Análise dos métodos de determinação das correntes de compensação em filtros ativos

Abstract

Not only distorted voltage and current waveforms, but also unbalanced systems are commonly found on power systems, notably due to the increasing number of single-phase non-linear loads. These phenomena may be mitigated by shunt active power filters (SAPF). In order to reduce the negative impact of distortions and unbalances in the electrical system, the active power filter synthesizes a compensation current waveform, which eliminates possible disturbances inserted into the system, especially those related to single-phase non-linear loads. In this scenario, the present work investigates two different methods of synthesizing the electrical current through SAPF: (i) sinusoidal current and (ii) unity power factor method. The first method is based on the injection of compensating currents in such a way that the line current becomes perfectly sinusoidal. In the second method, the line current is adjusted to have a waveform which is a replica of the voltage waveform, so that the set of the nonlinear load and the active filter behave as a nonlinear load of unity power factor. In this way, the purpose of this study is to determine which of the two methods presents the best performance in terms of harmonic mitigation, reduction of voltage unbalances and in a better use of the system as well. Aiming this purpose, the mathematical modeling of both methods was carried out and several simulations using Matlab-Simulink were performed. The obtained results suggest that depending on the purpose the unity power factor methodology is better than the sinusoidal current methodology.