International Journal of Power Electronics and Drive Systems (IJPEDS) Vol. 13, No. 3, September 2022, pp. 1486~1497 ISSN: 2088-8694, DOI: 10.11591/ijpeds.v13.i3.pp1486-1497  1486 Journal homepage: http://ijpeds.iaescore.com Minimization of total harmonic distortion in neutral point clamped multilevel inverter using grey wolf optimizer Fahmi Ahyar Izzaqi, Novie Ayub Windarko, Ony Asrarul Qudsi Electrical Engineering Department, Politeknik Elektronika Negeri Surabaya, Surabaya, Indonesia Article Info ABSTRACT Article history: Received Mar 18, 2022 Revised May 22, 2022 Accepted Jun 15, 2022 The inverter has been attracting researchers for their application in renewable energy. So far, multilevel inverter is considered as low distortion class, which produces multilevel output voltage imitating a pure sine waveform. However, the needs for free distortion of output voltage have been motivating to improve multilevel pulse width modulation PWM generation method. In this paper, the modified PWM technique is proposed to reduce the voltage total harmonics distortion (THD) of multilevel inverter. This modulation technique is then applied to control a single-phase three- level neutral point clamped multilevel inverter (NPC-MLI). Grey wolf optimizer (GWO) algorithm is utilized to generate optimal amplitude and phase shift of modified reference signal. The GWO algorithm is then compared with other optimization algorithms such as differential evolution (DE), human psychology optimization (HPO), and particle swarm optimization (PSO) to evaluate their performance in harmonic minimization. The performance of the proposed work is validated through simulation and experimentation on a prototype. The results show that the modified PWM technique optimized with GWO can reduce THD on NPC-MLI output voltage. Keywords: Grey wolf optimizer Modified PWM Multilevel inverter Optimization algorithm Total harmonic distortion This is an open access article under the CC BY-SA license. Corresponding Author: Fahmi Ahyar Izzaqi Electrical Engineering Department, Politeknik Elektronika Negeri Surabaya ITS Raya st, Keputih, Sukolilo, Surabaya, East Java 60111, Indonesia Email: fahmizzaqi@pe.student.pens.ac.id 1. INTRODUCTION Since several decades ago, multilevel inverter multilevel inverter (MLI) has been attracting to convert direct current DC voltage to alternating current AC voltage in renewable energy applications [1]. The MLI are widely used as voltage converters from renewable energy source such as solar panels, wind turbines and others, to supply electricity to AC loads in stand-alone systems [2] or to the grid-connected [3]. High efficiency power conversion systems are expected to deliver high performance by reducing conduction losses in the switching process and reducing total harmonics distortion total harmonics distortion (THD) [4]. So far, MLI is well known has low voltage distortion and can operate at high power and high switching frequency [5]. Under ideal condition, the MLI should provide pure sine wave for electric loads. The MLI can produce staircase output voltage which close to a sinewave form. However, the MLI’s staircase output voltage is non ideal sine wave and still contains harmonics due to the switching pattern generation [6]. To overcome this issue, many type of MLI has been developed includes cascaded H-Bridge MLI, flying capacitor MLI, and neutral point clamped multilevel inverter neutral point clamped multilevel inverter (NPC-MLI) [7]. Due to MLI circuit complexity, several researchers have proposed to reduce the number of MLI’s components [8]. Nevertheless, the NPC MLI has advantages of easy control and low cost hardware implementation among the MLIs [9].