System and method for chiller efficiency modeling and efficiency-based staging determination

Abstract

A multi-compressor chiller system can be effectively operated by determining real-time efficiency curves for the currently operating compressors and any compressors that can be added to meet demand, and using these efficiency curves to determine changes in compressor operation to increase efficiency in meeting chiller demand. The efficiency curves can be parabolic curves. Data for determining the efficiency curves can be obtained from operation at various lift points and various load points within these lift points. The efficiency curves can be solved to find intersections of possible staging points that can exist for adding or subtracting compressors in operation to effectively meet demand. This operation can be automated by a controller of a control system for the multi-compressor chiller system.

Description

Technical Field

[0001] This application relates to systems and methods for modeling the efficiency of coolers in a multi-cooler system and controlling the coolers in use based on the modeled efficiency. Background Technology

[0002] A cooler system may include multiple working fluid loops to provide cooling to the cooler's process fluid, such as cooling water, which is then used to cool the space. Each working fluid loop includes a compressor. As cooling demand changes, the load on the compressors also changes, as does the number of compressors in use. Compressor efficiency also varies with compressor load and compressor lift (the temperature or pressure difference between the condenser and evaporator in the loop, including the compressor). Therefore, the number of compressors required to meet cooling demand varies. Summary of the Invention

[0003] This application relates to systems and methods for modeling the efficiency of coolers in a multi-cooler system and controlling the coolers in use based on the modeled efficiency.

[0004] Real-time modeling of compressor efficiency based on cooler requirements and the resulting required lift and load allows compressor selection to consider the impact of lift and load on compressor efficiency. From the compressor efficiency model, the overall efficiency of the cooler system can be determined, and compressors can be selected based on improving this overall efficiency, refining compressor selection and staging, thereby providing higher efficiency for the cooler system.

[0005] In particular, using parabolic models for compressor efficiency at specific compressor lift conditions simplifies calculations while maintaining accuracy. This allows for real-time calculation of compressor efficiency, and these models can be easily combined to determine the composite efficiency of a set of operating compressors to meet specific cooler requirements. The parameters of these parabolic models can be based on the compressor efficiency observed for each compressor during various lift and load conditions.

[0006] In one embodiment, a method of operating a cooler system comprising multiple compressors includes receiving cooler demand and determining real-time efficiency curves for each of the multiple compressors currently in operation in the cooler system. The method further includes determining capacity-based operation changes based on the efficiency curves and cooler demand, and operating the cooler system according to the capacity-based operation changes.

[0007] In one embodiment, the method further includes determining the real-time efficiency curves of one or more compressors that are not currently in operation among a plurality of compressors. In one embodiment, a capacity change operation includes starting up at least one of the one or more compressors that are not currently in operation among a plurality of compressors.

[0008] In one embodiment, capacity change operation includes stopping the operation of at least one of the currently operating compressors of the cooler system. In another embodiment, capacity change operation includes changing the load of at least one of the currently operating compressors of the cooler system.

[0009] In one embodiment, each real-time efficiency curve is a parabolic function.

[0010] In one embodiment, determining capacity change operation includes determining a composite efficiency curve based on the efficiency curves of each of the plurality of compressors currently in operation in the cooler system. In one embodiment, the composite efficiency curve is further based on the efficiency curve of at least one compressor in the cooler system that is not currently in operation.

[0011] In one embodiment, determining capacity change operation includes solving for grading points, where grading points define when to start operation of compressors that are not currently in operation or when to stop operation of compressors that are currently in operation.

[0012] In one embodiment, the method further includes obtaining selection data by measuring efficiency data of each of a plurality of compressors at each of a plurality of load points within each of a plurality of lift points, wherein the determination of the real-time efficiency curve is based on the selection data.

[0013] In one embodiment, a control system for a cooler system comprising multiple compressors includes a controller. The controller is configured to receive cooler demand and determine a real-time efficiency curve for each of the multiple compressors currently in operation in the cooler system. The controller is also configured to determine capacity-changing operation based on the efficiency curves and cooler demand, and to guide the operation of the cooler system according to the capacity-changing operation.

