Dual polarity DC–DC converter integrated grid‐tied single‐phase transformer less inverter for solar application

Abstract

This study proposes a novel single‐phase transformer‐less inverter, using the principle of combined Ćuk SEPIC (CCS) converter for grid‐connected photovoltaic (PV) systems. The new inverter has a common ground between the grid and the PV source, which helps to eliminate the leakage current for the grid‐connected PV application. Unlike common ground‐type charge‐pump‐based transformer‐less inverter, this topology eliminates inrush current and hence reduces the current stress on the components. The CCS allows voltage control with both step‐up and step‐down abilities, along with more robustness against solar panel side fault. Further, application of wide band‐gap devices, such as SiC MOSFETs allows higher switching frequency to be achieved, and thus reduction of the passive components. A novel switching strategy, proposed here allows current in both directions, positive and negative (to the load/grid or from the load/grid, for reactive loads), making the converter suitable for grid connection (unity power factor), as well as stand‐alone operation. The proposed concept has been discussed in detail, along with simulation results. Finally, a prototype hardware has been fabricated and the experimental results are reported.