A Single Stage Doubly Grounded Transformerless Inverter Topology With Buck-Boost Voltage Capability for Grid Connected PV Systems

This paper presents a novel single-stage doubly grounded transformerless inverter configuration which can buck-boost the output voltage. In this transformerless inverter configuration grid neutral is directly connected to PV panel negative rail which suppresses/eliminates the PV leakage currents. In addition, the tracking of maximum power point is possible for wide variation of weather conditions due to buck-boost voltage capability of inverter. Moreover, the proposed inverter topology has symmetrical operation in both half cycles hence injects negligible DC offset current in to the grid. Here the symmetrical operation of inverter is achieved due to one inductor is used for both half cycles of the grid. The proposed topology is realized using five switches, two of which work at 50 Hz and remaining three switches at high frequency which reduces overall semiconductor losses. Further, the proposed inverter topology is controlled through a newly developed modulation technique and possible working modes are analyzed and described thoroughly. For performance validation, the simulation analysis of grid connected proposed inverter is performed on a 1 kVA system and results show that proposed inverter feeds power in to the grid with lesser THD while achieving greater efficiency.

Keywords: Double grounding, Transformerless inverter topology, Buck-boost voltage capability, Grid connected PV inverter, Common mode voltage (CMV), Total harmonic distortion (THD).