Estratégias de modulação aplicadas a conversores Split Source para a redução de correntes de modo comum em sistemas fotovoltaicos conectados à rede

Abstract

In view of the increase use of alternative energy sources, new technologies are necessary to ensure the quality of those in the insertion to the electrical grid or the power suply of isolated loads. One of the sources with greater exploration in Brazil is the photovoltaic generation. This generation modality supplies at the input terminals a direct current signal, requiring the use of electrical inverters to the power transfer. New topologies and strategies for inverters has been recently developed, directed toward photovoltaic generation. A classic photovoltaic system count with a cc-cc boost converter, a inverter and a transformer. The transformer is required to provide galvanic insulation, which avoids leakage currents. The Split-Source Inverter { SSI has been recently proposed as a topology that dispenses the use of a boost converter cc-cc. The topology has the same number of active Keys of a conventional invertor, three additional diodes and eight comute states. In order to reduce or eliminate leakage currents without a transformer, modulation strategies that aim low common mode voltage variations may be employed. However, SSI has certain limitations in the inverter states due to its operational characteristics, which make di_cult the implementation of modulations with low common mode voltage. The Simpli_ed Split Source Inverter - S3I has a single state conversion dc-ac with boost compatibility. In the S3I, the three additional diodes present in SSI are replaced for an active key. When compared of the SSI, a three-phase version of the S3I has greater exibility in the inverter states, which enables greater reduction in common mode voltage. Therefore, this paper presentes two space vector modulation strategies for both topologies: two space vector modulation strategies using all inverter states and two modified space vector modulation strategies with low common mode voltage.