A Novel DC Current Injection Suppression Method for Three-Phase Grid-Connected Inverter Without the Isolation Transformer

Due to current sensor errors, tolerance of power switching devices, and asymmetry of PWM gating driving pulses, grid-connected inverters without isolation transformer usually have certain amount of dc components injected to the ac grid. Many efforts, such as using a blocking capacitor, a current dc component feedback control, and a voltage dc component feedback control have been introduced to try to suppress the dc injection to the grid. This paper proposes a novel control strategy of suppressing dc current injection to the grid for a three-phase inverter by accurately sensing the dc component of line voltages of three-phase inverter and adding a dc component control loop. A dc suppression control scheme is presented, and the suppression performance of the proposed dc rejection method is evaluated and compared with the traditional method. Finally, the control scheme is verified on a 20-kW three-phase grid-connected inverter.

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

[2]  Tony Ahfock,et al.  DC offset elimination in a single-phase grid-connected photovoltaic system , 2006 .

[3]  Ronald Sharma.  Removal of DC offset current from transformerless PV inverters connected to utility , 2005 .

[4]  E. Koutroulis,et al.  Optimal Design of Modern Transformerless PV Inverter Topologies , 2013, IEEE Transactions on Energy Conversion.

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

[6]  D. Atkinson,et al.  A review of minimisation of output DC current component methods in single-phase grid-connected inverters PV applications , 2012, 2012 2nd International Symposium On Environment Friendly Energies And Applications.

[7]  Bangyin Liu,et al.  Eliminating DC Current Injection in Current-Transformer-Sensed STATCOMs , 2013, IEEE Transactions on Power Electronics.

[8]  P. Karlsson,et al.  On DC injection to AC grids from distributed generation , 2005, 2005 European Conference on Power Electronics and Applications.

[9]  D. Mukhedkar,et al.  Computer aided evaluation of pipeline current near toroidal HVDC ground electrodes , 1989 .

[10]  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.

[11]  Akio Kitamura,et al.  Test results on DC injection phenomenon of grid connected PV system at Rokko test center , 1996, Conference Record of the Twenty Fifth IEEE Photovoltaic Specialists Conference - 1996.

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

[13]  Guo Xiaoqiang,et al.  DC injection control for grid-connected inverters based on virtual capacitor concept , 2008, 2008 International Conference on Electrical Machines and Systems.

[14]  Dehong Xu,et al.  A Novel Control Strategy of Suppressing DC Current Injection to the Grid for Single-Phase PV Inverter , 2015, IEEE Transactions on Power Electronics.

[15]  Alessandro Ferrero,et al.  A linearization method for commercial Hall-effect current transducers , 2001, IEEE Trans. Instrum. Meas..

[16]  Matthew Armstrong,et al.  A new approach of prevention of DC current component in transformerless grid-connected PV inverter application , 2014, 2014 IEEE 5th International Symposium on Power Electronics for Distributed Generation Systems (PEDG).

[17]  杨波,et al.  Transformerless Inverter With Virtual DC Bus Concept for Cost-Effective Grid-Connected PV Power Systems , 2013 .

[18]  Qi Zhang,et al.  Minimization of the DC Component in Transformerless Three-Phase Grid-Connected Photovoltaic Inverters , 2015, IEEE Transactions on Power Electronics.

[19]  Roberto González,et al.  Transformerless Single-Phase Multilevel-Based Photovoltaic Inverter , 2008, IEEE Transactions on Industrial Electronics.

[20]  Kai Sun,et al.  A Family of Neutral Point Clamped Full-Bridge Topologies for Transformerless Photovoltaic Grid-Tied Inverters , 2013, IEEE Transactions on Power Electronics.

[21]  Dehong Xu,et al.  A novel control strategy to suppress DC current injection of single-phase PV inverter to the grid , 2013, 2013 4th IEEE International Symposium on Power Electronics for Distributed Generation Systems (PEDG).

[22]  G. Franceschini,et al.  A DC Offset Current Compensation Strategy in Transformerless Grid-Connected Power Converters , 2011, IEEE Transactions on Power Delivery.

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

[24]  E. Koutroulis,et al.  Design optimization of transformerless grid-connected PV inverters including reliability , 2012, 2012 Twenty-Seventh Annual IEEE Applied Power Electronics Conference and Exposition (APEC).

[25]  E. Olias,et al.  DC Current Injection Into the Network from PV Grid Inverters , 2006, 2006 IEEE 4th World Conference on Photovoltaic Energy Conference.

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

[27]  A. Emanuel,et al.  Direct Current Generation in Single-Phase Residential Systems DC Effects and Permissible Levels , 1984, IEEE Transactions on Power Apparatus and Systems.