Improved characterization for AC-feasible power transfer regions of virtual power plants

Aggregating distributed energy resources as virtual power plants (VPPs) to participate in transmission-level operations is a promising direction for future grids. However, it is challenging to decide the AC-feasible power transfer region of such a VPP at its point of common coupling with the transmission. This paper proposes an improved method to characterize this region. The proposed method constructs linear constraints to inner-approximate the AC-feasible power transfer regions, by applying Brouwer’s fixed-point theorem to the second-order Taylor expansion of the nonlinear Dist-flow equations. An exploration strategy is proposed to further improve our characterization flexibility. Finally, a transmission-level operation problem with VPP participation is formulated and solved through big-M linearization. The proposed methods are verified by numerical experiments on the IEEE 33-bus and 136-bus test systems.