Optimization-based dynamic voltage support strategy for inverter-based resources in weak grid conditions: Design, analysis and validation

The growing penetration of inverter-based resources (IBRs) in modern power systems demands effective dynamic voltage support (DVS) strategies, especially during low-voltage ride-through (LVRT) events. This paper proposes an optimization-based DVS method that coordinates active and reactive power while ensuring synchronization stability and robustness against grid impedance uncertainty. The voltage support problem is formulated as a constrained optimization considering current limits and dc-side power availability. An analytical, real-time solution is derived through Karush-Kuhn-Tucker (KKT) conditions applied to the nonconvex voltage maximization problem, yielding closed-form expressions for optimal active and reactive current references across three distinct operating regions determined by active constraint combinations. Simulation results under various balanced and unbalanced fault conditions show up to 95% improvement in voltage recovery and enhanced power delivery compared to droop, PI, MPC, and RL-based methods. The inverter dynamic model incorporates dual-sequence current control in the synchronous dq-reference frame with explicit dc-link voltage regulation, enabling coordinated LVRT response under both symmetrical and asymmetrical grid faults. The proposed strategy achieves near-optimal voltage support with low computational cost, making it suitable for real-time deployment in weak and renewable-rich grids.