Strategies to Deal with Ground Faults in Grid-Connected Transformerless Photovoltaic Converters with Battery Energy Storage System

Lucas V. Bellinaso; Ricardo S. Figueredo; Marcelo P. Almeida; Ricardo J. F. Bortolini; Ildo Bet; Leandro Michels; Roberto Zilles

doi:10.18618/REP.2019.3.0015

Authors

Lucas V. Bellinaso Power Electronics and Control Group of the Federal University of Santa Maria, Santa Maria, RS, Brazil
Ricardo S. Figueredo PHB Eletrônica LTDA, São Paulo, SP, Brazil
Marcelo P. Almeida Universidade de São Paulo - USP, São Paulo, SP, Brazil
Ricardo J. F. Bortolini Power Electronics and Control Group of the Federal University of Santa Maria, Santa Maria, RS, Brazil
Ildo Bet PHB Eletrônica LTDA, São Paulo, SP, Brazil
Leandro Michels Power Electronics and Control Group of the Federal University of Santa Maria, Santa Maria, RS, Brazil
Roberto Zilles Universidade de São Paulo - USP, São Paulo, SP, Brazil

DOI:

https://doi.org/10.18618/REP.2019.3.0015

Keywords:

Electric shock, Photovoltaic power systems, Power Electronics, Protective relaying, Uninterruptible Power Systems

Abstract

Grid-connected photovoltaic systems with energy storage, also called PV hybrid mini-grid system (PVHMS), operate in both grid-tied and stand-alone modes and are expected to play an important role in distributed generation. Transformerless photovoltaic converters are most preferred for these systems due to their higher conversion efficiency in comparison to insulated converters, increasing autonomy of the battery energy storage system (BESS). Safety in transformerless photovoltaic converters is a critical issue due to parasitic capacitance between PV modules and ground that could result in high leakage current. Existing safety requirements for grid-tied PV inverters may not be sufficient for PVHMS converters since they have multiple leakage current paths. This study analyzes some leakage-current-related faults on transformerless PVHMS converters, and proposes relay opening sequences to avoid unnecessary interruptions of power supply for the local loads. The following situations are analyzed: i) fault at dc side, ii) fault at ac load side, and iii) commutation between on-grid and off-grid operation modes. These faults have been studied for a transformerless PVHMS converter with a single dc-ac stage. Experimental results are presented to validate the proposed schemes and a table summarizing the proposals is presented.

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Author Biographies

Lucas V. Bellinaso, Power Electronics and Control Group of the Federal University of Santa Maria, Santa Maria, RS, Brazil

received the B.S. and M.S. degrees in electrical engineering, in 2012 and the M.Sc. and PhD degrees in electrical engineering from the Federal University of Santa Maria (UFSM), Santa Maria, Brazil, in 2014 and 2017, respectively. Since 2015, he has been with the Power Electronics and Control Group (GEPOC) at the same university, where he is currently Professor. His research interests are PV systems, applied digital control, and power management of microgrids.

Ricardo S. Figueredo, PHB Eletrônica LTDA, São Paulo, SP, Brazil

Ricardo Souza Figueredo received the B.S. degree in electrical engineering from the Pontifical Catholic University of Sao Paulo, São Paulo, Brazil, in 2010 and the M.S. degree in electrical engineering from the Polytechnic School of the University of São Paulo, São Paulo, Brazil, in 2015. His current research interests include design and modelling of power converters for renewable energy sources and digital control of power converters.

Marcelo P. Almeida, Universidade de São Paulo - USP, São Paulo, SP, Brazil

was born in Belém, Brazil, in 1987. He received the B.Eng. degree in Electrical Engineering from the Federal University of Pará (UFPA), Brazil, in 2009, the M.Sc. degree in Energy from the University of São Paulo (USP), Brazil, in 2012, and the D.Sc. degree in Energy in 2017, also from USP. He is a researcher at the Photovoltaic Systems Laboratory (LSF) of the Institute of Energy and Environment of the University of São Paulo (LSF-IEE-USP), the vice president of the Brazilian Solar Energy Association (ABENS), a board member of the International Solar Energy Society (ISES) and a reviewer of Solar Energy and Progress in Photovoltaics: Research and Applications journals.

Ricardo J. F. Bortolini, Power Electronics and Control Group of the Federal University of Santa Maria, Santa Maria, RS, Brazil

was born in Rodeio Bonito, Brazil, in 1992. He received the B.S degree in Automatic Control and Systems Engineering and M.Sc. degree in Electrical Engineering from the Federal University of Santa Maria (UFSM), Brazil in 2015 and 2018, respectively. He is currently a Ph.D. student and substitute technical manager of the UFSM’s PV inverters tests laboratory and is member of working groups that develops Brazilian’s PV standards. His current research interests include PV systems and in field measurements of PV systems.

Ildo Bet, PHB Eletrônica LTDA, São Paulo, SP, Brazil

Founding partner and director of engineering of PHB Eletrônica Ltda since 1984 in the city of São Paulo. He holds a degree in Electrical Engineering from PUC-RS (1978) and a Master's degree in Power Electronics from INEP / UFSC (1981). He is the director of ABINEE's Photovoltaic Sector Group and is coordinator of ABNT / COBEI / CE03: 82.01 - Photovoltaic Systems Studies Committee, focusing on Brazilian technical standards for photovoltaic inverters connected to the grid.

Leandro Michels, Power Electronics and Control Group of the Federal University of Santa Maria, Santa Maria, RS, Brazil

received the B.S and Ph.D. degrees in Electrical Engineering from Federal University of Santa Maria (UFSM), Brazil, in 2002 and 2006, respectively. He is currently an Associate Professor at the UFSM working with the Power Electronics and Control Research Group (GEPOC) and has a research grant level DT-1D from National Council for Scientific and Technological Development (CNPq-Brazil). Dr. Michels is the manager of UFSM's PV inverters tests laboratory and is member of Eletrôn. Potên., Joinville, v. 24, n. 3, p. 314-322, jul./set. 2019 322 working groups that develops Brazilian's PV standards. His current research interests include PV systems and applied digital control.

Roberto Zilles, Universidade de São Paulo - USP, São Paulo, SP, Brazil

Roberto Zilles was born in Novo Hamburgo, Rio Grande do Sul, Brazil, in 1960. He received the B.S. degree in Physics from the Federal University of Rio Grande do Norte (UFRN), Brazil, in 1985, and M.S. degree in mechanical engineering from the Federal University of Rio Grande do Sul (UFRGS), Brazil, in 1988, and the Dr. Ing. degree from the Polytechnic University of Madrid, Spain, in 1993. He founded the Photovoltaic System Laboratory from the Institute of Energy and Environment of the São Paulo University (LSF-IEE-USP) in 1995. Prof. Zilles, since 1998, is member of editorial board of the Progress in Photovoltaics: Research and Applications journal.