Compressor control process for variable cascade refrigeration system

Abstract

The invention relates to a method and apparatus for controlling a compressor in a cascade vapour compression system. The process may include controlling operation of the first compressor based on constant band control, and controlling operation of the second compressor based on proportional band control. If the first measurement is within a range associated with the first setpoint, controlling the first compressor based on the constant band control may include operating the compressor at a constant setting. If the first measurement is outside the range, it may also include proportionally adjusting operation of the first compressor. Further, controlling the second compressor based on proportional band control may include operating the compressor based on one of a plurality of proportional bands, each proportional band having a different proportionality coefficient. Controlling second compressor operation may also include switching between the proportional bands based on a second measured parameter.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is related to U.S. Application Serial No. (Agency Docket No. T11063910950US.1(0457.9) entitled “Cryogenic Storage System” and naming T.A. Lydick, Alex Roberts, Thomas A. Schoeppner, Benjamin T. Irwin, Mitchell J. Donnelly and Luke Schlicher as inventors and Trane Technologies Life Sciences LLC as applicant) and U.S. Application Serial No. (Agency Docket No. T11063910930US.1(0454.4) entitled “Defrost Fan Control” and naming T.A. Schoeppner, Alex Roberts, T.A. Lydick, Benjamin T. Irwin, Mitchell J. Donnelly and Luke Schlicher as applicant. A. Lydick and Mitchell J. Donnelly are named as inventors, and Trane Technologies Life Sciences LLC is named as applicant. Each of these applications was filed on the same day as the present application, and the entire contents of these applications are incorporated herein by reference. Technical Field

[0002] The present disclosure relates generally to improved control of compressors used to operate cascade refrigeration systems and is particularly applicable to cascade vapor compression systems having two or more compressors. Background Art

[0003] Climate control systems are used to adjust the climate of a conditioned space. Consequently, many systems typically include various components for controlling the temperature and other conditions associated with the conditioned space. In particular, climate control systems often include a compressor driven by a motor, the operation of which typically varies based on the conditioning load associated with the conditioned space.

[0004] To control the operation of the compressor, various control processes may be utilized. For example, the compressor motor may be controlled using a standard on / off operation. In other cases, when a variable frequency drive (VFD) is connected to the motor, a more complex control process may be utilized, perhaps using a proportional-integral (PI) control process to control the compressor operation.

[0005] However, these existing systems are insufficient to properly control climate control system compressors and balance competing demands, such as turndown requirements, energy efficiency requirements, and maintenance requirements. This is particularly true for cascade systems, where two refrigeration circuits operate in series to address the turndown load. Consequently, there is a need for improved compressor control processes for climate control systems, particularly for cascade vapor compression systems. Summary of the Invention

[0006] The present disclosure includes, but is not limited to, the following examples.

[0007] One embodiment is a method of controlling a cascade vapor compression system, the cascade vapor compression system including a first-stage compressor configured to circulate refrigerant in a first-stage refrigeration circuit and a second-stage compressor configured to circulate refrigerant in a second-stage refrigeration circuit, the method comprising: receiving a first measurement value that varies with time, the first measurement value indicating a first parameter associated with the cascade vapor compression system; receiving a second measurement value that varies with time, the second measurement value indicating a second parameter associated with the second-stage refrigeration circuit; controlling a speed of the first-stage compressor based on constant band control, wherein controlling the first-stage compressor based on constant band control comprises: when determining the first measurement value, The method includes operating a first-stage compressor at a constant speed setting when the first measured value is within a target parameter band, wherein the target parameter band is defined by a first set point and a band offset, adjusting the speed of the first-stage compressor based on proportional rate control when the first measured value is determined to be outside the target parameter band and within a first threshold and a second threshold; and controlling the speed of the second-stage compressor based on proportional band control, wherein controlling the speed of the second-stage compressor based on the proportional band control is based in part on the second measured value and the second set point, the proportional band control further comprising a plurality of proportional bands, each of the plurality of proportional bands comprising a proportional coefficient that is different from any other proportional band in the plurality of proportional bands.

[0008] Another embodiment is a method of controlling a cascade vapor compression system including a first-stage compressor configured to circulate refrigerant in a first-stage refrigeration circuit and a second-stage compressor configured to circulate refrigerant in a second-stage refrigeration circuit, the method comprising: receiving a first measurement value that varies over time, the first measurement value indicating a first parameter associated with the cascade vapor compression system; receiving a second measurement value that varies over time, the second measurement value indicating a second parameter associated with the second-stage refrigeration circuit; controlling the speed of the first-stage compressor based on constant band control, wherein controlling the speed of the first-stage compressor based on constant band control includes, in part, a comparison between the first measurement value and a first set point, the constant band control also including a constant speed setting; and controlling the speed of the second-stage compressor based on proportional band control, wherein controlling the speed of the second-stage compressor based on proportional band control includes: identifying an operating proportional band from a plurality of proportional bands, each of the plurality of proportional bands including a maximum operating speed, a minimum operating speed, and a proportional coefficient, wherein each of the plurality of proportional bands includes a proportional coefficient that is different from any other proportional band in the plurality of proportional bands, and adjusting the speed of the second-stage compressor based on the operating proportional band and the second measurement value.

[0009] Another embodiment is a method of controlling a cascade vapor compression system including a first-stage compressor configured to circulate refrigerant in a first-stage refrigeration circuit and a second-stage compressor configured to circulate refrigerant in a second-stage refrigeration circuit, the method comprising: receiving a first measurement value that varies with time, the first measurement value indicating a measured parameter associated with the cascade vapor compression system; receiving a second measurement value that varies with time, the second measurement value indicating a measured parameter associated with the second-stage refrigeration circuit; and controlling a speed of the first-stage compressor based on constant band control, wherein controlling the first-stage compressor based on constant band control comprises: operating the first-stage compressor at a constant speed setting when determining that the first measurement value is within a target parameter band. A compressor, wherein a target parameter band is defined by a first set point and a band offset, and upon determining that a first measured value is outside the target parameter band and within a first threshold and a second threshold, adjusting the speed of a first stage compressor based on proportional rate control; and controlling the speed of a second stage compressor based on proportional band control, wherein controlling the speed of the second stage compressor based on proportional band control includes: identifying an operating proportional band from a plurality of proportional bands, each of the plurality of proportional bands including a maximum operating speed, a minimum operating speed, and a proportional coefficient, wherein each of the plurality of proportional bands includes a proportional coefficient that is different from any other proportional band in the plurality of proportional bands, and adjusting the speed of the second stage compressor based on the operating proportional band and the second measured value.

[0010] 16. The system of claim 14, wherein the first and second compressors are configured to circulate refrigerant in a first refrigeration circuit; and a controller operatively coupled to the first and second compressors, the controller comprising a processor and a memory, the memory being configured to store computer-readable program code, the program code comprising a control-related software application; the processor being configured to access the memory and execute the computer-readable program code to cause the processor to at least: receive a first measurement value varying with time, the first measurement value indicating a first parameter associated with the cascade vapor compression system; receive a second measurement value varying with time, the second measurement value indicating a second parameter associated with the second refrigeration circuit; and control the first compressor based on a constant band control. The invention relates to a method for controlling the speed of a first-stage compressor, wherein causing the processor to control the speed of the first-stage compressor based on constant band control further comprises causing the processor to: operate the first-stage compressor at a constant speed setting when it is determined that the first measured value is within a target parameter band, wherein the target parameter band is defined by a first set point and a band offset, and when it is determined that the first measured value is outside the target parameter band and within a first threshold and a second threshold, adjust the speed of the first-stage compressor based on proportional rate control; and control the speed of the second-stage compressor based on proportional band control, wherein controlling the speed of the second-stage compressor based on the proportional band control is based in part on the second measured value and the second set point, the proportional band control further comprising a plurality of proportional bands, each of the plurality of proportional bands comprising a proportional coefficient that is different from any other proportional band in the plurality of proportional bands.

[0011] Another embodiment is a cascade vapor compression system comprising: a first-stage compressor configured to circulate refrigerant in a first-stage refrigeration circuit; a second-stage compressor configured to circulate refrigerant in a second-stage refrigeration circuit; and a controller operably coupled to the first-stage compressor and the second-stage compressor, the controller comprising a processor and a memory, the memory configured to store computer-readable program code, the program code comprising a control-related software application; the processor configured to access the memory and execute the computer-readable program code to cause the processor to at least: receive a first measurement value that varies with time, the first measurement value indicating a first parameter associated with the cascade vapor compression system; receive a second measurement value that varies with time, the second measurement value indicating a second parameter associated with the second-stage refrigeration circuit two parameters; controlling the speed of the first stage compressor based on constant band control, wherein controlling the speed of the first stage compressor based on constant band control includes, in part, a comparison between the first measurement value and the first set point, the constant band control also including a constant speed setting; and controlling the speed of the second stage compressor based on proportional band control, wherein controlling the speed of the second stage compressor based on proportional band control includes causing the processor to: identify an operating proportional band from a plurality of proportional bands, each of the plurality of proportional bands including a maximum operating speed, a minimum operating speed, and a proportional coefficient, wherein each of the plurality of proportional bands includes a proportional coefficient different from any other proportional band in the plurality of proportional bands, and adjust the speed of the second stage compressor based on the operating proportional band and the second measurement value.

[0012] Another embodiment is a cascade vapor compression system comprising: a first-stage compressor configured to circulate refrigerant in a first-stage refrigeration circuit; a second-stage compressor configured to circulate refrigerant in a second-stage refrigeration circuit; and a controller operably coupled to the first-stage compressor and the second-stage compressor, the controller comprising a processor and a memory, the memory configured to store computer-readable program code, the program code comprising a control-related software application; the processor configured to access the memory and execute the computer-readable program code to cause the processor to at least: receive a first measurement value that varies with time, the first measurement value indicating a first parameter associated with the cascade vapor compression system; receive a second measurement value that varies with time, the second measurement value indicating a second parameter associated with the second-stage refrigeration circuit; control a speed of the first-stage compressor based on a constant band control, wherein the processor is caused to control the speed of the first-stage compressor based on the constant band control Controlling the speed of the compressor also includes causing the processor to: operate the first-stage compressor at a constant speed setting when it is determined that the first measurement value is within a target parameter band, wherein the target parameter band is defined by a first set point and a band offset, and adjust the speed of the first-stage compressor based on proportional rate control when it is determined that the first measurement value is outside the target parameter band and within a first threshold and a second threshold; and control the speed of the second-stage compressor based on proportional band control, wherein causing the processor to control the speed of the second-stage compressor based on proportional band control includes causing the processor to: identify an operating proportional band from a plurality of proportional bands, each of the plurality of proportional bands including a maximum operating speed, a minimum operating speed, and a proportional coefficient, wherein each of the plurality of proportional bands includes a proportional coefficient different from any other proportional band in the plurality of proportional bands, and adjust the speed of the second-stage compressor based on the operating proportional band and the second measurement value.

[0013] These and other features, aspects, and advantages of the present disclosure will become apparent upon reading the following detailed description and the accompanying drawings, which are briefly described below. The present disclosure includes any combination of two, three, four, or more of the above-described embodiments, examples, or implementations set forth in the present disclosure, as well as any combination of two, three, four, or more features or elements, regardless of whether these features or elements are explicitly combined in the specific embodiment descriptions herein. Unless otherwise expressly provided in the context, the present disclosure is intended to be read as a whole, such that any separable features or elements disclosed in the present disclosure should be considered as intended to be capable of combination in any of its various aspects, embodiments, examples, or implementations. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Having generally described example embodiments of the present disclosure above, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and in which:

[0015] Figure 1 is a perspective view of a cryogenic storage system, according to some example embodiments.

[0016] Figure 2 According to some example embodiments Figure 1 Another perspective view of a cryogenic storage system showing an exterior door opened to view the interior storage chamber therein.

[0017] Figure 3 According to some example embodiments Figure 1 Schematic diagram of the climate control system of the cryogenic storage system.

[0018] Figure 4 is a flow chart illustrating various steps for controlling one or more motors of a climate control system, according to various example embodiments.

[0019] Figure 5A A diagram illustrating an example constant band control process according to some example embodiments;

[0020] Figure 5B shows a flow chart of an example constant band control process according to some example embodiments;

[0021] Figure 6A A diagram illustrating an example proportional band control process according to some example embodiments;

[0022] Figure 6B A flow chart illustrating an example proportional band control process according to some example embodiments; and

[0023] Figure 7 Control circuitry according to some example embodiments is shown. DETAILED DESCRIPTION

[0024] Some embodiments of the present disclosure will be described more fully below with reference to the accompanying drawings, in which some, but not all, embodiments of the present disclosure are shown. Indeed, the various embodiments of the present disclosure may be implemented in many different forms and should not be construed as limited to the embodiments, examples, or implementations illustrated herein; rather, these embodiments, examples, or implementations are provided so that this disclosure will be thorough and complete and will fully convey the scope of the disclosure to those skilled in the art. Like reference numerals refer to like elements throughout.

[0025] Unless otherwise specified or clear from the context, references to first, second, etc. should not be understood to imply a particular order. Furthermore, although reference may be made herein to quantitative measurements, values, geometric relationships, etc., any one or more (if not all) of these may be absolute or approximate, unless otherwise stated, to account for acceptable variations that may occur, such as those due to engineering tolerances, etc.

[0026] As used herein, unless otherwise specified or clear from the context, an "or" of a set of rungs is an "inclusive or," such that it is true if and only if one or more of the rungs is true, as opposed to an "exclusive or," which is false if all of the rungs are true. Thus, for example, "[A] or [B]" is true if [A] is true, or if [B] is true, or if both [A] and [B] are true. Furthermore, the articles "a" and "an" mean "one or more," unless otherwise specified or the context clearly dictates otherwise.

[0027] The disclosure herein describes various control processes that can be used to control the operation of one or more compressors used in a climate control system. These control processes may be particularly applicable to cascade vapor compression systems, which include at least two refrigerant cycles that transfer heat in series. Specifically, it may be advantageous to control one compressor in the cascade vapor compression system using a first control process, such as the constant band control process described herein, and to control another compressor in the cascade vapor compression system using a second control process, such as the proportional band control process described herein.

[0028] To provide more context, cascade vapor compression systems are typically used to transport heat across elevated temperature gradients, such as for ultra-low temperature storage. To achieve these high temperature gradients, the cascade system typically uses a first refrigerant circuit to transport heat between a given temperature, such as the external ambient temperature, and an intermediate temperature. The system then uses a second refrigerant circuit to transport heat between the intermediate temperature and another temperature, typically a desired temperature for regulation. More circuits (and intermediate temperatures) can be used, but the result is that while these circuits can transfer approximately the same amount of heat across a given temperature gradient, they do so under different conditions and considerations.

