  The penetration of variable renewable energy (VRE) in electrical systems has
changed the way the expansion planning is treated. This kind of resource has
great variability in small amounts of time, which makes it important to
represent hourly constraints that require chronology. Besides that, the
generation reserves should also be adjusted in order to capture the
intermittent effect, and since many countries use rapid thermal plants as part
of these reserves, unit commitment and ramp constraint have also become more
significant. In this paper, we propose a MILP expansion planning model that can
represent hourly time steps while maintaining reasonable computational times,
where both investment and operation problems are simultaneously solved. Because
the planning horizons are long (decades), the resolution of the entire horizon
in a single optimization problem would be computationally infeasible for large
real systems, making it necessary, therefore, to apply a horizon decomposition
heuristic in smaller sub-horizons, and use the representation of typical days
and seasons to reduces the size of the problem.
