H-Bridge transformerless inverter with common ground for single-phase solar-photovoltaic system

This paper proposes a new single-phase H-Bridge transformerless inverter with common ground for grid-connected photovoltaic systems (hereafter it is called `Siwakoti-H' inverter). The inverter works on the principle of flying capacitor and consists of only four power switches (two reverse blocking IGBT's (RB-IGBT) and two MOSFET's), a capacitor and a small filter at the output stage. The proposed topology share a common ground with the grid and the PV source. A Unipolar Sinusoidal Pulse-Width Modulation (SPWM) technique is used to modulate the inverter to minimize switching loss, output current ripple and filter requirements. The main advantages of the new inverter topology are the elimination of the leakage current and ability to provide reactive power to the grid. Further, the peak of output ac voltage is equal to input dc-voltage (unlike NPC and ANPC type which requires two times of the peak ac-voltage magnitude). Simulation as well as experimental results from a 1 kW prototype are presented at the end of the paper to prove the concept and also the theoretical analysis presented.