Retificadores trifásicos três níveis em modo de condução descontínua para geração eólica de baixa potência

Abstract

Electricity generation from renewable sources has grown considerably in recent years, and wind generation has gained prominence. Wind generation at low powers, however, did not follow this growth rate due to a series of adversities, as a lack of knowledge of its existence and of research on the characteristics of winds. This master’s thesis addresses and try to solve one of these adversities in particular: the issue between cost and performance in the three-phase rectifiers needed. Existing classic three-phase rectifier topologies are not suitable for low-power wind generation, either due to performance problems, such as high efforts on the semiconductors or high harmonic distortion rates, or due to technical issues, such as insufficient voltage static gain or reduced reliability, or due to high costs in relation to the power level. Thus, the objective of this work is the investigation and development of new three-phase rectifier topologies suitable for use in low-power wind generation. Through theoretical studies, a new family of rectifiers, which includes original converters as well as converters already studied in other works, is idealized, and proposed. A method for designing the components of the members of this family is also developed. Members of this new family employ only two switches and operate in discontinuous conduction mode, thus eliminating the need for input current control to achieve high power factor. They are low-cost, high-reliability converters that, due to the multilevel configuration and the interleaved operation of the switches, have reduced electrical efforts on semiconductors. The theoretical analyzes developed are verified and validated by simulations and by a prototype of one of the original three-phase topologies, the three-level rectifier with modified SEPIC, investigated in more detail. The prototype, with peak voltage in the supply phases of 90 V, output voltage of 622 V and rated power of 1000 W, presented a good performance: unity power factor, low harmonic distortion rates and high efficiency (95,4 %). Based on all the information obtained, it is possible to verify that members of this new proposed family, such as the prototype rectifier, are suitable for use in low-power wind generation.