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

Expresión de E-cadherina, laminina y colágeno IV en la evolución de displasia a carcinoma epidermoide oral

Objetivos: Estudiar la pérdida o reducción de la adhesión celular mediada por E-cadherina en leucoplasias, carcinomas epidermoides y metástasis ganglionares. Estudiar la pérdida de continuidad de la expresión de laminina y colágeno IV en la membrana basal epitelial en el desarrollo biológico de las leucoplasias y carcinomas orales. Material y metodo: Hemos estudiado 124 muestras de pacientes portadores de leucoplasias y carcinomas orales con diversos diagnósticos que abarcan desde epitelio normal (13 muestras), displasias leves (2), displasias moderadas (12), carcinomas in situ (13) carcinomas microinvasores (11) Carcinoma epidermoide oral (64 muestras) y metástasis ganglionar (9). Se construyeron 7 bloques de tissue microarrays con aguja de 2mm y se realizó un estudio mediante técnica inmunohistoquímica para E-cadherina (clona 36, T.D. ABD Company), Laminina (078P, Biogenex) y Colágeno IV (PHM12, Biogenex). Resultados: En Displasias Leves y Moderadas presentan pérdida de expresión de E-cadherina, Laminina, y Colágeno IV (20%). En Carcinomas in situ y Microinvasores, presentaron pérdida de expresión de E-cadherina (73%), y en Laminina y Colágeno IV (57%). En los carcinomas epidermoides, encontramos pérdida de expresión de E-cadherina (90%) y discontinuidad en la M. basal (70%). Todas las metástasis ganglionares presentaron pérdida de E-cadherina y discontinuidad en Laminina y Colágeno IV. Conclusiones: La pérdida de expresión de E-cadherina se incrementa al aumentar el grado de displasia de las lesiones. La perdida de continuidad en la expresión de laminina y Colágeno IV sigue una evolución paralela desde displasias a metástasis ganglionares. La disminución en la expresión de los tres marcadores ha sido significativa en la evolución de las lesiones orales.Objectives: Study the loss or reduction of the cellular adhesion mediated for E-cadherin in oral leukoplakias, oral squamous cell carcinomas and metastatic nodules. Study the loss of continuity of the laminin and collagen IV expression in the epithelial basal membrane from the biological development of the oral leukoplakias and oral carcinomas. Material and method: we have studied 124 samples of patient payees leukoplakias and oral carcinomas with diverse diagnosis that embrace from normal epithelium (13 samples), mild dysplasias (2), moderate dysplasias (12), 'in situ' carcinomas (13), microinvasive carcinomas (11) oral squamous cell carcinomas (64 samples) and metastatic nodules (9). 7 blocks of tissue microarrays were built with needle of 2mm and was carried out a study by means of immunohistochemical technique for E-cadherin (clone 36, Biogenex), Laminin (078P, Biogenex) and Collagen IV (PHM12, Biogenex). Results: In Mild and Moderate Dysplasias the results present loss of E-cadherin, Laminin, and Collagen IV (20%) expression. 'in situ' and microinvasive carcinomas, the results presented loss of E-cadherin expression (73%), and loss in Laminin and Collagen IV expression (57%). In the squamous cell carcinomas , we find E-cadherin underexpression (90%) and discontinuity in the Basal Membrane. (70%). All the metastatic nodules presented loss of E-cadherin expression and discontinuity in Laminin and Collagen IV expression. Conclusions: The loss of E-cadherin expression is increased when increasing the dysplasia grade of lesions. The loss of continuity in the laminin and Collagen IV expression follow a parallel evolution from dysplasias to metastatic nodules. The underexpression of the three markers has been significant in the evolution of the oral lesions

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

COMPARACIÓN DE DIFERENTES PROTOCOLOS DE SINCRONIZACIÓN PARA INSEMINACIÓN ARTIFICIAL A TIEMPO FIJO EN CERDAS NULÍPARAS: RESULTADOS PRELIMINARES

