  To manage huge amount of flexible distributed energy resources (DERs) in the
distribution networks, the virtual power plant (VPP) is introduced in industry.
The VPP can optimally dispatch these resources in a cluster way and provide
flexibility for the power system operation as a whole. Most existing works
formulate the equivalent power flexibility of the aggregating DERs as
deterministic optimization models without considering their uncertainties. In
this paper, we introduce the stochastic power flexibility range (PFR) to
describe the power flexibility of VPP, which is formulated as a chance
constrained optimization model. In this model, both operational constraints and
the randomness of DERs' output are incorporated, and a combined model and
data-driven solution is proposed to obtain the stochastic PFR and cost function
of VPP. Finally, numerical tests are conducted to verify the correctness and
efficiency of the proposed method.
