JPS62216001A - Adjustment of capacity for temperature adjusting system and system control - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to capacity control of temperature regulating systems, and more particularly to controls that vary the capacity of the system to maintain a regulating fluid at a set point temperature. It further relates to a control that modulates the capacity when the operating parameters approach a limit that would cause the system to stall.

BACKGROUND OF THE INVENTION Systems for heating or cooling fluids to set point temperatures are well known in the art for process applications or for regulating comfort zones.

Such systems typically cause the system to bias when the fluid temperature deviates from the set point by more than a predetermined first increment in one direction; It has a control that disables the system if the increment is exceeded. The combined magnitude of these increments defines the control's "deadband" or range of deviation of fluid temperature from the set point, which is typically centered around the set point and within which This control does not change the capacity of the system (by activating or deactivating the system) in response to fluid temperature errors.

Large temperature control systems often have variable capacity to more effectively handle changing load conditions.

In such systems, the capacity of the refrigerant compressor can be increased by using multiple stages that are selectively unloaded or deactivated, i.e. by using variable speed compressors, or by using mostly centrifugal compressors. In most systems, adjustments are made by adjusting the inlet guide vanes on the compressor. The control of a variable capacity system to maintain the fluid at a set point temperature is of course more complex than the simple on-off scheme described above, but typical controls for variable capacity systems still Must have a deadband around the set point for stability. The deadband of that control is normal.
Carefully selected. A wider deadband prevents frequent changes in compressor capacity, while a narrower deadband provides more precise control of fluid temperature at the set point.

[Problem that the invention seeks to solve]

Choosing the width of the deadband is usually a compromise between accurate temperature regulation and stable operation of the system. Designers try to avoid the stage undergoing continuous on-off cycles, ie, adjust the capacity to maintain the fluid temperature at a set point. Additionally, he wants to ensure that the system does not jump beyond its set point when the load worsens. These problems are addressed in U.S. Pat.
5a 961, in which two deadbands are used in the control of a system with multiple heating and cooling stages.

The patent uses microprocessor control, and a first narrow deadband is used to control the on and off states of whichever stage is cycling. Ru. Once the regulated temperature exceeds the second wide deadband, the next stage (or previous stage) is controlled to keep the straw temperature within the first deadband. . 1
The control of a stage within one or the other dead band is independent of whether the deviation from the set point is an increase or decrease, but only on the magnitude of that deviation. Therefore, the second dead band essentially limits the temperature error at which the next stage should be energized, ie the previous stage should end. However, this method does not realistically solve the problem of reducing the stage period and minimizing set point jumps.

Almost all temperature regulation systems have some form of precaution to prevent major failures if operating parameters exceed safe limits. For example, in large systems, some circuit breakers may be used to shut down the system if various operating parameters exceed safety limits, such as circuit breakers that protect compressor drive motors against damage resulting from overload conditions. Normally, a limit switch is used. Unless there is an automatic reset, the system remains in place until manually reset by an operator. Under such load conditions, it is common for operating parameters to exceed their limits, causing the system to shut down. This can be very troublesome if, for example, on a very hot day, the air conditioning system shuts down due to overload when it is most needed. Conversely, problems can also arise when the system is lightly loaded and the outside air temperature is relatively moderate. Because under these conditions, the evaporator refrigerant temperature will drop rapidly once the system is energized, causing the evaporator refrigerant limit switch to move and cause the liquid being cooled in the evaporator to freeze. This is because it is designed to prevent In either case,
The system will normally shut down and no cooling will occur until the problem is corrected and the limit switches are reset. Conventional controls modulate the capacity of the system only to bring the regulating fluid to and hold it at a set point temperature. Those controls will not adjust the capacity to prevent limit switch movement. On very hot days, when the load exceeds the capacity of the system, a limit switch can reduce the operating parameters to such an extent that the system is deactivated to prevent damage. It is much preferable to operate the system continuously.

It is therefore an object of the present invention to maintain the fluid near the set point and
The goal is to provide controls that minimize capacity adjustments.

Another object of the invention is to provide a control with minimal set point dispersion.

Another objective of the invention is to achieve the set point as quickly as possible without tripping limit switches, which protects the system from major failures.

Yet another objective is to adjust system capacity to ensure that operating parameters do not exceed safe limits even if set point temperatures are not reached.

These and other objects of the invention will become apparent from the following description of the invention and the accompanying drawings.

[Means for solving problems]

The present invention is a capacity control for a system used to condition a fluid to a predetermined set point temperature, and a method for controlling the capacity of such a system. The system includes a temperature sensor responsive to the temperature of the regulating fluid and a first dead band.
) and means for selecting a first variable used to determine the width of the second relatively wide deadband. The system further includes apparatus for selecting a second variable that limits the gain setting of the control.

A control device is connected to and responsive to the temperature sensor and the first and second variable selection devices. The controller determines the widths of the first and second dead bands as a function of the first variable. The capacity of the system is adjusted by the controller to maintain the temperature of the conditioning fluid near the set point as a function of the gain setting. Further, the control device determines the deviation of the fluid from the set point. When the absolute value of the deviation increases, the control device uses the first dead band, and when the absolute value decreases, the control device uses the second dead band when adjusting the capacity.

