JP2016080202A - Heat source system, and cooling water control device and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent significant degradation of performance due to output restriction of a refrigeration machine and to realize a stable operation.SOLUTION: A heat source system includes a system control device 5 equipped with a cooling water flow rate function for controlling a flow rate of cooling water supplied to a refrigeration machine. The system control device 5 includes a target setting portion 22 and a target correcting portion 24. The target setting portion 22 sets a cooling water target flow rate by using a cooling water flow rate table in which a refrigeration machine load factor and the cooling water target flow rate are associated with each other. The target correcting portion 24 corrects the cooling water target flow rate set by the target setting portion 22 to an increase direction when the refrigeration machine is in a predetermined restricted state.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a heat source system, a cooling water control device thereof, and a control method.

  In a refrigerator such as a turbo refrigerator, cooling water cooled by a cooling tower or the like is supplied to a condenser and used for cooling a refrigerant (for example, see Patent Documents 1 and 2). Conventionally, as a method for controlling the flow rate of cooling water supplied to the condenser, a method based on the temperature of the cooling water (for example, see Patent Document 1) and a method based on the refrigerator load (for example, see Patent Document 2) have been proposed. Yes.

JP 2000-283527 A JP 2010-236728 A

  The conventional flow rate control method described above is, for example, a method of controlling the flow rate according to the production heat quantity of the refrigerator, and tends to reduce the cooling water flow rate when the production heat quantity decreases. With such a control method, there is a possibility of falling into a negative spiral as shown in FIG. That is, when the operating condition of the refrigerator becomes severe and the output is limited (state A in FIG. 7), control such as reducing the work amount of the compressor or the like works, and the production heat quantity of the refrigerator decreases (see FIG. 7). State B). As a result, the amount of exhaust heat decreases (state C in FIG. 7), so that the cooling water flow rate is also controlled to be reduced (state D in FIG. 7). When the cooling water flow rate is reduced, the cooling water temperature rises (state E in FIG. 7). When the cooling water temperature rises, the amount of work of the compressor increases, so that the operation is controlled in such a direction (state A in FIG. 7). As a result, the states A to E are repeated.

  Such repetition of states A to E may lead to failure of the refrigerator. Further, if the production heat quantity continues to decrease, the cold water outlet temperature may not be able to keep the set value.

  The present invention has been made in view of such circumstances, and a heat source system capable of avoiding a significant reduction in capacity due to the output limitation of the refrigerator and realizing a stable operation and its cooling water. It is an object to provide a control device and a control method.

  A first aspect of the present invention is a target setting unit that sets a cooling water target flow rate using information in which at least one of a parameter related to a refrigerator load and a parameter related to a cooling water temperature is associated with a cooling water target flow rate, A cooling water control device for a heat source system, comprising target correction means for correcting the cooling water target flow rate in an increasing direction when the refrigerator is in a preset restricted state.

According to the cooling water control apparatus of the heat source system, the target setting unit uses the information in which at least one of the parameter related to the load of the refrigerator and the parameter related to the cooling water temperature and the cooling water target flow rate are associated with each other, The flow rate is set. In this case, when the refrigerator is in a preset restriction state, the target correction unit corrects the cooling water target flow rate in the increasing direction. As a result, when the refrigerator is in a restricted state, more cooling water than normal control is supplied to the refrigerator. When the cooling water flow rate increases, the amount of work of the compressor decreases, and it becomes possible to alleviate severe operating conditions. As a result, the restricted state can be released early.
Examples of the “limit state” include current limit, high voltage limit, surging limit, and the like. The current limit is executed, for example, when the current flowing through the compressor motor is equal to or higher than a predetermined upper limit value, and the high pressure limit is executed when the refrigerant pressure of the condenser is higher than a specified value. It is executed when a predetermined condition regarding is satisfied.

  In the cooling water control apparatus of the heat source system, the target correction unit is configured such that the cooling water inlet temperature, the cooling water outlet temperature, or the difference between the cooling water inlet temperature and the cooling water outlet temperature is equal to or greater than a preset threshold value. In addition, the cooling water target flow rate may be corrected in the increasing direction.

  When the cooling water inlet temperature, the cooling water outlet temperature, or the difference between the cooling water inlet temperature and the cooling water outlet temperature is equal to or greater than a preset threshold value, it can be said that the above-described restricted state is easily entered. Therefore, when such a state is detected, it is possible to reduce the frequency of entering the restricted state by performing control to increase the cooling water target flow rate.

