International Journal of Electrical and Computer Engineering (IJECE) Vol. 10, No. 6, December 2020, pp. 5609~5620 ISSN: 2088-8708, DOI: 10.11591/ijece.v10i6.pp5609-5620  5609 Journal homepage: http://ijece.iaescore.com/index.php/IJECE Time-domain harmonic extraction algorithms for three-level inverter-based shunt active power filter under steady-state and dynamic-state conditions-an evaluation study Ali Saadon Al-Ogaili 1 , Agileswari Ramasamy 2 , Yap Hoon 3 , Renuga Verayiah 4 , Marayati Marsadek 5 , Tengku Juhana 6 , Nur Azzammudin Rahmat 7 1,5 Institute of Power Engineering (IPE), Universiti Tenaga Nasional, Malaysia 2,4,6,7 Department of Electrical and Electronics Engineering, Universiti Tenaga Nasional, Malaysia 3 School of Engineering, Faculty of Innovation and Technology, Taylor’s University, Malaysia Article Info ABSTRACT Article history: Received Jul 18, 2019 Revised Mar 5, 2020 Accepted Mar 17, 2020 Power quality is a major consideration in all office equipment, manufacturies and residential home appliances. Harmonic distortion is one of the crucial power quality issues. In order to mitigate the harmonic distortion, the performance of shunt active power filter (SAPF) is judged in terms of the accuracy and response time of its designed controller. In this context, the controller consists of three parts: harmonic extraction, switching control, and DC-link capacitor. The harmonic extraction technique serves the major role of deriving the required reference current to ensure successful mitigation of current harmonics by SAPF. Among the existing techniques, harmonic extraction algorithms based on time-domain approaches are most widely applied as they offer simple implementation features with increased speed and reduced computational burden. This paper presents detailed investigation and analysis regarding the performance of two famous time-domain harmonic extraction techniques namely, synchronous reference frame (SRF) and instantaneous power (PQ) theory. Extensive simulation work is conducted in MATLAB-Simulink platform under two conditions, which are, steady-state conditions and dynamic-state conditions, considering various highly nonlinear loads. For evaluation purposes, each control algorithm is incorporated into the controller of a three-phase SAPF, developed using a three-level neutral-point-clamped (NPC) inverter. Comprehensive results are provided to confirm mitigation performance of the SAPF utilizing each harmonic extraction algorithm. Keywords: Active power filter Current harmonics mitigation DQ Theory Multilevel converter Power quality PQ theory Copyright © 2020 Institute of Advanced Engineering and Science. All rights reserved. Corresponding Author: Ali Saadon Al-Ogaili, Institute of Power Engineering (IPE), Universiti Tenaga Nasional, 43000 Kajang, Selangor, Malaysia. Email: alinasrieh.edu@gmail.com 1. INTRODUCTION Extensive applications of harmonic-producing loads have posted severe power quality issues especially low power factors and high harmonic distortion to electricity grid. This has raised alerting concerns among researchers in formulating efficient solution. Among the state-of-art-techniques, SAPF is the most powerful technique for solving current harmonics [1-3]. Additionally, it also improves power factor (PF) performance of power system by ensuring in-phase operation of source current with its corresponding source voltage. Generally, SAPF recovers the sinusoidal characteristics (with fundamental frequency) of the source current, by injecting a corrective current back to the polluted power system.