Heat source system, control method therefor, and control program

Abstract

The purpose of the present disclosure is to achieve an improvement in the operational efficiency of a heat source system that pressurizes and conveys fluid supplied to a plurality of heat source machines by means of a plurality of common pumps. This heat source system is provided with: a plurality of heat source machines connected in parallel to an external load; a return header in which fluid from the external load is collected; a supply header in which the fluid is collected, the temperature of fluid being adjusted by the heat source machines; a plurality of pumps that is provided on the upstream side of the fluid flow in the return header and controls the flow rate of the fluid supplied to the return header; and a pump control unit (46) that controls the plurality of pumps. The plurality of pumps includes a variable speed pump, and the pump control unit (46) controls, on the basis of the frequency of the pumps that are in operation, the number of pumps to be operated.

Description

Heat source system, control method and control program

[0001] The present disclosure relates to a heat source system, a control method for the heat source system, and a control program for the heat source system.

[0002] Conventionally, a heat source system in which a plurality of heat source units are connected in parallel is known (see, for example, Patent Document 1). In such a heat source system, a fluid (e.g., water) heated or cooled by use in an external load is sent to each heat source unit via a return header, and the fluid cooled or heated to a predetermined target temperature in the heat source unit is sent to the external load via a supply header.

[0003] Patent No. 5517667

[0004] The heat source system described in Patent Document 1 has one pump for each heat source machine, and controls the fluid flow rate supplied to each heat source machine by the pump corresponding to each heat source machine, and is not configured to pump fluid supplied to multiple heat source machines using multiple common pumps.

[0005] The present disclosure has been made in consideration of the above circumstances, and one of its several objectives is to provide a heat source system, a control method, and a control program therefor, which can improve the operational efficiency of a heat source system in which a plurality of common pumps are used to pump fluid to be supplied to a plurality of heat source machines. Another of its several objectives is to provide a heat source system, a control method, and a control program therefor, which can improve the operational safety of a heat source system in which a plurality of common pumps are used to pump fluid to be supplied to a plurality of heat source machines.

[0006] One aspect of the present disclosure is a heat source system comprising a plurality of heat source units connected in parallel to an external load, a return header that collects fluid from the external load, a supply header that collects fluid that has been temperature-adjusted by the heat source units, a plurality of pumps that are provided upstream of the return header in the fluid flow and control the flow rate of fluid supplied to the return header, and a pump control unit that controls the plurality of pumps, wherein the plurality of pumps include variable speed pumps, and the pump control unit controls the number of pumps in operation based on the frequency of the pumps during operation.

[0007] One aspect of the present disclosure is a heat source system comprising: a plurality of heat source units connected in parallel to an external load; a return header that collects fluid from the external load; a supply header that collects fluid that has been temperature-adjusted by the heat source units; a plurality of pumps that are provided upstream of the return header in the fluid flow and control the flow rate of the fluid supplied to the return header; a target flow rate calculation unit that calculates a load target flow rate value using characteristics of the heat source units; and a pump control unit that controls the plurality of pumps, wherein the plurality of pumps include variable speed pumps; and the pump control unit is equipped with: a calculation unit that calculates a frequency command value for the pumps that reduces the deviation between the load target flow rate value and the total fluid flow rate value of the heat source units; and a correction unit that corrects the frequency command value when the number of operating heat source units is changed or when the number of operating pumps is changed.

[0008] One aspect of the present disclosure is a heat source system comprising: a plurality of heat source machines connected in parallel to an external load; a primary return header that collects fluid from the external load; a plurality of pumps that are provided upstream of the fluid flow of the primary return header and control the flow rate of fluid supplied to the primary return header; a secondary return header that is provided upstream of the fluid flow of the plurality of pumps; a bypass pipe that connects the primary return header and the secondary return header; a return bypass valve that is provided in the bypass pipe; a supply header that collects fluid that has been temperature-adjusted by the heat source machines; and a pump control unit that controls the plurality of pumps, wherein the plurality of pumps include variable speed pumps, and the pump control unit controls the plurality of pumps so as to reduce the deviation between the pressure measurement value of the primary return header and a preset pressure set value.

[0009] One aspect of the present disclosure is a heat source system comprising: a plurality of heat source machines connected in parallel to an external load; a primary return header that collects fluid from the external load; a plurality of pumps that are provided upstream of the fluid flow of the primary return header and control the flow rate of fluid supplied to the primary return header; a secondary return header that is provided upstream of the fluid flow of the plurality of pumps; a bypass pipe that connects the primary return header and the secondary return header; a return bypass valve that is provided in the bypass pipe; a supply header that collects fluid that has been temperature-adjusted by the heat source machines; and a return bypass valve control unit that controls the return bypass valve.

[0010] One aspect of the present disclosure is a control method for a heat source system including a plurality of heat source units connected in parallel to an external load, a return header that collects fluid from the external load, a supply header that collects fluid that has been temperature-adjusted by the heat source units, and a plurality of pumps that are provided upstream of the return header in the fluid flow and control the flow rate of fluid supplied to the return header, wherein the plurality of pumps include variable speed pumps, and a computer controls the number of pumps in operation based on the frequency of the pumps during operation.

[0011] One aspect of the present disclosure is a control program for causing a computer to execute the above control method.

[0012] According to the present disclosure, it is possible to achieve energy savings in a heat source system in which a fluid to be supplied to a plurality of heat source units is pumped by a plurality of common pumps. According to the present disclosure, it is possible to improve the safety of the operation of a heat source system in which a fluid to be supplied to a plurality of heat source units is pumped by a plurality of common pumps.

[0013] FIG. 1 is a diagram showing a schematic configuration of a heat source system according to a first embodiment of the present disclosure. FIG. 2 is a diagram showing a schematic configuration of a control system of the heat source system according to the first embodiment of the present disclosure. FIG. 3 is a schematic configuration diagram showing an example of a hardware configuration of a system control device according to the first embodiment of the present disclosure. FIG. 4 is a functional configuration diagram showing an example of a function provided in the system control device according to the first embodiment of the present disclosure. FIG. 5 is a diagram showing an example of a configuration of a target flow rate calculation unit according to the first embodiment of the present disclosure. FIG. 6 is a diagram showing an example of a configuration of a heat source machine flow rate setting unit according to the first embodiment of the present disclosure. FIG. 7 is a diagram for explaining a method for setting a target flow rate value for a heat source machine by the heat source machine flow rate setting unit according to the first embodiment of the present disclosure. FIG. 8 is a flowchart showing an example of a procedure of a valve control method according to the first embodiment of the present disclosure. FIG. 9 is a flowchart showing an example of a procedure of a method for controlling the number of pumps according to the first embodiment of the present disclosure. FIG. 10 is a functional configuration diagram showing an example of a frequency control unit provided in the pump control unit according to the first embodiment of the present disclosure. FIG. 11 is a flowchart showing an example of a procedure of a method for controlling the frequency of a pump according to the first embodiment of the present disclosure. FIG. 12 is a diagram showing a schematic configuration of a heat source system according to a second embodiment of the present disclosure. FIG. 13 is a functional configuration diagram showing an example of a function provided in the system control device according to the second embodiment of the present disclosure. FIG. 10 is a diagram for explaining a control method of a return bypass valve according to a second embodiment of the present disclosure.

[0014] First Embodiment A heat source system, a control method thereof, and a control program thereof according to a first embodiment of the present disclosure will be described below with reference to the drawings. FIG. 1 is a diagram schematically illustrating the configuration of a heat source system 1 according to a first embodiment of the present disclosure. The heat source system 1 cools or heats a fluid (e.g., water) that has been used in an external load, such as an air conditioner, a water heater, or factory equipment, and whose temperature has been increased or decreased, and then supplies the fluid to the external load again. The heat source system 1 includes multiple heat source units 10 (10a, 10b, 10c) connected in parallel to the external loads. The heat source units 10 may be of the same model and capacity, or may be a mixture of different models and capacities. Examples of heat source units include a chiller, a turbo chiller, and an absorption chiller.

[0015] FIG. 1 illustrates an example in which three heat source units 10 (10a, 10b, 10c) are installed, but the number of installed heat source units can be determined arbitrarily. Hereinafter, for convenience of explanation, a case in which the heat source system 1 cools a fluid and supplies it to an external load will be described, but the present disclosure also applies to a case in which the fluid is heated and supplied to an external load. In the following explanation, when it is necessary to distinguish between the heat source units 10a, 10b, and 10c, they will be referred to as the heat source units 10a, 10b, etc., and when there is no need to distinguish between them, they will be simply referred to as the heat source unit 10. The same applies to other configurations.

