Multilevel single phase isolated inverter with reduced number of switches

This paper proposes a cascaded single phase multilevel inverter using an off-the-shelf three-phase inverter and transformer. The concept is based on a cascaded connection of two inverter legs using a typical three phase inverter in such a way that the third leg is shared between the other two phases. The cascaded connection is achieved through an integrated series transformer with a typical three-phase transformer core. Utilization of a special transformer design has been previously proposed in the Custom Power Active Transformer. However, cascaded connection of inverter legs has not been previously investigated with such a concept. In this way, a three-leg inverter and a three-phase transformer are converted into an isolated multilevel single-phase inverter based on an unique configuration and modulation technique.Postprint (author's final draft

Synchronous frequency support of photovoltaic power plants with inertia emulation

©2019 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 works.Grid stability is one of the main concerns in renewable energies. The lack of inertia and their low capability to provide frequency support has created the need for implementing new control strategies to solve this problem. In current networks, frequency and voltage support are performed through synchronous generators, which provide an inherent grid support due to the inertia presented in their mechanical rotors. Based on the same concept, renewable energies based on power converters have introduced synchronous controllers to emulate the dynamic behavior of synchronous generators and provide voltage and frequency support. However, most synchronous control strategies integrate their controllers as an add-on firmware embedded in each power converter, without presenting a coordinated synchronous performance when several converters operate in a PV power plant. The aggregation of several power converters operating with a coordinated synchronous response would be advantageous in these cases, since they can provide a harmonic response with an automatic power distribution when grid support is required. This paper presents a synchronous control strategy for photovoltaic power plants, which manages several power converters as an aggregated synchronous system.Peer ReviewedPostprint (author's final draft

Energy balancing with wide range of operation in the isolated multi-modular converter

The series-connection of modules in multilevel converters are prone to energy imbalances in the dc capacitor due to the differences between the power absorbed and consumed. In renewable energy applications where the primary source is directly connected to each module, energy imbalances can be even worse if the primary sources are affected by unpredictable weather conditions. Therefore, control strategies are required to compensate such energy imbalances, while maintaining the correct converter operation. Focusing our attention on a cascaded transformer multilevel inverter called Isolated MultiModular Converter, this paper introduces the combination of two control strategies aimed at providing a wide range of operation under imbalanced energy states. A general analytical model, including the regulation capability and differences with an existing strategy are presented to demonstrate the performance of the control proposed. The effectiveness of the proposal is validated through experimental results based on a three-phase multilevel prototype.This work was supported in part by the European Commission under Project FLEXITRANSTORE—H2020-LCE-2016-2017-SGS-774407 and Project INTERRFACE—H2020-LC-SC3-2018-ES-SCC-824330, and in part by the Spanish Ministry of Science under Project ENE2017-88889-C2-1-R.Peer ReviewedPostprint (published version

Diagnóstico del nivel de conocimientos y valoración de los efectos de la contaminación atmosférica por material particulado en estudiantes de Enseñanza Media de la Región del Maule

The aim of this study was to develop a knowledge diagnosis and assessment of high school students in relation to air pollution by particulate matter. The re- search is a descriptive cross-sectional survey study. The analysis was per- formed by means of a lexicon and a test was applied to a sample group of high school students. Very low levels of knowledge were detected in both insti- tutions, and the school in the commune of Talca showed higher values compa- red to the district of La Molina. 68% of students in both districts claimed they had never addressed the issue in class, and admitted that informal education (86% in Talca and 78% in Molina) was their most relevant source of knowledge on the subject, naming open TV and in- ternet as their most important sources. It can be concluded that both institu- tions show decreasing values regarding the degree of knowledge of air pollution by particulate matter. These results su- ggest the need for the development of educational policies in order to improve the knowledge level of both communes.El objetivo del presente estudio fue elaborar un diagnóstico del conoci- miento y valoración de estudiantes de Educación Media en relación con la contaminación atmosférica por mate- rial particulado. La investigación es un estudio descriptivo transversal por en- cuesta. El análisis se efectuó por medio de un lexicón y se aplicó un test a una muestra piloto de estudiantes de Edu- cación Secundaria. Se detectó niveles de conocimientos muy descendidos en ambas instituciones; además, el liceo de la comuna de Talca mostró valores más altos en relación con la comuna de La Molina. El 68% de los estudiantes de ambas comunas declararon que nunca han tratado el tema en clases y reco- nocen que la educación informal (86% en Talca y 78% en Molina) es su fuente de conocimiento más relevante sobre el tema, por ejemplo, la TV abierta e in- ternet son las fuentes más importantes. Se concluye que ambas instituciones presentan valores descendidos res- pecto al grado de conocimiento de la contaminación atmosférica por material particulado. Estos resultados sugieren el desarrollo de políticas educacionales para mejorarlo en ambas comunas

