  In this paper, an approach to evaluate the benefits of demand flexibility for
Virtual Power Plants (VPPs) is presented. The flexible demands chosen in this
study are part of a renewable energy source-based VPP that participates in
Day-Ahead Market (DAM) and Intra-Day Market (IDM) and has dispatchable and
non-dispatchable assets. A demand model with bi-level flexibility is proposed:
the first level is associated with DAM, whereas the second level is related to
IDM sessions. Simulations are carried out considering a 12-node network to
ascertain the eventual impacts of modeling demand flexibility on VPP operation.
The market structure considered in the case study resembles the different
trading floors in the Spanish electricity market. Results obtained show that
the proposed demand flexibility scheme increases the overall profit of the VPP,
as well as the revenues of the demand owners without disrupting consumers'
comfort.
