J Electr Eng Technol.2017; 12(1): 151-160 http://dx.doi.org/10.5370/JEET.2017.12.1.151 151 Copyright ⓒ The Korean Institute of Electrical Engineers This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Three-Phase Reference Current Generator Employing with Kalman Filter for Shunt Active Power Filter Ahmad Shukri Abu Hasim † , Zulkifilie Ibrahim*, Md. Hairul Nizam Talib* and Syed Mohd. Fairuz Syed Mohd. Dardin** Abstract – This paper presents a new technique of reference current generator based on Kalman filter (KF) estimator for three-phase shunt active power filter (APF). The stationary reference frame (d-q algorithm) is used to transform the load currents into DC component. The harmonics of load currents are extracted and the three-phase reference currents are generated using KF estimator. The work is simulated using Matlab/Simulink platform. To validate the simulation results, an experimental test-rig have been perform using real-time control dSPACE DS1104. In addition, hysteresis current control was used to generate the switching signal for the correction of the harmonics in the system. The non- linear load were constructed with three-phase rectifier which connected in series with inductor and parallel with resistor and capacitor. The results shows that the new technique of shunt APF embedded with KF is proven to eliminate the harmonics created by the non-linear load with some improvement on the total harmonics distortion (THD). Keywords: Active power filter, Harmonics, Kalman filter estimator, Non-linear load 1. Introduction Harmonics interference in power system become increasingly critical due to the wide application of power electronic equipment of non-linear load and harmonics contamination that affects the power quality of the system. Various methods have been proposed to solve these problems. One of the method is by using passive filter which connected in parallel with non-linear loads (NLL) resulting in the improvements of the power factor [1], harmonic suppression [2] and exhibit lower impedance at a tuned harmonics frequency [3]. This approach is popular due to its simplicity, reliability, efficiency and low cost [4], but at the expense of providing incomplete solutions particularly when compensating random frequency variations in the current, tuning and parallel resonant problems. In recent years, various active power filters (APF) configuration with their respective control strategies have been proposed and have been recognized as a viable solution to the problem created by harmonics [5-7]. Amongst the technique that have been developed are the extraction and the estimation approach. Instantaneous reactive power theory (p-q theory), modified p-q theory [8-10], p-q-r theory [11, 12], vectorial theory [13] and d-q theory [7, 14, 15] are the techniques that fall into the extraction technique. In many cases, d-q algorithm have been widely used to eliminated the harmonics due to its simplicity of control design relative to the rest [6]. On the other hand, estimation approach is used to estimate harmonics of frequency component present in the signal and measurement or estimation of the amplitude and phases of those frequencies [16]. These approach can be divided into two classes, non-parametric and parametric methods. The non-parametric methods are based on transformation of the given time-series data sequence. During the estimation process, this methods are not capable of incorporating with any available information about the system. Frequency domain approach using Fourier transform is the most commonly used for spectrum analysis in this harmonics estimation [16]. In addition, parametric methods use an appropriate model to represent the signal and then estimate the parameters of the model from the available data points. Estimated parameter are applied to the selected model to determine harmonics contents in the signal. This parametric methods offer higher resolution and better accuracy compared to the non-parametric methods [16]. KF estimator is one of the methods that fall into the parametric method category which have been widely studied and used for different applications [16-23]. In active power filter, KF is used to estimate and track the current harmonics of the grid which reported in [24-26]. In this technique, it is assume that the frequency of the grid are constant and its only detect the harmonics in the system. Furthermore, the DC NLL have been used by many researchers to generate the distorted current waveform [5, 27-31]. Generally, the NLL is constructed using combination of resistor, inductor and † Corresponding Author: Dept. of Electrical and Electronic Engineering, Universiti Pertahanan Nasional Malaysia, Malaysia. (shukri@upnm.edu.my) * Faculty of Electrical Engineering, Universiti Teknikal Malaysia Melaka, Malaysia. ({drzulkifiliee, hairulnizam}@utem.edu.my) ** Dept. of Electrical and Electronic Engineering, Universiti Pertahanan Nasional Malaysia, Malaysia. (syedfairuz@upnm.edu.my) Received: February 25, 2016; Accepted: July 18, 2016 ISSN(Print) 1975-0102 ISSN(Online) 2093-7423