Control strategy for a multilevel inverter in grid-connected photovoltaic applications

A novel conversion structure for photovoltaic (PV) grid connection is proposed in this paper. The conversion system is aimed to be relatively simple and effective in medium and high power range. The topology utilizes a dual two-level voltage source inverter (VSI), fed by two insulated PV fields, supplying a grid transformer with open-end connection. Use of proposed scheme doubles the output power range of the conversion system with respect to the rated power of a single inverter, without the need of series/parallel connections of power switches. Furthermore, the dual inverter structure allows multilevel voltage waveforms, reducing grid current harmonics and mitigating output voltage derivatives. An original control method has been introduced to regulate the dc-link voltages for each VSI. The proposed algorithm has been verified by numerical tests with reference to different operating conditions.

[1]  Toshihisa Shimizu,et al.  Generation control circuit for photovoltaic modules , 2001 .

[2]  Se-Kyo Chung,et al.  A phase tracking system for three phase utility interface inverters , 2000 .

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

[4]  D. Casadei,et al.  Power balancing of a multilevel converter with two insulated supplies for three-phase six-wire loads , 2005, 2005 European Conference on Power Electronics and Applications.

[5]  Luca Zarri,et al.  Switching Technique for Dual-Two level Inverter Supplied by Two Separate Sources , 2007, APEC 07 - Twenty-Second Annual IEEE Applied Power Electronics Conference and Exposition.

[6]  Sergio Busquets-Monge,et al.  Interfacing Renewable Energy Sources to the Utility Grid Using a Three-Level Inverter , 2006, IEEE Transactions on Industrial Electronics.

[7]  Y. Kawabata,et al.  SVG using open-winding transformer and two inverters , 2004, 2004 IEEE 35th Annual Power Electronics Specialists Conference (IEEE Cat. No.04CH37551).

[8]  Keith Corzine,et al.  Performance characteristics of a cascaded two-level converter , 1999 .

[9]  K. Gopakumar,et al.  A dual two-level inverter scheme with common mode voltage elimination for an induction motor drive , 2004, IEEE Transactions on Power Electronics.

[10]  Luis Moran,et al.  A three-phase active power filter operating with fixed switching frequency for reactive power and current harmonic compensation , 1995, IEEE Trans. Ind. Electron..