Simulation and Analysis of a Multilevel Converter Topology for Solar PV Based Grid Connected Inverter

Adil Sarwar, Mohammad S. J. Asghar

.

DOI: 10.4236/sgre.2011.21007                

Abstract

There has been a noticeable increase in use of Solar PV based systems for power generation, given its renewable nature. A solar PV based grid tie inverters are used for dc-ac conversion. The conventional line commutated ac-to-dc inverters have square-shaped line current which contains higher-order harmonics. The line current with the high harmonic contents generates EMI and moreover it causes more heating of the core of distribution/power transformers. Alternatively, PWM based inverters using MOSFET/IGBT switches are also used for the same purpose. However, apart from higher switching losses, the power handling capability and reliability of these devices are quite low in comparison to thyristors/SCR. Nevertheless, the conventional thyristor based forced commutated inverters are not suitable for PWM applications due to the problems of commutation circuits. A pure sinusoidal line current or waveform with low har- monic contents is the most desirable. In the present work, a multilevel line commutated inverter topology has been proposed and analyzed which improves the wave shape and hence reduces the total harmonic distortion (THD) of the line current in a grid tie line commutated inverter. The scheme has successfully been implemented and tested. Moreover, the performance of the proposed topology is far better than the conventional line-commutated inverter. It reduces THD, losses, switching stress and EMI.

Keywords

Multilevel Inverter, Total Harmonic Distortion, Grid Connected Inverter

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	J. Kumar, B. Das and A. Pramod, “Selective Harmonic Elimination Technique for a Multilevel Inverter,” Proceedings of Fifteenth National Power Systems Confer- ence (NPSC), Bombay, December 2008, pp. 608-613.
[2]	J. S. Lai and F. Z. Peng, “Multilevel Converters—A new Breed of Power Converters,” IEEE Transactions on Industry Applications, Vol. 32, No. 3, 1996, pp. 509-517. doi:10.1109/28.502161
[3]	L. M. Tolbert, J. N. Chiasson, Z. Du and K. J. McKenzie, “Elimination of Harmonics in a Multilevel Converter with Nonequal DC Sources,” IEEE Transaction on Industry Applications, Vol. 41, No. 1, 2005, pp. 75-81. doi:10.1109/TIA.2004.841162
[4]	L. M. Tolbert, F. Z. Peng and T. G. Habetler, “Multilevel Converters for Large Electric Drives,” IEEE Transactions on Industry Applications, Vol.35, No. 1, 1999, pp. 36-44. doi:10.1109/28.740843
[5]	J. Iwaszkiewicz and B. J. Perz, “Multilevel Convertors for Distributed Power Generation Systems with DC Voltage Sources,” International Conference on Renewable Energies and Power Quality, Saragossa, 2005.
[6]	A. Myrzlk and M. A. Johanna, “Novel Inverter Topologies for Single-Phase Stand-Alone or Grid Connected Photo-Voltaic Systems,” 4th IEEE International Conference on Power Electronics and Drive Systems, Denpassar, October 2001, pp. 103-108.
[7]	A. Sarwar, M. S. J. Asghar, Imdadullah and S. K. Moin Ahmed, “Development of Solar PV Based Grid Connected Inverters,” Proceedings of International Conference on Electrical Energy System & Power Electronics (ICEESPEEE’09), Chennai, April 2009, pp. 1172-1177.