CN105526670B

CN105526670B - Apparatus and method for subcooling control based on superheat set point control

Info

Publication number: CN105526670B
Application number: CN201510672789.XA
Authority: CN
Inventors: 林之勇; 贝内迪克特·J·多尔奇赫; 约翰·F·朱奇
Original assignee: Dimension Corp
Current assignee: Dimension Corp
Priority date: 2014-10-15
Filing date: 2015-10-15
Publication date: 2021-06-15
Anticipated expiration: 2035-10-15
Also published as: CN105526670A

Abstract

An apparatus and method for subcooling control based on superheat setpoint control is disclosed. A system includes a setpoint module, a summer, a control module, and an expansion valve module. The set point module is configured to indirectly control subcooling of the condenser by adjusting a superheat set point based on (i) a return air temperature set point or a supply air temperature set point and (ii) an outdoor ambient temperature. The summer is configured to determine an error between the superheat setpoint and a superheat level of the compressor. The control module is configured to generate a control signal based on the error. The expansion valve module is configured to electronically control a state of the expansion valve based on the control signal.

Description

Apparatus and method for subcooling control based on superheat set point control

Cross Reference to Related Applications

The present disclosure is a continuation-in-part application of U.S. patent application No. 14/078,734 filed on 13/11/2013. This application claims benefit of U.S. provisional application No. 61/729,037 filed on day 11, 21, 2012. The entire disclosure of the above application is incorporated herein by reference.

Technical Field

The present disclosure relates to cooling systems, and more particularly to expansion valve control systems.

Background

This section provides background information related to the present disclosure that is not necessarily prior art.

The cooling system has applicability in a number of different applications where a fluid is to be cooled. The fluid may be a gas such as air or a liquid such as water. An example application is for cooling heating, ventilation, air conditioning (HVAC) systems in spaces where people are located, such as in offices and data centers. A data center may refer to a room having a collection of electronic devices, such as computer servers.

An air conditioner 50 that may be used in, for example, a computer room is shown in fig. 1. The air conditioner 50 includes a cooling circuit 51 and a cabinet 52. The cooling circuit 51 is disposed in the cabinet 52 and includes an evaporator 54, an air moving device 56, a compressor 58, a condenser 60, and an expansion valve 62. The evaporator 54, compressor 58, condenser 60, and expansion valve 62 are connected in a closed loop that circulates a cooling fluid (e.g., a phase change refrigerant). The evaporator 54 may include a V-coil assembly having a plurality of cooling plates (slab) to provide enhanced cooling capacity. The evaporator 54 receives a cooling fluid and cools air passing through openings in the evaporator 54. An air moving device 56, such as a fan or squirrel cage blower, draws air from an inlet (not shown) in the cabinet 52 and through the evaporator 54. The cooled air is directed out of the evaporator 54 and out of a plenum 64 in the cabinet 52.

The compressor 58 circulates cooling fluid through a condenser 60, an expansion valve 62, the evaporator 54, and back to the compressor 58. The compressor 58 may be, for example, a scroll compressor. The scroll compressor may be a fixed speed, digital or variable speed compressor. Scroll compressors typically include two offset spiral disks. The first spiral is a fixed or scroll portion. The second spiral is an orbiting scroll. The cooling fluid is received at the inlet of the scroll compressor, captured between the offset spiral disks, compressed, and discharged centrally (or at the outlet) toward the condenser 60. The condenser 60 may be a microchannel condenser that cools the cooling fluid received from the compressor 58. The expansion valve 62 may be an electronic expansion valve and may expand the cooling fluid exiting the condenser 60, e.g., from a liquid to a gas.

The position of the expansion valve 62 (or the percentage of opening of the expansion valve) may be adjusted to control the suction superheat value of the compressor 58. The suction superheat value of the compressor is equal to the compressor suction temperature minus the compressor saturated suction temperature. The compressor suction pressure may be used to determine the compressor saturation suction temperature. The compressor suction temperature and compressor suction pressure may be determined based on signals from respective sensors connected between evaporator 54 and compressor 58. Superheat values refer to the amount by which the temperature of the cooling fluid in the gaseous state is heated above the saturated suction temperature of the compressor.

The superheat value may be used to adjust (or regulate) the position of the expansion valve 62. Control of the position (or percentage of opening) of the expansion valve 62 may be performed by a proportional, integral, derivative (PID) control module. The PID control module controls the superheat value to match a constant predetermined superheat setpoint. This ensures compressor stability and improves compressor efficiency.

Disclosure of Invention

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

A system is provided that includes a setpoint module, a summer, a control module, and an expansion valve module. The set point module is configured to indirectly control subcooling of the condenser by adjusting a superheat set point based on (i) a return air temperature set point or a supply air temperature set point and (ii) an outdoor ambient temperature. The summer is configured to determine an error between the superheat setpoint and a superheat level of the compressor. The control module is configured to generate a control signal based on the error. The expansion valve module is configured to electronically control a state of the expansion valve based on the control signal. The setpoint module is configured to: obtaining a plurality of adjustment factors for adjusting the superheat setpoint, wherein the plurality of adjustment factors are predetermined values selected based on one of a plurality of types of systems and one of a plurality of settings, and wherein the plurality of adjustment factors include a first indoor adjustment factor, a second indoor adjustment factor, and an outdoor adjustment factor; selecting an operating mode from a plurality of operating modes, wherein the plurality of operating modes includes a first operating mode, a second operating mode, and a third operating mode, wherein when operating in each of the plurality of operating modes, the setpoint module calculates a superheat setpoint differently than when operating in other of the plurality of operating modes, during the first operating mode, the superheat setpoint is adjusted using a first indoor adjustment factor and an outdoor adjustment factor, during the second operating mode, the superheat setpoint is adjusted using an outdoor adjustment factor and a second indoor adjustment factor, and during the third operating mode, the superheat setpoint is adjusted using the first indoor adjustment factor, the second indoor adjustment factor, and the outdoor adjustment factor; and adjusting the superheat setpoint based on the selected operating mode.

In another aspect, a method is provided, comprising: indirectly controlling subcooling of the condenser by adjusting a superheat setpoint based on (i) a return air temperature setpoint or a supply air temperature setpoint and (ii) an outdoor ambient temperature; determining an error between the superheat setpoint and a superheat level of the compressor; generating a control signal based on the error; and electronically controlling a state of the expansion valve based on the control signal; obtaining a plurality of adjustment factors for adjusting the superheat setpoint, wherein the plurality of adjustment factors are predetermined values selected based on one of a plurality of types and one of a plurality of settings for the system, and wherein the plurality of adjustment factors include a first indoor adjustment factor, a second indoor adjustment factor, and an outdoor adjustment factor; selecting an operating mode from a plurality of operating modes, wherein the plurality of operating modes includes a first operating mode, a second operating mode, and a third operating mode, wherein when operating in each of the plurality of operating modes, an superheat setpoint is calculated differently than when operating in other of the plurality of operating modes; during a first mode of operation, adjusting the superheat setpoint using the first indoor adjustment factor and the outdoor adjustment factor; during a second mode of operation, adjusting the superheat setpoint using the outdoor adjustment factor and a second indoor adjustment factor; during a third mode of operation, adjusting the superheat setpoint using the first indoor adjustment factor, the second indoor adjustment factor, and the outdoor adjustment factor; and adjusting the superheat setpoint based on the selected operating mode.