[0029] For example, the first circuit typically utilizes the outdoor ambient environment as a heat sink / source, and this environment can vary significantly. For example, if the outdoor ambient environment is used, the conditions may vary based on the local weather. In other examples, the system may be located within an indoor space; for example, the freezer may utilize a room (which may or may not be regulated) that serves as the freezer's ambient environment. In these examples, the freezer may utilize the room as the ambient environment for providing a heat source / heat sink for at least one refrigerant circuit. Regardless, in some examples, the first circuit can be used to transfer heat from or to the second circuit via an interstage heat exchanger. In contrast, the second circuit can be designed to regulate a given space or another regulatory requirement, such as regulating a heat transfer fluid, and can be driven based on the resulting varying regulatory requirements. However, current control systems for cascade systems typically do not account for these various considerations and typically control each of the various circuits based on the same or similar processes. This often results in suboptimal performance of one or both refrigeration circuits, as well as suboptimal performance of the entire system.

[0030] The present disclosure addresses this issue while also providing an overall improved control process. For example, the disclosed process includes utilizing a separate control process for each of these refrigeration circuits. Each of these processes addresses the issues present in its respective circuit and generally provides improved control over current control processes.

[0031] To introduce a further example, the disclosed process includes operating a first compressor in a first refrigerant circuit based on a constant band control process. In this example, the first compressor is driven to achieve a constant temperature of the interstage heat exchanger. This may be suitable for enabling the overall system to utilize this heat exchanger as a constant heat source / sink for the second stage circuit. Thus, the control process can be designed to determine an appropriate operating level for the first stage compressor and then, once that operating level is determined (or otherwise set), operate the compressor at that operating level whenever possible.

[0032] In this example, the first-stage refrigerant circuit may include a setpoint for the interstage heat exchanger, and it may also include a target parameter band associated with the setpoint. The setpoint may be a desired temperature of the interstage heat exchanger during operation, and the target parameter band may be a temperature range considered suitable or acceptable near the setpoint. The process may also include monitoring the temperature of the interstage heat exchanger and adjusting the operation of the compressor based on the difference between the monitored temperature and the setpoint.

[0033] The constant band control may also include a process for determining an appropriate operating level for the compressor, such as determining a constant control setting. Here, the compressor may determine this setting based on when the system is first turned on, perhaps after installation. This may be beneficial because, after installation, the system (and its various components) may be configured according to their manufacturing configuration, and thus this initial operation may indicate preferred or standard operation of the system. Regardless, once the system is turned on, it may operate at a maximum operating level, bringing the measured temperature closer to the desired set point. For example, at this point, the measured temperature may be above the high proportional band limit of the constant band control process, which may cause the process to operate at its maximum operating level. As the temperature measurement begins to approach the set point, the measured temperature may drop below the high proportional band limit. In this case, the constant band control process may adjust the compressor operating level based on proportional rate control. As the temperature measurement continues to approach the set point, typically decreasing, the constant band control process may continue to reduce the compressor operating level based on proportional rate control. Once the temperature measurement reaches within the target parameter band, the constant band control process may begin recording the operating level value. During this period, the constant band control process may continue to adjust the compressor operating level based on proportional rate control. Once the temperature measurement leaves the target temperature band, the constant band control process can determine a constant control setting. The constant control setting can be an average of the operating levels recorded when the measured temperature was within the target temperature band.

[0034] Once the constant control setting is determined, the constant band control process controls the compressor to the constant control setting when the measured temperature is within the target temperature band. As a result, constant band control will be able to continue to operate the compressor at a level determined to be appropriate under known conditions. In addition, after determining the constant control setting, the constant band control process can continue to utilize the other controls discussed above. For example, if the measured temperature is above the high proportional band limit, the constant band control process can control the compressor to the maximum operating level. If the measured temperature is below the low proportional band limit, the constant band control process can control the compressor to the minimum operating level. If the measured temperature is between the high proportional band limit and the low proportional band limit, but outside the target temperature band, the constant band control process can control the compressor based on proportional rate control. Again, if the measured temperature is within the constant band, the constant band control process can control the compressor to the constant control setting. This constant band control process is described in more detail below and includes additional and / or alternative features.

[0035] Turning to another control process, the disclosed system can also utilize a proportional band control process. This process can be used in a secondary refrigeration loop in a climate control system, in part because it allows for more continuous adjustments as a measured parameter approaches a given set point. The proportional band control process includes multiple different proportional bands, and the process switches between these bands to achieve the desired control process via the proportional bands.

[0036] Each proportional band can include a maximum operating level, a minimum operating level, and a proportional coefficient. Each proportional band can include different values. For example, multiple proportional bands can be arranged so that the maximum operating band continues to decrease, and with each decrease, the proportional coefficient also decreases. For example, a first proportional band can be set so that the maximum operating level is the compressor's maximum rated operating level, e.g., 100%, and the minimum operating level is set to the compressor's minimum rated operating level, e.g., 30%. The proportional coefficient for this first proportional band can be based on the difference between these maximum and minimum operating levels. The next proportional band can maintain the same minimum operating level, e.g., 30%, and reduce the maximum operating level by 5%. For example, the maximum operating level for the second proportional band can be 95%. In this example, the proportional coefficient for this second proportional band also decreases based on the lower maximum operating level. This process continues, so that each successive proportional band includes the same minimum operating level, e.g., 30%, but a lower maximum operating level, e.g., 90%, 85%, and so on, with a correspondingly lower proportional coefficient. Thus, the proportional coefficient continues to narrow within the operating range, and the proportional coefficient continues to decrease. This may allow the proportional band to provide progressively less responsive adjustments to compressor operation as the process adjusts to focus on the preferred desired operating range.

[0037] Furthermore, the proportional band control process can switch between these proportional bands to determine the responsiveness of the regulation process. For example, the proportional band control process can switch between a higher-level operating band (e.g., a band with a higher maximum operating level) and a lower-level operating band (e.g., a band with a lower maximum operating level). This switching can be initiated based on whether a given proportional band can achieve a desired set point and whether a measured parameter is at or below the desired set point over a certain period of time. For example, if a measured parameter is below the desired set point for a given period of time, the proportional band control process can switch to a lower operating band, such as one with a lower maximum operating level. This switching process can continue as long as the measured temperature remains at or below the desired temperature. However, if the measured parameter is above the desired set point and the proportional band cannot adjust the measured parameter to or below the desired set point, the proportional band control process can switch to a higher operating band, such as one with a higher maximum operating level. This switching process can continue as long as the proportional band cannot meet the given temperature set point. This proportional band control process will be described in more detail below, including additional and / or alternative features. Furthermore, as can be understood from the description provided herein, these control processes can be used with cascade vapor compression systems, simple cycle climate control processes, and even different field control processes.

[0038] Turning to the figures, an example cascade vapor compression system and examples of each of the control processes that the system may utilize will be discussed in greater detail below.

[0039] Now refer to Figure 1 and Figure 2 , shows a cryogenic storage system 10 according to some embodiments. The cryogenic storage system 10 can be configured to store degradable products (such as life science products and materials) at a temperature below the freezing point of water (e.g., 0°C or 32°F) or lower (e.g., below -20°C, below -40°C, below -70°C, below -80°C, etc.). Therefore, the cryogenic storage system 10 may be more simply referred to as a "freezer" herein. In some embodiments, the freezer can be configured to store products at ultra-low temperatures below -50°C. However, it should be understood that other embodiments of the cryogenic storage system 10 can be configured to store products at temperatures above the freezing point of water.

[0040] Generally speaking, the cryogenic storage system 10 includes a housing 15 that defines one or more internal storage chambers 12 (or more simply "chambers" or "chambers"). Figure 2In the embodiment shown, the housing 15 includes a separate chamber 12 accessible via an outer door 14. Specifically, the chamber 12 may include a front opening 13 that is closable by the outer door 14 during operation. Thus, the chamber 12 is at least partially defined by the outer door 14. When the door 14 is closed, thereby blocking or covering the front opening 13 ( Figure 1 ), the chamber 12 is isolated from the surrounding environment 5 or is substantially closed, when the door 14 is opened ( Figure 2 ), the chamber 12 is exposed to the surrounding environment 5 via the front opening 13. In some embodiments, the cryogenic storage system 10 can define a plurality of separate chambers 12, which can be accessed via an outer door 14 or multiple outer doors 14.

[0041] like Figure 2 As shown, the chamber 12 can have one or more (e.g., a plurality) inner doors 17 positioned therein that are configured to at least partially close the front opening 13 independently of the outer door 14. The one or more inner doors 17 can provide an additional barrier (i.e., in addition to the outer door 14) to minimize air exchange between the chamber 12 and the surrounding environment 5 when the outer door 14 is open. The number and arrangement of the inner doors 17 can correspond to the shelves or other tissue support structures inserted into the chamber 12 so that a user can open the inner door 17 associated with a specific storage location (e.g., a specific shelf).

[0042] In addition, the cryogenic storage system 10 includes a climate control system 100 operably coupled to the chamber 12. Specifically, the chamber 12 can be conditioned by a separate climate control system 100 configured to achieve and / or maintain a desired temperature (or temperature range) within the chamber 12 during operation. The climate control system 100 can include a vapor compression refrigeration system or module (or more simply, a "refrigeration module") that circulates one or more refrigerants to exchange heat between the chamber 12 and the environment 5 during operation. In some embodiments, the climate control system 100 can include a cascade refrigeration module having multiple staged refrigerant circuits that are in thermal communication with each other and configured to achieve and / or maintain a low temperature within the chamber 12 during operation.

[0043] Housing 15 may define or include a first portion or upper portion 18 and a second portion or lower portion 16, with second portion or lower portion 16 positioned vertically below and lower than upper portion 18. Climate control system 100 may generally define upper portion 18, and chamber 12 may generally define lower portion 16. Thus, climate control system 100 (or at least a majority thereof) may be positioned vertically above, or even vertically above, chamber 12. According to some embodiments, additional features of chamber 12 and climate control system 100 are provided herein.

[0044] Furthermore, in some embodiments, the location of the climate control system 100 relative to the chamber 12 and the lower portion 16 of the housing 15 can vary. For example, in some embodiments, the climate control system 100 (or a portion thereof) can be positioned along a lateral side or back of the lower portion 16 of the housing 15, or possibly even along the bottom side of the lower portion 16 of the housing 15.

[0045] The freezer 10 can operate using electricity supplied from a line power source (e.g., a local power grid). In addition, the freezer 10 can include (or be coupled to) one or more backup batteries, capacitors, generators, and the like (collectively, "backup power sources," not shown) to ensure that the freezer 10 (or one or more components or subsystems thereof) remains operational in the event of a line power failure. In some embodiments, the one or more backup power sources can operate one or more sensors (e.g., temperature sensor 128) and a user interface (e.g., user interface 300 described herein) of the freezer 10, but the remainder of the freezer 10 may become inoperable in the event of a line power failure or malfunction.

[0046] Figure 3 A schematic diagram of a climate control system 100 for a freezer 10 according to some embodiments is shown. In some embodiments, the climate control system 100 is a refrigeration system that is configured to circulate a refrigerant (or multiple refrigerants) to cool the chamber 12 during operation. Specifically, the climate control system 100 can include a so-called cascade refrigeration system that includes a plurality of separate staged refrigerant circuits 113, 121 that are thermally coupled to each other for transferring heat between the chamber 12 and the ambient environment 5. In some embodiments, the climate control system 100 can be configured to achieve and / or maintain low temperatures (e.g., "ultra-low" temperatures) in the chamber 12. Accordingly, the climate control system 100 may be referred to herein as a "cascade vapor compression system," a "cascade refrigeration system," or more simply a "refrigeration system." As described herein, other climate control systems, such as single-stage climate control systems, can also utilize the features disclosed herein.

[0047] like Figure 3As shown in FIG, the climate control system 100 may include a first refrigeration stage 102 (or more simply, "first stage" 102) having a first refrigerant circuit 113 that circulates a first refrigerant and a second refrigeration stage 104 (or more simply, "second stage" 104) having a second refrigerant circuit 121 that circulates a second refrigerant. The first refrigerant and the second refrigerant may include any suitable refrigerant or combination of refrigerants, such as one or more chlorofluorocarbons, hydrochlorofluorocarbons, hydrocarbons, ammonia, etc. The first refrigerant and the second refrigerant may be different from each other, and in particular, may have different phase change temperatures. The first refrigerant and the second refrigerant can be selected so that under the operating pressure of the first refrigerant circuit 113 and the second refrigerant circuit 121, the saturated condensing temperature range of the second refrigerant (in the second refrigerant circuit 121) overlaps with the saturated evaporation temperature of the first refrigerant (in the first refrigerant circuit 113) in the interstage heat exchanger (e.g., the interstage heat exchanger 114 described herein), so that each of the first refrigerant and the second refrigerant may experience a change in enthalpy when thermally interacting with each other during operation (e.g., via the interstage heat exchanger 114 described herein).

[0048] Generally speaking, during operation, the climate control system 100 can circulate the first refrigerant and the second refrigerant through the first refrigerant circuit 113 and the second refrigerant circuit 121, respectively, to transfer heat from the chamber 12 to the ambient environment 5. Heat can be transferred between the first refrigerant and the second refrigerant via the interstage heat exchanger 114, which is coupled to and part of each of the first refrigerant circuit 113 and the second refrigerant circuit 121.

[0049] More specifically, the first refrigerant circuit 113 can circulate the first refrigerant between the first stage compressor 112 (or more simply referred to as "compressor" 112), the condenser 110, the first stage expansion valve 116 (or more simply referred to as "expansion valve" or "valve" 116), and the interstage heat exchanger 114 to transfer heat from the second refrigerant circuit 121 (described in more detail herein) to the ambient environment 5. Specifically, the compressor 112 can compress the first refrigerant and output the compressed first refrigerant to the condenser 110. Due to the heat exchange within the interstage heat exchanger 114, the first refrigerant flowing to and through the compressor 112 may be in (or substantially in) a vapor state. The condenser 110 may include a heat exchanger (or a collection of heat exchangers) configured to cool the first refrigerant by transferring heat from the first refrigerant to the ambient environment 5 by, for example, convection, radiation, and / or any other suitable heat transfer mode. For example, in Figure 3In the embodiment shown in FIG, a blower or fan 118 can generate an airflow 117 that is in thermal contact with the first refrigerant via the condenser 110, such that during operation, the first refrigerant transfers heat to the airflow 117 and cools, thereby condensing or partially condensing the vapor into a liquid. The heated airflow 117 can flow outward and away from the condenser 110 and into the ambient environment 5. In some embodiments, the condenser 110 can transfer heat from the first refrigerant to the ambient environment 5 via natural convection and / or radiation, in addition to or in lieu of forced convection via the airflow 117. Therefore, in some embodiments, the fan 118 can be omitted.

[0050] Liquid (or at least partially liquid) first refrigerant may be discharged from condenser 110 and then expanded through expansion valve 116 to at least partially evaporate and further cool the first refrigerant. Thereafter, the cooled first refrigerant flows into interstage heat exchanger 114.

[0051] Within the interstage heat exchanger 114, heat is transferred from the second refrigerant flowing through the second refrigerant circuit 121 to the first refrigerant, causing the first refrigerant to undergo a phase change (or a substantial phase change) from liquid to vapor within the interstage heat exchanger 114. Thus, the interstage heat exchanger 114 can function as an evaporator for the first refrigerant in the first refrigerant circuit 113. The heated and evaporated (or partially evaporated) first refrigerant is then discharged from the interstage heat exchanger 114 and flows back to the first-stage compressor 112 to restart the aforementioned cycle.

