Filtros ativos para sistemas equilibrados e desequilibrados.

Abstract

This Thesis deals with the modelling and control of the Active Filter in electric power systems that have three and four wire. The Active Filter is composed by a shunt PWM voltage source converter to compensates the current of the grid in a industry plant. The compensation of the grid current encompasses homopolar, reactive, negative sequence and harmonic components. This compensation provides that the grid current comes to be sinusoidal, balanced and synchronized with the grid voltage. Thus, we explore some control techniques which can assurethese conditions to the feder currents, even under unbalanced conditions of the load or the grid impedance . The study presents control strategies that allow to enlarge the strenght of the shunt Active Filters in case of ocurring rigorous disturbance such as: elimination of functioning of one of branch of the converter; breach of the connection of one of the branch of grid; and when the voltage source converter presents limitation to your operation which brings a loss of one phase. The redundances of the structure of the converter with four branchs are explored by keeping the system in operation up to the point of its possible interruption to the necessary retifications. According to the findings of the study i t will not possible to compensate all the components of the current required by the load, as for exemple, the component of zero sequence. This proposition means a relevant advantage, mainly if applied to industrial systems, where one of the disturbances may imply in instantaneous and prolonged interruption of all process, providing serious demages. For the base and context of the proposal (In order to make the results showed clearer), it is presented a study of stead state about the application of Active Filters to compensate the power factor and control of the voltage regulation of the bus of the entrance in one industrial system, the point of couppling comon (PCC). This study, besides demonstrating the behavior of the compensator, faces the variations of important parameters, as the active and reactive powers demanded by the load. It also provides an analysis of the advantages, as well as the necessary investiment to choose one of the discussed options. The control structures used in the simulations and experiments are also presented in order to facilitate their understanding.