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

Patent metadata

Field	Value
Publication number	US-9746228-B2
Application number	US-201414763455-A
Country	US
Kind code	B2
Filing date	Jan 24, 2014
Priority date	Jan 25, 2013
Publication date	Aug 29, 2017
Grant date	Aug 29, 2017

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

The invention claimed is:

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, wherein the second measurement data includes a condenser entering water temperature data and a condenser refrigerant pressure data;
a capacity control component of the chiller control unit determining a desired chiller capacity based on the first measurement data, wherein the desired chiller capacity is indicative of a load demanded on the chiller system; and
a multi-actuator control component of the chiller control unit determining a centrifugal compressor speed and an inlet guide vane position based on the second measurement data;
determining a normalized chiller capacity based on the desired chiller capacity; determining a normalized centrifugal compressor speed based on the centrifugal compressor speed;
determining a pressure coefficient that represents a static pressure and a kinetic energy of the centrifugal compressor;
determining an inflection point based on the normalized chiller capacity, the normalized centrifugal compressor speed, and the pressure coefficient;
determining an adjusted centrifugal compressor speed and an adjusted inlet guide vane position based on the normalized chiller capacity, the normalized centrifugal compressor speed and the pressure coefficient;
wherein the chiller control unit generates a compressor speed command and an inlet guide vane command based on the adjusted centrifugal compressor speed and the adjusted inlet guide vane position; and
sends 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; and
wherein determining the adjusted centrifugal compressor speed and the adjusted inlet guide vane position includes:
determining whether the desired chiller capacity is greater than the inflection point;
adjusting the centrifugal compressor speed to achieve the desired chiller capacity and setting the 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.

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 further includes at least one of an evaporator leaving water temperature data, an evaporator refrigerant temperature data, and the desired chiller capacity.

4. The method of claim 1 , wherein the second measurement data also includes an evaporator leaving water temperature data, an evaporator refrigerant temperature data, and the desired chiller capacity, and the method further including:
determining the centrifugal compressor speed and the inlet guide vane position based on the evaporator leaving water temperature data, the evaporator refrigerant temperature data, and the desired chiller capacity.

5. 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, wherein the desired chiller capacity is indicative of a load demanded on the chiller system,
and a multi-actuator control component configured to:
receive second measurement data that includes a condenser entering water temperature data and a condenser refrigerant pressure data,
determine a centrifugal compressor speed and an inlet guide vane position based on the condenser entering water temperature data and the condenser refrigerant pressure data,
determine a normalized chiller capacity based on the desired chiller capacity;
determine a normalized centrifugal compressor speed based on the centrifugal compressor speed;
determine a pressure coefficient that represents a static pressure and a kinetic energy of the centrifugal compressor;
determine an inflection point based on the normalized chiller capacity, the normalized centrifugal compressor speed, and the pressure coefficient;
determine an adjusted centrifugal compressor speed and an adjusted inlet guide vane position based on the normalized chiller capacity, the normalized centrifugal compressor speed and the pressure coefficient;

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 adjusted 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 adjusted inlet guide vane position;
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
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.

6. The chiller system of claim 5 , wherein the first measurement data includes at least one of an evaporator leaving water temperature data and an evaporator entering water temperature data.

7. The chiller system of claim 5 , wherein the second measurement data further includes at least one of an evaporator leaving water temperature data, an evaporator refrigerant temperature data and the desired chiller capacity.

8. The chiller system of claim 5 , wherein the multi-actuator control component is configured to receive an evaporator leaving water temperature data, an evaporator refrigerant temperature data, and the desired chiller capacity and configured to determine the centrifugal compressor speed and the inlet guide vane position based on the evaporator leaving water temperature data, the evaporator refrigerant temperature data, and the desired chiller capacity.

9. 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, wherein the second measurement data includes at least one of a condenser entering water temperature data and a condenser refrigerant pressure data;
a capacity control component of the chiller control unit determining a desired chiller capacity based on the first measurement data, wherein the desired chiller capacity is indicative of a load demanded on the chiller system; and
a multi-actuator control component of the chiller control unit determining a centrifugal compressor speed and an inlet guide vane position based on the second measurement data;
determining a normalized chiller capacity based on the desired chiller capacity; determining a normalized centrifugal compressor speed based on the centrifugal compressor speed;
determining a pressure coefficient that represen

Assignees

• Trane Int Inc

Inventors

• Sibik Lee L

Classifications

• F25B2700/21173

  at the outlet · CPC title

• F25B2339/047

  Water-cooled condensers · CPC title

• F04D27/0261

  by varying driving speed · CPC title

• F25B2700/197

  of the evaporator · CPC title

• F04B49/103

  Responsive to speed · CPC title