1,721,149 research outputs found
SISTEMI IBRIDI PER L'ALIMENTAZIONE DI UTENTI RESIDENZIALI: DISPACCIAMENTO MULTIOBIETTIVO RETE/FOTOVOLTAICO
No full textTESI DI DOTTORATO IN INGEGNERIA ELETTRIC
PROCEDURE DI MISURA PER OTTENERE LE CARATTERISTICHE CORRENTE-TENSIONE DELLE CELLE SOLARI DI UN MODULO FOTOVOLTAICO
No full textMonitoring and checking of performance in photovoltaic plants: A tool for design, installation and maintenance of grid-connected systems
No full textThis work represents the Photovoltaic section of the European Project PERSIL, which includes also the study of solar thermal plants. The activity is twofold: the results of 1-year monitoring and checking of thirteen PV systems; the consequent guidelines for the design, installation and maintenance of grid connected PV systems. For accurate estimation of the energy production a two-year analysis of solar radiation has been conducted on the basis of pyranometer measurements in all the Project locations. The checking of energy performance has been carried out by a suitable improvement of a conventional method, that includes the assessment of the energy availability. The corresponding results are excellent for three PV plants, whereas they are strongly negative for five old PV plants which exhibit poor availability (62-78%). The remaining plants behave with acceptable performance ratios (0.65-0.78). Within the guidelines for design, the optimum coupling array/inverter and the related protections have been discussed in detail. About the guidelines for installation, the PV module/inverter cooling, the electric cables and enclosures have been dealt with. Then, concerning the guidelines for maintenance, the main items are the energy production assessment, the glass dirt checking and the maintenance of motors in sun-trackers. Finally, all these guidelines help to maximize the energy availabilit
Electric power distribution and environment: interference of power installation magnetic fields on computer systems
No full textThe present study analyzes the electromagnetic interference produced on visual display units (VDUs) in domestic and industrial environments. The main sources of disturbance may be identified in three-phase lines, unbalanced currents, currents in earthing systems, proximity of power installations, proximity of railway tracks, and presence of harmonics on the neutral conductor. Magnetic-field interference for PCs is practically limited to the deflection of the cathode-ray tube (CRT) electron beam. The vertical magnetic field determines a horizontal electron beam motion. The distortion depends linearly on magnetic field intensity and on the difference between the frequency of the CRT vertical raster scan and the frequency of the interfering magnetic field. Herein are analyzed two actual cases of interference produced by the DC-supply line of a metropolitan tram network and by the public electric power distribution network
Circuit Simulation of Photovoltaic Systems for Optimum Interface between PV Generator and Grid
No full textThe paper proposes a circuit simulation procedure based on two steps to determine the steady state working points and to analyze the time domain response of a grid-connected PV system. The overall PV generator is modeled with a very compact two-component physical model. A PV generator, constituted by a string of three standard 30 cell modules, connected to the grid by means of a PWM inverter, a decoupling inductor and a low frequency toroidal transformer is used as practical application example. This system is modeled and simulated using both DC and transient analysis with different modulation index values. Simulation outputs are compared with experimental results obtained from an ad hoc designed prototype system showing good agreement. The proposed circuit simulation procedure and models can be useful in assessing design variables as well as in checking novel hardware/software solutions for maximum power point tracking and grid connection
Are manufacturing I-V Mismatch and Reverse Currents Key Factors in Large Photovoltaic Arrays?
Full text linkIn this paper, two factors typical of large photovoltaic (PV) arrays are investigated: one is the current-voltage (I-V) mismatch consequent to the production tolerance; the other is the impact of reverse currents in different operating conditions. Concerning the manufacturing I-V mismatch, the parameters of the equivalent circuit of the solar cell are computed for several PV modules from flash reports provided by the manufacturers. The corresponding I-V characteristic of every module is used to evaluate the behavior of different strings and the interaction among the strings connected for composing PV arrays. Two real crystalline silicon PV systems of 8 times 250 kW and 20 kW are studied, respectively. The simulation results reveal that the impact of the I-V mismatch is negligible with the usual tolerance, and the insertion of the blocking diodes against reverse currents can be avoided with crystalline silicon technology. On the other hand, the experimental results on I-V characteristics of the aforementioned arrays put into evidence the existence of a remarkable power deviation (3%-4%) with respect to the rated power, linkable to the lack of measurement uncertainty in the manufacturer flash reports
Il Generatore Fotovoaltaico: Mismatch e Risultati della simulazione con le configurazioni di ombratura considerate
No full textIMPIANTI FOTOVOLTAICI DI PICCOLA TAGLIA: ALCUNI IMPIEGHI DEL FOTOVOLTAICO IN AGRICOLTURA E IN EDILIZIA
No full textPower conditioning units in grid-connected photovoltaic systems: A comparison with different technologies and wide range of power ratings
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