[0052] Still refer to Figure 3 The second refrigerant circuit 121 can circulate the second refrigerant between the second-stage compressor 120 (or more simply referred to as "compressor" 120), the interstage heat exchanger 114, the second-stage expansion valve 122 (or more simply referred to as "expansion valve" or "valve" 122), and the evaporator 124 to transfer heat from the chamber 12 to the first refrigerant circuit 113. Specifically, the compressor 120 can compress the second refrigerant and output the compressed second refrigerant to the interstage heat exchanger 114. Due to the heat exchange within the evaporator 124, the second refrigerant flowing to the compressor 120 and through the compressor 112 may be in (or substantially in) a vapor state. Within the interstage heat exchanger 114, heat can be transferred from the second refrigerant to the first refrigerant as described above. As a result, within the interstage heat exchanger 114, the second refrigerant can be cooled, condensing or partially condensing from a vapor to a liquid. Therefore, the interstage heat exchanger 114 can serve as a condenser for the second refrigerant in the first refrigerant circuit 121.

[0053] Liquid (or at least partially liquid) second refrigerant may be discharged from interstage heat exchanger 114 and then expanded through expansion valve 122 to at least partially evaporate and further cool the second refrigerant. Thereafter, the cooled second refrigerant flows into evaporator 124.

[0054] The evaporator 124 is a heat exchanger configured to transfer heat from the chamber 12 to the second refrigerant. Specifically, the cooled second refrigerant flows through the coils 126, which are thermally exposed to the airflow 50 in the evaporator 124, causing heat to be transferred from the airflow 50 to the second refrigerant, thereby causing the second refrigerant to undergo a phase change (or substantially phase change) from a liquid to a vapor. The airflow 50 can be generated by a blower or fan 36 positioned along the ductwork 30, which is configured to direct airflow between the chamber 12 and the evaporator 124 during operation. Specifically, the ductwork 30 includes a suction duct 32 configured to direct the airflow 50 from the chamber 12 to the evaporator 124, and a discharge duct 34 configured to direct the airflow 50 from the evaporator 124 to the chamber 12. The blower 36 may be located along or adjacent to the discharge duct 34 ; however, other locations for the blower 36 (eg, in the intake duct, in the chamber 12 , etc.) are also contemplated herein.

[0055] In some examples, the blower 36 and the associated one or more pipes may not be required. In these examples, the climate control system 100 can be coupled to a heat transfer fluid for delivering heat energy to the evaporator. For example, the freezer can be a cold wall freezer that uses ethylene glycol (or another fluid) to circulate heat from the cold wall (or plate) to the evaporator 124. In these systems, the fluid receives heat at a given location (e.g., a wall, plate, etc.), which typically increases the temperature of the heat transfer fluid. The heat transfer fluid then flows back to the evaporator 124, where it receives heat, which typically lowers the temperature of the heat transfer fluid. The heat transfer fluid then returns to the given location at this lower temperature, and the cycle repeats. In these examples, a pump is typically used to circulate the fluid to deliver heat, rather than a fan. Similarly, the freezer can also use water (or another fluid) to deliver heat to the evaporator 124 in a similar manner. It is further understood that in examples where the system operates as a heat pump, the heat transfer will be in reverse flow, and the heat exchanger will be a condenser. Similarly, other configurations can be utilized.

[0056] Still refer to Figure 3During operation, the climate control system 100 can significantly reduce the temperature in the chamber 12. As previously described, in some embodiments, the climate control system 100 can be configured to achieve and / or maintain ultra-low temperature and humidity levels in the chamber 12, while the ambient environment 5 remains at normal indoor conditions (e.g., a temperature in the range of approximately 18-24°C (approximately 65-75°F) and a relative humidity level in the range of approximately 30-60%). In some embodiments, the ambient environment 5 can include a temperature that is lower than normal indoor conditions (e.g., lower than 18°C ​​or 65°F), but may still be warmer than the temperature in the chamber 12. Air at a higher temperature than the chamber 12 may also include a greater relative humidity value than that in the chamber 12. Thus, when the exterior door 14 is opened, relatively warm and humid air from the ambient environment 5 may flow into the generally cooler chamber 12 and ultimately form ice therein. Of particular note, the airflow 50 circulating between the evaporator 124 and the chamber 12 may cause ice to form on the coils 126 of the evaporator 124, which may reduce the heat transfer function of the evaporator 124. Therefore, the climate control system 100 may periodically perform a defrost operation to remove ice accumulated on the coils 126. The defrost operation may include a so-called "hot gas bypass" and / or a separate supplemental heat source.

[0057] The controller 40 may be communicatively coupled (via any suitable wired and / or wireless connection) to various components of the climate control system 100 (e.g., compressors 112, 120, condenser 110, expansion valves 116, 122, valve 127, etc.). As described in more detail herein, the controller 40 may at least partially direct or control the operation of the climate control system 100 during operation. The controller 40 may be (or may be incorporated into) the primary or master controller for the chiller 10, or the controller 40 may be a stand-alone controller 40 used to control the climate control system 100 or a portion thereof. Regardless, the controller 40 may be described and referred to herein as being part of the refrigeration module 100, and more generally, the chiller 10 ( Figure 1 and Figure 2 ) part.

[0058] The controller 40 may include one or more computing devices, such as a computer, tablet computer, smartphone, server, circuit board, or other one or more computing devices or one or more systems.

[0059] The processor 42 may include any suitable processing device or a collection of processing devices. In some embodiments, the processor 42 may include a microcontroller, a central processing unit (CPU), a graphics processing unit (GPU), a timing controller (TCON), a scaler unit, or some combination thereof. During operation, the processor 42 executes machine-readable instructions (such as machine-readable instructions 46) stored on the memory 44, thereby causing the processor 42 to perform some or all of the actions attributed to the controller 40 herein. Typically, the processor 42 acquires, decodes, and executes instructions (e.g., machine-readable instructions 46). In addition, the processor 42 may also perform other actions, such as making determinations, detecting states or values, and transmitting signals. If the processor 42 assists another component in performing a function, it can be said that the processor 42 causes the component to perform the function.

[0060] The memory 44 may be any suitable device or collection of devices for storing digital information, including data and machine-readable instructions, such as the machine-readable instructions 46. For example, the memory 44 may include volatile storage, such as random access memory (RAM), non-volatile storage, such as flash memory, read-only memory (ROM), etc., or a combination of volatile and non-volatile storage. Data read or written by the processor 42 when executing the machine-readable instructions 46 may also be stored on the memory 44. The memory 44 may include a "non-transitory machine-readable medium," where the term "non-transitory" does not include or encompass transient propagating signals.

[0061] Processor 42 may include one processing device or multiple processing devices distributed within controller 40 (or communicatively coupled to controller 40) or more broadly distributed within climate control system 100 and / or freezer 10 ( Figure 1-3 Likewise, memory 44 may include one memory device or multiple memory devices distributed within (or communicatively coupled to) controller 40 or more broadly distributed within climate control system 100 and / or freezer 10 ( Figure 1-3 ). Thus, the controller 40 may include components distributed throughout the climate control module 100 and / or the freezer 10 ( Figure 1 ) in a separate "controller".

[0062] The controller 40 may be communicatively coupled (eg, via a wired connection and / or a wireless connection) to one or more components of the climate control system 100. For example, Figure 3As shown in FIG, the controller 40 can be communicatively coupled to the compressors 112 and 120, the valves 116, 122, and 127, the blowers 118 and 36, or some subset thereof. During operation, the controller 40 can control the operating states of the components of the climate control module 100. For example, the controller 40 can change the operating state of one or both of the compressors 112, 120 and / or the blowers 118, 36, such as by activating, deactivating, and / or changing the operating speed of one or both of the compressors 112, 120 and / or the blowers 118, 36 during operation. It should be understood that this control can include, in whole or in part, controlling one or more motors associated with the compressors and / or the blowers during operation. Similarly, the controller 40 can change the operating state of one or more of the valves 116, 122, 127, such as by changing their position (e.g., open, closed, or somewhere in between). In some embodiments, controller 40 may vary the operating state of one or both of compressors 112 , 120 and / or one or more of valves 116 , 122 , 127 to achieve or maintain a desired temperature in chamber 12 .

[0063] The controller 40 may also be coupled to one or more sensors 128. This may include sensors related to the condition of the chamber 12, the airflow 50, the interstage heat exchanger 114, the condenser 110, the evaporator 124, and / or other components. These sensors may monitor any parameter. For example, the sensor 128 may be a temperature sensor that monitors the temperature of a given component or the flow of fluid. In other examples, the sensor 128 may be a pressure sensor that monitors a corresponding pressure. Other sensors and sensor locations may also be used in accordance with the features described herein.

[0064] exist Figure 3In the example shown in FIG, the climate control system includes four different sensors 128 (A, B, C, and D). In this example, sensor 128A may be located on the interstage heat exchanger 114. In some examples, 128A is a temperature sensor and is positioned to monitor the refrigerants in both refrigerant circuits (113 and 121). This configuration allows sensor 128A to monitor heat transfer between the two refrigerant flows, as well as potentially other characteristics such as phase change, saturation temperature, etc. In some examples, the positioning of the sensors allows the sensors to determine whether one or both refrigerant fluids have undergone a complete or substantially complete phase change. For example, when the refrigerant in the second circuit 121 is circulating, the state associated with the refrigerant in the first circuit 113 may be very different from the state when the refrigerant in the second circuit 121 is not circulating. Therefore, sensor 128A can be used to monitor the thermal performance of the interstage heat exchanger, which is affected by both circuits. This design can allow sensor 128A to monitor an equilibrium state, where heat is transferred between the two circuits at a constant or substantially constant rate. Some cascade systems are designed so that this equilibrium state occurs at certain phase change temperatures in each circuit to provide a high level of performance.

[0065] Similarly, sensor 128B can be located in chamber 12, and in some examples, the sensor can be a temperature sensor. In some examples, sensor 128B is positioned in a manner that provides consistent temperature readings for the entire chamber (or its sub-compartments). For example, sensor 128B can be located away from a door or seal, or in another location that is not subject to frequent temperature changes.

[0066] Similarly, sensor 128C can be located in the suction duct 32. The sensor can be a temperature sensor, and it can provide a consistent temperature associated with the chamber. For example, monitoring the air in the suction duct can gather the load associated with the chamber to provide a representative temperature of the chamber as a whole. In some examples, a sensor (not shown) is provided in the discharge duct 34 to provide a consistent temperature associated with the air provided to the chamber. In examples where there are sensors in both the discharge duct and the suction duct, differential parameters can be monitored. For example, a temperature difference can be determined, which in some examples can be used as part of the load calculation. A pressure difference (or other parameter) can also be determined. It should be understood that in systems that do not involve forced air, such as systems using different heat transfer fluids, such as some cold wall systems, freezers, etc., the sensor 128C shown (and similar sensors) can monitor parameters associated with these fluids.

[0067] In the example shown, sensor 128D is located at condenser 110 in first stage 102. In some examples, this sensor may also be a temperature sensor and may be used to monitor conditions related to heat source / sink for the entire system. In some examples, this sensor is used to monitor the state of the refrigerant in first loop 113, perhaps to determine saturation temperature, phase changes associated with refrigerant passing through the condenser, or for other purposes.

[0068] In the example shown, sensor 128E is located at the evaporator 110 in the second stage 104. In some examples, this sensor may also be a temperature sensor and may be used to monitor the state of a regulating heat exchanger associated with the system. In some examples, this sensor is used to monitor the state of the refrigerant in the first loop 113, perhaps to determine saturation temperature, phase changes associated with the refrigerant passing through the condenser, or for other purposes. Furthermore, for each of these sensors 128, it will be understood that the sensor can be used to monitor different parameters. For example, for several of the sensors discussed herein, a pressure sensor can be used to provide similar indications of how the system is functioning, and in some examples, these pressure measurements can be used to provide an approximation of temperature measurements, and vice versa.

[0069] The controller 40 can be communicatively coupled to various sensors 128 and can be configured to control the operating state of the climate control system 100 (or its components) during operation based at least in part on the outputs of the sensors 128. For example, the controller 40 can adjust the operation of the first compressor 112 and / or the second compressor 120 or their motors based on the outputs of one or more sensors 128. Specifically, the controller 40 can activate or adjust the operation of the compressors 112, 120 and the blowers 36, 118 to circulate the first and second refrigerants through the first and second refrigerant circuits 113, 121, respectively, at least in part in response to the outputs of the sensors 128 (which indicate a sensed state compared to a target value), as previously described. Conversely, the controller 40 can deactivate the compressors 112, 120 to stop the circulation of the first and second refrigerants through the first and second refrigerant circuits 113, 121, respectively, at least in part in response to the outputs of the temperature sensors 128 (which indicate a temperature in the suction line 32 is below a target value), as previously described. Furthermore, controller 40 may adjust the positions of valves 116 , 122 and / or the operating speeds of compressors 112 , 120 and / or blowers 36 , 118 to actively vary the cooling capacity of climate control system 100 based at least in part on the output of temperature sensor 128 .

[0070] Returning to the disclosed control process or processes, Figure 4-6 provides an overview of one or more example processes that can be used according to the present disclosure. In some examples, these processes are combined with the above Figure 1-3 The climate control systems discussed implement, for example, freezer 10. In these examples, controllers, processes, computer-readable media, etc., can utilize the various inputs discussed in these processes to control the various components in the manner described herein.

[0071] Figure 4 An overview of a process 400 is provided that can be used to control two separate compressors, possibly compressors of a cascade vapor compression system, using two separate control processes. In this example, the first control process is a constant band control process and the second control process is a proportional band control process. Figure 5A and 5B A more detailed description of an example constant band control process 500 that can be used alone or in conjunction with process 400 is provided. Figure 6A and 6B A more detailed description of an example proportional band control process 600 that may be used alone or in conjunction with process 400 is provided.

[0072] Go to Figure 4 The process 400 in the illustrated example may be applicable to a cascade vapor compression system. For example, the cascade vapor compression system may include a first-stage compressor that circulates a first refrigerant in a first-stage refrigerant circuit. It may also include a second-stage compressor that circulates a second refrigerant in a second-stage refrigerant circuit. This may be combined with the above Figure 1-3 The processes discussed are the same or similar. In these examples, it may be advantageous to control the first stage compressor and the second stage compressor differently. Thus, the illustrated example involves receiving two different measured parameters and using these measured parameters to control two different compressors associated with a cascade vapor compression system. Again, in this example, different control processes are used to control each of these compressors.

[0073] To provide an overview, process 400 includes receiving a first measured parameter as shown in step 402 and a second measured parameter as shown in step 404. Process 400 may also control a first stage compressor based on a constant band control process and the first measured parameter as shown in step 406. It may also include controlling a second stage compressor based on a proportional band control process and the second measured parameter as shown in step 408.

[0074] Receiving the first measured parameter at step 402 may be performed in a variety of ways. For example, the measured parameter may be a temperature measurement associated with an interstage heat exchanger in a cascade vapor compression system, or may be a different measured parameter. These measured parameters may be received via sensors and may be received over time, typically on a continuous or regular basis. In some examples, the first measured parameter may be received via sensors in conjunction with the above. Figure 3 The sensor or sensors in question receive a first temperature measurement.