Another feature of the invention is a control and method for adjusting the capacity of a system when operating parameters are near limits that lead to a protective shutdown of the system. Such shutdowns typically occur to prevent major system failures when operating parameters exceed limits.

The control has a device for sensing the state of the operating parameters and a device for selecting the 'JEt'.

A control device responsive to the sensing device and the selection device includes:
determine the deviation of the operating parameters from its limits,
If the deviation is greater than the deadband, the capacity of the system is adjusted according to a first predetermined function of the deviation, and if the deviation is less than or equal to the deadband, the capacity of the system is adjusted according to a second predetermined function of the deviation. Operating parameters using this control method include evaporator refrigerant temperature, condenser pressure, and line current.

〔Example〕

Referring to FIG. 1, a liquid cooling system controlled in accordance with the present invention is indicated generally at 10. The cooling system 10 provides cooling fluid (liquid in this example) to the building by supplying cooling fluid (liquid in this example) through a supply line 12a.
It is used to cool one or more comfort areas 11. After the cooling fluid is used to cool the air circulated to the comfort area 11, the fluid returns to the cooling system through line 12b.

The refrigeration system 10 includes a centrifugal compressor 13 used to compress the refrigerant fluid and a compressed refrigerant fluid connected to the line 1.
5 and a condenser 14 fed through the capacitor 5. 1 compressed refrigerant fluid in condenser 14 is transferred to line 17
a and 17b into the cooling tower 16, respectively;
It is condensed into a liquid by heat exchange with the flowing water. The condensed refrigerant fluid flows through line 18 to expansion device 19;
It then flows through line 20 to evaporation chamber 21 where the expanded refrigerant evaporates by exchanging heat with the liquid used to cool comfort area 11 in the building. The evaporated refrigerant fluid then returns through line 22 to compressor 13 to repeat the refrigerant cycle.

The operation of the cooling system 10 is primarily controlled by a unit controller 25 having the capacity modulation control of the present invention. The unit controller 25 may optionally be connected to the building's automatic system controller 26 through data and control lines 27 if control of the cooling system 10 is desired to be incorporated into the overall building control.

However, it should be noted that the building's automatic system controller 26 is not required since the unit controller 25 can control the cooling system 10 on its own. Unit controller 25 performs several functions, but only those relevant to the present invention will be described here.

Using the signal passed through control line 28, controller 25 energizes or de-energizes compressor 13 to vary the capacity of the refrigeration system. Yes, it connects to a number of sensors, and those sensors can adjust their capacity as a function of the variables they respond to.

These sensors include a residual cooling liquid temperature sensor 29 connected to the unit controller 25 through line 30, an evaporator refrigerant temperature sensor 35 connected through line 36, and a centrifugal temperature sensor 35 connected through line 36. A supply current sensor (transformer) 37 used to monitor the current supplied to the compressor drive motor (not shown) and connected to the unit controller 25 by a lead 39, and a capacitor connected to the unit controller 25 by a wire 41. There is a pressure sensor 40.

Referring now to FIG. 2, a block diagram shows that unit controller 25 includes a microprocessor 45 and a multiplexer 46. Both of these solid state devices are energized by current supplied from power supply 47 through electrical wires 48a, 48b, respectively. Additionally, an analog to digital converter 49 is used which converts whichever of the analog signals is selected by the multiplexer 46 and inputs it to the A-to-D converter 49 through the %l[50. is a digital data stream which is transmitted through data line 51 to microphone processor 45 by an A-to-D converter. A second wire 52 connects the A-to-D converter 49 to the microprocessor 45 and is used to control the A-to-digital conversion process. In the preferred embodiment, A-to-D converter 49 comprises a conventional R-2R register network well known in the art. This example uses other types of A
-D converters can also be used equally.

A number of analog signals are sent to multiplexer 46 as follows:
is input to. Wire 39 carries an analog signal proportional to the centrifugal compressor motor current flowing through wire 38, and f4 wire 55 is generated across a variable electrometer;
and provides an input representing the voltage level that the user adjusts to the cooling water set point. Similarly, the current limit set point is
The resulting analog signal selected by adjusting the variable pot is input to multiplexer 46 through wire 56; similarly, the analog signal representing the pressure set point of the capacitor is input through wire 57; An analog signal representing the evaporator refrigerant temperature set point is input through wire 58, and an analog signal representing the control gain setting is input through wire 59.
An analog signal representing a user-selected variable called the difference start set point is input through wire 6.
It is input through 0. Additionally, analog signals representing cooling water temperature, evaporator refrigerant temperature and condenser pressure are input by wires 30, 36, 41, respectively.

Another signal processed by multiplexer 46 is input from inlet guide vane drive 65 through fti$9161. This signal indicates when the inlet guide vanes are fully closed. The inlet guide vane drive block 65 has a two-way motor that drives the inlet guide vane between a fully open position and a fully closed position.
It is connected to allow movement in increments determined by microprocessor 45 according to a control algorithm. Inlet guide vanes 66 are conventional and well known in the art as an effective means of regulating centrifugal compressor capacity. The inlet guide vane drive block 65 also includes a logic level switched AC line voltage control member (e.g. TRIAC).
, which is connected to the microprocessor 45 by a control signal line 67.

