Research on the adaptability of east China receiving-end grid to new ultra-high voltage DC transmission from external regions based on transient multi-feed-in short-circuit ratio

The establishment of carbon neutrality objectives has catalysed accelerated decarbonization of energy systems, driving transformative grid modernization initiatives. This structural transformation manifests through accelerating cross-regional HVDC deployment, concentrated renewable generation clusters, and geospatial disparity in generation-resource distribution. The transient multi-infeed short-circuit ratio (TMSCR) demonstrates particular quantitative technical advantage in DC interconnection planning through its dynamic system strength characterization. This study synthesizes renewable-hydro hybrid system development trajectories with China's 15th Five-Year Plan energy targets, specifically examining East China's grid modernization challenges. Critical analyses address: 1) Strategic positioning of new ±800kV UHV DC interconnects 2) Receiving-end grid security impacts through composite stability indices 3) Main grid operational interactions during multi-DC contingency events. The research further projects East China's 2035 grid architecture under multiple energy transition scenarios. Technical recommendations advocate deploying modular multilevel converter (MMC) configurations for future DC interconnections, implementing adaptive network reinforcement protocols aligned with provincial load centres. These findings directly inform State Grid Corporation's Five-Year Plan transmission investments while establishing technical baselines for hybrid AC/DC grid resilience assessments under N-1 security criteria.