  The insertion of renewable sources in power systems may cause a decrease in
the system's equivalent inertia, which result in the instability of the power
system. On the other hand, energy storage systems have proven to be an
effective tool to increase the flexibility in the operation of energy systems,
which may favor integrating renewable energy sources. In this way, plug-in
electric vehicle (PEVs) batteries can be used as storages when such vehicles
are parked and connected to the grid. In this work, the contribution of PEVs to
primary frequency response is analyzed in systems dominated by renewable
sources. A day-ahead scheduling model is developed considering PEVs groups can
actively participate in electricity markets, supporting day-ahead reserve
capacity and providing primary frequency response. The proposed model is
implemented in the distribution system of the Federal University of Amap\'a.
