The SUG can be virtually represented as an aggregator of
all the functionalities within the EUA that also acts as a mediator
for the participation in the energy market. Any component
of the SUG - being it a MG, a multi-MG, or an individual
energy entity - can be conceived as a sub-SUG. Fig. 1 shows a
possible evolutionary implementation of SUG concepts. A
SUG can coordinate and represent various combinations of
MGs and multi-MGs, including different operators organized
according to similar operation and technological platforms. As
further described, also EV services aggregators can be recognized
as operators, concretizing the possibility to extend the
MAS paradigm for realizing modes of distributed or mobile
operation for the V2G. Note from this figure that also the EV
aggregators can be seen from the SG interface as individual
agents (sub-SUGs) representing the first level in the hierarchy
of the two-way communication with the SG.