[0016] The heat source system 1 includes a return header 11 that collects fluid from an external load. The return header 11 includes, for example, a primary return header 11a and a secondary return header 11b that is provided upstream of the primary return header 11a in the fluid flow direction. A plurality of pumps 12 (12a, 12b, 12c) for controlling the flow rate of the fluid are provided between the primary return header 11a and the secondary return header 11b, in other words, upstream of the primary return header 11a in the fluid flow direction. For example, the primary return header 11a and the secondary return header 11b are connected by three pipes, and each pipe is provided with a pump 12. The pumps 12 may be of the same model and capacity, or may be of different models and capacities. The pumps 12 may be fixed-speed pumps, variable-speed pumps, or a combination of these. For convenience of explanation, this embodiment will be described assuming that each pump 12 is a variable-speed pump. Each pump 12 is driven by, for example, an inverter motor (not shown), which allows the rotation speed to be varied to thereby perform variable flow rate control.

[0017] Flow control valves 14 (14a, 14b, 14c) are provided between the primary return header 11a and each of the heat source units 10a, 10b, 10c. The flow control valves 14a, 14b, 14c are provided corresponding to each of the heat source units 10a, 10b, 10c, respectively, and adjust the flow rate of the fluid supplied to the corresponding heat source unit 10a, 10b, 10c. The fluid whose temperature has been adjusted by each of the heat source units 10 is collected in a supply header 16 and supplied to an external load. A bypass pipe is provided between the secondary return header 11b and the supply header 16, and a main pipe bypass valve 17 is provided in the bypass pipe.

[0018] The heat source system 1 is provided with a pressure sensor 21 that measures the pressure of the primary return header 11a, a differential pressure sensor 22 that measures the differential pressure between the secondary return header 11b and the supply header 16, and flow rate sensors 23a, 23b, and 23c that measure the flow rates of fluids sent from the heat source units 10a, 10b, and 10c to the supply header 16. Measurement values ​​measured by these various sensors are sent to a system control device 30. The system control device 30 controls the pump 12, flow rate adjustment valve 14, main pipe bypass valve 17, and the like using the measurements from the various sensors.

[0019] As described above, the heat source system 1 according to this embodiment is a single-pump system (primary pump system) in which a plurality of common pumps are used to pump fluid to be supplied to a plurality of heat source units 10, and the flow rate of the fluid supplied to the external load is adjusted by controlling the pump 12. According to this heat source system 1, the fluid heated by use in the external load is sent to the secondary return header 11b. The flow rate of the fluid output from the secondary return header 11b is adjusted by the pump 12 and sent to the primary return header 11a. The flow rate of the fluid output from the primary return header 11a is adjusted by flow control valves 14a, 14b, and 14c provided corresponding to each of the heat source units 10a, 10b, and 10c, respectively, and sent to each of the heat source units 10a, 10b, and 10c. The fluid whose temperature has been adjusted in each of the heat source units 10a, 10b, and 10c is sent to the supply header 16, and then sent from the supply header 16 to the external load.

[0020] 2 is a diagram showing a schematic configuration of a control system of the heat source system 1 according to this embodiment. As shown in FIG. 2, the system control device 30 is connected to heat source machine control devices 50 (50a, 50b, 50c) that control the heat source machines 10a, 10b, 10c via a communication network 25, and is configured to enable two-way communication. The system control device 30 is a control device that controls the entire heat source system 1, and functions as a higher-level device for the heat source machine control devices 50a, 50b, 50c.

[0021] 3 is a schematic diagram showing an example of the hardware configuration of the system control device 30. The system control device 30 is a computer and includes, for example, a CPU (Central Processing Unit: processor) 31, a main memory 32, a secondary storage 33, and a communication interface 34. These components are interconnected directly or indirectly via a bus and work together to execute various processes.

[0022] The system control device 30 may include an input device 35 and an output device 36. The input device 35 and the output device 36 may be connected as external devices via, for example, a communication interface, an external interface, etc. Examples of input devices include a keyboard, a touchpad, and a pointing device. Examples of pointing devices include a mouse, a touch panel, a pen tablet, a trackpad, and a trackball. Examples of output devices include a display, a projector, and a printer.

[0023] The CPU 31 controls the entire heat source system 1 using, for example, an operating system (OS) stored in a secondary storage device 33 connected via a bus, and executes various processes by executing various programs stored in the secondary storage device 33. One or more CPUs 31 may be provided, and the CPUs 31 may cooperate with each other to realize processes.

[0024] The main storage device 32 is composed of writable memory such as cache memory, RAM (Random Access Memory), etc., and is used as a work area for reading execution programs of the CPU 31 and writing processing data by the execution programs. The secondary storage device 33 is a non-transitory computer-readable storage medium. The secondary storage device 33 is, for example, a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, etc. Examples of the secondary storage device 33 include a ROM (Read Only Memory), an HDD (Hard Disk Drive), an SSD (Solid State Drive), and a flash memory. The secondary storage device 33 stores, for example, an operating system such as Windows (registered trademark), iOS (registered trademark), or Android (registered trademark), a BIOS (Basic Input / Output System), various device drivers for operating peripheral devices, various application software, and various data and files. The secondary storage device 33 stores programs for implementing various processes and various data required for implementing the various processes. A plurality of secondary storage devices 33 may be provided, and the above-mentioned programs and data may be stored separately in each secondary storage device 33.

[0025] Each heat source machine control device 50 is also a computer, and like the above-described system control device 30, is equipped with a CPU, a main memory device, a secondary memory device, etc. Many known technologies have been proposed for the heat source machine control device 50, so it is sufficient to adopt these known technologies as appropriate.

[0026] [System Control Device] Figure 4 is a functional configuration diagram showing an example of the functions of the system control device 30. A series of processes for realizing the various functions described below are stored in the form of a program in the secondary storage device 33, for example, and are realized by the CPU (processor) 31 reading this program into the main storage device 32 and executing information processing and arithmetic operations. The program may be pre-installed in the secondary storage device 33, provided in a state stored in another non-transitory computer-readable storage medium, or distributed via wired or wireless communication means. Examples of non-transitory computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

[0027] 4, the system control device 30 includes, for example, a target flow rate calculation unit 43, a heat source unit flow rate setting unit 44, a valve control unit 45, and a pump control unit 46. The system control device 30 may also include an information acquisition unit 41, a storage unit 42, and the like.

[0028] [Information Acquisition Unit] The information acquisition unit 41 acquires, for example, via a communication line, information required for the system control device 30 to control the heat source system 1. For example, the information acquisition unit 41 acquires measurement values ​​from various sensors provided in the heat source system 1. For example, the information acquisition unit 41 acquires a pressure measurement value measured by the pressure sensor 21, a main pipe differential pressure measurement value measured by the differential pressure sensor 22, and flow rate measurement values ​​measured by the flow rate sensors 23a, 23b, and 23c. The information acquisition unit 41 may also acquire a required flow rate of an external load from an external load control device (not shown) that controls the external load.

[0029] [Storage Unit] The storage unit 42 stores various data and algorithms (including arithmetic expressions) required for the system control device 30 to control the heat source system 1. For example, the storage unit 42 stores the characteristics of each heat source unit 10 (e.g., lower flow rate limit, upper flow rate limit, etc.), the characteristics of each pump 12 (e.g., lower flow rate limit, upper flow rate limit, etc.), the arithmetic expressions, coefficients used in the various arithmetic expressions, etc.

[0030] [Target Flow Rate Calculation Unit] The target flow rate calculation unit 43 calculates a load target flow rate value using the characteristics of the heat source unit 10 during operation. As shown in FIG. 5 , the target flow rate calculation unit 43 includes a calculation unit 431 and a limiter unit 432. For example, the calculation unit 431 calculates a load target flow rate value that reduces the deviation between the main pipe differential pressure measurement value measured by the differential pressure sensor 22 and a preset main pipe differential pressure set value. For example, the calculation unit 431 performs PI control on the deviation between the main pipe differential pressure measurement value and the main pipe differential pressure set value to calculate the load target flow rate value. By calculating such a load target flow rate value, it becomes possible to maintain the valve opening of the main pipe bypass valve 17 in a fully closed state or a state close to being fully closed.

[0031] The limiter unit 432 corrects the load target flow rate value as necessary so that the load target flow rate value set by the calculation unit 431 falls within the upper and lower limit range. The upper and lower limit values ​​may be fixed values ​​set in advance, or may be values ​​dynamically derived from the characteristics of the pump 12 and the heat source unit 10. Information such as the upper and lower limit values ​​or calculation formulas for calculating the upper and lower limit values ​​may be information stored in the storage unit 42 described above, for example.

[0032] The upper limit value is set, for example, to a value equal to or less than the sum of the upper limit flow rates of the pumps 12. For example, the upper limit value is set to the sum of the upper limit flow rates of the pumps 12a to 12c.

