Reference Current Generation for Active Power Filtering in Single-phase Power System
A new proposed STF-FCE algorithm is developed to replace the conventional SRF algorithm for a better performance of SAPF to mitigate the harmonic currents. The objectives are to obtain THD values with 5% limit and lower ripple content in the fundamental current before generating the reference current.
Power quality and stability of system can be greatly affected by the amount of harmonic distortions in a power network. Hence, shunt active power filter (SAPF) is developed to mitigate harmonic currents in the AC networks. Reference current generation algorithm is the most important control process based synchronous reference frame (SRF) algorithm to control SAPF as it has the simplest implementation features. However, the reference current generated from the conventional SRF algorithm suffers from some delays and inaccuracy as the fundamental element contains high ripple currents which would lead to noise in the system. Hence, a proposed STF-based fundamental component extraction (STF-FCE) algorithm is implemented for the major improvements such as the removal of the unnecessary cosine function to reduce complexity of algorithm, employment of self-tuning filter (STF) to extract accurate fundamental component and to generate a sinusoidal reference current. The purpose of developing STF-FCE algorithm is to generate a fast and efficient fundamental reference current to operate the SAPF in reducing the harmonics content of the power system. MATLAB-Simulink is used to design and evaluate the proposed STF-FCE algorithm as well as the conventional SRF algorithm for comparison purposes under steady state conditions when an ideal voltage source is connected. The THD values can be observed through the FFT analysis and it has reduced from 5.06% to 3.06% by tuning the gain of STF to a lower value. The ripple currents has shown improvement when the fundamental elements have lesser ripple contents compared to conventional SRF algorithm. The simulation results obtained had proved success when the proposed STF-FCE algorithm has shown improvement of performance when compared to conventional SRF algorithm in terms of total harmonic distortions (THD) and ripple contents in the fundamental elements.