Enhancing Optimal Reactive Power Dispatch under Critical Contingencies Using MPC-GUPFC with FRT Capability and HPSOBAT Optimization

This paper presents a unified and intelligent scheme for enhancing Optimal Reactive Power Dispatch (ORPD) under severe grid disturbances in the IEEE 30-bus system. A critical branch outage is first identified using a composite performance index (PI) based on total power loss and total voltage variation. The most severe line removal introduces up to 10.0 MW of additional losses and a voltage deviation of 0.021 pu, significantly degrading system performance. To effectively counter this, a combined mitigation strategy is proposed, simultaneously applying a Fault Ride-Through (FRT) mechanism and a Model Predictive Control based Generalized Unified Power Flow Controller (MPC-GUPFC). The MPC-GUPFC is dynamically controlled over a 5-step prediction horizon and optimally placed at sensitive bus triplets using a sensitivity-driven placement framework. The FRT capability ensures system stability during the disturbance, while the MPC-GUPFC adaptively controls power flow and supports voltage during and after the faulty event. Quantitative results show that this coordinated FRT with MPC-GUPFC strategy reduces total power losses from 21.8 MW (post-outage without mitigation) to 12.2 MW, and worse-case voltage deviation from 0.136 pu to 0.060 pu, at a quantified MPC-GUPFC cost of $55,226.15. Moreover, reactive power losses are minimized from 16.9 MVAr to 9.5 MVAr, and the system converges in fewer than 10 iterations, compared to over 20 iterations in the unmitigated case. The overall PI value is improved by over 43.79 %, demonstrating the superiority of the proposed approach in improving voltage stability, loss minimization, and post-contingency recovery.