COUPLING_BASE
=============

Per-port no-load base power for a unit-committed coupling group.
Give a positive power magnitude; its direction follows the port's flow direction (the same way ``coupling-coefficient`` does).
When the coupling group is unit-committed, each port's power equals its coupling coefficient times the group's marginal level *plus* this base, all gated by the group's on/off binary: ``P = coefficient * level + base`` when on, and ``0`` when off.
Use it to model a no-load offset, such as a cogeneration unit's no-load fuel consumption that is burned only while the unit runs.
Setting a non-zero base (on any port) makes the coupling group unit-committed.
Defaults to 0.