JP7463065B2 - HEAT SOURCE SYSTEM CONTROL DEVICE, HEAT SOURCE SYSTEM ... CONTROL METHOD, AND HEAT SOURCE SYSTEM CONTROL PROGRAM - Google Patents

Description

This disclosure relates to a heat source system control device, a heat source system, a control method for a heat source system, and a control program for a heat source system.

In a heat source system, when the load required by the external load is below the minimum operating capacity of the heat source unit under low load conditions, or when the heat medium inlet temperature of the heat source unit is close to the heat medium outlet temperature set value, light load stop control is performed to stop the compressor and stop the heat source unit.
When the heat source unit is stopped at a light load due to the light load stop control, for example, if the heat medium is cold water, the heat source unit will not return to normal operation under normal control until the heat medium inlet temperature exceeds the heat medium outlet temperature set value by a predetermined value or more. Therefore, it takes time for the heat source unit to recover from the light load stop. Therefore, even if the load required by the external load increases suddenly, the heat source unit cannot demonstrate its capabilities until it recovers from the light load stop.
To address such a situation, for example, Patent Document 1 discloses an ultra-low load mode in which the compressor of the heat source unit continues to operate without stopping even when the required load of the external load is 10% or less of the capacity of the heat source unit.

JP 2009-2635 A

However, in the invention disclosed in Patent Document 1, when the chilled water inlet temperature falls below the minimum temperature allowed by the heat source system, the heat source unit is shut down under light load, and there is a problem in that it takes time for the heat source unit to return to normal operation after it has been shut down under light load.

The present disclosure has been made in consideration of these circumstances, and aims to provide a heat source system control device, a heat source system, a control method for a heat source system, and a control program for a heat source system that enable forced return to normal control from a light load stop.

In order to solve the above problems, the control device of a heat source system disclosed herein is a control device for a heat source system including a plurality of heat source machines, and an inlet temperature sensor for detecting a heat medium inlet temperature, which is the heat medium temperature on the inlet side of the heat source machine, and an outlet temperature sensor for detecting a heat medium outlet temperature, which is the heat medium temperature on the outlet side, are installed for each of the heat source machines, and the control device acquires the heat medium inlet temperature and the heat medium outlet temperature set value, which is the set value of the heat medium outlet temperature of the heat source machine, is set to an initial value, and when the heat medium inlet temperature falls below a light-load stop temperature, the heat source machine enters a light-load stop state in which the compressor of the heat source machine stops, and when during the light-load stop, the heat medium inlet temperature is greater than the light-load stop temperature and exceeds a light-load return temperature, which is a value obtained by adding a predetermined value to the heat medium outlet temperature set value, the heat source machine enters a light-load return state in which the compressor of the heat source machine starts, and when any of the heat source machines enters a light-load stop state, forced return control is performed in which the heat medium outlet temperature set value is changed to a lower limit value which is a value smaller than the initial value.

The heat source system disclosed herein also includes multiple heat source units and the above-mentioned control device.

The control method for a heat source system disclosed herein is a control method for a heat source system including a plurality of heat source machines, in which an inlet temperature sensor for detecting a heat medium inlet temperature, which is the heat medium temperature on the inlet side of the heat source machine, and an outlet temperature sensor for detecting a heat medium outlet temperature, which is the heat medium temperature on the outlet side, are installed for each of the heat source machines, and when the heat medium inlet temperature falls below a light-load stop temperature, the heat source machine enters a light-load stop state in which the compressor of the heat source machine stops, and when the heat medium inlet temperature during the light-load stop state is greater than the light-load stop temperature and exceeds a light-load return temperature, which is a value obtained by adding a predetermined value to the heat medium outlet temperature set value, the heat source machine enters a light-load return state in which the compressor of the heat source machine starts, and the control method includes a step of acquiring the heat medium inlet temperature and the heat medium outlet temperature, a step of setting an initial value for the heat medium outlet temperature set value, which is the set value for the heat medium outlet temperature of the heat source machine, and a step of performing forced return control in which the heat medium outlet temperature set value is changed to a lower limit value, which is a value smaller than the initial value, when any of the heat source machines enters a light-load stop state.

The control program for the heat source system disclosed herein is a control program for a heat source system including a plurality of heat source machines, in which an inlet temperature sensor for detecting a heat medium inlet temperature, which is the heat medium temperature on the inlet side of the heat source machine, and an outlet temperature sensor for detecting a heat medium outlet temperature, which is the heat medium temperature on the outlet side, are installed for each of the heat source machines, and when the heat medium inlet temperature falls below a light-load stop temperature, the heat source machine enters a light-load stop state in which the compressor of the heat source machine stops, and when the heat medium inlet temperature during the light-load stop state is greater than the light-load stop temperature and exceeds a light-load return temperature, which is a value obtained by adding a predetermined value to the heat medium outlet temperature set value, the heat source machine enters a light-load return state in which the compressor of the heat source machine starts, and the control program has the steps of acquiring the heat medium inlet temperature and the heat medium outlet temperature, setting an initial value for the heat medium outlet temperature set value, which is the set value for the heat medium outlet temperature of the heat source machine, and performing forced return control to change the heat medium outlet temperature set value to a lower limit value, which is a value smaller than the initial value, when any of the heat source machines enters a light-load stop state.

According to the present disclosure, when the heat source unit is stopped at a light load, the heat medium outlet temperature setting value is changed to the lower limit value, so that the heat source unit that has been stopped at a light load can be forcibly returned to a light load.

