JP5379650B2 - Primary pump type heat source variable flow rate control system and method - Google Patents

Description

  The present invention relates to a primary pump type heat source variable flow rate control system and method for controlling the rotational speed of a primary pump that conveys heat source water.

  FIG. 13 shows an instrumentation diagram of a conventional primary pump heat source variable flow rate control system. In the figure, 1 is a heat source device that generates heat source water, 2 is a primary pump that conveys heat source water generated by the heat source device 1, 3 is an inverter attached to the primary pump 2, and 4 is from the heat source device 1. Outer header that receives heat source water, 5 is an outgoing water line, 6 is an external load that receives supply of heat source water sent from the outgoing header 4 via the outgoing water line 5 (heat load such as air conditioner and fan coil, area, etc. 7 is a return water pipe. The external load 6 is provided with a valve 6-1 for adjusting the flow rate of supplied heat source water.

  8 is a return header in which heat is exchanged in the external load 6 and returned to the heat source water sent via the return water pipe 7, 9 is a bypass pipe that connects the forward header 4 and the return header 8, and 10 is a bypass pipe A bypass valve provided in 9, a differential pressure gauge 11 that measures the differential pressure between the heat source water between the forward header 4 and the return header 8 (inter-header differential pressure) as the forward / backward differential pressure ΔPpv of the heat source water to the external load 6 , 12 are control devices.

  In this primary pump type heat source variable flow rate control system, the heat source water pumped by the primary pump 2 is cooled or heated by the heat source unit 1 to reach the forward header 4 and to the external load 6 via the forward water line 5. Supplied. Then, heat is exchanged in the external load 6, returned to the return header 8 through the return water pipe 7, and pumped again by the primary pump 2, and circulates through the above path. For example, when the heat source device 1 is a refrigerator, the heat source water is cold water and circulates through the above-described path. When the heat source device 1 is a heater, the heat source water is warm water and circulates in the above-described path.

(Constant pressure control)
The control device 12 monitors the return differential pressure ΔPpv measured by the differential pressure gauge 11, and controls the rotational speed of the primary pump 2 so that the return differential pressure ΔPpv is constant. That is, the return differential pressure ΔPpv measured by the differential pressure gauge 11 is compared with a preset differential pressure ΔPsp, and the inverter output INV for controlling the rotational speed to the primary pump 2 is set so that ΔPpv = ΔPsp. (INV = 0 to 100%) and the valve opening output θ for opening control to the bypass valve 10 (θ = 0 to 100%) are adjusted.

In this constant pressure control, a lower limit set value INV _MIN is determined for the inverter output INV to the primary pump 2. This lower limit set value INV _MIN is determined for the following reason. In the primary pump type heat source variable flow rate control system, when the flow rate of the heat source water passing through the heat source unit 1 falls below a predetermined flow rate, there is a possibility that an abnormality may occur in the heat source unit 1. The predetermined flow rate at this time is called the minimum flow rate. For example, when the heat source device 1 is a refrigerator, there is a risk of freezing if the flow rate of the passing cold water falls below the minimum flow rate _QMIN . For this reason, as a fail-safe function of the heat source unit 1 itself, when the flow rate of the passing heat source water falls below the minimum flow rate Q _MIN , a function is provided in which the water cutoff relay is activated and the operation of the heat source unit 1 is automatically stopped. Yes. The lower limit set value INV _MIN that can secure the minimum flow rate Q _MIN to the heat source unit 1 for the inverter output INV to the primary pump 2 so that the fail safe function of the heat source unit 1 does not work during the constant pressure control. (See, for example, Patent Documents 1, 2, and 3).

[Constant pressure control by primary pump speed: INV ≧ INV _MIN ]
When the flow rate required by the external load 6 is reduced and the opening / closing pressure of the valve 6-1 is reduced, and the return differential pressure ΔPpv increases, the control device 12 causes the primary pump so that ΔPpv = ΔPsp. The inverter output INV to 2 is decreased (the rotational speed of the primary pump 2 is decreased). Here, when the inverter output INV obtained internally is equal to or higher than the lower limit set value INV _MIN , the control device 12 sends a valve opening output θ of 0% to the bypass valve 10 to fully close the bypass valve 10. And This is referred to as constant pressure control by the primary pump rotation speed (see region S1 shown in FIG. 14).

