM and a 30 kW DFIM utilising the various characterisation procedures are presented in the thesis. The various test methods are analysed and validated through comparison of model predictions and torque-versus-speed curves for each induction machine. Sensitivity analysis is also used as a means of quantifying the effect of experimental error on the results taken from each of the testing procedures and is used to determine the suitability of the test procedures for characterising each of the devices. The series-coupling differential test is demonstrated to be the optimum test. The research then focuses on the OWC WEC and the modelling of this device. A software model is implemented based on data obtained from a scaled prototype device situated at the Irish test site. Test data from the electrical system of the device is analysed and this data is used to develop a performance curve for the air turbine utilised in the WEC. This performance curve was applied in a software model to represent the turbine in the electro-mechanical system and the software results are validated by the measured electrical output data from the prototype test device. Finally, once both the DFIM and OWC WEC power take-off system have been modeled succesfully, an investigation of the application of the DFIM to the OWC WEC model is carried out to determine the electrical machine rating required for the pulsating power derived from OWC WEC device. Thermal analysis of a 30 kW induction machine is carried out using a first-order thermal model. The simulations quantify the limits of operation of the machine and enable thedevelopment of rating requirements for the electrical generation system of the OWC WEC. The thesis can be considered to have three sections. The first section of the thesis contains Chapters 2 and 3 and focuses on the accurate characterisation of the doubly-fed induction machine using various testing procedures. The second section, containing Chapter 4, concentrates on the modelling of the OWC WEC power-takeoff with particular focus on the Wells turbine. Validation of this model is carried out through comparision of simulations and experimental measurements. The third section of the thesis utilises the OWC WEC model from Chapter 4 with a 30 kW induction machine model to determine the optimum device rating for the specified machine. Simulations are carried out to perform thermal analysis of the machine to give a general insight into electrical machine rating for an OWC WEC device.

A COMPARISON OF MARKET CLEARING TOOLS IN ELECTRICITY SYSTEMS

To maintain a strict balance between demand and supply in the US power systems, the Independent System Operators (ISOs) schedule power plants and determine electricity prices using a market clearing model. This model determines for each time period and power plant, the times of startup, shutdown, the amount of power production, and the provisioning of spinning and non-spinning power generation reserves, etc. Such a deterministic optimization model takes as input the characteristics of all the generating units such as their power generation installed capacity, ramp rates, minimum up and down time requirements, and marginal costs for production, as well as the forecast of intermittent energy such as wind and solar, along with the minimum reserve requirement of the whole system. This reserve requirement is determined based on the likelihood of outages on the supply side and on the levels of error forecasts in demand and intermittent generation. With increased installed capacity of intermittent renewable energy, determining the appropriate level of reserve requirements has become harder. Stochastic market clearing models have been proposed as an alternative to deterministic market clearing models. Rather than using a fixed reserve targets as an input, stochastic market clearing models take different scenarios of wind power into consideration and determine reserves schedule as output. Using a scaled version of the power generation system of PJM, a regional transmission organization (RTO) that coordinates the movement of wholesale electricity in all or parts of 13 states and the District of Columbia, and wind scenarios generated from BPA (Bonneville Power Administration) data, this paper explores a comparison of the performance between a stochastic and deterministic model in market clearing. The two models are compared in their ability to contribute to the affordability, reliability and sustainability of the electricity system, measured in terms of total operational costs, load shedding and air emissions. The process of building the models and running for tests indicate that a fair comparison is difficult to obtain due to the multi-dimensional performance metrics considered here, and the difficulty in setting up the parameters of the models in a way that does not advantage or disadvantage one modeling framework. Along these lines, this study explores the effect that model assumptions such as reserve requirements, value of lost load (VOLL) and wind spillage costs have on the comparison of the performance of stochastic vs deterministic market clearing models.