JPH04278144A - Turbo freezer and its volume control device - 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]

0001

[Industrial Application Field] The present invention relates to a centrifugal chiller and its capacity control device, and in particular, a microcomputer (MCU) calculates a command value to a control motor that drives a vane damper, and the calculation method uses fuzzy control. This invention relates to a centrifugal chiller to which this technology is applied and its capacity control device.

0002

2. Description of the Related Art As a conventional device for controlling the opening degree of a vane damper of a centrifugal chiller, for example, Japanese Patent Laid-Open No. 60-660
As described in Publication No. 76, there is a determination means for determining whether or not the operating capacity is full capacity operation based on the temperature detected by a first sensor that detects the outside air temperature when the refrigerator starts operating, and A device is known that includes a second sensor that detects the cold water outlet temperature related to the controlled temperature after a certain period of time, and a correction means that changes the operating capacity at the start of operation based on the output of the second sensor. As for the correction control, depending on the state where the cold water outlet temperature is far from the target temperature, the opening of the vane damper is commanded by so-called PID control such as proportional operation (P operation), integral operation (I operation), differential operation (D operation), etc. was outputting.

0003

[Problem to be Solved by the Invention] In the conventional vane damper opening control using PID control based on the chilled water outlet temperature, when the refrigerator is started, the chilled water has not yet cooled, and the chilled water outlet temperature is far from the target value. Therefore, the P and I operations are strongly effective. As a result, when the load is small, the vane damper closing command may not be issued in time and the cold water outlet temperature may fall too much below the target value. Generally, in a centrifugal chiller, when the chilled water outlet temperature becomes 1.5 degrees Celsius lower than the target temperature, the main motor is stopped, the chiller is stopped, and the chilled water outlet temperature gradually begins to rise, and when it becomes 8 degrees Celsius higher than the target temperature. The refrigerator has an automatic start/stop function that automatically restarts operation. However, once the main motor is stopped, it takes 15 minutes to restart it.
minutes of time are required. Furthermore, the main motor consumes a large amount of starting power when it is started from a standstill, and frequent automatic starting and stopping shortens the life of the machine.

Therefore, in conventional PID control, when the load capacity is small or when load fluctuations are large, the chilled water outlet temperature overshoots and automatically starts and stops, resulting in a reduction in power consumption and machine life. There was a problem. Also, P.I.
In the D control, it is necessary to adjust the constant of the PID, and the adjustment work must be carried out by an adjuster through an on-site test run, and there is a problem in that a specialized adjuster is required.

The present invention has been made to solve the problems of the prior art described above, and is aimed at preventing automatic freezing of the refrigerator due to overshoot that occurs when starting the refrigerator when the load fluctuates rapidly or when the load is small. To provide a centrifugal chiller and its capacity control device that can prevent starting and stopping, do not require on-site adjustment, reduce power consumption, extend machine life, and reduce the number of on-site adjustment personnel. This is the purpose.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the configuration of a turbo chiller according to the present invention consists of a turbo compressor equipped with a vane damper, a condenser, and an evaporator, and a In a centrifugal chiller in which the opening degree of a vane damper is controlled according to the temperature of a chilled water system, there is provided a means for detecting a chilled water outlet temperature of the evaporator, an amount of change in the chilled water outlet temperature based on the detected output, and a change in the chilled water outlet temperature. Means for calculating the opening command value of the vane damper by using a deviation from the target value as a membership function and a combination of a plurality of control rules including judgments based on past knowledge data, and calculating the opening of the vane damper according to the opening command value. It is equipped with a control motor that drives the.

The present invention also provides a temperature sensor that detects the chilled water outlet temperature, receives the signal, calculates the deviation from the target value and the amount of change in the chilled water outlet temperature, and uses the deviation and the amount of change to The opening degree of the vane damper is controlled by reproducing the operations of the field surveyor by combining the experience and knowledge of the adjuster with multiple rules. Furthermore, since control is performed based on the deviation from the target value and the amount of displacement, it is possible to control the vane damper by following sudden changes in load.