[0033] The lower limit value is set to, for example, a value obtained by multiplying the total value of the flow rate lower limit values ​​of the heat source units 10 in operation by a correction value C1 (C1≧1.0). For example, the lower limit value is calculated using the following arithmetic formula (1).

[0034] Lower limit value = total value of lower limit flow rate of heat source units in operation × C1 (1)

[0035] In this way, by multiplying the lower limit value by the correction value C1 to provide a margin of error, it is possible to prevent the fluid flow rate from falling below the lower limit flow rate of the heat source unit 10 and causing the heat source unit 10 to stop due to a sudden pressure fluctuation or failure of the pump 12.

[0036] The lower limit value may be set to, for example, a value equal to or greater than the value obtained by multiplying the maximum value of the flow rate lower limit value of the heat source units 10 in operation by the number of operating heat source units 10. For example, the lower limit value is calculated using the following arithmetic formula (2).

[0037] Lower limit value = Maximum flow rate lower limit value of heat source units in operation × Number of operating units × C2 (2)

[0038] Here, C2 is a correction value and is set to a value equal to or greater than 1.0. For example, when the heat source units 10a to 10c are in operation, the flow rate lower limit values ​​of the heat source units 10a and 10b are 500 [m ３ / h], and the lower limit of the flow rate of the heat source unit 10c is 1000 [m ３ / h], and when the correction value C2 is 1.0, the lower limit of the load target flow rate value is 3000 [m ３ / h].

[0039] For example, if heat source units 10 with different capacities are mixed and the lower limit flow rates of the heat source units 10 are different, more fluid tends to flow to the heat source units 10 with larger capacities, and less fluid tends to flow to the heat source units with smaller capacities. In this case, the fluid flow rate supplied to the heat source unit 10 with smaller capacity may fall below the lower limit flow rate of the heat source unit 10, which may cause an emergency shutdown. Therefore, as described above, by setting the lower limit of the load target flow rate value using the maximum value of the lower limit flow rate of the heat source units 10 currently in operation, it is possible to avoid a shutdown of the heat source unit 10 due to insufficient flow rate, even if the lower limit flow rates of multiple heat source units differ. This makes it possible to improve the safety of the operation of the heat source units 10.

[0040] As described below, when the number of operating heat source units 10 is reduced by stopping the operating heat source units 10, the target flow rate calculation unit 43 retains the load target flow rate value of the heat source units 10 before the heat source units 10 were stopped for a predetermined period of time. Here, the load target flow rate value before the heat source units 10 were stopped may be, for example, the load target flow rate value that was set when the operation stop signal was transmitted. It takes a certain amount of time from when the operation stop signal is transmitted to the heat source units 10 until the heat source units 10 (specifically, the compressors) stop operating based on this command. As described below, the flow control valves 14 are controlled to a fully closed state after the compressors of the heat source units 10 are stopped. Therefore, the target flow rate calculation unit 43 retains, for example, the load target flow rate value that was set when the operation stop signal was transmitted from when the operation stop signal was transmitted to the heat source units 10 until the flow control valves 14 corresponding to the heat source units 10 are fully closed. This allows a necessary and sufficient flow rate of fluid to be supplied until the compressors of the heat source units 10 are stopped, enabling the heat source units 10 to be safely shut down.

[0041] [Heat source machine flow rate setting unit] The heat source machine flow rate setting unit 44 sets a target flow rate value for each heat source machine according to the load target flow rate value calculated by the target flow rate calculation unit 43. For example, as shown in Fig. 6, the heat source machine flow rate setting unit 44 includes a setting unit (calculation unit) 441 and a limiter unit 442. The setting unit 441 sets the target flow rate value for each heat source machine 10, for example, by dividing the load target flow rate value by the number of heat source machines 10 in operation.

[0042] Here, when the multiple operating heat source machines 10 include a mixture of heat source machines 10 with different capacities, if the target flow rate value of each heat source machine 10 is set by simply dividing the load target flow rate value by the number of operating machines, there is a possibility that some heat source machines 10 will have a target flow rate value set that exceeds the upper flow rate limit of the heat source machine 10. In this case, the heat source machine flow rate setting unit 44 identifies a target heat source machine 10 whose target flow rate value is greater than the upper flow rate limit of the heat source machine 10, and distributes the excess target flow rate value to the other operating heat source machines 10 so that the target flow rate value of the target heat source machine is equal to or less than the upper flow rate limit.

[0043] For example, as shown in FIG. 7, the upper flow rate limit values ​​of the heat source units 10a, 10b, and 10c are set to 500 m３ / h], 600 [m ３ / h], 300 [m ３ / h], and the load target flow rate value is 1200 [m ３ / h], if this is evenly allocated to each of the heat source units 10a to 10c, the target flow rate value will be 400 [m ３ In this case, since this target flow rate value exceeds the upper flow rate limit of the heat source unit 10c, this excess amount 100 is distributed equally to each of the heat source units 10a and 10b. As a result, the target flow rate values ​​of each of the heat source units 10a, 10b, and 10c are each 450 [m ３ / h], 450 [m ３ / h], 300 [m ３ / h]. Here, the excess is distributed evenly, but it may be distributed according to the capacity of the heat source unit 10.

[0044] The limiter unit 442 corrects the target flow rate value of each heat source unit 10 set by the setting unit 441 to fall within an upper and lower limit range. Specifically, the limiter unit 442 corrects the heat source unit target flow rate value as needed so that the target flow rate value of each heat source unit falls within the upper and lower limit ranges shown below. The upper limit value is set to, for example, the upper flow rate upper limit value of each heat source unit 10. The lower limit value is set to, for example, the highest flow rate lower limit value among the heat source units 10 that are in operation.

[0045] In this way, by setting the lower limit value to the highest flow rate lower limit value among the heat source units 10 that are in operation, it is possible to avoid emergency shutdowns or abnormal shutdowns of the heat source units 10 due to insufficient fluid flow rates, even if the lower limit flow rates differ between the heat source units 10. Although explanations of control over the number of heat source units have been omitted, this may be performed by appropriately using known technology.

[0046] [Valve control unit] The valve control unit 45 calculates the valve opening degree of each flow rate adjustment valve 14 so as to reduce the deviation between the target flow rate value of each heat source unit 10 set by the heat source unit flow rate setting unit 44 and the flow rate measurement value of each heat source unit 10. For example, the valve control unit 45 performs PI control on the deviation between the flow rate measurement value measured by the flow rate sensor 23a and the target flow rate value of the heat source unit 10a, and calculates the valve opening degree of the flow rate adjustment valve 14a corresponding to the heat source unit 10a. Similarly, the valve control unit 45 calculates the valve opening degrees of the flow rate adjustment valves 14b and 14c.

[0047] After the heat source machine 10 starts operating, the valve control unit 45 starts valve control (valve opening control) of the flow rate adjustment valve 14 corresponding to that heat source machine 10. Here, the start of operation of the heat source machine 10 refers to, for example, when the compressor of the heat source machine 10 starts operating, when an operation start signal is sent to the heat source machine 10, or a predetermined timing from when the operation start signal is sent to the heat source machine 10 to when the compressor of the heat source machine 10 starts operating. Furthermore, the valve control unit 45 ends valve control of the flow rate adjustment valve 14 corresponding to that heat source machine 10 after the compressor of the heat source machine 10 stops. Furthermore, the valve control unit 45 maintains the valve opening at the time of sending the operation stop signal during the period from when the operation stop signal is sent to the heat source machine 10 to when the compressor of the heat source machine 10 stops. This makes it possible to safely stop the heat source machine 10 without causing a flow rate shortage.

[0048] When the following opening degree increase condition is met for a certain period of time during operation of the heat source unit 10, the valve control unit 45 may prioritize the above-mentioned PI control and perform control to increase the valve opening degree of all flow control valves 14 corresponding to the operating heat source unit 10 by a predetermined opening degree.

[0049] (Condition 1) When the maximum valve opening degree among the valve opening degrees of the flow rate adjustment valves 14 corresponding to the heat source units 10 in operation is smaller than a predetermined opening degree threshold, and (Condition 2) When the frequency command value of the pump 12 is larger than a predetermined frequency threshold.

[0050] Here, the opening degree threshold is a value that is set based on, for example, the upper limit of the opening degree of the flow rate adjustment valve 14. For example, the opening degree threshold is set to a value obtained by subtracting a predetermined correction value from the upper limit of the opening degree of the flow rate adjustment valve 14. The frequency threshold is a value that is set based on, for example, the lower limit of the frequency of the pump 12. For example, the frequency threshold is set to a value obtained by adding a predetermined correction value to the lower limit of the frequency of the pump.

