Análise, projeto e implementação de um arranjo flexível de conversores estáticos para sistemas de conversão de energia eólica conectados à rede

Abstract

This Thesis deals with the analysis, design and implementation of a flexible arrangement of static converters for grid connected Wind Energy Conversion Systems (WECS). The main features of the proposed flexible arrangement are: (i) expanded reactive power capability limits, (ii) high efficiency mainly under low wind conditions where the active power is reduced, and (iii) low current harmonic content. The proposed arrangement has several operation modes and this Thesis proposes a methodology for selecting the redundant operation modes. This methodology estimates the lifetime of the power semiconductors in order to increase the system reliability of the wind energy conversion system. Furthermore, this Thesis proposes a hybrid modulation strategy for voltage fed converters with multiple parallel magnetically coupled legs. The proposed hybrid modulation strategy combines the benefits of space vector, such as switching sequences flexibility and the simplicity of the modulation based on the geometric approach. As a result, it is possible to obtain multilevel equivalent voltages, as well as the equal sharing among the converter leg currents. In addition, the virtual vector concept is used which leads to the determination of the voltage limits required to impose the equal sharing among the leg currents and to avoid the saturation of the coupled inductor. Experimental results are presented to support the developed analysis demonstrating the performance of the proposed flexible arrangement of converters and the proposed modulation technique.