A typical set point selection electrometer 63 is shown in FIG. 2, which has a voltage range of 1:4! between the power supply 47 and ground potential. @
Connect via 48c. A pot 63 is provided for each set point or limit setting. By adjusting each pot 63, the operator selects an analog voltage representing one of the aforementioned set points.

Microprocessor-45 has random access memory (RAM) and read only memory (ROM). The ROM controls the operation of the cooling system 10 in binary form.
This program is used to store the variables and data used by the dud program. The general outlines of microprocessor-control of the type described above are well known in the art and there is no need to explain the details thereof. The programs stored in ROM, the functions they perform, and the physical parameters used and sensed to perform these functions distinguish this embodiment of the invention from other conventional microprocessor cooling controls. They are different.

The overall picture of the control/roll algorithm of the cooling system is shown in the third section.
As shown in the flowchart of the figure. The program starts at block 100, followed by instructions 101, which refer to the chiller t (compressor 13).
) is inactive. Instruction block 102 implicitly encompasses several operations. Therein, microprocessor 45 instructs multiplexer 46 to select a cooling fluid temperature setpoint signal, an analog value representing the temperature of the cooling fluid, and a start setpoint difference signal. By selecting digital values equal to these analog signals (as provided by A-D converter 49), microprocessor 45 sets the set point shown as variable "E" or error in the flowchart of FIG. Compute the initial deviation of the cooling fluid temperature from If so, the program returns to block 101 where the cooling system is stopped (if not, it has already stopped).
5 completely closes the inlet guide vane 66, starts the compressor 13 and begins setting the variables consisting of: El equal to the initial error E, SE equal to O, and ST equal to 6. . The importance of these variables will become clear from the following explanation.

In the preferred embodiment, the user generally selects 0″F(-
It is desirable to choose a value for the starting differential set point equal to approximately 50% of the design capacity of the cooling system at a temperature of 17,8° C.). For example, when the cooling system is at full capacity, the temperature of the fluid being cooled by the evaporator 21 is 10"F (-12").
, 2°C), the starting differential set point X is set to 5''17 (-15°C).

Other values for X may be used depending on the characteristics of the cooling system. The value selected for X is first used in the control algorithm to determine whether the cooling device is activated initially and in block 105 in the calculation of the variable STP. Variable S T
P +; into the equation S T P = 0.8 * X
−4 d is calculated accordingly. Block 105 also starts a 5 second timer internal to microprocessor-45. The five second interval is determined by a crystal time pace 53 connected to microprocessor-45. A counter accumulates clock pulses in the microprocessor's internal registers until the count reaches 5 seconds.

If the calculated value of STP is less than 2, instruction blocks 106, 107 set a lower limit and set STP equal to 2.
Set TP. For example, if X is 4, block 1
The value of STP calculated according to the equation at 05 is -0,8
becomes. Therefore, according to the program logic in blocks 106 and 107, the value of STP is set to 2.

Returning now to FIG. 2, a cooling fluid temperature set point range selection switch 54 is provided on the unit control 25 to allow the user to select either an expanded range or a standard range for the cooling fluid temperature set point. Allow choice. In the standard range, the cooling water temperature set point is the limit temperature 377 (2
, 8°C) and 60'F' (15.5°C).

If an ethylene glycol solution is used instead of water as the cooling fluid, the operator can set the cooling fluid set point to 20 below (-67
C) to 70"F (21 C.). Instruction block 108 checks the state of switch 54 to determine whether the standard range is selected; If so, it is 353
The temperature of the water exiting the evaporator is checked at sensor 29 to determine if it is below (1.8° C.). If so, the program returns to block 101 to shut off the cooling system and prevent further cooling. Otherwise, it is the instruction block 110
Then, it is checked whether the error E is smaller than 13TP.

Instruction 110 is also reached if there is a negative response to verification device 108. This condition occurs when the cooling system 10 is so lightly loaded that, at minimum capacity, the temperature of the cooling fluid drops below the set point by a value above the STP value. Under these conditions, instruction block 111 specifies in instruction block 112 that the SE value is -118*S
It works to integrate the variable SE until it becomes smaller than TP.

If this happens, instruction block 1
01 stops the cooling device. During successive passes through the program logic, if the error E is greater than -3TP, then S
The value of E is 0 in the instructor input block 113.
is set to If the result in instruction block 112 is negative, or after completing instruction block 113, the program continues to block 114, a subroutine entitled "Evaporator Exit Water Temperature Control."

FIG. 4 shows that block 114 requires liquid leaving the evaporator (
3 is a flowchart of a subroutine for adjusting the temperature of cooling fluid. The subroutine starts at block 200 and then proceeds to block 201 where microprocessor 45 uses multiplexer 46 to
The control gain setting signal of lead 59 is selected for D conversion, and the resulting digital value is set as variable II C''.
Assign to. In this instruction, the microprocessor-45 also calculates the change in the cooling fluid error by calculating the difference between the current value and the previous value of the error E and assigns that change to the variable "D E". Assign.

The next instruction block 202 checks to see if the current error is positive, i.e. greater than O, and if it is, the error is set to 0.1 in instruction block 203. *S
Convert the program logic to determine whether T P is exceeded.

