Reference Current Generation for Active Power Filtering in Single-phase Power System
The paper presents a new proposed reference current generation algorithm based synchronous reference frame (SRF) to mitigate the harmonic currents in single-phase inverter-based shunt active power filter (SAPF) for an active power filtering purpose. SAPF is often used in the AC networks due to its superiority in dynamic-state conditions. The proposed algorithm known as STF-based fundamental component identifier (STF-FCI) algorithm is implemented for major improvements and few modifications of the algorithm are made. The modifications are: (1) employment of self-tuning filter (STF) to extract accurate fundamental component and to generate a sinusoidal reference current (2) replacement of low pass filter (LPF) and (3) removal of the unnecessary cosine function to reduce complexity of algorithm. The purpose of developing STF-FCI algorithm is to generate a fast and accurate fundamental reference current to operate the SAPF and provide a fast response time in the dynamic-state conditions. The algorithm is conducted under both steady-state where the non-linear load is connected with capacitive (RC) load or inductive (RL) load and under dynamic condition where the non-linear load change from capacitive load to inductive load. The performance of steady-state condition will be evaluated in terms of THD values, ripple factor, power factor and phase difference. Under dynamic-state condition, the dynamic speed will be evaluated to capture the speed of the amplitude change in non-linear load in a period of time. MATLAB-Simulink is used to design and evaluate the proposed STF-FCI algorithm by using the Simpower System toolbox. There are few comparisons made with the proposed algorithm in this paper: (1) SRF algorithm and the STF-FCI algorithm are compared under steady-state and dynamic conditions in order to prove the effectiveness of using STF-FCI algorithm; (2) Mean algorithm in STF-FCI algorithm and LPF algorithm in SRF algorithm will be evaluated for comparison purpose. All of the algorithms will be tested under ideal and distorted voltage in all conditions. The simulation results had shown the major development when THD values, ripple factor, power factor and phase difference are reduced. The response time of the changing load is shortened when mean algorithm is applied when compare to LPF algorithm. The simulation results proved success when the pro-posed STF-FCI algorithm using mean algorithm are better than SRF algorithm using LPF algorithm in steady-state and dynamic conditions under two voltage conditions i.e. ideal and distorted voltage.