Active Power Filter Controller for Harmonics Mitigation of Nonlinear Loads

Abstract

The paper addresses the problem of the synthesis of a controller which removes harmonics from nonlinear loads connected to the power network. Non-linear loads, for example containing thyristor circuits, behave in an asymmetrical manner, introduce reactive power and generate harmonic power components, at a frequency that is a multiple of the power grid frequency. While reactive power compensators are designed for the basic grid frequency, the elimination of harmonic components requires tuned circuits designed independently for each harmonic. The article presents the application of an Active Power Filter (APF) for the removal of selected harmonics so that the spectrum of the load current remains within the required limits. Such an approach allows replacing multiple passive filters of a given fixed bandwidth by a single active device, in which compensation bandwidth is tuned in a programming manner. The APF controller is designed as Simulink diagram, which is next applied for the automatic generation of the real-time control application. The experiments show that the amplitude of the selected harmonics is mitigated to a level of 5%–10% of the initial value. This results in a fourfold decrease in the Total Harmonic Distortion index of the load current.