If the response is positive, instruction block 2
04 checks whether the error exceeds 0.4*S T P, and if not, instruction block 205 determines whether the change in error DE is greater than zero. Verification device 203 or 20
If the response to 5 is negative, the program logic advances to instruction block 206 where the variable II D S I+ (indicating the relative change in the position of the inlet guide vane) is set to O. Match value @204,205
If the response to is positive, the program logic proceeds to instruction block 207 where it sets a variable DS equal to the product of the gain setting and the error, ie, C*E.

Returning now to instruction block 202, if the error is less than or equal to O, instruction block 208 then checks to see if the error is less than -0,1*STP. If so, block 209 determines that its error is -0,4* S T P
Determine if it is less than. If the response to the verification device is negative, it is determined whether the change in error DE is less than zero at instruction block 210. If the response to the verification device 208, 210 is negative, the variable aDS is set to 0 in instruction block 211.

If the response to the collation device 209, 210 is positive, the process proceeds to instruction block 207 where the variable DS is set to a value equal to the product of the gain setting C and the error E, as described above.

A positive error or a negative error is the amount of change D in the position of the inlet guide vane.
The fact that the flowchart in Figure 4 gives rise to the same amount of change (albeit in the opposite direction) as S and that the value associated with this change depends on the relative and absolute magnitude of the error indicates that the flowchart in Figure 4 has a symmetrical appearance. It becomes clear from what is shown. Regardless of the value of DS chosen, i.e. 0 or the product of C*E, the program logic is then sent to the matching unit 212 where DS is greater than 0.013. Determine whether or not. If so, Ds is set to 0.013 in instruction block 213, thereby limiting the upper limit for relative changes in the position of the inlet guide vanes. Others, instruction block 21
4, determine whether Ds is less than -0,013, and if so, set DS to inetraxis 1
-0,013 in block 215 and DS
Set a lower limit for negative values of . Block 216 returns the program to instruction block 115 in the main control logic as shown in FIG.

Referring now to FIG. 5, the modulation of the compressor inlet guide vanes is graphically illustrated to maintain the effluent water fluid at a set point temperature. It can be seen that the relative change in the movement of the inlet guide vanes does not exceed ±0013, that is, the change in the position of the inlet guide vanes for each 5 second cycle of the program does not exceed ±1.3%. Furthermore, if the temperature error E is 01*STP ~ 0.1*STP,
Or tal error is 0.1 * S T PN2.4
* When S T P, if the change in error DE is less than 0, or fbl error is 10, 1 * STP~-0,4
*When S T P, if the error change DE is 0 or more,
The relative inlet guide vane movement DS is set to O. In the case of a positive error, when the change in error is also positive, ie increasing, the relative movement DS of the inlet guide vanes is set to the product of the gain setting C and the error E. Similarly, when the error is negative (less than minus 01*STP) and the change DE in the error is negative, i.e. increases in the negative direction, then DS likewise becomes C*
It is set to E.

In instruction block 115 of FIG.
The evaporator refrigerant temperature limit control subroutine begins. The logic of this subroutine is as shown in the flowchart of FIG.
Start from 00. The instruction 301 is
Set the variable “ETO” equal to the previous value denoted as evaporator refrigerant temperature “ET” and set the current analog input representing the evaporator cold W temperature and the evaporator refrigerant temperature “trip” setting. A multiplexer 46 is caused to select an analog input representing a point.

Offset limit “ETI” is trip +2 teeth (-1
6,7℃). These values are stored digitally in microprocessor-RAM for use by the algorithms.

Instructions 321 determine state B of switch 54, and if the cooling system is operating with a cooling fluid set point within the standard range, the program proceeds with verification device 322. If the trip set point is less than 307 (-1,1℃), the program will recalculate and become ET1 = ) lip + 1.5"F (-16,9℃). This uses water as the cooling fluid. In this case, this is necessary because the margin before freezing is small, and the refrigerant trip temperature of the evaporator is set at least 2 degrees lower than the freezing temperature of the water.

After the instruction 323, that is, the verification device 3
If, at 21, the system is indicated to be in extended range, or, after verification @322, the trip temperature is greater than or equal to 30 below (-11° C.), the program proceeds to instruction 302. At instruction block 302, the current evaporator refrigerant temperature ET
and its previous temperature is greater than or equal to 0375, and if so, instruction block 3Q3 determines whether the current value for F-T is E
Determine if T1+4″F (15.5° C.) or greater. If the check is answered in the affirmative, instructions 304 are returned to instruction block 116 of the main control algorithm.

Returning now to instructions 302, if the difference between the current evaporator refrigerant temperature and the previous temperature value is less than -0375, the variable "DS4" is set to 0.012441 (ET- E
TO+1.4375). Instruction block 306 then executes instruction 11
It is determined whether the relative change in the movement of the inlet guide vane DS determined in the subroutine No. 4 is greater than the variable DS4. If so, instructions 307 set DS equal to the value of DS4. Program logic then proceeds to instruction block 303 as described above.

