2,928 research outputs found
Recent evolution of poverty in the European countries
The purpose of this paper is to analyze the evolution of poverty in the 15 countries of E.U., whose household income data is available through the information contained in the European Community Household Panel (ECHP). Several indicators have been proposed in economic literature for measuring poverty, but they may produce different orderings when cases are compared. In this work, a set of poverty one-dimensional indicators are chosen, which best verify some desirable properties. A modification of the Principal Component Analysis (PCA) is proposed to calculate synthetic cross-sectional measures of poverty using this set of indicators. In order to obtain comparable values throughout time, in addition to cross-sectional sense, joint consideration of single poverty indicators is proposed, independently of their temporary period of reference. Therefore, applying common space analysis to these cross-sectional synthetic measures, a common frame of comparison and a homogeneous weighting structure are obtained, which are stable throughout time. This powerful tool allows static as well as dynamic comparisons, among the EU countries. Furthermore, the determination of groups of countries according to their characteristics in poverty will be accomplished.
Estrategias policiales y otros mecanismos de prevención
[ES] Tras realizar un breve repaso de los puntos sobre los que se apoya en Europa la estrategia pública frente al fenómeno de las sectas destructivas, se muestra un ejemplo de dicha labor en un ámbito concreto: el relativo a la relación entre sectas y drogas. Asimismo, se exponen las estrategias públicas ante este problema, y se apuntan algunas ideas que sirven para debatir las posibles lÃneas de trabajo preventivo policial en materia de sectas destructivas.[EU] Sekta suntsitzaileen aurkako fenomenoekiko Europako estrategia publikoari buruz errepasoa egin ondoren, lan horri buruzko adibide bat azaltzen da kasu konkretu batetan: sekta eta drogen arteko erlazioa. Arazo horren aurrean dauden estrategia publikoak azaltzen dira, eta sekta suntsitzaileen aurka egin behar den prebentzio polizial lana nola eraman daitekeen ideia batzuk azaltzen dira.[FR] Après avoir effectué un bref examen des points sur lesquels on soutient en Europe la stratégie publique visant au phénomène des sectes destructives, on montre un exemple de cette tâche dans un cadre concret: la relation entre les sectes et les drogues. De même, on expose les stratégies publiques visant à ce problème, et on signale quelques idées pour débattre les possibles lignes de travail préventif policier en matière de sectes destructives.[EN] After making a brief review of the points on which the European public strategy to face the destructive sects’ phenomenon is based, it is shown an example of this work in a concrete field: the relation between sects and drugs. Also, the public strategies to face this problem are explained, and some ideas to debate the possible lines of the police preventive work on the subject of destructive sects are suggested
Analysis of the contribution of wind power plants to damp power system oscillations
Wind power has emerged as one of the most promising renewable energy sources. The very penetration levels of wind energy in power systems have altered several aspects of power system operation, such as system stability. Owing to the large penetration of wind power, transmission system operators (TSOs) have established special grid codes for wind farms connection. These grid codes require wind farms to provide ancillary services to the grid such as frequency and voltage regulation. In the near future, the capability of damping power system oscillations will be required. As a result of the development of such requirements, the concept of wind power plant (WPP) arises being de ned as a wind farm which is expected to behave similarly to a conventional power plant in terms of power generation, control and
ancillary services.
As future grid codes will require power oscillation damping contribution from wind power, the thesis is mainly focused on the analysis of the power system stabilizer (PSS) capability of wind power plants. The change produced by wind power plants based on di erent wind turbine technologies on power system small signal dynamics is analysed to determine their possible contribution to damp oscillations. The eff ect of the distance from the tie line to the wind power plant on the controller response and the influence of wind power plants proximity to synchronous generators are demonstrated to be critical factors. At this point several questions are raised as: What are the most critical factors? How can be ensure a proper contribution, at least the best possible response? Can it be ensured to be independent to
the power system and the controller selected?
To answer these questions, this thesis conducts research on proper selection of input-output signal pairs to damp out electromechanical oscillations using wind power plants without drawing attention to a particular control design. This is necessary conclusions about the power system independently of a particular controller. The capability to damp is an intrinsic characteristic of the system and should not be a ected by a particular controller (PSS).
