Enhancing Fault Ride-Through Capability of a High-Voltage Power Grid Using Solar PV–Battery Assisted Auxiliary Support

High penetration of inverter-based renewable energy sources introduces dynamic stability challenges in high-voltage power systems, particularly under severe fault conditions. This study proposes a renewable-integrated resilience enhancement framework for the Bibiyana 400/230 kV power hub in Bangladesh to ensure uninterrupted supply to critical 1.2 MW auxiliary loads during grid disturbances and blackouts. A 3 MW solar photovoltaic (PV) system integrated with battery energy storage system (BESS) support, interfaced through a grid-forming inverter (GFM) at the 0.4 kV bus, is optimally designed using Hybrid Optimization of Multiple Energy Resources (HOMER) Pro and evaluated in DIgSILENT PowerFactory under load variation, solar curtailment, normal operation, and severe fault scenarios. Techno-economic analysis shows a cost of energy (COE) of 0.0423 USD/kWh, net present cost (NPC) of 3.10 M USD, a renewable fraction (RF) of 88.6%, and CO₂ reduction of 86.9%, with a payback period of 7.07 years. Dynamic results indicate that, under a three-phase fault (5–6 s), the conventional system collapses, whereas the proposed system maintains ~0.98 pu voltage and delivers 1.2 MW supply to the auxiliary loads. Rapid postfault recovery confirms enhanced fault ride-through capability, supply continuity, and overall grid resilience.