Analysis of Terminal Voltage in Single-Phase Extended Three-Phase Transformerless PV Inverter Topologies

In this article, an insight view for the derivation of various existing three-phase transformerless PV inverter topologies which are extended from the single-phase configuration is presented. In this article, the topologies under the four categories like dc decoupled, ac decoupled, neutral point clamped (NPC) dc decoupled, and NPC ac decoupled of single-phase transformerless photovoltaic (PV) inverter configurations are considered and their extended three-phase configurations are given. Furthermore, the analysis of the terminal voltage for each three-phase PV inverter topology is also presented. The analysis given in this article is expressed using the switching function concept. The analytical waveforms obtained using the mathematical switching function equation is matching with the simulation results presented. In addition, the obtained analytical and simulation results are further supported with the experimental results from the developed lab prototype. Finally, a comparison is done for the considered three-phase transformerless inverter topologies in terms of the number of switches and diodes used, the number of switches and diodes conducting, etc.