Model and control of the isolated multi-modular converter

Multi-modular converters have proven to be one of the most suitable topology to be used in high and power applications. The modularity of these configurations offer several advantages, such as: high quality voltage, redundancy and high efficiency. In these converters, the series connection of modules increase the number of voltage levels, but also the floating voltage of modules with respect the neutral point connection which may give rise to isolation issues at the DC side. Because of this, modules with two or more conversion stages are used to provide isolation and to prevent high floating voltages. However, increasing the number of conversion stages, increase also the losses and the implementation costs. In order to overcome these drawbacks, a new configuration of multi-modular converter is proposed in this paper. The proposed converter provides isolation with one conversion stage by means of using low frequency transformers in each module. The main principle behind this concept, the control structure and simulation results are presented to validate the proposed configuration.Peer ReviewedPostprint (author's final draft

Three-phase isolated multi-modular converter in renewable energy distribution systems

Multilevel converters are widely used in medium and high voltage applications. Their high performance, power quality, efficiency and smaller filters make them interesting for renewable energy distribution systems. In utility- scale photovoltaic plants, these topologies could provide multiple benefits since they are able to connect string of photovoltaic panels to independent modules. However, high floating voltages caused by high number of modules limit multilevel converters in medium and high voltage applications, since all of them are not suitable to provide isolation to each module. To offer a solution, this paper presents a novel multi-modular converter that provides multiple isolated modules connected in series through low frequency transformers to operate at medium voltage levels. This topology is able to achieve the power balancing between the connected modules and independently adjust the dc voltage of each module by means of controlling a circulating current which flows through the arms. Furthermore, the topology implemented in photovoltaic renewable energy systems and the control strategy required to regulate the circulating and the output current are presented. The main principle behind this concept and the performance of the converter are evaluated and validated through simulation and experimental results.Peer ReviewedPostprint (author's final draft

Catalase as a Molecular Target for Male Infertility Diagnosis and Monitoring: An Overview

Catalase (CAT) stands out as one of the most efficient natural enzymes when catalysing the split of H2O2 into H2O and O2; H2O2 is one of the reactive oxygen species (ROS) involved in oxidative stress, a process closely related to aging and several health disorders or diseases like male infertility. Some studies have correlated H2O2 with male infertility and catalase with fertility restoration. However, the number of studies conducted with human beings remains scarce. Considering the use of CAT as a molecular target for biochemical analysis, this review summarises the current knowledge on how CAT influences human beings’ male fertility. Thus, three different databases were consulted—Scopus, PubMed and WOS—using single keywords and combinations thereof. A total of 40,823 articles were identified. Adopting inclusion and exclusion criteria, a final database of 197 articles served to conduct this work. It follows from this analysis that CAT could play an important role in male fertility and could become a good target for male infertility diagnosis and monitoring. However, that potential role of CAT as a tool in diagnosis must be confirmed by clinical trials. Finally, guidelines are suggested to reinforce the use of CAT in daily clinical tests for male fertility diagnosis and monitoring.This research was funded by the Human Fertility Chair, the Department of Biotechnology (VIGROB-186) and the Applied Biochemistry research group of the University of Alicante (VIGROB-309)

IZUMO1 Receptor Localization during Hyaluronic Acid Selection in Human Spermatozoa

IZUMO1 is an acrosome transmembrane protein implicated in the adhesion and fusion of gametes. This study aims to describe the distribution of IZUMO1 in human sperm under different physiological conditions: before capacitation (NCS), at one-hour capacitation (CS1), after a hyaluronic acid (HA) selection test (mature, MS1 and immature, IS1), and induced acrosome reaction from one-hour-capacitated sperm (ARS1). The data obtained in NCS, CS1, and MS1 significantly highlight dotted fluorescence in the acrosomal region (P1) as the major staining pattern (~70%). Moreover, we describe a new distribution pattern (P2) with a dotted acrosomal region and a labelled equatorial region that significantly increases in HA-bound spermatozoa, suggesting the onset of the migration of IZUMO1. In contrast, unbound spermatozoa presented an increase in P3 (equatorial region labelled) and P4 (not labelled). Finally, costaining to observe IZUMO1 distribution and acrosome status was performed in ARS1. Interestingly, we reported a variety of combinations between the IZUMO1 staining patterns and the acrosomal stages. In conclusion, these data show as a novelty the diffusion of the IZUMO1 protein during different physiological conditions that could contribute to the improvement in sperm selection techniques.This research was funded by Ministerio de Ciencia e Innovación (PID2021-123091NB-C22) and by Universidad de Alicante (VIGROB-186)