[0008]

[Operation] The temperature sensor detects the chilled water outlet temperature, and calculates the deviation of the chilled water outlet temperature from the target value and the amount of change in the chilled water outlet temperature per unit time. The opening of the vane damper is controlled using fuzzy control, which takes these deviations and changes as membership functions and incorporates the experience and knowledge of local coordinators into a knowledge database as control rules. Therefore, there is no need for on-site adjustment work such as adjusting PID control constants. In addition, although the deviation and amount of change in the chilled water outlet temperature change from moment to moment, since control is performed based on this, it is easy to follow load fluctuations, and the chiller itself does not start or stop automatically. This will reduce the power consumption required for starting the traction motor and further extend the life of the machine.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 5. FIG. 1 is an overall configuration diagram of a centrifugal chiller to which the present invention is applied, and FIG. 2 is a block diagram of a vane damper opening control device for a centrifugal chiller according to an embodiment of the present invention. In FIG. 1, 1 is a main motor, 2 is a turbo compressor, 3 is a compressor impeller, 4 is a condenser, 5 is an evaporator,
6 is cold water flowing through the evaporator 5; 7 is cooling water flowing through the condenser 4; 8 is a vane damper provided at the compressor inlet; 9 is a cold water outlet for detecting the cold water outlet temperature of the evaporator 5. Temperature sensor, 12 microprocessor (MCU), 1
3 is a control motor that drives the vane damper 8 to open and close. In FIG. 2, 9 is the cold water outlet temperature sensor, 10 is an analog/digital (A/D) converter, 11 is a timer, and 12 is a microprocessor (MCU) for calculating the opening command value of the vane damper. ), 1
3 is the aforementioned control motor.

In the turbo compressor 2, the impeller 3 is rotated at high speed by the main electric motor 1, and the refrigerant vapor generated in the evaporator 5 is compressed to the pressure in the condenser 4. The heat generated during the compression process is removed by the cooling water 7 flowing in the condenser 4, and the refrigerant vapor is cooled to the condensation temperature and becomes a liquid refrigerant. This liquid refrigerant flows into the evaporator 5 due to the pressure difference. The refrigerant liquid is evaporated in the evaporator 5 at a boiling temperature corresponding to the internal pressure. At this time, the cold water 6 is cooled in order to remove heat from the cold water 6 flowing in the evaporator 5. In this manner, the refrigerant sequentially repeats the four processes of evaporation, compression, condensation, and depressurization within the refrigerator, and cools the cold water during the evaporation process. The refrigeration capacity is controlled by adjusting the amount of refrigerant by adjusting the opening degree of the vane damper 8. The vane damper 8 is driven by a control motor 13 and opens and closes via links and gears (not shown).

FIG. 2 is a diagram illustrating a device for controlling the control motor 13 that drives the vane damper 8. As shown in FIG. Detecting the cold water outlet temperature by a cold water outlet temperature sensor 9,
The detection signal is digitally converted by the A/D converter 10 of the MCU 12. Using this detected temperature and the function of the timer 11, the chilled water outlet temperature for a certain period of time is calculated, and the deviation between the chilled water outlet temperature and the chilled water outlet target temperature is calculated. The vane damper 8 is controlled by controlling the command to the control motor 13 by fuzzy control based on this deviation and the amount of change.
This controls the opening and closing of the cold water outlet and controls the temperature of the cold water outlet.

Next, a method for controlling the command value of the control motor 13 will be described with reference to FIGS. 3 to 5. Figure 3 shows
Diagram showing membership functions used in this example, FIG. 4
5 is an explanatory diagram showing a control rule for the deviation and change amount of the cold water outlet temperature and the manipulated variable of the vane damper, and FIG. 5 is an explanatory diagram for determining the opening manipulated variable of the vane damper by fuzzy control. The deviation and amount of change in chilled water outlet temperature are defined as follows. Chilled water outlet temperature deviation = Target value - Chilled water outlet temperature Chilled water outlet temperature change amount = Current cold water outlet temperature - Previous cold water outlet temperature A membership function is determined for these deviations and changes as shown in FIG.

First, the symbols representing evaluation by membership functions in the following explanation are defined as follows. PB: (Positive Big) Positive and quite large (quite open) PM: (Positive Medium) Positive and large (open) PS: (Positive Small) Positive and slightly large (slightly open) ZO: (Zero) Equal, no change ( NS: (Negative Small) Negative and slightly large (slightly closed) NM: (Negative Medium) Negative and large (closed) NB: (Negative Big) Negative and quite large (quite closed)

[0014] In general, a membership function is a numerical representation of the human sense of whether a deviation or amount of change is large or small. For example, when the temperature deviation is −2.5 (deg), the proportion matching NB is 0.5, and the proportion matching NM is also 0.5. That is, the deviation is -2
．． If it is 5 degrees, it is assumed that it is compatible with both NB and NM. The membership function of deviation is shown in Figure 3 (
As shown in a), 5 of NB, NM, NS, ZO, PB
Type. Furthermore, as shown in FIG. 3(b), there are three types of membership functions for the amount of change: NB, ZO, and PB. The reason why there is only one positive deviation evaluation in the deviation membership function in Figure 3(a) is that when the temperature drops below the target value, the vane damper is operated as soon as possible to avoid reaching the automatic start/stop temperature. This is to do so.