[0014] In one embodiment, the controller is further configured to determine the real-time efficiency curves of one or more compressors that are not currently in operation among the plurality of compressors. In one embodiment, a capacity change operation includes starting at least one of the one or more compressors that are not currently in operation among the plurality of compressors. In one embodiment, a capacity change operation includes stopping at least one of the compressors that are currently in operation in the cooler system.

[0015] In one embodiment, capacity change operation includes changing the load of at least one of the compressors currently operating in the cooler system.

[0016] In one embodiment, each real-time efficiency curve is a parabolic function.

[0017] In one embodiment, the controller is configured to determine a composite efficiency curve based on the efficiency curve of each of the plurality of compressors currently in operation in the cooler system, and capacity change operation is based on the composite efficiency curve.

[0018] In one embodiment, the composite efficiency curve is further based on the efficiency curve of at least one compressor in the cooler system that is not currently in operation.

[0019] In one embodiment, the controller is configured to solve for gradation points, where gradation points define when to start the operation of a compressor that is not currently running or when to stop the operation of a compressor that is currently running.

[0020] In one embodiment, the cooler system includes multiple compressors and a control system as described herein. Attached Figure Description

[0021] Figure 1 A schematic diagram of a cooler system according to an embodiment is shown.

[0022] Figure 2 A flowchart of a method for determining a model of a cooler according to an embodiment is shown.

[0023] Figure 3 A flowchart of a method for selecting a cooler to use, according to an embodiment, is shown.

[0024] Figure 4 An example of an efficiency curve based on an embodiment including gradation points is shown. Detailed Implementation

[0025] This disclosure relates to systems and methods for modeling the efficiency of coolers in a multi-cooler system and controlling the coolers in use based on the modeled efficiency.

[0026] Figure 1 A schematic diagram of a cooler system according to an embodiment is shown. The cooler system 100 includes a plurality of cooler loops 102a-n. Each cooler loop 102a-n includes a compressor 104a-n, a condenser 106a-n, an expander 108a-n, and an evaporator 110a-n. Each of the evaporators 110a-n is configured to exchange heat with a cooler process fluid line 112, such that any one or all of the evaporators 110a-n can absorb heat from the cooler process fluid line 112. The cooler process fluid line 112 is configured to deliver cooler process fluid from the cooler system 100 to a cooling load 114 and then back to the cooler system 100. A controller 116 can direct the operation of each of the cooler loops 102a-n.

[0027] Cooler system 100 is a system for providing cooling to a process fluid to provide cooling to a cooling load 114. Cooler system 100 includes a plurality of cooler loops 102a-n, each configured to absorb heat from the process fluid. Any number of cooler loops 102a-n can actively cool the process fluid at specific times. In one embodiment, valves and fluid lines can be configured to bypass cooler loops 102a-n that are not in operation. The process fluid can be, for example, water, ethylene glycol, mixtures thereof, or any other suitable fluid used to be cooled at cooler loops 102a-n and absorb heat at the cooling load 114. The process fluid may include one or more additives for, for example, lowering the freezing temperature of the process fluid.

[0028] Cooler circuits 102a-n are individual refrigeration circuits, each configured to absorb heat from the process fluid. Cooler circuits 102a-n can be arranged in series, parallel, or a mixed arrangement relative to the flow of the process fluid, including some cooler circuits 102a-n in series and others in parallel. Each cooler circuit 102a-n includes a compressor 104a-n, a condenser 106a-n, an expander 108a-n, and an evaporator 110a-n. In one embodiment, each cooler circuit 102a-n may include the same components. In one embodiment, at least some cooler circuits 102a-n differ in at least one component, such as respective compressors 104a-n with different designs and / or characteristics (e.g., capacity, etc.).

[0029] Each of the compressors 104a-n is a compressor configured to compress the working fluid of the corresponding cooler circuit 102a-n. Each of the compressors 104a-n can be any suitable compressor, such as a centrifugal compressor, screw compressor, scroll compressor, etc., as non-limiting examples. In one embodiment, each of the compressors 104a-n is identical to each other. In one embodiment, each of the compressors 104a-n may have different rated capacities and / or load characteristics.