  In the cooling water control apparatus of the heat source system, the target correction unit may increase the cooling water target flow rate according to a constant change rate. At this time, the target correction means may increase the change rate as the difference between the limit value in the limit state and the measured value increases.

  In this way, the larger the difference between the limit value and the measured value in the limit state, that is, the more the refrigerator is placed in a stricter state, the more cooling water is supplied, thereby increasing the cooling water at a constant rate. It can be expected that the restriction state will be released earlier than if

  In the cooling water control apparatus of the heat source system, the target correction unit may change the cooling water target flow rate to a rated value.

  In this way, by changing the cooling water target flow rate to the rated value, it becomes possible to increase the flow rate of the cooling water supplied to the refrigerator at once. Thereby, it can be expected that the restriction state is released earlier than when the cooling water is gradually increased according to the predetermined rate.

  The cooling water control apparatus of the heat source system further includes information updating means for updating the information using the cooling water target flow rate when the restriction state of the refrigerator is released, and the target setting means is updated after the update. The cooling water target flow rate may be set using the information.

  According to the cooling water control device of the heat source system, since the cooling water target flow rate when the restriction state of the refrigerator is released is obtained and information is updated based on the cooling water target flow rate, The target setting means sets the cooling water target flow rate using information in which the flow rate is set to be higher than that of the control. Thereby, since the quantity of the cooling water supplied to the condenser of a refrigerator becomes larger than usual, it becomes possible to ease the work of a compressor. Thereby, it is possible to reduce the frequency of entering the restricted state.

  A second aspect of the present invention is a heat source system including a refrigerator and a cooling water control device for the heat source system.

  A third aspect of the present invention is a target setting step of setting a cooling water target flow rate using information in which at least one of a parameter related to a refrigerator load and a parameter related to a cooling water temperature is associated with a cooling water target flow rate, A cooling water control method for a heat source system, including a target correction step of correcting the cooling water target flow rate in an increasing direction when the refrigerator is in a preset restricted state.

  According to the present invention, it is possible to avoid a significant decrease in capacity due to the output restriction of the refrigerator, and to achieve an effect that a stable operation can be realized.

It is the figure which showed schematic structure of the heat source system which concerns on 1st Embodiment of this invention. It is the figure which showed schematic structure of the refrigerator which concerns on 1st Embodiment of this invention. It is a functional block diagram of a system control device concerning a 1st embodiment of the present invention. It is the figure which showed an example of the cooling water flow rate table. It is a functional block diagram of the system control apparatus which concerns on 2nd Embodiment of this invention. It is the figure which showed an example of the cooling water flow rate table after the update by a table update part. It is a figure for demonstrating the conventional subject.

[First Embodiment]
Below, the heat source system which concerns on 1st Embodiment of this invention, its cooling water control apparatus, and a control method are demonstrated with reference to drawings.
FIG. 1 is a diagram schematically showing an overall configuration of a heat source system according to the present embodiment. As shown in FIG. 1, a heat source system 1 includes a refrigerator 10, a cooling tower 2 that cools cooling water supplied to the refrigerator 10, and a water supply pump 3 that pumps cooling water from the cooling tower 2 to the refrigerator 10. I have. The frequency of the water pump 3 is variable by the inverter 4. Control of the inverter 4 is performed by a system control device (cooling water control device) 5. In addition, a temperature sensor 31 that measures the cooling water inlet temperature Tcwi is provided in the forward piping that supplies the cooling water from the cooling tower 2 to the refrigerator 10, and cooling is provided in the return piping that returns the cooling water from the refrigerator 10 to the cooling tower 2. A temperature sensor 32 for measuring the water outlet temperature Tcwo and a flow rate sensor 35 for measuring the cooling water flow rate Fc are provided. In addition, the flow sensor 35 may be provided in the outward piping.

FIG. 2 is a diagram illustrating a configuration example of the refrigerator 10. Here, a turbo refrigerator will be described as an example, but the present invention is not limited to a turbo refrigerator, and may be another refrigerator such as an absorption refrigerator.
As shown in FIG. 2, the refrigerator 10 according to this embodiment includes a compressor 11 that compresses a refrigerant, a condenser 12 that condenses a high-temperature and high-pressure gas refrigerant compressed by the compressor 11, and a liquid from the condenser 12. An expansion valve 13 that expands the refrigerant, an evaporator 14 that evaporates the liquid refrigerant expanded by the expansion valve 13, and a refrigerator control device 20 that controls each part of the refrigerator 1 are provided.

