Novel self balancing single phase asymmetric 9 level grid connected inverter for photovoltaic applications

Abstract

This paper proposes a novel, asymmetric 9 level multi-level inverter (MLI) topology which can self balance voltage across input side capacitors by series charging and parallel discharging. The proposed inverter can take two low voltage PV sources as input to produce high voltage AC at the output. In addition to this, the inverter can boost the input voltage by up to 1.5 times and inject good quality power into the grid when the two PV sources operate at different MPPs (e.g. owing to different illumination conditions). The proposed MLI contains a total of ten power switches out of which two switches operate at 100Hz and remaining 8 switches operate at high switching frequency. 100Hz frequency operating switches have voltage withstanding capability equal to the total DC voltage applied to the input. Four out of 8 high frequency switches can bear 0.5 times the input DC voltage. Remaining four switches and eight of the power diodes can bear voltage 0.25 times the input DC voltage. Filter requirements are reduced drastically because of more number of levels at output. All the simulation and experimental results of this work are presented.