Hybrid-bridge transformerless photovoltaic grid-connected inverter

Abstract

The transformerless inverters with leakage current suppression have become an urgent application tendency in grid-connected photovoltaic systems because of low cost and high efficiency concerns. In this study, the half-bridge module and neutral point clamping (NPC) module are combined to derive an advanced hybrid-bridge transformerless inverter, which not only suppresses leakage current, but also reduces the required bus voltage compared to the conventional half-bridge or NPC inverters. A sinusoidal pulse-width modulation strategy without dead time is presented to enhance both the grid-connected power quality and system reliability. Furthermore, a detailed circuit performance comparison and practical evaluation are presented to show the clear advantages of the hybrid-bridge transformerless inverter. It also provides practical solutions for the leakage current minimisation by considering the contributing factors such as circuit parasitic parameters. Finally, a 3 kW prototype is tested to verify the theoretical analysis and main contributions of the study.