Analysis of Reaching Law Effectiveness in Sliding Mode Control of the UPFC

The Unified Power Flow Controller (UPFC) represents a critical component within the Family of FACTS devices, employed to improve the stability, reliability, and controllability of electrical power systems under fluctuating load conditions. This research endeavors to assess various reaching laws within the paradigm of Sliding Mode Control (SMC) with the aim of enhancing the dynamic performance of a UPFC. Specifically, an examination and comparison of three distinct types of reaching laws—constant rate, exponential rate, and power rate—are conducted. The principal aim is to devise and implement robust control methodologies that guarantee precise tracking of reference power commands, as well as improved regulation of both active and reactive power flows within transmission lines. The proposed SMC-based controllers are incorporated into a simulated UPFC framework, with their performance being compared against that of a conventional PID controller. Simulation models have been constructed using MATLAB/Simulink, and performance metrics including overshoot, settling time, and rise time are utilized for quantitative analysis. The results demonstrate that the SMC utilizing the power rate reaching law significantly surpasses the conventional PID controller, achieving a minimal overshoot of approximately 0.5411%, a settling time of 0.1009 seconds, and a rapid rise time of 4.0720 × 10⁻⁴ seconds. These findings substantiate the efficacy of advanced reaching laws in augmenting UPFC control, thereby contributing to enhanced stability and operational efficiency within power systems.