The membership function of the vane damper opening command is determined as shown in FIG. 3(c). In FIG. 3(c), the horizontal axis indicates the manipulated variable with respect to the current opening degree command value. Opening and closing are evaluated differently in order to make the operation amount sensitive to the command for closing.

Next, fuzzy control rules are defined as shown in FIG. Control rules will be created incorporating the know-how and experience of local coordinators. Therefore, the operations performed by the local coordinator can be reproduced. In FIG. 4, the vertical axis shows the evaluation of the cold water outlet temperature deviation, and the horizontal axis shows the evaluation of the amount of change in the cold water outlet temperature, and what is written at the intersection of the evaluations is the evaluation of the operation and use of the vane damper. That is, each control rule is described as follows.

Rule 1: If the deviation is NB and the amount of change is NB, the operating amount of the vane damper is PM. Rule 2: If the deviation is NB and the amount of change is ZO, the operating amount of the vane damper is PB. Rule 3: If the deviation is NB and the amount of change is PB, the operating amount of the vane damper is PB. Rule 4: If the deviation is NM and the amount of change is ZO, the operating amount of the vane damper is PM. Rule 5: If the deviation is NS and the amount of change is NB, the operating amount of the vane damper is NS. Rule 6: If the deviation is NS and the amount of change is ZO, the operating amount of the vane damper is PS. Rule 7: If the deviation is NS and the amount of change is PB, the operating amount of the vane damper is PS. Rule 8: If the deviation is ZO and the amount of change is NB, the operating amount of the vane damper is NS. Rule 9: If the deviation is ZO and the amount of change is ZO, the amount of operation of the vane damper is ZO. Rule 10: If the deviation is ZO and the amount of change is PB, the operating amount of the vane damper is PS. Rule 11: If the deviation is PB and the amount of change is ZO, the operating amount of the vane damper is NS.

The above control rule increases the opening degree of the vane damper when the chilled water outlet temperature is extremely high, and reduces the opening degree of the vane damper when the chilled water outlet temperature decreases, causing the chilled water outlet temperature to cool beyond the target value. The human decision to close the vane damper has been directly converted into a rule.

Next, a method of determining the opening manipulated variable of the vane damper using fuzzy control will be explained with reference to FIG. (a), (b), and (c) of FIG. 5 are explanatory diagrams for calculating the opening operation amount of the vane damper from the deviation and amount of change regarding Rule 6, and (d), (e), and (f) of FIG. 5 is an explanatory diagram for calculating the opening operation amount of the vane damper from the deviation and amount of change regarding Rule 4, and (g), (h), and (i) of FIG. FIG. Here, the vane damper opening operation amount is determined using the Min-Max method and the center of gravity method, and as shown in FIG. 5, the chilled water outlet temperature deviation is -1.8
deg, and the cold water outlet temperature change amount is 0.1 deg.

First, the goodness of fit for each evaluation of the cold water outlet temperature deviation is determined. In this example, Figs. 5(a), (d), (
As shown in g), the goodness of fit for NS is 0.17, the degree of fit for NM is 0.75, and the goodness of fit for other evaluations is 0. Next, the goodness of fit for each evaluation of the cold water outlet temperature change amount is determined. In this example, Fig. 5(b), (e), (h)
As shown in the figure, the suitability of ZO is 0.5, the suitability of PB is 0.25, and the suitability for other evaluations is 0. Next, for each control rule, the minimum value of the evaluation suitability of the antecedent part is set as the suitability of the operation amount of the vane damper in each rule. For example, in rule 6, the fitness of the deviation is 0.1
7. Since the degree of adaptation of the amount of change is 0.5, the minimum value of 0.
17 is the degree of conformity of the operation amount of the vane damper to the evaluation PS. Do the same for all rules. Since all of the rules other than rules 4, 6, and 7 have a degree of conformity with respect to the evaluation of the antecedent part of 0, the amount of operation is also 0 in this example.

