Optimal Planning for Offshore Wind Farm Electrical Collector System Considering $N-1$ Criterion

With the rise of renewable energy-centered power systems, offshore wind has emerged as a cornerstone of the clean energy transition. Despite the growing demand for highly reliable and cost-effective electrical collector system (ECS) planning, existing research based on the $N-1$ security criterion remains largely confined to conventional single-/double-sided ring topologies and heuristic algorithms, thus falling short in balancing the tradeoff between economic performance and stringent reliability requirements. In this paper, we propose a novel ECS planning framework for offshore wind farms (OWFs) by developing a scenario-based $N-1$ composite ring planning model. Furthermore, the proposed framework is extended to support cable size selection through mathematical optimization models for both double-sided ring topology and $N-1$ composite ring topology. To reduce computational complexity, model simplification and acceleration strategies are adopted. Case studies demonstrate that the proposed approach achieves superior optimization outcomes under the $N-1$ framework compared with conventional methods.