International Journal of Electrical and Computer Engineering (IJECE) Vol. 14, No. 2, April 2024, pp. 1274~1286 ISSN: 2088-8708, DOI: 10.11591/ijece.v14i2.pp1274-1286  1274 Journal homepage: http://ijece.iaescore.com Transient response mitigation using type-2 fuzzy controller optimized by grey wolf optimizer in converter high voltage direct current I Made Ginarsa 1 , I Made Ari Nrartha 1 , Agung Budi Muljono 1 , Osea Zebua 2 1 Department of Electrical Engineering, Faculty of Engineering, University of Mataram, Mataram, Indonesia 2 Department of Electrical Engineering, Faculty of Engineering, Lampung University, Metro Lampung, Indonesia Article Info ABSTRACT Article history: Received May 15, 2023 Revised Dec 5, 2023 Accepted Dec 13, 2023 Long high voltage direct current (HVDC) transmission link is commonly used to transmit electrical energy via land or under-sea cable. The long HVDC avoids reactive power losses (RPL) and power stability problems (PSP). On the contrary, the RPL and PSP phenomena occur in long high voltage alternative current-link (HVAC) caused by the high reactive component in the HVAC-link. However, the HVDC produces a high and slow transient current response (TCR) on the high value of the up-ramp rate. Interval type-2 fuzzy (IT2F) control on converter-side HVDC is proposed to mitigate this TCR problem. The IT2F is optimized by grey wolf optimizer (GWO) to adjust input-output IT2F parameters optimally. The performance of IT2F-GWO is assessed by the minimum value of integral time squared error (ITSE), peak overshoot, and settling time of the TCR. The IT2FC- GWO performance is validated by the performance of IT2F control that is optimized by genetic algorithm (IT2F-GA) and proportional integral (PI) controller. Simulation results show that the IT2F-GWO performs better with small ITSE, low peak overshoot, and shorter settling times than competing controllers. Keywords: Converter control Grey wolf optimizer High voltage direct current Transient response mitigation Type-2 fuzzy This is an open access article under the CC BY-SA license. Corresponding Author: I Made Ginarsa Department of Electrical Engineering, Faculty of Engineering, University of Mataram Majapahit Street, No. 62, Mataram 83125, Nusa Tenggara Barat, Indonesia Email: kadekgin@unram.ac.id 1. INTRODUCTION Transmission system is vital in a power system industry to deliver the electrical power/energy from power plants to consumers through distribution systems. Transmission systems categorized into alternating current (AC) and direct current (DC) types, according to the international electrical commission (IEC) standard regulation. Electrical energy delivered via high voltage direct current (HVDC) technology in modern transmission systems. This HVDC technology has intrinsic advantages such as being more favorable to install on very long distances for overhead or/and submersible transmissions, do not have reactive power losses, being feasible to connect for difference frequency systems (50/60 Hz), and having no stability issues appear in very long-distance transmission application. These advantages make the HVDC more convenient to implement than its competing (high voltage alternating current (HVAC)) technology. By using the newest power semiconductor technology, the AC/DC/AC converter process is more effective, efficient, and affordable in cost to be implemented. Moreover, ultra HVDC (UHVDC) transmission is a new technology that increases power capacity delivery, decreases electrical energy losses, and reduces of circuit-lines [1]. Some control and protection schemes for fault types in HVDC are provided in [2], [3]. A control scheme