  This letter presents a corrective frequency-constrained UC (C-FCUC) for
island power systems implementing analytical constraints on underfrequency load
shedding (UFLS). Since UFLS is inevitable for sufficiently large disturbances,
one can argue that less spinning reserve could be held back since UFLS takes
place anyway. Congruently, the reserve criterion should consider UFLS likely to
occur under disturbances. The C-FCUC can be converted into a preventive
frequency-constrained UC (P-FCUC) or the standard unit commitment (UC) and the
C-FCUC is thus a generalization. The proposed formulation is successfully
applied to a Spanish island power system.