In another aspect, a system is provided and includes an error module configured to integrate a difference between a superheat signal and a superheat setpoint to generate an error signal, wherein the superheat signal is indicative of a suction superheat value of a compressor. The comparison module is configured to compare the error signal to a first predetermined threshold to generate a first comparison signal based on the comparison. The zero-crossing module is configured to compare the first count value to a second predetermined threshold to generate a second comparison signal. The first count value is generated based on at least one comparison between the superheat signal and the superheat setpoint. The setpoint module is configured to adjust a superheat setpoint based on the first comparison signal and the second comparison signal.

In another aspect, a system is provided and includes a boundary counter, a boundary module, a setpoint module, and a control module. The boundary counter is configured to: the first count value is incremented when the superheat signal of the compressor exceeds a predetermined limit. The boundary module is configured to: the first count value is compared with a first predetermined threshold to generate a first comparison signal. The setpoint module is configured to: the superheat setpoint is adjusted based on the first comparison signal. The control module is configured to: the position of the expansion valve is adjusted based on the superheat setpoint.

In another aspect, a system is provided and includes an instability module, a discharge module, and a set point module. The instability module is configured to: determining whether an unstable suction superheat condition of the compressor exists, and generating an instability signal. The exhaust module is configured to: the discharge pressure of the compressor is compared with a predetermined pressure to generate a first comparison signal. The setpoint module is configured to: the superheat setpoint is adjusted based on the instability signal and the first comparison signal.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

Drawings

The drawings described herein are for illustrative purposes only of selected implementations and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 is a perspective view of a prior art air conditioner;

FIG. 2 is a schematic diagram of a multi-stage cooling system incorporating a cooling control module, according to one aspect of the present disclosure;

FIG. 3 is a functional block diagram of a superheat setpoint adjustment system according to an aspect of the present disclosure;

FIG. 4 is a functional block diagram of a portion of the cooling control module of FIG. 2 incorporating an unstable module, according to one aspect of the present disclosure;

FIG. 5 is a logic flow diagram illustrating a superheat setpoint adjustment method in accordance with an aspect of the present disclosure;

FIG. 6 is a functional block diagram of a superheat setpoint adjustment system, according to an aspect of the present disclosure; and

FIG. 7 is a logic flow diagram illustrating a method of superheat setpoint adjustment in accordance with an aspect of the present disclosure.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Detailed Description

Example implementations are now described more fully with reference to the accompanying drawings.

The air conditioning system may include a condenser (or outdoor coil), an expansion valve, an evaporator (or indoor coil), and a compressor. The position (or opening percentage) of the expansion valve may be adjusted to maintain the superheat value of the compressor at a predetermined (or adjusted) superheat setpoint. Unstable operation of the air conditioning system may be caused due to a change in indoor operating conditions of the air conditioning system. Examples disclosed herein prevent an unstable condition from occurring, and if an unstable condition occurs, examples stabilize an air conditioning system. This instability prevention and stabilization is provided by adjustment and/or regulation of the superheat setpoint.

Indoor operating conditions of an air conditioning system may change, for example, due to changes in required temperature and/or dehumidification settings. The varying operating conditions, the relative sizes of the capacities of the condenser and the evaporator, and the charge of cooling fluid in the evaporator being too low (less than the first predetermined charge) or too high (greater than the second predetermined charge) may result in unstable operation. The loading of the cooling fluid may refer to the amount or mass of the cooling fluid. The superheat value can be maintained in the presence of, for example, a low charge of cooling fluid in the evaporator to avoid high discharge (output) pressures of the compressor. The compressor may be turned off when a discharge pressure of the compressor is greater than a predetermined pressure. Maintaining the superheat value in the presence of a high charge of cooling fluid in the evaporator may result in a loss of subcooling from the condenser. The loss of subcooling may result in unstable compressor operation. Unstable compressor operation may result in unstable air conditioning system operation.

Implementations disclosed below include stabilizing superheat values for compressors under various operating conditions. Implementations include managing cooling fluid loading between an evaporator and a condenser for stable operation. This includes adjusting the superheat setpoint based on certain parameters (e.g., compressor suction pressure, compressor inlet temperature, and compressor discharge pressure). The above parameters depend on the operating conditions. Thus, implementations provide dynamic adjustment of the superheat setpoint for expansion valve position control. Implementations enable the superheat setpoint of the compressor to be stabilized to a suitable setpoint, which may be determined in real time (or during operation of the associated air conditioning system). If an unstable superheat condition is detected, superheat setpoint adjustment is performed to reset the superheat setpoint according to the current setting to rebalance the load between the evaporator and the condenser, which stabilizes the superheat value and system operation.

Fig. 2 shows a schematic view of the cooling system 100. The cooling system 100 may be a variable frequency air conditioning system and includes an upstream cooling stage 102 having an upstream (or first) cooling circuit 104 and a downstream (or second) cooling stage 106 having a downstream cooling circuit 108. The cooling

circuits

104, 108 are controlled via a cooling control module 109. Although two cooling circuits are shown, a different number of cooling circuits may be included. The upstream cooling circuit 104 includes a first evaporator 110, a first expansion valve 112, a first condenser 114, a first compressor 116, and a second compressor 118. The downstream cooling circuit 108 includes a second evaporator 120, a second expansion valve 122, a second condenser 124, a third compressor 126, and a fourth compressor 128. The

evaporators

110, 120 have respective

evaporator fans

130, 132. The

condensers

114, 124 have

respective condenser fans

134, 136.

The cooling control module 109 may generate condenser fan signals COND1, COND2, evaporator fan signals EVAP1, EVAP2, expansion valve signals EXP1, EXP2, and compressor signals PWM1, PWM2, PUMP3, PUMP4 to control the

fans

130, 132, 134, 136, the expansion valves 112, 122, and the

compressors

116, 118, 126, 128.

The cooling control module 109 may control the

fans

130, 132, 134, 136, the expansion valves 112, 122, and/or the

compressors

116, 118, 126, 128 based on signals from various sensors. For example, the sensors may include an ambient temperature sensor 150,

suction pressure sensors

152, 154, head pressure (head pressure)

sensors

156, 158, and/or compressor inlet (or evaporator outlet)

temperature sensors

160, 162. The ambient temperature sensor 150 may be an outdoor ambient temperature sensor and generates an ambient temperature signal T_A. The

suction pressure sensors

152, 154 generate suction pressure signals SUC1, SUC2 and detect the pressure of the fluid received by the

compressors

116, 118, 126, 128. The

discharge pressure sensors

156, 158 generate discharge pressure (or discharge pressure) signals HEAD1, HEAD2 and detect the pressure of the fluid exiting the

compressors

116, 118, 126, 128. The

temperature sensors

160, 162 detect the temperature of (i) the fluid downstream of the

evaporators

110, 120 and (ii) the fluid between the

evaporators

110, 120 and the

compressors

116, 118, 126, 128. Although not shown, pressure and/or temperature sensors may also be included to detect the pressure and/or temperature of (i) the fluid between the

condensers

114, 124 and the expansion valves 112, 122 and/or (ii) the fluid between the expansion valves 112, 122 and the

evaporators

110, 120.

