Comparison of transformerless converter topologies for photovoltaic application concerning efficiency and mechanical volume

Three transformerless converters for three phase solar applications are compared concerning efficiency, leakage current and mechanical volume. The investigated topologies are the voltage source inverter (VSI), the three level neutral point clamped (NPC) inverter and the z-source inverter (ZSI). Therefore the topologies are introduced and the working principles are explained. The power losses, the resulting leakage current at the pv array and the volume of the inverter are investigated mathematically, by simulation and experimental measurements. From the efficiency point of view the NPC has the best performance followed by the VSI and ZSI. The leakage current is for all topologies acceptable.