  Further, the refrigerator 10 includes a temperature sensor 33 for measuring a cold water temperature (cold water inlet temperature) Tswi supplied to the evaporator 14, and a cold water temperature (cold water outlet temperature) supplied from the evaporator 14 to an external load (not shown). A temperature sensor 34 for measuring Tswo and a flow rate sensor 36 for measuring the cold water flow rate Fs are provided. The above-described information on the cooling water inlet temperature Tcwi, the cooling water outlet temperature Tcwo, the cooling water flow rate Fc, the cooling water inlet temperature Tswi, the cooling water outlet temperature Tswo, the cooling water flow rate Fc, and the cooling water flow rate Fs is transmitted to the refrigerator controller 20. The refrigerator control device 20 performs control of each part of the refrigerator 10 based on these measured values, for example, rotation speed control of the compressor 11, opening degree control of the expansion valve 13, and the like.

  The refrigerator control device 20 and the system control device 5 (see FIG. 1) are configured to be capable of bidirectional communication. For example, the refrigerator control device 20 includes information necessary for control of the system control device 5 to be described later, such as the refrigerator load factor Lf, information indicating that it is in a restricted state, and sensor values measured by the sensors. The system control device 5 is notified at regular time intervals. The cooling water inlet temperature Tcwi, the cooling water outlet temperature Tcwo, and the cooling water flow rate Fc may be directly input to the system control device 5. Note that the information acquisition form is not limited to this example, and an appropriate technique can be used as appropriate.

  The system control device 5 and the refrigerator control device 20 include, for example, a CPU (Central Processing Unit), a memory such as a RAM (Random Access Memory), and a computer-readable recording medium. A series of processing steps for realizing various functions to be described later are recorded in a recording medium or the like in the form of a program, and the CPU reads the program into a RAM or the like to execute information processing / arithmetic processing. Thus, various functions described later are realized.

  FIG. 3 is a functional block diagram showing the cooling water flow rate control function extracted from the functions provided in the system control device 5. As shown in FIG. 3, the system control device 5 includes a storage unit 21, a target setting unit 22, and a target correction unit 24.

The storage unit 21 stores a cooling water flow rate table in which the refrigerator load factor Lf and the cooling water target flow rate are associated with each other. FIG. 4 shows an example of the cooling water flow rate table. In FIG. 4, the horizontal axis represents the refrigerator load factor [%], and the vertical axis represents the cooling water target flow rate [%]. In this embodiment, the cooling water target flow rate is expressed as a ratio to the rated flow rate, but is not limited to this example.
A plurality of cooling water flow rate tables may be provided for each cooling water temperature. In this case, the cooling water target flow rate corresponding to the refrigerator load factor Lf may be acquired with reference to the cooling water flow rate table provided corresponding to the cooling water temperature (for example, the cooling water outlet temperature Tcwo).
Furthermore, it is not limited to the aspect prepared as a table as shown in FIG. 4, For example, you may prepare as a function which contains the cooler load factor Lf as a parameter.

In the present embodiment, the cooling water target flow rate is set according to the refrigerator load factor Lf. Instead, for example, the cooling water inlet temperature, the cooling water outlet temperature, or the cooling water is used. The cooling water target flow rate may be set according to the difference between the inlet temperature and the cooling water inlet / outlet temperature. In this case, a cooling water flow rate table that associates these parameters with the cooling water target flow rate may be prepared.
The target setting unit 22 refers to the cooling water flow rate table stored in the storage unit 21, acquires the cooling water target flow rate corresponding to the current refrigerator load factor Lf, and outputs it to the target correction unit 24.

The target correction unit 24 corrects the cooling water target flow rate set by the target setting unit 22 in the increasing direction when the refrigerator 10 is in one of the preset restriction states. Whether or not the refrigerator 10 is in the restricted state can be determined based on information notified from the refrigerator control device 20.
The restricted state means, for example, current restriction, high voltage restriction, surging restriction, and the like. The current limitation is executed when the current flowing through the compressor motor is equal to or greater than a predetermined upper limit value. The high pressure restriction is executed when the refrigerant pressure of the condenser 12 is equal to or higher than a specified value. The restriction by surging is executed when a predetermined condition regarding surging is satisfied.

