Inverter topology with unipolar modulation of single-phase transformerless inverter topologies for grid-connected photovoltaic applications

During the last decade, extensive advancements have been achieved in the research and technological development of grid-integrated photovoltaic (PV) systems. Among the essential components of such systems, the grid-connected inverter serves as the key interface that enables effective power transfer from renewable energy resources to the utility network. The rapid expansion of the solar energy sector has particularly accelerated innovation in single-phase transformerless inverter configurations designed for grid-connected PV applications. These inverter structures have attracted considerable attention because they eliminate the need for bulky line-frequency transformers while maintaining high performance standards.
Compared to traditional transformer-isolated inverters, transformerless topologies provide significant advantages, including lighter system weight, reduced installation and production costs, compact architecture, simplified circuitry, and improved power conversion efficiency. In these systems, electrical isolation can be achieved by incorporating additional switching devices either at the DC input stage or at the AC output stage. However, inverter configurations employing isolation techniques on the AC side generally demonstrate superior efficiency, primarily due to fewer semiconductor devices in the active current path, which results in lower conduction and switching losses.
This study presents a H4 Inverter topology with unipolar modulation of single-phase transformerless inverter topologies for grid-connected photovoltaic applications.