In the verification device in instruction 303,
If the evaporator refrigerant temperature is at its set point ET1+4”l?(15
. If so, the variable "'DSI'" is set in instruction 3.
At 09, it is set equal to -0,124, and at instruction 310, the variable ST is set equal to the difference between the trip temperature and the evaporator refrigerant temperature ET minus its previous value. In successive cycles through instruction block 310, if the ST value is less than 0, the ST value is integrated in time up to the matching device 311, and if the cooling device is stopped, the algorithm jumps to instruction block 101 of the main program. . The purpose of the test to calculate the time integral of ST and determine when ST is less than O is to respond to conditions where the outside air temperature is relatively cold, but the cooling system is As it remains deenergized for a period of time, the fluid temperature increases and the cooling load initially exceeds the rated capacity of the cooling system. Under these conditions, the evaporator refrigerant temperature drops rapidly as the cooling system 10 is turned on. ST
By calculating the time integral for , the control gives the time for the cooling fluid to cool, but if the refrigerant altitude is below the trip value, it stops the compressor 13 before the circulating cooling fluid begins to freeze. Slow down.

Returning to the verification device 308, the evaporator refrigerant temperature ET
, becomes greater than the trip temperature, ST is reset to 6 in instruction 313 and the matching value M3
Step 14: It is determined whether the value of ET is less than or equal to the refrigerant set temperature of the evaporator - 3°. If so, instructions 315 set the SDI equal to the difference between the evaporator refrigerant temperature and the offset limit times 0005, or 0005*(ET-ETI).

If the result of the verification device 314 indicates another value, the verification device 31
6 determines whether the ET value is greater than ET1+0.6°. If so, variable DS1 is set to 0.0006* (ET-E
T1+1.5). Other DS1 is set to O in instruction block 318.
is set to Instruction block 311,3
15, 317 or 318, the verification device 31
9 determines whether the current value (relative movement of the inlet vane) to DS is greater than the variable DS1. If so, instruction 320 sets DS equal to DSL, then instruction 3
Exit the subroutine at point 04.

As is clear from FIG. 6, the instruction 304
, the variable DS is equal to the algebraic minimum of the DSA and DSl values, and the original DS (entry block 3
00) depends on the relationship between the evaporator refrigerant temperature and the set point. When the evaporator refrigerant temperature approaches or is close to its set point and trip 1 degree, the capacity of the chiller is reduced to m! 1 control algorithm is the 7th
．． This is shown in Figure 8. In Fig. 7, the difference between the current evaporator refrigerant temperature and the previous value of DS41 is -
0375 to -0,4375, it is calculated as a function of the difference. Furthermore, the maximum value of DS4 is effectively limited to 0.013. Because DS4 indicates in instruction blocks 306 and 307 that
Only when it is smaller than S, it can be replaced with DS. Offset limit ETI from evaporator refrigerant temperature ET
If the value obtained by subtracting is less than 47 (-15,5℃),
DSl values are calculated according to four possible equations.

If ET-ETI is O,S~4, then DSI is 0.0
06*(ET-ET1+1.5). E.T.
When the -ETI is between -0,3 and 06, the DSI is O.

When ET-ETI is AA ~ -03 (because AA calculates ETI minus the value added to the rip set point), DSl will be equal to O,OO5* (ET-ETI l). And finally, if ET-ETI is less than AA, DS1 will be equal to -0124.

Again, it is important that upon exiting instruction 304, the program's logic retains as DS the algebraic minimum value of the inlet guide vane movement calculated in the preceding control algorithm.

Instrafusian block 116 identifies line current limit control as the next subroutine used by the program logic. The algorithm for this subroutine is shown as a flowchart in FIG. 9, starting at instruction block 400.

After entering at this point, follow instruction 4.
01 causes the multiplexer 46 to select the analog line current signal and the current set point signal, convert them to digital values using the A-D converter 49, and convert these values to the microprocessor. Store in RAM as variables "SS" and "5S1N, respectively. Verifier i 1402 determines whether the difference between the measured Ti current and the set point for the current limit is less than -01. If so, the current is not close enough to its set point to justify modulation of its capacity and the control logic exits instruction block 403.
The verification device 404 determines that the difference between the current and its set point is 02
Determine if it is less than. If not less than 02, at instruction block 405,
The variable “D S 2 ” is 0.6* (SSI-3S+0
．． 017). In addition, the matching value @406 indicates that the difference between the current and its set point is -0,0
2, and if so, instruction 407 sets DS2 to 0.14*(331
-33-0,013).

If the response to verifier 406 is negative, instructions 408 set DS2 to zero.

Following instructions 405, 407 or 408, matcher 409 determines whether DS is less than DS2, and if not, instructions 410 set DS equal to DS2. Thus, the current control limit algorithm exits at 403. The DS value is then equal to the algebraic minimum of the previously calculated value DS at entry block 400 and DS2.

Figure 10 shows the variable DS depending on whether the value (33-3SI) is greater than 002 or between -01 and -002.
2 is calculated according to two different functions of (SS1-33). A dead band in which DS2 is set to 0 means that (S81-SS) is -002 to 0.
1 over a range equal to 02.

Following instruction block 116, the control logic of FIG. 3 proceeds to a subroutine labeled "Condenser Pressure Limit Control," ie, instruction block 117. The program logic for this subroutine is entry block 5.
Starts with 00. The instruction block 501 sends the capacitor pressure analog signal and the capacitor pressure setting limit signal to the multiplexer 46 from A to D.
selected for conversion and microprocessor-4
5, it is stored in RAM. The condenser pressure is standardized on a scale of zero to one and stored as the variable "CP", whereupon the set point for this operating parameter limit is also standardized and stored as "cpi". Verifier 502 determines whether the difference between the standardized capacitor pressure and its limit is less than -0,1, and if so, program logic performs this at instruction block 503. Exit the subroutine. This is because the pressure in the capacitor is well below its limit and will not cause any problems.

