Article A Review on Optimal Control for the Smart Grid Electrical Substation Enhancing Transition Stability Wilson Pavon 1, * , Esteban Inga 1 , Silvio Simani 2 and Maddalena Nonato 2   Citation: Pavon, W.; Inga, E.; Simani, S.; Nonato, M. A Review on Optimal Control for the Smart Grid Electrical Substation enhancing Transition Stability. Energies 2021, 14, 8451. https://doi.org/10.3390/en14248451 Academic Editor: Dimitrios Katsaprakakis Received: 22 September 2021 Accepted: 20 November 2021 Published: 14 December 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 Engineering, Universidad Politécnica Salesiana, Quito EC170146, Ecuador; einga@ups.edu.ec 2 Engineering Department, Università degli Studi di Ferrara, 050031 Ferrara, Italy; smnslv@unife.it (S.S.); maddalena.nonato@unife.it (M.N.) * Correspondence: wpavon@ups.edu.ec Abstract: This paper is a research article for finding the optimal control of smart power substations for improving the network parameters and reliability. The included papers are the most essential and main studies in the field, which propose a different approach to reach the best performance in electrical power systems. The parameters for improvement are the ability for tracking of the reference signal, stabilizing the system, reducing the error in steady state and controlling the behavior in transient state. The research focuses with the reaching a better transient stability considering voltage and frequency dynamic parameters. The optimal model for the control is focused on minimizing energy consumption but maintaining the controllable parameters, exploring some optimization techniques to find the optimal control, with of aim of minimizing the response time, the energy consumption, and maximizing the reliability by means of improving the controller to be more robust. Keywords: smart grid; control; substation; electrical; optimization; hierarchical; distributed generation; microgrid 1. Introduction The present paper aims to give an overview of different existing methodologies for optimal control in a smart power substation (SPSS). The main objective is to show several approaches for optimal control of a SPSS for improving the network transient stability, considering electrical variables as the frequency and voltage. The review explores the general models for integrating all the elements in a SPSS, taking into account that the control must be optimal, enhancing transition stability of the tackled variables. The research has a worldwide impact because smart grid (SG) is one of the most promising technologies to fight against climate change; additionally, there are projects in the region, which aim to unify the generation, transmission, and distribution of energy to improve the stability of the entire system in the region. Finally, there is a massive gap in the regional energy network development, and the researchers’ achievements to boost the technological advances in this field. The document is organized as follows, Section 2 shows the applied methodology to understand a substation, Section 3 shows the State of the Art, Section 4 shows the definitions for SPSS and presents the control level in SPSS, and the strategies for optimal operation. Finally, the conclusions and future work are presented in Section 5. 2. Methodology The methodology is based on the scientific information extracted from the state of the art (SoTA), where the most cited and relevant research were selected considering the documents which tackled the problem with a mathematical modeling and engineering simulation approach. Energies 2021, 14, 8451. https://doi.org/10.3390/en14248451 https://www.mdpi.com/journal/energies