FIG. 1 is a schematic configuration diagram of a heat source system according to some embodiments of the present disclosure. FIG. 2 is a block diagram illustrating a control device of a heat source system according to some embodiments of the present disclosure. 11 is a flowchart showing a return control from a light load stop as a reference example. 11 is a flowchart illustrating a forced return control according to some embodiments of the present disclosure. 4 is a time chart illustrating forced return control according to some embodiments of the present disclosure. 11 is a flowchart illustrating a forced return control according to some embodiments of the present disclosure. 11 is a flowchart illustrating a forced return control according to some embodiments of the present disclosure. 11 is a flowchart illustrating a forced return control according to some embodiments of the present disclosure.

Below, an embodiment of a heat source system control device, a heat source system, a control method for a heat source system, and a control program for a heat source system according to the present disclosure will be described with reference to the drawings.

First Embodiment
FIG. 1 shows a schematic configuration of one aspect of a heat source system according to some embodiments of the present disclosure.
As shown in FIG. 1, the heat source system 1 mainly comprises a chiller (heat source unit) 2, a pump 3, a supply header 4, a return header 5, an external load 6, a bypass valve 7, an inlet temperature sensor 8, and an outlet temperature sensor 9.
The refrigerator 2 is composed of refrigerators 2a, 2b, 2c, and 2d. Each of the refrigerators 2a, 2b, 2c, and 2d is installed in parallel with an external load 6.
The pump 3 is composed of cold water pumps 3a, 3b, 3c and 3d.
In the following description, when the refrigerators 2a, 2b, 2c, and 2d are to be distinguished from one another, any of the letters a to d will be added to the end of the reference numerals, and when the refrigerators 2a, 2b, 2c, and 2d are not to be distinguished from one another, the letters a to d will be omitted. Similarly, when the refrigerators 2a, 2b, 2c, and 2d are not to be distinguished from one another, the letters a to d will be omitted.

When operating in cold heat output mode, cold water pumps 3a, 3b, 3c, and 3d that pump cold water are installed upstream of each of the chillers 2a, 2b, 2c, and 2d, respectively. These cold water pumps 3a, 3b, 3c, and 3d pump cold water from the return header 5 to each of the chillers 2a, 2b, 2c, and 2d.

The supply header 4 collects the cold water that has passed through each of the chillers 2a, 2b, 2c, and 2d. The cold water collected in the supply header 4 is supplied to an external load 6. The cold water that has been used for air conditioning or the like in the external load 6 and has been heated is sent to the return header 5. The cold water is branched in the return header 5 and sent to each of the chillers 2a, 2b, 2c, and 2d as described above.

A bypass valve 7 is provided on the bypass line that sends the cold water collected in the supply header 4 directly to the return header 5 without passing through the external load 6. By adjusting the opening of the bypass valve 7, the amount of cold water supplied to the external load 6 can be adjusted.

Upstream of each chiller 2a, 2b, 2c, and 2d from the perspective of the chilled water flow, inlet temperature sensors 8a, 8b, 8c, and 8d are installed to detect the chilled water inlet temperature (heat medium inlet temperature), which is the chilled water temperature (heat medium temperature) on the inlet side of the chiller 2. Also, downstream of each chiller 2a, 2b, 2c, and 2d from the perspective of the chilled water flow, outlet temperature sensors 9a, 9b, 9c, and 9d are installed to detect the chilled water outlet temperature (heat medium outlet temperature), which is the chilled water temperature (heat medium temperature) on the outlet side of the chiller 2.

FIG. 2 shows a block diagram illustrating a control device of a heat source system according to some embodiments of the present disclosure.
2, chiller control devices 10a, 10b, 10c, and 10d, which are control devices for the chillers 2a, 2b, 2c, and 2d, are connected to a control device 20. The control device 20 is, for example, a device that controls the entire heat source system 1. The control device 20 controls the chillers 2a, 2b, 2c, and 2d via the chiller control devices 10a, 10b, 10c, and 10d, and also performs, for example, control of the rotation speeds of chilled water pumps 3a, 3b, 3c, and 3d, and acquisition of chilled water inlet temperatures detected by inlet temperature sensors 8a, 8b, 8c, and 8d and chilled water outlet temperatures detected by outlet temperature sensors 9a, 9b, 9c, and 9d.

The control device 20 and the refrigeration machine control devices 10a, 10b, 10c, and 10d are, for example, MPUs (Micro Processing Units), and have computer-readable non-transitory recording media on which programs for executing each process are recorded, and each process is realized by a CPU (Central Processing Unit) reading the programs recorded on the recording media into a main storage device such as a RAM (Random Access Memory) and executing them. Examples of computer-readable recording media include magnetic disks, magneto-optical disks, and semiconductor memories.
The control device 20 and the refrigerator control devices 10a, 10b, 10c, and 10d may be embodied by a single MPU, or may be embodied by individual MPUs.

FIG. 3 is a flow chart showing a return control from a light load stop as a reference example.
In step S301, it is determined whether the operating refrigerator 2 is in a light load stop state.
If it is determined that the vehicle is in a light-load stop state, the process proceeds to step S302. If it is determined that the vehicle is not in a light-load stop state, the process proceeds to step S306, where normal control, not light-load stop control, is performed.

If it is determined in step S301 that the refrigerator 2 is in a light-load stopped state, the refrigerator 2 is placed in a light-load stopped state with the compressor stopped (S302).

Next, the control device 20 acquires the chilled water inlet temperature Tin of the chiller 2 from the inlet temperature sensor 8 via the chiller control device 10 (S305), and determines whether the chilled water inlet temperature Tin is equal to or higher than the light-load return temperature Ta (S303). Here, the light-load return temperature Ta is a value set to determine that the chilled water inlet temperature has risen during a light-load stop and reached a temperature at which normal control can be returned from the light-load stop, and is a value obtained by adding a predetermined value α to the chilled water outlet temperature set value (heat medium outlet temperature set value) Tset of the chiller 2. The chilled water outlet temperature set value Tset is set to an initial value Tinit. The initial value Tinit is a value that can be set arbitrarily. The predetermined value α is a value that can be set arbitrarily, for example, 3.