Additionally, verification device 504 determines whether the standardized capacitor pressure is less than a set point, and if not, instructions 505
sets the variable “DS3” to 0.3*(CPI-CP-0,00
5). If the result of the verification device 504 is positive, the verification device 506 determines whether the difference between the normalized capacitor pressure and its limit is less than −0.04. If it is smaller than that,
Variable DS3 is set equal to 067 lines (CP 1 - CP - 0,018) in instruction block 507. Others, 50 instructions
8 sets DS3 equal to 0. Following instructions 505, 507 or 50B, the match value 'f! 1
509 checks to determine if DS is less than DS3, and if not, then
Instructions 510 set DS equal to DS3. Instruction 509 or 510
Following either of these, the control logic exits at 503 to instruction block 118 of FIG.
Return to

The modulation of the capacity of the cooling system for the relative movement of the inlet guide vanes in relation to the standardized condenser pressure DS3 is shown in FIG. even here,
DS3, if the value of (CP-CPI) is greater than O, the condenser pressure and its setting IJ
Equal to the function, the value of CP-CPI is -01 to -0,04
It is clear that if it is in the range of , it is equal to the second function.

The deadband when DS3 is set equal to 0 extends over the range -0.04 to 0 (CP-CPI). Again, DS is equal to the algebraic minimum of its previous value when entering the algorithm at block 500, and the DS3 value is calculated by the capacitor pressure limit control algorithm.

Instruction block 118 of FIG. 3 causes microprocessor 45 to adjust the inlet guide vane according to the DS value calculated in the preceding subroutine, ie, that value at instruction 503. This adjustment is accomplished by energizing the inlet guide vane drive i65 so that the drive opens and closes the inlet guide vane according to the DS value calculated as described above. Verification device 119ζ of FIG. 3 determines whether the 5-second timer is keeping track of time; if not, loops through verification bag W 119 until the timer status is satisfactory. Let it form. At this point, instruction 12
0 assigns the current value of the cooling fluid 1 degree error E to the variable E1 and sends the multiplexer 46 to the starting difference set point, the cooling water temperature set point, and the current value for the analog to digital conversion. Analog signal of fluid cooling water temperature and 1! im selectively, and the microprocessor-
45 to calculate the error F. The program then returns to instruction block 105 to cycle through the program once every five seconds.

〔Effect of the invention〕

Each of the algorithms formed by instruction blocks 115, 116 and 117 determines when one of the operating parameters (i.e., evaporator refrigerant temperature or flow and condenser pressure) approaches a limit (beyond that limit). (the system must be shut down to avoid catastrophic failure thereof), the potential is such that the temperature control of the liquid exiting the evaporator in subroutine 114 is maintained as necessary to maintain the cooling system 10 in operation. This feature allows the cooling of the evaporator even when the desired retentate temperature set point cannot be achieved, rather than continuing to operate at full capacity to the point where the system is shut down completely. System 10 and comfort zone 11
can be cooled.

Another result of the invention is the regulation of the temperature of the liquid leaving the evaporator. Typically, the capacity of the cooling system 10 is modulated by adjusting the inlet guide vanes as a function of temperature error and gain settings around one of two deadbands that depend on the error increase or decrease. When the temperature error is reduced, the relative movement DS of the inlet guide vanes is over a relatively wide deadband, i.e. -4*STP~
0, 4 * S T P remains unchanged over 21! of the cooling liquid. When the degree approaches its set point, the adjustment becomes more stable. Also, when the temperature error of the coolant increases, a narrow deadband of −〇,1*STP~0.1*STP is used, which controls the capacity and minimizes the magnitude of the temperature error. . This control method reduces unnecessary changes in cooling system capacity and stabilizes the regulation of cooling liquid temperature.

Although this preferred embodiment uses inlet guide vanes to vary the capacity of the centrifugal cooling system, other devices may be used to modulate the capacity of the cooling system, such as a variable speed compressor drive motor. can be used as well. This basic control can also be used in systems where the heat transfer liquid is heated rather than cooled. Furthermore, this same control and method also applies to temperature regulating systems in which an expanding or condensing refrigerant fluid is used directly to cool or heat, respectively, a gaseous fluid such as air. As mentioned above,
These and other modifications to the preferred embodiment will be apparent to those skilled in the art within the scope of the following claims.

[Brief explanation of drawings]