[0075] Process 400 may also include receiving a second measured parameter, as shown in step 404. The second measured parameter may be a temperature measurement associated with the chamber conditioned by the cascade vapor compression system, or may be a different measured parameter. Similar to step 402, the second measured parameter may be received via a sensor and may be received over time, typically on a continuous or regular basis. In some examples, the second measured parameter may be received via the sensor in conjunction with the above. Figure 3 The sensor or sensors in question receive a second temperature measurement.

[0076] Process 400 also includes controlling the first compressor based on constant band control, as shown in step 406. This control step may utilize the measurements received at step 402 as part of the control process, such as the first measured parameter. Controlling the compressor via constant band control may include setting, adjusting, and operating the compressor at various operating levels via the compressor motor or other means, as will be discussed below. Figure 5A and 5B for a more detailed discussion.

[0077] Process 400 also includes controlling the second compressor based on proportional band control, as shown in step 408. This control step may utilize the measurement value received at step 404 as part of the control process, such as a second measured parameter. Controlling the second compressor via proportional band control may include setting, adjusting, and operating the compressor at various operating levels via the compressor motor or other means, as will be discussed below. Figure 6A and 6B for a more detailed discussion.

[0078] Figure 5A and 5B An example diagram and process flow associated with a constant band control process (500) is shown. Figure 5A shows a schematic diagram for an example constant band control process 500, Figure 5BA process flow for an example constant band control process is shown. Both figures are used to illustrate the example process. In this discussion, the constant band control process 500 is discussed in conjunction with the first stage (102) of the cascade vapor compression system; however, it should be understood that the control process can be used with the second stage (104) of the cascade vapor compression system or any other process, such as a standard refrigerant process, etc.

[0079] exist Figure 5A , a diagram illustrating a constant band control process 500 for mapping compressor operation to parameters associated with a refrigerant circuit. In this example, compressor operation is the operating level shown on the y-axis 502. The constant band control process 500 maps this operating level to the parameter shown on the x-axis 504. Additionally, a parameter setpoint 506 is shown, which may be a temperature setpoint for a given component. In this example, the constant band control process 500 adjusts the compressor operating level based on the measured parameter to achieve or approach a desired setpoint. This diagram will be described in more detail below.

[0080] Figure 5A , the compressor operating level. The y-axis 502 in FIG. 5 represents the compressor operating level, which may be the operating speed of the compressor, or may be other parameters, such as power level, capacity level, etc. Here, the compressor operating level may be a percentage from 0% to 100%. A 100% operating level may indicate a rated maximum operating level for a motor associated with the compressor. In some examples, the maximum operating level may be set differently, which may be based on calibration of the compressor and compressor motor during manufacturing or testing, during installation, or through different processes. It is further understood that other indicators related to compressor operation may be used, such as an actual compressor speed value, such as a revolutions per minute (RPM) value, or other metrics related to the operating level rate associated with compressor operation.

[0081] Figure 5A The x-axis 504 in FIG. 5 represents a measured parameter. In some examples, the measured parameter is a measured temperature and / or pressure. For a first-stage compressor in a cascade vapor compression system, the measured parameter may be the measured temperature of an interstage heat exchanger. In the illustrated example, the measured parameter values ​​increase along the x-axis. Similarly, the measured parameter may be another measured temperature, pressure, or other parameter used to control the compressor in the manner discussed herein, such as via a compressor motor.

[0082] Figure 5AThe setpoint 506 in FIG. 5 is a target value. In some examples, the setpoint may be a desired value for a given measured parameter. For example, the setpoint value may be a desired temperature for an interstage heat exchanger during operation. In some examples, the setpoint value may be determined to maximize the operating efficiency of the first-stage refrigerant cycle in a cascade system. For example, it may be based on the refrigerants and various components used in the first and second stages. For example, the setpoint may be determined to ensure complete or near-complete phase change of the first and / or second refrigerants. For example, the setpoint 506 may be an interstage temperature setpoint, and this temperature setpoint may be selected to optimize thermodynamic heat transfer between the first and second refrigerant cycles. In some examples, the setpoint may be determined by testing, calibrating, or continuously operating the climate control system using this process. In some examples, the temperature setpoint may be adjusted by the system manufacturer, system operator, technician, etc. Other parameters and setpoints may be used, and it will be appreciated that if the control process is used in a different application, such as a non-cascade system, other considerations may be used when selecting the operating setpoint.

[0083] The constant band control process 500 may also include various different controls. In the example shown, the constant band control process 500 includes a high proportional band limit 510, a low proportional band limit 512, a constant control setting 514, a target parameter band range 516, and a proportional rate control 518. Furthermore, the high proportional band limit 510 corresponds to a high operating limit 520, such as a maximum operating limit, and the low proportional band limit 512 corresponds to a low operating limit 522, such as a minimum operating limit. Each of these controls can be used to adjust the compressor operating level 502 to achieve a desired set point 506. In this example, the constant band control process 500 utilizes the appropriate control based on a measured parameter (which may be compared to a set point).

[0084] To introduce these controls, a high proportional band limit 510 may be a measured value above the set point 506. In some examples, the high proportional band limit may be referred to as a threshold, perhaps a first threshold. This value may be selected to correlate with operating the compressor at a high level, perhaps at a maximum operating level. In the example shown, the high proportional band limit is a parameter setpoint above the set point 506, and the operating level at the high proportional band limit, such as the high operating limit 520, is the maximum operating speed of the compressor. In this example, if the measured parameter is at or above the high proportional band limit 510, the constant band control process 500 may operate the compressor at the maximum operating level, such as the maximum operating speed.

[0085] The low proportional band limit 512 can be a set value or measured value that is lower than the set point 506. In some examples, the low proportional band limit can be referred to as a threshold value, possibly a second threshold value. The value can be selected to be a value associated with operating the compressor at a low level, possibly at a minimum operating level. In the example shown, the low proportional band limit is a parameter set value that is lower than the set point 506, and the operating level at the low proportional band limit, such as the low operating limit 522, is the minimum operating level for the compressor. In some examples, if the measured parameter is at or below the low proportional band limit 512, the constant band control process 500 can operate the compressor at a minimum operating level, such as a minimum operating speed. In another example, not shown, if the measured parameter is below or significantly below the low proportional band limit 512, the operating level may drop or jump to zero or an off state.

[0086] In some examples, the high proportional band limit 510 and the low proportional band limit 512 are selected based on the set point value and the proportional band offset. In these examples, the high proportional band limit 510 can be a value higher than the set point 506 by the proportional band offset, and the low proportional band limit can be a value lower than the set point 506 by the proportional band offset. For example, if the set point is -23°C and the proportional band offset is 5°C, the high proportional band limit can be -18°C and the low proportional band limit can be -28°C. Other processes can be used to determine the high proportional band limit and the low proportional band limit.

[0087] In some examples, if the measured temperature is between the upper proportional band limit and the lower proportional band limit, the constant band control process 500 uses another control process. Also in these examples, the constant band control process adjusts compressor operation in response to the measured parameter to drive the parameter to (or approximately to) the set point.

[0088] In this example, the constant band control process 500 attempts to drive compressor operation to a constant control setting 514. At this setting, the constant band control process operates the compressor at the constant setting, provided the measured parameter is within an appropriate range of the set point 506. For example, the constant band control process 500 may define a constant band range 516 associated with the set point 506. This range 516 may be defined based on the value of a band offset and may be used to define a range of acceptable measured parameters near the set point value. For example, the set point value may be -23°C and the constant band offset value may be 1°C. In these examples, when the measured parameter is within the target parameter band range 516, the constant band control process 500 may control the compressor to operate at the constant control setting 514. For example, the constant control setting 514 may be a constant speed setting. When the measured parameter is within the target parameter band range, the constant band control process 500 may operate the compressor at the constant speed setting. In this example, the target parameter band is between -22°C and -24°C.

[0089] In some examples, the target parameter band range 516 may also be used to determine the constant control setting 514. This set operating level may be established in various ways. For example, as discussed in more detail below, the constant band operating level may be determined based on operating the compressor and evaluating compressor operation to determine an appropriate constant control setting. This determination may be based on initial operation of the compressor during startup. In some examples involving cascaded vapor compression systems, this determination may occur after startup when both compressors are circulating refrigerant through an interstage heat exchanger. Other methods may also be used to set the constant control setting.

[0090] When the measured parameter is within the high proportional band limit and the low proportional band limit, but outside the target parameter band range 516, the constant band control process 500 can also utilize other control processes. In the example shown, a proportional rate control 518 is shown. This control 518 can be used to adjust the operating level of the compressor based on whether the measured parameter is above or below the target parameter band range 516. In some examples, the proportional rate control 518 is used to adjust the operating level of the compressor based on various proportional processes. In some examples, the proportional rate control 518 may include multiple controls. For example, different controls may be used when the measured parameter is above the set point 506 (e.g., 518A) and when the measured parameter is below the set point 506 (e.g., 518B). In some examples, different rate controls are used before determining the constant control setting 514.

[0091] Proportional rate control 518 can use various proportional processes. These processes can be used to proportionally adjust the operating level based on a measured parameter and a proportionality factor (e.g., a constant value used to determine the proportional adjustment rate). For example, the operating level can be determined by interpolating the operating level based on a minimum operating level, a maximum operating level, and a proportionality factor. In these examples, a measured parameter 504 can be used, and the process can determine the relative position of the measured parameter x 504 between the upper proportional band limit 510 and the lower proportional band limit 512. The process can then determine the operating level 502 corresponding to this position through interpolation, with the proportionality factor being a value used to allow for this correspondence. In other examples, proportional rate control 518 can be used as part of a feedback process, using a gain value and an error associated with the difference between the measured parameter 504 and the set point 506. In these examples, the gain value can be considered a proportionality factor, which is multiplied by the error to provide a proportional adjustment term, which is then used to adjust the operating level. Similarly, other processes can also be used.

[0092] To introduce an illustrative example, the proportional rate control 518 may be used to determine the operating level based on interpolation. Equation (1) that may be used as part of this interpolation is provided below:

[0093] In the above equation (1), "Op. Level" is an operating level, such as operating level 502. "Maximum Level" and "Minimum Level" are the maximum operating level and the minimum operating level, such as maximum operating level 520 and minimum operating level 522. "Measured Parameter" is measured parameter 504, and "Upper Limit" and "Lower Limit" are the upper and lower limits of the measured parameter, such as high proportional band limit 510 and low proportional band limit 512.

[0094] Furthermore, in the above equation, the proportionality factor is expressed as the following term:

[0095] In other words, in the example shown, the proportionality factor is the slope of the line, e.g., the rise during operation, as shown in proportional rate control 518. In this example, the proportionality factor is multiplied by the difference between the measured parameter 504 and the lower proportional band limit 512. This allows for interpolation between proportional bands using the measured parameter. The relative position of the measured parameter within the proportional band, e.g., between the upper and lower proportional band limits, is used to determine the corresponding relative operating level between the upper and lower operating limits. The relative operating level value is then added to the minimum operating level to determine the appropriate operating level based on the measured parameter.

[0096] It will be appreciated that other similar interpolation processes may be used. For example, comparing the high proportional band limit 510 to the measured parameter may be used to determine the relative position of the measured parameter. Knowing this relative position, a corresponding relative operating level may be determined, which may then be subtracted from the maximum operating level to determine an appropriate operating level based on the measured parameter.

[0097] Furthermore, as described above, in some examples, a proportional feedback process is used. In these examples, a proportional term can be based on a gain value and an error, and this term can be used to adjust the operating level of the compressor. In these examples, the error value can be based on the difference between a measured set point (e.g., 504) and a measured parameter (e.g., 504). This error value can be multiplied by a gain value, such as a proportional coefficient, to determine the proportional term. This proportional term can be used as feedback to adjust the current operating parameter. Similarly, it will be appreciated that other proportional controls can be used to adjust the operating level based on the proportional coefficient 518.

[0098] Go to Figure 5B , the process of the example constant band control process 500 is described with reference to the figures discussed above in conjunction with the illustrated process flow. Figure 5BIn the example shown, process flow 550 describes the steps of the constant band control process 500. These steps include starting the operation as shown in step 552, adjusting the operation based on proportional control as shown in step 554, determining the constant control setting as shown in step 556, and operating based on constant band control as shown in step 564. This process will be described in more detail below, and it will be appreciated that the constant band control process 500 may include more or fewer of the process steps discussed herein.

[0099] In some examples, process 550 may include starting compressor operation, as shown in step 552. When starting the compressor at this step, the measured parameter may be above the high proportional band limit 510, which may cause the compressor to operate at a maximum operating level. In some examples, step 552 includes starting the cascade vapor compression system after installation, which may be the first startup of the system after installation. In other examples, starting compressor operation may occur after a reset process, such as the reset process discussed in conjunction with step 574. Other processes may also be used.

[0100] As operation continues, the measured parameter may adjust and fall below the high proportional band limit 510, which may cause the process 550 to continue to step 554. In these examples, the constant band control process 500 can control the compressor operating level based on the proportional rate control 518, proportionally adjusting the compressor operation during this operating phase. For example, the compressor operation can be determined based on the interpolation process described above or by another process. In some examples, the measured parameter can move back above the high proportional band limit before moving to step 554. In these examples, the process can adjust between controlling the compressor operating level to an elevated level (e.g., a maximum operating level) if the measured parameter is above the high proportional band limit 510 and adjusting the compressor operation based on the proportional rate control 518 if the measured parameter is below the high proportional band limit 510.

[0101] As the compressor continues to operate, the measured parameter can continue to adjust, and when the measured parameter is within the target parameter band 516, process 550 can determine the constant control setting 514, as shown in step 556. The determination process can be initiated in various ways, as shown in 558. Once initiated, determination process 556 can include various steps, as shown in 560-564. For example, determining the constant control setting in step 556 can begin by recording the compressor operating level, as shown in 560. Once the measured parameter is within the target parameter band 516, this recording can begin and can be performed at regular increments, such as once per second, once per minute, etc. During this recording process, while the measured parameter is within the target parameter band, constant band control process 500 can continue to control the compressor operating level based on proportional rate control 518. This process can continue until the measured parameter leaves the target parameter band.

[0102] Once the measured parameter leaves the target parameter band range 516, the constant band control process 500 can set a constant control setting 514 based on the recorded information, as shown in step 562. For example, the compressor operating level (e.g., speed) can be averaged over the period, and the constant control setting can be set based on this average. Other processes, such as median values, mode values, or more complex processes such as regression analysis can be performed on the recorded operating levels to determine the appropriate constant control setting. Once determined, the constant band control process sets the constant control setting at the determined value, as shown in step 562. This set value can be used during subsequent runs of the constant control process.

[0103] In some examples, the control band process 550 initiates the process of determining a constant control setting in a first instance, as shown in step 558, and the first instance may continue until the constant control setting is set, as shown in step 562. For example, the first instance may be the first time a measured parameter enters the target parameter band 516 after the climate control system is powered on, or the first time the compressor is turned on. In some examples, the first instance ends once the measured parameter is outside the target parameter band 514. In some examples, the first instance is configured to span multiple cycles of measured temperatures within and outside the target parameter band 514, for example, the first two cycles, the first three cycles, etc. In some examples, the first instance is configured to span a period of time after the event occurs, for example, any time during the first day after the climate control system is powered on that the measured parameter is within the target parameter band. Other time periods and methods may be used to determine representative events of system operation within the target parameter band, which may be used to determine the constant control setting as described above.