[0051] For example, when the above-described condition for increasing the opening is satisfied, the fluid being pumped by the pump 12 is throttled by the flow control valve 14, and the power of the pump 12 is being wasted. Therefore, in this state, the opening command value is controlled to increase by a predetermined opening, so that the fluid sent from the pump 12 is circulated as efficiently as possible. This makes it possible to reduce unnecessary energy consumption in the pump 12.

[0052] Next, a valve control method executed by the above-mentioned valve control unit 45 will be described with reference to Fig. 8. Fig. 8 is a flowchart showing an example of the procedure of the valve control method according to this embodiment. The following series of processing procedures is started when any one of the heat source units 10 starts operation and is ended when the compressors of all the heat source units 10 stop operating. Furthermore, the following series of processing is repeatedly executed at predetermined time intervals or at predetermined timing.

[0053] First, the valve position command value for the flow control valve 14 corresponding to each operating heat source unit 10 is calculated using the target flow rate value set for the operating heat source unit 10 and the flow rate measurement value measured by the flow sensor 23 corresponding to that heat source unit 10 (SA1). Next, it is determined whether the amount-increase condition is met (SA2). As a result, if the amount-increase condition is not met (SA2: NO), each flow control valve 14 is controlled based on the calculated valve position command value (SA3). On the other hand, if the amount-increase condition is met (SA2: YES), the calculated valve position command value is corrected by adding a predetermined value to the calculated valve position command value (SA4), and each flow control valve 14 is controlled based on the corrected valve position command value (SA3).

[0054] [Pump Control Unit] The pump control unit 46 controls the number of operating pumps 12 and the frequency of the pumps 12 based on the load target flow rate value set by the target flow rate calculation unit 43 and the frequency of the pumps 12. The pump control unit 46 starts controlling the pumps 12 after the first heat source unit 10 starts operation, and ends controlling the pumps 12 after the compressors of all the heat source units 10 have stopped. Here, the time when the heat source unit 10 starts operation refers to, for example, when the compressor of the heat source unit 10 starts operation, when an operation start signal is sent to the heat source unit 10, or a predetermined timing from when an operation start signal is sent to the heat source unit 10 to when the compressor of the heat source unit 10 starts operation. Below, the control of the number of operating pumps 12 and the frequency control performed by the pump control unit 46 will be described.

[0055] [Control of the number of operating pumps] When starting pump control, the pump control unit 46 sets the number of operating pumps 12, for example, by dividing the load target flow rate value by the lower limit flow rate value of the pump 12. After starting pump control, the pump control unit 46 controls the number of operating pumps 12 based on the frequency of the operating pumps 12, for example; in other words, it increases or decreases the number of operating pumps. In explaining the transition, increasing the number of operating pumps is also referred to as "increasing the number," and decreasing the number of operating pumps is also referred to as "decreasing the number."

[0056] For example, the pump control unit 46 increases the number of operating pumps when the frequencies of all of the operating pumps 12 are equal to or greater than a predetermined step-up threshold set to be equal to or less than the upper frequency limit of the pumps 12. That is, the step-up condition (hereinafter referred to as "step-up condition 1") is expressed by the following equation (3). In this case, the pump control unit 46 may output an operation start command to the stopped pumps 12 when the following step-up condition 1 is continuously satisfied for a certain period of time.

[0057] Increase condition: Pfc≧Pfmax−C3 (3)

[0058] In the above formula (3), Pfc is the frequency value of the pump 12, Pfmax is the upper frequency limit value of each pump 12, and C3 is a predetermined correction value.

[0059] The pump control unit 46 may increase the number of operating pumps when the following increase-stage condition 2 is satisfied. More specifically, the pump control unit 46 may output an operation start command to a stopped pump when the following increase-stage condition 2 is satisfied continuously for a certain period of time.

[0060] Fg≧ΣPrate×C4 (4)

[0061] In the above formula (4), Fg is the load target flow rate value, Prate is the total value of the rated flow rates of the operating pumps 12, and C4 is a predetermined correction value that is set to a value equal to or less than 1.0. That is, the pump control unit 46 increases the number of operating pumps 12 when the load target flow rate value remains greater than the total value of the rated flow rates of the operating pumps 12 multiplied by the predetermined correction value for a certain period of time.

[0062] The pump control unit 46 may increase the number of operating pumps 12 when at least one of the above-described step-up condition 1 and step-up condition 2 is satisfied (OR condition).

[0063] The pump control unit 46 reduces the number of operating pumps 12, for example, when the frequencies of all of the operating pumps 12 are equal to or lower than a predetermined step-down threshold set to be equal to or higher than the lower limit frequency value of the pumps. That is, the step-down condition (hereinafter referred to as "step-down condition 1") is expressed by the following equation (5). In this case, the pump control unit 46 may output an operation stop command to the operating pumps 12 when the following step-down condition 1 is continuously satisfied for a certain period of time.

[0064] Stage reduction condition: Pfc≦Pfmin+C5 (5)

[0065] In the above formula (5), Pfc is the frequency value of the pump 12, Pfmin is the lower limit frequency value of each pump 12, and C5 is a constant.

[0066] The pump control unit 46 may reduce the number of operating pumps when the following reduction condition 2 is satisfied. More specifically, the pump control unit 46 may output an operation stop command to the operating pumps when the following reduction condition 2 is satisfied continuously for a certain period of time.

[0067] Stage reduction condition: Fg≦ΣPe_rate×C6 (6)

[0068] In the above formula (6), Fg is the load target flow rate value, Pe_rate is the total value of the rated flow rates of the operating pumps 12 excluding pumps scheduled to be shut down, and C6 is a predetermined correction value that is set to a value equal to or less than 1.0. In other words, the pump control unit 46 reduces the number of operating pumps 12 when the load target flow rate value is equal to or less than the value obtained by multiplying the total value of the rated flow rates of the operating pumps 12 excluding pumps 12 scheduled to be shut down by the predetermined correction value.

[0069] The pump control unit 46 may reduce the number of operating pumps 12 when at least one of the above-described step-down condition 1 and step-down condition 2 is satisfied (OR condition).

[0070] When the number of operating pumps is increased or decreased, the pump control unit 46 may prohibit the increase or decrease of the number of operating pumps for a certain period of time, thereby stabilizing the load and the pressure in the system.

[0071] Next, a method for controlling the number of pumps 12 executed by the above-described pump control unit 46 will be described with reference to Fig. 9. Fig. 9 is a flowchart showing an example of the procedure for the method for controlling the number of pumps 12 according to this embodiment. The series of processes shown below is started when at least one heat source unit 10 starts operating, and is ended when the compressors of all heat source units 10 stop operating.

[0072] First, the number of pumps to be operated is set by dividing the load target flow rate value by the lower limit flow rate value of the pump 12, and the set number of pumps to be operated are started (SB1). Next, the pump to be started next is determined (SB2). For example, the operation order of the pumps 12 is set in advance, and the pump 12 to be started next is determined based on that operation order. The operation order may be dynamically set based on, for example, the cumulative operation time of the pumps 12, or may be a predetermined fixed order. If all pumps 12 are in operation, this process is omitted. Next, the pump to be stopped is determined (SB3). This process is also performed in the same way as when determining the pump to be started.

[0073] Next, it is determined whether Increase Condition 1 or Increase Condition 2 is satisfied (SB4). If Increase Condition 1 or Increase Condition 2 is satisfied (SB4: YES), it is determined whether a predetermined period of time has elapsed since the previous change in the number of operating pumps (SB5). In other words, immediately after the number of operating pumps 12 is changed, the fluid flow rate is not stable, and an unexpected abnormality may occur. For this reason, if the number of operating pumps 12 is changed, in other words, if a new start pump is started or a stopped pump is stopped, the operation of the pumps 12 is not started or stopped for a predetermined period of time.

[0074] In step SB5, if a predetermined period has not elapsed since the previous change in the number of operating pumps (SB5: NO), the process waits until the predetermined period has elapsed, and after the predetermined period has elapsed (SB5: YES), the process starts operation of the start pump (SB6).Then, the process determines the next start pump to be started (SB7), and returns to step SB4.If all pumps 12 are in operation, the process of step SB7 is omitted.

[0075] If the determination in step SB4 is negative (SB4: NO), the system determines whether step-down condition 1 or step-down condition 2 is satisfied (SB8). If step-down condition 1 or step-down condition 2 is not satisfied (SB8: NO), the system returns to step SB4 and performs subsequent processing. On the other hand, if step-down condition 1 or step-down condition 2 is satisfied (SB8: YES), the system determines whether a predetermined period has elapsed since the previous change in the number of operating units (SB9). If the predetermined period has not elapsed since the previous change in the number of operating units (SB9: NO), the system waits until the predetermined period has elapsed, and after the predetermined period has elapsed (SB9: YES), the system stops operation of the stopped pump (SB10). The system then determines the next stopped pump to be started (SB11), and returns to step SB4.

