Heat source system, control method therefor, and control program

Abstract

The present invention improves the operation safety of a heat source system in which a fluid to be supplied to a plurality of heat source machines is pumped by means of a plurality of common pumps. The heat source system comprises: a plurality of heat source machines; a plurality of flow-rate-regulating valves that regulate the flow rate of a fluid to be supplied to the corresponding heat source machines; a target flow-rate calculation unit (43) that calculates a target load flow rate value by using the characteristics of the heat source machines; a heat-source machine flow-rate setting unit (44) that sets a target flow rate value for each of the heat source machines in operation on the basis of the target load flow rate value and the characteristics of the heat source machines in operation; and a valve control unit (45) that controls the flow-rate-regulating valves on the basis of the target flow rate values for the heat source machines.

Description

Heat source system, control method and control program

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

[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 aims to provide a heat source system, a control method and a control program therefor that can improve the safety of operation of a heat source system in which fluid supplied to multiple heat source machines is pressurized by multiple common pumps.

[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 the fluid supplied to the return header; a plurality of flow control valves that are provided between the return header and each of the heat source units and adjust the flow rate of the fluid supplied to the corresponding heat source unit; a target flow rate calculation unit that calculates a load target flow rate value using characteristics of the heat source units; a heat source unit flow rate setting unit that sets a target flow rate value for each of the heat source units that is operating based on the load target flow rate value and the characteristics of the heat source units that are operating; and a valve control unit that controls each of the flow control valves based on the target flow rate value of each of the heat source units.

[0007] One 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, 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, and a plurality of flow control valves that are provided between the return header and each of the heat source machines and adjust the flow rate of the fluid supplied to the corresponding heat source machine, in which a computer calculates a load target flow rate value using characteristics of the heat source machines, sets a target flow rate value for each of the heat source machines that is operating based on the load target flow rate value and the characteristics of the heat source machines that are operating, and controls each of the flow control valves based on the target flow rate value of each of the heat source machines.

[0008] One aspect of the present disclosure is a control program for causing a computer to execute the above control method.

[0009] According to the present disclosure, it is possible to improve the safety of 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.

[0010] FIG. 1 is a diagram showing a schematic configuration of a heat source system according to an embodiment of the present disclosure. FIG. 2 is a diagram showing a schematic configuration of a control system of a heat source system according to an 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 an embodiment of the present disclosure. FIG. 4 is a functional configuration diagram showing an example of a function provided in a system control device according to an embodiment of the present disclosure. FIG. 5 is a diagram showing an example configuration of a target flow rate calculation unit according to an embodiment of the present disclosure. FIG. 6 is a diagram showing an example configuration of a heat source machine flow rate setting unit according to an 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 a heat source machine flow rate setting unit according to an embodiment of the present disclosure. FIG. 8 is a flowchart showing an example procedure of a valve control method according to an embodiment of the present disclosure. FIG. 9 is a flowchart showing an example procedure of a pump operation control method according to an embodiment of the present disclosure.

[0011] A heat source system, a control method thereof, and a control program thereof according to an embodiment of the present disclosure will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a schematic configuration of a heat source system 1 according to an 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.

[0012] 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.

[0013] 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 fixed-speed pump.

[0014] 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.

[0015] 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 transmitted to a system control device 30. The system control device 30 controls the pump 12, the flow rate adjustment valve 14, the main pipe bypass valve 17, and the like using the measurements from the various sensors. Although not shown in the heat source system 1, a primary bypass pipe is provided between the primary return header 11a and the secondary return header 11b, and a primary bypass valve may be provided in the bypass pipe.

[0016] 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 a plurality of heat source units 10, and the flow rate of the fluid supplied to the external load is adjusted by controlling the number of pumps 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 for 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] [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.

[0026] [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.

[0027] [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.

[0028] 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.

[0029] 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.

[0030] 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).

[0031] Lower limit value = total value of lower limit flow rate of heat source units in operation × C1 (1)

[0032] 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.

[0033] 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).

