Variable CHW Flow Chillers Operate unexpectedly

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In fact, there is a way around this bug to some extent, but not completely.

Multiple PlantEquipmentList objects can be modelled as follows to allow operation of only one chiller, two chillers, three chillers , and all chillers. The load upper limit for each PlantEquipmentList object is specified in PlantEquipmentOperation:CoolingLoad.

PlantEquipmentList,
    Chilled Water Loop 1 Chiller,  !- Name
    Chiller:Electric:EIR,    !- Equipment 1 Object Type
    Chiller1;           !- Equipment 1 Name

PlantEquipmentList,
    Chilled Water Loop 2 Chillers,  !- Name
    Chiller:Electric:EIR,    !- Equipment 1 Object Type
    Chiller1,           !- Equipment 1 Name
    Chiller:Electric:EIR,    !- Equipment 2 Object Type
    Chiller2;           !- Equipment 2 Name

PlantEquipmentList,
    Chilled Water Loop 3 Chillers,  !- Name
    Chiller:Electric:EIR,    !- Equipment 1 Object Type
    Chiller1,           !- Equipment 1 Name
    Chiller:Electric:EIR,    !- Equipment 2 Object Type
    Chiller2,           !- Equipment 2 Name
    Chiller:Electric:EIR,    !- Equipment 3 Object Type
    Chiller3;           !- Equipment 3 Name

PlantEquipmentList,
    Chilled Water Loop All Chillers,  !- Name
    Chiller:Electric:EIR,    !- Equipment 1 Object Type
    Chiller1,           !- Equipment 1 Name
    Chiller:Electric:EIR,    !- Equipment 2 Object Type
    Chiller2,           !- Equipment 2 Name
    Chiller:Electric:EIR,    !- Equipment 3 Object Type
    Chiller3,           !- Equipment 3 Name
    Chiller:Electric:EIR,    !- Equipment 4 Object Type
    Chiller4;           !- Equipment 4 Name

PlantEquipmentOperation:CoolingLoad,
    Chilled Water Loop Chiller Operation All Hours,  !- Name
    0,                       !- Load Range 1 Lower Limit {W}
    8866.94,                 !- Load Range 1 Upper Limit {W}
    Chilled Water Loop 1 Chiller,  !- Range 1 Equipment List Name
    8866.94,                 !- Load Range 2 Lower Limit {W}
    17733.88,                !- Load Range 2 Upper Limit {W}
    Chilled Water Loop 2 Chillers,  !- Range 2 Equipment List Name
    17733.88,                !- Load Range 3 Lower Limit {W}
    26600.82,                !- Load Range 3 Upper Limit {W}
    Chilled Water Loop 3 Chillers,  !- Range 3 Equipment List Name
    26600.82,                !- Load Range 4 Lower Limit {W}
    1E+15,                   !- Load Range 4 Upper Limit {W}
    Chilled Water Loop All Chillers;  !- Range 4 Equipment List Name

However, when a large negative value is detected in the output variable Plant Supply Side Unmet Demand Rate, Plant Supply Side Cooling Demand Rate gets bigger than it needs to be, and this workaround does not work well.