[Constant pressure control by opening of bypass valve: INV <INV _MIN ]
When the inverter output INV obtained internally becomes smaller than the lower limit set value INV _MIN , the control device 12 regulates the inverter output INV to the primary pump 2 so as not to fall below the lower limit set value INV _MIN . That is, the inverter output INV to the primary pump 2 is set to INV _MIN . In this case, the control device 12 controls the opening degree of the bypass valve 10 so that ΔPpv = ΔPsp. This is referred to as constant pressure control based on the bypass valve opening (see region S2 shown in FIG. 14).

In the constant pressure control based on the opening degree of the bypass valve, the inverter output INV to the primary pump 2 is restricted to the lower limit set value INV _MIN , so that the minimum flow rate Q _MIN to the heat source unit 1 is secured. For this reason, the flow rate of the heat source water passing through the heat source unit 1 does not fall below the minimum flow rate Q _MIN, and the fail safe function of the heat source unit 1 does not work. Of this minimum flow rate Q _MIN , the surplus with respect to the load flow rate QF to the external load 6 flows through the bypass line 9 as the bypass flow rate QB.

JP 2006-38379 A JP 2002-98358 A JP 2004-101104 A

However, in the conventional primary pump type heat source variable flow rate control system described above, the fail safe function of the heat source unit 1 may work when the set differential pressure ΔPsp is increased (Problem 1). The lower limit set value INV _MIN of the inverter output is set to a higher setting so that there is no error. If the set differential pressure ΔPsp is lowered at this time, the bypass flow rate QB increases and energy is increased (Problem 2), and even if the change control of the set differential pressure ΔPsp is performed, a sufficient energy saving effect cannot be obtained. It was.

FIG. 15 shows the relationship between the set differential pressure ΔPsp, the minimum flow rate Q _MIN to the heat source unit 1 and the lower limit set value INV _MIN of the inverter output to the primary pump 2. In FIG. 15, characteristic I shows the relationship between the pump pressure and the flow rate of the primary pump 2 when the inverter output INV is 100%, and characteristic II shows the primary pump 2 when the inverter output INV is the lower limit set value INV _MIN. The characteristic III shows the relationship between the required pressure (pump required pressure) and the flow rate of the primary pump 2 for setting the return differential pressure ΔPpv to the set differential pressure ΔPsp. In the characteristic III, the required pump pressure is the secondary side pressure (ΔPsp) + the primary side pressure loss (the square of the flow rate), so a secondary curve as shown in the figure is obtained. In such a relationship, the lower limit set value INV _MIN of the inverter output is determined so that the flow rate at the intersection P1 of the characteristic II and the characteristic III becomes the minimum flow rate Q _MIN to the heat source unit 1.

[Problem when the set differential pressure ΔPsp is increased (Problem 1)]
Here, it is assumed that the set differential pressure ΔPsp is increased to ΔPsp ′. In this case, the characteristic III indicating the relationship between the required pump pressure and the flow rate is shifted up like the characteristic III ′ shown in FIG. For this reason, the flow rate at the intersection P1 ′ between the characteristic II and the characteristic III ′ becomes smaller than the minimum flow rate Q _MIN to the heat source unit 1, and the fail safe function of the heat source unit 1 may be activated.

[Problem when the set differential pressure ΔPsp is lowered (Problem 2)]
On the other hand, it is assumed that the set differential pressure ΔPsp is lowered to ΔPsp ″. In this case, the characteristic III indicating the relationship between the pump required pressure and the flow rate is shifted down as shown by the characteristic III ″ shown in FIG. For this reason, the flow rate at the intersection P1 ″ of the characteristic II and the characteristic III ″ becomes larger than the minimum flow rate Q _MIN to the heat source unit 1, the bypass flow rate QB increases, and the energy increases.

  In the above, the primary pump system heat source variable flow rate in which the difference between the supply pressure and return pressure of the heat source water to the external load is measured as the return differential pressure, and the return differential pressure is made to coincide with the set differential pressure. Although the control system has been described, the same problem occurs in the primary pump heat source variable flow rate control system in which the water supply pressure to the external load is measured and the water supply pressure is made to coincide with the set water supply pressure.

  The present invention has been made to solve such a problem, and the object of the present invention is to provide a primary pump heat source variable flow rate capable of performing a change control of a set differential pressure or a set water supply pressure without hindrance. It is to provide a control system and method.

