DC current injection into the network from transformerless and LF transformer photovoltaic inverters

The present paper is focused on the study of the DC current injection in the case of photovoltaic (PV) inverters. The source of the leakage current of the transformerless PV inverters is deeply studied among the three most relevant groups that coexist in the market. This study includes measurements of two types of inverters (transformerless and transformer PV inverters) in order to evaluate and compare the behaviour of the injection of the DC current into the grid. According to the assessment of the measurements, the results show that in both cases there is evidence of DC current in the AC grid side, overcoming the limit applied on most of the standards.

[1]  Juan Jose Corrales Hernandez,et al.  Guidelines for the technical assessment of harmonic, flicker and unbalance emission limits for PV-di , 2011 .

[2]  J. C. Hernández,et al.  Statistical characterisation of harmonic current emission for large photovoltaic plants , 2014 .

[3]  J. Doval-Gandoy,et al.  Eliminating Ground Current in a Transformerless Photovoltaic Application , 2010, IEEE Transactions on Energy Conversion.

[4]  Yangguang Yan,et al.  Seamless Transfer of Single-Phase Grid-Interactive Inverters Between Grid-Connected and Stand-Alone Modes , 2010, IEEE Transactions on Power Electronics.

[5]  S.V. Araujo,et al.  Novel grid-connected non-isolated converters for photovoltaic systems with grounded generator , 2008, 2008 IEEE Power Electronics Specialists Conference.

[6]  A. Ahfock,et al.  Direct current offset controller for transformerless single-phase photovoltaic grid-connected inverters , 2010 .

[7]  Vassilios G. Agelidis,et al.  Multilevel converters for single-phase grid connected photovoltaic systems-an overview , 1998, IEEE International Symposium on Industrial Electronics. Proceedings. ISIE'98 (Cat. No.98TH8357).

[8]  Adriana Palomar Lozano.  Análisis y estudio del rendimiento de inversores integrados en los sistemas fotovoltaicos de conexión a red , 2009 .

[9]  P. G. Vidal,et al.  Characterization of the insulation and leakage currents of PV generators: Relevance for human safety , 2010 .

[10]  Mei Qiang,et al.  Real-time DC injection measurement technique for transformerless PV systems , 2010, The 2nd International Symposium on Power Electronics for Distributed Generation Systems.

[11]  Manuel Ortega,et al.  Measurement and assessment of power quality characteristics for photovoltaic systems: Harmonics, flicker, unbalance, and slow voltage variations , 2013 .

[12]  David J. Atkinson,et al.  Approach to low-cost prevention of DC injection in transformerless grid connected inverters , 2010 .

[13]  A. Ahfock,et al.  DC magnetisation of transformers , 2006 .

[14]  Yunjie Gu,et al.  A transformerless grid connected photovoltaic inverter with switched capacitors , 2011, 2011 Twenty-Sixth Annual IEEE Applied Power Electronics Conference and Exposition (APEC).

[15]  Hembram Mansing.  A Cascaded Inverter For Transformerless Single Phase Grid Connected Photovoltaic Systems , 2013 .

[16]  Andres Barrado,et al.  DC current injection into the network from PV inverters of <5 kW for low-voltage small grid-connected PV systems , 2007 .

[17]  Youngseok Jung,et al.  High-frequency DC link inverter for grid-connected photovoltaic system , 2002, Conference Record of the Twenty-Ninth IEEE Photovoltaic Specialists Conference, 2002..

[18]  Yi Zhao,et al.  Design and Analysis of a Grid-Connected Photovoltaic Power System , 2010, IEEE Transactions on Power Electronics.

[19]  F. Blaabjerg,et al.  A review of single-phase grid-connected inverters for photovoltaic modules , 2005, IEEE Transactions on Industry Applications.

[20]  Xiao-Qiang Guo.  Real-time measurement method of dc injection for transformerless PV systems , 2011 .

[21]  P. Sanchis,et al.  Transformerless Inverter for Single-Phase Photovoltaic Systems , 2007, IEEE Transactions on Power Electronics.

[22]  U. Borup,et al.  Transformerless Photovoltaic Inverters Connected to the Grid , 2007, APEC 07 - Twenty-Second Annual IEEE Applied Power Electronics Conference and Exposition.

[23]  Emilio Olias,et al.  Overview of the legislation of DC injection in the network for low voltage small grid-connected PV systems in Spain and other countries , 2008 .

[24]  M. Liserre,et al.  Common mode voltage in case of transformerless PV inverters connected to the grid , 2008, 2008 IEEE International Symposium on Industrial Electronics.

[25]  Zhang Zheng-mao.  The progress and development trend of the DC injection issue in PV grid-connected systems , 2012 .

[26]  T. S. Key,et al.  Utility compatibility of nonisolated residential power conditioners , 1987 .

[27]  Yunjie Gu,et al.  Improved Transformerless Inverter With Common-Mode Leakage Current Elimination for a Photovoltaic Grid-Connected Power System , 2012, IEEE Transactions on Power Electronics.

[28]  Francisco A. S. Neves,et al.  Eliminating Leakage Currents in Neutral Point Clamped Inverters for Photovoltaic Systems , 2012, IEEE Transactions on Industrial Electronics.

[29]  Pablo Sanchis,et al.  Ground currents in single-phase transformerless photovoltaic systems , 2007 .

[30]  C.M. Johnson,et al.  Auto-Calibrating DC Link Current Sensing Technique for Transformerless, Grid Connected, H-Bridge Inverter Systems , 2006, IEEE Transactions on Power Electronics.