Firstly, di erent analysis techniques are compared, considering both controllability and observability measures and input-output interactions. This enables recommendations to be drawn so as to the selection of the the best signal pairs to damp power system oscillations considering di erent approaches, such as single-input single-output (SISO) and multivariable control (MIMO). Second, a new criterion to select the best input-output signals used by a PSS based on WPPs is presented, considering explicitly local and remote signals in the analysis. Taking into account fundamental design limitations and using controllability and observability concepts, the criterion is able to identify the most suitable pair of input-output local signals without consider any particular controller. Finally, due to the increase of wind power generation - including o shore locations - and the concept of an interconnected Pan-European network, a new o shore wind power plant AC network similar in design to the European SuperGrid \SuperNode", is analyzed. The cost e ect of choosing a nonstandard operating frequency on the o shore AC network is investigated. As the o shore AC network is isolated from onshore networks through the use of HVDC links, it may be operated in an asynchronous fashion and at a suitable frequency. The cost associated with operating the network at a fixed frequency in the range 20 to 120 Hz is investigated, focusing on the frequency-cost-scalings of electrical devices (such as cables, transformers and reactive compensation) and the related o shore infrastructures,L'energia e olica s'ha convertit en una de les fonts d'energia renovable m es prometedores. Actualment, l'elevat nivell de penetraci o de l'energia e olica a la xarxa el ectrica ha conduï t a la modi caci o del comportament de diversos aspectes d'aquesta, com per exemple, l'estabilitat. Degut a aquesta gran penetraci o, els operadors de xarxes de transmissi o (TSOs) han establert procediments d'operaci o especials per a la connexi o de grans parcs e olics. Aquests codis requereixen als parcs elics que realitzin serveis auxiliars al sistema el ectric com, per exemple, la regulaci o de freqü encia i la regulaci o de la pot encia reactiva. En un futur proper, la capacitat dels parcs e olics per
esmorteir les oscil lacions del sistema de pot encia es requerir a (en l'actualitat ja existeixen esborranys de nous procediments d'operaci o que ho inclouen).
A causa d'aquest requeriments, el concepte de central de generaci o d'energia e olica es de neix com un parc e olic que s'espera que es comporti de manera similar a una central de generaci o el ectrica convencional en termes de poder realitzar tasques tals com generaci o, control i serveis auxiliars. Ja que un futur requeriment dels operadors de xarxa ser a la contribuci o de l'energia e olica en l'esmorteiment de les oscil lacions de pot encia, en aquesta tesi s'estudia la capacitat de les centrals e oliques per actuar com estabilitzador dels sistemes el ectrics de pot encia. A m es a m es, s'analitza l'efecte de les centrals d'energia e olica al comportament din amic del sistema el ectric considerant l'estabilitat de petita senyal, per a determinar quina podr a ser la possible contribuci o proporcionada per aquestes tecnologies. S'ha estudiat
que l'efecte de la dist ancia des d'el punt de connexi o amb la central d'energia e olica a la resposta del control estabilitzant i la influ encia de la proximitat de les centrals e oliques als generadors s ncrons s on factors cr tics. D'aquest fet surgeixen algunes preguntes com: Es aquest el factor m es cr tic? Com es pot assegurar una contribuci o adequada, si m es no la millor resposta possible, per ajudar a estabilitzar el sistema el ectric? Es poden asegurar quina ser a la contribuci o a l'estabilitat del sistema el ectric independentment de la xarxa i l'esquema de control escollit?
Per respondre a aquestes preguntes, aquesta tesi ha realitzat investigacions sobre l'adequada selecci o de parells de senyals d'entrada-sortida per esmorteir les oscil lacions electromec aniques amb centrals e oliques evitant dissenyar el controlador i propossant met odes f acilment adaptables a qualsevol sistema el ectric. En primer lloc, s'han comparat diferents t ecniques d'an alisi tenint en compte tant les mesures de controlabilitat i observabilitat com les interaccions entre les senyals d'entrada i sortida. D'aquesta comparaci o, certes recomanacions es donen a l'hora de seleccionar els millors parells de senyals per esmorteir les oscil lacions del sistema el ectric de pot encia considerant diferents esquemes de control com ara entrada unica sortida unica (SISO) i control multivariable (MIMO). En segon lloc, s'ha proposat un nou criteri per seleccionar les senyals d'entrada i sortida utilitzades per un control estabilitzador per centrals d'energia e olica. On, a difer encia amb anteriors met odes de selecci o proposats, el criteri presentat considera expl citament tant senyals locals com senyals remotes dins el seu an alisi. Aquest criteri es capa c d'identi car la parella de senyals locals d'entrada i sortida m es adequada sense realitzar el disseny del controlador, considerant tant les limitacions fonamentals del disseny del controlador imposades per el sistema com els conceptes de controlabilitat i observabilitat.
