The easiest way in OpenStudio ([1]) is probably to model 3 PlantLoops with one chiller on the supply side. Put an AvailabilityManager:Scheduled on each plant loop to turn it off when you don't want the chiller operating.

Place an ideal HeatExchanger:FluidToFluid (HX) on the demand side, set the Control Type to CoolingSetpointModulated

Each of the three primary loops would look like this:

Make a secondary PlantLoop, with the three HX on the supply side, and the AHU coils on the demand side.

[1] Note: In EnergyPlus, I would probably make it one loop and tweak the PlantEquipmentOperationSchemes with 3 PlantEquipmentOperationCoolingLoad each with one chiller, that I would schedule On/Off, but in OpenStudio that is not possible