Publication - Development and implementation of algorithms for harmonic identification and control applied to shunt active power filters - Group of Electronic Engineering Applied to Renewable Energy Systems
 

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Publications Master Thesis

Development and implementation of algorithms for harmonic identification and control applied to shunt active power filters

Research Area: Year: 2010
Type of Publication: Master Thesis
Authors:
Abstract:
This Master Thesis is focused on the field of current control for shunt active power filters. This is a field in constant development and innovation, since the number of nonlinear loads that are connected to the grid is growing thanks to the rise of new technologies. Different algorithms are studied in order to implement the current control of a shunt active filter. Broadly speaking, two types of controllers are studied: (1) Proportional-resonant controllers based on second order generalized integrators, and (2) repetitive controllers. Within this general classification, different implementations are studied based on several studies, their characteristics are analyzed and their advantages and disadvantages are discussed. Their behavior is analyzed both in normal operation conditions and in anomalous conditions like, for example, when drifts occur in the nominal values of the plant parameters and in the fundamental frequency of the grid. This analysis is useful for choosing one or another controller depending on the system where it is to be used, since operating margins are obtained for each controller and the errors are compared in each case. In addition, the response of these controllers is analyzed in a three-phase three-wire and four wire system, talking about the implementation details in each case. To perform this step, an analytical study of the plant model for both three-wire and four-wire systems is previously made. To discuss the simulations obtained in the two types of systems, comparative analysis is based on the parameter THD (Total Harmonic Distortion) and on temporal representation of grid current, load current and filter current, so that the effectiveness of the active filter to leave the grid to supply only the fundamental harmonic is demonstrated. Active filters also have the ability to correct the power factor of a system, which is demonstrated with a simple example in which a capacitive load is connected to the Point of Common Coupling (PCC) and finally the grid voltage and grid current are in phase, resulting in a power factor close to 1. Since one of the problems of existing current controllers is their high sensitivity to changes in grid frequency, three methods for estimating the frequency are explored, which will serve to develop frequency-adaptive current controllers. Their performances are compared when a frequency step is applied, basing the study on parameters such as settling time of the algorithm and highest error obtained. Finally, the conclusions drawn from this work and the future works are presented.
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