[0104] In some examples, the determination process is only initiated at step 558 in a cascaded vapor compression system after both the first-stage compressor and the second-stage compressor begin circulating refrigerant. This can be advantageous because it allows the measured parameter to take into account the interaction of heat transfer between the stages. For example, if the measured parameter is associated with an interstage heat exchanger, waiting to initiate the determination process at step 556 until both the first-stage refrigerant and the second-stage refrigerant have flowed through the heat exchanger can allow the measured parameter to take into account the properties of each of these refrigerants, such as thermal properties, as well as the interaction between these flows.

[0105] Back to Figure 5B Once the constant control setting is determined through the above process (or other means), constant band control can control the compressor based on the constant control setting, as shown in step 564. As shown in step 566, if the measured temperature is above the upper proportional band limit 510, the process includes operating the compressor at a high level of operation, such as a maximum operating level. As shown in step 568, if the measured parameter is below the lower proportional band limit 512, it also includes operating the compressor at a low level of operation, such as a minimum operating level. The process also includes operating the compressor based on proportional rate control 518 if the measured parameter is between the upper and lower proportional band limits and also outside the target parameter band range 516, as shown in step 570. In addition, the process includes, in a second case, if the measured parameter is within the target parameter band range 516, setting the compressor operation to the constant control setting, as shown in step 572.

[0106] To further describe step 572, the second scenario can be a time after the constant band setting is determined and / or set, and the measured parameter is within the target parameter band. In some examples, the second scenario is when the measured parameter is within the target parameter band at each time, and the compressor is operating after the control setting 514 is determined and / or set. For example, in a cascade vapor compression system, it may be advantageous to operate the first stage compressor at a constant speed setting to provide a consistent heat sink (or heat source) for the second stage circuit. When the measured parameter is within the target parameter band and the compressor is operating, other time periods and methods can be used to determine when it is appropriate to operate the compressor at the constant control setting 514.

[0107] The constant band control process 500 may also include a reset process, as shown in step 574. This process may cause the constant band control process to redetermine the constant band control setting 514. This redetermination process may include some or all of the steps described above. This process may be initiated by the user or a given event, such as shutting down the climate control system, an error message, a diagnostic, etc.

[0108] Figure 6A and 6BAn example diagram and process flow associated with a proportional band control process (600) is shown. Figure 6A shows a schematic diagram for an example proportional band control process 600, Figure 6B A process flow for an example proportional band control process is shown. Both figures are used to illustrate the example process. In this discussion, the proportional band process 600 is discussed in conjunction with the second stage (104) of the cascade vapor compression system; however, it should be understood that the control process can be used with the first stage (102) in the cascade vapor compression system or any other process (e.g., a standard refrigerant process, etc.).

[0109] Figure 6A A schematic diagram of an example proportional band control process 600 is shown. As shown in the figure, the compressor operating level 602 is shown on the x-axis, which is based on Figure 6A The measured parameter 604 shown on the y-axis is mapped to the proportional band control process 600. In addition, the proportional band control process 600 also includes a set point 606, an upper proportional band limit 608, a lower proportional band limit 610, and a plurality of proportional bands 612 (A, B, C, ..., N). As discussed in more detail below, each of these proportional bands 612 includes a maximum operating level 614, a minimum operating level 616, and a proportional coefficient 618. These features will be described in more detail below.

[0110] With the above Figure 5A similar, Figure 6A The y-axis 602 in FIG. 5 represents the compressor operating level, which may be the operating speed of the compressor, or may be other parameters such as power level, capacity level, etc. Here, the compressor operating level may be a percentage from 0% to 100%. A 100% operating level may indicate the rated maximum operating level of the motor associated with the compressor. In some examples, the maximum operating level may be set differently, which may be based on calibration of the compressor and compressor motor during manufacturing or testing, during installation, or through different processes. It is further understood that other metrics related to compressor operation may be used. For example, an actual compressor speed value, such as an RPM value, or other metrics related to the operating level rate associated with compressor operation may be used.

[0111] Also similar to Figure 5A , Figure 6A The x-axis 604 in the figure represents a measured parameter. In some examples, the measured parameter is a measured temperature and / or pressure. In some examples, the measured parameter 604 can be used to control a second-stage compressor in a cascade vapor compression system, and in this example, the measured parameter can be the measured temperature of a chamber regulated by the cascade vapor compression system. In the example shown, the measured parameter value increases along the x-axis. Similarly, the measured parameter can be other measured temperatures, pressures, or other parameters used to control the compressor in the manner discussed herein.

[0112] Figure 6A The set point 606 in is a target value, which may be similar to the set point 506. In some examples, the set point may be a desired value for a given measured parameter. For example, in a secondary loop, the set point value may be a desired temperature for a chamber regulated by a cascade vapor compression system. In some examples, the set point value may be set by another process based on user preferences, one or more substances in the chamber (e.g., medical or chemical substances, etc.). In some examples, such as an ultra-low storage unit, the chamber set point may be -80°C. In some examples, the set point may be adjusted, perhaps by the manufacturer of the system, the operator of the system, a technician, etc. Other parameters and set points may be used, and it will be appreciated that if the control process is used in a different application, such as a non-cascade system, other considerations may be used in selecting the operating set point.

[0113] like Figure 6A As shown in FIG6 , the proportional band control process 600 may also include a high proportional band limit 608 and a low proportional band limit 610. These limits may be used to establish upper and lower limits for the proportional band. In some examples, these limits may be set based on the set point 606. For example, the high proportional band limit 608 may be a parameter setting that is higher than the set point 606. In these examples, when the measured temperature is at or above the high proportional band limit, such as a high temperature limit, the proportional control process 600 may set the operating level to a high operating level, which may be the maximum operating level for a given proportional band 612. Similarly, the low proportional band limit 610 may be a parameter setting that is lower than the set point 606. In these examples, when the measured temperature is at or below the low proportional band limit 610, such as a low temperature set point, the proportional control process 600 may operate at a low operating level, which may be the minimum operating level for a given proportional band 612.

[0114] To introduce an example, the set point 606 may be -80°C, which may be set as a desired temperature for a chamber in an ultra-low storage unit. In these examples, the high proportional band limit 608 may be set a certain amount above the set point 606. In this example, the high proportional band limit 608 is set to -78°C, or 2°C above the set point 606, and the low proportional band limit 610 is set to -81°C, or 1°C below the set point 606. In the example shown, the high proportional band limit 608 and the low proportional band limit 610 are the same for each of the plurality of proportional bands 612; however, as will be understood from the following discussion, in some examples, each proportional band may have its own high proportional band limit and / or low proportional band limit.

[0115] like Figure 6AAs shown in FIG, the proportional band control 600 may also include a plurality of proportional bands 612. Similarly, each of these proportional bands includes a maximum operating level 614, a minimum operating level 616, and a proportional coefficient 618. The maximum operating level 614 corresponds to the operating level for a given proportional band 612 when the measured parameter is at or above the high proportional band limit 608 for that proportional band. The minimum operating level 616 corresponds to the operating level for a given proportional band 612 when the measured parameter is at or below the low proportional band limit 610 for that proportional band. The proportional coefficient 618 is a proportional coefficient used to adjust the compressor operating level when the measured parameter is between the high proportional band limit 608 and the low proportional band limit 610.

[0116] A proportionality factor 618 can be used to adjust the operating level between a maximum operating level 614 and a minimum operating level 616 for a given proportional band 612. In some examples, the operating level can be adjusted by the proportionality factor in the same manner as discussed above in connection with the proportional rate control 518 associated with the constant band control process 500. For example, the operating level can be determined by interpolation, and the proportionality factor 618 can be used to determine the relative position of the measured parameter within the proportional band. As described above, this relative position of the measured parameter can be used to determine a corresponding relative operating level within the proportional band, for example, the relative operating level between the minimum operating level and the maximum operating level associated with the proportional band. In other examples, also similar to the above discussion, the adjustment process adjusts the operating level based on an error associated with the measured parameter 604 and the set point 606, as well as a gain value (e.g., the proportionality factor in these examples). Using this gain and error, the proportional control process 600 can adjust compressor operation to drive the measured parameter toward the set point 606. As discussed in more detail below, the proportional band control 600 can switch between these different proportional bands to determine the appropriate control band for the compressor to meet given conditions.

[0117] exist Figure 6A In the example shown in , the proportional bands 612 (A, B, ..., X, ...N) are arranged in sequence. In this example, each proportional band includes the same minimum operating level 616, and each proportional band includes a different maximum operating level 614. In this example, each maximum operating level 614 (X) of a given proportional band 612 (X) is less than the consecutive maximum operating level 614 (X+1) of the next proportional band 612 (X+1). In some examples, this may continue from the maximum overall operating level, which may be the maximum rated operating level of the compressor, to the minimum rated operating level. In some examples, including Figure 6A In the example shown in , such successive reductions occur at regular intervals 620 , eg, each successive maximum speed is lower than the next maximum speed by a regular amount, such as 5%, 100 RPM, etc.

[0118] To illustrate an example, for a given compressor, the maximum operating level for a first proportional band might be 100% of rated speed, while the minimum overall operating level for that compressor might be 30% of rated speed. In this example, the minimum operating level remains constant for all proportional bands, while the maximum operating level decreases with each successive operating level. Here, the first proportional band 612(A) has a minimum operating level 616(A) of 30% of rated speed and a maximum operating level 614(A) of 100% of rated speed. The next successive proportional band 612(B) has a minimum operating level 616(B) of 30% of rated speed, but the maximum operating level 614(B) is decreased by a regular amount. In this example, the regular amount is 5%, so the maximum operating level 614(B) is 95% of the rated speed for the second proportional band 612(B). In this example, the process continues, for example, with the third proportional band 612(C) having a minimum operating level 616(C) of 30% of rated speed and a maximum operating level of 90% of rated speed, and so on, as 612(D), 612(E), and so on. In this example, the proportional bands continue until the maximum operating level of a given proportional band is equal to or approximately equal to the minimum operating level of that given proportional band. Similarly, in this example, after 13 consecutive operating bands, the maximum operating level of the proportional band will be 35% of rated speed and the minimum operating level will be 30% of rated speed. In some examples, this may be the last proportional band in this example control process. In other examples, there may be another proportional band 612(X) where the minimum operating level 616(X) and the maximum operating level 614(X) are the same value.

[0119] It should be understood that the above is only one example of how various proportional bands may be configured to form a plurality of proportional bands for use in a proportional band control process. For example, for each proportional band 612, the maximum operating level 614 may remain constant, while the minimum operating level 616 may increase, possibly by a regular amount. In some examples, both the maximum operating level and the minimum operating level are adjusted for each proportional band. In some examples, the maximum operating level 614 and / or the minimum operating level are adjusted based on a multiplier and / or other factors. Other examples may also be utilized.

[0120] Furthermore, as described above, each proportional band 612 may also include a proportional coefficient 618. The proportional coefficient 618 may be the same or similar to the proportional coefficient discussed above in connection with the proportional rate control 518 used as part of the constant control process 500. Similar to this control, the proportional coefficient 618 in the proportional band control process 600 may be used to determine the rate of adjustment of the operating level when the measured parameter 602 is within a given proportional band 612. For example, the proportional coefficient 618 may be used to determine the relative position of the measured parameter and the corresponding operating level within the band based on interpolation. In other examples, the proportional control process 600 may compare the measured parameter 602 at a given time with the set point 606 to determine an error value. This error value may be adjusted based on the proportional coefficient 618, such as a gain, to adjust the compressor operating level to drive the measured parameter toward the set point. In some examples, this adjustment of the compressor operating level may be constrained by a minimum compressor operating level and a maximum compressor operating level for the given proportional band, e.g., the operating level may not exceed the maximum operating level for the given proportional band, nor fall below the minimum operating level for the given proportional band.

[0121] Furthermore, as described above, these proportional coefficients 618 may be different for each proportional band 612. Adjusting the proportional coefficients of the proportional bands has various advantages. For example, using proportional coefficients allows for adjustment of operating levels, but this process can also result in various problems, such as overshoot, oscillation, etc. Therefore, proportional coefficient values ​​are typically selected for a given system to maximize the benefits of that system and limit its problems. For example, a larger proportional coefficient may result in increased response time to errors and cause the system to drive toward the set point more quickly. However, this speed may come at the expense of increased undesirable problems, such as overshoot, oscillation, etc. In contrast, a lower proportional coefficient can reduce these undesirable problems, but may result in slower response time. Thus, allowing the system to switch between multiple proportional bands allows the disclosed control process to refine the proportional coefficients to values ​​appropriate for a given system and / or the conditions being handled by the system.

[0122] In some examples, the proportional coefficient 618 is the only regulation used by the proportional band control process 600. For example, each proportional band in the proportional band control process may not include an integral error term and / or a derivative error term. Thus, in some examples, the regulation process uses only a proportional error term and may regulate between different gains. Thus, in some examples, the regulation process is not a proportional and integral process, such as a PI process, nor is it a regulation process that uses a derivative error term, such as a PID process. Instead, in some examples, the proportional band control process 600 uses only a proportional process, such as a P process, to regulate the error. In these examples, the process 600 can switch between various proportional processes with different proportional coefficients to adjust and refine the control process to quickly and reliably achieve the set point.

[0123] Back to Figure 6A In the illustrated example, the proportionality factor 618(X) for each proportional band 612(N) is determined based on the maximum operating level 614(N) and the minimum operating level 616(X) for that proportional band. For example, in the illustrated example, the proportionality factor 618(X) for each proportional band 612(X) is based on the slope of the line for the given proportional band. In other words, in this example, the proportionality factor 618(X) is set to correspond to the rise of the illustrated proportional band 612(X) during operation. Thus, in this example, the proportionality factor 618(X) is the maximum operating level 614(X) minus the minimum operating level 616(X), e.g., exceeding the upper proportional band limit 608 minus the lower proportional band limit 610, e.g., travel. Thus, in the illustrated example, as the maximum operating level decreases, the proportionality factor also decreases for each successive operating level. This configuration can be advantageous because the proportional band continues to narrow its operating range and also decreases in proportionality factor. Thus, the illustrated proportional control process 600 provides a process for continually improving control to identify the optimal range of compressor operation and the appropriate control rate, thereby allowing for rapid adjustment of compressor operating levels, which limits undesirable consequences from incorrect proportional factors or other control processes.

