A comprehensive review of three and five level transformerless inverter topologies based on component count and their performance

Abstract In solar photovoltaic (SPV) applications, transformerless grid-tied inverters have garnered significant research interest because of several promising characteristics such as higher efficiency, tolerable power density, lightweight design and affordability. Among the different types of grid-tied SPV inverters, transformerless multilevel inverters (MLI) stand out as particularly popular. This popularity stems from their capacity to transmit reactive power effectively, their common-ground (CG) configuration, which helps in mitigating the detrimental effects of leakage current caused by the parasitic capacitances of the PV array and their ability to accommodate smaller size filters for minimizing total harmonic distortion (THD). Several transformerless inverter (TLI) concepts have emerged in recent times to effectively eliminate leakage current. These approaches employ various strategies that include decoupling the DC from the AC side, implementing clamping mechanisms for controlling common mode voltage during the freewheeling phase, and adopting CG configurations. Over the years, numerous new topologies and configurations came into existence, and it becomes a complex and confusing task while selecting the topology for SPV. Hence, to provide a clear overview of the advancements in TLI for grid-tied SPV systems, this paper seeks to classify and thoroughly review different TLI models. The comparison among the different topologies was conducted based on size, leakage current elimination, THD, total stress voltage, cost functions and other relevant factors. The findings were then summarized in a table for a concise representation of the comparative analysis. This will help researchers in selecting which topology is best for particular SPV application.