  In order to achieve such an object, the present invention provides a heat source device that generates heat source water, a primary pump that conveys the heat source water generated by the heat source device, and an external load that receives supply of the heat source water from the heat source device. A heat source water outgoing water line from the heat source unit to the external load, a return water line from the external load to the heat source water to the heat source unit, a bypass line that connects the outgoing water line and the return water line, The difference between the bypass valve provided in the bypass pipe and the supply pressure and return pressure of the heat source water to the external load is defined as the return differential pressure, and the primary pump is set so that the return differential pressure matches the set differential pressure. In a primary pump type heat source variable flow rate control system having a control means for adjusting an inverter output for controlling the number of revolutions and an opening degree output for controlling the opening degree to the bypass valve, the control means includes a set differential pressure Is set for the set differential pressure and heat source when Inverter output lower limit value storage means for storing the relationship with the lower limit value of the inverter output to the primary pump that can secure the minimum flow rate, and the set differential pressure and the inverter output lower limit value stored in the inverter output lower limit value storage means The inverter output lower limit value acquisition means for acquiring the lower limit value of the inverter output corresponding to the current set differential pressure from the relationship with the value, and the inverter output lower limit value acquired by the inverter output lower limit value acquisition means for the current set difference Inverter output restriction means for regulating the inverter output to the primary pump so as not to fall below the lower limit set value.

  In the present invention, the lower limit value of the inverter output to the primary pump that can secure the minimum flow rate to the heat source unit is determined as the relationship between the set differential pressure when the set differential pressure is changed and the lower limit value of the inverter output. It has been. For example, the horizontal axis is the set differential pressure, the vertical axis is the lower limit value of the inverter output, and stored as a table or expression indicating the relationship between the set differential pressure represented by the horizontal axis and the vertical axis and the lower limit value of the inverter output. Has been. The relationship between the set differential pressure and the lower limit value of the inverter output may be a relationship obtained by changing the set differential pressure by at least two points as a theoretical value, or obtained as a real value by changing the set differential pressure by at least two points. It may be a relationship.

  In the present invention, the lower limit value of the inverter output corresponding to the current set differential pressure is obtained from the relationship between the set differential pressure and the lower limit value of the inverter output, and the obtained lower limit value of the inverter output is determined by the current set differential pressure. The inverter output to the primary pump is regulated so as not to fall below this lower limit set value. For example, if the set differential pressure is increased, the lower limit value of the inverter output corresponding to the increased set differential pressure is acquired, and the acquired lower limit value of the inverter output is set as the lower limit set value of the inverter output. The inverter output to the primary pump is regulated so as not to fall below. If the set differential pressure is lowered, the lower limit value of the inverter output corresponding to the lowered set differential pressure is obtained, and the obtained lower limit value of the inverter output is set as the lower limit set value of the inverter output. The inverter output to the primary pump is regulated so as not to fall below.

  In this way, in the present invention, when the set differential pressure is changed, the lower limit set value of the inverter output is changed according to the set differential pressure, and the minimum flow rate to the heat source machine is reduced by the changed lower set value. It will be secured. Therefore, even if the set differential pressure is changed, the fail-safe function of the heat source machine does not work or increase energy, and the change control of the set differential pressure can be performed without any trouble.

  As a modification of the present invention, according to the relationship between the set differential pressure stored in the inverter output lower limit value storage means and the lower limit value of the inverter output, not the current set differential pressure but the current return differential pressure is used. A lower limit value of the inverter output may be acquired.

  As a modification of the present invention, the water supply pressure of the heat source water to the external load may be used instead of the return differential pressure, and the set water supply pressure may be used instead of the set differential pressure. In this case, the control means adjusts the inverter output for controlling the rotational speed to the primary pump so that the water supply pressure of the heat source water to the external load matches the set water supply pressure. Further, the inverter output lower limit value storage means includes the lower limit value of the inverter output to the primary pump that can secure the set water supply pressure when the set water supply pressure is changed and the minimum flow rate determined for the heat source unit. The inverter output lower limit value acquisition means stores the current set water supply pressure (or current water supply pressure) from the relation between the set water supply pressure stored in the inverter output lower limit value storage means and the lower limit value of the inverter output. The lower limit value of the inverter output corresponding to the inverter output is obtained, and the inverter output restricting means uses the inverter output lower limit value obtained by the inverter output lower limit value obtaining means as the inverter output at the current set water supply pressure (or current water supply pressure). The inverter output to the primary pump is regulated so as not to fall below the lower limit set value.

