Adaptive PID control for chilled water CRAC units

1. A computer room air conditioning (CRAG) unit incorporating a proportional, integral, derivative (PID) control system for controlling a cooling component of a cooling unit to assist in controlling a supply air temperature of air discharged from the CRAC unit, the system including:

a supply air temperature sensor;

a PID controller in communication with the supply air temperature sensor;

a memory in communication with the PID controller;

a plurality of look-up tables stored in the memory and setting forth different proportional “P”, integral (“I”) and derivative (“D”) gains based on an operating variable associated with operation of the cooling component of the cooling unit;

the cooling component including an electrically adjustable component being in communication with the PID controller and helping to control performance of the CRAG unit at least in part in response to the supply air temperature; and

wherein the PID controller uses the look-up tables together with a limited slope calculation which defines projected behavior of the operating variable, to adjust at least one of the P, I and D gains in real time, in controlling the cooling component to modify performance of the CRAC unit.

2. The system of claim 1 , further comprising a plurality of algorithms stored in the memory to help determine the gains to be used in controlling the cooling component.

3. The system of claim 2 , wherein the limited slope calculation defines the projected behavior of the operating variable, to determine different P, I and D gains to be used in controlling the PID controller within a plurality of different operating regions of the operating variable.

4. The system of claim 1 , wherein the cooling component controlled by the system comprises a chilled water (CW) valve which controls a flow of chilled water to the CRAC unit.

5. The system of claim 1 , wherein the cooling component controlled by the system comprises a motor driven unit fan operably associated with the cooling unit.

6. The system of claim 1 , wherein the system demarcates a plurality of distinct operating points and operating regions for controlling the P, I and D gains.

7. A computer room air conditioning (CRAC) unit incorporating a proportional, integral, derivative (PID) control system for controlling a cooling component of the CRAC unit to assist in controlling a supply air temperature of air being discharged from the CRAC unit, the system including:

a PID controller;

a sensor configured to sense a temperature of air associated with operation of the CRAC unit and to provide an electrical signal to the PID controller;

a memory in communication with the PID controller;

a plurality of look-up tables stored in the memory and setting forth different proportional (“P”), integral (“I”) and derivative (“D”) gains based on an operating variable associated with operation of the cooling component;

a plurality of algorithms stored in the memory to help determine the gains to be used in controlling the cooling component;

the cooling component including at least one of a motor driven unit fan and an electrically adjustable chilled water (CW) valve, and being in bi-directional electrical communication with the PID controller and responsive to electrical signals from the PID controller such that the PID controller controls the cooling component to control performance of the CRAC unit in accordance with the air temperature; and

wherein the PID controller uses the look-up tables together with a limited slope calculation, wherein the limited slope calculation defines projected behavior of the operating variable to determine different P, I and D gains to be used by the PID controller in controlling performance of the CRAC unit, within a plurality of different operating regions of the operating variable.

8. The system of claim 7 , wherein the cooling component controlled by the system comprises the electrically adjustable chilled water (CW) valve which controls a flow of chilled water to the CRAC unit, wherein the air temperature comprises a supply air temperature being discharged by the CRAC unit.

9. The system of claim 7 , wherein the cooling component controlled by the system comprises the motor driven unit fan operably associated with the CRAC unit, wherein the air temperature comprises a remote air temperature at a load bank remote from the CRAC unit.

10. The system of claim 8 , wherein the system demarcates a plurality of distinct operating points and operating regions for controlling the P, I and D gains, including:

a predetermined low fan speed;

a predetermined high fan speed;

two predetermined medium fan speeds comprising medium 1 and medium 2 fan speeds, at points between the predetermined low fan speed and the predetermined high fan speed;

a low fan speed adapts region extending between the predetermined low fan speed and the medium 1 fan speed;

a high fan speed adapts region between the medium 2 fan speed and the predetermined high fan speed;

a medium 1 fan speed adapts region extending from the medium 1 fan speed to the midpoint between the medium 1 and medium 2 fan speeds; and

a medium 2 fan speed adapts region extending from the midpoint between the medium 1 and medium 2 fan speeds to the medium 2 fan speed.

11. The system of claim 7 , wherein the look-up tables each include:

three gain points for proportional gain P(1), P(2), P(3);

three gain points for integral gain I(1), I(2), I(3); and

three gain points for derivative gain D(1), D(2), D(3); and

wherein the algorithms determine which gain point or gain points to increase or decrease based on real time performance of the cooling component and a comparison of a connecting line slope with the limited slope calculation, wherein the connecting line slope defines projected performance of the cooling component based on real time data.

12. A method for controlling a computer room air conditioner (CRAC) unit in a manner such that operation of a cooling component of the CRAC unit is modified to assist in controlling a supply air temperature of air being discharged by the CRAC unit, the method including:

using a PID controller of the CRAC unit to control a proportional gain (P), an integral gain (I) and a derivative gain (D), wherein the proportion gain, the integral gain and the derivative gain are used to modify operation of the CRAC unit;

using a memory to communicate with the PID controller;

storing a plurality of look-up tables in the memory;

using the look-up tables to hold different proportional, integral and derivative gains based on an operating variable associated with operation of the cooling component; and

causing the PID controller to access the look-up tables and a limited slope calculation to determine projected operating data for the cooling component, wherein the cooling component includes at least one of a motor driven unit fan and an electrically adjustable chilled water (CW) supply valve, and to adjust at least one of the P, I and D gains for the cooling component in real time in response to evaluations of at least the projected operating data, to control the CRAC unit.

13. The method of claim 12 , wherein causing the PID controller to determine projected operating data for the cooling component comprises causing the PID controller to determine the projected operating data for control of a unit fan.

14. The method of claim 12 , wherein causing the PID controller to determine projected operating data for the cooling component comprises causing the PID controller to determine projected operating data for a position of a chilled water valve, where the chilled water valve controls a flow of water to the CRAC unit.

15. The method of claim 12 , wherein the look-up tables each include:

three gain points for proportional gain P(1), P(2), P(3);

three gain points for integral gain I(1), I(2), I(3); and

three gain points for derivative gain D(1), D(2), D(3); and

wherein the PID controller determines which gain point or gain points to increase or decrease based on real time performance of the cooling component and a comparison of a connecting line slope with the limited slope calculation, wherein the connecting line slope defines projected performance of the cooling component based on real time data.