Figure 1 is a block diagram of a liquid-based cooling air adjustment system whose capacity is adjusted by utilizing the present invention, Figure 2 is a schematic block diagram of a control device, and Figure 3 is an overall diagram. FIG. 4 is a flowchart illustrating the capacity control logic; FIG. The figure is a graph showing the temperature error of the fluid and the movement of the inlet guide vane regarding the first and second dead bands. Figure 6 is a flow chart showing the refrigerant temperature IJ it control logic of the evaporator. During evaporator refrigerant temperature limit control,
A graph showing the movement of the inlet guide vanes as a function of the temperature change of the cooling fluid, Figure 8, during evaporator refrigerant temperature limit control.
FIG. 9 is a flowchart showing the current limit control logic; FIG. 10 is a graph showing the movement of the inlet guide vane as a function of cooling fluid temperature error; FIG. FIG. 11 is a flowchart showing the condenser pressure control logic; FIG. 12 is a graph showing the movement of the inlet guide vanes as a function of cooling fluid error for condenser pressure control. [Explanation of symbols] O... Liquid cooling system 11... Comfort area 1
2a...Supplementary M line 12b...Line 13.
...Centrifugal compressor 14...Condenser 15...Line 16
0. Cooling tower 17λ, 17b...Line 18...Line 19...Expansion device 2
0...Line 21-゛°Evaporator 22-
...Line 25...Unit controller 26...Automatic system controller for ti products 2g1
8. Line 29...Temperature sensor 30
... Line 35 ... Evaporator refrigerant temperature sensor 36 ... Line 37 ... Supply current sensor 38 ... Two-phase power supply lead 39 ... Lead 40 ... Condenser pressure sensor 45 ... Microprocessor - 46... Multiplexer - 47... Power supply body 48m
, 48b... Lead 49... Analog to digital converter 50... Lead 65... Inlet guide vane drive device 63... Set point selection electrometer

Claims (1)