  According to the present invention, the relationship between the set differential pressure when the set differential pressure is changed and the lower limit value of the inverter output to the primary pump that can secure the minimum flow rate determined for the heat source unit is determined. The lower limit value of the inverter output corresponding to the current set differential pressure (or the current return differential pressure) is obtained from the relationship between the set differential pressure and the lower limit value of the inverter output, and the obtained lower limit value of the inverter output is The lower limit set value of the inverter output at the set differential pressure (or the current return differential pressure) is set so that the inverter output to the primary pump is regulated so as not to fall below this lower set value. Even if it is changed, the fail-safe function of the heat source machine does not work or increase energy, and the control of changing the set differential pressure can be performed without any trouble.

  In addition, according to the present invention, the water supply pressure of the heat source water to the external load is used instead of the return differential pressure, and the set differential pressure is used instead of the set differential pressure. As in the case of use, even if the set water supply pressure is changed, the fail safe function of the heat source machine does not work or increase energy, and the change control of the set water pressure can be performed without any trouble. It becomes like this.

1 is an instrumentation diagram of a primary pump type heat source variable flow rate control system (primary pump type heat source variable flow rate control system configured to control a return differential pressure constant) according to an embodiment of the present invention. It is a functional block diagram of the principal part of the control apparatus in this primary pump system heat source variable flow control system. It is a figure which illustrates the table which shows the relationship between the setting differential pressure | voltage calculated | required as a theoretical value memorize | stored in the inverter output lower limit memory | storage part of this control apparatus, and the lower limit value of an inverter output. It is a figure explaining how to obtain | require the lower limit (theoretical value) of an inverter output at the time of creating the table which shows the relationship between setting differential pressure and the lower limit of an inverter output. It is a flowchart which shows the specific process operation | movement in this control apparatus. It is a figure which illustrates the data used when calculating | requiring the relationship between setting differential pressure | voltage and the lower limit of an inverter output as an actual value. It is a figure which illustrates the table which shows the relationship between the setting differential pressure calculated | required as an actual value, and the lower limit of an inverter output. It is an instrumentation diagram of a primary pump type heat source variable flow rate control system when the set differential pressure is changed according to the load flow rate. It is a flowchart which shows the specific process operation | movement in a control apparatus at the time of changing a setting differential pressure according to load flow volume. It is an instrumentation diagram of a primary pump system heat source variable flow rate control system that controls the water supply pressure to be constant. It is a flowchart which shows the specific process operation | movement in the control apparatus at the time of making it control water supply pressure uniformly. It is a flowchart which shows the specific process operation | movement in a control apparatus at the time of changing a setting water supply pressure according to load flow volume. It is an instrumentation figure of the conventional primary pump system heat source variable flow control system. It is a figure explaining the pressure constant control by the primary pump rotation speed and the pressure constant control by a bypass valve opening degree in this primary pump system heat source variable flow control system. It is a figure which shows the relationship between the setting differential pressure | voltage in this primary pump system heat source variable flow control system, the minimum flow volume to a heat source machine, and the minimum setting value of the inverter output to a primary pump. It is a figure explaining the problem at the time of raising the setting differential pressure in this primary pump system heat source variable flow control system. It is a figure explaining the problem at the time of lowering the setting differential pressure in this primary pump system heat source variable flow control system.

  Hereinafter, the present invention will be described in detail based on embodiments. FIG. 1 is an instrumentation diagram of a primary pump type heat source variable flow rate control system showing an embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 13 denote the same or equivalent components as those described with reference to FIG. 13, and the description thereof will be omitted.

  This embodiment is different from the conventional primary pump type heat source variable flow rate control system in the function of the control device 12. The control device 12 is realized by hardware including a processor and a storage device, and a program that realizes various functions in cooperation with these hardware. As a function unique to this embodiment, a lower limit setting value of the inverter output Has a change function. FIG. 2 shows a functional block diagram of the main part of the control device 12 including the function of changing the lower limit set value of the inverter output.