[0030] Each of the condensers 106a-n is a heat exchanger configured to allow heat to be discharged from the working fluid compressed by the respective compressor 104a-n. As a non-limiting example, heat can be discharged to the surrounding environment of the condenser 106a-n or to another fluid loop, for example, for heat recovery.

[0031] Each of the expanders 108a-n is configured to expand the working fluid after the working fluid has dissipated heat at the corresponding condenser 106a-n. The expanders 108a-n can be any suitable structure or combinations thereof for expanding the working fluid, such as an expansion valve, one or more expansion orifices, etc.

[0032] Each of the evaporators 110a-n is a heat exchanger configured to allow the working fluid expanding at the respective expander 108a-n to absorb heat from the process fluid of the cooler system 100. Each of the evaporators 110a-n may be connected to the same process fluid flow, such that the process fluid is further cooled by each successive evaporator 110a-n through which it passes. In one embodiment, the evaporators 110a-n may be connected to each other using a combination of fluid lines and valves that allow selective bypassing of any one of the evaporators 110a-n.

[0033] Cooler process fluid line 112 is a fluid line configured to deliver process fluid from cooler loops 102a-n to cooling loads 114 and back from cooling loads 114 to cooler loops 102a-n. Cooling load 114 is one or more devices that dissipate heat to the process fluid. In an embodiment, cooling load 114 may be one or more terminal devices including heat exchangers for cooling air in one or more conditioned spaces served by cooler system 100.

[0034] Controller 116 is configured to direct the operation of cooler system 100, particularly to operate a specific compressor selected from compressors 104a-n. Controller 116 may optionally be further configured to control valves guiding process fluids of cooler system 100 such that they pass along a route only through those evaporators 110a-n in the currently operating cooler loops 102a-n. Controller 116 may include one or more processors, one or more memories, one or more network inputs / outputs, and storage. It should be understood that controller 116 may further include additional components. Controller 116 may be operatively connected to compressors 104a-n such that controller 116 can receive power consumption data and / or issue commands to compressors 104a-n. Controller 116 may also be operatively connected to valves that allow process fluids to selectively bypass evaporators 110a-n. The operative connection may be any suitable wired or wireless connection that allows the transmission of data and / or commands to or from controller 116 and connected compressors 104a-n and / or valves. Non-limiting examples of operational connections include wired or wireless communication according to any suitable known standard. In one embodiment, controller 116 may further control one or more pumps 118 included in cooler system 100, such as pumps 118 that circulate process fluid between cooling load 114 and cooler loops 102a-n.

[0035] In one embodiment, controller 116 may be configured to map each of compressors 104a-n to operate at various load points and various lift points in order to generate efficiency data. The efficiency data may be, for example, power consumption at predetermined lift and load points. Controller 116 may also be configured to store the obtained efficiency data for subsequent operational control, such as using it to calculate efficiency curves, such as coefficients of performance, which can be used to determine the efficiency of the compressor under specific load and lift conditions. The efficiency data may be represented as a parabolic curve of efficiency as a function of load under specific lift conditions.

[0036] In one embodiment, controller 116 may be configured to control the gradation of compressors 104a-n using an efficiency model of the compressors 104a-n to effectively address the cooling demand of cooling load 114. Controller 116 may use an efficiency curve determined by operational testing as described above as an efficiency model, a predetermined efficiency model, or any other suitable representation of the efficiency of compressors 104a-n varying with lift and load. Controller 116 may receive the cooling demand of cooling load 114. Cooling demand is a value representing the amount of cooling that cooler circuits 102a-n must provide to cool cooling load 114. Cooling demand may be based, for example, on the desired exit process fluid temperature of cooler circuits 102a-n and the return process fluid temperature from cooling load 114 back to cooler circuits 102a-n, as well as subsequent flow of the process fluid. The efficiency model may be used to control the operation of one or more of compressors 104a-n to meet the cooling demand. In one embodiment, control of compressors 104a-n may include selecting a load level for the currently operating compressor 104a-n. In one embodiment, controlling the compressors 104a-n may include selecting one or more compressors 104a-n to operate. In one embodiment, selecting the compressor to operate may include selecting one or more additional compressors from the compressors 104a-n to operate in conjunction with the currently operating compressors in the compressors 104a-n. In one embodiment, the compressor selection may be based on a composite efficiency curve. The composite efficiency curve may be determined based on a combination of the efficiency curves of at least some of the compressors in the compressors 104a-n, such as the currently operating compressor, the currently operating compressor plus the next added compressor, or the currently operating compressors excluding the next subtracted compressor. Selecting the compressor to operate can be performed such that the selected compressor operating reduces or minimizes the energy consumption required to meet cooling requirements.

