Conversores multiníveis com aterramento comum para sistemas de geração solar fotovoltaica conectados à rede elétrica

Abstract

Renewable energies have been widely explored in recent years, to the point of contributing considerably to global electricity production. Particularly, photovoltaic solar generation systems connected to the grid can eliminate the need for a transformer. This fact adds to the converter greater efficiency, lower cost and lower volume/weight. However, the common mode voltages generated by the converter can give rise to leakage currents that flow through the parasitic capacitances and filter inductances. These currents must be mitigated in order not to cause damage to equipment and people. Therefore, this work deals with the development of converters that do not require the use of a low-frequency transformer, with common grounding to mitigate leakage current. They are composed of a smaller number of semiconductors compared to other topologies in the same category and synthesize output voltage with five levels. Two converters are proposed: the first converter operates in voltage step-down mode and the other with dual gain possibilities (step-down and step-up). The design of active and passive devices, as well as loss analysis are presented in detail in this dissertation. Space-Vector Modulation is used to generate the power switch command signals and the Proportional Resonant (PR) controller is designed to track the current injected into the network. Furthermore, the performance of the converters was tested through simulations and experimentally with 500W prototypes. Keywords: Photovoltaic solar energy, Multilevel converters, Common-mode voltage, Leakage current.