Strategic deployment of FACTS devices for enhanced security in multi-area power systems

• A comprehensive analysis of optimal FACTS device placement in multi-area power transmission systems is presented to improve power flow management and strengthen overall system security. • Results show that the optimal locations for FACTS deployment could effectively reduce transmission congestion and enhance reliability. • The proposed method leads to more efficient utilization of the network, increased power flow in underused lines, and a significant improvement in system performance and stability across multi-area transmission systems. The increasing demand for reliable and efficient power transfer in connected systems drives the use of Flexible AC Transmission System (FACTS) controllers. This paper provides a detailed comparison of three key FACTS devices: Phase Shifting Transformer (PST), Unified Power Flow Controller (UPFC), and Optimized Unified Power Flow Controller (OUPFC). It evaluates their performance under normal and outage conditions. The analysis involves IEEE-14 and IEEE-30 multi-area test systems using Newton-Raphson load flow, integrating device models into the power flow equations. Four scenarios are examined: base system, PST, UPFC, and OUPFC. Two performance measures are defined: maximum branch gain and sum-branches gain. Population statistics, including mean, standard deviation, and coefficient of variation, are calculated to assess effectiveness across corridors and devices. The results indicate that OUPFC consistently offers the highest improvements in transfer capacity, achieving gains over 600 % in weak corridors and recovery ratios above 120 % under N-1 outage conditions. UPFC serves as a strong middle-ground device, restoring 70–90 % of lost transfer during outages, while PST provides targeted but cost-effective improvements. The statistical data reveal that performance variability increases with network size, highlighting the necessity for optimization in placement. The study’s innovation lies in combining deterministic, statistical, and contingency viewpoints, backed by visual results and planning recommendations. The findings offer practical guidelines for FACTS deployment, balancing technical effectiveness with cost considerations.