[0124] To introduce an illustrative example, a regulation process using interpolation is described. In this example, the proportional bands are also arranged in sequence such that the minimum operating level 616(X) remains constant for each proportional band, while the maximum operating level 614(X) is reduced by a given amount. Furthermore, the proportional coefficient 618(X) is adjusted based on the corresponding adjustment to the maximum operating level. In this example process, the measured parameter is between the upper proportional band limit 608 and the lower proportional band limit 610. Thus, the proportional coefficient 618(X) is used to interpolate the given proportional band 612(X) and find the relative position of the operating speed corresponding to the relative position of the measured parameter within that band. The proportional band process continues to adjust the operating speed based on the updated measured parameter and the interpolation process associated with the given proportional band 612(X). However, if the proportional band fails to move the measured parameter to the setpoint, the proportional control process can switch to a different proportional band, such as 612(X+1), to adjust the operating level based on the measured parameter. Because different proportional bands, such as 612(X+1), include different values, such as different scaling factors and different maximum speeds, the updated proportional bands adjust the operating level differently based on the same measured parameter. For example, the updated proportional band 612(X+1) will interpolate the measured parameter to correspond to different operating levels because the corresponding operating levels in the updated proportional band 612(X+1) have different ranges between the maximum operating level 614(X+1) and the minimum operating level 616(X+1) based on the different scaling factors 618(X+1). Thus, the updated proportional band 612(X+1) may be better able to adjust the operating level 602 based on the measured parameter 604 to achieve the setpoint 606. If the updated proportional band does not perform adequately, the process continues to switch between the various proportional bands 612 to determine a proportional band 612 that appropriately adjusts the operation for the system and conditions.

[0125] Go to Figure 6B , shows an example process flow 630 that describes various steps that can be used as part of the proportional band control process 600. The process flow is referred to above in conjunction with Figure 6A The various controls discussed are discussed.

[0126] like Figure 6BAs shown in the example depicted in FIG, the process includes initiating compressor operation, as shown in step 632. The process also includes identifying an appropriate proportional band control, as shown in step 634, and operating the compressor at the identified proportional band, as shown in step 636. The process also includes switching between multiple proportional bands, as shown in step 638. As discussed in more detail below, the process includes various processes for switching between these bands. The process may also include identifying a shutdown setting, as shown in step 640, and the process may also include defrost control, as shown in step 642. It should be understood that proportional band control 600 may include more or fewer of these process steps.

[0127] To describe these process steps in more detail, the proportional band control process 600 may begin when the compressor starts, as shown in step 632. In some examples, this may occur when the climate control system is turned on, at which point the compressor may start. In other examples, for a second-stage compressor in a cascaded vapor compression system, the compressor may start in step 632 after an event occurs, such as after an interstage heat exchanger reaches a certain temperature. Other examples or events may cause the compressor to start, some of which will be discussed herein.

[0128] Once the compressor is started, the proportional band control process 600 includes identifying the appropriate proportional band control, as shown in step 634. For example, if the system is being turned on for the first time, or after a certain period of time, the proportional band control process 600 may begin the process at the first proportional band, which may be the proportional band with the highest operating level, e.g. Figure 6A 6(A+1). In other examples, the compressor may begin operating as a result of a given event or other operation, and a different proportional band may be identified. This may include identifying the last proportional band used by the proportional band control process 600, or identifying a proportional band that is higher or lower than the last proportional band used by the proportional band control process 600. Further examples are discussed below, and the disclosed process contemplates further implementations.

[0129] The proportional band control process 600 also includes operating the compressor at a given operating level, as shown in step 636. If the compressor has just started up, the proportional band control process 600 may operate the compressor at the proportional band 612 identified in step 634. If the compressor has been operating for some time, the proportional band control process 600 may have switched between various proportional bands, as discussed below in conjunction with step 638. In these examples, the proportional band control process 600 will operate the compressor according to the current proportional band identified based on this switching. Regardless, in some examples, the proportional band 612 used to operate and adjust compressor operation may be referred to as an operating proportional band.

[0130] In some examples, the proportional band control process 600 can operate the compressor based on the operating proportional band 612(X) as follows. If the measured parameter 604 is above the high proportional limit 608, the proportional band control process can operate the compressor at the maximum operating level 614(X) of the operating proportional band 612(X). If the measured parameter 604 is between the high proportional band limit 608 and the low proportional band limit 610, the proportional coefficient 618(X) of the operating proportional band 612(X) is used to adjust the operation of the compressor. As described above, this may include determining the relative position of the measured parameter within the proportional band and then applying the proportional coefficient 618(X) to that position to determine the appropriate adjustment to the compressor operating level. This adjustment to the operating level may be constrained by the minimum operating level 616(X) and the maximum operating level 614(X) of the operating proportional band 612(N). For example, adjustments based on the proportionality factor 618(X) may be limited to decreasing the compressor operating level to no less than the minimum operating level 616(X), or increasing the compressor operating level to no more than the maximum operating level 614(X).

[0131] In some examples, if the measured parameter 604 is below the low proportional band limit 610, the proportional band process 600 may also initiate a shutdown process discussed below in conjunction with step 640. In other cases, if the measured parameter 604 is below the low proportional band limit 610, the proportional band control process may operate the compressor at a minimum operating level 616(X) that operates the proportional band 612(X). In these cases, the low proportional band limit 610 may be a set point that is different from the power-off state.

[0132] Furthermore, in some examples, the proportional band control process 600 also includes switching between multiple proportional bands, as shown in step 638. In some examples, switching between multiple proportional bands includes switching from a given proportional band 612, which may be referred to as a first proportional band or a previous proportional band, to a proportional band with a higher or lower maximum operating level. For example, if a given proportional band 612 fails to achieve a measured parameter 604 equal to or less than a set point 606, the proportional band control process 600 may switch to a proportional band with a higher maximum operating level. Alternatively, in some examples, if a given proportional band 612 fails to achieve a measured parameter 604 equal to or less than a high proportional band limit 608 within a set time interval, the proportional band control process 600 may switch between proportional bands. Conversely, if a given proportional band 612 fails to achieve a measured parameter 604 equal to or greater than a set point 606 (or a low proportional band limit 610) within a set time interval, the proportional band control process 600 may switch to a proportional band with a lower maximum operating level. Other similar types of switching may be performed.

[0133] To introduce another example of such a switch shown in step 638, the Figure 6A As described above, in this example, the proportional band control process 638 includes a plurality of proportional bands, wherein each successive proportional band 612(X) includes the same minimum operating level 616(X) and a lower maximum operating level 614(X) than the previous proportional band 612(X-1). In addition, for each successive proportional band 612(X+1), the proportional coefficient 612(X) of the proportional band 612(X) also decreases, and this decrease is based on the decrease in the maximum operating level 614(X).

[0134] In this example, the proportional band control process 600 can switch from a given proportional band 612, which may be the first proportional band or the previous proportional band, to the operating proportional band 612 in response to a given event. In this example, the event may be that the operating compressor fails to drive the measured parameter 604 to the set point 606 within a set time interval based on the given proportional band 612 (X). Thus, if the measured parameter 604 remains above the set point 606 for a set period of time, such as if the measured parameter fails to reach or fall below the set point for a set period of time, the process can switch to a proportional band with a larger maximum operating level. Similarly, using Figure 6A , the process can switch from the previous proportional band 612(X) to an operating proportional band 612(X-1) having a maximum operating level increased by 5%. However, continuing with this example, if the measured parameter 604 remains below the set point 606 for a set period of time, e.g., if the measured parameter fails to reach or exceed the set point within the period of time, the process can switch to a proportional band having a lower maximum operating level. Thus, here, the process 600 can switch from the first or previous proportional band 612(X) to an operating proportional band 612(X+1) having a maximum operating level decreased by 5%. It should be understood that this switching process can be continued multiple times to continue driving the system to the appropriate proportional control band for a given system and / or state. It should also be understood that these values ​​may vary, and other coefficients and / or set points may be used when determining whether to switch between multiple proportional bands.

[0135] Furthermore, the set time period can be any time period suitable for the controlled system. For example, it can be a short time period, such as 10 minutes, 20 minutes, etc., or a longer time period, such as 1 day, 2 days, etc. Furthermore, the set time period can be the same when determining whether to switch to a higher or lower proportional band; in other examples, these time periods can be different. In some examples, the time period begins at any point when measured parameter 604 is not within set point 606. For example, the time period can begin as soon as the system switches to a given proportional band, which typically occurs because measured parameter 604 is not within set point 606. Alternatively, in some examples, the time period can begin after measured parameter 604 is within set point 606 and then deviates from it for some reason (e.g., load change, component problem, etc.). In these cases, set point 606 can have a tolerance level, such as 0.1°C, and the time period can begin once the measured parameter exceeds the set point, such as a measured value of -79.9°C. Furthermore, in some examples, once the time period begins, it may continue until reset or expires.

[0136] Furthermore, in some examples, the time period may only be reset based on certain conditions. For example, the time period may only be reset when the measured parameter 604 reaches the set point 606. If the measured parameter 604 deviates outside the proportional band limits, such as falling below the high proportional band limit 608 and / or rising above the low proportional band limit 610, the time period may not be reset. To illustrate an example, process 600 may be in a given proportional band 612(X), and the measured parameter 604 may be above the set point 606. Thus, process 600 may initiate a timer to determine whether a set time period has elapsed, causing process 600 to switch to a different operating proportional band. At this point, the measured temperature may be above the high proportional limit 608, causing the compressor to operate at the maximum level of the given proportional band 612(X). As the compressor continues to operate (and the timer continues), the measured parameter may drop below the high proportional band limit 610, causing the proportional band control process 600 to reduce compressor operation based on a given proportional factor (e.g., 618(X)). However, in some examples, the reduction in compressor operation does not cause the time period to reset, but rather the timer to continue. In this example, the timer continues until the measured parameter 604 reaches the set point 606, in which case the timer is reset and the process 600 continues to operate the compressor based on the given proportional band (e.g., 612(X)). Or, if the timer expires, e.g., the time period is reached, the process 606 switches to a different proportional band, in which case the proportional band will be a proportional band with a higher maximum operating level and the timer for that proportional band will operate in the same manner.

[0137] In some examples, the proportional band control process 600 also includes a shutdown setting, as shown in step 640. For example, the process 600 may include a setting to shut down the compressors. In some examples, such as for a cascade vapor compression system, this setting may cause both the first-stage compressor and the second-stage compressor to shut down. In these examples, the shutdown setting may be triggered when the measured parameter 604 is at or below a certain level, which may be below a low proportional band limit 610 or other shutdown condition. For example, if the measured parameter is the temperature of a chamber regulated by the cascade control system, and the setpoint is a desired temperature for the chamber, such as -80°C, then the shutdown condition (the low proportional band limit in this example) may be a temperature below the chamber setpoint by a given amount, such as 1°C. In these examples, if the measured chamber temperature is below -81°C, the process 600 may shut down one or more compressors of the cascade vapor compression system. For example, in response to the measured chamber temperature being -81°C or below, the process 600 may shut down the second-stage compressor and may also shut down the first-stage compressor. In some examples, the shutdown condition (and possibly the corresponding shutdown setting) can be the same for all proportional bands. For example, if the shutdown condition is met, the shutdown setting can be triggered regardless of which proportional band is controlling the compressor operation at the time. It is further understood that other conditions or multiple conditions can be used as the shutdown condition. For example, the above example can also include a timer, and the shutdown setting will only be activated after a certain time of the shutdown setting is reached. In some examples, the shutdown setting may be triggered when an overpressure deviation or other fault condition occurs.

[0138] In these examples, once compressor operation is restarted after a shutdown condition occurs, the proportional band control process 600 can adjust the operating proportional band 612. Continuing with the above example, if one or more compressors of the cascade vapor compression system shut down due to a measured chamber temperature equal to or below -81°C, when the system is restarted, the proportional band control process 600 can switch to a lower proportional band 612 as the operating proportional band. For example, if a shutdown condition occurs while the compressor is operating at a given proportional band 612(X), upon restart, the process 600 can switch to controlling the compressor at the next lower proportional band 612(X+1) with a lower maximum operating speed. Similarly, other processes can be used, as can adjustments.

[0139] In some examples, the proportional band control process 600 also includes defrost control, as shown in step 642. In these examples, a system using the proportional band control process 600 (e.g., a climate control system) may include a defrost setting. In these examples, the defrost setting may result in a change in the operation of one or more components of the climate control system, and the process is typically to remove ice from one or more heat exchangers. In these examples, the defrost setting may override the proportional band control process 600 when a defrost process is required. However, once the defrost process is complete, the proportional band control process 600 may resume control of the compressor, and in these examples, the proportional band control process 600 may select the last proportional band 612 used for the control process. For example, the proportional band control process 600 may be used as described above, and it may or may not switch between various proportional bands 612. Thus, in this example, when the defrost process is initiated, the proportional band 612(X) is used to control the operating level of the compressor. Once the defrost process ends, the proportional band control process 600 then resumes control of the compressor based on the previously used proportional band 612(X).

[0140] Figure 7 Device 700 according to some example embodiments of the present disclosure is shown. Generally, a device according to example embodiments of the present disclosure may include, comprise, or be embodied in one or more fixed or portable electronic devices. Examples of suitable electronic devices include any controller, processor, or other electrical device discussed herein, as well as those not discussed herein: smartphones, tablet computers, laptop computers, desktop computers, workstation computers, server computers, PLCs, circuit boards, and the like. The device may include one or more of each of a number of components, such as a processor 702 coupled to a memory 704.

[0141] Processor 702 is generally any computer hardware capable of processing information, such as data, computer programs, and / or other suitable electronic information. A processor includes one or more electronic circuits, some of which may be packaged as an integrated circuit or multiple interconnected integrated circuits (integrated circuits are sometimes more commonly referred to as "chips"). Depending on the specific implementation, the processor may be multiple processors, a multi-core processor, or some other type of processor.

[0142] The processor 702 may be configured to execute a computer program, such as computer-readable program code 706, which may be stored on the processor or otherwise stored in the memory 704. In some examples, the processor may be embodied as or otherwise include one or more ASICs, FPGAs, etc. Thus, while the processor may be capable of executing a computer program to perform one or more functions, the processor of various examples may be capable of performing one or more functions without the aid of a computer program.

[0143] Memory 704 is generally any computer hardware capable of temporarily and / or permanently storing information (e.g., data, computer-readable program code 706 or other computer programs) and / or other suitable information. Memory can include volatile memory such as random access memory (RAM) and / or non-volatile memory such as a hard drive, flash memory, etc. In various cases, memory can be referred to as a computer-readable storage medium, which is a non-transitory device capable of storing information. In some examples, then, the computer-readable storage medium is non-transitory and has computer-readable program code stored therein, which, in response to execution by processor 702, causes device 700 to perform various operations as described herein, some of which can in turn cause the components discussed herein to perform various operations.

[0144] In addition to the memory 704, the processor 702 may also be connected to one or more peripheral devices, such as a network adapter 708, one or more input / output (I / O) devices, and the like. The network adapter is configured to connect the device 700 to one or more networks to enable the device to transmit and / or receive information via the one or more networks. This may include transmitting and / or receiving information via one or more networks using a wired or wireless connection using Wi-Fi, Bluetooth, BACnet, LonTalk, Modbus, ZigBee, Zwave, or other suitable wired or wireless communication protocols.

[0145] The 293 I / O devices may include one or more input devices 710 capable of receiving data or instructions for the device 700 and / or one or more output devices 712 capable of providing output from the device. Examples of suitable input devices include a keyboard, a keypad, etc., and examples of suitable output devices include a display device, such as one or more light emitting diodes (LEDs), an LED display, a liquid crystal display (LCD), etc.

