High- and Low-Voltage Mitigation in Distribution Systems Using Residential Static Volt-Ampere Reactive Compensators

Power distribution systems are experiencing a fast transformation from simple one-way radial feeders to complex systems with multiple sources and bidirectional power flows. The rapid increase of Distributed Generation (DG) connected to the distribution system over the last decade, especially solar photovoltaic (PV), has been the key element to this transformation. The variable nature of PV-based DG has increased the complexity of voltage regulation in distribution systems. Electric Utilities are facing an increasing number of voltage issues in distribution systems with high penetration of DGs, leading customers to experience voltage levels outside of range A of the ANSI C84.1 standard. Electric Utilities have to expend resources, both human and economic, to mitigate the voltage issues caused by the interconnection of DG. The economic impact of voltage issues can be considerable in some cases. Conventional methods to mitigate voltage issues in distribution systems, such as the addition of voltage regulators and capacitor banks, could be ineffective in mitigating localized voltage issues caused by high levels of DG penetration. Other mitigation options, such as increasing the conductor size and the operating voltage of the feeder, are expensive. There is a clear need in the industry to locally solve voltage issues economically. In this dissertation, a new device, a Residential Static Volt-Ampere Reactive Compensator (RSVC), is proposed. The RSVC is used to mitigate low and high voltage issues by deploying them in a feeder with a high DG penetration level. This dissertation will investigate the interaction between solar inverters, voltage regulators and capacitor banks with the proposed RSVC. In order to reduce the number of buses to be analysed, the use of loss sensitivity factors will determine the candidate buses to host a RSVC. The results of this dissertation show that the use of RSVCs is able to mitigate low and high voltage conditions. Simulation results show that the RSVCs are able to control the voltage by absorbing and injecting reactive power according to the voltage seen at their terminals. Similar commercially available devices are not able to handle the injection and absorption of reactive power and are limited to handle either injection of reactive power or absorption of reactive power. The most common devices provide the capability of injecting reactive power

Construcción de un convertidor CC-CC tipo reductor orientado a la enseñanza

Luego de tener claro el objetivo de lo que se iba a desarrollar, se recopiló información para fortalecer la teoría del proyecto, con esta se pasó a diseñar el circuito Buck matemáticamente teniendo en cuenta los parámetros fi nales deseados, con esto se hizo un proceso de validación mediante tomas de datos en los laboratorios y simulaciones las cuales arrojaron resultados satisfactorios. Tomando como referencia trabajos pasados se decidió cual era el driver más adecuado para manejar el convertidor el cual fue probado en el laboratorio dando los resultados esperados. Paralelamente se desarrolló el PWM para proporcionar la señal de entrada del driver y la salida del Buck. Finalmente se construyeron los circuitos impresos con los cuales se tomó datos y se compararon con los simulados

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

Safety and effectiveness of propranolol in severely burned patients: systematic review and meta-analysis

Background The objective of this systematic review was to determine the effectiveness and safety of propranolol compared to placebo or usual care for improving clinical relevant outcomes in severely burned patients (TBSA \u3e20%). Methods Relevant articles from randomized controlled trials were identified by a literature search in MEDLINE, EMBASE, and CENTRAL. We included trials involving patients with a severe burn (\u3e20% of total body surface area affected). Trials were eligible if they evaluated propranolol and compared to usual care or placebo. Two investigators independently assessed articles for inclusion and exclusion criteria and selected studies for the final analysis. We conducted a meta-analysis using a random-effects model. Results We included ten studies in our systematic review. These studies randomized a total of 1236 participants. There were no significant differences between propranolol and placebo with respect to mortality (RD −0.02 [95% CI −0.06 to 0.02]), sepsis (RD −0.03 [95% CI −0.09 to 0.04]), and the overall hospital stay (MD −0.37 [−4.52 to 3.78]). Propranolol-treated adults had a decrease in requirements of blood transfusions (MD −185.64 [95% CI −331.06 to −40.43]) and a decreased heart rate (MD −26.85 [95% CI −39.95 to −13.75]). Conclusions Our analysis indicates that there were no differences in mortality or sepsis in severely burned patients treated with propranolol compared with those who had usual care or placebo. However, the use of propranolol in these patients resulted in lower requirements of blood transfusion and lower values of heart rate. The evidence synthesized in this systematic review is limited to conclude that propranolol reduces the length of hospital stay among severely burned patients. Future trials should assess the impact of propranolol on clinically relevant outcomes such as mortality and adverse events

Influence of homeostatic mechanisms of bacterial growth and division on structural properties of biofilms. A computer simulation study

Bacterial growth and division generally occur by the process known as binary fission, in which the cells grow polarly until they divide into two daughter cells. Although this process is affected by factors that introduce stochastic variability in both growth rate and daughter cell length, the fact is that the size distribution in bacterial communities, also known as biofilm, remains stable over time. This suggests the existence of homeostatic mechanisms that contribute to maintaining a stable size distribution. Those known as sizer and adder stand out among these mechanisms whose relevance is not entirely determined. In this work, computer simulations using an agent-based model, are used to study the effect of these homeostatic mechanisms on the geometrical and structural properties of the developing biofilm, focusing on the early stages of its development. Also, it was examined the effect of linear or exponential dependence with the time of cellular growth on these properties. From our study, we deduce that these mechanisms do not have a noticeable impact on the properties studied, which could be due to the importance that stochastic factors play in the cell division and growth process. In addition, we discuss how competition between cell growth and diffusion is a key aspect in explaining the structure and geometry of developing bacterial colonies

