Abstract

Subject of the present diploma thesis is the study and construction of a device for eliminating the noise produced by small locally-made wind turbines in autonomous systems. The noise source is initially assumed, and then proved, to be electromagnetic. Having that in mind, several methods of current conditioning are studied including passive filter topologies, other passive methods of harmonic current reduction, active filters and other devices that provide full control of the generator.

At first, the operation principals of an uncontrolled three-phase diode bridge rectifier are presented and analyzed, as well as the harmonic current that naturally occurs which conclusively is the source of the problem. Thereafter, a review is carried out of every method passive or active that is been used in the industry and results in the conditioning of wind turbine current and harmonic compensation.

Subsequently, the most basic of these are modeled and then simulated in order to study the characteristics they offer to the overall system. Active topologies, their operation principles, control strategy as well as their fundamental design factors are analyzed. Special emphasis is given to passive filters topologies, which are finally selected. After comparing the simulation results, the final choice of the appropriate device is made, that is a passive forth degree filter of L-LC-L topology. An essential parameter in choosing and designing the filter, consists of a minimal effect on the wind turbine power curve.

One of the main objectives of this diploma thesis is the creation of a calculation and design method of the selected filter topology as well as a construction process. For this reason, great importance is given to the experimental verification of the studied, simulated and finally applied arrangements. Experimental results have validated the accuracy of the construction process on the one hand, and the design method on the other. These have taken into account the final acoustic noise measurements in the field and the level of the remaining harmonic current components, which were compared with corresponding simulation results.

Key words: diode rectifier, current harmonics, harmonic reduction techniques, passive filters, active filter, bidirectional six-switch active rectifier, passive filter design

Author: Ilias Katsampiris

Responsible PhD: Athanasios Vassilakis / avassil@mail.ntua.gr and Kostas Latoufis / latoufis@power.ece.ntua.gr

Supervising Professor: Nikos Hatziargyriou / nh@power.ece.ntua.gr

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