[0037] Figure 2A flowchart of a method for determining a compressor model according to an embodiment is shown. Method 200 includes operating the compressor 202 at each of a plurality of load points within each of a plurality of lift points, and recording efficiency data 204 at each of the plurality of load points within each of the plurality of lift points. The efficiency data used at 204 can be used to determine one or more efficiency curves 206 representing the compressor efficiency under specific load and lift conditions.

[0038] The compressor to be modeled operates at point 202. The operation of compressor 202 is performed at each of a plurality of different load points and at each of a plurality of lift points. The operation at the various load and lift points can be operation at these varying load and lift points that occur during normal compressor operation. In one embodiment, the compressor operation can be directed to provide operation at the lift and / or load points where data is required. Each of the plurality of load points is a predetermined load level at which the compressor is to operate. Each of the plurality of lift points represents a different compressor lift condition under which the compressor being modeled can operate. The lift condition can be characterized by the temperature or pressure difference between the condenser and evaporator of the compressor loop.

[0039] Efficiency data is recorded at 204 points for use at each load point and corresponding lift point. The efficiency data can be, for example, the power consumption of the compressor being modeled under specific load and lift conditions. In one embodiment, the efficiency data is the compressor's coefficient of performance.

[0040] An efficiency curve for the compressor being modeled can be determined at point 206 for each lift point. The efficiency curves can be used to simulate the compressor's efficiency at different load levels across various lift points. In one embodiment, each efficiency curve is a discrete curve for a specific lift point. The efficiency curve of a particular compressor may vary with lift conditions. The efficiency curve can represent the relationship between compressor load and compressor efficiency under specific lift conditions. The efficiency curve can be a parabolic curve. Method 200 can be performed by each compressor included in the cooler system, such as those discussed above. Figure 1 Each compressor 104a-n in the cooler system 100 shown is illustrated. Efficiency curves at different load points can be used to determine the parameters defining the parabola of the efficiency curve at each lift point. The parabola can be a graph of efficiency, where it provides the peak efficiency, the load at which peak efficiency is achieved, and the width of the curve indicating the rate at which efficiency decreases from the peak as the load changes.

[0041] Figure 3A flowchart of a method for selecting a cooler to use according to an embodiment is shown. Method 300 includes receiving cooler demand data 302, determining the efficiency curve of each compressor currently in operation 304, optionally determining the efficiency curve of one or more compressors not in operation 306, determining a capacity change operation 308, and operating the cooler system 310 according to the capacity change operation.

[0042] Cooler demand data is received at 302. Cooler demand is a value indicating the load from the compressor required to meet the cooling load, such as maintaining the exit temperature of the process fluid at the final cooler loop of the cooler system before it is directed to the cooling load. In one embodiment, cooler demand data may be based on the setpoint temperature and the process fluid temperature, where the process fluid enters the first cooler loop or any other suitable point downstream of the cooling load and the subsequent flow of the process fluid.

[0043] The efficiency curve of the currently operating compressor is determined at point 304. The efficiency curve can be determined based on a compressor model, for example, by generating it using the method described above (200). Figure 2 The model is illustrated. For example, the model can be determined by using the current compressor lift conditions to determine the parameters of a function representing the relationship between compressor load and compressor efficiency. In one embodiment, this function is a parabolic function. The efficiency curve determined at 304 can be determined based on the specific lift conditions of each respective compressor and using the relevant efficiency curve for those lift conditions. In one embodiment, the efficiency curves determined at 304 can be combined into a composite efficiency curve. In one embodiment, the composite efficiency curve can omit one or more compressors that may shut down in response to a cooler demand received at 302.

