Surrogate Affine Approximation Based Co-Optimization of Transactive Flexibility, Uncertainty, and Energy

This study presents an approach to co-optimization of transactive flexibility, energy, and optimal injection-range of Variable Energy Resource (VER). Flexibility receives immense attention, as it is the essential resource to accommodate VERs in modern power systems. With a novel concept of transactive flexibility, the proposed approach proactively positions the flexible resources and optimizes the demand of flexibility. A surrogate affine approximation (SAA) method is proposed to solve the problem with variable infinite-constraint range in polynomial time. It is shown that SAA is more optimistic than the traditional affine policy in the power literature. The SAA method is also applicable to the search for secure injection-range of VER, which is often heuristically determined in industry given the latest system information. In practice, VER generation beyond the secure injection-range has to be curtailed, even if its cost is lower than the marginal price. The proposed technique helps accommodate more VERs securely and economically by increasing secure injection-range. The model and the solution approach are illustrated in the 6-bus system and IEEE 118-bus system.