频率安全问题往往发生在少量的、离群的极端场景下，如风光出力高导致常规同步机组开机少的场景，而现有规划偏重典型场景遗漏极端场景。文中采用基于剪枝精确线性时间（Pruned Exact Linear Time, PELT）的变点搜索算法辨识自适应时间段极端场景，构建涵盖风、光、火、储、特高压直流、需求侧响应的多机系统频率响应模型推导频率安全约束。在此基础上提出三层迭代源网储协同规划方法，建立优化配置主问题模型、典型场景运行子问题模型、极端场景运行子问题模型，采用MATLAB Simulink仿真、割函数反馈、L型分解协调等方法，实现电源、输电线路和储能建设的同步优化。最后通过某实际区域电网算例验证方法的有效性，探讨极端场景、负荷、新能源不确定性对规划结果的影响。该方法通过增加少量投资和优化机组运行，保障极端场景下的电力系统频率安全，并可以为新能源发展边界提供建议。

Frequency security issues often occur in a small number of outlier extreme scenarios, such as when large-scale wind and solar power generation leads to fewer conventional synchronous units being online, while existing planning method focuses on typical scenarios and overlooks extreme ones. This paper realizes the identification of adaptive time-interval extreme scenarios based on the PELT algorithm, constructs frequency security constraints using a multi-machine system frequency response model that incorporates wind, solar, thermal, energy storage, UHVDC, and demand-side response. On this basis, a three-layer iterative source-grid-storage collaborative planning model is established, including an optimal configuration master problem model, a typical scenario operation sub-problem model, and an extreme scenario operation sub-problem model. Model solving is achieved through methods such as MATLAB Simulink simulation, cut function feedback, and L-shape decomposition coordination. The method optimizes the construction plans for generators, transmission lines, and energy storages at the same time. Finally, the effectiveness of the proposed method is verified through a case study of an actual regional power grid, and the impacts of extreme scenarios, load, and new energy factors on the planning results are analyzed. This method ensures the frequency security of power systems in extreme scenarios by increasing a small amount of investment and optimizing unit operation, and can provide suggestions for the development boundaries of new energy.