[0021] Next, among the degrees of conformity with respect to the obtained operation amount, the maximum value of the degrees of conformity is taken for evaluation of the same operation. In this example, rule 6 and rule 7 are shown in FIG. 5(c).
, as shown in (i), both are PS and the goodness of fit is 0.1.
7, so the goodness of fit for the manipulated variable PS is 0.17. Finally, the operating amount of the vane damper is determined using the center of gravity method. That is, as shown in FIG. 5(f), the degree of conformity of the evaluation of each manipulated variable is superimposed, and the center of gravity of the graph is determined. The position of the center of gravity indicates the manipulated amount of the vane damper's opening degree. In the example of FIG. 5(f), an operation command is issued to open the vane damper by 7%. The above steps are shown in Figure 2.
The MCU 12 shown in FIG. 1 performs calculations, outputs open and close commands according to the calculation results, and moves the control motor 13 to control the opening degree of the vane damper.

[0022] The above is an example of fuzzy control, and the method of determining membership and setting control rules is not limited to this. For example, in this example, the isosceles triangle shown in FIG. 5 was used as the shape of the membership function, but any other shape such as a triangle, trapezoid, bell shape, or any other shape that can be written as a function may be used. do not have. Further, the method of taking the horizontal axis of the membership function, the number of evaluations, etc. are not limited to this example, and the evaluation can be further divided into smaller sections. Control rules are not limited to this example either. In this example, as a membership function,
Although deviations and changes in the cold water outlet temperature have been discussed, other things necessary for control can also be incorporated. In this embodiment, the fuzzy inference is performed by software using the MCU, but this inference may be performed using another board or by an external computer. Furthermore, it can also be achieved by storing the calculation results as a table in ROM (read-only memory) in advance.

According to this embodiment, since the experience and know-how of on-site adjusters are incorporated into the control rules, it is possible to provide a vane damper control method that does not require the parameter adjustment work conventionally performed on-site. In addition, even when load fluctuations are severe, the chiller does not start or stop automatically without overshooting, and by reducing the number of times the traction motor starts, it is possible to extend the life of the traction motor and reduce power consumption. .

[0024]

[Effects of the Invention] As explained in detail above, according to the present invention, automatic starting and stopping of the refrigerator due to overshoot that occurs when starting the refrigerator when the load fluctuates rapidly or when the load is small is prevented. Furthermore, it is possible to provide a turbo chiller and its capacity control device that do not require on-site adjustment, reduce power consumption, extend machine life, and reduce the number of on-site adjustment personnel.

[0025]

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a turbo chiller to which the present invention is applied.

FIG. 2 is a block diagram of a vane damper opening control device for a turbo chiller according to an embodiment of the present invention.

FIG. 3 is a diagram showing membership functions used in this example.

FIG. 4 is an explanatory diagram showing a control rule for the deviation and amount of change in the cold water outlet temperature and the manipulated variable of the vane damper.

FIG. 5 is an explanatory diagram for determining the opening amount of the vane damper using fuzzy control.

[Explanation of symbols]

2 Turbo chiller 4 Condenser 5 Evaporator 8 Vane damper 9 Chilled water outlet temperature sensor 12 MCU 13 Control motor

Claims (2)

[Claims] Claim 1: A turbo compressor equipped with a vane damper;
In a centrifugal chiller comprising a condenser and an evaporator, and in which the opening degree of a vane damper is controlled depending on the temperature of a cold water system flowing through the evaporator, means for detecting a cold water outlet temperature of the evaporator and a detection output thereof. The amount of change in the chilled water outlet temperature due to the change in temperature and the deviation between the chilled water outlet temperature and the target value are used as membership functions, and the opening command value of the vane damper is calculated by a combination of multiple control rules including judgments based on past knowledge data. What is claimed is: 1. A turbo chiller comprising means for controlling the opening of a vane damper, and a control motor that drives the opening of a vane damper in accordance with the opening command value. Claim 2: A turbo compressor equipped with a vane damper;
A capacity control device for a centrifugal chiller comprising a condenser and an evaporator and configured to control the opening degree of a vane damper depending on the temperature of a cold water system flowing through the evaporator, comprising: means for detecting a cold water outlet temperature of the evaporator; , the amount of change in the chilled water outlet temperature based on the detection output, and the deviation between the chilled water outlet temperature and the target value are used as membership functions, and the opening degree of the vane damper is determined by a combination of multiple control rules including judgments based on past knowledge data. 1. A capacity control device for a centrifugal chiller, comprising: means for calculating a command value; and a control motor that drives the opening of a vane damper in accordance with the opening command value.