[0044] Optionally, the efficiency curve of a compressor that is not currently in operation can also be determined at 306. The efficiency curves of one or more compressors identified as potentially activated to meet the cooler demand received at 302 can be determined. The efficiency curve can be determined at 306 in the same manner as the efficiency curve of a currently operating compressor is determined at 304. In one embodiment, if a compressor is in operation, the efficiency curve can be determined at 306 by selecting a relevant efficiency curve for the compressor's predicted lift. In one embodiment, the efficiency curves determined at 306 can be combined into a composite efficiency curve that also includes the efficiency curve determined at 304.

[0045] Capacity change operation is determined at 308. Capacity change operation can be any appropriate change in the operation of the compressors in use to meet the cooler demand received at 302, such as by changing the load of one or more compressors currently in operation, starting the operation of a compressor that is not currently in operation, or stopping the operation of a currently running compressor. Capacity change operation can be determined based on efficiency curves determined at 304 and optionally at 306 to determine an effective combination and / or operation of compressors to meet the cooler demand received at 302. An effective combination can be a combination of compressors and their operation that provides higher efficiency and / or lower energy consumption compared to other possible combinations or operations capable of meeting the cooler demand received at 302. In one embodiment, an effective combination is a combination of compressors or their operation that provides the maximum efficiency and / or minimum energy consumption to meet the cooler demand received at 302. In one embodiment, the combination of compressors for capacity change operation can be determined by solving a system of equations defining the efficiency curves to identify the gradation points where one or more specific compressors of the cooler system should be started or stopped.

[0046] The cooler system 310 operates according to capacity change operation. The compressors can start or stop operating based on the capacity change operation determined at 308 to achieve compressor selection and / or specific compressor operation. The controller can issue commands to instruct the compressors of the cooler system to operate according to capacity change operation. Capacity change operation may include stopping the operation of one or more compressors, starting the operation of one or more compressors, and / or selecting specific operating parameters, such as speed, load, temperature setpoint, flow rate, etc., within the cooler system.

[0047] Figure 4 An example of an efficiency curve based on an embodiment including gradation points is shown. Figure 4 In the diagram, efficiency is plotted as a function of system load for various cooler loop operating possibilities. Figure 4 The efficiency metric used is the coefficient of performance (COP), with loads measured in tons. Understandably, Figure 4This is a general representation of the efficiency curve, and the specific values ​​and locations of the step points may vary due to system design, installation details, or any other suitable conditions that may affect a particular load-efficiency relationship. The current operating curve 400 is the composite efficiency curve of the cooler system when the currently operating cooler loop is in use. The reduced operating curve 402 is the composite efficiency curve of the cooler system when the currently operating cooler loop is in use (excluding the next subtracted cooler loop that stops operating). The increased operating curve 404 is the composite efficiency curve of the cooler system when the currently operating cooler loop and the next added cooler loop are in use. Each of the current operating curve 400, reduced operating curve 402, and increased operating curve 404 can be determined based on the efficiency curve determined for each compressor, for example, by... Figure 2 The method shown and described above. The determination of the composite efficiency of each of curves 400, 402, and 404 can be based on the determination of the composite efficiency curves described herein.

[0048] The cooler subtraction step point 406 can exist at the intersection of the current operating curve 400 and the reduced operating curve 402. Under loads below the cooler subtraction step point 406, the cooler system as a whole is more efficient when the next subtracted cooler loop stops operating. Therefore, when the load is at or below the cooler subtraction step point 406, it can be used to control the cooler system by stopping the operation of the next subtracted cooler. In embodiments, the cooler subtraction step point 406 and / or the curves 400 and 402 from which it is determined can be dynamically calculated to reflect the recent performance of each cooler loop or to compare different combinations of cooler loops.