If it is determined in step S303 that the chilled water inlet temperature Tin is equal to or higher than the light-load return temperature Ta, the chiller 2 is deemed capable of returning from the light-load stop to normal operation under normal control, and returns from the light-load stop (S304) and returns to normal control (S306).

On the other hand, if it is determined in step S303 that the chilled water inlet temperature Tin is less than the light load return temperature Ta, the process returns to step S302 and the chiller 2 continues to be in the light load stopped state.

As such, with conventional light-load stop control, it was not possible to return from the light-load stop state until the chilled water inlet temperature reached the light-load return temperature.

Figure 4 shows a flow chart of forced return control according to some embodiments of the present disclosure.

In step S401, it is determined whether the operating refrigerator 2 has been stopped under a light load.
With regard to whether or not a light-load stop has been performed, it is determined that a light-load stop has been performed when, for example, the chilled water inlet temperature Tin of the chiller 2 falls below a light-load stop temperature Tb. Here, the light-load stop temperature Tb is a value set for determining that the chilled water inlet temperature drops during normal operation under normal control and reaches a temperature at which a light-load stop occurs, and is a value obtained by adding a predetermined value β to the chilled water outlet temperature set value Tset of the chiller 2. The predetermined value β is a value that can be set arbitrarily and is smaller than the predetermined value α. The predetermined value β is set to, for example, 1.
If it is determined that the light-load stop has been performed, the process proceeds to step S402. If it is determined that the light-load stop has not been performed, the process proceeds to step S407, where normal control, which is not the light-load stop control, is performed.

When it is determined in step S401 that the chiller 2 has been stopped under light load, the control device 20 changes the chilled water outlet temperature set value Tset of the chiller 2 (chiller 2a in this example) corresponding to the light load stop from the initial value Tinit of the chilled water outlet temperature set value to the lower limit value Tsmin (forced return control) (S402) via the chiller control device 10. Here, the lower limit value Tsmin is the lower limit value of the chilled water outlet temperature set value Tset and is a value smaller than the initial value Tinit.
In this way, by setting the chilled water outlet temperature set value Tset to the lower limit value Tsmin which is a value smaller than the initial value Tinit, the light-load return temperature Ta=Tset+α and the light-load stop temperature Tb=Tset+β also become smaller.

Then, the process proceeds to step S403, where the control device 20 determines whether the chiller 2a has returned to a light load state. Specifically, the control device 20 acquires the chilled water inlet temperature Tin (Tina) of the chiller 2a via the chiller control device 10a (S406), and determines whether the chilled water inlet temperature Tin is equal to or higher than the light load return temperature Ta.

If it is determined in step S403 that the chilled water inlet temperature Tin is equal to or higher than the light load return temperature Ta, the system will return to light load and the process will transition to step S405.

In step S405, the control device 20 changes the chilled water outlet temperature set value Tset of the chiller 2a from the lower limit value Tsmin to the initial value Tinit via the chiller control device 10a.

When the chilled water outlet temperature set value Tset of the chiller 2a is changed to the initial value Tinit, the process transitions to step S407. The forced return control according to this embodiment is terminated, and the chiller 2a returns to normal operation under normal control.

On the other hand, if it is determined in step S403 that the cold water inlet temperature Tin falls below the light load return temperature Ta, the control device 20 determines whether or not a predetermined time has elapsed since the light load stop was detected in step S401 (S404). Here, the predetermined time is a value that can be set arbitrarily, and is set to, for example, 300 seconds.

If it is determined in step S404 that a predetermined time or more has elapsed since the light-load stop was detected, the process proceeds to step S405. In step S405, the chilled water outlet temperature set value Tset is changed from the lower limit value Tsmin to the initial value Tinit. If the chilled water inlet temperature Tin does not increase and a predetermined time has elapsed without reaching the light-load return temperature Ta, the forced return control according to this embodiment is terminated, and a return from the light-load stop by normal control is performed (S407).
Here, when returning from a light load stop, if the chilled water outlet temperature setting value Tset is immediately changed from the lower limit value Tsmin to the initial value Tinit, there is a possibility that the light load stop will occur again. Therefore, in this embodiment, the chilled water outlet temperature setting value Tset may be gradually increased at a predetermined rate until it reaches the initial value Tinit.

On the other hand, if it is determined in step S404 that the time since the light load stop was detected is less than the predetermined time, the process returns to step S403, and the determination as to whether or not to resume is made again.

FIG. 5 is a time chart showing the forced return control according to some embodiments of the present disclosure.
In Figure 5, the vertical axis is temperature (°C) and the horizontal axis is time (s). The thick line indicates the chilled water inlet temperature Tin of the chiller 2, the solid line indicates the chilled water outlet temperature set value Tset, the dashed line indicates the light-load stop temperature Tb, and the dashed line indicates the light-load return temperature Ta.

When normal operation is performed under normal control, the chilled water outlet temperature set value Tset is set to an initial value Tinit. When normal control is performed, the chilled water inlet temperature Tin drops (during the period from time t0 to t1), and at time t1 the chilled water inlet temperature Tin reaches the light load stop temperature Tb.

When the chilled water inlet temperature Tin reaches the light-load stop temperature Tb, the chiller 2 is stopped at light load. When a light-load stop is detected, the control device 20 changes the chilled water outlet temperature set value Tset from the initial value Tinit to the lower limit value Tsmin (Tsmin < Tinit). Similarly, the light-load stop temperature Tb (Tset + β) is changed to Tsmin + β, and the light-load return temperature Ta (Tset + α) is changed to Tsmin + α.