[0034] Lower limit value = Maximum flow rate lower limit value of heat source units in operation × Number of operating units × C2 (2)

[0035] 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].

[0036] 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.

[0037] 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.

[0038] [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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] [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.

[0044] 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. After the compressor of the heat source machine 10 stops, the valve control unit 45 ends valve control of the flow rate adjustment valve 14 corresponding to that heat source machine 10. The valve control unit 45 maintains the valve opening at the time the operation stop signal was sent to the heat source machine 10 during the period from when the operation stop signal was 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.

[0045] 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.

[0046] (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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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).

[0051] [Pump Control Unit] The pump control unit 46 controls the number of operating pumps 12 based on the load target flow rate value set by the target flow rate calculation unit 43. The pump control unit 46 starts controlling the pumps 12 after the first heat source unit 10 starts operating, and ends controlling the pumps 12 after the compressors of all the heat source units 10 have stopped. 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 flow rate lower limit value of the pump 12. Furthermore, after starting pump control, the pump control unit 46 increases or decreases the number of operating pumps 12 according to the load target flow rate value.

[0052] For example, the pump control unit 46 increases the number of operating pumps when the following condition for increasing the number of pumps is satisfied.

[0053] Increase condition: Fg≧ΣPrate×C3 (3)

[0054] In the above formula (3), Fg is the load target flow rate value, Prate is the total value of the rated flow rates of the operating pumps 12, and C3 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 increases the number of operating pumps 12 when the load target flow rate value is greater than the value obtained by multiplying the total value of the rated flow rates of the operating pumps 12 by the predetermined correction value.

[0055] The pump control unit 46 reduces the number of operating pumps 12 when the following reduction conditions are met.

[0056] Stage reduction condition: Fg≦ΣPe_rate×C4 (4)

[0057] In the above formula (4), 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 C4 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.

[0058] 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.

[0059] 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.

[0060] Next, it is determined whether the step-up condition is satisfied (SB4). If the step-up condition is satisfied (SB4: YES), it is determined whether a predetermined period 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 unstable, 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. If, in step SB5, the predetermined period has not elapsed since the previous change in the number of operating pumps (SB5: NO), the system waits until the predetermined period has elapsed, and after the predetermined period has elapsed (SB5: YES), the system starts the operation of the start pump (SB6). The next start pump to be started is then determined (SB7), and the process returns to step SB4. If all pumps 12 are in operation, step SB7 is omitted.

[0061] If the determination in step SB4 is negative (SB4: NO), the process determines whether the step-down condition is met (SB8). If the result is that the step-down condition is not met (SB8: NO), the process returns to step SB4 and performs transition processing. On the other hand, if the step-down condition is met (SB8: YES), the process determines whether a predetermined period has elapsed since the previous change in the number of operating units (SB9). If the result is that the predetermined period has not elapsed since the previous change in the number of operating units (SB9: NO), the process waits until the predetermined period has elapsed, and after the predetermined period has elapsed (SB9: YES), the process stops operation of the stopped pump (SB10). Thereafter, the next stopped pump to be started is determined (SB11), and the process returns to step SB4.

[0062] 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 sent from the supply header 16 to the external load. In this heat source system 1, a load target flow rate value is calculated using the characteristics of the heat source unit 10, and target flow rate values ​​for each operating heat source unit are set based on the load target flow rate value. This makes it possible to control the fluid flow rate taking into account the characteristics of each heat source unit, thereby achieving stable operation of the heat source system.

[0063] Although the present disclosure has been described above using embodiments, the technical scope of the present disclosure is not limited to the scope described in the above embodiments. Various modifications or improvements can be made to the above embodiments 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. The above embodiments may also be combined as appropriate. The processing flow described in the above embodiments is also 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.

[0064] 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.

[0065] The heat source system and the control method and control program thereof described in the embodiment described above can be understood, for example, as follows.