Claims: 1. A system for temperature regulating a fluid to a predetermined set point temperature, comprising: a. a temperature sensor responsive to the temperature of the regulating fluid; and b. a first deadband and a second relatively wide deadband. e. a selection device for a second variable used to determine the width of the temperature sensor and the temperature sensor; e. a selection device for a second variable used to limit the gain settings for system capacity control; a control device connected to the first and second variable selection devices and responsive to the regulated fluid temperature, the first variable and the gain settings; and the control device selects widths of the first and second dead bands as a function of the first variable. determine the deviation of the fluid temperature from its set point,
Further, if the absolute deviation value of the fluid temperature from the set point increases, a first dead band is used, and if the absolute deviation value decreases, a second wider dead band is used. Control of system capacity consists of adjusting the capacity of the system to maintain the temperature of the regulating fluid near the set point as a function of the gain setting. 2. The temperature control system has a centrifugal compressor,
System capacity control according to claim 1, characterized in that the control device adjusts the capacity of the compressor to maintain the temperature of the regulating fluid near a set point. 3. System capacity control according to claim 2, characterized in that the temperature regulation system has an inlet guide vane to adjust the capacity of the compressor. 4. The control device adjusts the capacity of the system by adjusting the inlet guide vanes at predetermined time intervals.
System Capacity Control as described in Section. 5. System capacity control according to claim 4, characterized in that the change in the increasing direction of the system capacity does not exceed a predetermined maximum value in each time interval. 6. System capacity control according to claim 1, characterized in that the change in system capacity is determined by the product of the gain setpoint and the deviation of the regulating fluid from its setpoint temperature. 7. System capacity control according to claim 1, characterized in that the control device comprises a microprocessor. 8. A refrigerant compressor with variable capacity;
In a liquid cooling system having a condenser and an evaporator for cooling liquid supplied to cool a load, the system comprises: a. a temperature sensor responsive to the temperature of the coolant exiting the evaporator; b. a first dead band and a first dead band. a first variable selection device used to determine a second relatively wide deadband; said first variable being selected by an operator as appropriate for the cooling system being controlled; c. a second variable selection device for limiting gain settings for said control, said variable being selected by an operator as appropriate for the controlled cooling system; d. a first variable selection device connected to a temperature sensor; and a control device connected to the second variable selection device and responsive to the temperature of the coolant exiting the evaporator, the first variable and the gain setting, the control device being connected to the first variable and the first and second predetermined constants. determining the width of the first and second dead bands, respectively, as a function of the deviation of the cooling liquid temperature from the set point, and using the first dead band as the absolute value of said deviation increases; , adjusting the capacity of the compressor to maintain the coolant temperature near its set point as a function of the gain setting and the deviation by using a wider second deadband when the absolute value of the deviation decreases; a control that modulates the capacity of the compressor to maintain the temperature of the coolant exiting the evaporator near a predetermined set point, consisting of: 9. Control according to claim 8, characterized in that the compressor is a centrifugal compressor with inlet guide vanes to adjust the capacity of the compressor. 10. The control device modulates the capacity of the compressor by adjusting the inlet guide vanes at predetermined time intervals,
Control according to claim 9. 11. Control according to claim 10, characterized in that the incremental change in compressor capacity does not exceed a predetermined maximum value during each time interval. 12. Control according to claim 8, characterized in that the change in compressor capacity is determined by the product of the gain setpoint and the deviation of the coolant from its setpoint temperature. 13. Control according to claim 8, characterized in that the control device consists of a microprocessor. 14. a. Selecting a first variable used to determine the width of the first deadband and a second relatively wide deadband, and b. A second variable used to define the gain settings for control of the system. c. determining the width of the first and second dead bands as a function of the first variable; d. sensing the temperature of the temperature-adjusted fluid; and e. determining the temperature of the fluid from the set point. determining the deviation, f, using a first deadband if the absolute value of the deviation of the fluid temperature from the set point increases; if the absolute value of said deviation decreases;
The process consists of modulating the capacity of the system to maintain the temperature of the regulated fluid near the set point as a function of the gain setting by using a wide second deadband, and the temperature of the fluid to the predetermined set point. A method used to control the capacity of a system used to regulate it. 15. The method according to claim 14, characterized in that the temperature regulation system comprises a centrifugal compressor with inlet guide vanes for regulating the capacity of the compressor. 16. A method according to claim 15, characterized in that the control device modulates the capacity of the system by adjusting the inlet guide vanes at predetermined time intervals. 17. The method of claim 16, further comprising the step of limiting the change in system capacity to a predetermined maximum value during each time interval. 18, the patent further comprising the step of multiplying the gain set point by the deviation of the regulating fluid from the set point to determine the magnitude of the change in system capacity required to reduce the deviation. The method according to claim 14. 19. A temperature regulation system for regulating a fluid to a set point temperature, comprising: a. a device for sensing the state of an operating parameter; b. a device for selecting limits for the operating parameter; and c. responsive to the sensing device and the selection device. and determine the deviation of the operating parameter from its limit, and if the deviation is at or greater than the deadband, follow a first predetermined function of the deviation, and if the deviation is less than the deadband, follow a second predetermined deviation function. and a control device that modulates the capacity of the system by complying with the system to avoid major failures when operating parameters are near limits that lead to a protective shutdown of the system. Control to do. 20. The control of claim 19, wherein the control device further modulates the capacity of the system to maintain the regulating fluid near the set point temperature. 21. The control device controls the system according to one of the first and second predetermined functions, rather than holding the regulating fluid at the set point, if the deviation of the operating parameter from the limit is less than a first predetermined value. 21. Control according to claim 20, characterized in that it modulates the capacity. 22. Control according to claim 21, characterized in that the temperature regulation system has a refrigerant condenser, and the sensing device comprises a pressure sensor for sensing the pressure of the refrigerant fluid in the condenser. 23. Claim 21, characterized in that the sensing device comprises a line current sensor that senses the operating line current supplied to operate the temperature control system.
Controls described in Section. 24. Control according to claim 21, characterized in that the temperature regulation system has a refrigerant evaporator, and the sensing device comprises a temperature sensor for sensing the temperature of the refrigerant fluid in the evaporator. 25, a. if the deviation is greater than a second predetermined value, b. if the change in system capacity determined according to said change function of the temperature of the refrigerant fluid is less than the change required to adjust that fluid to the set temperature: the control device modulates the system capacity according to a predetermined change function of the evaporator refrigerant fluid temperature;
Control according to claim 24. 26. Control according to claim 19, characterized in that the temperature regulation system comprises a centrifugal compressor with inlet guide vanes used to modulate the capacity of the compressor. 27. Claim 2, characterized in that the control device adjusts the capacity of the system by adjusting the inlet guide vanes at predetermined time intervals.
Control as described in Section 6. 28. A temperature regulation system for regulating a fluid to a set point temperature, comprising: a. a device for sensing the state of an operating parameter; b. a device for selecting limits for the operating parameter; and c. A control device that determines the deviation of an operating parameter from a limit and, if the deviation is within a predetermined increment, adjusts the capacity of the system as a function of the deviation, rather than holding the fluid at its set point temperature. A control that adjusts the capacity of a system to maintain fluid temperature at a set point to prevent major failure or damage unless operating parameters are near such limits that would cause a protective shutdown of the system. . 29. In a temperature regulation system that regulates a fluid to a set point temperature, a. sensing the state of an operating parameter; b. selecting a limit for the operating parameter; e. determining a deviation of the operating parameter from that limit; d. adjusting the capacity of the system by following a first predetermined function of the deviation if the deviation is greater than the predetermined deadband and by following a second predetermined function of the deviation if the deviation is less than the deadband; A method of controlling the capacity of a system when the operating parameters of the system are near limits that lead to preventive shutdown of the system to prevent major failures. 30. The method of claim 29, further comprising the step of adjusting the capacity of the system to maintain the conditioning fluid near the set point temperature. 31, adjusting the system capacity according to one of the first and second predetermined functions comprises holding the regulating fluid at the set point if the deviation of the operating parameter from the limit is less than the first predetermined value; 30. The method according to claim 29, characterized in that it is carried out preferentially. 32. Method according to claim 31, characterized in that the temperature regulation system has a refrigerant condenser and the operating parameter consists of the pressure of the refrigerant fluid in the condenser. 33. Method according to claim 31, characterized in that the operating parameter consists of the line current supplied for operating the temperature regulation system. 34. Method according to claim 31, characterized in that the temperature regulation system comprises a refrigerant evaporator and the operating parameter consists of the temperature of the refrigerant fluid of the evaporator. 35. Claim 34, further comprising the step of determining at any time a change in the refrigerant fluid temperature of the evaporator.
The method described in section. 36, a. if the deviation is greater than a second predetermined value; b. the change in system capacity determined according to said function of change in refrigerant fluid temperature is less than the change required to regulate the fluid to the set point temperature; 36. The method of claim 35, further comprising the step of: adjusting the capacity of the system according to a predetermined function of the change in temperature of the evaporator refrigerant fluid. 37. The method according to claim 29, characterized in that the temperature regulation system comprises a centrifugal compressor with inlet guide vanes used to regulate the capacity of the compressor. 38. Claim 37, characterized in that the step of adjusting the capacity of the system comprises the step of adjusting the inlet guide vanes at predetermined time intervals.
The method described in section.