electronics Article Transient Stability Enhancement of a Grid-Connected Large-Scale PV System Using Fuzzy Logic Controller Md. Rifat Hazari 1, * , Effat Jahan 1 , Mohammad Abdul Mannan 1 and Narottam Das 2,3, *   Citation: Hazari, M.R.; Jahan, E.; Mannan, M.A.; Das, N. Transient Stability Enhancement of a Grid-Connected Large-Scale PV System Using Fuzzy Logic Controller. Electronics 2021, 10, 2437. https:// doi.org/10.3390/electronics10192437 Academic Editors: Jingyang Fang and M. Tariq Iqbal Received: 28 August 2021 Accepted: 5 October 2021 Published: 8 October 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Electrical and Electronics Engineering, American International University-Bangladesh (AIUB), 408/1 Kuratoli, Khilkhet, Dhaka 1229, Bangladesh; effat@aiub.edu (E.J.); mdmannan@aiub.edu (M.A.M.) 2 School of Engineering and Technology, Central Queensland University Australia, Melbourne, VIC 3000, Australia 3 Centre for Intelligent Systems, School of Engineering and Technology, Central Queensland University, Brisbane, QLD 4000, Australia * Correspondence: rifat@aiub.edu (M.R.H.); n.das@cqu.edu.au (N.D.) Abstract: This paper presents a new intelligent control strategy to augment the low-voltage ride- through (LVRT) potential of photovoltaic (PV) plants, and the transient stability of a complete grid system. Modern grid codes demand that a PV plant should be connected to the main power system during network disturbance, providing voltage support. Therefore, in this paper, a novel fuzzy logic controller (FLC) using the controlled cascaded strategy is proposed for the grid side converter (GSC) of a PV plant to guarantee voltage recovery. The proposed FLC offers variable gains based upon the system requirements, which can inject a useful amount of reactive power after a severe network disturbance. Therefore, the terminal voltage dip will be low, restoring its pre-fault value and resuming its operation quickly. To make it realistic, the PV system is linked to the well-known IEEE nine bus system. Comparative analysis is shown—using power system computer- aided design/electromagnetic transients including DC (PSCAD/EMTDC) software—between the conventional proportional–integral (PI) controller-based cascaded strategy and the proposed control strategy to authenticate the usefulness of the proposed strategy. The comparative simulation results indicate that the transient stability and the LVRT capability of a grid-tied PV system can be augmented against severe fault using the proposed FLC-based cascaded GSC controller. Keywords: fuzzy logic controller (FLC); grid side converter (GSC); low-voltage ride-through (LVRT); photovoltaic (PV) system; transient stability 1. Introduction Due to the global warming issues of fossil fuel-based power stations and the increasing cost of energy generation, the presence of large-scale renewable energy sources (RESs) in current power systems has been increasing over the last decade. Among different types of RESs, PV power plants are among the most popular because they are continuously decreasing in price [1–4]. According to Refs. [5,6], the global capacity of installed PV systems was 512 GW in 2018 [5], and it will reach about 1.1 TW in 2022. A recent report showed that China, India, the USA, Japan, and Australia are in the top positions, having installed 44.3 GW, 10.8 GW, 10.7 GW, 6.7 GW, and 3.8 GW, respectively, in 2018 [5]. China’s total installed capacity reached 175.4 GW, retaining the country’s market leadership position [5]. Additionally, in the USA, solar energy holds the most significant percentage of RESs [7]. 1.1. Motivation The enormous integration of PV plants into the prevailing power grid introduces issues concerning the entire power system’s stability and reliability [8–11]; therefore, transmission Electronics 2021, 10, 2437. https://doi.org/10.3390/electronics10192437 https://www.mdpi.com/journal/electronics