[0076] 9, the number of operating units is increased when step-up condition 1 or step-up condition 2 is satisfied, and decreased when step-down condition 1 or step-down condition 2 is satisfied, but this example is not limiting. For example, the number of operating units may be controlled using only step-up condition 1 and step-down condition 1, or the number of operating units may be controlled using only step-up condition 2 and step-down condition 2. Furthermore, when step-up condition 1 or the like is maintained for a predetermined period of time, it may be determined that the condition is met.

[0077] [Pump Frequency Control] Next, a description will be given of frequency control of the pump 12. Fig. 10 is a functional configuration diagram showing an example of a frequency control unit 460 included in the pump control unit 46 according to this embodiment. The frequency control unit 460 includes, for example, a calculation unit 461 and a correction unit 462.

[0078] The calculation unit 461 calculates a frequency command value for the pump that reduces the deviation between the load target flow rate value and the total fluid flow rate value of the operating heat source units 10. Here, the total fluid flow rate value of the operating heat source units 10 is a value obtained by adding up the measurement values ​​of the flow rate sensors 23 corresponding to the operating heat source units 10. More specifically, the calculation unit 461 performs PI control on the deviation between the load target flow rate value and the total fluid flow rate value of the operating heat source units 10, and calculates the frequency command value for the pump 12.

[0079] The correction unit 462 corrects the frequency command value when increasing or decreasing the number of operating heat source units 10 or when increasing or decreasing the number of operating pumps 12. For example, the correction unit 462 corrects the frequency command value to increase when increasing the number of operating heat source units 10 or decreasing the number of operating pumps 12. Specifically, the correction unit 462 corrects the frequency command value using the following equation (7).

[0080] Pfm=Pfc+Pfc×[(M+1 / M)-1]×C7 (7)

[0081] Here, Pfm is the corrected pump frequency command value, Pfc is the frequency command value calculated by the calculation unit 461, M is the number of operating heat source machines, and C8 is a correction coefficient, which is a fixed value set, for example, based on design specifications. The reason why the coefficient [(M+1 / M)-1] is included in the above calculation formula is to ensure that the coefficient is always the same regardless of the number of operating pumps, as shown in Table 1 below. By using this coefficient, when a corrected frequency command value is given to each of the operating pumps 12, it is possible to increase the total value of the flow rate delivered from the operating pumps 12 by a predetermined amount, regardless of the number of operating pumps.

[0082]

[0083] When the number of operating heat source machines is increased, the pressure of the target heat source system increases rapidly, causing a sudden decrease in the flow rate of the other operating heat source systems, and the fluid flow rate of the other operating heat source machines 10 may fall below the lower limit of the heat source machine 10. Furthermore, when the number of operating pumps 12 is reduced, the water flow rate to the heat source machine 10 may temporarily decrease, causing the fluid flow rate of the heat source machine 10 to fall below the lower limit. Therefore, when the number of operating heat source machines 10 is increased or the number of operating pumps 12 is reduced, it is possible to prevent breakdowns or abnormal shutdowns of the heat source machines by increasing the frequency command value of the pumps 12.

[0084] For example, the correction unit 462 corrects the frequency command value to decrease when the number of operating heat source units 10 is reduced or when the number of operating pumps 12 is increased. Specifically, the correction unit 462 corrects the frequency command value using the following equation (8).

[0085] Pfm=Pfc+Pfc×[(M-1 / M)-1]×C8 (8)

[0086] Here, Pfm is the corrected pump frequency command value, Pfc is the frequency command value calculated by the calculation unit 461, M is the number of operating heat source machines, and C8 is a correction coefficient, which is a fixed value set, for example, based on design specifications. The reason why the coefficient [(M-1 / M)-1] is included in the above calculation formula is to ensure that the coefficient is always the same regardless of the number of operating pumps, as shown in Table 2 below. By using this coefficient, when a corrected frequency command value is given to each of the operating pumps 12, it is possible to reduce the total value of the flow rate delivered from the operating pumps 12 by a predetermined amount, regardless of the number of operating pumps.

[0087]

[0088] When the number of operating heat source machines is reduced, the pressure of the corresponding heat source system suddenly decreases, which may result in a sudden increase in the flow rate of other operating heat source systems. Also, when the number of operating pumps 12 is increased, the water flow rate to the heat source machines 10 temporarily increases, causing fluctuations in the fluid flow rate of the heat source machines 10. Therefore, when the number of operating heat source machines 10 is increased or the number of operating pumps 12 is reduced, it is possible to suppress fluctuations in the fluid flow rate by reducing the frequency command value of the pumps 12.

[0089] Next, a method for controlling the frequency of the pump 12 executed by the above-described pump control unit 46 will be described with reference to Fig. 11. Fig. 11 is a flowchart showing an example of the procedure for the method for controlling the frequency of the pump 12 according to this embodiment. The series of processes shown below is started when at least one heat source unit 10 starts operating, and is ended when the compressors of all the heat source units 10 stop operating. The series of processes below is repeatedly executed at predetermined time intervals or at predetermined timing.

[0090] First, a frequency command value is calculated using the load target flow rate value and the total flow rate value of the operating heat source units (SC1). Next, it is determined whether the number of operating heat source units has increased or the number of operating pumps has decreased (SC2). If the result is negative (SC2: NO), it is determined whether the number of operating heat source units has decreased or the number of operating pumps has increased (SC3). If the result is negative (SC3: NO), the pump is controlled based on the frequency command value calculated in step SC1 (SC4). On the other hand, if the result is positive (SA2: YES) in step SC2, the frequency command value is corrected to increase (SC5), and the process proceeds to step SC7. If the result is positive (SC3: YES) in step SC3, the frequency command value is corrected to decrease (SC6), and the process proceeds to step SC7. In step SC7, the pump is controlled based on the corrected frequency command value (SC7).

[0091] As described above, according to the heat source system 1 and its control method and control program of this embodiment, the flow rate of fluid from an external load is adjusted by the multiple pumps 12 and sent to the primary return header 11a. The flow rate of the fluid output from the primary return header 11a is adjusted by the flow control valves 14 provided corresponding to each heat source unit 10 and sent to each heat source unit 10. The temperature-adjusted fluid in each heat source unit 10 is sent to the supply header 16 and then sent from the supply header 16 to the external load. In this heat source system 1, the multiple pumps are variable-speed pumps, so flow rate adjustment is possible by controlling the pump frequency. Furthermore, by controlling the number of operating pumps based on the pump frequency, pump operation start and stop can be performed at appropriate times. This is expected to reduce the overall pump transport power, enabling energy savings across the entire heat source system.

[0092] Second Embodiment Next, a heat source system, a control method thereof, and a control program thereof according to a second embodiment of the present disclosure will be described with reference to the drawings. Hereinafter, components common to the first embodiment described above will be assigned the same reference numerals and description thereof will be omitted, and different components will be mainly described.

[0093] 12 is a diagram schematically illustrating the configuration of a heat source system 1a according to a second embodiment of the present disclosure. The heat source system 1a according to this embodiment differs in that a return bypass pipe 18 is provided between the primary return header 11a and the secondary return header 11b, and a return bypass valve 20 is provided in the return bypass pipe 18. In addition, a pressure sensor 21 is provided to measure the pressure of the primary return header 11a, and the pressure measurement value measured by the pressure sensor 21 is used to control the return bypass valve 20 and the frequency control of the pump 12.

[0094] 13 is a functional configuration diagram showing an example of functions of the system control device 30a according to this embodiment. As shown in Fig. 13, the system control device 30a differs from the system control device 30 according to the first embodiment in that the pump frequency is controlled by a pump control unit 46a and that a return bypass valve control unit 47 is further provided.

[0095] [Pump Frequency Control] In this embodiment, the pump control unit 46a controls the multiple pumps 12 so as to reduce the deviation between the pressure measurement value of the primary return header 11a and a preset pressure set value SP. FIG. 14 is a functional configuration diagram showing an example of the function of a frequency control unit 460a included in the pump control unit 46a according to this embodiment. As shown in FIG. 14, the frequency control unit 460a includes, for example, a calculation unit 461a and a correction unit 462. The calculation unit 461a performs PI control on the deviation between the pressure measurement value of the primary return header 11a and the preset pressure set value SP to calculate a frequency command value for the pump 12. The correction unit 462 is similar to that of the first embodiment described above except that it performs correction using the frequency command value calculated by the calculation unit 461a, and therefore a detailed description thereof will be omitted here.