The target correction unit 24 increases the cooling water target flow rate according to a predetermined constant change rate. Here, the target correction unit 24 may set the change rate to be larger as the difference between the limit value in the limit state and the current measurement value is larger. For example, if the current is being limited, the change rate is increased as the difference between the current limit value and the current current value (where motor current> current limit value) is larger. As described above, the larger the deviation between the measurement value and the limit value related to the limit, the more the work of the compressor 11 can be reduced by correcting in the direction of increasing the coolant flow rate. It becomes possible to make it go to the direction which reduces an electric current. As a result, early release of the restricted state can be expected.
Further, when the refrigerator 10 is not in the restricted state, the target correction unit 24 outputs the coolant target flow rate set by the target setting unit 22 as it is without performing correction.

Next, a cooling water control procedure executed by the system control device 5 having the above configuration will be described.
The system control device 5 periodically acquires various information necessary for control from the various sensors 31 to 36 and the refrigerator control device 20. For example, refrigerator load factor Lf, information indicating whether or not it is in a restricted state, cooling water inlet temperature Tcwi, cooling water outlet temperature Tcwo, cooling water flow rate Fc, cooling water inlet temperature Tswi, cooling water outlet temperature Tswo, cooling water flow rate Fc, cooling water The flow rate Fs and the like are acquired.

  Next, the target setting unit 22 refers to the cooling water flow rate table stored in the storage unit 21, acquires the cooling water target flow rate corresponding to the current refrigerator load Lf, and outputs it to the target correction unit 24. . The target correction unit 24 determines whether or not the refrigerator 10 is in a restricted state, and if it is not in the restricted state, the target correction unit 24 outputs the cooling water target flow rate set by the target setting unit 22 without being corrected. On the other hand, when the refrigerator 10 is in the restricted state, the cooling water target flow rate is output by increasing the cooling water target flow rate at a constant rate until the current restricted state is released.

The cooling water target flow rate output from the target correction unit 24 is input to a flow rate control unit (not shown), for example. In the flow rate control unit, a control command for making the current cooling water flow rate Fc coincide with the cooling water target flow rate is generated, and the inverter 4 is driven based on the control command. As a result, the cooling water flow rate Fc can be matched with the cooling water target flow rate.
When the restricted state is released, the target correction unit 24 corrects the cooling water target flow rate at a constant rate to the cooling water target flow rate corresponding to the refrigerator load factor Lf at that time.

  As described above, according to the heat source system, the cooling water control apparatus, and the control method thereof according to the present embodiment, the cooling water flow rate in which the refrigerator load factor Lf and the cooling water target flow rate are associated by the target setting unit 22. A cooling water target flow rate corresponding to the current refrigerator load factor Lf is set using the table, and is output to the flow rate correction unit 24. When the refrigerator 10 is in a preset restriction state, the target correction unit 24 corrects the cooling water target flow rate in the increasing direction. Thus, when the refrigerator 10 is in the restricted state, a larger amount of cooling water than normal control is supplied to the refrigerator 10, so that the work amount of the compressor 11 can be reduced, and the restriction state is reduced. It becomes possible to expedite the release.

  Here, in the present embodiment, the target correction unit 24 is configured such that the cooling water inlet temperature Tcwi or the cooling water outlet temperature Tcwo or the difference between the cooling water inlet temperature and the cooling water outlet temperature is equal to or greater than a preset threshold value. In this case, the above-described cooling water target flow rate may be corrected in the increasing direction.

  For example, when the cooling water inlet temperature Tcwi, the cooling water outlet temperature Tcwo, or the difference between the cooling water inlet temperature and the cooling water outlet temperature is equal to or higher than a preset threshold value, it can be said that the above-described restricted state is easily entered. . Therefore, when such a state is detected, it is possible to reduce the frequency of entering the restricted state by performing control to increase the cooling water target flow rate.

In the present embodiment, when the refrigerator 10 is in the restricted state, the target correction unit 24 increases the cooling water target flow rate at a constant rate. Instead, the cooling water target flow rate is set to the rated value. It is good also as changing to.
In this way, by changing the cooling water target flow rate to the rated value, the flow rate of the cooling water supplied to the refrigerator 10 can be increased at a stretch. As a result, the restriction state can be released earlier than when the cooling water is gradually increased according to a constant rate.