[0146] As explained above and reiterated below, the present disclosure includes, but is not limited to, the following example embodiments.

[0147] Scheme 1: A method of controlling a cascade vapor compression system, the cascade vapor compression system including a first-stage compressor configured to circulate refrigerant in a first-stage refrigeration circuit and a second-stage compressor configured to circulate refrigerant in a second-stage refrigeration circuit, the method comprising: receiving a first measurement value that varies with time, the first measurement value indicating a first parameter related to the cascade vapor compression system; receiving a second measurement value that varies with time, the second measurement value indicating a second parameter related to the second-stage refrigeration circuit; controlling the speed of the first-stage compressor based on constant band control, wherein controlling the first-stage compressor based on constant band control comprises: when determining the first measurement value operating the first stage compressor at a constant speed setting while within a target parameter band, wherein the target parameter band is defined by a first set point and a band offset, and adjusting the speed of the first stage compressor based on proportional rate control when the first measured value is determined to be outside the target parameter band and within a first threshold and a second threshold; and controlling the speed of the second stage compressor based on proportional band control, wherein controlling the speed of the second stage compressor based on the proportional band control is based in part on the second measured value and the second set point, the proportional band control further comprising a plurality of proportional bands, each of the plurality of proportional bands comprising a proportional coefficient that is different from any other proportional band in the plurality of proportional bands.

[0148] Option 2: The method according to any of the options, wherein controlling the speed of the second-stage compressor based on proportional band control further includes: identifying an operating proportional band from a plurality of proportional bands, each of the plurality of proportional bands including a maximum operating speed, a minimum operating speed, and a proportional coefficient, and adjusting the speed of the second-stage compressor based on the operating proportional band and the second measurement value.

[0149] Option 3: A method according to any option, wherein controlling the speed of the first-stage compressor based on constant band control further includes: determining a constant speed setting during operation of the first-stage compressor in a first condition, the first condition occurring when the first measured value is within a target parameter band; and wherein, after the constant speed setting has been determined in the first condition and when it is determined that the first measured value is within the target parameter band, operating the compressor at the constant speed setting.

[0150] Option 4: A method according to any option, wherein determining the constant speed setting further includes: starting operation of the first-stage compressor, wherein, at startup, the first measurement value exceeds a first threshold; operating the first-stage compressor at a maximum speed while the first measurement value exceeds the first threshold; adjusting the speed of the first-stage compressor in response to the first measurement value falling below the first threshold, the adjustment including reducing the speed of the first-stage compressor based on a proportional rate control; in a first case, recording multiple operating speeds of the first-stage compressor while the first measurement value is within a target parameter band; and setting the constant speed setting based on the multiple recorded operating speeds.

[0151] Option 5: The method of any option, wherein setting the constant speed setting comprises setting the constant speed setting based on an average of a plurality of recorded operating speeds.

[0152] Option 6: A method according to any option, wherein controlling the speed of the first-stage compressor based on constant band control further includes: operating the first-stage compressor at a maximum speed setting when determining that the first measured value is above a first threshold; and operating the first-stage compressor at a minimum speed setting when determining that the first measured value is below a second threshold.

[0153] Option 7: The method of any option, wherein the constant band control further comprises receiving user input to set one or more of: a first set point, a band offset, a first threshold, and a second threshold.

[0154] Option 8: The method of any option, wherein the first temperature measurement is a temperature measurement associated with an interstage heat exchanger of the cascade vapor compression system, and wherein the first set point is a set point associated with the interstage heat exchanger.

[0155] Option 9: The method of any option, wherein the first set point is about -23°C and the belt deflection in either direction at the set point is about 1°C.

[0156] Embodiment 10: A method of controlling a cascade vapor compression system, the cascade vapor compression system including a first-stage compressor configured to circulate refrigerant in a first-stage refrigeration circuit and a second-stage compressor configured to circulate refrigerant in a second-stage refrigeration circuit, the method comprising: receiving a first measurement value that varies over time, the first measurement value indicating a first parameter associated with the cascade vapor compression system; receiving a second measurement value that varies over time, the second measurement value indicating a second parameter associated with the second-stage refrigeration circuit; controlling the speed of the first-stage compressor based on constant band control, wherein controlling the speed of the first-stage compressor based on constant band control partially includes comparing the first measurement value to a first set point, the constant band control also including a constant speed setting; and controlling the speed of the second-stage compressor based on proportional band control, wherein controlling the speed of the second-stage compressor based on proportional band control includes: identifying an operating proportional band from a plurality of proportional bands, each of the plurality of proportional bands including a maximum operating speed, a minimum operating speed, and a proportional coefficient, wherein each of the plurality of proportional bands includes a proportional coefficient that is different from any other proportional band in the plurality of proportional bands, and adjusting the speed of the second-stage compressor based on the operating proportional band and the second measurement value.

[0157] Option 11: A method according to any option, wherein controlling the speed of the first-stage compressor based on constant band control further includes: operating the first-stage compressor at a constant speed setting when it is determined that the first measured value is within a target parameter band, wherein the target parameter band is defined by a first set point and a band offset, and adjusting the speed of the first-stage compressor based on proportional rate control when it is determined that the first measured value is outside the target parameter band and within a first threshold and a second threshold.

[0158] Option 12: The method of any of the options, wherein adjusting the speed of the second-stage compressor based on the operating proportional band further comprises: operating the second-stage compressor at a maximum operating speed of the operating proportional band when determining that the second measurement value is above a high set point, and adjusting the speed of the second-stage compressor based on a proportional coefficient of the operating proportional band when determining that the second temperature measurement value is between the high set point and the low set point.

[0159] Option 13: The method of any of the options, further comprising shutting down the first stage compressor and the second stage compressor in response to the second measured value being below a low set point.

[0160] Option 14: The method of any of the options, wherein identifying the operating proportional band further comprises switching from a previous proportional band to the operating proportional band in response to the second measured value being above a second set point for a set period of time.

[0161] Embodiment 15: The method of any embodiment, wherein the set time period continues in response to the second measurement being below the high set point, and the set time period restarts in response to the second measurement being equal to or below the second set point.

[0162] Embodiment 16: The method of any embodiment, wherein identifying the operating proportional band further comprises: switching from a previous proportional band to the operating proportional band in response to the second measured value being below a second set point for a set period of time.

[0163] Option 17: The method of any of the options, wherein identifying the operating proportional band further comprises switching between a plurality of proportional bands to identify the operating proportional band, wherein the switching occurs in response to the second measured value being above a second set point for a set period of time or below the second set point for a set period of time.

[0164] Option 18: A method according to any option, wherein each of the multiple proportional bands includes the same minimum operating speed and a different maximum operating speed, wherein the different maximum operating speeds differ based on a regular amount such that each successive maximum operating level is less than the previous maximum operating speed by the regular amount, and wherein the proportional coefficient of each of the multiple proportional bands is based on the minimum operating speed and the maximum operating speed of the respective proportional band.

[0165] Embodiment 19: The method of any embodiment, wherein the proportional band control further comprises receiving user input to set one or more of the following: a second set point, a set time period, a low temperature set point, and a high temperature set point.

[0166] Embodiment 20: The method of any embodiment, wherein the second temperature measurement is a temperature measurement associated with a chamber conditioned by the cascade vapor compression system, and wherein the second set point is a set point associated with the chamber.

[0167] Item 21: The method of any of items 21, wherein the set point associated with the chamber is approximately -80°C.

[0168] Scheme 22: A method of controlling a cascade vapor compression system, the cascade vapor compression system including a first-stage compressor configured to circulate refrigerant in a first-stage refrigeration circuit and a second-stage compressor configured to circulate refrigerant in a second-stage refrigeration circuit, the method comprising: receiving a first measurement value that varies with time, the first measurement value indicating a measured parameter associated with the cascade vapor compression system; receiving a second measurement value that varies with time, the second measurement value indicating a measured parameter associated with the second-stage refrigeration circuit; controlling the speed of the first-stage compressor based on constant band control, wherein controlling the first-stage compressor based on constant band control includes: operating the first-stage compressor at a constant speed setting when determining that the first measurement value is within a target parameter band A machine, wherein a target parameter band is defined by a first set point and a band offset; and upon determining that the first measured value is outside the target parameter band and within a first threshold and a second threshold, adjusting the speed of the first stage compressor based on proportional rate control; and controlling the speed of the second stage compressor based on proportional band control, wherein controlling the speed of the second stage compressor based on proportional band control includes: identifying an operating proportional band from a plurality of proportional bands, each of the plurality of proportional bands including a maximum operating speed, a minimum operating speed, and a proportional coefficient, wherein each of the plurality of proportional bands includes a proportional coefficient that is different from any other proportional band in the plurality of proportional bands, and adjusting the speed of the second stage compressor based on the operating proportional band and the second measured value.

[0169] Option 23: A method according to any option, wherein adjusting the speed of the second-stage compressor based on the operating proportional band further includes: operating the second-stage compressor at the maximum operating speed of the operating proportional band when it is determined that the second measured value is higher than the high set point, and adjusting the speed of the second-stage compressor based on a proportional coefficient of the operating proportional band when it is determined that the second measured value is between the high set point and the low set point.

[0170] Option 24: A method according to any option, wherein the first measurement value is a temperature measurement value associated with an interstage heat exchanger of a cascaded vapor compression system, and wherein the first set point is a temperature set point associated with the interstage heat exchanger, the first set point is approximately -23°C, and the band offset is approximately 1°C in any direction of the first set point; and wherein the second measurement value is a temperature measurement value associated with a chamber regulated by the cascaded vapor compression system, and wherein the second set point is a temperature set point associated with the chamber, and the second set point is approximately -80°C.

[0171] Option 25: A cascade vapor compression system, comprising: a first-stage compressor configured to circulate refrigerant in a first-stage refrigeration circuit; a second-stage compressor configured to circulate refrigerant in a second-stage refrigeration circuit; and a controller operably coupled to the first-stage compressor and the second-stage compressor, the controller comprising a processor and a memory, the memory configured to store computer-readable program code, the program code comprising a control-related software application; the processor configured to access the memory and execute the computer-readable program code to cause the processor to at least: receive a first measurement value that varies with time, the first measurement value indicating a first parameter associated with the cascade vapor compression system; receive a second measurement value that varies with time, the second measurement value indicating a second parameter associated with the second-stage refrigeration circuit; and control the first-stage compressor based on constant band control. The method of claim 1 further comprising causing the processor to: operate the first stage compressor at a constant speed setting when it is determined that the first measured value is within a target parameter band, wherein the target parameter band is defined by a first set point and a band offset; and adjust the speed of the first stage compressor based on proportional rate control when it is determined that the first measured value is outside the target parameter band and within a first threshold and a second threshold; and control the speed of the second stage compressor based on proportional band control, wherein controlling the speed of the second stage compressor based on the proportional band control is based in part on the second measured value and the second set point, and the proportional band control further comprises a plurality of proportional bands, each of the plurality of proportional bands comprising a proportional coefficient that is different from any other proportional band in the plurality of proportional bands.

[0172] Option 26: A cascade vapor compression system according to any of the options, wherein causing the processor to control the speed of the second-stage compressor based on proportional band control also includes: identifying an operating proportional band from a plurality of proportional bands, each of the plurality of proportional bands including a maximum operating speed, a minimum operating speed, and a proportional coefficient, and adjusting the speed of the second-stage compressor based on the operating proportional band and the second measurement value.

[0173] Option 27: A cascade vapor compression system according to any option, wherein causing the processor to control the speed of the first-stage compressor based on constant band control also includes causing the processor to: determine a constant speed setting during operation of the first-stage compressor in a first situation, the first situation occurring when the first measured value is within a target parameter band; and wherein causing the processor to operate the compressor at the constant speed setting also includes causing the processor to operate the compressor at the constant speed setting after the constant speed setting has been determined in the first situation and when it is determined that the first measured value is within the target parameter band.

[0174] Option 28: A cascaded vapor compression system according to any option, wherein causing the processor to determine the constant speed setting also includes causing the processor to: start operation of the first-stage compressor, wherein, at startup, the first measurement value exceeds a first threshold; when the first measurement value exceeds the first threshold, operate the first-stage compressor at a maximum speed; in response to the first measurement value falling below the first threshold, adjust the speed of the first-stage compressor, the adjustment including reducing the speed of the first-stage compressor based on proportional rate control; in a first case, when the first measurement value is within a target parameter band, record multiple operating speeds of the first-stage compressor; and set the constant speed setting based on the multiple recorded operating speeds.

[0175] Embodiment 29: The cascade vapor compression system of any of the embodiments, wherein causing the processor to set the constant speed setting further comprises causing the processor to set the constant speed setting based on an average of a plurality of recorded operating speeds.

[0176] Option 30: A cascade vapor compression system according to any option, wherein causing the processor to control the speed of the first-stage compressor based on constant band control also includes causing the processor to: operate the first-stage compressor at a maximum speed setting when determining that the first measurement value is above a first threshold; and operate the first-stage compressor at a minimum speed setting when determining that the first measurement value is below a second threshold.

[0177] Option 31: The cascade vapor compression system according to any option further includes: an interstage heat exchanger configured to transfer thermal energy between the first-stage refrigerant circuit and the second-stage refrigerant circuit; and wherein the first temperature measurement is a temperature measurement associated with the interstage heat exchanger, and wherein the first set point is a temperature set point associated with the interstage heat exchanger, wherein the first set value is approximately -23°C and the band offset in either direction of the set point is approximately 1°C.

[0178] Option 32: The cascade vapor compression system of any option, wherein the processor is configured to access the memory and execute the computer-readable program code, further comprising causing the processor to: receive user input to set one or more of: a first set point, a band offset, a first threshold, and a second threshold.

[0179] Option 33: A cascade vapor compression system, comprising: a first-stage compressor configured to circulate refrigerant in a first-stage refrigeration circuit; a second-stage compressor configured to circulate refrigerant in a second-stage refrigeration circuit; and a controller operably coupled to the first-stage compressor and the second-stage compressor, the controller comprising a processor and a memory, the memory configured to store computer-readable program code, the program code comprising a control-related software application; the processor configured to access the memory and execute the computer-readable program code to cause the processor to at least: receive a first measurement value that varies with time, the first measurement value indicating a first parameter associated with the cascade vapor compression system; receive a second measurement value that varies with time, the second measurement value indicating a second parameter associated with the second-stage refrigeration circuit parameters; controlling the speed of the first stage compressor based on constant band control, wherein controlling the speed of the second stage compressor based on constant band control includes, in part, a comparison between the first measurement and the first set point, the constant band control also including a constant speed setting; and controlling the speed of the second stage compressor based on proportional band control, wherein controlling the speed of the second stage compressor based on proportional band control includes causing the processor to: identify an operating proportional band from a plurality of proportional bands, each of the plurality of proportional bands including a maximum operating speed, a minimum operating speed, and a proportional coefficient, wherein each of the plurality of proportional bands includes a proportional coefficient that is different from any other proportional band in the plurality of proportional bands, and adjust the speed of the second stage compressor based on the operating proportional band and the second measurement.

