Novel three-phase topology for cascaded multilevel medium-voltage conversion systems in large-scale PV plants

Solar photovoltaic renewable energy systems are expanding in the power sector thanks to its increasingly competitive prices. Traditionally, large-scale PV plants have reduced their cost by increasing the power ratings of the inverters and the line-frequency transformers. However, cost-reduction limits of large-scale PV plants are being reached. Cascaded converters have appeared as a solution to continue reducing the cost of large PV plants as they reduce the wiring cost. In this paper, a novel three-phase topology for cascaded conversion structures is proposed. It only has 2 conversion steps, one without switching losses. Hence, it increases the efficiency and reduces the cost of the previously proposed cascaded conversion systems. The topology is patent pending.The authors acknowledge the financial and continuous support of INGETEAM POWER TECHNOLOGY

El fin del ciclo de expansión del salitre en Chile: la inflexión de 1919 como crisis estructural

This article presents support for the view that the saltpetre crisis of 1919–1922 marked the end of the expansion cycle of nitrate in Chile. It also reports on the previously unknown social impact of this crisis. Even though recurrent crises and their respective peaks were a characteristic of this economy, the turning point reached in 1919–1922 had unprecedented consequences due to the definitive loss of the German market and the consolidation of synthetic nitrate. For the first time, this crisis made Chileans aware of the structural problems in its economy and the need to change the saltpetre policy established in the previous century. This paper challenges the traditional Chilean national historiography, which hadn’t considered this event as the end of the saltpetre industry, protracting its demise until the Great Depression of 1929.En este articulo se sostiene que la crisis salitrera de los años 1919-1922 marco el termino del ciclo de expansion del nitrato en Chile. Tambien se afirma que tuvo un impacto social desconocido hasta entonces, tanto por su extension como por su profundidad. Si bien fue un rasgo caracteristico de esta economia las recurrentes crisis con sus respectivos auges, la inflexion de 1919-1922 habria tenido caracteristicas ineditas hasta entonces, debido a la perdida definitiva del mercado aleman y por la consolidacion del nitrato sintetico. Con esta crisis por primera vez se habria tomado plena conciencia en Chile del problema estructural que enfrentaba esta economia, y la necesidad de cambiar la politica salitrera establecida en el siglo anterior. Sin embargo, al analizar este fenomeno, la historiografia nacional no ha considerado que esta inflexion fuera su final, sino que lo ha correlacionado con la Gran Depresion Mundial iniciada en 1929

Medium-voltage cascaded sequential topology for large-scale PV plants

Photovoltaic (PV) conversion systems are in continuous development due to their increasingly competitive prices. The traditional configuration of large-scale PV plants is based on high-power central inverters, which have reduced their cost by increasing their power rating. However, this cost reduction is expected to saturate in the near future, mainly due to an increase in the cost of the dc wiring. Cascaded conversion systems have appeared as potential solutions to continue reducing the PV plant cost. They consist of several conversion units whose ac outputs are connected in series. This enables the power-rating reduction of each individual conversion unit, while maintaining the power rating of the conversion structure. Thus, the conversion units are placed closer to the PV panels, reducing the dc wiring cost. In this paper, a novel three-phase topology for medium-voltage cascaded conversion systems is presented. The proposed topology is formed of several conversion units, each one with a reduced number of conversion stages, namely, dc/ac, medium-frequency isolation and ac/ac. Moreover, thanks to its sequential operation and modulation technique, zero-voltage switching and zero-current switching are achieved in all conversion stages. In this way, with respect to the configuration with central inverters, the proposed topology has the advantages of cascaded conversion systems. In comparison to previously investigated cascaded topologies, the proposed topology also presents promising characteristics, representing a potential cost reduction and efficiency increase. An experimental validation of the topology is carried out in a laboratory prototype consisting of three conversion units.This work was supported in part by the Spanish State Research Agency (AEI) under Grant PID2019-110956RB-I00 /AEI/10.13039/501100011033, and in part by the Public University of Navarre through a Ph.D. Scholarship

Active control for medium-frequency transformers flux-balancing in a novel three-phase topology for cascaded conversion structures

