Search results for "Volt"
showing 10 items of 2187 documents
Reconfigurable electrical interconnection strategies for photovoltaic arrays: A review
2014
Non-uniform irradiance significantly decreases the power delivered by solar photovoltaic arrays. A promising technique for compensating these power losses relies on dynamically reconfiguring the electrical connections between photovoltaic modules. This paper presents the current state-of-the-art strategies for photovoltaic array reconfiguration in order to increase the power output under partial shading and mismatch conditions. The different approaches have been compared in terms of effectiveness of the control algorithms, monitored electrical and environmental variables, overall hardware complexity and specific features of each solution. Finally, the most challenging aspects of the reconfi…
A study on the use of bare buried conductors in an extended interconnection of earthing systems inside a MV network
2005
In the field of electrical safety an important topic is the transmission of voltages, during an earth fault, inside an extended interconnection of local earthing systems. The paper presents a study, with reference to the MV networks, about those systems where the interconnection between the earth electrodes of the electrical installations is carried out using bare buried conductors. Starting from the description of the circuital model of a bare buried conductor interconnecting together the earth electrodes of two MV/lv substations, the mathematical model of the whole interconnected earthing system is found. Finally, the results of some simulations, giving the distribution of the fault curre…
Primary Frequency Control in the Power System of Continental Europe including the Dynamics of the HVDC Link France-Great Britain
2020
The paper presents a study of primary frequency control within the power system of Continental Europe (CE) including the dynamics of the high voltage direct current (HVDC) link between France and Great Britain (GB). The large-scale dynamic model of the CE system originally provided by ENTSO-E is extended with a more detailed representation of the whole HVDC interconnection. The dynamics of the GB synchronous area is also considered in the analysis, implementing a system equivalent suitable for primary frequency control studies. The opportunity of frequency containment reserve exchange between the two areas through the link is also investigated, considering supplementary frequency controls w…
Removing Leakage and Surface Recombination in Planar Perovskite Solar Cells
2019
Thin-film solar cells suffer from various types of recombination, of which leakage current usually dominates at lower voltages. Herein, we demonstrate first a three-order reduction of the shunt loss mechanism in planar methylammonium lead iodide perovskite solar cells by replacing the commonly used hole transport layer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with a better hole-selective polyarylamine. As a result, these cells exhibit superior operation under reduced light conditions, which we demonstrate for the extreme case of moonlight irradiance, at which open-circuit voltages of 530 mV can still be obtained. By the shunt removal we also observe the VOC to dro…
Electrochemical characterization of iron sites in ex-framework FeZSM-5
2002
Abstract The electrochemical response of FeZSM-5 prepared by an ex-framework method has been studied using Paraloid B72 polymer film electrodes immersed in aqueous media using H2SO4, HCl, Na2EDTA and NaCl electrolytes. The ex-framework method comprises the hydrothermal synthesis of isomorphously substituted FeZSM-5, followed by calcination at 823 K and subsequent steam treatment (300 mbar H2O in N2) at 873 K. During this process iron is extracted to extra-framework positions. Also partial dealumination of the zeolite framework takes place. Characteristic voltammetric responses in the +1.0 to −0.6 V versus SCE potential range have been recorded and were used to characterize the iron species …
N-heterocyclic carbenes and parent cations: acidity, nucleophilicity, stability, and hydrogen bonding-Electrochemical Study and ab initio calculations
2016
N-Heterocyclic carbenes (NHCs) are widely used as organocatalysts. Their reactivity (and instability) is related to their basicity and nucleophilicity, which, in turn, are linked to their scaffold. NHCs can be generated by chemical deprotonation or electrochemical reduction of the parent azolium cations, NHCH+s. Cyclic voltammetry enabled the reduction potential of the NHCH+s to be determined; the reduction potential is related to the acidity of the NHCH+s and the oxidation potential of the NHCs, which is related to the nucleophilicity of the NHCs. It was thus possible to order different NHCH+s and NHCs by their acidity and nucleophilicity, respectively. A study on the stability of NHCs was…
Sustainable technologies for greenhouse systems
2020
The greenhouse cultivation system in European countries represents one of the most energy-intensive sectors in the agriculture and agro-industry sector. In this regard, renewable energies represent an innovative solution to reduce energy costs and environmental impacts. Both, the energy demands and the economic aspects are analyzed with regard to the main energy users, i.e.: heating and cooling systems, lighting and pumping for irrigation. This work considers the use of solar photovoltaic and thermal energy. The use of semi-closed greenhouses is also considered.
Redox tuning and species distribution in Maya Blue-type materials: a reassessment.
2013
Maya Blue-type specimens prepared from indigo (1 wt %) plus kaolinite, montmorillonite, palygorskite, sepiolite, and silicalite are studied. Liquid chromatography with diode array detection, ultra-performance liquid chromatography coupled with mass spectrometry, and pyrolysis-silylation gas chromatography-mass spectrometry analyses of the extracts from these specimens combined with spectral and solid-state voltammetry, electrochemical impedance spectroscopy, and scanning electrochemical microscopy techniques provide evidence for the presence of a significant amount of dehydroindigo and isatin accompanying indigo and other minority organic compounds in all samples. Solid-state electrochemist…
A Simulation Analysis of VSM Control for RES plants in a Small Mediterranean Island
2020
The paper presents an application of Virtual Synchronous Machine control for managing inverter-interfaced renewable energy sources in a small Mediterranean island not supplied by the main grid. In the proposed analysis, the island's renewables-based generators area assumed interfaced to the grid by voltage source converters with a swing controller and a vector-current controller with two different options for the reference current for regulating the voltage at the Point of Common Coupling and the active power output. The system, modeled in PScad environment, allows to verify the response of the renewables-based generators with VSM control in the presence of a fault in the grid.
A backward sweep method for power flow solution in distribution networks
2010
Abstract A methodology for the analysis of radial or weakly meshed distribution systems supplying voltage dependent loads is here developed. The solution process is iterative and, at each step, loads are simulated by means of impedances. Therefore, at each iteration, it is necessary to solve a network made up only of impedances; for this kind of network, all the voltages and currents can be expressed as linear functions of a single unknown current (in radial systems) or of two unknown currents for each independent mesh (for meshed systems). The methodology has been called “backward” since the unique equation, in case of radial network, and the linear system of equations, in case of meshed n…