Effectiveness of Virtual Ground Technique on a Single Phase Full Bridge Voltage Source Inverter using Unipolar and Bipolar Sinusoidal PWM

Abstract

In a transformerless grid-connected PV inverter, the presence of a parasitic capacitance between the solar cells and the metal frame can cause ground leakage current to flow through the circuit composed of the electrical grid, the parasitic capacitance, and the metal frame of the panel. The magnitude of this current can be high and can constitute a safety risk itself if precautions are not taken. So to counter these issues on a VSI based PV system, an internal current return path is provided in the circuit from the load side to the source side to reduce the ground leakage current due to the formation of parasitic capacitance at the PV side. In this work, a single-phase Full Bridge grid connected VSI is connected to a PV panel with the current return path, also known as Virtual Ground, which can significantly reduce the Leakage Current that flows to the neutral of the grid connections that share the common ground with the PV mounted structures are realized. The effectiveness of Virtual Ground was studied for unipolar and bipolar PWM methods in a single-phase grid connected PV VSI using simulations that were carried out using MATLAB/Simulink.