During the light load stop, the compressor of the refrigerator 2 is stopped, so the chilled water inlet temperature Tin starts to rise gradually. Then, at time t2, the chilled water inlet temperature Tin reaches the light load return temperature Ta = Tsmin + α, and the refrigerator returns to light load from the light load stop.

The actions and effects of the heat source system control device, the heat source system, the control method for a heat source system, and the control program for a heat source system according to the present embodiment described above will be described.
In the control device 20 of the heat source system 1 according to this embodiment, when any of the chillers 2 reaches a light load stop, forced return control is performed to change the chilled water outlet temperature setting value to a lower limit value that is a value smaller than the initial value.
If the chilled water outlet temperature set value is changed to the lower limit value when any of the chillers 2 reaches a light-load stop, the light-load return temperature is also lowered by lowering the chilled water outlet temperature set value. When forced return control is performed to lower the chilled water outlet temperature set value, the chilled water inlet temperature is more likely to reach the light-load return temperature, making it possible to reach light-load return more quickly compared to control that does not change the chilled water outlet temperature set value.
Therefore, according to the control device 20 of the heat source system 1 of this embodiment, even if the load suddenly increases when the light-load stop state is reached, the system can quickly recover from the light-load stop state and the chiller 2 can demonstrate its capacity.

In addition, in the control device 20 of the heat source system 1 according to this embodiment, when light load recovery is achieved by the forced return control, the chilled water outlet temperature set value changed by the forced return control is gradually increased at a predetermined rate to return it to the initial value.
If the chilled water outlet temperature setting value is returned to the initial value immediately after returning from a light-load stop, the chilled water inlet temperature will approach the light-load stop temperature, which is based on the chilled water outlet temperature setting value, and in some cases, a light-load stop may occur again.
Therefore, according to the control device 20 of the heat source system 1 of this embodiment, the cold water outlet temperature setting value is not returned to the initial value immediately after recovering from a light-load stop, but is gradually increased at a predetermined rate and then returned to the initial value, thereby preventing the cold water inlet temperature from falling below the light-load stop temperature and suppressing the system from reaching a light-load stop again.

Second Embodiment
In the first embodiment, the heat transfer medium outlet temperature setting value is changed to the lower limit value, but in this embodiment, it is changed to a value using the difference between the light load return temperature and the heat transfer medium inlet temperature. Since other points are the same as in the first embodiment, the same reference numerals are used for the same configurations and the description thereof is omitted.

Figure 6 shows a flow chart of forced return control according to some embodiments of the present disclosure.

In step S601, it is determined whether the operating refrigerator 2 has been stopped under a light load.
If it is determined that the light load has been stopped, the process proceeds to step S602. If it is determined that the light load has not been stopped, the process proceeds to step S608, where normal control, not light load stop control, is performed.

If it is determined in step S601 that the chiller 2 has stopped under light load, the process proceeds to step S602. The control device 20 acquires the chilled water inlet temperature Tin (Tina) of the chiller 2a via the chiller control device 10a (S607), and calculates the difference ΔT = Ta - Tin between the light load return temperature Ta and the chilled water inlet temperature Tin.

Next, the process proceeds to step S603, where the control device 20 calculates a value ΔT' = ΔT + γ by adding the difference ΔT calculated in step S602 to the first correction value γ. Furthermore, the control device 20 changes the chilled water outlet temperature set value Tset from the initial value Tinit to Tinit - ΔT' (forced return control). Here, the first correction value γ is a value that can be set arbitrarily, for example, 1°C.

By changing the chilled water outlet temperature set value Tset in this manner, the light-load return temperature Ta falls below the chilled water inlet temperature Tin. As a result, the chilled water inlet temperature Tin becomes equal to or higher than the light-load return temperature Ta, and the chiller 2a returns to light load from light-load stop.
Moreover, by lowering the chilled water outlet temperature set value Tset by ΔT' obtained by adding the first correction value γ instead of the difference ΔT, it is possible to prevent the system from immediately reaching a light load stop again.

Next, the process proceeds to step S604, where the control device 20 determines whether the chiller 2a has returned to the light load state.
Regarding whether or not the chiller 2 has returned to light load, it is determined that the chiller 2 has returned to light load, for example, when the chilled water inlet temperature Tin of the chiller 2 exceeds a light load return temperature Ta.
If it is determined that the light load has returned, the process proceeds to step S606. If it is determined that the light load has not returned, the process proceeds to step S605.

If it is determined in step S604 that the light load has returned, the controller 20 changes the chilled water outlet temperature set value Tset of the chiller 2a from Tinit-ΔT' to the initial value Tinit (S606).
Next, the process proceeds to step S608, where the forced return control according to this embodiment is ended and normal control is performed.

On the other hand, if it is determined in step S604 that the light load has not returned, the control device 20 determines whether a predetermined time or more has elapsed since the light load stop was detected in step S601 (S605).

If it is determined in step S605 that a predetermined time or more has elapsed since the chilled water outlet temperature set value Tset was changed, the process proceeds to step S606. In step S606, the chilled water outlet temperature set value Tset of the chiller 2a is changed from Tinit-ΔT' to the initial value Tinit. If a predetermined time has elapsed without achieving light load recovery, the forced recovery control according to this embodiment is terminated, and recovery from light load stoppage using normal control is performed (S607).

On the other hand, if it is determined in step S605 that the time elapsed since the chilled water outlet temperature set value Tset was changed is less than the predetermined time, the determination is repeated until the predetermined time or more has elapsed.

