Absolute or proportional minimum? For charge or discharge? If proportional, proportional to what?
Absolute bounds for storage discharge can be defined by STGOUT_BND. A minimum discharge flow proportional to the storage level can be easily defined by FLO_SHAR (if it is a timeslice storage). Minimum discharge flow proportional to capacity would be also possible, but would require defining an auxiliary storage flow, and then a UC constraint referring to the aux flow and the capacity.
Absolute bounds for storage charge can be defined by STGIN_BND. A minimum charge flow proportional to the storage level or capacity would be possible by defining an auxiliary storage flow, and then a UC.
EDIT: Or do you mean minimum level for the state of charge?
Absolute bounds for storage discharge can be defined by STGOUT_BND. A minimum discharge flow proportional to the storage level can be easily defined by FLO_SHAR (if it is a timeslice storage). Minimum discharge flow proportional to capacity would be also possible, but would require defining an auxiliary storage flow, and then a UC constraint referring to the aux flow and the capacity.
Absolute bounds for storage charge can be defined by STGIN_BND. A minimum charge flow proportional to the storage level or capacity would be possible by defining an auxiliary storage flow, and then a UC.
EDIT: Or do you mean minimum level for the state of charge?