A Planning–Operation Bi-Level Optimization Method for Flexible Power Distribution System Scenarios with Voltage Source Converters Under Flexibility Constraints

High-penetration distributed photovoltaic (PV) generation, energy storage, flexible loads, and voltage source converters (VSCs) are transforming distribution-system operation, making operational flexibility essential in planning. This paper proposes a planning–operation bi-level optimization method for flexible distribution systems with bidirectional flexibility constraints. A multi-resource model is developed for PV, energy storage, interruptible loads, and VSCs. Upward and downward flexibility requirements are quantified from net-load ramping, and the available flexibility of each resource is represented explicitly. The upper level determines PV and energy-storage siting and sizing to minimize annual total cost; the lower level optimizes chronological operation and feeds operating cost, PV curtailment, network losses, voltage deviation, and flexibility shortages back to the planning level. A nested solution strategy combining an improved dung beetle optimization algorithm with operational evaluation was tested on a 58-bus AC/DC hybrid distribution system. Compared with coordinated source-storage planning without flexibility constraints, the proposed scheme reduced annual total cost by CNY 14.8998 million and increased average daily upward and downward flexibility margins to approximately 1.30 MW and 0.38 MW, respectively. The results also show improved PV accommodation and voltage quality, confirming the method’s economic and operational effectiveness under high renewable-energy penetration.