The

evaporators

110, 120 may be Microchannel (MC) cooling coil assemblies, and/or include MC heat exchangers, and/or may be fin and tube (fin and tube) cooling coil assemblies. The expansion valves 112, 122 may be electronically based expansion valves (e.g., EEVs). The EEVs 112, 122 may be used to regulate the flow of refrigerant to the

evaporators

110, 120. This enables the cooling system 100 to be maintained at appropriate operating conditions for accurate temperature control, as well as providing rapid cooling and minimizing energy consumption. For example, suitable operating conditions may include maintaining a subcooling temperature oF the cooling system 100 (or out oF the condensers 114, 124) at a predetermined subcooling temperature (e.g., 5 ° f) and/or within a predetermined subcooling temperature range oF the predetermined subcooling temperature. The term "subcooling" as used herein may refer to a fluid that is present at a temperature below the normal saturation temperature of the fluid.

Each of the

condensers

114, 124 may be of various types, such as an air-cooled condenser, a water-cooled condenser, or a glycol-cooled condenser. The

condensers

114, 124 may include a heat rejection device that transfers heat from the return fluid to a cooling medium, such as outside air. The heat rejection means may comprise an air-cooled heat exchanger or a liquid-cooled heat exchanger.

In each of the

circuits

104, 108, a cooling fluid (refrigerant) is circulated through a

respective compressor pair

116, 118, 126, 128. Fluid flows from the

compressors

116, 118, 126, 128, through the

condensers

114, 124, the expansion valves 112, 122, and the

evaporators

110, 120, and back to the

compressors

116, 118, 126, 128. The

evaporators

110, 120 may be arranged in stages such that air flows in series first through the upstream evaporator 110 and then through the downstream evaporator 120. By having multiple cooling stages arranged for the serial air flow, the temperature difference across the

evaporators

110, 120 is reduced. This in turn enables the

evaporators

110, 120 to operate at different pressure levels and enables the pressure differential between the evaporator 110 and the condenser 114 and the pressure differential between the evaporator 120 and the condenser 124 to be reduced.

Since the compressor power is a function of the pressure difference between the evaporator and the condenser, a low pressure difference is more energy efficient. Each of the cooling

circuits

104, 108 may include a series (tandem) compressor (e.g.,

compressor

116, 118 or compressor 126, 128) pair. Each of the compressors in series may be a fixed capacity scroll compressor (e.g., compressors 116, 126) or a variable capacity scroll compressor (e.g., compressors 118, 128). The fixed capacity scroll compressor may be activated (on) and deactivated (off) based on a control signal generated by the cooling control module 109. The variable capacity scroll compressor may be controlled via corresponding digital signals received from the cooling control module 109.

Each of the cooling

circuits

104, 108 may include a series bank of compressors. Each of the series groups may include two compressors of equal volumetric displacement. The first compressor may be a digital Pulse Width Modulation (PWM) scroll compressor that receives a PWM percentage signal to control the rate and capacity of the first compressor. The second compressor may be a fixed speed scroll compressor with simple on/off capacity control. The suction and discharge conduits of the two compressors may be piped in parallel to form a series group. As an example, the

compressors

116, 126 may be PWM scroll compressors, and the

compressors

118, 128 may be fixed speed scroll compressors. In addition to receiving the PWM signal from the cooling control module 109, the fixed speed scroll compressor may receive an on/off control signal.

The series compressor configuration enables energy efficient temperature control by providing a wide range of capacity modulation to the cooling circuit of the air conditioning system. By having the digital PWM scroll compressor activated before the fixed speed scroll compressor, the series bank provides an energy efficient configuration when the compressor is on. This effectively enables the series group to provide a reduced volumetric displacement/capacity for partial displacement operation until additional capacity is required by the fixed scroll compressor.

Referring also to FIG. 3, a superheat setpoint adjustment system 200 is shown. The superheat setpoint adjustment system 200 includes a cooling control module 109 and a cooling circuit 202 (e.g., one of the cooling

circuits

104, 108 of fig. 2). The cooling control module 109 includes an instability module 204, a compressor discharge module 206, a set point module 208, a summer 210, a PID control module 212, an Expansion Valve (EV) module 214, a saturation module 216, and a superheat module 218. The instability module 204 determines whether an unstable superheat condition exists based on the superheat SET point SET and the superheat signal SH, which includes a superheat value. The superheat setpoint SET is a target superheat value. The superheat value SH indicates a level of superheat of a compressor (e.g., one of the

compressors

116, 118, 126, 128) of the cooling circuit 202. The instability module 204 generates an instability signal INST that indicates whether an unstable condition exists. The instability signal may be a digital signal. The determination of the unstable overheat condition is further described below with respect to fig. 4 and 5.

The compressor discharge module 206 determines whether the discharge pressure of the compressor exceeds a first predetermined pressure PredPres₁. The compressor discharge module 206 may compare a discharge signal CompDIS received from a discharge sensor (e.g., one of the sensors 152, 158) and generate a discharge comparison signal DC. Predetermined pressure PredPres₁May be accessed from a memory 220 that stores predetermined pressures and thresholds 222.

The setpoint module 208 generates a superheat setpoint signal SET based on the instability signal INST and the exhaust signal DC. The SET point module 208 may generate the superheat SET point signal SET based on, for example, the first adjustment table 223. An example of an adjustment table is provided as table 1.

TABLE 1 Regulation Table

Summer 210 subtracts superheat signal SH from superheat setpoint SET to generate ERROR signal ERROR₁. The PID control module 212 provides control of the position of an EV 224 (e.g., one of the EVs 112, 122) of the cooling circuit 202. PID control module 212 bases on ERROR signal ERROR₁CONTROL signal CONTROL is generated to CONTROL the position of EV 224. The PID control module 212 may have tuning parameters such as PID gains that may be used to determine PID values for EV control. The EV module 214 generates an EV signal to adjust the position of the EV 224 based on the CONTROL signal CONTROL. EV 224 is an electronically controlled expansion valve.

The superheat module 218 receives sensor signals from sensors 226 (e.g.,

sensors

154, 156, 160, 162) of the cooling circuit 202 and/or the saturation temperature SatTemp from the saturation module 216. The sensor signals may include a suction pressure signal SucPres and a compressor inlet temperature signal CompINTemp. The saturation module 216 determines a saturation temperature SatTemp of the compressor based on the suction pressure signal SucPres. The superheat module 218 may include a second summer 230, and the second summer 230 may subtract the saturation temperature SatTemp from the compressor inlet temperature CompINTemp to generate the superheat signal SH.

Referring also to FIG. 4, a portion of the cooling control module 109 is shown. The cooling control module 109 includes an instability module 204, a set point module 208, and a memory 220. The unstable module 204 distinguishes unstable behavior from stable behavior. The instability signal may exhibit periodic oscillations having a magnitude greater than a predetermined threshold and/or set point. The instability module 204 includes an error module 240, a comparison module 242, a zero crossing counter 244, a zero crossing module 246, a boundary touching counter 248, a boundary touching module 250, and an evaluation module 252.

The ERROR module 240 receives the superheat signal SH and the superheat SET point signal SET and may generate a second ERROR signal ERROR₂. Second ERROR signal ERROR₂Is generated based on the difference between the superheat signal SH and the SET point signal SET. For example, the error signal may be a sinusoidal signal. The difference between the superheat signal SH and the SET point signal SET (or the first ERROR signal ERROR)₁) May be integrated and normalized over time based on a moving window as described further below.