A total of 15 gilts (150 ± 14.6 kg) were randomly assigned to three treatments: 1) AN: addition of 20 mg altrenogest (Virbagest, progesterone) to the diet for 18 days; 2) ANH: similar to AN plus 10.5 µg of GnRH and 500 IU of hCG 24 and 96 hours, respectively, after the last application of progesterone; and 3) PL: six intramuscular injections of 600 mg progesterone (Proluten) at 72-hour intervals plus 10.5 µg of GnRH and 500 IU hCG 48 and 120 hours, respectively, after the last progesterone injection. Two IATFs were performed, one at 26 hours and another at 40 hours after hCG application. Although no significant differences were evident in the pregnancy rate (p>0.05), the sows synchronized with AN had, numerically, a 20% higher pregnancy rate compared to the other treatments. A reduction in the onset of estrus was obtained in the synchronized sows with ANH and PL compared to those synchronized with AN (p<0.05). The PL treatment was $20.65 and$21.93 cheaper than the AN and ANH treatments, respectively. In conclusion, the application of the PL protocol had a similar pregnancy rate and onset of heat than the ANH group, as well as a lower application cost per sow.Un total de 15 cerdas nulíparas cruzadas (150±14.6 kg) se asignaron al azar a tres tratamientos: 1)         AN: adición de 20 mg de altrenogest (Virbagest, progesterona) en la dieta durante 18 días; 2) ANH: similar a AN más 10.5 µg de GnRH y 500 UI de hCG 24 y 96 horas, respectivamente, luego de la última aplicación de progesterona; y 3) PL: seis inyecciones intramusculares de 600 mg de progesterona con intervalos de 72 horas, más 10.5 µg de GnRH y 500 UI de hCG 48 y 120 horas, respectivamente, luego de la última inyección de progesterona. Se realizaron dos IATF, una a las 26 horas y otra a las 40 horas después de la aplicación de hCG. A pesar de que no se evidenció diferencias significativas en la tasa de preñez (p>0.05), las cerdas sincronizadas con AN tuvieron, numéricamente, una tasa de preñez de 20% mayor en comparación a los demás tratamientos. Se obtuvo una reducción en el inicio del estro en las cerdas sincronizadas con el tratamiento ANH y PL en comparación con las cerdas del grupo AN (p< 0.05). Los tratamientos AN y ANH fueron de mayor costo por $20.65 y$21.93 que el tratamiento PL. En conclusión, la aplicación del protocolo PL tuvo similar tasa de preñez y similar intervalo de inicio del estro que el grupo ANH, como también un menor costo de aplicación por cerda

Propiedades mecánicas del acero de refuerzo utilizado en Colombia

Results of the statistical analysis applied to the experimental study that determine the mechanical properties of Colombian steels subjected to monotonic tensile loads are presented. Typical stress-strain curves are obtained that allow characterizing national steels studied by emphasizing the variables that determine the change in material behaviorSe presentan resultados del análisis estadístico aplicado al estudio experimental que de- termina las propiedades mecánicas de aceros colombianos sometidos a cargas monotónicas de tracción. Se obtienen curvas típicas de esfuerzo-deformación que permiten caracterizar aceros nacionales estudiados haciendo énfasis en las variables que determinan el cambio de comportamiento del materia

La Hora TutHora: una herramienta de ordenación académica para incrementar la acción tutorial en la Escuela Universitaria de Ingeniería Técnica Industrial de la UPM

La reciente puesta en marcha de las titulaciones adaptadas al RD 1393/2007 constituía la oportunidad largamente esperada de implementar una serie de proyectos ilusionantes asociados a la Declaración de Bolonia y a su “nebulosa”. Entre ellos, la mejora del rendimiento en la Acción Tutorial constituye, para la UPM, uno de los aspectos prioritarios. En ese ámbito, la E.U. de Ingeniería Técnica Industrial ha desarrollado, desde el curso 2010/2011, un proyecto denominado “La Hora TutHora”, cuyo objetivo consiste en actuar desde Ordenación Académica para favorecer la mencionada Acción Tutorial. Este artículo expone los resultados que han podido medirse tras un año de vida del proyecto

Propiedades mecánicas del acero de refuerzo utilizado en Colombia

A statistical analysis applied to a experimental study that determines the mechanical properties of steels produced in Colombia subjected to monotonic loads of tension is presented. Typical stress-strain diagram that allow to characterize these steels making emphasis in the variables that determine the change of behaviour of the materia are presented.PACS: 62.20.-xSe presentan resultados del análisis estadístico aplicado al estudio experimental que de- termina las propiedades mecánicas de aceros colombianos sometidos a cargas monotónicas de tracción. Se obtienen curvas típicas de esfuerzo-deformación que permiten caracterizar aceros nacionales estudiados haciendo énfasis en las variables que determinan el cambio de comportamiento del materialPACS: 62.20.-

La Acción Tutorial incentivada durante los dos últimos cursos académicos con el proyecto de "La Hora Tuthora"

La puesta en marcha de las titulaciones adaptadas al RD 1393/2007 constituía la oportunidad largamente esperada de implementar una serie de proyectos ilusionantes asociados a la Declaración de Bolonia y a su “nebulosa”. Entre ellos, la mejora del rendimiento en la Acción Tutorial constituye, para la UPM, uno de los aspectos prioritarios. En ese ámbito, la E.U. de Ingeniería Técnica Industrial ha desarrollado, desde el curso 2010/2011, un proyecto denominado “La Hora TutHora”, cuyo objetivo consiste en actuar desde Ordenación Académica para favorecer la mencionada Acción Tutorial. Este artículo expone los resultados que han podido medirse tras dos años de vida del proyecto, las conclusiones que pueden obtenerse y el planteamiento de propuestas de mejora