Voltage Optimization of Distribution Networks Considering the Grid-Support Capability of Flexible DC Communities

Sustainable operation of photovoltaic-rich distribution networks requires effective use of distributed flexibility to manage voltage variations and regulation costs. However, the support available from flexible DC communities depends on heterogeneous resources and time-coupled constraints, which converter ratings alone cannot capture. This paper proposes a capability-based voltage optimization framework for active distribution networks with flexible DC communities. Photovoltaic generation, storage, electric vehicles, thermal flexibility, and flexible loads are aggregated into feasible active–reactive power capability regions and admissible voltage–active power droop ranges at the point of common coupling. These capabilities are coordinated with network-side resources through a multi-period optimization model balancing network losses and voltage deviation. A Benders–ADMM distributed solution retains detailed community operating information locally. Simulations on a modified IEEE 33-bus system show that converter-based representations overestimate available support. Under heavy-load/low-photovoltaic conditions, coordinated community support reduces mean voltage deviation and the assessed voltage regulation cost by approximately 50% and 45%, respectively, relative to conventional regulation without community support. Voltages remain within prescribed limits across the tested operating conditions, including light-load/high-photovoltaic operation. These findings support sustainable distribution network operation through more effective use of existing flexibility and lower voltage regulation costs.