Abstract
The rapid integration of remote renewable energy sources has strained existing AC transmission corridors, pushing them to post-transient stability limits before reaching thermal capacity. This congestion compromises grid reliability and restricts power transfer potential. While HVDC systems like the Pacific DC Intertie (PDCI) offer solutions through superior controllability and long-distance efficiency, their dynamic interactions with parallel AC networks during contingencies remain underexplored. Specifically, the asymmetric stability response of HVDC systems during major AC faults requires deeper analysis to optimize grid resilience. This study investigates how HVDC emergency controls can mitigate these instability risks in renewable-rich power systems and how integration of HVDC systems into the existing grid can solve many problems faced by the grid today.