Using Openstudio (2.1.0) how can I change 'Always On Discrete' to a schedule of my choice?

I am confused because
$model.getPlantEquipmentOperationSchemes() returns OS:PlantEquipmentOperation:CoolingLoad objects.

I am expecting that call to return the object like this from the idf PlantEquipmentOperationSchemes, North Chilled Water Loop Operation Schemes, !- Name PlantEquipmentOperation:CoolingLoad, !- Control Scheme Object Type 1 Plant Equipment Operation Cooling Load 7, !- Control Scheme Name 1 Always On Discrete; !- Control Scheme Schedule Name 1

I'd like to set the control scheme schedule to control the chillers and pumps on the chilled water loop.