Search results for " multilevel"
showing 10 items of 65 documents
Mathematical formulation of pulse amplitude modulation selective harmonic elimination in multilevel three phase inverters
2022
In this paper multilevel cascaded H-bridges (CHB) three phase inverters with 2n dc sources, n=1,2,3,... are considered and a mathematical formulation providing both 2n switching angles and dc voltage source to eliminate n+1 harmonics and their respective multiple from their output voltage waveform, is proposed. The computed angles don't depend on modulation index and the source voltages linearly vary with it. The proposed procedure finds the solution through an analytical formula that avoids to solve transcendental systems and presents very low computational cost. A lot of low order harmonics are eliminated, returning a very low total harmonic distortion (THD). Particularly for 9-level conf…
Experimental Comparative Analysis of Efficiency and THD for a Three-phase Five-level Cascaded H-Bridge Inverter Controlled by Several MC-PWM Schemes
2021
Cascaded H-Bridges Multilevel Inverters are an innovative and promising solution in different application fields. This topology allows obtaining an improvement in the performance (e.g. reduced harmonic content, the low voltage stress on power components, and high efficiency) in respect to the traditional two-level inverters. In this context, the Multicarrier-PWM strategies play an important role thanks to their features. This paper presents an experimental investigation on the performance of a three-phase five-level Cascaded H-Bridge inverter by using different PWM modulation strategies. In particular, the paper is focused on the experimental validation of the main features of Multicarrier …
L'ACCESSO ALL'ABITAZIONE DI RESIDENZA: UN'ANALISI MULTILEVEL SULLE FAMIGLIE ITALIANE
2010
Objectives. Income inequalities depend on a large range of components, which influence living conditions of private households. Not all these elements are strictly monetary, and non-monetary components sometimes can be even more important than monetary ones. While international literature has devoted considerable attention to the study of distribution, relevance and inequalities concerning monetary income, the same cannot be said for its non monetary components. Despite this lack of attention in the literature, non monetary components often influence dramatically living conditions of private households. One of the most important component of non-monetary income is imputed rents from owner-o…
Overview and experimental analysis of MC SPWM techniques for single-phase five level cascaded H-bridge FPGA controller-based
2016
This paper presents an overview and experimental analysis of the MC SPWM techniques for single-phase cascaded H-bridge inverter. The multilevel power converters are an alternative to traditional converters known as “three-level converters”. The voltage waveforms and the related frequency spectra, which have been obtained by simulation analysis in Matlab-Simulink environment, are here reported for all the proposed modulation techniques. The simulation results have been experimentally validated through means of a DC/AC, five-level, single-phase converter prototype with an appropriate test bench.
On Ignoring the Random Effects Assumption in Multilevel Models: Review, Critique, and Recommendations
2019
Entities such as individuals, teams, or organizations can vary systematically from one another. Researchers typically model such data using multilevel models, assuming that the random effects are uncorrelated with the regressors. Violating this testable assumption, which is often ignored, creates an endogeneity problem thus preventing causal interpretations. Focusing on two-level models, we explain how researchers can avoid this problem by including cluster means of the Level 1 explanatory variables as controls; we explain this point conceptually and with a large-scale simulation. We further show why the common practice of centering the predictor variables is mostly unnecessary. Moreover, …
Evolutionary Pathways of Political Representation in a Multi-Level Constitutional System: the Italian experience
2004
Il saggio cerca di studiare e individuare adeguati strumenti di raccordo e nuove forme di governance idonei ad assicuarare legittimità democratica ai sistemi politici complessi con particolare riferimento al sistema italiano profondamente mutato a seguito del processo di integrazione europea e dopo la riforma del titolo V della Costituzione italiana.
Challenges in dental statistics: data and modelling
2022
The aim of this work is to present the reflections and proposals derived from the first Workshop of the SISMEC STATDENT working group on statistical methods and applications in dentistry, held in Ancona (Italy) on 28th September 2011. STATDENT began as a forum of comparison and discussion for statisticians working in the field of dental research in order to suggest new and improve existing biostatistical and clinical epidemiological methods. During the meeting, we dealt with very important topics of statistical methodology for the analysis of dental data, covering the analysis of hierarchically structured and over-dispersed data, the issue of calibration and reproducibility, as well as some…
Factors Influencing Teachers’ Use of ICT in Class: Evidence from a Multilevel Logistic Model
2022
Information and Communication Technologies (ICTs) have become a key factor in the educational context, especially in the aftermath of the COVID-19 pandemic, and, correctly implemented, can help to improve academic performance. The aim of this research was to analyse the factors that influence teachers’ decisions to use ICT more- or less frequently to carry out tasks and exercises in their classes. To this end, we estimated a multilevel logistic model with census data from the individualized evaluation of students of the Community of Madrid (Spain) carried out at the end of the 2018–2019 academic year in primary and secondary education. Additionally, we applied multiple imputation techniques…
Between Self-Organizing and Accelerating Networks: Untangling the multilevel of strategic networks
2010
This paper aims to detect the crucial determinants and processes that shape the emergence and evolution of interfirm network cognitive morphology. We pinpoint three relatively distinct but coexistent levels which define the fundamental structure of the network: the microsystemic (or the single firm) level; the mesosystemic (or the groups of firms within the network) level; and the macrosystemic (or the overarching network) level. Then, we integrate the complex system perspective (Morin, 1977; Prigogine and Stengers, 1984; Anderson, 1999) applied to networks with studies regarding theoretical models that elucidate network structuring and dynamics cultivated in the new “science of networks” (…
Does taking additional Maths classes improve university performance?
2022
Several recent studies in educational literature showed how students’ skills in maths affect their success at higher levels of education. The aim of this paper is to evaluate the effect of taking additional maths class at high school on first-year performance of Italian university students. However, university performance and the choice of the high-school depend on several factors that make this evaluation challenging. Using information coming from three different sources, we carry out a multilevel propensity score procedure to estimate the average treatment effect between the applied sciences track and the traditional scientific one. After balancing for school- and student-level covariates…