For a MO, this is basically to minimize energy production costs while satisfying the demand; reliability and emissions are usually treated as constraints.
However, a somewhat counter-intuitive consequence of Kirchhoff laws is that interrupting a line (maybe even a congested one) causes a global re-routing of electrical energy and may therefore improve grid performances.
This has led to defining the Optimal Transmission Switching problem,[11] whereby some of the lines of the grid can be dynamically opened and closed across the time horizon.
[23] A troubling consequence of the fact that UC needs be solved well in advance to the actual operations is that the future state of the system is not known exactly, and therefore needs be estimated.
This used to be a relatively minor problem when the uncertainty in the system was only due to variation of users' demand, which on aggregate can be forecasted quite effectively,[24][25] and occurrence of lines or generators faults, which can be dealt with by well established rules (spinning reserve).
[22] This had made it necessary to resort to appropriate mathematical modeling techniques to properly take uncertainty into account, such as: The combination of the (already, many) traditional forms of UC problems with the several (old and) new forms of uncertainty gives rise to the even larger family of Uncertain Unit Commitment[4] (UUC) problems, which are currently at the frontier of applied and methodological research.
One of the major issues with the real-time unit commitment problem is the fact that the electricity demand of the transmission network is usually treated as a "load point" at each distribution system.