Filtros ativos: implementação prática a partir da plataforma dSPACE

Abstract

The constant growth of electricity demand and the nonlinear characteristics of loads have made the search for power quality increasingly urgent. Several consequences of the operation of some equipment deteriorate the quality of the power grid, causing distortions such as direct current offset, noise, interharmonics and harmonics. The harmonics, which has particular attention in this paper, is the subject of rules that aim to determine limits to its quantity in a system, wich can make consumers pay fines when not observed. Harmonic mitigation solutions include passive, shunt and hybrid filters. The active filter shunt was the solution chosen in this work to reduce the harmonic currents of electrical systems, compensating the demanded current by the load in the way that the grid current can follow the sinusoidal and balanced behavior pattern in a three phase system. To control the filter converter, it is necessary to obtain the reference currents, which was done by applying the real and imaginary instantaneous power Theory. This work proposed, through a practical approach using the dSPACE platform, the implementation of an shunt active power filter using instantaneous power Theory to reduce the effects of harmonics current drained from the grid by a nonlinear load. At first it was used a nonlinear load configuration containing a three-phase rectifier bridge, which had resistive components on its DC bus, in parallel with an unbalanced resistive load. It was possible to reduce the current THD in the three phases, a, b and c from 17.04%, 15.77 % and 14.97 % to 6.42%, 5.99%, and 5.99%, respectively. Then, it was used a second load containing a power transformer and a three-phase rectifier, which had an RC load on its DC bus. It was possible to reduce the current THD in the three phases, a, b and c from 42.66%, 45.75% and 39.36 % to 11.69 %, 13.48 % and 13.18 %, respectively. Therefore, it was possible to reduce the level of harmonic current distortion for two different types of load, thus improving the power quality of the proposed circuit configurations.