Joint offering strategy for multi-virtual power plants: a stepwise offer curve construction via probability-guided sequential optimization

Virtual Power Plants (VPPs) face significant challenges in wholesale electricity markets, including renewable generation uncertainty and market access barriers. This paper proposes a joint offering strategy for an alliance of VPPs, enabling them to submit a unified, stepwise offer curve. The strategy is built on a probability-guided sequential optimization (PGSO) framework, which first optimizes offers for the most probable price intervals based on forecasts, then sequentially handles the remaining intervals to ensure computational efficiency. To handle uncertainties, the model applies distributionally robust optimization (DRO) for stochastic wind power. Case studies demonstrate that the joint strategy improves profitability compared to independent offering, primarily through internal resource sharing and risk hedging. The analysis validates the advantages of the DRO approach over traditional methods and confirms the effectiveness of the proposed PGSO framework.