[0096] As described above, in this embodiment, a return bypass pipe 18 is provided between the primary return header 11a and the secondary return header 11b, and a return bypass valve 20 is provided in the return bypass pipe 18. The frequency of the pump 12 is controlled so that the pressure measurement value Pr of the primary return header 11a remains constant at a predetermined set value Ps. This suppresses fluctuations in system pressure that occur when the heat source unit 10 or the pump 12 is increased or decreased in stages, thereby suppressing fluctuations in fluid temperature and preventing abnormal shutdowns of the heat source unit. As a result, stable operation of the heat source system 1a can be achieved. The start and end timing of pump control by the pump control unit and control of the number of pumps can be performed in the same manner as in the first embodiment described above.

[0097] [Return Bypass Valve Control Unit] The return bypass valve control unit 47 controls the valve opening degree of the return bypass valve 20. For example, as shown in Fig. 15 , the return bypass valve control unit 47 starts valve opening degree control when the pressure measurement value Pr of the primary return header 11a reaches a preset control start pressure value SPrs, and ends valve opening degree control of the return bypass valve 20 when the pressure measurement value Pr of the primary return header 11a reaches a control end pressure value SPre that is set to a value smaller than the control start pressure value.

[0098] Here, the control end pressure value SPre and the control start pressure value SPrs are set to values ​​greater than the pressure set value SP of the primary return header 11a and smaller than the pressure set value SPbs of the return bypass valve 20. The return bypass valve control unit 47 controls the valve opening of the return bypass valve 20, for example, so that the pressure measurement value Pr of the primary return header 11a falls within a predetermined pressure range. Specifically, PI control is performed on the deviation between the pressure measurement value Pr of the primary return header 11a and the pressure set value SP of the primary return header 11a, and a valve opening command value βr is calculated.

[0099] Furthermore, when the sum ΣFn (hereinafter simply referred to as the "sum ΣFn") of the fluid flow measurement values ​​(measurement values ​​by the flow sensor 23) of the heat source unit 10 in operation is below a predetermined flow threshold Fts, the return bypass valve control unit 47 controls the return bypass valve 20 based on the sum ΣFn in priority to the control of the return bypass valve 20 based on the pressure measurement value Pr of the above-mentioned primary return header 11a.

[0100] The return bypass valve control unit 47 controls the return bypass valve 20 so that the smaller the combined value ΣFn, the larger the valve opening command value βr of the return bypass valve 20. For example, the valve opening command value βr of the return bypass valve 20 is controlled based on the following equation (9).

[0101] βr=-a×ΣFn (9)

[0102] Here, a is a predetermined coefficient, which is a value obtained by dividing the fluid flow rate value corresponding to the maximum valve opening βr_max of the return bypass valve 20 by the flow rate threshold Fts. Here, the flow rate threshold Fts is set to a value obtained by multiplying the total value of the rated flow rates of the pumps 12 during operation by the predetermined coefficient. The predetermined coefficient may be set in advance to an appropriate value depending on the operation.

[0103] 16 is a diagram showing an example of the relationship between the valve opening command value βr and the combined value ΣFn of the return bypass valve 20. As shown in the above formula (9) and in FIG. 16, the valve opening command value βr is proportionally controlled with respect to the combined value ΣFn.

[0104] For example, if an operating heat source unit 10 suddenly stops operating, the total fluid flow rate ΣFn of the operating heat source unit 10 becomes extremely low. In this case, the circulation flow rate, including the external load, drops sharply, potentially causing the pump 12 to run idle (shutoff operation), resulting in possible breakdown. Therefore, when the total fluid flow rate ΣFn is equal to or less than the predetermined flow rate threshold Fts, control of the return bypass valve 20 based on the total fluid flow rate ΣFn takes precedence over control of the return bypass valve 20 based on the pressure measurement value Pr of the primary return header 11a. In this control, the smaller the total fluid flow rate ΣFn, the greater the valve opening of the return bypass valve 20. This allows fluid to circulate between the pump 12 and the return bypass valve 20—in other words, between the primary return header 11a and the secondary return header 11b—and prevents breakdown of the pump 12. The control of the return bypass valve control unit 47 described above may be combined with the pump control unit 46 according to the first embodiment. In this case, the pump control unit 46 according to the first embodiment may be used in place of the pump control unit 46a according to the second embodiment.

[0105] Although the present disclosure has been described above using each embodiment, the technical scope of the present disclosure is not limited to the scope described in each embodiment. Various modifications or improvements can be made to each embodiment without departing from the gist of the disclosure, and forms incorporating such modifications or improvements are also included in the technical scope of the present disclosure. Furthermore, each embodiment may be appropriately combined. Furthermore, the processing flow described in the above embodiment is merely an example, and unnecessary steps may be deleted, new steps may be added, or the processing order may be rearranged without departing from the gist of the present disclosure.

[0106] For example, in the above-described embodiment, the flow rate adjustment valves are controlled by the system control device 30, but this is not limited to this. For example, the system control device 30 may transmit the target flow rate values ​​of each heat source machine 10 to the heat source machine control devices 50 (50a to 50c) that control each heat source machine 10, and the heat source machine control devices 50a to 50c may control the corresponding flow rate adjustment valves 14a to 14c. In this case, the heat source machine control device 50 has the function of the valve control unit 45.

[0107] The heat source system and the control method and control program thereof described in each of the above-described embodiments can be understood, for example, as follows.

[0108] A heat source system (1) according to a first aspect of the present disclosure comprises a plurality of heat source units connected in parallel to an external load, a return header that collects fluid from the external load, a supply header that collects fluid that has been temperature-adjusted by the heat source units, a plurality of pumps that are provided upstream of the return header in the fluid flow and control the flow rate of fluid supplied to the return header, and a pump control unit that controls the plurality of pumps, wherein the plurality of pumps include variable speed pumps, and the pump control unit controls the number of pumps in operation based on the frequency of the pumps during operation.

[0109] According to the above aspect, the flow rate of fluid from an external load is adjusted by multiple pumps and sent to a return header. The fluid output from the return header is temperature-adjusted in each heat source unit, and the temperature-adjusted fluid is sent to a supply header, and then sent from the supply header to an external load. In such a heat source system, the multiple pumps include variable-speed pumps, so flow rate adjustment is possible by controlling the pump frequency. Furthermore, by controlling the number of operating pumps based on the pump frequency, pump operation start and stop can be performed at appropriate times. This is expected to reduce the transport power of the entire pump, making it possible to achieve energy savings throughout the heat source system.

[0110] In the heat source system (1) according to the second aspect of the present disclosure, in the first aspect, the pump control unit increases the number of operating pumps when the frequency of each pump in operation is equal to or higher than a predetermined increase threshold set to be equal to or lower than the upper frequency limit value of the pump.

[0111] According to the above aspect, it is possible to increase the number of operating pumps at an appropriate timing taking into consideration the frequency of the pumps in operation.

[0112] In the heat source system (1) according to the third aspect of the present disclosure, in the first or second aspect described above, the pump control unit reduces the number of operating pumps when the frequency of each pump in operation is equal to or lower than a predetermined reduction threshold value set to be equal to or higher than the lower limit frequency value of the pump.

[0113] According to the above aspect, it is possible to reduce the number of operating pumps at an appropriate timing taking into consideration the frequency of the pumps in operation.

[0114] In a heat source system (1) according to a fourth aspect of the present disclosure, in any of the first to third aspects, when the number of operating pumps is increased or decreased, the pump control unit prohibits further increase or decrease in the number of operating pumps for a certain period of time.

[0115] According to the above aspect, it is possible to stabilize the load and the pressure in the system.

[0116] A heat source system (1) according to a fifth aspect of the present disclosure is any of the first to fourth aspects, and includes a target flow rate calculation unit that calculates a load target flow rate value using the characteristics of the heat source machine, and the pump control unit includes a calculation unit that calculates a frequency command value for the pump that reduces the deviation between the load target flow rate value and the total fluid flow rate value of the heat source machine, and a correction unit that corrects the frequency command value when the number of operating heat source machines is changed or when the number of operating pumps is changed.

[0117] According to the above aspect, when the number of operating heat source machines or the number of operating pumps is changed, the frequency command value is corrected. This makes it possible to suppress increases or decreases in the fluid flow rate due to changes in the number of operating heat source machines or pumps. This makes it possible to prevent breakdowns or abnormal shutdowns of the heat source machines.

[0118] A heat source system (1) according to a sixth aspect of the present disclosure is the fifth aspect, wherein the correction unit increases the frequency command value when the number of operating heat source machines is increased or the number of operating pumps is decreased.

[0119] According to the above aspect, it is possible to prevent breakdowns and abnormal shutdowns of the heat source machine.

