Low cost and compact six switch seven level grid tied transformerless PV inverter

Transformerless inverters with common ground structure are favoured in grid-connected photovoltaic (PV) systems primarily due to their ability to effectively suppress leakage current, eliminate transformer-related losses, enhance efficiency, and reduce costs. A six switch seven-level (S2-7 L) common ground type triple boost transformerless inverter topology for grid-tied solar PV applications is presented in this paper. The proposed structure maintains a constant common-mode voltage by sharing a common ground point between the source and the grid neutral, so effectively suppressing leakage current. The proposed topology's key advantages include generating a seven-level output voltage with only six switches, minimal conducting switches, and the lowest total standing voltage per unit. The article includes the modes of operation, design of passive components, and filter inductors. The MATLAB/Simulink software is employed for the simulation and experimental validation of 825 W through the use of a prototype model. A comprehensive comparison analysis of the proposed topology with the existing 7-level SC topologies is also included. The FFT analysis shows that the S2-7 L inverter has a THD of 17.2% for voltage, and 3.9% for grid current, confirming that these values are within the limits specified by the IEEE-519 standards.