[0066] A heat source system (1) according to a first aspect of the present disclosure comprises a plurality of heat source machines (10) connected in parallel to an external load, a return header (11a) that collects fluid from the external load, a supply header (16) that collects fluid temperature-adjusted by the heat source machines, a plurality of pumps (12) 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 plurality of flow control valves (12) that are provided between the return header and each of the heat source machines and adjust the flow rate of the fluid supplied to the corresponding heat source machine, a target flow rate calculation unit (43) that calculates a load target flow rate value using characteristics of the heat source machines, a heat source machine flow rate setting unit (44) that 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 (45) that controls each of the flow control valves based on the target flow rate value of each of the heat source machines.

[0067] According to the above aspect, the flow rate of fluid from the external load is adjusted by multiple pumps and sent to the return header. The flow rate of the fluid output from the return header is adjusted by flow control valves provided corresponding to each heat source unit and sent to each heat source unit. The fluid whose temperature has been adjusted in each heat source unit is sent to the supply header and sent from the supply header to the external load. In such a heat source system, a load target flow rate value is calculated using the characteristics of the heat source units, and target flow rate values ​​for the operating heat source units are set based on the load target flow rate value. This makes it possible to control the fluid flow rate taking into account the characteristics of each heat source unit, thereby achieving stable operation of the heat source system.

[0068] In the heat source system (1) according to the second aspect of the present disclosure, in the first aspect, the target flow rate calculation unit (43) is provided with a limiter unit (432) that corrects the load target flow rate value to be within an upper and lower limit range, and the upper limit of the upper and lower limit range is set to a value equal to or less than the sum of the upper flow rate upper limits of the pumps, and the lower limit of the upper and lower limit range is 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.

[0069] 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.

[0070] In the heat source system (1) according to the third aspect of the present disclosure, in the first or second aspect described above, the heat source unit flow rate setting unit (44) is provided with a limiter unit (442) that corrects the target flow rate value of each of the heat source units to within an upper and lower limit range, the upper limit value of the upper and lower limit range being set to the upper flow rate upper limit value of each of the heat source units, and the lower limit value of the upper and lower limit range being set to the highest flow rate lower limit value among the heat source units currently in operation.

[0071] According to the above aspect, the highest flow rate lower limit value among the heat source units in operation is set as the lower limit value of the limiter unit. This makes it possible to avoid emergency shutdowns or abnormal shutdowns of the heat source units due to insufficient fluid flow rates, even if the lower limit flow rates differ between the heat source units.

[0072] In the heat source system (1) according to the fourth aspect of the present disclosure, in any of the first to third aspects, the valve control unit (45) starts controlling the opening degree of the flow control valve after the first heat source machine starts operating, and ends controlling the opening degree of the flow control valve after the compressors of all the heat source machines have stopped.

[0073] For example, when an operation stop signal is output to a heat source machine, the compressor of the heat source machine continues to operate for a certain period of time. Therefore, by controlling the valve opening of the flow control valve until the compressor of the heat source machine stops, it is possible to continue sending an appropriate flow rate of fluid to the heat source machine, and it is possible to safely stop the heat source machine.

[0074] In the heat source system (1) according to the fifth aspect of the present disclosure, in any of the first to fourth aspects, when an operation stop signal is sent to any of the heat source machines, the valve control unit (45) holds the valve opening command value of the flow control valve corresponding to that heat source machine for a predetermined period of time.

[0075] According to the above aspect, when an operation stop signal is sent to the heat source machine, the valve opening of the flow control valve is maintained until the compressor of the heat source machine stops. This makes it possible to continue to supply a sufficient flow rate of fluid to the heat source machine, and to safely stop the heat source machine.

[0076] A heat source system (1) according to a sixth aspect of the present disclosure is any one of the first to fifth aspects, wherein the valve control unit (45) comprises a calculation unit that calculates a valve opening command value of the flow control valve corresponding to each of the heat source machines based on the target flow rate value of each of the heat source machines currently in operation, and a correction unit that corrects the valve opening command value calculated by the calculation unit, and the correction unit increases the valve opening command value when the maximum valve opening of the flow control valve corresponding to the heat source machine currently in operation is smaller than an opening threshold value that is set based on an upper opening value, and when the frequency command value of the pump is larger than a frequency threshold value that is set based on a lower frequency value.

[0077] According to the above aspect, when the maximum valve opening of the flow control valve corresponding to the heat source unit in operation is smaller than the opening threshold value set based on the opening upper limit value, and when the pump frequency command value is greater than the frequency threshold value set based on the frequency lower limit value, control is performed to increase the valve opening command value. This makes it possible to circulate the fluid delivered from the pump as efficiently as possible. As a result, it is possible to reduce unnecessary energy consumption in the pump.

[0078] A control method for a heat source system according to a seventh aspect of the present disclosure is a control method for 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, and a plurality of flow control valves that are provided between the return header and each of the heat source machines and adjust the flow rate of fluid supplied to the corresponding heat source machine, wherein a computer calculates a load target flow rate value using characteristics of the heat source machines, sets a target flow rate value for each of the heat source machines that is operating based on the load target flow rate value and the characteristics of the heat source machines that are operating, and controls each of the flow control valves based on the target flow rate value of each of the heat source machines.

[0079] A control program for a heat source system according to an eighth aspect of the present disclosure causes a computer to execute the above control method.

[0080] 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 21: Pressure sensor 22: Differential pressure sensor 23 (23a to 23c): Flow rate sensor 25: Communication network 30: 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: Pump control unit 50 (50a to 50c) : Heat source machine control device 431 : Calculation unit 432 : Limiter unit 441 : Setting unit 442 : Limiter unit

Claims

1. 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 plurality of flow control valves that are provided between the return header and each of the heat source machines and adjust the flow rate of fluid supplied to the corresponding heat source machine; a target flow rate calculation unit that calculates a load target flow rate value using characteristics of the heat source machines; a heat source machine flow rate setting unit that sets a target flow rate value for each of the heat source machines that is operating based on the load target flow rate value and the characteristics of the heat source machine that is operating; and a valve control unit that controls each of the flow control valves based on the target flow rate value of each of the heat source machines.

2. The heat source system of claim 1, 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 less than or equal to 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 greater than or equal to the maximum flow rate lower limit value of the heat source machines in operation multiplied by the number of operating heat source machines.

3. The heat source system of claim 1, wherein the heat source unit flow rate setting unit includes a limiter unit that corrects the target flow rate value of each of the heat source units to within an upper and lower limit range, the upper limit of the upper and lower limit range is set to the upper flow rate limit value of each of the heat source units, and the lower limit of the upper and lower limit range is set to the highest flow rate lower limit value among the heat source units currently in operation.

4. The heat source system of claim 1, wherein the valve control unit starts controlling the opening degree of the flow control valve after the first heat source unit starts operation, and ends controlling the opening degree of the flow control valve after the compressors of all the heat source units have stopped.

5. A heat source system as described in claim 1, wherein the valve control unit holds the valve opening command value of the flow control valve corresponding to any of the heat source machines for a predetermined period of time when an operation stop signal is sent to that heat source machine.

6. The heat source system described in claim 1, wherein the valve control unit comprises: a calculation unit that calculates a valve opening command value for the flow control valve corresponding to each of the heat source machines based on the target flow rate value of each of the heat source machines currently in operation; and a correction unit that corrects the valve opening command value calculated by the calculation unit, wherein the correction unit increases the valve opening command value when the maximum valve opening of the flow control valve corresponding to the heat source machine currently in operation is smaller than an opening threshold value set based on an upper opening value, and when the frequency command value of the pump is larger than a frequency threshold value set based on a lower frequency limit value.

7. A control method for 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, and a plurality of flow control valves that are provided between the return header and each of the heat source machines and adjust the flow rate of fluid supplied to the corresponding heat source machine, wherein a computer calculates a load target flow rate value using the characteristics of the heat source machines, sets a target flow rate value for each of the heat source machines that is operating based on the load target flow rate value and the characteristics of the heat source machines that are operating, and controls each of the flow control valves based on the target flow rate value of each of the heat source machines.

8. A control program for causing a computer to execute the control method according to claim 7.

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