To detect an unstable overheat condition, the ERROR module 240 may apply the first ERROR signal ERROR based on a moving window₁Is integrated over time to generate a second ERROR signal ERROR₂. A moving window may be used to limit the integration to provide the second ERROR signal ERROR₂The amount of data history. The moving window may include a predetermined number of first ERROR signals ERROR₁The sinusoidal period of (c). The integral may be determined using, for example, equation 1, where t is time and WindowSize is the size of the moving window.

The moving window may have a predetermined size, which may be stored in the memory 220 and accessed by the error module 240. Second ERROR signal ERROR₂May be equal to the magnitude a multiplied by WindowSize multiplied by 2/pi. In order to provide a moving window and to implement the first ERROR signal ERROR₁The error module 240 may include a timer 254, the timer 254 being incremented to a value equal to the size of the window WindowSize.

Second ERROR signal ERROR₂Normalization can be performed relative to a baseline. The baseline may include the size of the moving window and a predetermined oscillation amplitude a. The predetermined oscillation amplitude a refers to the amplitude of the peaks and troughs of the sinusoidal period of the sinusoidal baseline signal. The predetermined oscillation amplitude a is determined as the maximum amplitude for stable oscillation and system operation. At the first ERROR signal ERROR₁Having an amplitude greater than a predetermined amplitude A and/or a second ERROR signal ERROR₂Above a predetermined threshold, an unstable condition may exist.

The comparison module 242 outputs the second ERROR signal ERROR₂And a first predetermined threshold value PredTor₁A comparison is made and an error comparison signal EC is generated. The ERROR comparison signal EC indicates the second ERROR signal ERROR₂Whether greater than a first predetermined threshold PredTor₁。

The zero-crossing counter 244 receives the superheat signal SH and the superheat SET point signal SET, and causes the first Count value Count to be SET if the superheat signal SH is equal to the superheat SET point signal SET₁And (4) increasing. The zero crossing module 246 determines the first Count value Count₁Whether or not it is greater than a second predetermined threshold PredTor₂. The zero crossing module 246 generates a zero crossing comparison signal ZC to indicate when the first Count value Count is₁Greater than a second predetermined threshold value PredTor₂. Second predetermined threshold PredTor₂May be normalized with respect to a second baseline determined by moving the window size WindowSize and the period of oscillation. Second predetermined threshold PredTor₂May be set to a value equal to, for example, 1 or within a predetermined range of 1.

The BOUNDARY touching counter 248 receives the overheat signal SH and compares the overheat signal SH with a predetermined range limit and/or a predetermined value BOUNDARY (hereinafter referred to as a BOUNDARY value BOUNDARY). In the case where the overheat signal SH is greater than the predetermined value BOUNDARY, the BOUNDARY touching counter 248 makes the second Count value Count₂And (4) increasing. The boundary touching module 250 counts the second Count value₂And a third predetermined threshold value PredTHr₃A comparison is made and a boundary comparison signal BC is generated. The boundary touching module 250 generates a boundary comparison signal BC to indicate when the second Count value Count₂Greater than a third predetermined threshold PredTor₃. A third predetermined threshold PredTohr may be paired with respect to a third baseline determined by the moving window size WindowSize and the oscillation period₃And (6) carrying out normalization. Third predetermined threshold PredTor₃May be set to a value equal to 1 or within a predetermined range of 1.

The modules 240 through 252 are used to eliminate false positives and false negatives of whether an unstable overheat condition exists. Reporting of an unstable condition via the evaluation module 252 is prevented by normalizing and integrating the error signal, normalizing and determining the number of zero crossings, and by normalizing and determining the number of times the overheating exceeds a predetermined boundary.

The evaluation module 252 generates an instability signal INST based on the comparison signals EC, ZC, BC. The instability signal INST may indicate that an unstable condition exists, for example, if both EC and ZC are true. The instability signal INST indicates that an instability condition exists that triggers an increase or decrease in the superheat setpoint signal SET (or superheat setpoint). The change in the superheat setpoint signal SET may be based on the comparison signals EC, ZC, BC. The operation of the superheat setpoint adjustment system 200 and the instability module 204 of fig. 3 and 4 are further described with reference to the method of fig. 5.

The superheat setpoint adjustment system 200 may operate using a number of methods, with the method of fig. 5 providing an example method. In FIG. 5, a logic flow diagram illustrating a superheat setpoint adjustment method is shown. The method may begin at 300. Although the following tasks are described primarily with reference to the implementations of fig. 2-4, the tasks may be readily modified to apply to other implementations of the present disclosure. The tasks may be performed iteratively.

At 302, the timer 254 may be started or reset. The timer 254 may be started and/or reset after each execution of the tasks 332-346.

At 304, the error module 240 determines a superheat value based on the superheat signal SH. At 305, the superheat value for the current timestamp indicated by the timer is stored in memory 220.

At 307, the instability module 204 determines whether the timer 254 is equal to WindowSize. Task 308 is performed if timer 254 equals WindowSize, otherwise task 324 is performed.

At 308, the ERROR module 240 generates an ERROR signal (e.g., a first ERROR signal ERROR) based on the superheat value and the superheat setpoint stored during tasks 304-307₁). First ERROR signal ERROR₁The value of (d) may be generated by determining a difference between each of the superheat values and a superheat setpoint. The ERROR signal is integrated and normalized over a moving window as described above to generate a second ERROR signal ERROR₂。

At 309, the zero crossing (or first) Count is calculated and normalized within the moving window as described above₁. At 310, a boundary Count (or second) Count is computed and normalized as described above₂。

At 312, the comparison module 242 determines the second ERROR signal ERROR₂Whether greater than a first predetermined threshold PredTor₁And generates an error (or first) comparison signal EC. At the second ERROR signal ERROR₂Greater than a first predetermined threshold value PredTor₁Task 314 may be performed, otherwise task 316 may be performed.

At 314, the zero crossing module 246 determines a first Count₁Whether or not it is greater than a second predetermined threshold PredTor₂And generates a zero-crossing (or second) comparison signal ZC. The comparison is performed in a steady state to prevent the first ERROR signal ERROR₁Integration "end (winding up)" of (1). The zero crossing counter 246 is used to count the number of times the superheat signal SH crosses the superheat setpointA second detection criterion for counting. If the first Count is₁Greater than a second predetermined threshold value PredTor₂Then task 318 is performed, otherwise task 316 is performed.

At 316, the boundary touching module 250 determines a second Count₂Whether greater than a third predetermined threshold PredTor₃And generates a boundary comparison signal BC. If the second Count is₂Greater than a third predetermined threshold PredTor₃Then task 318 is performed, otherwise task 320 is performed.

At 318, the evaluation module 252 may indicate that an unstable overheat condition exists based on the comparison signals EC, ZC, BC. This may be indicated via the instability signal INST. In the event that either task 314 or task 326 is true, an unstable condition exists. At 320, the evaluation module 252 may indicate that a stable over-temperature condition exists based on the comparison signals EC, ZC, BC. This may be indicated via the instability signal INST. In the case where task 316 is false, a stable condition exists. After

tasks

318 and 320,

tasks

322 and 332 are performed.

At 322, the timer is decremented, the first superheat value associated with the first timestamp of the moving window is dropped and/or deleted, the remaining superheat values are advanced, and the Count is reset₁、Count₂. This allows the updated superheat value to be determined during subsequent iterations of task 304. During subsequent iterations of tasks 304-305, an updated superheat value is determined and stored as the last superheat value in memory 220. The newly stored superheat value is then used in performing subsequent iterations of task 308.