The actions and effects of the heat source system control device, the heat source system, the control method for a heat source system, and the control program for a heat source system according to the present embodiment described above will be described.
In the control device 20 of the heat source system 1 in this embodiment, when any of the chillers 2 reaches a light load, forced return control is performed to change the chilled water outlet temperature setting value to a value lowered from the initial value by the difference between the light load return temperature and the chilled water inlet temperature of the chiller 2 plus a first correction value.
When any of the chillers 2 reaches a light-load stop, if the chilled water outlet temperature set value is changed to a value lowered from the initial value by the difference between the light-load return temperature and the chilled water inlet temperature of the chiller 2 plus the first correction value, the light-load return temperature is also lowered by lowering the chilled water outlet temperature set value. When forced return control is performed to lower the chilled water outlet temperature set value, the chilled water inlet temperature is more likely to reach the light-load return temperature, making it possible to reach light-load return more quickly compared to normal control, which does not change the chilled water outlet temperature set value.
Therefore, according to the control device 20 of the heat source system 1 of this embodiment, even if the load suddenly increases when the light-load stop state is reached, the system can quickly recover from the light-load stop state and the chiller 2 can demonstrate its capacity.

Third Embodiment
In the first embodiment, when the light load is restored, the heat transfer medium outlet temperature setting value is changed to the initial value, but in this embodiment, the heat transfer medium outlet temperature setting value is changed to a value based on the heat transfer medium inlet temperature and the light load stop temperature. Since other points are the same as in the first embodiment, the same reference numerals are used for the same configurations and the description thereof is omitted.

7 and 8 are flow charts showing forced return control according to some embodiments of the present disclosure.

In step S701 of FIG. 7, it is determined whether the operating refrigerator 2 has been stopped under a light load.
If it is determined that the light-load stop has occurred, the process proceeds to step S702. If it is determined that the light-load stop has not occurred, the process proceeds to step S710 in Fig. 8, where normal control, not light-load stop control, is performed.

If it is determined in step S701 of FIG. 7 that the chiller 2 has been stopped under light load, the control device 20 changes the chilled water outlet temperature set value Tset of the chiller 2 (here, chiller 2a) that is in the light load stop state from the initial value Tinit of the chilled water outlet temperature set value to the lower limit value Tsmin via the chiller control device 10 (forced return control) (S702).
In this manner, by setting the chilled water outlet temperature set value Tset to the lower limit value Tsmin, which is a value smaller than the initial value Tinit, the light-load return temperature Ta and the light-load stop temperature Tb also become smaller in value.

Then, the process proceeds to step S703, where the control device 20 determines whether the chiller 2a has returned to a light load state. Specifically, the control device 20 acquires the chilled water inlet temperature Tin (Tina) of the chiller 2a via the chiller control device 10a (S706), and determines whether the chilled water inlet temperature Tin is equal to or higher than the light load return temperature Ta.

If it is determined in step S703 that the chilled water inlet temperature Tin is equal to or higher than the light load return temperature Ta, the system will return to light load and the process will transition to step S707 in FIG. 8.

In step S707 of FIG. 8, the control device 20 calculates the settable upper limit value Tmax of the chilled water outlet temperature set value Tset. The settable upper limit value Tmax is a value that is set to prevent the chilled water inlet temperature Tin from immediately reaching the light-load stop temperature Tb and causing a light-load stop again when the chilled water outlet temperature set value Tset is changed from the lower limit value Tsmin to the initial value Tinit.

The settable upper limit value Tmax is expressed by the following formula (1).
[Equation 1]
Tmax = Tset + (Tin - Tb) - ζ
= Tset + {Tin - (Tset + β)} - ζ
= Tin - β - ζ ... (1)

In formula (1), ζ is a second correction value, which can be set arbitrarily, for example, to 0.5°C.
As shown in formula (1), the settable upper limit value Tmax is calculated from the chilled water inlet temperature Tin and the light-load stop temperature Tb. By subtracting the second correction value ζ as a margin, it is possible to prevent the engine from immediately returning to a light-load stop state again after recovering from the light-load stop state.

Next, the process proceeds to step S708, where the control device 20 changes the chilled water outlet temperature set value Tset of the chiller 2a to the settable upper limit value Tmax. The chilled water outlet temperature set value Tset, which was lowered from the initial value Tinit to the lower limit value Tsmin for the forced return control, is raised to the settable upper limit value Tmax calculated by formula (1). Rather than immediately raising the value of the chilled water outlet temperature set value Tset from the lower limit value Tsmin to the initial value Tinit, the value of the chilled water outlet temperature set value Tset is raised in accordance with the change in the chilled water inlet temperature Tin.

Next, the process proceeds to step S709, where the control device 20 determines whether the chilled water outlet temperature set value Tset has reached the initial value Tinit. If it is determined that the chilled water outlet temperature set value Tset has reached the initial value Tinit, the process proceeds to step S710. The forced return control according to this embodiment is terminated, and normal control is performed.

On the other hand, if it is determined in step S709 that the chilled water outlet temperature set value Tset has not reached the initial value Tinit, the process returns to step S707. By repeating the processes of steps S707 to S709, the chilled water outlet temperature set value Tset, which has been lowered to the lower limit value Tsmin by the forced return control, is gradually increased in temperature. The processes of steps S707 to S709 are repeated until the chilled water outlet temperature set value Tset reaches the initial value Tinit.

On the other hand, if it is determined in step S703 of FIG. 7 that the chilled water inlet temperature Tin falls below the light load return temperature Ta, the control device 20 determines whether a predetermined time or more has elapsed since the light load stop was detected in step S701 (S704).

If it is determined in step S704 that a predetermined time has elapsed since the light-load stop was detected, the process proceeds to step S705. In step S705, the chilled water outlet temperature set value Tset is changed from the lower limit value Tsmin to the initial value Tinit. If the chilled water inlet temperature Tin does not increase and a predetermined time has elapsed without reaching the light-load return temperature Ta, the forced return control according to this embodiment is terminated, and the system is returned from the light-load stop by normal control (S710 in FIG. 8).

On the other hand, if it is determined in step S704 of FIG. 7 that the time since the light load stop was detected is less than the predetermined time, the process returns to step S703, and the determination as to whether or not to resume is made again.

