Analysis of the power balance In the cells of a multilevel cascaded H-Bridge converter

Multilevel cascaded H-Bridge converters (CHB) have been presented as a good solution for high power applications. In this way, several control and modulation techniques have been proposed for this power converter topology. In this paper the steady state power balance in the cells of the single phase two cell CHB is studied. The capability to be supplied with active power from the grid or to deliver active power to the grid in each cell is analyzed according to the dc-link voltages and the desired ac output voltage value. Limits of the maximum and minimum input active power for stable operation of the CHB are addressed. Simulation results are shown to validate the presented analysis

Resumen de los actos de La Juventud Católica de Leon durante la interrupcion de sus tareas académicas (1874 á 1877.) : memoria leida en la solemne inaguracion del año académico de 1877-78

Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 2009-201

Impacto de la COVID-19 sobre la delincuencia vial en la ciudad de Villena (Alicante)

Con motivo de la pandemia de la COVID-19 se sufrió, tanto a nivel mundial como en España, una importante crisis en todos los ámbitos de la sociedad. Las medidas que se han tenido que tomar por parte de los distintos gobiernos han tenido un fuerte impacto en el comportamiento de los ciudadanos. Esta situación de excepcionalidad no sólo ha modificado las conductas y rutinas de la ciudadanía, también ha afectado a muchas actividades delictivas como la delincuencia vial. En esta investigación tendrá como objetivo investigar el impacto del confinamiento, impuesto por el gobierno, en la delincuencia vial en la ciudad de Villena. Este municipio se utilizará como muestra, analizando los datos recabados por su Cuerpo de Policía Local durante el periodo comprendido entre los años 2019 a 2022. Así pues, se plantean las hipótesis de que, por un lado, la pandemia por COVID-19 ha provocado el descenso de los delitos cometidos contra la seguridad vial en Villena, y por otro lado, que a pesar de las restricciones de circulación y desplazamientos causadas por la COVID-19, estos delitos se siguen cometiendo en las mismas franjas temporales.The COVID-19 pandemic caused a major crisis in all areas of society, both globally and in Spain. The measures that have had to be taken by the different governments have had a strong impact on the behaviour of citizens. This exceptional situation has not only modified the behaviour and routines of citizens, but has also affected many criminal activities such as road crime. The aim of this research will be to investigate the impact of government-imposed confinement on road crime in the city of Villena. This municipality will be used as a sample, analysing the data collected by its Local Police Force during the period from 2019 to 2022. Thus, it is hypothesised that, on the one hand, the COVID-19 pandemic has led to a decrease in road safety offences in Villena, and on the other hand, that despite the restrictions on traffic and travel caused by COVID-19, these offences continue to be committed in the same time periods

Risk Factors for Relapse in People with Severe Mental Disorders during the COVID-19 Pandemic: A Multicenter Retrospective Study

Background: Evidence suggests that different variables associated with the COVID-19 pandemic may increase the risk of relapse in people with Severe Mental Disorders (SMDs). However, no studies have yet looked closely at the different risk factors involved to determine their influence on the worsening of these patients’ illnesses. Objective: To analyze which variables related to the COVID-19 pandemic have increased the risk of relapse in patients with SMDs. Method: A multicenter retrospective cohort study in which data were collected from 270 patients with mental disorders who had been under follow-up in day hospitals during the year 2020. Results: The proportion of full mental health inpatient admissions was significantly higher in those who lost their employment (40.7% vs. 18.1%; p = 0.01), in those who were not receiving psychotherapy interventions (33.9% vs. 16.6%; p = 0.006), and in those who were not receiving occupational therapy (25.7% vs. 13.6%: p = 0.013). Significant associations were detected between urgent mental health consultations, the number of COVID-19 symptoms (B = 0.274; p = 0.02), and the low-income group (1.2424 vs. 0.4583; p = 0.018). Conclusions: COVID-19 symptoms and certain consequences of the pandemic, such as loss of employment, economic hardship, and loss of interventions, have brought about clinical worsening in people with SMDs. Knowledge of these factors is important for health-related decision-making in future outbreaks or pandemics

Diversity and novelty in environmental enrichment increases enrichment use in juvenile American mink (Neogale vison)