The control device 12 is a table TB1 (described later) showing the relationship between the set differential pressure ΔPsp and the lower limit value INV _MIN of the inverter output to the primary pump 2 that can secure the minimum flow rate Q _MIN determined for the heat source unit 1. ) Stored in the inverter output lower limit value storage unit (memory) 12A and the table TB1 stored in the inverter output lower limit value storage unit 12A, the lower limit value of the inverter output according to the current set differential pressure ΔPsp (ΔPspnow) The inverter output lower limit value acquisition unit 12B that acquires INV _MIN (INV _MIN now), and the primary pump 2 that satisfies ΔPpvnow = ΔPspnow from the measured return / return differential pressure ΔPpv (ΔPpvnow) and the current set differential pressure ΔPspnow Inverter output calculation unit 12C for obtaining the inverter output INV (INV = 0 to 100%).

Further, the control device 12 sets the lower limit value INV _MIN now of the inverter output acquired by the inverter output lower limit value acquisition unit 12B as the lower limit set value INV _MIN sp of the inverter output at the current set differential pressure ΔPspnow, and this lower limit set value From the inverter output regulation unit 12D that regulates the inverter output INV from the inverter output calculation unit 12C to the primary pump 2 so as not to fall below INV _MIN sp, and the measured return pressure differential ΔPpvnow and the current set differential pressure ΔPspnow A valve opening degree output calculation unit 12E that calculates a valve opening degree output θ (θ = 0 to 100%) to the bypass valve 10 such that ΔPpvnow = ΔPspnow. The valve opening output calculation unit 12E normally outputs θ = 0 as the valve opening output θ, and the valve opening only when the inverter output restriction unit 12D restricts the inverter output INV to the primary pump 2. The output θ is calculated.

FIG. 3 illustrates a table TB1 showing a relationship between the above-described set differential pressure ΔPsp stored in the inverter output lower limit value storage unit 12A and the inverter output lower limit value INV _MIN . In this table TB1, the horizontal axis represents the set differential pressure ΔPsp, and the vertical axis represents the lower limit value INV _MIN of the inverter output. The relationship between the set differential pressure ΔPsp and the lower limit value INV _MIN of the inverter output is determined as a relationship obtained by changing the set differential pressure ΔPsp by at least two points as a theoretical value.

In this example, the lower limit value INV _MIN dw of the inverter output to the primary pump 2 that can secure the minimum flow rate Q _MIN to the heat source unit 1 with respect to the lower limit value ΔPspdw of the set differential pressure ΔPsp is obtained as a theoretical value, and the set differential pressure ΔPsp. The lower limit value INV _MIN up of the inverter output to the primary pump 2 that can ensure the minimum flow rate Q _MIN to the heat source unit 1 relative to the upper limit value ΔPspup of the current value is obtained as a theoretical value, and the lower limit of the set differential pressure ΔPsp obtained as this theoretical value The relationship between the lower limit value INV _MIN dw of the inverter output at the value ΔPspdw and the lower limit value INV _MIN up of the inverter output at the upper limit value ΔPspup of the set differential pressure ΔPsp is obtained from the relationship between the set differential pressure ΔPsp and the lower limit value INV _MIN of the inverter output The relationship between the obtained set differential pressure ΔPsp and the lower limit value INV _MIN of the inverter output is stored as a table TB1 in the inverter output lower limit value storage unit 12A before factory shipment. I am letting.

FIG. 4 shows how to obtain the lower limit values INV _MIN dw and INV _MIN up of the inverter output. In FIG. 4, a characteristic IV is a characteristic showing a relationship between a required pump pressure and a flow rate when the set differential pressure ΔPsp is an upper limit value ΔPspup, and a characteristic V is a pump required when the set differential pressure ΔPsp is a lower limit value ΔPspdw. This is a characteristic indicating the relationship between pressure and flow rate. The inverter output INV having the characteristic VI intersecting the point P1up at which the minimum flow rate Q _MIN is reached in the characteristic IV is a theoretical value of the lower limit value INV _MIN up of the inverter output with respect to the upper limit value ΔPspup of the set differential pressure ΔPsp. The inverter output INV having the characteristic VII that intersects the point P1dw that becomes Q _MIN is the theoretical value of the lower limit value INV _MIN dw of the inverter output with respect to the lower limit value ΔPspdw of the set differential pressure ΔPsp.

