def min_power_rule(mod, g, tmp):
    """
    **Constraint Name**: GenSimple_Min_Power_Constraint
    **Enforced Over**: GEN_SIMPLE_OPR_TMPS

    Power minus downward services cannot be below zero.
    """
    return mod.GenSimple_Provide_Power_MW[g, tmp] \
        - mod.GenSimple_Downwards_Reserves_MW[g, tmp] \
        >= 0