[0120] In the heat source system (1) according to the seventh aspect of the present disclosure, in the fifth or sixth aspect described above, the correction unit reduces the frequency command value when the number of operating heat source machines is reduced or the number of operating pumps is increased.

[0121] According to the above aspect, it is possible to prevent breakdowns and abnormal shutdowns of the heat source machine.

[0122] A heat source system (1) according to an eighth aspect of the present disclosure is any one of the fifth to seventh aspects, wherein the target flow rate calculation unit is provided with a limiter unit that corrects the load target flow rate value to be within an upper and lower limit range, the upper limit of the upper and lower limit range being set to a value equal to or less than the sum of the upper flow rate upper limits of each of the pumps, and the lower limit of the upper and lower limit range being set to a value equal to or greater than the maximum flow rate lower limit of the heat source machines in operation multiplied by the number of operating heat source machines.

[0123] According to the above aspect, since the lower limit of the load target flow rate value is set using the maximum value of the lower limit of the flow rate of the heat source machines currently in operation, it is possible to avoid the heat source machines from stopping due to insufficient flow rate even if the lower limit of the flow rate differs among multiple heat source machines, thereby improving the safety of the operation of the heat source machines.

[0124] A heat source system (1) according to a ninth aspect of the present disclosure is the heat source system of either the first or fourth aspect, wherein the return header includes a primary return header provided downstream of the pump in the fluid flow, and a secondary return header provided upstream of the pump in the fluid flow, and further includes a bypass pipe connecting the primary return header and the secondary return header, and a return bypass valve provided in the bypass pipe, and the pump control unit controls the plurality of pumps so as to reduce the deviation between the pressure measurement value of the primary return header and a preset pressure set value.

[0125] According to the above-mentioned aspect, it is possible to suppress fluctuations in the system pressure that occur when increasing or decreasing the number of stages of the heat source unit or the pump, thereby suppressing fluctuations in fluid temperature and preventing abnormal shutdowns of the heat source unit, thereby realizing stable operation of the heat source system.

[0126] In the heat source system (1) according to the tenth aspect of the present disclosure, in either the first or ninth aspect, the pump control unit starts controlling the pump after the first heat source unit starts operating, and ends controlling the pump after the compressors of all the heat source units have stopped.

[0127] According to the above aspect, it is possible to start and end pump control at appropriate times, thereby reducing unnecessary energy consumption by the pump and achieving energy conservation.

[0128] A heat source system (1) according to an eleventh aspect of the present disclosure is the heat source system of either the first or tenth aspect, wherein the return header includes a primary return header provided downstream of the pump in the fluid flow, and a secondary return header provided upstream of the pump in the fluid flow, and further includes a bypass pipe connecting the primary return header and the secondary return header, a return bypass valve provided in the bypass pipe, and a return bypass valve control unit that controls the valve opening of the return bypass valve.

[0129] According to the above-mentioned aspect, it is possible to suppress fluctuations in the system pressure that occur when increasing or decreasing the number of stages of the heat source unit or the pump, thereby suppressing fluctuations in fluid temperature and preventing abnormal shutdowns of the heat source unit, thereby realizing stable operation of the heat source system.

[0130] In a heat source system (1) according to a twelfth aspect of the present disclosure, in the eleventh aspect described above, the return bypass valve control unit starts valve opening control of the return bypass valve so that the pressure measurement value of the primary return header becomes a predetermined pressure setting value when the pressure measurement value of the primary return header reaches a preset control start pressure, and ends valve opening control of the return bypass valve when the pressure measurement value of the primary return header reaches a control end pressure that is set to a value smaller than the control start pressure.

[0131] According to the above-mentioned aspect, it is possible to suppress fluctuations in the system pressure that occur when increasing or decreasing the number of stages of the heat source unit or the pump, thereby suppressing fluctuations in fluid temperature and preventing abnormal shutdowns of the heat source unit, thereby realizing stable operation of the heat source system.

[0132] In the heat source system (1) according to a thirteenth aspect of the present disclosure, in the eleventh or twelfth aspect, the return bypass valve control unit controls the return bypass valve based on the sum of the fluid flow rates of the heat source units during operation when the sum of the fluid flow rates is equal to or less than a predetermined threshold value.

[0133] According to the above aspect, when the total value of the fluid flow rates of the heat source units in operation is equal to or less than the flow rate threshold, it is possible to control the valve opening of the return bypass valve based on the total value. This control makes it possible to circulate the fluid between the primary return header and the secondary return header by forcibly controlling the valve opening of the return bypass valve to be open. This makes it possible to prevent pump failure due to a decrease in flow rate.

[0134] In a heat source system (1) according to a fourteenth aspect of the present disclosure, in the thirteenth aspect, the return bypass valve control unit controls the return bypass valve so that the valve opening degree of the return bypass valve increases as the combined value decreases.

[0135] According to the above aspect, it is possible to appropriately control the valve opening degree of the return bypass valve.

[0136] A heat source system (1) according to a fifteenth aspect of the present disclosure, in any of the first to fourteenth aspects above, comprises a plurality of flow control valves respectively provided between the return header and each of the heat source machines for adjusting the flow rate of the fluid supplied to the corresponding heat source machine, a target flow rate calculation unit which calculates a load target flow rate value using the characteristics of the heat source machine, a heat source machine flow rate setting unit which sets a target flow rate value for each of the heat source machines in operation based on the load target flow rate value and the characteristics of the heat source machine in operation, and a valve control unit which controls each of the flow control valves based on the target flow rate value of each of the heat source machines.

[0137] According to the above aspect, it is possible to send fluid to the heat source unit at an appropriate flow rate according to the load target flow rate value, thereby realizing safe operation of the heat source system.

[0138] A heat source system (1) according to a sixteenth aspect of the present disclosure comprises a plurality of heat source machines connected in parallel to an external load, a return header that collects fluid from the external load, a supply header that collects fluid that has been temperature-adjusted by the heat source machines, a plurality of pumps that are provided upstream of the return header in the fluid flow and control the flow rate of the fluid supplied to the return header, a target flow rate calculation unit that calculates a load target flow rate value using characteristics of the heat source machines, and a pump control unit that controls the plurality of pumps, wherein the plurality of pumps include variable speed pumps, and the pump control unit comprises a calculation unit that calculates a frequency command value for the pumps that reduces the deviation between the load target flow rate value and the total fluid flow rate value of the heat source machines, and a correction unit that corrects the frequency command value when the number of operating heat source machines is changed or when the number of operating pumps is changed.

[0139] According to the above aspect, when the number of operating heat source machines or the number of operating pumps is changed, the frequency command value is corrected. This makes it possible to suppress increases or decreases in the fluid flow rate due to changes in the number of operating heat source machines or pumps. This makes it possible to prevent breakdowns or abnormal shutdowns of the heat source machines.

[0140] A heat source system (1) according to a seventeenth aspect of the present disclosure comprises a plurality of heat source machines connected in parallel to an external load, a primary return header that collects fluid from the external load, a plurality of pumps that are provided upstream of the primary return header in the fluid flow and control the flow rate of fluid supplied to the primary return header, a secondary return header that is provided upstream of the pumps in the fluid flow, a bypass pipe that connects the primary return header and the secondary return header, a return bypass valve that is provided in the bypass pipe, a supply header that collects fluid that has been temperature-adjusted by the heat source machines, and a pump control unit that controls the plurality of pumps, wherein the plurality of pumps include variable speed pumps, and the pump control unit controls the plurality of pumps so as to reduce the deviation between the pressure measurement value of the primary return header and a preset pressure set value.

[0141] According to the above-mentioned aspect, it is possible to suppress fluctuations in the system pressure that occur when increasing or decreasing the number of stages of the heat source unit or the pump, thereby suppressing fluctuations in fluid temperature and preventing abnormal shutdowns of the heat source unit, thereby realizing stable operation of the heat source system.

[0142] A heat source system (1) according to an eighteenth aspect of the present disclosure includes a plurality of heat source machines connected in parallel to an external load, a primary return header that collects fluid from the external load, a plurality of pumps that are provided upstream of the primary return header in the fluid flow and control the flow rate of fluid supplied to the primary return header, a secondary return header that is provided upstream of the pumps in the fluid flow, a bypass pipe that connects the primary return header and the secondary return header, a return bypass valve that is provided in the bypass pipe, a supply header that collects fluid that has been temperature-adjusted by the heat source machines, and a return bypass valve control unit that controls the return bypass valve.

[0143] According to the above-mentioned aspect, it is possible to suppress fluctuations in the system pressure that occur when increasing or decreasing the number of stages of the heat source unit or the pump, thereby suppressing fluctuations in fluid temperature and preventing abnormal shutdowns of the heat source unit, thereby realizing stable operation of the heat source system.

