Unified Power Flow Controller (UPFC) Used to Relieve Power Congestion on a 500/230 kV Grid Hayder Khaleel AL-Qaysi Department of Electronic Engineering, College of Engineering, University of Diyala, Baqubah 32001, Iraq Corresponding Author Email: hay.kha.82@uodiyala.edu.iq Copyright: ©2024 The author. This article is published by IIETA and is licensed under the CC BY 4.0 license (http://creativecommons.org/licenses/by/4.0/). https://doi.org/10.18280/jesa.570307 ABSTRACT Received: 8 February 2024 Revised: 15 April 2024 Accepted: 8 May 2024 Available online: 25 June 2024 This research paper aims to investigate the application of a unified power flow controller (UPFC) for relieving power congestion on a 500/230 kV grid, Power congestion occurs when the demand for electrical power exceeds the transmission capacity of the grid resulting in potential stability issues and voltage fluctuations. The UPFC is a flexible and advanced power electronic device that can regulate power flow and voltage levels in real- time hence offering a potential solution to alleviate congestion. This study explores the principles of UPFC operation its control strategies and the impact of its installation on power system stability and reliability. The research methodology involves computer simulations and analysis of the results obtained. Keywords: unified power flow controller (UPFC), power congestion, grid stability, voltage regulation, power system reliability 1. INTRODUCTION The increased desire for electric power in recent times has created tension in the power transmission sector. This has raised concerns about power blockages that do not only affect the reliability of the network but also bar effective delivery of electricity. Advanced methodologies e.g. unified power flow controller (UPFC) are being used to solve this problem. The UPFC is a flexible AC transmission system (FACTS) device, which is used for modulating power flow as well as voltage at any instant (in real-time) and can potentially solve power congestion problems on transmission grids. UPFC is able to control transmission lines power flow. This is achieved by injecting series voltage (Vs) and switching current (Ish) into the system. The desired power flow regulation basis on which voltages and currents are injected can be varied. Through this, the UPFC can be able to effectively manage both active as well as reactive power transmitted via the line. It is essential to note that UPFC helps a lot in maintaining proper voltage levels within the network hence it is through direct injection of voltage Vs into the system that it achieves this [1]. One can change the amplitude and phase shift of introjected voltage in order to compensate the losses by voltage or voltage instability and keep steady the voltage. Distinct control strategies are applied in order to control power flow and voltage through unified power flow control (UPFC). Typically, measurements of line current, voltage and phase angle are made under these strategies. According to those measurements, injection parameters must be tuned by the UPFC (Vs and Ish) for achieving desired control objective(s). All in all, significant advantages with respect to alleviating power congestion on transmission networks are brought by UPFC itself. That is, making possible higher efficient power transfer, it also boosts grid stability as well as helps in preservation of the desired voltage fluctuation limits [2]. Objectives of this investigation go beyond simply inspecting practical application of UPFC in reducing electrical grid load problem for 500/230 kV systems; they also include elucidating complexities inherent in its functioning mechanisms [3]. The purpose of this study was to research about the UPFC control strategies and their implications for power systems stability and reliability so as to fill the existing gaps in literature on managing grid congestion. This study uses advanced computer simulations and precise analytical methods to explore profound insights into the optimal implementation of UPFC that can deal effectively with power congestion issues. In a bid to offer tangible proof of its ability to increase power system stability increase power flow control related problems reductions among others, the performance of UPFC in real time conditions for different operational scenarios will be investigated. In illuminating the practical consequences of UPFC deployment and its effect on power system operations, this study aims to provide valuable insights in electrical grid management [4]. In conclusion, the aim is to provide practical advice and remedies that allow network operators and policy makers to decide on how best to handle electric grid congestion and guarantee movement systems run smoothly. 2. OVERVIEW OF UPFC The UPFC is composed of several important components such as one series transformer, one shunt inverter, and one DC link. The main function of the series transformer is to control both active and reactive power flows whereas for the shunt Journal Européen des Systèmes Automatisés Vol. 57, No. 3, June, 2024, pp. 699-708 Journal homepage: http://iieta.org/journals/jesa 699