It is standard practice on mink farms in Canada to provide one manipulable environmental enrichment (EE) in each cage to benefit animal health and welfare, and once an enrichment is introduced, it must remain in the cage for the duration of that animal’s life. However, mink might habituate to permanently present enrichments, which reduces interaction with these items over time. In this study, juvenile mink were provided with multiple EEs (mobile and hanging items) that were regularly exchanged to maintain novelty in addition to a standard, permanently present EE (enriched kits; EK). EE use over time, as well as interactions based on EE type, were compared to that of two groups which were standard-housed as juveniles (control; C and enriched at whelping; EW) with access to a permanently available standard enrichment. EK housing was found to significantly increase kits’ EE use compared to standard housing (p< 0.001). Despite some evidence of rapid habituation to novel objects (e.g., decreased use of hanging rope EE in second week of access: p = 0.019), item exchange appeared to have a sustaining effect on exploration of all EEs in the cage, including familiar objects. Thus, it may be beneficial to provide farmed mink with multiple EEs, both novel and familiar, to promote their optimal use and facilitate welfare benefits. Objects with greater manipulability or malleability were also used more by kits than those with fewer possible uses (e.g., pig’s ear versus other, less malleable mobile EEs: p< 0.001; rope versus less malleable hanging EE: p< 0.001). Although this effect was persistent across all periods of observation, it is possible that kit age at time of object introduction or differences in novelty may have contributed to these differences in their use. Further research is required to determine kits’ preference for different EE types when all items are equivalently novel, and when differences in developmental stage are fully accounted for

A Model-Based Direct Power Control for Three-Phase Power Converters

Direct Power Control (DPC) technique has been widely used as control strategy for three-phase power rectifiers due to its simplicity and good performance. The DPC uses the instantaneous active and reactive power to control the power converter, the controller design has been proposed as a direct control with a look up table (LUT), and in recent works, as an indirect control with an inner control loop with proportional plus integral controllers for the instantaneous active and reactive power errors. In this paper a model-based DPC for three-phase power converters is designed, obtaining expressions for the input control signal which allow to design an adaptive control law minimizing the errors introduced by the parameters uncertainties as the smoothing inductor value or the grid frequency. Controller design process, stability study of the system and experimental results for a synchronous three-phase power rectifier prototype are presented to validate the proposed controller

Control del Equilibrio de las Tensiones de los Condensadores Flotantes en Convertidores Multinivel de Capacidades Flotantes

SEMINARIO ANUAL DE AUTOMATICA, ELECTRONICA INDUSTRIAL E INSTRUMENTACION () (.2006.GIJON)Los convertidores de capacidades flotantes multinivel se presentan como una alternativa a otro tipo de topologías multinivel presentando ciertas ventajas. Sin embargo, presentan desventajas como el desequilibrio de tensiones de los condensadores flotantes introduciendo distorsión en las tensiones moduladas por el convertidor. Se presenta en este trabajo un algoritmo para controlar el equilibrio de estas tensiones. Este algoritmo se basa en la elección de los estados de los transistores dentro de la secuencia de conmutación usando modulación Space Vector. Este algoritmo es completamente general siendo aplicable a cualquier número de niveles e independiente de la carga. Se presentan todas las expresiones matemáticas necesarias para el control mostrándose resultados de simulación para demostrar el buen funcionamiento de la estrategia de control propuesta. Se muestran los límites de controlabilidad del algoritmo comparándolo con los límites obtenidos para otras topologías de convertidores multinivel

Generalized analytical approach of the calculation of the harmonic effects of single phase multilevel PWM inverters

This paper introduces a generalized analytical approach for calculating the total harmonic distortion THD and its weighted value WTHD for multilevel PWM inverters. The calculation considers one single phase and it can apply to any number of levels of the inverter in general. Although the analysis is based on the assumption of a high number of pulses, the developed equations can also be applied for lower frequency ratios fs/f1. The analytical formulas require the characteristic parameters of the PWM only, which are the modulation factor m, the switching frequency fs, the fundamental frequency f1, the effective inductance L and the DC link voltage inverters with a number of levels N are considered. It must be noticed that some differences appear between the case of N odd and N even. Several parametric curves arc calculated to define the specifications of an inverter with N levels in order to fulfill the harmonic voltage recommendations trying to reduce the output signal filtering