Central plant with secondary strong prevention

1. A central plant, comprising:

a plurality of subplants comprising a chiller configured to output supply water at a supply water temperature;

a sensor configured obtain a measurement of the supply water temperature; and

a control system configured to:

calculate an additional load factor based on the measurement of the supply water temperature and a supply water temperature setpoint;

obtain an actual load for the chiller;

calculate an effective load based on the additional load factor and the actual load;

generate load allocations for the plurality of subplants based on the effective load; and

control the plurality of subplants to operate in accordance with the load allocations.

2. The central plant of claim 1 , wherein the additional load factor is positive when the supply water temperature deviates from the supply water temperature setpoint.

3. The central plant of claim 1 , wherein the control system is configured to calculate the additional load factor by:

setting additional load factor to zero in response to the measurement of the supply water temperature being greater than or equal to the supply water temperature setpoint; and wherein setting the additional load factor to a non-zero value when the measurement of the supply water temperature is less than a sum of the supply water temperature setpoint and an offset.

4. The central plant of claim 3 , wherein, when the additional load factor is non-zero, the additional load factor comprises a scaling factor multiplied by a difference between the measurement of the supply water temperature and a sum of the supply water temperature setpoint and an offset.

5. The central plant of claim 1 , wherein the control system is configured to generate load allocations based on the effective load by:

generating a predicted load for the central plant based on the effective load; and allocating the predicted load amongst the plurality of subplants.

6. The central plant of claim 1 , wherein the additional load factor causes the control system to generate the load allocations for the plurality of subplants by increasing a load allocation for a first device of the plurality of subplants to compensate for a failure of the chiller to meet a load allocated to the chiller.

7. A method for controlling building equipment comprising a chiller, the method comprising:

operating the chiller to output supply water at a supply water temperature;

obtaining a measurement of the supply water temperature;

calculating an additional load factor based on the measurement of the supply water temperature and a supply water temperature setpoint;

obtaining an actual load for the chiller;

calculating an effective load based on the additional load factor and the actual load;

generating load allocations for the building equipment based on the effective load; and

controlling the building equipment in accordance with the load allocations.

8. The method of claim 7 , wherein the additional load factor is positive when the supply water temperature deviates from the supply water temperature setpoint.

9. The method of claim 7 , wherein calculating the additional load factor comprises setting the additional load factor to zero in response to the measurement of the supply water temperature being greater than or equal to the supply water temperature setpoint.

10. The method of claim 9 , wherein calculating the additional load factor comprises, in response to the measurement of the supply water temperature being less than a sum of the supply water temperature setpoint and an offset:

calculating the sum of the supply water temperature setpoint and the offset;

determining a difference between the measurement of the supply water temperature and the sum; and

multiplying the difference by a scaling factor.

11. The method of claim 7 , wherein generating load allocations comprises:

generating a predicted load for the building equipment based on the effective load; and

allocating the predicted load amongst the building equipment.

12. The method of claim 7 , wherein generating load allocations for the building equipment based on the effective load comprises increasing a load allocated to a first device of the building equipment to compensate for a failure of the chiller to meet a load allocated to the chiller.

13. A method for controlling a central plant, comprising:

operating a first subplant of the central plant to output a first resource with a measureable characteristic;

obtaining a measurement of the measureable characteristic at an output of the first subplant and a setpoint for the measureable characteristic at the output of the first subplant;

calculating an additional load factor based on the measurement and the setpoint;

obtaining an actual load for the first subplant;

calculating an effective load for the first subplant based on a sum of the actual load and the additional load factor;

generating load allocations for the central plant based on the effective load; and

controlling the central plant based on the load allocations.

14. The method of claim 13 , comprising controlling the first subplant with a control loop configured to drive the measureable characteristic towards the setpoint.

15. The method of claim 13 , wherein the additional load factor is positive when the measurement deviates from the setpoint.

16. The method of claim 13 , wherein calculating the additional load factor comprises setting the additional load factor to zero in response to the measurement being greater than or equal to the setpoint.

17. The method of claim 16 , wherein calculating the additional load factor comprises, in response to the measurement being less than a sum of the setpoint and an offset,

calculating the sum of the supply water temperature setpoint and the offset;

determining a difference between the measurement and the sum; and

multiplying the difference by a scaling factor.

18. The method of claim 13 , wherein generating load allocations comprises:

generating a predicted load for the central plant based on the effective load; and

allocating the predicted load amongst a plurality of subplants of the central plant, the plurality of subplants comprising the first subplant.

19. The method of claim 13 , generating load allocations for the central plant based on the effective load comprises increasing a load allocated to a second subplant of the central plant to compensate for a failure of the first subplant to meet a load allocated to the first subplant.

20. The method of claim 13 , wherein the first subplant comprises an electric centrifugal chiller.