Central plant control system with computation reduction based on stranded node analysis

1. A controller for an energy plant, the controller comprising:

a processing circuit comprising a processor and memory storing instructions executed by the processor, the processing circuit configured to:

perform a stranded node analysis on connections of a plurality of heating, ventilation, or air conditioning (HVAC) devices, wherein performing the stranded node analysis comprises using schematic relationships of the plurality of HVAC devices to determine a reduced subset of the plurality of HVAC devices for which a set of operating parameters of the plurality of HVAC devices is determined;

predict thermodynamic states of the reduced subset;

determine the set of operating parameters based on the thermodynamic states; and

operate the plurality of HVAC devices according to the set of operating parameters.

2. The controller of claim 1 , wherein the processing circuit is configured to determine the schematic relationships of the plurality of HVAC devices of the energy plant based on the stranded node analysis by: removing a first HVAC device of the plurality of HVAC devices; detecting a stranded node after removing the first HVAC device; and determining a second HVAC device coupled to the stranded node to be schematically dependent on the first HVAC device.

3. The controller of claim 2 , wherein the stranded node has only one or more of inlets or outlets after removing the first HVAC device.

4. The controller of claim 1 , wherein the processing circuit is further configured to:

generate an incidence matrix indicating the schematic relationships of the plurality of HVAC devices, each set of elements of the incidence matrix in a first direction associated with a corresponding HVAC device, each set of elements of the incidence matrix in a second direction associated with a corresponding node,

wherein the schematic relationships are determined based on the incidence matrix.

5. The controller of claim 4 , wherein the processing circuit is configured to determine the schematic relationships by:

replacing a nonzero value of a first set of elements of the incidence matrix in the first direction with zero, the first set of elements associated with a HVAC device of the plurality of HVAC devices; and

detecting a second set of elements of the incidence matrix in the second direction having one of a first value corresponding to an inlet and a second value corresponding to an outlet but not both the first value and the second value, the detected second set of elements corresponding to a stranded node.

6. The controller of claim 5 , wherein the processing circuit is configured to determine the schematic relationships by:

detecting the second set of elements of the incidence matrix in the first direction having the first value, the second set of elements corresponding to another HVAC device of the plurality of HVAC devices schematically dependent on the HVAC device.

7. The controller of claim 6 , wherein the processing circuit is configured to determine the schematic relationships by:

replacing a nonzero value of the second set of elements of the incidence matrix with zero.

8. A controller for an energy plant, the controller comprising:

a processing circuit comprising a processor and memory storing instructions executed by the processor, the processing circuit configured to:

determine schematic relationships of a plurality of heat, ventilation, and air conditioning (HVAC) devices of the energy plant based on connections of the plurality of HVAC devices, each HVAC device configured to operate according to a corresponding operating parameter;

determine a reduced subset of the plurality of HVAC devices based on the schematic relationships;

identify, from the plurality of HVAC devices, a first HVAC device to be turned off;

determine a second HVAC device schematically dependent on the first HVAC device;

exclude the first HVAC device and the second HVAC device from the reduced subset of the plurality of HVAC devices;

predict thermodynamic states of the reduced subset;

determine a set of operating parameters of the plurality of HVAC devices based on the thermodynamic states; and

operate the plurality of HVAC devices according to the set of operating parameters.

9. A controller for an energy plant, the controller comprising:

a processing circuit comprising a processor and memory storing instructions executed by the processor, the processing circuit configured to:

determine schematic relationships of a plurality of heat, ventilation, and air conditioning (HVAC) devices of the energy plant based on connections of the plurality of HVAC devices, each HVAC device configured to operate according to a corresponding operating parameter;

determine a reduced subset of the plurality of HVAC devices based on the schematic relationships;

identify, from the plurality of HVAC devices, a first HVAC device to be turned on;

determine a second HVAC device schematically dependent on the first HVAC device;

add the first HVAC device and the second HVAC device to the reduced subset of the plurality of HVAC devices in response to determining that the second HVAC device is schematically dependent on the first HVAC device;

predict thermodynamic states of the reduced subset;

determine a set of operating parameters of the plurality of HVAC devices based on the thermodynamic states; and

operate the plurality of HVAC devices according to the set of operating parameters.

10. A method of operating an energy plant, the method comprising:

generating an incidence matrix indicating schematic relationships of a plurality of heat, ventilation, and air conditioning (HVAC) devices of the energy plant, each set of elements of the incidence matrix in a first direction associated with a corresponding HVAC device, each set of elements of the incidence matrix in a second direction associated with a corresponding node;

determining schematic relationships of the plurality of HVAC devices of the energy plant, each HVAC device configured to operate according to a corresponding operating parameter, wherein the schematic relationships are determined based on the incidence matrix;

determining a reduced subset of the plurality of HVAC devices based on the schematic relationships;

predicting thermodynamic states of the reduced subset;

determining a set of operating parameters of the plurality of HVAC devices based on the thermodynamic states; and

operating the plurality of HVAC devices according to the set of operating parameters.

11. The method of claim 10 , wherein determine the schematic relationships includes:

removing a first HVAC device of the plurality of HVAC devices;

detecting a stranded node after removing the first HVAC device; and

determining a second HVAC device coupled to the stranded node to be schematically dependent on the first HVAC device.

12. The method of claim 11 , wherein the stranded node has only one or more inlets or outlets after removing the first HVAC device.

13. The method of claim 10 , wherein determining the schematic relationships includes:

replacing a nonzero value of a first set of elements of the incidence matrix in the first direction with zero, the first set of elements associated with a HVAC device of the plurality of HVAC devices; and

detecting a second set of elements of the incidence matrix in the second direction having one of a first value corresponding to an inlet and a second value corresponding to an outlet but not both the first value and the second value, the detected second set of elements corresponding to a stranded node.

14. The method of claim 13 , wherein determining the schematic relationships includes:

detecting the second set of elements of the incidence matrix in the first direction having the first value, the second set of elements corresponding to another HVAC device of the plurality of HVAC devices schematically dependent on the HVAC device.

15. The method of claim 14 , wherein determining the schematic relationships includes:

replacing a nonzero value of the second set of elements of the incidence matrix with zero.

16. The method of claim 10 , further comprising:

identifying, from the plurality of HVAC devices, a first HVAC device to be turned off;

determining a second HVAC device schematically dependent on the first HVAC device; and

excluding the first HVAC device and the second HVAC device from the reduced subset of the plurality of HVAC devices.

17. The method of claim 10 , further comprising:

identifying, from the plurality of HVAC devices, a first HVAC device to be turned on;

determining a second HVAC device schematically dependent on the first HVAC device; and

adding the first HVAC device and the second HVAC device to the reduced subset of the plurality of HVAC devices in response to determining that the second HVAC device is schematically dependent on the first HVAC device.

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

determine schematic relationships of a plurality of heat, ventilation, and air conditioning (HVAC) devices of an energy plant based on connections of the plurality of HVAC devices, each HVAC device configured to operate according to a corresponding operating parameter, wherein the schematic relationships are determined by:

removing a HVAC device of the plurality of HVAC devices,

detecting a stranded node after removing the HVAC device, and

determining another HVAC device coupled to the stranded node to be schematically dependent on the HVAC device;

determine a reduced subset of the plurality of HVAC devices based on the schematic relationships;

predict thermodynamic states of the reduced subset;

determine a set of operating parameters of the plurality of HVAC devices based on the thermodynamic states; and

operate the plurality of HVAC devices according to the set of operating parameters.