  Next, processing operations unique to the present embodiment in the control device 12 will be described with reference to the flowchart shown in FIG. In this example, it is assumed that the set differential pressure ΔPsp is manually changed during operation.

In the control device 12, the inverter output lower limit value acquisition unit 12B takes in the set differential pressure ΔPsp as the current set differential pressure ΔPspnow (step S101), and the lower limit value INV _{MIN of the} inverter output corresponding to the fetched current set differential pressure ΔPspnow. Now is obtained from the table TB1 in the inverter output lower limit storage unit 12A (step S102), and the obtained lower limit value INV _MIN now of the inverter output is obtained as the lower limit set value INV _MIN sp of the inverter output at the current set differential pressure ΔPspnow. To the inverter output restriction unit 12D (step S103).

  The inverter output calculation unit 12C captures the measured return differential pressure ΔPpv as ΔPpvnow (step S104), and generates an inverter output INV such that ΔPpvnow = ΔPspnow from the retrieved forward differential pressure ΔPpvnow and the current set differential pressure ΔPspnow. Obtained and sent to the inverter output restricting unit 12D (step S105).

The inverter output restriction unit 12D compares the inverter output INV from the inverter output calculation unit 12C with the lower limit set value INV _MIN sp of the inverter output from the inverter output lower limit value acquisition unit 12B (step S106).

Here, if INV ≧ INV _MIN sp (YES in step S106), the inverter output restriction unit 12D outputs the inverter output INV from the inverter output calculation unit 12C as it is as the inverter output INV to the primary pump 2 ( Step S110). At this time, the valve opening output calculation unit 12E sets the valve opening output θ to θ = 0 because the inverter output restriction unit 12D does not restrict the inverter output INV to the primary pump 2 (step S107). The valve opening output θ = 0 is output as the valve opening output θ to the bypass valve 10 (step S110).

On the other hand, if INV <INV _MIN sp (NO in step S106), the inverter output restriction unit 12D uses the inverter output INV from the inverter output calculation unit 12C as the lower limit of the inverter output from the inverter output lower limit value acquisition unit 12B. The set value INV _MIN sp is regulated (step S108), and the regulated inverter output INV (INV = INV _MIN sp) is output as the inverter output INV to the primary pump 2 (step S110). At this time, since the inverter output restriction unit 12D regulates the inverter output INV to the primary pump 2, the valve opening degree output calculation unit 12E calculates ΔPpvnow = ΔPspnow from the return differential pressure ΔPpvnow and the current set differential pressure ΔPspnow. The valve opening output θ is calculated as follows, and the calculated valve opening output θ is output as the valve opening output θ to the bypass valve 10 (step S110).

[When the set differential pressure ΔPsp is changed]
The control device 12 repeats the processing operations of steps S101 to S110 described above at regular intervals. Here, when the set differential pressure ΔPsp is changed, the inverter output lower limit value acquisition unit 12B takes in the changed set differential pressure ΔPsp as the current set differential pressure ΔPspnow (step S101), and takes in the current setting thus taken. The lower limit value INV _MIN now of the inverter output corresponding to the differential pressure ΔPspnow is obtained from the table TB1 in the inverter output lower limit value storage unit 12A (step S102), and the obtained lower limit value INV _MIN now of the inverter output is obtained as the current set differential pressure. The inverter output lower limit set value INV _MIN sp at ΔPspnow is sent to the inverter output restricting unit 12D (step S103).

Here, when the set differential pressure ΔPsp is changed in the increasing direction, the lower limit set value INV _MIN sp of the inverter output to the inverter output restricting unit 12D is increased according to the table TB1 shown in FIG. When the set differential pressure ΔPsp is changed in the downward direction, the lower limit set value INV _MIN sp of the inverter output to the inverter output restricting unit 12D is lowered according to the table TB1 shown in FIG.

The inverter output restriction unit 12D compares the inverter output INV from the inverter output calculation unit 12C and the lower limit set value INV _MIN sp of the changed inverter output from the inverter output lower limit value acquisition unit 12B, and INV ≧ INV _MIN sp If there is (YES in step S106), the inverter output INV from the inverter output calculation unit 12C is output as it is as the inverter output INV to the primary pump 2 (step S110), and if INV <INV _MIN sp (in step S106) NO), the inverter output INV (INV = INV _MIN sp) regulated by the lower limit set value INV _MIN sp of the inverter output from the inverter output lower limit acquisition unit 12B is output as the inverter output INV to the primary pump 2 (step S110). ).

