Multilevel inverter for grid interconnection with square wave voltage sources and minimisation of active filter capacity

This paper proposes an integrated micro-inverter using a multiple-step controlled voltage source and an active filter connected in series. Recently, a micro-inverter based on an isolated resonant DC-DC converter is widely used. A typical micro-inverter can achieve a high efficiency around 97%. In addition, a micro-inverter system can achieve high efficiency of maximum power point tracking (MPPT) thanks to its small photovoltaic area. The proposed circuit is a combination of a multiple-step controlled voltage source, an active filter connected in series and an unfolding circuit. This circuit reduces the power to be converted to 1/8 compared to a conventional inverter. The control strategy for the proposed circuit is also discussed in this paper. Finally, the grid connected operation is verified through circuit simulation.