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Abstract
This work presents a method of voltage insertion into the grid with harmonic distortions through a dynamic voltage restorer (DVR) for protection of sensitive loads to short-term voltage sags. The aim is to recover the nominal voltage level at the load by restoring only the fundamental frequency component without compensating the harmonic contents. Corrections carried out in this manner are justified as the DVR is a device dedicated to restore the amplitude of the sensitive load to its rated value, based on rapid variations from the power grid. The correction of distortions is not suitable for this equipment as harmonics are permanent problems and originate from nonlinearities of electrical loads. Therefore, the batteries that supply the DVR do not support the correction of permanent problems, only for rapid variations. Thus, it allows an extension in the lifespan of the batteries (needed in this type of compensator). Collaterally, restoring only the fundamental decreases the total harmonic distortion of the load, thus allowing this method to make a double contribution to improving the system’s power quality. For this purpose, a recursive least-square estimation is developed, suitable for voltages with harmonic content, here called HRLS. The construction of the reference voltage to be produced by the DC–AC converter also considers the synchronism with the fundamental component of the grid, which allows an optimization of the voltage level used on the DC-link. Correction scenarios only inserting the fundamental, as well as with harmonic content, are tested in simulation to compare performance in the use of the compensator power. The same scenarios are also tested on an experimental platform developed in the laboratory to confirm the proposal.
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Notes on contributors
Paulo J. P. Santos
Paulo J. P. dos Santos received the B.S. degree from the Department of electrical Engineering, Centro Universitario Estacio do Recife, Pernambuco, Brazil, in 2017 and the MBA degree in Industrial Management from the Faculdade da Industria de Curitiba, Curitiba, Brazil, in 2018. He is currently a Master degree student at the Federal University of Paraiba (UFPB), and a Maintenance Engineer with Ache Laboratorios Farmaceuticos, Pernambuco, Brazil, where he specializes in the Maintenance Management. His research is focused on power optimization.
Darlan A. Fernandes
Darlan A. Fernandes received the B.S. degree in electrical engineering from the Federal University of Paraiba, Brazil, in 2002, and the M.S. and Ph.D. degrees in electrical engineering from the Federal University of Campina Grande, Brazil, in 2004 and 2008, respectively. He was a Visiting Scholar at the Center for Power Electronics Systems (CPES) at the Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, United States, from 2018 to 2019. From 2007 to 2011, he was a Professor with the Industry Department in the Federal Center of Technological Education of Rio Grande do Norte. He is currently an Associate Professor with the Department of Electrical Engineering, Federal University of Paraiba, Brazil. His research interests are in the applications of power electronics in distribution systems, power quality, photovoltaic systems, and impedance-based control design techniques for static converters.
Alfeu J. Sguarezi Filho
Alfeu J. Sguarezi Filho received his Ph. D. degree from Campinas University in Brazil in 2010. He is a full time professor at Federal University of ABC - UFABC, in Santo André, Brazil, teaching in the areas of Electrical Machines, Power Electronics and Electrical Drives. His research interests are machine drives, wind and photovoltaic energies, doubly-fed induction generators, power control, and electrical power systems.
Fabiano F. Costa
Fabiano F. Costa received the B.S., M.S., and Ph.D. degrees from the University of São Paulo (USP), Federal University of Paraíba (UFPB), and Federal University of Campina Grande (UFCG) in 1997, 2001 and 2005 respectively, all in electrical engineering. He is currently with the Department of Electrical Engineering at the Federal University of Bahia as Associate Professor. His current research interests include topics related to the stability and modeling of static converters, mainly the grid-connected LCL inverter. These topics are impedance-based modeling methods, phase-locked loops techniques, online methods for estimating grid impedances, and Nyquist criteria for accessing the converter’s stability.