[0049] A cooler addition step point 408 can exist at the intersection of the current operating curve 400 and the increasing operating curve 404. Under loads above the cooler addition step point 408, the cooler system as a whole is more efficient when the next added cooler loop is added to the currently operating cooler loop. Therefore, when the load exceeds or will exceed the cooler addition step point 408, the cooler addition step point 408 can be used to control the cooler system by initiating the operation of the next added cooler. In embodiments, the cooler addition step point 408 and / or the curves 400 and 404 from which the cooler addition step point 408 is determined can be dynamically calculated to reflect the recent performance of each cooler loop or to compare different combinations of cooler loops.

[0050] aspect:

[0051] It should be understood that any one of aspects 1-10 can be combined with any one of aspects 11-20.

[0052] Aspect 1. A method of operating a cooler system comprising multiple compressors, the method comprising:

[0053] Receive cooler requirements;

[0054] Determine the real-time efficiency curve of each of the plurality of compressors currently in operation in the cooler system;

[0055] Determine capacity change operation based on efficiency curves and cooler demand; and

[0056] The cooler system operates according to capacity changes.

[0057] Aspect 2, according to the method of aspect 1, also includes determining the real-time efficiency curves of one or more compressors that are not currently in operation among a plurality of compressors.

[0058] Aspect 3, according to the method of aspect 2, wherein capacity change operation includes starting operation of at least one of one or more compressors that are not currently in operation among a plurality of compressors.

[0059] Aspect 4, the method according to any one of Aspects 1-3, wherein the capacity change operation includes stopping the operation of at least one of the currently operating compressors of the cooler system.

[0060] Aspect 5, the method according to any one of Aspects 1-4, wherein the capacity change operation includes changing the load of at least one of the currently operating compressors of the cooler system.

[0061] Aspect 6: Based on any one of Aspects 1-5, where each real-time efficiency curve is a parabolic function.

[0062] Aspect 7. The method of any one of Aspects 1-6, wherein determining the capacity change operation includes determining the composite efficiency curve based on the efficiency curves of each of the multiple compressors currently in operation of the cooler system.

[0063] Aspect 8, the method according to aspect 7, wherein the composite efficiency curve is further based on the efficiency curve of at least one currently non-operational compressor of the cooler system.

[0064] Aspect 9, according to the method of any one of Aspects 1-8, wherein determining capacity change operation includes solving for grading points, wherein grading points define when to start operation of a compressor that is not currently running or when to stop operation of a compressor that is currently running.

[0065] Aspect 10. The method according to any one of Aspects 1-9 further includes obtaining selection data by measuring efficiency data of each of a plurality of compressors at each of a plurality of load points within each of a plurality of lift points, wherein the determination of the real-time efficiency curve is based on the selection data.

[0066] Aspect 11. A control system for a cooler system comprising multiple compressors, the control system comprising:

[0067] The controller is configured to:

[0068] Receive cooler requirements;

[0069] Determine the real-time efficiency curve of each of the plurality of compressors currently in operation in the cooler system;

[0070] Determine capacity change operation based on efficiency curves and cooler demand; and

[0071] The operation of the cooler system is guided by changes in capacity.

[0072] Aspect 12, the control system according to aspect 11, wherein the controller is further configured to determine the real-time efficiency curves of one or more compressors that are not currently in operation among the plurality of compressors.

[0073] Aspect 13. The control system according to aspect 12, wherein the capacity change operation includes starting operation of at least one of the one or more compressors that are not currently in operation among the plurality of compressors.

[0074] Aspect 14. The control system according to any one of Aspects 11-13, wherein the capacity change operation includes stopping the operation of at least one of the currently operating compressors of the cooler system.

[0075] Aspect 15. The control system according to any one of Aspects 11-14, wherein the capacity change operation includes changing the load of at least one of the compressors currently in operation of the cooler system.

[0076] Aspect 16. A control system based on any one of Aspects 11-15, wherein each real-time efficiency curve is a parabolic function.

[0077] Aspect 17. The control system according to any one of Aspects 11-16, wherein the controller is configured to determine a composite efficiency curve based on the efficiency curve of each of the plurality of compressors currently in operation of the cooler system, and the capacity change operation is based on the composite efficiency curve.