The actions and effects of the heat source system control device, the heat source system, the control method for a heat source system, and the control program for a heat source system according to the present embodiment described above will be described.
In the control device 20 of the heat source system 1 in this embodiment, the chilled water outlet temperature setting value is increased to the settable upper limit value of the chilled water outlet temperature setting value, and the settable upper limit value is set to a value obtained by subtracting a second correction value from the sum of the chilled water outlet temperature setting value and the difference between the chilled water inlet temperature and the light load stop temperature.
According to the control device 20 of the heat source system 1 of this embodiment, by subtracting the second correction value as a margin, it is possible to prevent a light-load stop from occurring again before the chilled water outlet temperature set value is returned to the initial value. Since the chilled water inlet temperature gradually increases due to the return to the light load, the settable upper limit value of the chilled water outlet temperature set value also gradually increases to the initial value, making it possible to prevent a light-load stop from occurring.

Although each embodiment of the present disclosure has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment.
In the above-described embodiments, the refrigerators 2a, 2b, 2c, and 2d are described as refrigerators that cool cold water, i.e., cold heat output, but they may be refrigerators that heat cold water, i.e., hot heat output. They may also have both a cooling function and a heating function. The heat medium may be a system that cools or heats another heat medium, such as brine, instead of cold water.
In the case of heat output, the temperature handling is the opposite of that in the case of cold output.

Furthermore, each embodiment of the present disclosure is particularly suitable for performing forced rotation control, which forcibly operates the heat source unit in rotation. When forced rotation control is being performed in the heat source system 1, forced return control may be performed, and when forced rotation control is not being performed, forced return control may not be performed and normal light load stop control may be performed.

The heat source system control device, the heat source system, the control method for a heat source system, and the control program for a heat source system described in each of the embodiments described above can be understood, for example, as follows.
The control device (20) of the heat source system (1) according to the present disclosure is a control device (20) of a heat source system (1) including a plurality of heat source units (2), in which an inlet temperature sensor (8) for detecting a heat medium inlet temperature, which is the heat medium temperature on the inlet side of the heat source unit (2), and an outlet temperature sensor (9) for detecting a heat medium outlet temperature, which is the heat medium temperature on the outlet side, are installed for each of the heat source units (2), and the control device (20) acquires the heat medium inlet temperature and the heat medium outlet temperature, and detects the set value of the heat medium outlet temperature of the heat source unit (2). An initial value is set for the heat medium outlet temperature setting value, and when the heat medium inlet temperature falls below a light-load stop temperature, the heat source unit (2) enters a light-load stop state in which the compressor of the heat source unit (2) stops, and when the heat medium inlet temperature exceeds a light-load return temperature that is greater than the light-load stop temperature during the light-load stop state, the heat source unit (2) enters a light-load return state in which the compressor of the heat source unit (2) starts up, and when any of the heat source units (2) enters a light-load stop state, forced return control is performed in which the heat medium outlet temperature setting value is changed to a lower limit value that is a value smaller than the initial value.

In the present disclosure, when any of the heat source units (2) reaches a light load stop, forced return control is performed to change the heat medium outlet temperature setting value to a lower limit value that is a value smaller than the initial value.
If the heat medium outlet temperature setting value is changed to the lower limit value when any of the heat source units (2) reaches a light-load stop, the light-load return temperature is also lowered by lowering the heat medium outlet temperature setting value. When forced return control is performed to lower the heat medium outlet temperature setting value, the heat medium inlet temperature is more likely to reach the light-load return temperature, making it possible to return to light load more quickly compared to normal control in which the heat medium outlet temperature setting value is not changed.
Therefore, according to the present disclosure, even if the load suddenly increases after the light-load stop, the heat source unit (2) can quickly recover from the light-load stop and demonstrate its capabilities.

The control device (20) of the heat source system (1) according to the present disclosure is a control device (20) of a heat source system (1) equipped with a plurality of heat source machines (2), in which an inlet temperature sensor (8) for detecting a heat medium inlet temperature, which is the heat medium temperature on the inlet side of the heat source machine (2), and an outlet temperature sensor (9) for detecting a heat medium outlet temperature, which is the heat medium temperature on the outlet side, are installed for each of the heat source machines (2), and the control device (20) acquires the heat medium inlet temperature and the heat medium outlet temperature, and sets an initial value for the heat medium outlet temperature setting value, which is the setting value for the heat medium outlet temperature of the heat source machine (2), When the heat medium inlet temperature falls below the light-load stop temperature, the heat source unit (2) enters a light-load stop state in which the compressor of the heat source unit (2) stops, and when the heat medium inlet temperature exceeds a light-load return temperature, which is a value greater than the light-load stop temperature, during the light-load stop state, the heat source unit (2) enters a light-load return state in which the compressor of the heat source unit (2) starts up. When any of the heat source units (2) enters a light-load stop state, forced return control is performed to change the heat medium outlet temperature setting value to a value lowered from the initial value by the difference between the light-load return temperature and the heat medium inlet temperature of the heat source unit (2) plus a first correction value.

In the present disclosure, when any of the heat source units (2) reaches a light load, forced return control is performed to change the heat medium outlet temperature setting value to a value lowered from the initial value by the difference between the light load return temperature and the heat medium inlet temperature of the heat source unit (2) plus a first correction value.
When any of the heat source units (2) reaches a light-load stop, if the heat medium outlet temperature set value is changed to a value lowered from the initial value by the difference between the light-load return temperature and the heat medium inlet temperature of the heat source unit (2) plus the first correction value, the light-load return temperature is also lowered by lowering the heat medium outlet temperature set value. When forced return control is performed to lower the heat medium outlet temperature set value, the heat medium inlet temperature is more likely to reach the light-load return temperature, making it possible to return to light load more quickly compared to normal control in which the heat medium outlet temperature set value is not changed.
Therefore, according to the present disclosure, even if the load suddenly increases after the light-load stop, the heat source unit (2) can quickly recover from the light-load stop and demonstrate its capabilities.