[Second Embodiment]
Next, a heat source system, a cooling water control device thereof, and a control method thereof according to a second embodiment of the present invention will be described with reference to the drawings.
FIG. 5 is a functional block diagram of the system control apparatus 20 ′ according to the present embodiment. As shown in FIG. 5, the system control device 20 ′ according to the present embodiment further includes a table updating unit 25 that updates the cooling water flow rate table stored in the storage unit 21. Different from the embodiment. Hereinafter, the description of the present embodiment will be omitted with respect to the points common to the first embodiment, and different points will be mainly described.

When the restriction state of the refrigerator 10 is released, the table update unit 25 stores the target coolant flow rate output from the flow rate correction unit 24 and the refrigerator load factor Lf at that time. And the cooling water flow rate table stored in the memory | storage part 21 is updated using the cooling water target flow rate and refrigerator load factor Lf at this time. For example, when the cooling water target flow rate when the restriction state of the refrigerator 10 is released is a and the refrigerator load factor is b, the table update unit 25, as shown in FIG. And the point specified by the refrigerator load factor b are plotted on the table, and the cooling water flow rate table is updated by connecting this point and the end point of the current characteristic. Although FIG. 6 shows a case where the lines are connected to each other by a straight line, the lines may be connected by a gentle curve.
Thereafter, the target setting unit 22 sets the cooling water target flow rate with reference to the updated cooling water flow rate table (solid control line in FIG. 6).

  Thus, since the cooling water flow rate table is updated based on the cooling water target flow rate when the restriction state of the refrigerator 10 is released and the refrigerator load factor at that time, the flow rate is higher than the previous control thereafter. The target setting unit 22 sets the cooling water target flow rate using the cooling water flow rate table that is set to a large amount. Thereby, the work amount of the compressor 11 can be reduced, and the frequency of entering the restricted state can be reduced.

  And whenever the refrigerator 10 enters into a restriction | limiting state and it is cancelled | released, the cooling water flow rate table by the table change part 25 is updated, and it can implement | achieve the cooling water flow control which is hard to enter into a restriction | limiting state. It becomes possible.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention.
For example, in the above embodiment, the case where the system control device 5 has a function of controlling the coolant flow rate has been described. For example, the function of the coolant flow rate control is provided on the heat source device side, for example, the refrigerator control device 20. It is good.

DESCRIPTION OF SYMBOLS 1 Heat source system 2 Cooling tower 3 Water pump 4 Inverter 5 System controller 10 Refrigerator 11 Compressor 12 Condenser 13 Expansion valve 14 Evaporator 20 Refrigerator controller 21 Memory | storage part 22 Target setting part 24 Target correction | amendment part 25 Table update part 31-34 Temperature sensor 35, 36 Flow sensor

Claims (8)

Target setting means for setting the cooling water target flow rate using information in which at least one of the parameter relating to the load of the refrigerator and the parameter relating to the cooling water temperature and the cooling water target flow rate are associated;
A cooling water control device for a heat source system, comprising target correction means for correcting the cooling water target flow rate in an increasing direction when the refrigerator is in a preset restricted state.   The target correction means sets the set value of the cooling water flow rate when the cooling water inlet temperature, the cooling water outlet temperature, or the difference between the cooling water inlet temperature and the cooling water outlet temperature is equal to or greater than a preset threshold value. The cooling water control device for a heat source system according to claim 1, wherein the cooling water control device corrects in an increasing direction.   The cooling water control device for a heat source system according to claim 1 or 2, wherein the target correction means increases the cooling water target flow rate according to a constant change rate.   The cooling water control device for a heat source system according to claim 3, wherein the target correction means increases the change rate as the difference between the limit value in the limit state and the measured value increases.   The cooling water control device for a heat source system according to claim 1 or 2, wherein the target correction means changes the cooling water target flow rate to a rated value. Comprising information updating means for updating the information using the cooling water target flow rate when the restriction state of the refrigerator is released,
The said target setting means is a cooling water control apparatus of the heat source system in any one of Claims 1-5 which sets the said cooling water target flow volume using the said information after update. A refrigerator,
A heat source system comprising the cooling water control device for a heat source system according to any one of claims 1 to 6. A target setting step for setting the cooling water target flow rate using information in which at least one of the parameter relating to the load of the refrigerator and the parameter relating to the cooling water temperature is associated with the cooling water target flow rate;
A cooling water control method for a heat source system, comprising: a target correction step of correcting the cooling water target flow rate in an increasing direction when the refrigerator is in a preset restricted state.

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