Citation: Loji, K.; Sharma, S.; Loji, N.; Sharma, G.; Bokoro, P.N. Operational Issues of Contemporary Distribution Systems: A Review on Recent and Emerging Concerns. Energies 2023, 16, 1732. https://doi.org/10.3390/ en16041732 Academic Editors: Tek Tjing Lie and Yogendra Arya Received: 22 October 2022 Revised: 28 January 2023 Accepted: 6 February 2023 Published: 9 February 2023 Copyright: © 2023 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/). energies Review Operational Issues of Contemporary Distribution Systems: A Review on Recent and Emerging Concerns Kabulo Loji 1,2 , Sachin Sharma 3 , Nomhle Loji 1 , Gulshan Sharma 2, * and Pitshou N. Bokoro 2 1 Department of Electrical Power Engineering, Durban University of Technology, Durban 4001, South Africa 2 Department of Electrical Engineering Technology, University of Johannesburg, Johannesburg 2006, South Africa 3 Department of Electrical Engineering, Graphic Era Deemed to be University, Dehradun 248002, India * Correspondence: gulshans@uj.ac.za Abstract: Distribution systems in traditional power systems (PS) constituted of passive elements and the distribution issues were then limited to voltage and thermal constraints, harmonics, overloading and unbalanced loading, reactive power compensation issues, faults and transients, loss minimization and frequency stability problems, to name a few. Contemporary distribution systems are becoming active distributed networks (ADNs) that integrate a substantially increasing amount of distributed energy resources (DERs). DERS include distributed generation (DG) sources, energy storage resources and demand side management (DSM) options. Despite their evidenced great benefits, the large- scale deployment and integration of DERs remain a challenge as they subsequently lead to the network operational and efficiency issues, hampering PS network reliability and stability. This paper carries out a comprehensive literature survey based on the last decade’s research on operational challenges reported and focusing on dispatchable and non-dispatchable DGs grid integration, on various demand response (DR) mechanisms and, on battery energy storage system (BESS) charging and discharging challenges, with the aim to pave the way to developing suitable optimization techniques that will solve the coordination of multiple renewable sources, storage systems and DRs to minimize distribution systems’ operational issues and thus improve stability and reliability. This paper’s findings assist the researchers in the field to conduct further research and to help PS planners and operators decide on appropriate relevant technologies that address challenges inherent to DG grid integration. Keywords: demand response strategies; demand side management; distributed energy resources; battery energy storage systems; distribution generation; operational challenges; optimization techniques 1. Introduction 1.1. Traditional vs. Contemporary PS Networks From the first built PS network, more than 100 years have seen a huge development of the electricity generation and supply systems. Points of generation of electric power were indeed situated several kilometres away from points of consumption as shown in Figure 1, since for economic reasons and a secure supply of electrical power, long distance bulk power transfer was essential [1]. Until the 1990s, the electric power industry was inclined to have a vertical integration approach to generation and transmission, justified mostly by economic reasons as mentioned above, rather than the improvement of the overall efficiency/reliability of the system [2]. The quasi-increasing amount of diverse electrical nature’s loads over time resulted in the change of the grid topology, prompting grid complexity growth as illustrated in Figure 2, requiring much more attention on PS operational issues than ever. Current transformations have been driven for the last two decades by the increasing integration of renewable energy sources (RES), particularly solar and wind sources, known for their intermittency and unpredictability, into national grids. Energies 2023, 16, 1732. https://doi.org/10.3390/en16041732 https://www.mdpi.com/journal/energies