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

A novel ‘sea-thermal’, synergistic co-valorisation approach for biofuels production from unavoidable food waste (almond hulls) and plastic residues (disposable face masks)

This work first-time addresses the synergetic hydrothermal co-valorisation of almond hulls (an unavoidable food waste) and FFP2 face masks (a common plastic material) using seawater (a sustainable reaction medium). The effects of the feedstock composition (each material alone and all possible binary combinations) and the reaction medium (deionised water, seawater and all possible binary mixtures) have been evaluated at 350 °C and 170 bar over a wide range of reaction times (20–180 min). Bilateral biomass-plastic synergistic and antagonistic interactions between both feedstocks, combined with several promoting and inhibiting effects displayed by seawater, ruled the distribution of the reaction products and their most important physicochemical and fuel properties. Process optimisation revealed that the formation of an energy-dense (32 MJ/kg) liquid biofuel was maximised (26% biocrude yield) by conducting the process with almond hulls in deionised water for 115 min. At the same time, face masks promoted solid biofuel formation (83% hydrochar yield, 46 MJ/kg) by coprocessing an almond hulls/disposable face masks mixture (8:92 wt%) in salted (seawater/deionised water mixture with 37471 ppm salinity) water for 180 min. Conducting the process with seawater (44608 ppm salinity) for 180 min allowed coprocessing of both materials (22/78 wt% almond hulls/face masks) efficiently to maximise biofuels production (13% biocrude yield, HHV = 33 MJ/kg and 67% hydrochar yield, HHV = 49 MJ/kg). These results are a breakthrough in developing season-free and flexible biorefineries, which contribute to reducing pollution and bringing out the hidden value of human activity common residues

Laser marking of polymers. Work methodology

Laser marking of polymers. Work Methodology. Context The aim of this work is to obtain a work protocol for laser marking of polymers (figure 1). An in depth study regarding the ‘state of the art’ (articles, patents, books, dissertations) about the laser-polymer interaction, laser parameters, photo chemical/thermical processes, mechanical properties of polymers and optical characterization will be carried out. During laser marking, different phenomena can be observed from the most common photothermical processes to photochemical reactions. Those phenomena are not only due to the raw material, but also to different additives, wavelengths and laser parameters. This work will be developed with the resources available at the company B.S.H. (Balay) and the University of Zaragoza, mainly with the laser processing of materials group and the liquid crystals and polymers group. Initial proposal As starting materials for the study of laser marking, the following commercial polymers are proposed: ABS, SAN, PBT, PMMA and mainly PP. Regarding the irradiation following wavelengths are proposed: 1064, 532 and 355 nm covering IR, visible and UV spectra. Special interest will be paid to 355nm (UV) because in this range the possibilities of photochemical processes increases. Control of raw material There is a strong interest in controlling the raw material and additives, so alternatives for the production of different polymer plates will be studied; partially to identify the relationships between different phenomenology and additives. To control the raw material a profound knowledge of the quantitative and qualitative composition of the material is necessary. For the analysis various tools can be enhanced (XPS, ATR, EDX). Experiments According to the ‘state of the art’ different experiments are proposed, carrying them out on both, the raw material and the marks. The experiments fall into various investigation backgrounds, the different fields are shown below. . Design of experiments (DoE): parameter selection, factorial design. • Mathematical models: photo chemical/thermical rate, thermal models. • Mechanical properties: hardness and scratch resistance of the marks. • Temperature: measurement different tools • Morphology: roughness, appearance and depth of marks. • Optical characterization: Contrast and color distance (CIELab), absorption spectra. • Detection of photochemical/photothermical phenomena: carbonization, foaming, photo reduction, bond breaking, ablation, incubation, blocking. Importance of experimental results The experimental results must be discussed leading to conclusions. According to the conclusions the experiments can be accepted, discarded or adapted defining a solid work methodology suitable for a wide group of polymers

La importancia de la literatura para la enseñanza de la lengua extranjera en la educación primaria

La finalidad central de esta revisión bibliográfica es detectar las dinámicas beneficiosas que rodean a la literatura en el proceso de enseñanza-aprendizaje del inglés como lengua extranjera en la educación Primaria. Para esta revisión, hemos analizado el origen de la aparición y desarrollo del lenguaje. A partir de este análisis hemos seguido con los beneficios que produce la introducción de una segunda lengua o idioma dentro de un mismo individuo según diversos autores. Continuando finalmente con el desarrollo del trabajo desglosamos los diversos beneficios que tiene la literatura específicamente como herramienta en el desarrollo y aprendizaje de la comunicación y expresión lingüística en la educación Primaria.The main purpose of this bibliographic review is to detect the beneficial dynamics that surround literature in the teaching-learning process of English as a foreign language in Primary education. For this review, we have analyzed the origin of the appearance and development of language. From this analysis we have continued with the benefits produced by the introduction of a second language or language within the same individual according to various authors. Finally continuing with the development of the work we break down the various benefits that literature has specifically as a tool in the development and learning of communication and linguistic expression in Primary education

Impedance-based analysis of harmonic resonances in HVDC connected offshore wind power plants

