Maximising power yield in a transformerless single-phase grid connected inverter servicing two separate photovoltaic panels

A single-phase grid connected transformerless inverter for solar photovoltaic (PV) systems is presented in this study. This inverter has the capability to extract maximum power from two separate PV panels operating under equal as well as mismatched meteorological conditions. The proposed inverter is based on the buck-boost principle, and hence, can tolerate a wide variation of voltage in both the PV panels. Further, due to the neutral point clamped structure of the inverter the neutral/ground terminal of grid is directly connected at the midpoint of two PV panels. This eliminates the flow of leakage current through the parasitic capacitances existing between the PV panels and the ground. The proposed inverter requires six switches and is free from shoot-through fault. This inverter does not require sensing of grid current for its operation. The principle of operation of the inverter is presented. The control strategy devised for the inverter is provided. The theoretical analysis is supported through detailed simulation studies carried out on Matlab/Simulink platform. Exhaustive experimental results obtained from a scaled down laboratory prototype developed for the inverter are presented to confirm the validity of the scheme.