Tasks

304, 305, 307, 322, and 324 provide a moving window for storing the latest predetermined number of superheat values.

As an example, during tasks 304-307 and 324, a predetermined number of overheat values indicated by the size of the moving window may be stored at addresses of memory 220 beginning at the first address and ending at the last address. Where the remaining superheat values advance forward, a first pointer associated with a first timestamp of the moving window may be shifted from a first address (associated with the falling superheat value) to a second address. The second superheat value is previously stored at the second address. A last pointer associated with a last timestamp of the moving window and previously pointing to a last address (associated with a last previously stored superheat value) may be shifted to an address subsequent to the last address or to a first address. This shifts each of the superheat values and causes the updated superheat value to be stored at a subsequent address or to overwrite the first superheat value at the first address.

Task 324 is performed after task 322. At 324, a timer is incremented. Timer 254 may be incremented for each iteration of tasks 304-307.

The following tasks 326 to 330 may be executed in parallel with the tasks 302 to 324. At 326, the boundary touching counter 248 determines a discharge pressure of the compressor (e.g., one of the

compressors

116, 118, 126, 128). At 328, the boundary reach counter 248 determines whether the discharge pressure CompDIS is greater than the predetermined pressure PredPres₂. At discharge pressure CompDIS greater than predetermined pressure PredPres₂Otherwise, task 332 is performed.

At 330, the boundary touching counter 248 may indicate that the discharge pressure (or discharge pressure) is a high discharge pressure. This may be accomplished by setting a high discharge flag, for example, in memory 220.

At 332, the setpoint module 208 determines whether the instability signal INST has been generated. Tasks 326 through 330 may be completed before tasks 302 through 324 are completed. Task 332 causes the superheat setpoint SET to be adjusted as follows: (i) the discharge pressure CompDIS is not less than or equal to the second predetermined pressure PredPres₂(ii) a (ii) Tasks 326 through 330 are completed before tasks 302 through 324. Task 334 is performed if the instability signal INST is not generated and/or received by the setpoint module 208, otherwise task 338 is performed.

At 334, the setpoint module 208 may determine whether the discharge pressure CompDIS is less than or equal to a second predetermined pressure PredPres₂. At a discharge pressure CompDIS less than or equal to a second predetermined pressure PredPres₂Task 336 is performed otherwise task 342 is performed. At 336, the setpoint module 208 may maintain (or avoid changing) the superheat setpoint SET.

At 338, the setpoint module 208 determines whether a stable condition exists and whether the discharge pressure CompDIS is less than or equal to the second predetermined pressure PredPres based on the results of tasks 312-316₂. If a stable condition exists and the discharge pressure CompDIS is less than or equal to the second predetermined pressure PredPres₂. Then task 336 is performed, otherwise task 340 is performed.

At 340, the setpoint module 208 determines whether a stable condition exists and whether the discharge pressure CompDIS is greater than the second predetermined pressure PredPres based on the results of tasks 312-316₂. If true, then task 342 is performed, otherwise task 344 is performed.

At 342, the setpoint module 208 may decrease the superheat setpoint SET. The SET point module 208 may determine an amount to decrease the superheat SET point SET. The amount of reduction may be based on the second ERROR signal ERROR₂Discharge pressure CompDIS, counter value Count₁、Count₂The results of

tasks

312, 314, 316, and/or 318, the instability signal INST, and/or other suitable parameters and/or information. The SET point module 208 may then lower the superheat SET point SET accordingly.

At 344, the setpoint module 208 determines whether an unstable condition exists and whether the discharge pressure CompDIS is less than or equal to the second predetermined pressure PredPres based on the results of tasks 312-316₂. If true, then task 346 is performed, otherwise task 342 is performed.

At 346, the SET point module 208 may increase the superheat SET point SET. The SET point module 208 may determine an amount to increase the superheat SET point SET. The amount of the increase may be based on the second ERROR signal ERROR₂Discharge pressure CompDIS, counter value Count₁、Count₂The results of

tasks

312, 314, 316, and/or 318, the instability signal INST, and/or other suitable parameters and/or information. The SET point module 208 may then increase the superheat SET point SET accordingly.

At 348, the instability module clears the over-temperature data stored in memory and resets the Count value Count₁、Count₂. Clearing the overheating data includes deleting the data during tasks 304, 305The superheat value of the intermediate storage. Task 302 may be performed after task 348.

The SET point management provided by the above task is used to adjust the superheat SET point SET such that the superheat condition of the compressor is stabilized against the updated superheat SET point SET. This improves the robustness and reliability of the system operation.

The cooling system may operate in a variety of different environments and subject to a variety of different operating conditions. For example, some portions oF the cooling system may be subjected to indoor temperatures oF 60 to 105 ° f, and other portions oF the cooling system may be subjected to outdoor temperatures oF-30 to 105 ° f. As an example, the evaporator of the cooling system may be located indoors and the condenser of the cooling system may be located outdoors. Traditionally, the superheat value of the compressor is controlled to match a constant superheat set point to ensure compressor safety and improve system efficiency. However, maintaining the superheat value at a constant superheat setpoint value can result in poor refrigerant charge management of the compressor and cause unstable system operation due to various operating conditions.

Examples described below include determining whether to adjust a superheat setpoint to manage refrigerant charge between an indoor tube coil (e.g., evaporator) and an outdoor tube coil (e.g., condenser) for stable operation. The superheat setpoint is maintained and/or adjusted based on operating conditions and predetermined and/or initial values. The superheat setpoint is suitably set for each of the operating conditions to provide a loading balance between the indoor and outdoor tube trays to stabilize the superheat value and indirectly maintain the predetermined subcooling level.

FIG. 6 illustrates a superheat setpoint adjustment system 350 including the cooling control module 109' and the cooling circuit 202. The cooling control module 109' may replace the cooling control module 109 of fig. 2. Although shown as a different module than the cooling control module 109 of fig. 3, the cooling control module 109' may be the cooling control module 109. In other words, a single cooling control module may provide both the stabilization feature of the cooling control module 109 of fig. 3 and the instability prevention feature of the cooling control module 109' of fig. 6. If an unstable condition, as determined by, for example, the method of FIG. 5, exists, the superheat setpoint control provided by the (override) superheat setpoint adjustment system 350 and the corresponding superheat setpoint adjustment method of FIG. 7 may be skipped. If an unstable condition exists, the superheat SET point, SET, may be controlled via the method of fig. 5 rather than based on the method of fig. 7. If an unstable condition does not exist, the method of FIG. 7 may be performed. Thus, if an unstable condition is detected, the cooling control module may perform both the method of FIG. 5 and the method of FIG. 7, and may skip the method of FIG. 7 and adjust the superheat setpoint based on the method of FIG. 5.

The cooling control module 109 'includes a compressor discharge module 206, a set point module 208', a summer 210, a PID control module 212, an Expansion Valve (EV) module 214, a saturation module 216, a superheat module 218, a memory 220, and a mode selection module 351. The setpoint module 208' includes a second adjustment table 352. The second adjustment table 352 may include the first adjustment table 223 of fig. 3 and/or may be used to determine the superheat setpoint SET based on an input provided to the setpoint module 208'. The inputs are shown in fig. 6 and described below.

