Addressing the Transmission Constraints of Nigeria National Grid via Optimal Distributed Power Flow Controller Placement

The uncertainties in the Nigerian National Grid have raised serious concerns among researchers and stakeholders in the power sector. Aging equipment, inadequate generation, and diminishing transmission capacity cause the persistent instability of the grid, which includes intermittent system collapses and voltage rises or drops that exceed the safe operating limit. After more than a dozen outages in 2025, several have occurred in 2026. Technical issues with 330kV lines and inadequate reserve power frequently cause severe outages, which almost completely stop generation. This study presents a steady state and post-load flow analysis of a 30-bus transmission network in Nigeria in order to evaluate voltage stability using the Modern Voltage Stability Index (MVSI) in MATLAB environment. Preliminary results indicate that twenty-five buses operate within the permissible stability range (0.95-1.05 p.u.), two heavily loaded buses (1.4-1.6 p.u.) exhibit instability of MVSI > 1.05, and three weak buses (MVSI <0.95 at 0.80, 0.89, 0.94). A linear regression model (MVSI = 0.24P + 0.85, R2 = 0.73) indicates that voltage stability is primarily based on loading conditions, with instability hazards rising above 0.83 p.u. To mitigate these issues, a Distributed Power Flow Controller (DPFC) is deployed with a control gain of 0.45 and a maximum reactive power injection of 0.12 MVar per iteration. The proposed approach achieves full system stabilization within 20 iterations, improving the mean MVSI from 0.80 to 0.992 and reduced from 1.6 to 1.002. Post-compensation results show a marginal adjustment in regression performance (R² = 0.68), indicating enhanced system dynamics without altering the intrinsic load–stability relationship. Additionally, voltage profiles at critical buses improve by 3–5%, while power transfer capability increases by approximately 24%. These results demonstrate the effectiveness of DPFC in enhancing voltage stability and transmission efficiency in developing power systems.