Abstract

Modern distribution networks face dual challenges: extremely asymmetric spatial power flows caused by the high-penetration integration of distributed renewables under normal operating conditions and asymmetric system faults triggered by extreme weather such as blizzards under extreme conditions. To address these imbalances, this paper integrates distributed energy storage (DES) and soft open points (SOPs) as flexible resources to propose a two-stage joint optimal planning method that balances operational economy and resilience enhancement. First, by incorporating the spatiotemporal evolution trajectory and distance attenuation effects of blizzards, a multi-dimensional scenario sets characterizing asymmetric faults and normal source-load fluctuations are constructed. Second, a joint optimal planning model minimizing the total lifecycle cost is established. The progressive hedging algorithm is then adopted to decouple cross-scenario variables for efficient parallel solving. Verified on both the IEEE 33-node and large-scale 123-node systems, the coordinated planning strategy effectively avoids redundant investment in a single type of device. By establishing a symmetrical balance of flexible resources, the proposed method significantly reduces network losses and renewable curtailment during normal operation, while minimizing the amount of system load shedding under extreme asymmetric faults.

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