The memory stores predetermined pressure and threshold values 222, predetermined temperatures 354, and predetermined initial SH set point values 356. The predetermined temperature 354 and the predetermined initial SH set point value 356 may be provided via the user interface 329 of fig. 2 and/or may be predetermined and stored in the memory 220. Different predetermined temperatures and/or predetermined initial SH set point values may be stored in memory 220 for: different types of cooling systems; cooling systems having different types of components (e.g., different types of condensers, evaporators, expansion valves, compressors, etc.); and/or different cooling system configurations.

The mode selection module may select a particular mode of operation. These modes of operation are described below with respect to the method of fig. 7. The cooling circuit 202 includes an expansion valve 224 and a sensor 226. The operation of the modules and devices of the cooling control module 109' are further described below with respect to the method of FIG. 7.

FIG. 7 illustrates a superheat setpoint adjustment method. Although the following tasks are primarily described with respect to the implementations of fig. 6-7, the tasks may be readily modified to apply to other implementations of the present disclosure. The tasks may be performed iteratively.

The method may begin at 400. At 402, suction pressure SucPres, compressor inlet temperature Completemp, outdoor ambient temperature T are measured and/or determined_AAnd compressor discharge pressure CompDis. These temperatures and pressures may be detected and/or determined as described above.

At 404, saturation module 216 determines saturation temperature SatTemp based on suction pressure SucPres, as described above. At 406, the superheat module 218 determines an actual superheat value SH, which is determined based on the saturation temperature SatTemp and the compressor inlet temperature CompINTemp.

The following tasks 408-416 may be performed before the tasks 404-406, during the tasks 404-406, and/or after the tasks 404-406. At 408, the compressor discharge module 206 compares the compressor discharge pressure CompDis to a first predetermined pressure PredPres₁Compares to generate a discharge comparison signal DC indicative of the compressor discharge pressure CompDis to a first predetermined pressure PredPres₁The difference between them.

The following task 410 may be performed before task 408, during task 408, and/or after task 408. At 410, the mode selection module 351 may select operation in, for example, a first mode, a second mode, a third mode, or a fourth mode. The selection may be based on user input of the user interface 329. The user may select operation in the first mode, the second mode, the third mode, or the fourth mode. The selection may be based on whether the return air temperature set point T is provided and stored in memory 220_RASETOr supply air temperature setpoint T_SASET. Return air temperature setpoint T_RASETRefers to the predetermined temperature of the air returned to (or supplied to) the evaporator. Supply air temperature setpoint T_SASETRefers to the predetermined temperature of the air exiting the evaporator (and/or cooling system). These set points may be set by a user via the user interface 329 of fig. 2, or may be predetermined set points stored in the memory 220. The predetermined temperature 354 includes these set points. Mode selection module 351 generates a mode signal MOD indicating the selected modeE。

The first mode may refer to the use of a first indoor conditioning factor adslid 1 and an outdoor conditioning factor adsood. The second mode may refer to the use of an outdoor conditioning factor adshood and a second indoor conditioning factor AdSHid 2. The first mode may not include the use of the second indoor adjustment factor AdSHid 2. The second mode may not include using the first indoor adjustment factor AdSHid 1. The third mode may refer to the use of all of the adjustment factors adslid 1, adslid 2. The fourth mode may refer to avoiding adjusting the superheat setpoint SET. This may be skipped (override) by the method of fig. 5, although the fourth mode may be selected.

The adjustment factors adslid 1, adsood, adslid 2 may be predetermined default values used at 416 to adjust the superheat setpoint SET. The adjustment factors adslid 1, adsood, adslid 2 may be set based on the settings of the cooling system to which the factors are applied and/or the operating conditions under which the cooling system is used. Each different type of cooling system may have a different value for the adjustment factors adslid 1, adsood, adslid 2. In mode 3, the indoor adjustment factors AdSHid1 and AdSHid2 may be weighted to provide the resulting indoor adjustment factors. Weighting the factors may include multiplying the factors by a weight (or a value greater than or equal to 0 and less than or equal to 1) and summing the weighted factors to provide a resulting indoor adjustment factor.

At 412, the SET point module 208' determines whether to adjust the superheat SET point SET. The determination may be based on, for example, the MODE signal MODE, the emissions comparison signal DC, and/or other parameters. As an example, the superheat SET point SET may be adjusted while operating in one of modes 1-3, and may not be adjusted while operating in mode 4. As another example, if the emissions comparison signal DC is greater than a predetermined value, raising and/or adjusting the superheat setpoint SET may be disabled. This causes the superheat setpoint to be lowered and/or maintained at the current superheat setpoint. If no adjustment is made to the superheat setpoint, task 414 may be performed. If an adjustment is to be made to the superheat setpoint, then task 416 may be performed. If the superheat setpoint is allowed to decrease but not to increase, then the passing target may be used aloneThe selected mode uses resulting values provided by adjustment of two or more of the factors adslid 1, adslid 2 to adjust the superheat SET point SET if the sum of the resulting values is negative. The resulting values may be the corresponding terms in equations 2 through 7 provided below. As an example, a corresponding entry for AdSHId1 may be AdSHId1^*(T_RASET-T₁). The parameters of the respective items are defined and described below.

At 414, the SET point module 208' maintains the superheat SET point SET at the current value. At 416, the SET point module 208' adjusts the superheat SET point SET. The superheat setpoint SET may be adjusted according to any of equations 2 to 4. The selection of one of the equations 2 to 4 may be based on the MODE signal MODE, where SH_INITIs the initial superheat set point. Initial superheat setpoint SH_INITMay be a predetermined initial SH value 356 stored in the memory 220. For example, if operating in mode 1, equation 2 may be selected. If operating in mode 2, equation 3 may be selected. If operating in mode 3, equation 4 may be selected.

SET＝SH_INIT+AdSHid1*(T_RASET-T₁)+AdSHod*(T₂-T_A) (2)

SET＝SH_INIT+AdSHid2＊(T_RASET-T₃)+AdSHod＊(T₂-T_A) (3)

The indoor conditioning factor AdSHId1 is based on the return air temperature setpoint T_RASETAnd a first predetermined temperature T₁(e.g., 75 ° F). The outdoor regulation factor AdSHod is based on the outdoor ambient temperature T_AAnd a second predetermined temperature T₂(e.g., 95 ° F). The indoor conditioning factor AdSHId2 is based on the supply air temperature setpoint T_SASETAnd a third predetermined temperature T₃(e.g., 55F) to adjust. In equation 4, the indoor adjustment factors AdSHId1 and AdSHId2 are determined by the weight W₁、W₂To be adjusted.