[0180] Embodiment 34: The cascade vapor compression system of any embodiment, wherein causing the processor to control the speed of the first stage compressor based on constant band control further comprises causing the processor to: operate the first stage compressor at a constant speed setting when determining that the first measured value is within a target parameter band, wherein the target parameter band is defined by a first set point and a band offset, and adjust the speed of the first stage compressor based on proportional rate control when determining that the first measured value is outside the target parameter band and within a first threshold and a second threshold;

[0181] Option 35: A cascade vapor compression system according to any of the options, wherein causing the processor to adjust the speed of the second-stage compressor based on the operating proportional band further includes causing the processor to: operate the second-stage compressor at the maximum operating speed of the operating proportional band when determining that the second measurement value is above the high set point, and adjust the speed of the second-stage compressor based on a proportional coefficient of the operating proportional band when determining that the second temperature measurement value is between the high set point and the low set point.

[0182] Option 36: The cascade vapor compression system of any of the options, wherein the processor is configured to access the memory and execute the computer-readable program code, further comprising causing the processor to: shut down the first stage compressor and the second stage compressor in response to the second measured value being below the low set point.

[0183] Embodiment 37: The cascade vapor compression system of any of the embodiments, wherein causing the processor to identify the operating proportional band further comprises causing the processor to: switch from a previous proportional band to the operating proportional band in response to the second measured value being above a second set point for a set period of time.

[0184] Embodiment 38: The cascade vapor compression system of any of the embodiments, wherein the set time period continues in response to the second measured value being less than the high set point, and wherein the set time period restarts in response to the second measured value being equal to or less than the second set point.

[0185] Embodiment 39: The cascade vapor compression system of any of the embodiments, wherein causing the processor to identify the operating proportional band further comprises causing the processor to: switch from a previous proportional band to the operating proportional band in response to the second measured value being below a second set point for a set period of time.

[0186] Option 40: A cascade vapor compression system according to any of the options, wherein causing the processor to identify the operating proportional band further comprises causing the processor to: switch between a plurality of proportional bands to identify the operating proportional band, wherein the switching occurs in response to the second measured value being above a second set point for a set time period or below the second set point for a set time.

[0187] Option 41: A cascade vapor compression system according to any option, wherein each of the plurality of proportional bands includes a same minimum operating speed and a different maximum operating speed, wherein the different maximum operating speeds differ based on a regular amount such that each successive maximum operating level is less than the previous maximum operating speed by the regular amount, and wherein the proportional coefficient of each of the plurality of proportional bands is based on the minimum operating speed and the maximum operating speed of the respective proportional band.

[0188] Option 42: A cascade vapor compression system according to any option, wherein the second measurement is a temperature measurement associated with a chamber regulated by the cascade vapor compression system, and wherein the second set point is a temperature set point associated with the chamber, wherein the second set point is approximately -80°C.

[0189] Option 43: A cascade vapor compression system according to any of the options, wherein the processor is configured to access the memory and execute the computer-readable program code, further comprising causing the processor to: receive user input to set one or more of the following: a second set point, a set time period, a low temperature set point, and a high temperature set point.

[0190] Option 44: A cascade vapor compression system, comprising: a first-stage compressor configured to circulate refrigerant in a first-stage refrigeration circuit; a second-stage compressor configured to circulate refrigerant in a second-stage refrigeration circuit; and a controller operably coupled to the first-stage compressor and the second-stage compressor, the controller comprising a processor and a memory, the memory configured to store computer-readable program code, the program code comprising a control-related software application; the processor configured to access the memory and execute the computer-readable program code to cause the processor to at least: receive a first measurement value that varies with time, the first measurement value indicating a first parameter associated with the cascade vapor compression system; receive a second measurement value that varies with time, the second measurement value indicating a second parameter associated with the second-stage refrigeration circuit; control the speed of the first-stage compressor based on constant band control, wherein the processor is configured to control the speed of the first-stage compressor based on the constant band control The method of claim 1 further comprising causing the processor to: operate the first stage compressor at a constant speed setting upon determining that the first measured value is within a target parameter band, wherein the target parameter band is defined by a first set point and a band offset, and adjust the speed of the first stage compressor based on proportional rate control upon determining that the first measured value is outside the target parameter band and within a first threshold and a second threshold; and control the speed of the second stage compressor based on proportional band control, wherein causing the processor to control the speed of the second stage compressor based on proportional band control includes causing the processor to: identify an operating proportional band from a plurality of proportional bands, each of the plurality of proportional bands including a maximum operating speed, a minimum operating speed, and a proportional coefficient, wherein each of the plurality of proportional bands includes a proportional coefficient different from any other proportional band in the plurality of proportional bands, and adjust the speed of the second stage compressor based on the operating proportional band and the second measured value.

[0191] Option 45: A cascade vapor compression system according to any of the options, wherein causing the processor to adjust the speed of the second-stage compressor based on the operating proportional band also includes causing the processor to: operate the second-stage compressor at the maximum operating speed of the operating proportional band when it is determined that the second measured value is higher than the high set point, and adjust the speed of the second-stage compressor based on a proportional coefficient of the operating proportional band when it is determined that the second measured value is between the high set point and the low set point.

[0192] Option 46: The cascade vapor compression system according to any option further includes: an interstage heat exchanger configured to transfer thermal energy between the first-stage refrigerant circuit and the second-stage refrigerant circuit; and wherein the first measurement value is a temperature measurement value associated with the interstage heat exchanger, and wherein the first set point is a temperature set point associated with the interstage, the first set value is approximately -23°C, and the band offset in either direction of the first set point is approximately 1°C; and wherein the second measurement value is a temperature measurement value associated with a chamber regulated by the cascade vapor compression system, and wherein the second set point is a temperature set point associated with the chamber, and the second set point is approximately -80°C.

[0193] Thanks to the teachings of the above description and the associated drawings, those skilled in the art to which the present disclosure pertains will appreciate many modifications and other embodiments of the present disclosure as described herein. Therefore, it should be understood that the present disclosure is not limited to the specific embodiments disclosed, and modifications and other embodiments are intended to be included within the scope of the appended claims. In addition, although the above description and the associated drawings describe example embodiments in the context of certain example combinations of elements and / or functions, it should be understood that different combinations of elements and / or functions can be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, as set forth in some of the appended claims, it is also possible to envision combinations of elements and / or functions that are different from the elements and / or functions explicitly described above. Although specific terms are used in the text, they are used only in a general and descriptive sense, and not for the purpose of limitation.

Claims

1. A method of controlling a cascade vapor compression system, the cascade vapor compression system comprising a first-stage compressor configured to circulate refrigerant in a first-stage refrigeration circuit and a second-stage compressor configured to circulate refrigerant in a second-stage refrigeration circuit, the method comprising: receiving a first measurement over time, the first measurement indicative of a first parameter associated with the cascade vapor compression system; receiving a second measurement over time, the second measurement indicative of a second parameter associated with the second stage refrigeration circuit; Controlling the speed of the first-stage compressor based on constant band control, wherein controlling the first-stage compressor based on the constant band control includes: operating the first stage compressor at a constant speed setting when it is determined that the first measurement is within a target parameter band, wherein the target parameter band is defined by a first set point and a band offset, When the first measurement is determined to be outside the target parameter band and within first and second thresholds, adjusting the speed of the first stage compressor based on proportional rate control; and The speed of the second stage compressor is controlled based on a proportional band control, wherein the controlling of the speed of the second stage compressor based on the proportional band control is based in part on the second measurement and a second set point, the proportional band control further comprising a plurality of proportional bands, each of the plurality of proportional bands comprising a proportional coefficient that is different from any other proportional band in the plurality of proportional bands.

2. The method according to claim 1, characterized in that Controlling the speed of the second-stage compressor based on the proportional band control further includes: identifying an operating proportional band from the plurality of proportional bands, each of the plurality of proportional bands comprising a maximum operating speed, a minimum operating speed, and a proportional factor, and The speed of the second stage compressor is adjusted based on the operating proportional band and the second measurement.

3. The method according to claim 1, characterized in that Controlling the speed of the first stage compressor based on the constant band control further includes: determining the constant speed setting during operation of the first stage compressor in a first condition, the first condition occurring when the first measured value is within the target parameter band; and wherein the compressor is operated at the constant speed setting after the constant speed setting has been determined in the first condition and upon determining that the first measured value is within the target parameter band.

4. The method according to claim 3, characterized in that Determining the constant speed setting further comprises: Starting the operation of the first stage compressor, wherein, at the time of starting, the first measurement value exceeds the first threshold; operating the first stage compressor at a maximum speed while the first measurement exceeds the first threshold; adjusting the speed of the first stage compressor in response to the first measurement falling below the first threshold, the adjusting comprising decreasing the speed of the first stage compressor based on the proportional rate control; In the first case, when the first measurement value is within the target parameter band, recording a plurality of operating speeds of the first stage compressor; and The constant speed setting is set based on the recorded plurality of operating speeds.

5. The method according to claim 4, characterized in that Setting the constant speed setting includes setting the constant speed setting based on an average of the recorded plurality of operating speeds.

6. The method according to claim 1, characterized in that Controlling the speed of the first stage compressor based on the constant band control further includes: Upon determining that the first measurement is above the first threshold, operating the first stage compressor at a maximum speed setting; and Upon determining that the first measurement is below the second threshold, the first stage compressor is operated at a minimum speed setting.

7. The method according to claim 1, characterized in that The first temperature measurement is a temperature measurement associated with an interstage heat exchanger of the cascade vapor compression system, and Wherein the first set point is a temperature set point associated with the interstage heat exchanger, wherein the first set point is approximately -23°C and the band offset in either direction of the set point is approximately 1°C.

8. A method of controlling a cascade vapor compression system, the cascade vapor compression system comprising a first-stage compressor configured to circulate refrigerant in a first-stage refrigeration circuit and a second-stage compressor configured to circulate refrigerant in a second-stage refrigeration circuit, the method comprising: receiving a first measurement over time, the first measurement indicative of a first parameter associated with the cascade vapor compression system; receiving a second measurement over time, the second measurement indicative of a second parameter associated with the second stage refrigeration circuit; controlling the speed of the first stage compressor based on constant band control, wherein controlling the speed of the first stage compressor based on the constant band control includes, in part, a comparison between the first measurement and a first set point, the constant band control also including a constant speed setting; and The speed of the second-stage compressor is controlled based on proportional band control, wherein the controlling of the second-stage compressor based on the proportional band control includes: identifying an operating proportional band from a plurality of proportional bands, each of the plurality of proportional bands comprising a maximum operating speed, a minimum operating speed, and a proportional coefficient, wherein each of the plurality of proportional bands comprises a proportional coefficient that is different from any other proportional band in the plurality of proportional bands, and The speed of the second stage compressor is adjusted based on the operating proportional band and the second measurement.

9. The method according to claim 8, characterized in that Controlling the speed of the first stage compressor based on the constant band control further includes: operating the first stage compressor at the constant speed setting upon determining that the first measured value is within a target parameter band, wherein the target parameter band is defined by the first set point and a band offset, and Upon determining that the first measurement is outside the target parameter band and within first and second thresholds, the speed of the first stage compressor is adjusted based on proportional rate control.

10. The method according to claim 8, characterized in that Adjusting the speed of the second stage compressor based on the operating proportional band further includes: operating the second stage compressor at the maximum operating speed of the operating proportional band upon determining that the second measured value is above a high set point, and Upon determining that the second temperature measurement is between the high set point and the low set point, the speed of the second stage compressor is adjusted based on the proportional coefficient of the operating proportional band.

11. The method according to claim 8, characterized in that The method further comprises: In response to the second measurement being below a low set point, the first stage compressor and the second stage compressor are shut down.

12. The method according to claim 8, characterized in that Identifying the operating proportional band further includes: In response to the second measurement being above a second set point for a set period of time, a switch is made from the previous proportional band to the operating proportional band.

13. The method according to claim 12, characterized in that The set time period continues in response to the second measurement being below the high set point, and the set time period restarts in response to the second measurement being equal to or below the second set point.

14. The method according to claim 8, characterized in that Identifying the operating proportional band further includes: In response to the second measurement being below a second set point for the set period of time, a switch is made from the previous proportional band to the operating proportional band.

15. The method according to claim 8, characterized in that Identifying the operating proportional band further includes: switching between the plurality of proportional bands to identify the operating proportional band, The switching occurs in response to the second measurement value being higher than a second set point within a set time period or being lower than the second set point within the set time period.

16. The method according to claim 15, characterized in that Each of the plurality of proportional bands includes a same minimum operating speed and a different maximum operating speed, wherein the different maximum operating speeds differ based on a regular amount such that each successive maximum operating level is less than the previous maximum operating speed by the regular amount, and The proportional coefficient of each of the plurality of proportional bands is based on the minimum operating speed and the maximum operating speed of each proportional band.

17. The method according to claim 8, characterized in that The second measurement is a temperature measurement associated with a chamber conditioned by the cascade vapor compression system, and The second set point is a temperature set point associated with the chamber, wherein the second set point is approximately -80°C.

18. A method of controlling a cascade vapor compression system, the cascade vapor compression system comprising a first-stage compressor configured to circulate refrigerant in a first-stage refrigeration circuit and a second-stage compressor configured to circulate refrigerant in a second-stage refrigeration circuit, the method comprising: receiving a first measurement value as a function of time, the first measurement value being indicative of a measured parameter associated with the cascade vapor compression system; receiving a second measurement over time, the second measurement indicating a measured parameter associated with the second stage refrigeration circuit; Controlling the speed of the first-stage compressor based on constant band control, wherein controlling the first-stage compressor based on the constant band control includes: operating the first stage compressor at a constant speed setting upon determining that the first measurement is within a target parameter band, wherein the target parameter band is defined by a first set point and a band offset, and upon determining that the first measurement is outside the target parameter band and within first and second thresholds, adjusting the speed of the first stage compressor based on proportional rate control; and The speed of the second-stage compressor is controlled based on a proportional band control, wherein the speed of the second-stage compressor is controlled based on the proportional band control, comprising: identifying an operating proportional band from a plurality of proportional bands, each of the plurality of proportional bands comprising a maximum operating speed, a minimum operating speed, and a proportional coefficient, wherein each of the plurality of proportional bands comprises a proportional coefficient that is different from any other proportional band in the plurality of proportional bands, and The speed of the second stage compressor is adjusted based on the operating proportional band and the second measurement.

19. The method according to claim 18, characterized in that Adjusting the speed of the second stage compressor based on the operating proportional band further includes: operating the second stage compressor at the maximum operating speed of the operating proportional band upon determining that the second measured value is above a high set point, and When it is determined that the second measurement is between the high set point and the low set point, the speed of the second stage compressor is adjusted based on the proportional coefficient of the operating proportional band.

20. The method according to claim 18, wherein the first measurement being a temperature measurement associated with an interstage heat exchanger of the cascade vapor compression system, and wherein the first set point is a temperature set point associated with the interstage heat exchanger, and wherein the first set point is approximately -23°C, and the band offset is approximately 1°C in either direction of the first set point; and wherein the second measurement is a temperature measurement associated with a chamber conditioned by the cascade vapor compression system, and wherein the second set point is a temperature set point associated with the chamber, the second set point being approximately -80°C.

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