Central plant control system with setpoints modification based on physical constraints

A method for an energy plant including heating, ventilation, air conditioning (HVAC) devices, the method including:

• determining flow rates of gas or liquid through a plurality of the HVAC devices of the energy plant connected in parallel with each other in a branch such that outputs of the plurality of the HVAC devices combine to form a combined output of the branch;
• using the flow rates and a constraint on the combined output of the branch to generate a candidate set of operating parameters indicating target thermodynamic states other than flow rate of the outputs of the plurality of the HVAC devices, the candidate set of operating parameters predicted to result in the combined output of the branch having a thermodynamic state other than flow rate that satisfies the constraint on the combined output of the branch when the outputs of the plurality of the HVAC devices combine according to the flow rates to form the combined output of the branch;
• and
• operating the energy plant according to the candidate set of operating parameters by controlling the plurality of the HVAC devices to produce the outputs using the target thermodynamic states indicated by the candidate set of operating parameters.

A non-transitory computer readable medium storing instructions when executed by a processor cause the processor to:

• determine, for each of a plurality of heating, ventilation, air conditioning (HVAC) devices of an energy plant, a flow rate ratio based on a hydraulic resistance value for said each of the plurality of HVAC devices and a summation of the hydraulic resistance values for the plurality of the HVAC devices, the plurality of HVAC devices connected in parallel with each other in a branch such that outputs of the plurality of the HVAC devices combine to form a combined output of the branch;
• use the flow rate ratios of the plurality of HVAC devices and a constraint on the combined output of the branch to generate a candidate set of operating parameters indicating target thermodynamic states other than flow rate of the outputs of the plurality of the HVAC devices, the candidate set of operating parameters predicted to result in the combined output of the branch having a thermodynamic state other than flow rate that satisfies the constraint on the combined output of the branch when the outputs of the plurality of the HVAC devices combine according to the flow rates to form the combined output of the branch;
• and
• operate the energy plant according to the candidate set of operating parameters by controlling the plurality of the HVAC devices to produce the outputs using the target thermodynamic states indicated by the candidate set of operating parameters.