A Five-Level Common-Ground Inverter With Reduced Switch Count for Transformerless Grid-Tied PV Applications

Multilevel inverters with common-ground feature have been getting attention especially for grid-tied photovoltaic systems. These inverters have the grid neutral line connected to the negative pole of the dc bus, eliminating the common-mode leakage current which is a critical issue in grid-connected PV systems. This paper proposes a common-ground five-level transformerless inverter with a reduced switch count for solar photovoltaic applications. The proposed inverter comprises only four power switches, three diodes, two capacitors and two inductors. Moreover, only two switches operate at high-frequency, enabling the reduction of switching losses. The interleaved operation of a coupled inductor enhances the quality of the output current, as the first group of harmonic components is around twice the switching frequency. Additionally, a full dc-bus voltage utilization is provided and the reactive power capability is achieved. The paper details the operation modes, the design guidelines as well as a control and modulation strategy for the proper operation of the inverter. Finally, experimental results are obtained to validate the performance of the proposed grid-tied inverter.