The adjustment factors adslid 1, adslid 2 may be set to predetermined default values and/or may be based on the type and/or setting of the cooling system to which the adjustment factors adslid 1, adslid 2 are applied. As an example, the default values of the adjustment factors adslid 1, adslid 2 may be 0.3, 0.13, 0.3, respectively. The default value of the second indoor adjustment factor AdSHid2 may be different from the default value of the first indoor adjustment factor AdSHid 1. Predetermined temperature T₁、T₂、T₃May be set to a predetermined baseline value, and/or may be based on a predetermined temperature T₁、T₂、T₃The type and/or setting of the cooling system being used. If the temperature T is_RASET、T_A、T_SASETAre respectively equal to a predetermined temperature T₁、T₂、T₃The superheat setpoint SET is then equal to the initial superheat setpoint SH_INIT。

Outdoor ambient temperature T_AMay be averaged over a predetermined period of time (e.g., 5 minutes) to provide an average temperature. The average may be determined by a set point module 208 'or a temperature module (not shown) within the cooling control module 109'. The average temperature being the outdoor ambient temperature T_AAn average of a plurality of readings (iteratively determined) over a predetermined period of time. The average temperature may be used instead of the outdoor ambient temperature T in equations 2 to 4 and/or equations 5 to 7 provided below_A. This provides system stability by preventing changes in the superheat SET point SET due to brief, sustained fluctuations in the outdoor ambient temperature. Outdoor ambient temperature may fluctuate due to, for example, wind gusts and/or other outdoor environmental elements. If the average outdoor ambient temperature is not determined and/or the outdoor ambient temperature is not determined within a predetermined period of time (e.g., during startup of the cooling system), then there may be no adshood^*(T₂-T_A) In the case of items, the superheat setpoint SET is calculated. Accordingly, one of equations 5 to 7 may be used instead of one of equations 2 to 4, respectively.

SET＝SH_INIT+AdSHid1＊(T_RASET-T₁) (5)

SET＝SH_INIT+AdSHid2＊(T_RASET-T₃) (6)

SET＝SH_INIT+[W₁＊AdSHid1＊(T_RASET-T₁)]+[W₂＊AdSHid2*(T_RASET-T₃)] (7)

In one embodiment, if the outdoor ambient temperature T_ALess than or equal to a predetermined temperature (e.g., 50F), the outdoor ambient temperature T is set for purposes of equations 2 through 4_AIs set at a predetermined temperature (e.g., 50F). This is because at temperatures below the predetermined temperature, the outdoor ambient temperature of 50 ° F has minimal or no effect on subcooling. At temperatures below the predetermined temperature, the cooling fluid volume inside the respective evaporator and inside the respective condenser may not change. For this reason, no superheat SET adjustment may be performed since a predetermined amount of subcooling is maintained without adjusting the superheat SET at these temperatures. At a temperature below the predetermined temperature, the discharge comparison signal DC may be maintained at a constant set point.

If the outdoor ambient temperature is not provided due to, for example, the outdoor ambient temperature sensor 150 being disconnected or a signal from the outdoor ambient temperature sensor 150 being lost, the previous outdoor ambient temperature (the previously determined T) may be used_A) As the current outdoor ambient temperature. The previous outdoor ambient temperature may be used if the outdoor ambient temperature or a corresponding sensor signal from the outdoor ambient temperature sensor 150 is not provided for less than a predetermined period of time (e.g., 1 to 2 seconds). In the event that the voltage of the outdoor ambient temperature signal drops more than a predetermined amount and/or is negative, the cooling control module 109' may detect a loss of the outdoor ambient temperature signal. This prevents the overheating SET point SET from being improperly adjusted due to the loss of the outdoor ambient temperature signal.

After tasks 406, 414, and/or 416, task 418 is performed. At 418, the summer 210 generates a first ERROR signal ERROR based on the superheat setpoint SET provided by the setpoint module 208' and the superheat level SH provided by the superheat module 218₁. The superheat setpoint SET may be the current superheat setpoint provided at 414 or atThe updated superheat setpoint at 416. After performing task 416, the updated superheat setpoint becomes the current superheat setpoint.

At 420, the PID control module 212 bases the first ERROR signal ERROR₁The CONTROL signal CONTROL is generated. At 422, the EV module 214 generates an EV signal to adjust the state of the expansion valve 224 based on the CONTROL signal CONTROL.

The above-described method of fig. 7 provides robust superheat detection and automatic schedule maintenance and/or adjustment to superheat set points. By adjusting the superheat setpoint SET and controlling the state of the expansion valve 224 based on the adjusted superheat setpoint SET, the expansion valve 224 reacts to manage the flow of coolant (or cooling fluid) between the evaporator (e.g., one of the

evaporators

110, 120 of fig. 2) and the condenser (e.g., one of the

condensers

114, 124 of fig. 2) for system load balancing. This allows subcooling to be maintained and/or a predetermined level of subcooling to be maintained at the inlet of the expansion valve 224.

The method maintains the level of subcooling without the use of a pressure sensor and/or a temperature sensor for measuring the pressure exiting the condenser and/or the temperature of the refrigerant (or fluid) exiting the condenser.

The above-described tasks of fig. 5 and 7 are intended to be illustrative examples; the tasks may be performed sequentially, synchronously, simultaneously, continuously, in overlapping periods or in a different order depending on the application. Further, depending on the implementation and/or order of events, none of the tasks may be performed or skipped.

The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. As used herein, at least one of the phrases A, B and C should be construed to mean logic (a OR B OR C) using a non-exclusive logic "OR" (OR), and should not be construed to mean "at least one of a, at least one of B, and at least one of C". It should be understood that one or more steps within a method may be performed in a different order (or simultaneously) without altering the principles of the present disclosure.

In this application, including the following definitions, the term "module" or the term "controller" may be replaced by the term "circuit". The term "module" may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); digital circuits, analog circuits, or hybrid analog/digital discrete circuits; digital circuits, analog circuits, or hybrid analog/digital integrated circuits; a combinational logic circuit; a Field Programmable Gate Array (FPGA); processor circuitry (shared, dedicated, or group) that executes code; memory circuitry (shared, dedicated, or group) that stores code executed by the processor circuitry; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, for example in a system on a chip.

A module may include one or more interface circuits. In some examples, the interface circuit may include a wired interface or a wireless interface to connect to a Local Area Network (LAN), the internet, a Wide Area Network (WAN), or a combination thereof. The functionality of any given module of the present disclosure may be distributed among a plurality of modules connected via interface circuits. For example, multiple modules may allow load balancing. In yet another example, a server (also referred to as remote or cloud) module may implement some functionality on behalf of a client module.

The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, data structures, and/or objects. The term shared processor circuit encompasses a single processor circuit that executes some or all code from multiple modules. The term group processor circuit encompasses a processor circuit that executes some or all code from one or more modules in conjunction with another processor circuit. The multiple processor circuits referred to encompass multiple processor circuits on separate dies, multiple processor circuits on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination thereof. The term shared memory circuit encompasses a single memory circuit that stores some or all code from multiple modules. The term group memory circuit encompasses memory circuits that store some or all code from one or more modules in combination with additional memory.

The term memory circuit is a subset of the term computer readable medium. The term computer-readable medium as used herein does not encompass transitory electrical or electromagnetic signals propagating through a medium (e.g., on a carrier wave); the term computer readable medium may therefore be considered tangible and non-transitory. Non-limiting examples of non-transitory, tangible computer readable media are: non-volatile memory circuitry (e.g., flash memory circuitry, erasable programmable read only memory circuitry, or mask read only memory circuitry); volatile memory circuitry (e.g., static random access memory circuitry or dynamic random access memory circuitry); magnetic storage media (e.g., analog or digital tape or hard disk drive); and an optical storage medium (e.g., a CD, DVD, or blu-ray disc).

The apparatus and methods described in this application may be partially or wholly implemented by a special purpose computer, which is generated by configuring a general purpose computer to perform one or more specific functions included in a computer program. The functional blocks and flowchart elements described above are used as software applications that can be converted into computer programs by a routine work of a technician or programmer.

