This paper focuses on implementing the unified power flow controller (UPFC) in the optimal power flow approach, a critical aspect of power and control system operations. Optimal power flow minimizes operating costs and maintains safety margins for control variables, making it an indispensable tool for energy management. The flexible AC transmission system (FACTS) is a fundamental component of this approach, with the UPFC playing a crucial role. This versatile device provides various types of energy system compensation, enabling the independent control of reactive and active electrical power in transmission lines and bus voltages simultaneously. Previous studies have explored a wide range of engineering applications for UPFC using diverse techniques. This paper reviews these applications, specifically examining how UPFC can increase power system flexibility and controllability. Additionally, this paper explores utilizing artificial intelligence (AI) in the placement of UPFC in power systems. By incorporating AI techniques such as machine learning and optimization algorithms, power system operators can optimize the placement of UPFC to achieve optimal energy management. This approach enhances the efficiency and reliability of energy systems, resulting in significant cost savings and improved power system performance.