During the last years, the installation and planning of offshore wind farms using HVDC-links to transmit power onshore has increased. After the first HVDC connected offshore wind power plant of this type had been commissioned, the electrical harmonic resonance at the offshore AC grid was observed. The phenomenon leads to unwanted outages on both wind turbines and the HVDC transmission system. This paper aims to present the harmonic resonances in power-electronics dominated grids such as HVDC connected wind power plants. The study focuses on harmonic frequencies identification which are excited through the resonance phenomena between the elements of the offshore AC network including power converters. The paper presents a comparison of three different methodologies existing in the literature for harmonic resonance analysis including stability analysis. Moreover, we analyse the impact of the different power converter models application. The models and methods are validated in different test cases in order to determine the relationship of such resonances with respect to the grid topology.Postprint (author's final draft

Operational strategies, monitoring and control of heterologous protein production in the methylotrophic yeast Pichia pastoris under different promoters: A review

The methylotrophic yeast Pichia pastoris has been widely reported as a suitable expression system for heterologous protein production. The use of different phenotypes under PAOX promoter, other alternative promoters, culture medium, and operational strategies with the objective to maximize either yield or productivity of the heterologous protein, but also to obtain a repetitive product batch to batch to get a robust process for the final industrial application have been reported. Medium composition, kinetics growth, fermentation operational strategies from fed-batch to continuous cultures using different phenotypes with the most common PAOX promoter and other novel promoters (GAP, FLD, ICL), the use of mixed substrates, on-line monitoring of the key fermentation parameters (methanol) and control algorithms applied to the bioprocess are reviewed and discussed in detail

Stimuli Responsive Polymeric Nanoparticles for Controlled Release of Cargo Molecules

Block copolymers (BCs) are complex macromolecules having, at least, two different polymeric chains chemically connected. These blocks are, in general, mutually immiscible, which leads to phase separation. Due to the length of the macromolecular blocks, this segregation occurs at the nanoscale. If BCs are formed by hydrophilic and hydrophobic blocks (amphiphilic BCs) these materials can undergo segregation in a selective solvent, e.g. water, resulting on micelles or vesicles above a critical concentration, as occurs with surfactants. Polymeric micelles or vesicles have higher stability than those formed by low molecular weight amphiphiles and have been explored in Medicine as nanocarriers for targeted drug delivery. Objective of this project is the preparation of nanoparticles from amphiphilic BCs to bond stimuli-responsive molecules by multiple hydrogen bonding (molecular recognition). Hydrophobic blocks having 2,6-diacylaminopyridine moieties will be employed for supramolecular assemblies. The high tendency to form polymeric nanoparticles of these BCs will be studied. Azobenzene groups will be easily incorporated to provide a light response to the nanoparticles that can be used for the release of cargo molecules. Furthermore, the presence of pyridine rings also provide of a pH response. Tasks to be carried out in this project initially are: - Preparation of precursors and supramolecular amphiphilic BCs having 2,6-diacylaminopyridine groups. - Complete characterization of the prepared materials, including spectroscopic and thermal analysis techniques. - Preparation of polymeric nanoparticles by using different methodologies and study by transmission electron microscopy

Stability assessment for multi-infeed grid-connected VSCs modeled in the admittance matrix form

© 2021 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksThe increasing use of power electronics converters to integrate renewable energy sources has been a subject of concern due to the resonance oscillatory phenomena caused by their interaction with poorly damped AC networks. Early studies are focused on assessing the controller influence of a single converter connected to simple networks, and they are no longer representative for existing systems. Lately, studies of multi-infeed grid-connected converters are of particular interest, and their main aim is to apply traditional criteria and identify their difficulties in the stability assessment. An extension of traditional criteria is commonly proposed as a result of these analysis, but they can be burdensome for large and complex power systems. The present work addresses this issue by proposing a simple criterion to assess the stability of large power systems with high-penetration of power converters. The criterion has its origin in the mode analysis and positive-net damping stability criteria, and it addresses the stability in the frequency domain by studying the eigenvalues magnitude and real component of dynamic models in the admittance matrix form. Its effectiveness is tested in two case studies developed in Matlab/Simulink which compare it with traditional criteria, proving its simplicity.Peer ReviewedPostprint (author's final draft

Introducing Augmented Reality in Cultural Heritage Studies

Augmented Reality is a technology that allows overlaid digital content into our view of the real world through the camera of a Smartphone or a tablet. Video, audio, 2D and 3D images, web and text are just some examples of the type of content that can be overlaid on our perception of the real world. This content can be associated with real world elements by means of geolocation or image recognition. Such technology has great engagement potential and is used in many fields to augment the users’ perception of the world. Cultural heritage is one of the fields that could benefitmore from this technology. This paper describes how augmented reality has been used in an educational context in order to support learning for cultural heritage students. The students taking part in this experience built landscape units in several locations in Catalonia and augmented them with digital information, creating digital Points of Interest distributed throughout Catalonia and Spain. These Points ofInterest, which constitute a mix of digital and real world information, were then published through an augmented reality browser, making them freely available to the public. Today there are more than 5,000 freely available Points of Interest that have been created by the students. The results of the experiment show that students appreciate the use ofaugmented reality in this particular context and find it useful both from a pedagogical and a technological point of view