1,721,177 research outputs found
UN SISTEMA DI CONTROLLO PER L’UTILIZZO DI DISPOSITIVI SSC PER LA COMPENSAZIONE DI POTENZA REATTIVA
No full textPhotovoltaic generating units as reactive supply ancillary service providers
No full textThis paper addresses the issue of the application of PhotoVoltaic (PV) Distributed Generation (DG) units for supplying reactive power to the grid. In order to reach this aim, an advanced control scheme to suitably drive the injection of both active and reactive power into a MV radial distribution grid has been developed. Such algorithm allows a decoupled control of active and reactive power by properly adjusting the modulating signals of a PWM interface converter with the grid. A closed loop regulation scheme has been derived and guidelines for the choices of the reference quantities and for the design of the regulators are provided. The control algorithm has been applied to a real MV grid-connected PV power plant, which has been simulated in the PSCAD - EMTDC electromagnetic environment, in order to represent, with high detail, every system component and to thoroughly analyze the occurring electromagnetic transients. The positive effect of reactive power support to the grid from the PV unit has been highlighted, showing benefits on the grid current and voltage profiles with respect to the classical configuration, where the DG system behaves as a sole active power source. © 2008 The Berkeley Electronic Press. All rights reserved
Cooray-Rubinstein formula for the evaluation of lightning radial electric fields: derivation and implementation in time domain
No full textA regularization approach for high-frequency electromagnetic field-to-line coupling analysis
No full textThe problem of the high-frequency electromagnetic field coupling to an overhead electrical transmission line is an important issue in power signal transmission and here it is dealt with the regularization theory of ill-posed problems. The integro-differential equation describing the field-induced current into a line of finite length lying over a perfectly conducting soil is solved combining the use of Fourier series expansion and the Landweber algorithm. More precisely, the iterative regularization procedure is applied in order to obtain the value of the Fourier coefficients. © 2012 IOP Publishing Ltd
Inverter-Based Nanogrid Design with Integration of Primary, Secondary and Tertiary Controls – A Case Study
No full textThis paper investigates the performance of a hierarchical control framework in an inverter-based Nanogrid (NG) serving a building. The NG integrates a 21 kW Photovoltaic (PV) array and two 40 kWh Battery Energy Storage Systems (BESS1 and BESS2). Firstly, a Mixed-Integer Quadratically Constrained Programming (MIQCP) Energy Management System (EMS) was implemented in MATLAB/YALMIP and solved with Gurobi, executing a dayahead optimization to minimize cost. Secondly, a simulation was carried out to test the behavior of the NG when undergoing a load increase contingency during islanded mode operation. To this purpose, the NG was implemented in MATLAB/Simulink Simscape. The EMS results highlighted that PV selfconsumption through BESSs is the best solution to minimize the operating costs of the facility. Dynamic simulation showed that the BESSs, by increasing the power output, are able to stop the frequency variation in the NG to 49.8 Hz, efficiently providing a frequency containment action
An improved electrical power supply system for tunnels, particularly for road tunnels
No full textThe purpose of the invention is to provide an improved system for the power supply in a tunnel, which offers an increased operative reliability in all normal and emergency conditions, as well as having low operating costs
Lightning return stroke current radiation in presence of a conducting ground: 1. Theory and numerical evaluation of the electromagnetic fields
No full textThe general theory describing the electromagnetic field radiated by a lightning stroke over a conducting ground is presented in this paper. The derivation of the Green functions necessary to solve the problem is discussed in detail, and the determination of the expressions for the electromagnetic field components is carried out in a form that minimizes the final computational costs. A method for the numerical evaluation of the electromagnetic field is then proposed, and it is shown that it can be used starting from any "engineering model" representation for the lightning current distribution along the channel. Such method is based on a new efficient evaluation of the so-called Sommerfeld's integrals appearing in the electromagnetic field expressions, without resorting to any kind of approximated formulas for them. The numerical treatment of the Sommerfeld's integrals is characterized by a proper subdivision of the integration domain, the use of the Romberg technique and the determination of a suitable upper bound for the error due to the integral truncation. In the second part of this work it will be shown how the results provided by the developed theory can be used in order to assess the validity of the most common simplified approach for the calculation of the lightning radiation over a lossy ground plane. Copyright 2008 by the American Geophysical Union
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