Weak distribution grids with low short-circuit ratios are increasingly challenged by large voltage sags during inductive load switching. Grid-following inverters (GFLI) can provide fast local Volt-VAR support, but their voltage recovery capability is constrained by apparent power limits, DC-link dynamics, and phase-locked loop (PLL) stability. Grid-forming inverters (GFMI), in contrast, can establish voltage and frequency references to stabilize the grid; however, they are complex and expensive. This paper presents a coordinated control strategy to enhance voltage sag recovery and stability in weak distribution networks. Using a test system with S C R=4, the proposed approach demonstrates that GFLI can rapidly inject reactive power by curtailing real power while preserving DC bus voltage as a priority, surpassing its conventional maximum power delivery role. Simulation results show that point of common coupling (PCC) voltage sag depth is reduced by 3 0 - 3 5 % after VAR activation (from approximately 0.82 pu to 0.93 pu), with voltage recovery occurring within 200-250 ms. The DC-link voltage remains within pm 3 % of nominal during VAR support, and PLL synchronization is maintained without loss of synchronism, making it a perfect contender for GFMI, because GFMI has current limitation drawback. The system effectively mitigates harmonic distortion also caused by DC-bus oscillations during sustained VAR injection and environmental shift. These results confirm that coordinated GFLI-GFMI control could significantly enhance voltage recovery capability and dynamic stability under weak-grid conditions compared to standalone GFMI operation.
