Normalized Source-Storage-Load Flexibility-Loss Indicators for Day-Ahead Scheduling of Renewable Virtual Power Plants

ABSTRACT: Renewable virtual power plants (VPPs) require day-ahead schedules that coordinate renewable generation, storage, gas turbines, and demand-side flexibility while retaining interpretable operating signals. This paper develops a normalized source-storage-load flexibility-loss-indicator (FLI) framework for renewable VPP scheduling. The indicators are engineering proxies for renewable-curtailment value loss, storage availability loss, and interruptible-load activation burden, rather than market-settled opportunity costs or a complete uncertainty-risk measure. The scalar objective combines net operating cost, operating coordination cost, and normalized FLI terms with reference scales fixed within each comparative setting. In a PJM-scaled day-ahead scheduling case, the baseline, scalarized multi-term reference, and proposed FLI schedules achieved net operating profits of 69,590.98 USD, 60,377.26 USD, and 66,856.81 USD. The proposed schedule reduced SOC boundary contacts from 9 to 3 and equivalent full cycles from 1.7253 to 1.6647, with a 3.93% profit concession relative to the baseline. Weight sensitivity, channel ablation, and eight representative operating and stress-test scenarios show state-dependent effects: the storage channel was active in seven scenarios, the interruptible-load channel under peak and flexibility-stressed conditions, and the renewable channel remained weak because curtailment was nearly zero. The framework provides a diagnostic coordination signal for renewable VPP operation.