Efficiency and power density are important parameters in the design of power electronics converters. In many applications, low-frequency transformers are being substituted for medium-frequency and high-frequency transformers in order to reduce the volume and therefore the cost of the transformer. However, preventing their saturation is a complex task. This paper studies the medium-frequency transformers' flux balancing in a novel three-phase topology for cascaded conversion structures.Based on the modulation technique of the converter, a method to directly measure the magnetizing current of the medium-frequency transformers is proposed in this paper. A control loop to regulate the dc value of the magnetizing current is also designed and developed. Simulation results validate the correct operation of the control loop, which prevents the transformer saturation.This work was supported by the Spanish State Research Agency (AEI) under grants PID2019-110956RB-I00 /AEI/ 10.13039/501100011033 and DPI-2016-80641-R, and by the Public University of Navarre through a doctoral scolarship

Near-field photocurrent nanoscopy on bare and encapsulated graphene

Opto-electronic devices utilizing graphene have already demonstrated unique capabilities, which are much more difficult to realize with conventional technologies. However, the requirements in terms of material quality and uniformity are very demanding. A major roadblock towards high-performance devices are the nanoscale variations of graphene properties, which strongly impact the macroscopic device behaviour. Here, we present and apply opto-electronic nanoscopy to measure locally both the optical and electronic properties of graphene devices. This is achieved by combining scanning near-field infrared nanoscopy with electrical device read-out, allowing infrared photocurrent mapping at length scales of tens of nanometers. We apply this technique to study the impact of edges and grain boundaries on spatial carrier density profiles and local thermoelectric properties. Moreover, we show that the technique can also be applied to encapsulated graphene/hexagonal boron nitride (h-BN) devices, where we observe strong charge build-up near the edges, and also address a device solution to this problem. The technique enables nanoscale characterization for a broad range of common graphene devices without the need of special device architectures or invasive graphene treatment

Posibilidad de aprovechamiento de los RCD generados en obras de rehabilitación

Oftentimes, the incorporation of ordinances and application of regulations of technical, social,or urban nature imply an appropriate study and analysis of the building, the population affected, their habits and any of the consequences caused by the resolution of new demands. The research developed by the team REPROGRAMA in the University of Seville, CONTRATO I+D, related to the field of action of the Consejería de Fomento y Vivienda of the Agencia de Obra Pública de la Junta de Andalucía, considers the needs of intervention in the Andalusian housing stock built between the 1940s-80s, in order to improve an active aging process, taking into account a gender perspective, comfort requirements, energy savings, and environmental sustainability. Considering the rehabilitation of the housing stock as one of the greatest challenges of today for cities and always considering the three pillars of sustainability, this research is to reflect upon the existing reality and to propose protocols of intervention, which would satisfy the social needs and meet the demands of the current regulations, improving the quality of life for the users and the protection of the environment. In this presentation we explain an important part of the research we’ve done, the management of the RCD generated in the construction of energetic rehabilitation from one particular case of great singularity—the neighborhood of Nuestra Señora del Carmen in the district of Los Remedios of Seville. In this case, the planned constructions will create a great amount of waste, which should be taken into consideration since it could be one of the facets that questions the viability of the intervention. We will show our proposal of the RCD management, including quantification, assessment, minimization, selection and treatment in situ, and the possibilities of use of the original building. We will offer the results obtained in relation to reusing and recycling the wastes to reincorporate them to the building, extending its lifespan as a “secondary material”, as part of the natural process in reformation projects and rehabitilitaion of buildings, in accordance with the Directive 2008/98/CE or the Plan Nacional Integrado de Residuos (National Integrated Plan of Wastes) 2008-2015.A menudo, la incorporación de ordenanzas y normativas de aplicación de carácter técnico,social o urbano al parque de viviendas existente, implican un adecuado estudio y análisis de la edificación, la población afectada, sus hábitos y cualquiera de las consecuencias que puedan derivarse en la aplicación de las nuevas exigencias. Los trabajos desarrollados por el equipo REPROGRAMA de la Universidad de Sevilla, en el contrato I+D con la Consejería de Fomento y Vivienda de la Junta de Andalucía, tienen como objetivo el análisis de las necesidades de intervención en el parque edificado andaluz construido entre los años 40-80, sobre la base de favorecer el envejecimiento activo y desde la perspectiva de género, a partir de las exigencias de confort, ahorro energético y sostenibilidad ambiental. Considerando la rehabilitación del parque edificado como uno de los grandes retos de hoy en día para las ciudades y teniendo en todo momento presente los tres pilares de la sostenibilidad, esta investigación fija como objetivo general reflexionar acerca de la realidad existente y proponer protocolos de intervención, que satisfagan las necesidades sociales y cumplan con las exigencias normativas actuales, mejorando la calidad de vida de los usuarios y la protección del Medio Ambiente. En la ponencia que presentamos exponemos una parte relevante de los estudios desarrollados, la gestión de los RCD generados en las obras de Rehabilitación energética de un caso particular de gran singularidad, la Barriada de Nuestra Señora del Carmen en el barrio de los Remedios de Sevilla. En este caso, las obras previstas generarán un gran volumen de escombros cuyo destino final debe contemplarse, ya que puede suponer uno de los aspectos que cuestionen la viabilidad de la actuación. En el presente trabajo, mostraremos la propuesta de gestión de los RCD, incluyendo cuantificación, valorización, minimización, selección y tratamiento in situ, y posibilidades de aprovechamiento en el edificio origen. Ofreceremos los resultados obtenidos en relación a la reutilización y reciclado de los escombros para incorporarlos de nuevo al edificio alargando su vida útil como “material secundario”, como parte natural del proceso en los proyectos de reforma y rehabilitación de edificios, acorde con la Directiva 2008/98/CE o el Plan Nacional Integrado de Residuos 2008-2015

