  Flexibility in power demand, diverse usage patterns and storage capability of
plug-in electric vehicles (PEVs) grow the elasticity of residential electricity
demand remarkably. This elasticity can be utilized to form the daily aggregated
demand profile and/or alter instantaneous demand of a system wherein a large
number of residential PEVs share one electricity retailer or an aggregator. In
this paper, we propose a demand response (DR) technique to manage
vehicle-to-grid (V2G) enabled PEVs' electricity assignments (charging and
discharging) in order to reduce the overall electricity procurement costs for a
retailer bidding to a two-settlement electricity market, i.e., a day-ahead (DA)
and a spot or real-time (RT) market. We show that our approach is
decentralized, scalable, fast converging and does not violate users' privacy.
Extensive simulations show significant overall cost savings can be achieved for
a retailer bidding to an operational electricity market by using the proposed
algorithm. This technique becomes more needful when the power grid accommodates
a large number of intermittent energy resources wherein RT demand altering is
crucial due to more likely contingencies and hence more RT price fluctuations
and even occurring the so-called \textit{black swan events}. Finally, such
retailer could offer better deals to customers as well.