[0078] Aspect 18. The control system according to aspect 17, wherein the composite efficiency curve is also based on the efficiency curve of at least one currently non-operating compressor of the cooler system.

[0079] Aspect 19. The control system according to any one of Aspects 11-18, wherein the controller is configured to solve for a gradation point, wherein the gradation point defines when to start the operation of a compressor that is not currently running or when to stop the operation of a compressor that is currently running.

[0080] Aspect 20: A cooler system comprising a plurality of compressors and a control system according to any one of aspects 11-19.

[0081] The examples disclosed in this application are to be considered illustrative rather than limiting in all respects. The scope of the invention is indicated by the appended claims rather than by the foregoing description; and all variations within the equivalent meaning and scope of the claims are intended to be included therein.

Claims

1. A method for operating a cooler system comprising multiple compressors, characterized in that, The method includes: Receive cooler requirements; Determine the real-time efficiency curve of each of the plurality of compressors currently in operation in the cooler system; A composite efficiency curve is determined based on a combination of the real-time efficiency curves of each of the plurality of compressors currently in operation in the cooler system. Based on the composite efficiency curve and the cooler requirements, capacity change operation is determined; and The cooler system is operated according to the capacity change.

2. The method according to claim 1, characterized in that, It also includes determining the real-time efficiency curves of one or more compressors that are not currently in operation among the plurality of compressors.

3. The method according to claim 2, characterized in that, The capacity change operation includes starting at least one of one or more compressors that are not currently in operation.

4. The method according to claim 1, characterized in that, The capacity change operation includes stopping the operation of at least one of the compressors currently in operation in the cooler system.

5. The method according to claim 1, characterized in that, The capacity change operation includes changing the load of at least one of the compressors currently in operation in the cooler system.

6. The method according to claim 1, characterized in that, Each real-time efficiency curve is a parabolic function.

7. The method according to claim 1, characterized in that, The composite efficiency curve is further based on the efficiency curve of at least one compressor of the cooler system that is not currently in operation.

8. The method according to claim 1, characterized in that, Determining the capacity change operation includes solving for grading points, where the grading points define when to start the operation of a compressor that is not currently running or when to stop the operation of a compressor that is currently running.

9. The method according to claim 1, characterized in that, It also includes obtaining selection data by measuring the efficiency data of each of the plurality of compressors at each of the plurality of load points within each of the plurality of lift points, wherein the determination of the real-time efficiency curve is based on the selection data.

10. A control system for a cooler system comprising multiple compressors, characterized in that, The control system includes: The controller is configured to: Receive cooler requirements; Determine the real-time efficiency curve of each of the plurality of compressors currently in operation in the cooler system; A composite efficiency curve is determined based on a combination of the real-time efficiency curves of each of the plurality of compressors currently in operation in the cooler system. Based on the composite efficiency curve and the cooler requirements, capacity change operation is determined; and The operation of the cooler system is guided by changes in capacity.

11. The control system according to claim 10, characterized in that, The controller is also configured to determine the real-time efficiency curves of one or more compressors that are not currently in operation among the plurality of compressors.

12. The control system according to claim 11, characterized in that, The capacity change operation includes starting at least one of the one or more compressors that are not currently in operation.

13. The control system according to claim 10, characterized in that, The capacity change operation includes stopping the operation of at least one of the compressors currently in operation in the cooler system.

14. The control system according to claim 10, characterized in that, The capacity change operation includes changing the load of at least one of the compressors currently in operation in the cooler system.

15. The control system according to claim 10, characterized in that, Each real-time efficiency curve is a parabolic function.

16. The control system according to claim 10, characterized in that, The composite efficiency curve is further based on the efficiency curve of at least one compressor of the cooler system that is not currently in operation.

17. The control system according to claim 10, characterized in that, The controller is configured to solve for gradation points, wherein the gradation points define when to start the operation of a compressor that is not currently running or when to stop the operation of a compressor that is currently running.

18. A cooler system, characterized in that, It includes multiple compressors and the control system according to claim 10.

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