Methods and systems for controlling a chiller system having a centrifugal compressor with a variable speed drive

Patent metadata

Field	Value
Publication number	US-2017356684-A1
Application number	US-201715687668-A
Country	US
Kind code	A1
Filing date	Aug 28, 2017
Priority date	Jan 25, 2013
Publication date	Dec 14, 2017
Grant date	—

Abstract

Methods and systems for controlling a chiller system to achieve control stability while maintaining optimum efficiency. Particularly, methods and systems for controlling a centrifugal compressor speed and an inlet guide vane position that establishes three distinct regions in the control path: (i) during initial unloading from full load, the inlet guide vane position is kept at a fully open position while the centrifugal compressor speed is changed to achieve the desired cooling capacity; (ii) between an inflection point and a transition point, keeping the centrifugal compressor speed constant while the inlet guide vane position is changed to achieve the desired cooling capacity; and (iii) between the transition point and zero cooling capacity, changing both the inlet guide vane position and the centrifugal compressor speed to achieve the desired cooling capacity.

First claim

1 . A method for controlling a chiller system that includes a centrifugal compressor with a variable speed drive, a chiller control unit and one or more inlet guide vanes, the method comprising:
the chiller control unit receiving first measurement data and second measurement data; determining a desired chiller capacity based on the first measurement data; determining a centrifugal compressor speed and an inlet guide vane position based on the second measurement data; generating a compressor speed command and an inlet guide vane command based on the determined centrifugal compressor speed and the determined inlet guide vane position; sending the compressor speed command to the variable speed drive of the centrifugal compressor and the inlet guide vane command to the centrifugal compressor to control the one or more inlet guide vanes.

2 . The method of claim 1 , wherein the first measurement data includes at least one of an evaporator leaving water temperature data and an evaporator entering water temperature data.

3 . The method of claim 1 , wherein the second measurement data includes at least one of an evaporator leaving water temperature data, an evaporator refrigerant temperature data, a condenser entering water temperature data, a condenser refrigerant pressure data, and the desired chiller capacity.

4 . The method of any of claim 1 , wherein determining the centrifugal compressor speed and the inlet guide vane position based on the second measurement data includes:
determining whether the desired chiller capacity is greater than a transition point; adjusting a centrifugal compressor speed to achieve the desired chiller capacity and setting an inlet guide vane position to a fully open inlet guide vane position when the desired chiller capacity is greater than the transition point; determining whether the desired chiller capacity is greater than an inflection point when the desired chiller capacity is not greater than the transition point; adjusting the inlet guide vane position to obtain the desired chiller capacity while the centrifugal compressor speed is kept constant when the desired chiller capacity is greater than the inflection point; and adjusting both the inlet guide vane position and the centrifugal compressor speed to obtain the desired chiller capacity when the desired chiller capacity is not greater than the inflection point.

5 . The method of claim 4 , further comprising initially starting the chiller system with the centrifugal compressor speed set at a maximum centrifugal compressor speed and an inlet guide vane position to the fully open inlet guide vane position.

6 . The method of claim 1 , wherein determining the centrifugal compressor speed and the inlet guide vane position based on the second measurement data includes:
determining whether the desired chiller capacity is greater than an inflection point; adjusting a centrifugal compressor speed to achieve the desired chiller capacity and setting an inlet guide vane position to a fully open inlet guide vane position when the desired chiller capacity is greater than the inflection point; and adjusting both the inlet guide vane position and the centrifugal compressor speed to obtain the desired chiller capacity when the desired chiller capacity is not greater than the inflection point.

7 . The method of claim 6 , further comprising initially starting the chiller system with the centrifugal compressor speed set at a maximum centrifugal compressor speed and an inlet guide vane position to the fully open inlet guide vane position.

8 . The method of claim 1 , wherein determining the centrifugal compressor speed and the inlet guide vane position based on the second measurement data includes:
determining whether the desired chiller capacity is greater than a transition point; adjusting a centrifugal compressor speed to achieve the desired chiller capacity and setting an inlet guide vane position to a fully open inlet guide vane position when the desired chiller capacity is greater than the transition point; and adjusting both the inlet guide vane position and the centrifugal compressor speed to obtain the desired chiller capacity when the desired chiller capacity is not greater than the transition point.

9 . The method of claim 8 , further comprising initially starting the chiller system with the centrifugal compressor speed set at a maximum centrifugal compressor speed and an inlet guide vane position to the fully open inlet guide vane position.

10 . A chiller system comprising:
a centrifugal compressor with a variable speed drive; one or more inlet guide vanes; and a chiller control unit that includes a capacity control component configured to receive first measurement data and determine a desired chiller capacity based on the first measurement data, and a multi-actuator control component configured to receive second measurement data and determine a centrifugal compressor speed and an inlet guide vane position based on the second measurement data, wherein the chiller control unit is configured to generate and send a centrifugal compressor speed command to the variable speed drive of the centrifugal compressor based on the determined centrifugal compressor speed and configured to generate and send an inlet guide vane position command to the centrifugal compressor to control the one or more inlet guide vanes based on the determined inlet guide vane position.

11 . The chiller system of claim 10 , wherein the first measurement data includes at least one of an evaporator leaving water temperature data and an evaporator entering water temperature data.

12 . The chiller system of claim 10 , wherein the second measurement data includes at least one of an evaporator leaving water temperature data, an evaporator refrigerant temperature data, a condenser entering water temperature data, a condenser refrigerant pressure data, and the desired chiller capacity.

13 . The chiller system of claim 10 , wherein the multi-actuator control component is configured to:
determine whether a desired chiller capacity is greater than a transition point; adjust a centrifugal compressor speed to achieve the desired chiller capacity and set an inlet guide vane position to a fully open inlet guide vane position when the desired chiller capacity is greater than the transition point; determine whether the desired chiller capacity is greater than an inflection point when the desired chiller capacity is not greater than the transition point; adjust the inlet guide vane position to obtain the desired chiller capacity while the centrifugal compressor speed is kept constant when the desired chiller capacity is greater than the inflection point; and adjust both the inlet guide vane position and the centrifugal compressor speed to obtain the desired chiller capacity when the desired chiller capacity is not greater than the inflection point.

14 . The chiller system of claim 13 , wherein the multi-actuator control component is configured to initially start the chiller system with the centrifugal compressor speed set at a maximum centrifugal compressor speed and an inlet guide vane position to the fully open inlet guide vane position.

15 . The chiller system of claim 10 , wherein the multi-actuator control component is configured to:
determine whether the desired chiller capacity is greater than an inflection point; adjust a centrifugal compressor speed to achieve the desired chiller capacity and set an inlet guide vane position to a fully open inlet guide vane position when the desired chiller capacity is greater than the inflection point; and adjus

Assignees

• Trane Int Inc

Inventors

• Sibik Lee L

Classifications

• F25B2700/21173

  at the outlet · CPC title

• F04D27/0261

  by varying driving speed · CPC title

• F04B49/103

  Responsive to speed · CPC title

• F25B2339/047

  Water-cooled condensers · CPC title

• F25B2700/21161

  of the fluid heated by the condenser · CPC title