Two-stage coordinated robust electricity trading for virtual power plants across the annual-to-spot trading cycle under asynchronous wholesale-retail interaction

Virtual power plants (VPPs) increasingly operate across annual contracting, monthly adjustment, and spot settlement. Annual contracts establish base positions that allow VPPs to pre-position contracted resources and reduce quantity-price exposure before short-horizon operation, yet most existing studies focus on short-horizon dispatch and treat annual contracting outcomes as exogenous inputs. To bridge the gap between endogenous annual position formation and monthly-spot operational rebalancing, this paper proposes a two-stage coordinated robust trading method for VPPs over the annual-to-spot trading cycle under asynchronous wholesale-retail interaction. In Stage I, a rolling forward-contracting model captures the concurrent evolution of progressive retail contracting and batch wholesale position building under multi-round negotiations with irreversible commitments, while a hierarchical curve-based source-load matching method and an asymmetric pricing mechanism guide procurement toward resource-specific benchmark curves. Taking the annual positions formed in Stage I as fixed inputs, Stage II develops a multi-timescale operational rebalancing model that jointly optimizes position adjustment, spot settlement, and internal flexible resource dispatch under a structured finite uncertainty set with explicit cross-channel restrictions. The model is further evaluated against an augmented finite scenario library that includes a portfolio-adaptive candidate adverse scenario constructed through period-wise enumeration. For a representative VPP in the Sichuan provincial electricity market, the proposed method increases Stage-I profit by 20.5% relative to the static single-round benchmark, yields a more balanced procurement structure, and, within the evaluated library, reduces the worst-case rebalancing cost by 7.9% relative to the no-spot-close-out benchmark. Full-cycle wholesale-retail coordination therefore improves both annual position quality and worst-case protection. © 2026 Elsevier Ltd.