Resumen de Elininación de perturbaciones de baja frecuencia en redes eléctricas mediante compensadores estáticos
The increasing use of DC electronic devices connected to mains lead to numerous complications of harmonic distortion and efficiency reduction in electrical energy transmission. These devices behave as a marked non linear lads, which behavior lie in their topology and structure, but also in mains impedance as well as the neighbor loads impedance. In order to correct this situation, these loads can be modified or filters can be introduced. Filters are usually connected in parallel to de loads, to reduce harmonic generation. These filters can be active or passive. This thesis is devoted to parallel active filter topology and control method study; it also analyses and the filter behavior as soon as they are connected to the mains. More specifically, the thesis is focused in to hybrid filters study, coupled to the mains by a passive LC filter. The main contributions of this thesis, one and all supported by publications, are: a) Filter Topology: Various filter topologies show several problems, which are explained in detail on the document. Hybrid filter coupled to the mains by passive LC filters is adopted in this thesis and a new topology called "Neutral to Negative" (NtN) is proposed. This topology uses only one capacitor in the DC bus and therefore removes the DC balance requirement characteristic of split capacitors VSI topologies. b) Control and PWM modulation techniques: In these area contributions are concentrated in two features; a transformation based on 60º angles is proposed by contrast of the classic aß orthogonal transformation. This adaptation considerably simplifies to procure the VSI stages in case of systems without neutral wire. Furthermore a current controller and modulation technique has been developed to follow current track, in three and four-wire mains. c) Leading current control: A new method to reduce leading current in low load conditions has been developed. This method regulates the available voltage across coupling capacitors in order to obtain a specific di/dt; and is operational without losing filter properties. d) Non linear loads model: Harmonic filter introduction in power lines disturbs non-linear-loads (NLL) behavior and produce some harmonic amplification problems introduced in the last chapter. This chapter is devoted to obtain a NLL model in order to predict the load response when a filter is introduced. A model based in Neural Networks (NN) has been developed. This model is created making use of measure collection made where the filter is going to be connected. This NN model has been completed with an iterative method allowing to predict harmonic current changes in NLL when an active filter is connected.
