Hybrid-bridge transformerless photovoltaic grid-connected inverter

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.