The control device (20) of the heat source system (1) according to the present disclosure performs forced return control when forced rotation control is being performed to forcibly operate the heat source unit (2) in rotation, and performs normal control to stop the unit under light load when the forced rotation control is not being performed, and does not perform forced return control.

In the present disclosure, the forced return control is performed only when the forced rotation control is being performed.
When forced rotation control is being performed, when switching (rotating) a heat source unit (2) to be stopped with a heat source unit (2) to be operated, a period occurs during which the heat source unit (2) to be stopped and the heat source unit (2) to be operated operate simultaneously. At this time, the capacity of the operating heat source unit (2) exceeds the required capacity of the external load (6), and the heat medium inlet temperature drops, which may result in a light load stop.
According to the present disclosure, even if the load increases suddenly in a light-load stopped state, the heat source unit (2) can quickly recover from the light-load stopped state and demonstrate its capabilities.

When the control device (20) of the heat source system (1) disclosed herein returns to a light load through forced return control, the control device (20) gradually increases the heat medium outlet temperature setting value changed through forced return control at a predetermined rate until it reaches the initial value.

In the present disclosure, when the forced return control returns to a light load, the heat medium outlet temperature setting value changed by the forced return control is gradually increased at a predetermined rate to return to the initial value.
If the heat transfer medium outlet temperature setting value is returned to the initial value immediately after returning from a light-load shutdown, the heat transfer medium inlet temperature will approach the light-load shutdown temperature, which is based on the heat transfer medium outlet temperature setting value, and in some cases, the light-load shutdown may occur again.
According to the present disclosure, the heat transfer medium outlet temperature setting value is not returned to the initial value immediately after recovery from a light-load stop, but is gradually increased at a predetermined rate and then returned to the initial value, thereby preventing the heat transfer medium inlet temperature from falling below the light-load stop temperature and suppressing the occurrence of a light-load stop again.

The control device (20) of the heat source system (1) according to the present disclosure increases the heat medium outlet temperature setting value up to the settable upper limit of the heat medium outlet temperature setting value, and the settable upper limit is a value obtained by subtracting a second correction value from the sum of the heat medium outlet temperature setting value and the difference between the heat medium inlet temperature and the light load stop temperature.

In the present disclosure, the heat medium outlet temperature setting value is increased to the settable upper limit value of the heat medium outlet temperature setting value, and the settable upper limit value is a value obtained by subtracting a second correction value from the sum of the heat medium outlet temperature setting value and the difference between the heat medium inlet temperature and the light load stop temperature.
According to the present disclosure, by subtracting the second correction value as a margin, it is possible to prevent the system from becoming light-load stopped again before the heat medium outlet temperature setting value is returned to its initial value. Since the heat medium inlet temperature gradually rises due to the return to light load, the settable upper limit of the heat medium outlet temperature setting value also gradually rises to its initial value, making it possible to prevent the system from becoming light-load stopped.

The heat source system (1) according to the present disclosure includes a plurality of heat source units (2) and the aforementioned control device (20).

The control method for a heat source system (1) according to the present disclosure is a control method for a heat source system (1) equipped with a plurality of heat source machines (2), in which an inlet temperature sensor (8) for detecting a heat medium inlet temperature, which is the heat medium temperature on the inlet side of the heat source machine (2), and an outlet temperature sensor (9) for detecting a heat medium outlet temperature, which is the heat medium temperature on the outlet side, are installed for each of the heat source machines (2), and when the heat medium inlet temperature falls below the light-load stop temperature, the heat source machine (2) enters a light-load stop state in which the compressor of the heat source machine (2) stops, and during the light-load stop state, When the heat medium inlet temperature exceeds a light-load return temperature that is a value greater than the light-load stop temperature, the compressor of the heat source unit (2) starts, resulting in a light-load return, and the system includes a process of acquiring the heat medium inlet temperature and the heat medium outlet temperature, a process of setting an initial value for the heat medium outlet temperature setting value, which is the setting value for the heat medium outlet temperature of the heat source unit (2), and a process of performing forced return control to change the heat medium outlet temperature setting value to a lower limit value that is a value smaller than the initial value when any of the heat source units (2) reaches a light-load stop.

A control program for a heat source system (1) having a plurality of heat source machines (2), in which an inlet temperature sensor (8) for detecting a heat medium inlet temperature, which is the heat medium temperature on the inlet side of the heat source machine (2), and an outlet temperature sensor (9) for detecting a heat medium outlet temperature, which is the heat medium temperature on the outlet side, are installed for each of the heat source machines (2), and when the heat medium inlet temperature falls below a light-load stop temperature, the heat source machine (2) enters a light-load stop state in which the compressor of the heat source machine (2) stops, and when the heat medium inlet temperature exceeds a light-load return temperature, which is a value greater than the light-load stop temperature, during the light-load stop state, the heat source machine (2) enters a light-load return state in which the compressor of the heat source machine (2) starts, and includes a step of acquiring the heat medium inlet temperature and the heat medium outlet temperature, a step of setting an initial value for the heat medium outlet temperature setting value, which is the setting value of the heat medium outlet temperature of the heat source machine (2), and a step of performing forced return control to change the heat medium outlet temperature setting value to a lower limit value, which is a value smaller than the initial value, when any of the heat source machines (2) enters a light-load stop state.

