Modeling and stability of large-scale PV plants due to grid impedance

Grid-connected photovoltaic(PV) system will become unstable when the grid impedance(Lg) is large, especially large-scale PV plant connected to weak grid (Lg is large). In this paper, a three-phase paralleled inverter equivalent Norton model is established to study the stability of large-scale PV plants including the grid impedance; the expression of the output current and point of common coupling (PCC) voltage are derived; and then the current loop stability of three-phase paralleled grid-connected inverters is analyzed by root locus method; the study is validated through simulation. Studies have shown that: there is no inter-phase coupling effects in the equivalent Norton model of the three-phase inverters, the inner current loop of the paralleled inverters will unstable in range of some parameters depending on the grid impedance.

[1]  Yosuke Fujii,et al.  Parallel connection of grid-connected LCL inverters for MW-scaled photovoltaic Systems , 2010, The 2010 International Power Electronics Conference - ECCE ASIA -.

[2]  Yun Wei Li,et al.  Investigation and resonances damping of multiple PV inverters , 2012, 2012 Twenty-Seventh Annual IEEE Applied Power Electronics Conference and Exposition (APEC).

[3]  J L Agorreta,et al.  Modeling and Control of $N$ -Paralleled Grid-Connected Inverters With LCL Filter Coupled Due to Grid Impedance in PV Plants , 2011, IEEE Transactions on Power Electronics.

[4]  Jianyun Chai,et al.  Analysis of harmonic and circulating current for paralleling inverters in MW-level wind energy conversion system , 2008, 2008 International Conference on Electrical Machines and Systems.

[5]  M. Liserre,et al.  Stability of grid-connected PV inverters with large grid impedance variation , 2004, 2004 IEEE 35th Annual Power Electronics Specialists Conference (IEEE Cat. No.04CH37551).

[6]  Yi Lei,et al.  Modeling and analysis of MW-level grid-connected PV plant , 2011, IECON 2011 - 37th Annual Conference of the IEEE Industrial Electronics Society.

[7]  Jian Sun,et al.  Impedance-Based Stability Criterion for Grid-Connected Inverters , 2011, IEEE Transactions on Power Electronics.

[8]  Francesc Guinjoan,et al.  Stability analysis of grid-connected PV systems based on impedance frequency response , 2011, 2011 IEEE International Symposium on Industrial Electronics.

[9]  Zhengming Zhao,et al.  Overview of Large-scale Grid-connected Photovoltaic Power Plants , 2011 .

[10]  M. Liserre,et al.  Stability of photovoltaic and wind turbine grid-connected inverters for a large set of grid impedance values , 2006, IEEE Transactions on Power Electronics.