Marcos legales para el acceso a la tierra en América Latina: una mirada comparativa en ocho países de la región

Durante la segunda mitad del siglo XX y la primera década del XXI, la mayoría de países de América Latina experimentaron grandes cambios políticos, sociales y culturales. Muchos de estos cambios implicaron cambios en el acceso a la tierra y el marco jurídic

La prevención de riesgos y la accidentabilidad laboral : aportaciones desde la psicología social

El accidente y la enfermedad profesional, son, sin duda alguna, dos de los problemas más graves y de mayor relevancia que tiene planteados aún hoy el mundo del trabajo y la sociedad en general, ya que implica altos y variados costes humanos. Ahora bien, la accidentabilidad laboral o la pérdida de la salud no es un problema exclusivo del trabajador y del empresario, sino que ha de ser responsabilidad de la sociedad en su conjunto, pues tanto los accidentes como la salud en el trabajo son temas centrales desde una perspectiva política, económica y social. Desde el punto de vista científico, las líneas de investigación que se han seguido, quizás hayan estado excesivamente dirigidas hacia la restauración o intervención, aunque en la actualidad parecen desplazarse hacia el campo de la prevención._____________________ Professional accidents and diseases are without any doubt two of the main problems in the labour world and the society in general, as it implies a great deal of human lives. Now, the workplace accident rate or the health loss is not simply a problem for employers or employees, it must also be the responsibility of the society as a whole, as both workplace accidents and health are political, economic and social topics. From a scientific point of view, the research approaches have mainly been focussed towards restoration and intervention. However, at present research is developing towards prevention

Análisis mineralógicos, petrográficos y geoquímicos confirman el origen hidrotermal de sedimentos metalíferos sobreyaciendo las peridotitas de Cerro Matoso, Colombia

This paper shows part of the Doctoral dissertation of the first author (A. Castrillón), who gratefully acknowledges a fellowship from Colciencias (National Doctorate, scholarship 647) and Universidad Nacional de Colombia. Isotope analyses were done in the Instituto Andaluz de Ciencias de la Tierra, Granada, Spain. The authors express their gratitude to Dr. Dario Barrero, for his comments, and to Dr. Brian Fry for his selfless collaboration and valuable contributions to isotope modeling, and thanks to Cerro Matoso. This work also was possible thanks to the support of Dr. Augusto Rodriguez and the Instituto de Geología and Instituto de Geofísica Ambiental from the Universidad Nacional Autónoma de México. Datasets for this research are included in this paper and supplementary information files can be found in. Castrillón, Andres (2020), “Open systems fractionation factor CM”, Mendeley Data, v1. https://doi.org/10.17632/8fr82mx34x.1#file- 51080efe-3098-4796-a5ae-384707ae2ddbThe Cerro Matoso deposit, one of the largest open-pit ferronickel mines in the world is formed by a sedimentary succession on top of an abducted ultramafic body that makes part of the Cauca ophiolite complex. The set of rocks was accreted in northwestern Colombia during the Cretaceous and exposed to weathering processes during the last Andean Orogeny. Sediment samples were collected and studied using petrographic microscopy, SEM, EPMA, ICP-MS, XRF, and oxygen as well as carbon isotopes analyses. Oxygen isotope results reflect pore-water temperatures reaching up to 130 degrees C during mineral precipitation, which are consistent with serpentinization-derived fluids of mantle rocks that may be related to deep-sea hydrothermal activity. Negative delta 13C values (-27.1 to -1 parts per thousand V-PDB) in bulk samples of the tabular succession correlate with the delta 13C range of methane from modern serpentinite-derived fluids. The REE/Fe data (ratio <0.4) suggest that sediments differenced in black mudstone and fossiliferous green claystone correspond to metalliferous and hydrothermal sediments respectively, formed in the ancient mid-ocean Pacific ridge, far west of its present position. Positive Eu and negative Ce anomalies registered in the black mudstone succession correlate with a hydrothermal plume scenario.El yacimiento Cerro Matoso, una de las minas de ferroníquel a cielo abierto más grandes del mundo, está formado por una sucesión sedimentaria que reposa sobre un cuerpo ultramáfico adosado al continente, que forma parte del Complejo Ofiolítico del Cauca. El conjunto de rocas fue adosado en el noroeste de Colombia durante el Cretácico, y fue expuesto a procesos de meteorización durante la última orogenia andina. Las muestras de sedimentos fueron recolectadas y estudiadas mediante microscopía petrográfica, SEM, EPMA, ICP-MS, FRX y análisis de isótopos de oxígeno y carbono. Los resultados de los isótopos de oxígeno reflejan temperaturas del agua intersticial que alcanzan los 130°C durante la precipitación mineral, lo que es coherente con fluidos derivados de la serpentinización de las rocas ultramáficas que pueden estar relacionados con actividad hidrotermal en el fondo del mar. Los valores negativos de δ13C (−27,1 a −1‰ V-PDB) en muestras (roca total) de la sucesión sedimentaria, se correlacionan con el rango de δ13C del metano de fluidos modernos derivados de serpentinita. Los datos REE/Fe (relación <0.4) sugieren que los sedimentos denominados lodolitas negras y arcillolitas verdes fosilíferas corresponden a sedimentos metalíferos e hidrotermales respectivamente, formados en la antigua dorsal meso-oceánica del océano Pacífico, muy al oeste de su posición actual. Las anomalías positivas de Eu y negativas de Ce registradas en la sucesión de lodolitas negras se correlacionan con un escenario de plumas hidrotermalesDepartamento Administrativo de Ciencia, Tecnologia e Innovacion Colciencias 64