Finalment, a causa del augment de la generaci o d'energia e olica, principalment en localitzacions marines, i al concepte d'una xarxa el ectrica comuna Pan-Europea, s'ha realitzat l'an alisi d'un nou concepte de xarxa en corrent altern (AC) dins de les centrals d'energia e olica marina, amb un disseny similar al concepte investigat a la Super-Xarxa Europea \Supernode". En aquest treball s'ha investigat l'efecte que t e en els costos la tria una freqüencia nominal d'operaci o no est andard en dita xarxa en corrent altern. La xarxa en AC que es forma entre les turbines e oliques i el convertidor de transmissi o es aï llada tant de les xarxes terrestres per l' us d'enlla cos en corrent continu (HVDC) com de la pr opia de les turbines per el convertidor que porten incorporat. Aquest fet implica que aquesta xarxa pot ser operada sense sincronitzar
a qualsevol freqüencia.
En aquesta tesi, s'ha estudiat quin es el cost associat amb l'operaci o de la xarxa a una freqü encia fi xa dins del rang de 20-120 Hz, focalitzant principalment en l'escalat del costos dels diferents elements el ectrics (com ara cables, transformadors i compensaci o reatviva i
infraestructures necessaris en instal lacions marines respecte la freqüencia
Modeling and control of squirrel cage induction generator with full power converter applied to windmills
The project aims to develop a dynamic model, of a generation system of electrical energy with
a variable speed wind turbine using a squirrel cage induction generator which is connected
to the grid by a back to back frequency converter, for testing purposes.
In the project has been done an analysis of the mathematical equations of the whole system,
separating the mechanical system (turbine and gearbox) and the electrical (generator and
converter).
We study the control design of the machine which allow us to obtain the maximum wind
power extraction, and we also study the control of the converter which couple the generator
with the network.
The proper functioning of the model is checked comparing the obtained results with some
commonly known results.Outgoin
Control of multi-terminal HVDC networks towards wind power integration: A review
© 2015 Elsevier Ltd.
More interconnections among countries and synchronous areas are foreseen in order to fulfil the EU 2050 target on the renewable generation share. One proposal to accomplish this challenging objective is the development of the so-called European SuperGrid. Multi-terminal HVDC networks are emerging as the most promising technologies to develop such a concept. Moreover, multi-terminal HVDC grids are based on highly controllable devices, which may allow not only transmitting power, but also supporting the AC grids to ensure a secure and stable operation. This paper aims to present an overview of different control schemes for multi-terminal HVDC grids, including the control of the power converters and the controls for power sharing and the provision of ancillary services. This paper also analyses the proposed modifications of the existing control schemes to manage high participation shares of wind power generation in multi-terminal grids.Postprint (author's final draft
PolicÃa y conflicto. Un análisis de las demandas sociales que se expresan a través de los medios de comunicación
Sufficient conditions for controllability and observability of serial and parallel concatenated linear systems
This paper deals with the sufficient conditions
for controllability and observability characters of finitedimensional
linear continuous-time-invariant systems of serial
and parallel concatenated systems. The obtained conditions
depend on the controllability and observability of the systems
and in some cases, the functional output-controllability of the
first one.Peer ReviewedPostprint (published version
The mOxy-CaL Process: Integration of Membrane Separation, Partial Oxy-combustion and Calcium Looping for CO2 Capture
CO2 capture and storage (CCS) is considered as a key strategy in the short to medium term to mitigate global
warming. The Calcium-Looping process, based on the reversible carbonation/calcination of CaO particles, is a
promising technology for post-combustion CO2 capture because of the low cost and non-toxicity of natural CaO
precursors and the minor energy penalty on the power plant in comparison with amines capture based
technologies (4-9 % compared to 8-12 %). Another interesting process to reduce CO2 emissions in power plants
is oxy-combustion, which is based on replacing the air used for combustion by a highly concentrated (~95 %
v/v) O2 stream. This work proposes a novel process (mOxy-CaL) for post-combustion CO2 capture based on
the integration of membrane separation, partial oxy-combustion and the Calcium-Looping process. An oxygenenriched
air stream, which is obtained from air separation by using highly permeable polymeric membranes, is
used to carry out partial oxy-combustion. The flue gas exiting partial oxy-combustion shows a CO2 concentration
of ~30 % v/v (higher than 15 % v/v typical in coal power plants). After that, the flue gas is passed to the CaL
process where the CO2 reacts with CaO solids according to the carbonation reaction. Thermogravimetric
analysis show that the multicycle CaO conversion is enhanced as the CO2 concentration in the flue gas stream
is increased. Process simulations show that the mOxy-CaL process has a high CO2 capture efficiency (~95%)
with lower energy consumption per kg of CO2 avoided than previously proposed post-combustion CO2 capture
technologies. Moreover, the overall system size is significantly lower that state-of-the-art CaL systems, which
allows for an important reduction in the capital cost of the technology
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