Power systems with high renewable energy sources: A review of inertia and frequency control strategies over time

Traditionally, inertia in power systems has been determined by considering all the rotating masses directly connected to the grid. During the last decade, the integration of renewable energy sources, mainly photovoltaic installations and wind power plants, has led to a significant dynamic characteristic change in power systems. This change is mainly due to the fact that most renewables have power electronics at the grid interface. The overall impact on stability and reliability analysis of power systems is very significant. The power systems become more dynamic and require a new set of strategies modifying traditional generation control algorithms. Indeed, renewable generation units are decoupled from the grid by electronic converters, decreasing the overall inertia of the grid. ‘Hidden inertia’, ‘synthetic inertia’ or ‘virtual inertia’ are terms currently used to represent artificial inertia created by converter control of the renewable sources. Alternative spinning reserves are then needed in the new power system with high penetration renewables, where the lack of rotating masses directly connected to the grid must be emulated to maintain an acceptable power system reliability. This paper reviews the inertia concept in terms of values and their evolution in the last decades, as well as the damping factor values. A comparison of the rotational grid inertia for traditional and current averaged generation mix scenarios is also carried out. In addition, an extensive discussion on wind and photovoltaic power plants and their contributions to inertia in terms of frequency control strategies is included in the paper.This work was supported by the Spanish Education, Culture and Sports Ministry [FPU16/04282]

Convergencia Europea, Trabajo Social y nuevas tecnologías

Within the article, we enumerate the three fundamental axes for European Convergence regarding Higher Education. It then focuses on the second of these axes which deals with the successful factors of this process, especially the second: learning versus teaching. In this regard, we will report on what is being done at our SSW (UCM). In particular, we will explain the following points: a) the experience obtained from the pilot programme on support for teaching which the UATD (Unidad de Apoyo Técnico a la Docencia) [Technical Teaching Support Unit], started up during this 2003-2004 academic year, and how this is being implemented in several subjects, and, b) our experience with European Networks and the importance of the Erasmus Mundus Programmes for postgraduates at our schools within the EU framework.En este artículo nos centraremos en el segundo de los tres ejes fundamentales del proceso de Convergencia Europea en Enseñaza Superior (CEES). De los tres factores de éxito de dicho proceso de los que habla el citado eje, hemos elegimos el segundo de ellos —aprendizaje versus enseñanza— para dar cuenta de qué se está haciendo en la EUTS de la UCM. En concreto, expondremos: a) la experiencia piloto sobre apoyo a la docencia que la UATD (Unidad de Apoyo Técnico a la Docencia) puso en marcha en el curso 2003-2004, y cómo lo hemos instrumentalizado en distintas asignaturas de Trabajo Social, y, b) lo que estamos haciendo en redes europeas y la importancia de los programas Erasmus Mundus para los postgrados en nuestras escuelas en el marco de la Convergencia Europea (CE)

Reduced kinetic mechanisms for modelling LPP combustión in gas turbines

Reduced kinetic mechanisms for modelling LPP combustión in gas turbine

Experiments conducted on combustion at microgravity in the TEXUS-38 sounding rocket

A series of experiments linked together on combustion at microgravity have been conducted in a TEXUS-38 sounding rocket. The experiments were performed with three cylindrical hollow rods of polymethylmethacrylate. Test were carried out in O2-N2 mixtures at rest and at flow velocities ranging from 10 to 30 mm/s. O2-N2 mixture composition changed from 40% oxygen down to pure nitrogen. The sequence of experiments consisted of: 1º.- Measurement of flame temperatures in the non-visible optical range. 2º.- Determination of O2 concentrations at flame extinction at constant flow velocity, obtained by continuously reducing the O2 concentration in the test section. 3º.- Measurement of flame spreading velocities. 4º.- Some information on the influence on flammability of the ignition location and time, and fuel thickness. Main conclusions are: 1º.- Flames in the infrared, non-visible optical range have a substantially lower temperature. 2º.- O2 concentration at flame extinction depends considerably on flow velocity, especially at low velocity levels. Final conclusion is that the flow velocity field of maximum interest is the one in which flow velocities are of the same order of magnitude as typical diffusion velocities. A follow-on program in this subject will be conducted in the US Combustion Module of the International Space Station

El turisme actiu a Espanya. Identificació de la qualitat del servei en les empreses

Va ser el 2012 quan es va finalitzar el disseny de l’eina per a la identificació de la qualitat en el servei de les empreses de turisme actiu, l’anomenada eina valorativa HEVA. El 2013 es va llançar la proposta a totes les empreses de turisme actiu registrades en les 52 oficines de turisme de les províncies del territori nacional, i es va obtenir un registre de 918 empreses actives, 186 de les quals s’han utilitzar per a aquest estudi. HEVA analitza tres aspectes fonamentals: la identificació del perfil sectorial de les empreses, la valoració dels paràmetres que reconeixen la qualitat del servei i la percepció del responsable de l’empresa en relació amb el que la clientela identifica com a qualitat del servei que presta. Aspectes clau per conèixer i poder determinar processos que ajudin la gestió de les empreses. Com a conclusions, les entitats consideren que està més reconeguda la seva activitat empresarial dins del sector del turisme (80,6 %) que de l’esport. Pel que fa a la valoració dels paràmetres de qualitat en el servei, s’identifica que el paràmetre dels recursos humans obté el major reconeixement (97,7 %). I referent a la percepció del responsable de l’empresa, hi ha diferències significatives per a la clientela en elements com el tractament de les reclamacions i els productes complementaris