Control of harmonic current in power systems with hybrid active filters

Abstract

Consulta en la Biblioteca ETSI Industriales (7825)

[EN] Non linear loads and sources like HVDC converter are able to distort the network voltage due to their harmonic currents. The voltage distortion can be reduced by means of conventional passive filters. These circuits are usually designed as shunt elements creating a low impedance path for harmonics to be filtered. The filter is build up as a resonant circuit consisting of capacitor(s) and inductor(s) and in many cases also resistor(s) for a better damping behavior of the filter. The characteristics of a passive filter can significantly be improved by means of a series connected voltage source which is usually realized by a voltage source inverter (VSI). The circuit is then called a hybrid active filter, which is able to control the harmonic currents in the circuit. A well known control concept for a single tuned hybrid active filter is working with simple PI-controllers guarantying high control dynamic for one harmonic current. In the Final Project this control concept has to be developed for the simultaneously control of different harmonic currents. This project deals about the great development that active filters has taken part in the last twenty years, about why is necessary the fast control in the harmonic filters, and why active filters displace to the passive filters. In a first part both filters will be described, explaining for each one advantages and disadvantages. In this first part it will be described too in which fields are commonly used and how can a passive filter become an active with a suitable control. In the second part, a practical simulation will be shown and described by using typical values given at the practice in a network, such as voltage, current, power, impedances, etc. In this part successive simulations becomes more complicated, in order to add several elements that makes the response faster and clear (no dangerous oscillations for the system). The intention of this document is to describe each of these elements or systems , as well as to explain his function, and show how the introduction of these makes the performance of the response better (or not). All the simulations will be made it with the graphic user interface computer program Matlab Simulink¿, in MS Windows Vista¿ operating system