From @crphilbrick:
PROBLEM: Steam units have commitment constraints and costs that make it impossible to commit the generator in day ahead (DA) or that cannot be accurately managed in DA.
RESOLUTION: "Week Ahead" cycle added to model. Inflexible generators identified as "Stage1" commitment in this cycle.
JUSTIFICATION: In real world, inflexible generators would be self-scheduled or committed by a process before DA.
From @crphilbrick: