Search results for "THD"

A reexamination of voltage distortion for classical carrier-based vs B-Spline modulation of three-phase Voltage Sources Inverters

2015

Voltage waveform improvement has been the object of several investigations for many years and a manifold of different solutions have been proposed to reduce the harmonic content in Voltage Source Inverters (VSI) power application. In many cases this improvements have been obtained by modifying the reference voltage modulating signal. The recent introduction of cardinal B-spline functions, used as carrier signals, has given rise to a new modulation technique whose main characteristic is a lower value of the Total Harmonic Distortion (THD). After the discussion on the B-Spline modulation principle and on its computational effort, a performance comparisons is carried out by means of Total Harm…

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 …

Mixed Harmonic Elimination Control for a Single-Phase 9 Level Grid-Connected Inverter

2018

The power quality requirements are increasingly stringent, due to the continuous growth of devices connected to the grid that introduce harmonics. These devices include DC to AC energy conversion systems, i.e. grid connected inverters. The design, control and operation of these systems must take into account the rules of interconnection to the electricity grid. To improve the quality of the output waveform of the grid-connected inverter, Multilevel Converters (MC) with selective harmonic elimination modulation technique can be used. This paper presents a single-phase nine level grid-connected inverter with DC/DC input stages. The obtained switching angles for THD minimization are independen…

Assessment and treatment of the withdrawal syndrome in paediatric intensive care units

2020

Background: Sedoanalgesia secondary iatrogenic withdrawal syndrome (IWS) in paediatric intensive units is frequent and its assessment is complex. Therapies are heterogeneous, and there is currently no gold standard method for diagnosis. In addition, the assessment scales validated in children are scarce. This paper aims to identify and describe both the paediatric diagnostic and assessment tools for the IWS and the treatments for the IWS in critically ill paediatric patients. Methods: A systematic review was conducted according to the PRISMA guidelines. This review included descriptive and observational studies published since 2000 that analyzed paediatric scales for the evaluation of the i…

Adjusting to Climate Change: Implications of Increased Variability and Asymmetric Adjustment Costs for Investment in Water Reserves

1997

Abstract In this paper we study the determination of optimal water storage capacity in a region, taking into account that the supply of the resource, the flow into the reserve, is uncertain, that a measure of the uncertainty, the variance, is likely to increase with climate change, that building capacity is costly, and that the development of water resources may entail alsoenvironmental costs. We find that water storage capacity in the long run ispositivelyrelated to increases in uncertainty if the marginal benefit of water withdrawal isconvexand that, for the case of costly reversibility of investment, a range of inaction for investment appears, and the stability of water storage capacity …

Il bias di ragionamento probabilistico nel birthday-problem. Un contributo di ricerca

Sepsis in head and neck cancer patients treated with chemotherapy and radiation: literature review and consensus

2015

Abstract: The reporting of infection/sepsis in chemo/radiation-treated head and neck cancer patients is sparse and the problem is underestimated. A multidisciplinary group of head and neck cancer specialists from Italy met with the aim of reaching a consensus on a clinical definition and management of infections and sepsis. The Delphi appropriateness method was used for this consensus. External expert reviewers then evaluated the conclusions carefully according to their area of expertise. The paper contains seven clusters of statements about the clinical definition and management of infections and sepsis in head and neck cancer patients, which had a consensus. Furthermore, it offers a revie…

DYSPHORIC-LIKE BEHAVIOUR DURING ETHANOL WITHDRAWAL IN FEMALE RATS. EFFECT OF CONTINUOUS VS INTERMITTENT ACCESS PARADIGM.

2014

Women show higher vulnerability for neuroadaptation to alcohol, which may contribute to negative emotional state during withdrawal (Sharrett-Field et al., 2013; Koob and Le Moal, 1997). This study aimed at exploring the effects of different patterns of voluntary ethanol consumption on female rat"s affective behaviour during withdrawal. Female rats underwent 12-week-, 2-bottle choice- continuous or intermittent (3 days/week ) access to 20% ethanol and were respectively named CARs and IARs. They were tested for alcohol preference; dysphoric-like state during withdrawal (24-48h); depressive- and anhedonic-like behaviours explored by forced swim- and saccharin preference tests; anxiety-like beh…

Substituent effects in nitro derivatives of carbazoles investigated by comparison of low-temperature crystallographic studies with density functional…

2014

The crystal structure of 9H-carbazole, C12H9N, (I), has been redetermined at low temperature for use as a reference structure in a comparative study with the structures of 1-nitro-9H-carbazole, C12H8N2O2, (II), and 9-nitrocarbazole, C12H8N2O2, (III). The molecule of (I) has crystallographically imposed mirror symmetry (Z′ = 0.5). All three solid-state structures are slightly nonplanar, the dihedral angles between the planes of the arene and pyrrole rings ranging from 0.40 (7)° in (III) to 1.82 (18)° in (II). Nevertheless, a density functional theory (DFT) study predicts completely planar conformations for the isolated molecules. To estimate the influence of nitro-group substitution on aroma…