Validation of Cognitive Rehabilitation as a Balance Rehabilitation Strategy in Patients with Parkinson’s Disease: Study Protocol for a Randomized Controlled Trial.

Background: Parkinson’s disease (PD) is the second most common neurodegenerative disorder. This disease is characterized by motor symptoms, such as bradykinesia, tremor, and rigidity. Although balance impairment is characteristic of advanced stages, it can be present with less intensity since the beginning of the disease. Approximately 60% of PD patients fall once a year and 40% recurrently. On the other hand, cognitive symptoms affect up to 20% of patients with PD in early stages and can even precede the onset of motor symptoms. There are cognitive requirements for balance and can be challenged when attention is diverted or reduced, linking a worse balance and a higher probability of falls with a slower cognitive processing speed and attentional problems. Cognitive rehabilitation of attention and processing speed can lead to an improvement in postural stability in patients with Parkinson’s. Methods: We present a parallel and controlled randomized clinical trial (RCT) to assess the impact on balance of a protocol based on cognitive rehabilitation focused on sustained attention through the NeuronUP platform (Neuronup SI, La Rioja, Spain) in patients with PD. For 4 weeks, patients in the experimental group will receive cognitive therapy three days a week while the control group will not receive any therapy. The protocol has been registered at trials.gov NCT04730466. Conclusions: Cognitive therapy efficacy on balance improvement may open the possibility of new rehabilitation strategies for prevention of falls in PD, reducing morbidity, and saving costs to the health care system.post-print1014 K

Inhibition pattern of sulfamide-related compounds in binding to carbonic anhydrase isoforms I, II, VII, XII and XIV

A set of sulfamides and sulfamates were synthesized and tested against several isoforms of carbonic anhydrase: CA I, CA II, CA VII, CA XII and CA XIV. The biological assays showed a broad range of inhibitory activity, and interesting results were found for several compounds in terms of activity (Ki <1μm) and selectivity: some aromatic sulfamides are active against CA I, CA II and/or CA VII; while they are less active in CA XII and CA XIV. On the other hand, bulky sulfamides are selective to CA VII. To understand the origin of the different inhibitory activity against each isozyme we used molecular modeling techniques such as docking and molecular dynamic simulations.Facultad de Ciencias Exacta

Outcomes of liver transplantation with thoracoabdominal normothermic regional perfusion: a matched-controlled initial experience in Spain

Thoracoabdominal (TA) normothermic regional perfusion (NRP) should allow the safe recovery of heart and liver grafts simultaneously in the context of controlled donation after circulatory death (cDCD). We present the initial results of cDCD liver transplantation with simultaneous liver and heart procurement in Spain until October 2021. Outcomes were compared with a matched cohort of cDCD with abdominal NRP (A-NRP) from participating institutions. Primary endpoints comprised early allograft dysfunction (EAD) or primary non-function (PNF), and the development of ischemic-type biliary lesions (ITBL). Six transplants were performed using cDCD with TA-NRP during the study period. Donors were significantly younger in the TA-NRP group than in the A-NRP group (median 45.6 years and 62.9 years respectively, p = 0.011), with a median functional warm ischemia time of 12.5 min in the study group and 13 min in the control group. Patient characteristics, procurement times, and surgical baseline characteristics did not differ significantly between groups. No patient in the study group developed EAD or PNF, and over a median follow-up of 9.8 months, none developed ITBL or graft loss. Extending A-NRP to TA-NRP for cardiac procurement may be technically challenging, but it is both feasible and safe, showing comparable postoperative outcomes to A-NRP