The computer program includes processor-executable instructions stored in at least one non-transitory, tangible computer-readable medium. The computer program may also comprise or rely on stored data. The computer program may include: a basic input/output system (BIOS) that interacts with the hardware of the special purpose computer; a device driver to interact with a specific device of the special purpose computer; one or more operating systems; a user application; background services; background applications, and the like.

The computer program may include: (i) descriptive text to be parsed, such as HTML (hypertext markup language) or XML (extensible markup language); (ii) assembling the code; (iii) by a compilerObject code generated from source code; (iv) source code for execution by an interpreter; (v) source code for compilation and execution by a just-in-time compiler, and the like. By way of example only, source code may be written using syntax in a language including C, C + +, C #, target C, Haskell, Go, SQL, R, Lisp, etc,

Fortran、Perl、Pascal、Curl、OCaml、

HTML5, Ada, ASP (dynamic Server Page), PHP, Scala, Eiffel, Smalltalk, Erlang, Ruby, HawIth,

Visual

lua and

no element recited in the claims is intended to be a means plus function element within the meaning of 35u.s.c. § 112(f) unless the element is explicitly recited using the phrase "means for … …" or in the case of a method claim using the phrase "operation for … …" or "step for … …".

Claims

1. A system, comprising:

a set point module configured to indirectly control subcooling of a condenser by adjusting a superheat set point based on (i) a return air temperature set point or a supply air temperature set point and (ii) an outdoor ambient temperature;

a summer configured to determine an error between the superheat setpoint and a superheat level of the compressor;

a control module configured to generate a control signal based on the error; and

an expansion valve module configured to electronically control a state of an expansion valve based on the control signal,

wherein the setpoint module is configured to:

obtaining a plurality of adjustment factors for adjusting the superheat setpoint, wherein the plurality of adjustment factors are predetermined values selected based on one of a plurality of types of the system and one of a plurality of settings, and wherein the plurality of adjustment factors include a first indoor adjustment factor, a second indoor adjustment factor, and an outdoor adjustment factor,

selecting an operating mode from a plurality of operating modes, wherein the plurality of operating modes includes a first operating mode, a second operating mode, and a third operating mode, wherein when operating in each of the plurality of operating modes, the set point module calculates the superheat set point differently than when operating in other of the plurality of operating modes,

adjusting the superheat setpoint using the first indoor adjustment factor and the outdoor adjustment factor during the first mode of operation,

adjusting the superheat setpoint using the outdoor adjustment factor and the second indoor adjustment factor during the second mode of operation,

during the third mode of operation, adjusting the superheat setpoint using the first indoor adjustment factor, the second indoor adjustment factor, and the outdoor adjustment factor, an

Adjusting the superheat setpoint based on the selected operating mode.

2. The system of claim 1, wherein the setpoint module is configured to: adjusting the superheat setpoint based on an initial predetermined superheat level of the compressor.

3. The system of claim 2, wherein the setpoint module is configured to: adjusting the initial predetermined superheat level of the compressor based on (i) the return air temperature setpoint or the supply air temperature setpoint and (ii) the outdoor ambient temperature while determining the superheat setpoint.

4. The system of claim 1, wherein the setpoint module is configured to: adjusting the superheat setpoint based on (i) the return air temperature setpoint, (ii) the outdoor ambient temperature, and (iii) an initial predetermined superheat level for the compressor.

5. The system of claim 1, wherein the setpoint module is configured to: adjusting the superheat setpoint based on (i) the supply air temperature setpoint, (ii) the outdoor ambient temperature, and (iii) an initial predetermined superheat level for the compressor.

6. The system of claim 1, further comprising a mode selection module configured to select a mode of operation,

wherein the set point module is configured to adjust the superheat set point based on (i) the return air temperature set point or (ii) the supply air temperature set point, in accordance with the selected operating mode.

7. The system of claim 1, wherein the setpoint module is configured to: adjusting the superheat setpoint based on an iteratively determined average of the outdoor ambient temperature over a predetermined period of time.

8. The system of claim 1, wherein the setpoint module is configured to: (i) detecting loss of an outdoor ambient temperature signal; and (ii) refrain from changing the superheat setpoint based on the loss of the outdoor ambient temperature signal.

9. The system of claim 1, wherein:

the set point module is configured to avoid changing the superheat set point based on an emissions comparison signal; and is

The discharge comparison signal indicates a difference between a discharge pressure of the compressor and a predetermined pressure.

10. A method, comprising:

indirectly controlling subcooling of the condenser by adjusting a superheat setpoint based on (i) a return air temperature setpoint or a supply air temperature setpoint and (ii) an outdoor ambient temperature;

determining an error between the superheat setpoint and a superheat level of the compressor;

generating a control signal based on the error;

electronically controlling a state of an expansion valve based on the control signal;

obtaining a plurality of adjustment factors for adjusting the superheat setpoint, wherein the plurality of adjustment factors are predetermined values selected based on one of a plurality of types and one of a plurality of settings for the system, and wherein the plurality of adjustment factors include a first indoor adjustment factor, a second indoor adjustment factor, and an outdoor adjustment factor;

selecting an operating mode from a plurality of operating modes, wherein the plurality of operating modes includes a first operating mode, a second operating mode, and a third operating mode, wherein the superheat setpoint is calculated differently when operating in each of the plurality of operating modes than when operating in other of the plurality of operating modes;

during the first mode of operation, adjusting the superheat setpoint using the first indoor adjustment factor and the outdoor adjustment factor;

during the second mode of operation, adjusting the superheat setpoint using the outdoor adjustment factor and the second indoor adjustment factor;

during the third mode of operation, adjusting the superheat setpoint using the first indoor adjustment factor, the second indoor adjustment factor, and the outdoor adjustment factor; and

adjusting the superheat setpoint based on the selected operating mode.

11. The method of claim 10, comprising adjusting the superheat setpoint based on an initial predetermined superheat level of the compressor.

12. The method of claim 11, further comprising adjusting the initial predetermined superheat level of the compressor based on (i) the return air temperature setpoint or the supply air temperature setpoint and (ii) the outdoor ambient temperature while determining the superheat setpoint.

13. The method of claim 10, comprising: adjusting the superheat setpoint based on (i) the return air temperature setpoint, (ii) the outdoor ambient temperature, and (iii) an initial predetermined superheat level of the compressor.

14. The method of claim 10, comprising: adjusting the superheat setpoint based on (i) the supply air temperature setpoint, (ii) the outdoor ambient temperature, and (iii) an initial predetermined superheat level of the compressor.

15. The method of claim 10, further comprising:

selecting an operation mode; and

adjusting the superheat setpoint based on (i) the return air temperature setpoint or (ii) the supply air temperature setpoint, in accordance with the selected operating mode.

16. The method of claim 10, further comprising: adjusting the superheat setpoint based on an iteratively determined average of the outdoor ambient temperature over a predetermined period of time.

17. The method of claim 10, further comprising:

detecting loss of an outdoor ambient temperature signal; and

refraining from changing the superheat setpoint based on the loss of the outdoor ambient temperature signal.

18. The method of claim 10, further comprising: refraining from changing the superheat setpoint based on an emissions comparison signal,

wherein the discharge comparison signal indicates a difference between a discharge pressure of the compressor and a predetermined pressure.