1 Heat source system 2, 2a, 2b, 2c, 2d Refrigeration machine (heat source machine)
3 Pumps 3a, 3b, 3c, 3d Chilled water pump 4 Supply header 5 Return header 6 External load 7 Bypass valve 8, 8a, 8b, 8c, 8d Inlet temperature sensor 9, 9a, 9b, 9c, 9d Outlet temperature sensor 10, 10a, 10b, 10c, 10d Refrigeration unit control device 20 Control device

Claims (8)

A control device for a heat source system having a plurality of heat source devices,
An inlet temperature sensor for detecting a heat medium inlet temperature, which is the heat medium temperature on the inlet side of the heat source machine, and an outlet temperature sensor for detecting a heat medium outlet temperature, which is the heat medium temperature on the outlet side, are installed for each of the heat source machines,
The control device acquires the heat medium inlet temperature and the heat medium outlet temperature, and sets an initial value to a heat medium outlet temperature setting value, which is a setting value of the heat medium outlet temperature of the heat source device;
When the heat medium inlet temperature falls below a light-load stop temperature, the heat source machine enters a light-load stop state in which the compressor of the heat source machine stops, and when the heat medium inlet temperature during the light-load stop state is greater than the light-load stop temperature and exceeds a light-load return temperature, which is a value obtained by adding a predetermined value to the heat medium outlet temperature setting value , the heat source machine enters a light-load return state in which the compressor of the heat source machine starts,
A control device for a heat source system that performs forced return control to change the heat medium outlet temperature setting value to a lower limit value that is smaller than the initial value when any of the heat source units reaches a light load stop. A control device for a heat source system having a plurality of heat source devices,
An inlet temperature sensor for detecting a heat medium inlet temperature, which is the heat medium temperature on the inlet side of the heat source machine, and an outlet temperature sensor for detecting a heat medium outlet temperature, which is the heat medium temperature on the outlet side, are installed for each of the heat source machines,
The control device acquires the heat medium inlet temperature and the heat medium outlet temperature, and sets an initial value to a heat medium outlet temperature setting value, which is a setting value of the heat medium outlet temperature of the heat source device;
When the heat medium inlet temperature falls below a light-load stop temperature, the heat source machine enters a light-load stop state in which the compressor of the heat source machine stops, and when the heat medium inlet temperature during the light-load stop state is greater than the light-load stop temperature and exceeds a light-load return temperature, which is a value obtained by adding a predetermined value to the heat medium outlet temperature setting value , the heat source machine enters a light-load return state in which the compressor of the heat source machine starts,
A control device for a heat source system that performs forced return control in which, when any of the heat source units reaches a light-load stop, the heat medium outlet temperature set value is changed to a value lowered from the initial value by an amount equal to the difference between the light-load return temperature and the heat medium inlet temperature of the heat source unit plus a first correction value. The control device for a heat source system according to claim 1 or 2, which performs forced return control when forced rotation control is being performed to forcibly rotate the heat source machine, and performs normal control to stop the machine under light load when the forced rotation control is not being performed, and does not perform forced return control. A control device for a heat source system according to any one of claims 1 to 3, which, when a light load is restored by the forced return control, gradually increases the heat medium outlet temperature setting value changed by the forced return control at a predetermined rate until it reaches the initial value. The heat transfer medium outlet temperature setting value is increased to a settable upper limit value of the heat transfer medium outlet temperature setting value,
The control device for a heat source system according to claim 4 , wherein the settable upper limit value is a value obtained by subtracting a second correction value from the sum of the heat medium outlet temperature setting value and the difference between the heat medium inlet temperature and the light load stop temperature. A heat source system comprising a plurality of heat source machines and a control device according to any one of claims 1 to 5. A control method for a heat source system having a plurality of heat source devices,
An inlet temperature sensor for detecting a heat medium inlet temperature, which is the heat medium temperature on the inlet side of the heat source machine, and an outlet temperature sensor for detecting a heat medium outlet temperature, which is the heat medium temperature on the outlet side, are installed for each of the heat source machines,
When the heat medium inlet temperature falls below a light-load stop temperature, the heat source machine enters a light-load stop state in which the compressor of the heat source machine stops, and when the heat medium inlet temperature during the light-load stop state is greater than the light-load stop temperature and exceeds a light-load return temperature, which is a value obtained by adding a predetermined value to the heat medium outlet temperature setting value , the heat source machine enters a light-load return state in which the compressor of the heat source machine starts,
Obtaining the heat transfer medium inlet temperature and the heat transfer medium outlet temperature;
A step of setting an initial value to a heat medium outlet temperature setting value, which is a setting value of the heat medium outlet temperature of the heat source machine;
and when any of the heat source units reaches a light-load stop, performing forced return control to change the heat medium outlet temperature set value to a lower limit value that is smaller than the initial value. A control program for a heat source system having a plurality of heat source devices,
An inlet temperature sensor for detecting a heat medium inlet temperature, which is the heat medium temperature on the inlet side of the heat source machine, and an outlet temperature sensor for detecting a heat medium outlet temperature, which is the heat medium temperature on the outlet side, are installed for each of the heat source machines,
When the heat medium inlet temperature falls below a light-load stop temperature, the heat source machine enters a light-load stop state in which the compressor of the heat source machine stops, and when the heat medium inlet temperature during the light-load stop state is greater than the light-load stop temperature and exceeds a light-load return temperature, which is a value obtained by adding a predetermined value to the heat medium outlet temperature setting value, the heat source machine enters a light-load return state in which the compressor of the heat source machine starts,
Obtaining the heat transfer medium inlet temperature and the heat transfer medium outlet temperature;
A step of setting an initial value to a heat medium outlet temperature setting value, which is a setting value of the heat medium outlet temperature of the heat source machine;
A control program for a heat source system that causes a computer to execute a step of performing forced return control to change the heat medium outlet temperature setting value to a lower limit value that is smaller than the initial value when any of the heat source units reaches a light-load stop.

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