[0144] A control method for a heat source system according to a 19th aspect of the present disclosure is a control method for a heat source system including a plurality of heat source machines connected in parallel to an external load, a return header that collects fluid from the external load, a supply header that collects fluid that has been temperature-adjusted by the heat source machines, and a plurality of pumps that are provided upstream of the return header in the fluid flow and control the flow rate of fluid supplied to the return header, wherein the plurality of pumps include variable speed pumps, and a computer controls the number of pumps in operation based on the frequency of the pumps during operation.

[0145] A control program for a heat source system according to a twentieth aspect of the present disclosure causes a computer to execute the above control method.

[0146] 1: Heat source system 10 (10a to 10c): Heat source unit 11: Return header 11a: Primary return header 11b: Secondary return header 12 (12a to 12c): Pump 14 (14a to 14c): Flow rate control valve 16: Supply header 17: Main pipe bypass valve 18: Return bypass piping 20: Return bypass valve 21: Pressure sensor 22: Differential pressure sensor 23 (23a to 23c): Flow rate sensor 25: Communication network 30, 30a: System control device 31: CPU 32: Main memory device 33: Secondary memory device 34: Communication interface 35: Input device 36: Output device 41: Information acquisition unit 42: Memory unit 43: Target flow rate calculation unit 44: Heat source unit flow rate setting unit 45 : Valve control unit 46, 46a : Pump control unit 47 : Return bypass valve control unit 50 (50a to 50c) : Heat source machine control device 431 : Calculation unit 432 : Limiter unit 441 : Setting unit 442 : Limiter unit 460, 460a : Frequency control unit 461, 461a : Calculation unit 462 : Correction unit

Claims

1. A heat source system comprising: a plurality of heat source units connected in parallel to an external load; a return header that collects fluid from the external load; a supply header that collects fluid that has been temperature-adjusted by the heat source units; a plurality of pumps that are provided upstream of the return header in the fluid flow and control the flow rate of fluid supplied to the return header; and a pump control unit that controls the plurality of pumps, wherein the plurality of pumps include variable speed pumps, and the pump control unit controls the number of pumps in operation based on the frequency of the pumps during operation.

2. The heat source system of claim 1, wherein the pump control unit increases the number of operating pumps when the frequency of each pump in operation is equal to or greater than a predetermined increase threshold set below the upper frequency limit of that pump.

3. The heat source system of claim 1, wherein the pump control unit reduces the number of operating pumps when the frequency of each pump in operation is below a predetermined reduction threshold set above the lower frequency limit value of that pump.

4. The heat source system according to claim 1, wherein the pump control unit prohibits further increase or decrease in the number of operating pumps for a certain period of time when the number of operating pumps is increased or decreased.

5. A heat source system as described in claim 1, comprising a target flow rate calculation unit that calculates a load target flow rate value using the characteristics of the heat source machine, wherein the pump control unit comprises: a calculation unit that calculates a frequency command value for the pump that reduces the deviation between the load target flow rate value and the total fluid flow rate value of the heat source machine; and a correction unit that corrects the frequency command value when the number of operating heat source machines is changed or when the number of operating pumps is changed.

6. A heat source system as described in claim 5, wherein the correction unit increases the frequency command value when the number of operating heat source machines is increased or when the number of operating pumps is decreased.

7. A heat source system as described in claim 5, wherein the correction unit reduces the frequency command value when the number of operating heat source machines is reduced or when the number of operating pumps is increased.

8. The heat source system of claim 5, wherein the target flow rate calculation unit includes a limiter unit that corrects the load target flow rate value to within an upper and lower limit range, the upper limit of the upper and lower limit range is set to a value that is equal to or less than the sum of the flow rate upper limit values ​​of each of the pumps, and the lower limit of the upper and lower limit range is set to a value that is equal to or greater than the maximum flow rate lower limit value of the heat source machines in operation multiplied by the number of operating heat source machines.

9. The heat source system described in claim 1, wherein the return header includes a primary return header provided downstream of the pump in the fluid flow direction and a secondary return header provided upstream of the pump in the fluid flow direction, a bypass pipe connecting the primary return header and the secondary return header, and a return bypass valve provided in the bypass pipe, and wherein the pump control unit controls the multiple pumps so as to reduce the deviation between the pressure measurement value of the primary return header and a predetermined pressure set value.

10. A heat source system described in any one of claims 1 to 9, wherein the pump control unit starts controlling the pump after the first heat source unit starts operation, and ends controlling the pump after the compressors of all heat source units have stopped.

11. The heat source system described in claim 1, wherein the return header includes a primary return header provided downstream of the pump in the fluid flow direction and a secondary return header provided upstream of the pump in the fluid flow direction, and further comprising: a bypass pipe connecting the primary return header and the secondary return header; a return bypass valve provided in the bypass pipe; and a return bypass valve control unit that controls the valve opening degree of the return bypass valve.

12. The heat source system described in claim 11, wherein the return bypass valve control unit starts valve opening control of the return bypass valve so that the pressure measurement value of the primary return header becomes a predetermined pressure setting value when the pressure measurement value of the primary return header reaches a predetermined control start pressure, and ends valve opening control of the return bypass valve when the pressure measurement value of the primary return header reaches a control end pressure that is set to a value smaller than the control start pressure.

13. The heat source system of claim 11, wherein the return bypass valve control unit controls the return bypass valve based on the combined value of the fluid flow rates of the heat source units during operation when the combined value is below a predetermined threshold value.

14. The heat source system according to claim 13, wherein the return bypass valve control unit controls the return bypass valve so that the smaller the total value, the larger the valve opening of the return bypass valve.

15. A heat source system as described in claim 1, comprising: a plurality of flow control valves respectively provided between the return header and each of the heat source machines for adjusting the flow rate of fluid supplied to the corresponding heat source machine; a target flow rate calculation unit which calculates a load target flow rate value using characteristics of the heat source machine; a heat source machine flow rate setting unit which sets a target flow rate value for each of the heat source machines in operation based on the load target flow rate value and characteristics of the heat source machine in operation; and a valve control unit which controls each of the flow control valves based on the target flow rate value of each of the heat source machines.

16. A heat source system comprising: a plurality of heat source machines connected in parallel to an external load; a return header that collects fluid from the external load; a supply header that collects fluid that has been temperature-adjusted by the heat source machines; a plurality of pumps that are provided upstream of the return header in the fluid flow and control the flow rate of fluid supplied to the return header; a target flow rate calculation unit that calculates a load target flow rate value using characteristics of the heat source machines; and a pump control unit that controls the plurality of pumps, wherein the plurality of pumps include variable speed pumps, and the pump control unit comprises: a calculation unit that calculates a frequency command value for the pumps that reduces the deviation between the load target flow rate value and the total fluid flow rate value of the heat source machines; and a correction unit that corrects the frequency command value when the number of operating heat source machines is changed or when the number of operating pumps is changed.

17. A heat source system comprising: a plurality of heat source machines connected in parallel to an external load; a primary return header that collects fluid from the external load; a plurality of pumps that are provided upstream of the fluid flow of the primary return header and control the flow rate of fluid supplied to the primary return header; a secondary return header that is provided upstream of the fluid flow of the plurality of pumps; a bypass piping that connects the primary return header and the secondary return header; a return bypass valve provided in the bypass piping; a supply header that collects fluid that has been temperature-adjusted by the heat source machines; and a pump control unit that controls the plurality of pumps, wherein the plurality of pumps include variable speed pumps, and the pump control unit controls the plurality of pumps so as to reduce the deviation between the pressure measurement value of the primary return header and a predetermined pressure set value.

18. A heat source system comprising: a plurality of heat source machines connected in parallel to an external load; a primary return header that collects fluid from the external load; a plurality of pumps that are provided upstream of the fluid flow of the primary return header and control the flow rate of fluid supplied to the primary return header; a secondary return header that is provided upstream of the fluid flow of the plurality of pumps; a bypass pipe that connects the primary return header and the secondary return header; a return bypass valve that is provided in the bypass pipe; a supply header that collects fluid that has been temperature-adjusted by the heat source machines; and a return bypass valve control unit that controls the return bypass valve.

19. A control method for a heat source system comprising a plurality of heat source units connected in parallel to an external load, a return header that collects fluid from the external load, a supply header that collects fluid whose temperature has been adjusted by the heat source units, and a plurality of pumps that are provided upstream of the return header in the fluid flow and control the flow rate of fluid supplied to the return header, wherein the plurality of pumps include variable speed pumps, and a computer controls the number of pumps in operation based on the frequency of the pumps during operation.

20. A control program for causing a computer to execute the control method according to claim 19.

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