Evaluation of large-scale photovoltaic applications with multilevel converter cascade transformerless

This paper presents a evaluation of the transformerless Cascaded H-bridge (CHB) multilevel converter applied a large-scale photovoltaic (PV) plants. One the major problems in transformerless application is leakage current formed by the parasitic capacitance of the PV panels. This problem affect the security and quality of system. Most studies presents the solution based in common mode voltage, but in CHB multilevel converter is little different. The system model with a parasitic capacitance is detailed and a relation show the voltage across the parasitic capacitance is presented. The leakage current is detailed in topology in study and two loop of the circulating current is showed. The comparison about the leakage current between the mainly PWM techniques applied the CHB is presented and discussed.