Análisis de prefactibilidad, evaluación técnica y económica en la implementación de un biodigestor común en viviendas sociales para la generación de energía y propuesta de utilización de ésta

77 p.El cambio climático y la contaminación son dos de las tres grandes crisis que afectan actualmente a todo el planeta, Chile es uno de los países afectados por estos cambios, su vez responsable de este problema global, dado su gran consumo de energía no renovable como es el uso indiscriminado de combustibles fósiles y productos derivados del petróleo, a esto se le suma la gran cantidad de desechos que nuestro país produce anualmente, especialmente de tipo orgánicos. Por lo mencionado anteriormente es que existe la necesidad de buscar energías alternativas renovables no convencionales que aminoren principalmente el impacto ambiental y también que ayude a la economía de las personas reemplazando los combustibles que hoy en día han presentado un alza exponencial. El presente trabajo trata esta problemática y como solución la idea de implementar un biodigestor común en viviendas sociales, con la finalidad de reducir los desechos orgánicos que son tirados a la basura y estos sean utilizándolos como biomasa, para la producción de biogás, aprovechándolo posteriormente para calefacción o en electricidad, además de generar una conciencia ambiental y aportar al cuidado del medio ambiente mediante el reciclaje de desechos orgánicos. Esta investigación se basó en analizar y determinar la prefactibilidad del dispositivo ya que normalmente los biodigestores se encuentran en el sector rural y utilizan como materia prima estiércol de ganado, sin embargo, estudios aseguraron que se puede utilizar residuo vegetal, se experimentó con residuo solido urbano orgánico o basura de cocina con excrementos de mascota dando resultados aceptables demostrando de forma práctica que es viable la producción de biogás. Se diseñó y analizó un digestor para ser evaluado técnica y económicamente resultando en un proyecto bastante viable sobre todo constructivamente, siendo una construcción e instalación simple y de bajo costo, no obstante, el transporte de biogás se limitó a una conducción por tubería desde el biodigestor a los hogares a una distancia menor a 100 metros descartando la posibilidad de almacenamiento y transporte en balones que normalmente se utilizan en el gas licuado, además de proponer la utilización de este en algún espacio comunitario del grupo habitacional social, que podría ser centro social, jardín infantil, junta de vecino entre algunos. Finalmente, producto de la biodigestión queda un excedente llamado biol que es un fertilizante mejorado y acondicionador de suelos teniendo una gran variedad de usos agrícolas dándole un valor agregado a este sistema

Sperm Adhesion Molecule 1 (SPAM1) Distribution in Selected Human Sperm by Hyaluronic Acid Test

The failures of binding to the oocyte zona pellucida are commonly attributed to defects in the sperm recognition, adhesion, and fusion molecules. SPAM1 (sperm adhesion molecule 1) is a hyaluronidase implicated in the dispersion of the cumulus-oocyte matrix. Therefore, the aim of this study was to characterize the SPAM1 distribution in the different physiological conditions of human sperm. Specifically, we evaluated the location of the SPAM1 protein in human sperm before capacitation, at one and four hours of capacitation and after hyaluronic acid (HA) selection test by fluorescence microscopy. Sperm bound to HA were considered mature and those that crossed it immature. Our results detected three SPAM1 fluorescent patterns: label throughout the head (P1), equatorial segment with acrosomal faith label (P2), and postacrosomal label (P3). The data obtained after recovering the mature sperm by the HA selection significantly (p < 0.05) highlighted the P1 in both capacitation times, being 79.74 and 81.48% after one hour and four hours, respectively. Thus, the HA test identified that human sperm require the presence of SPAM1 throughout the sperm head (P1) to properly contact the cumulus-oocyte matrix. Overall, our results provide novel insights into the physiological basis of sperm capacitation and could contribute to the improvement of selection techniques.This research was funded by the Cátedra Human Fertility, Departamento de Biotecnología of the Universidad de Alicante (VIGROB-186) and «Proyectos de Generación de Conocimiento» within the framework of the State Program to Promote Scientific-Technical Research and its Transfer, of the State Plan for Scientific, Technical and Innovation Research 2017–2020 (PGC2018-094781-B-I00)