Study of Leakage Current Phenomena in Hybrid 2/3-Level Three-Phase Transformerless Photovoltaic Grid-Connected Inverters

In photovoltaic (PV) applications, it is possible to eliminate the transformer from the PV system in order to improve the efficiency and reduce cost, losses, and size. The main issue arises when the transformer is removed. This issue is due to the presence of a parasitic capacitance between the metal frame of the panel and the PV cells. This stray capacitor causes the leakage current. This current increases current harmonics injected into the utility grid, the radiated and conducted electromagnetic emissions, and losses. In this paper, application of the hybrid 2/3-level converter as grid-connected photovoltaic inverter is studied. Moreover, a novel modulation method is proposed for this topology that can be efficiently implemented to reduce leakage current. Through simulation case studies, the effectiveness of the proposed modulation method is validated; unlike traditional full-bridge inverters, leakage current of hybrid 2/3-level converter meet the requirements of transformerless PV inverters.

Keywords:

Transformer-less photovoltaic (PV) system , leakage current , parasitic capacitor , sinusoidal pulse width modulation (SPWM) strategy , hybrid 2/3-level inverter