In this case, the lower limit set value INV _MIN sp of the changed inverter output is the inverter output that can secure the minimum flow rate Q _MIN to the heat source unit 1 at the current set differential pressure ΔPspnow (changed set differential pressure ΔPsp). Since it is the lower limit value INV _MIN , the flow rate of the heat source water passing through the heat source unit 1 is kept at the minimum flow rate Q _MIN while the inverter output INV is regulated at the lower limit set value INV _MIN sp.

That is, in the conventional system, when the set differential pressure ΔPsp is increased, the lower limit set value INV _MIN of the inverter output is set to a fixed value, so that the flow rate to the heat source unit 1 is increased as described with reference to FIG. There is a possibility that the fail-safe function of the heat source unit 1 may work because it becomes smaller than the minimum flow rate Q _MIN . On the other hand, in the present embodiment, when the set differential pressure ΔPsp is increased, the lower limit set value INV _MIN of the inverter output is increased (the state point in the direction from the P1 point to the P1up point shown in FIG. 4). Movement), the minimum flow rate Q _MIN to the heat source unit 1 is ensured. Thereby, there is no possibility that the fail safe function of the heat source device 1 works, and it is possible to change the set differential pressure ΔPsp in the increasing direction without any trouble.

Further, in the conventional system, when the set differential pressure ΔPsp is lowered, the lower limit set value INV _MIN of the inverter output is a fixed value, so that the flow rate to the heat source unit 1 is as described with reference to FIG. It becomes larger than the minimum flow rate Q _MIN , the bypass flow rate QB increases, and the energy increases. In contrast, in this embodiment, when the set differential pressure ΔPsp is lowered, the lower limit set value INV _MIN of the inverter output is lowered (the state point in the direction from the P1 point to the P1dw point shown in FIG. 4). Movement), the minimum flow rate Q _MIN to the heat source unit 1 is ensured. As a result, the bypass flow rate QB does not increase and the energy does not increase, and the set differential pressure ΔPsp can be changed in the descending direction without hindrance.

In the above-described embodiment, the relationship between the set differential pressure ΔPsp and the lower limit value INV _MIN of the inverter output is obtained as a theoretical value, but it may be obtained as an actual value instead of a theoretical value. In this case, for example, the relationship between the set differential pressure ΔPsp and the lower limit value INV _MIN of the inverter output is obtained as an actual value by the following method.

In the system shown in FIG. 1, before starting operation, the minimum flow rate Q _MIN is supplied to the heat source unit 1, and the return differential pressure ΔPpv at that time is set to the lower limit value ΔPspdw of the set differential pressure ΔPsp. A constant pressure control is performed. The inverter output INV to the primary pump 2 at this time is observed, and the observed inverter output INV is obtained as the actual value of the lower limit value INV _MIN dw of the inverter output at the set differential pressure ΔPspdw (see data D1 shown in FIG. 6). ).

Next, the minimum flow rate Q _MIN is supplied to the heat source unit 1, and the constant pressure control by the primary pump rotation speed is performed so that the return differential pressure ΔPpv at that time becomes the upper limit value ΔPspup of the set differential pressure ΔPsp. The inverter output INV to the primary pump 2 at this time is observed, and the observed inverter output INV is obtained as an actual value of the lower limit value INV _MIN up of the inverter output at the set differential pressure ΔPspup (see data D2 shown in FIG. 6). ).

Then, from the lower limit value INV _MIN dw of the inverter output at the set differential pressure ΔPspdw obtained as the actual value and the INV _MIN up of the inverter output at the set differential pressure ΔPspup, the set differential pressure ΔPsp and the lower limit value INV _{MIN of the} inverter output (See FIG. 7), and this calculated relationship is stored in the inverter output lower limit storage unit 12A as a table TB1.

  In the above-described embodiment, the setting differential pressure ΔPsp is manually changed during operation. However, the setting differential pressure ΔPsp may be automatically changed. For example, as shown in FIG. 8, a flow meter 13 is provided to measure the load flow rate QF returned to the return header 8, and the load flow rate QF measured by the flow meter 13 is given to the control device 12. Is changed according to the load flow rate QF. In this case, if the load flow rate QF decreases, the set differential pressure ΔPsp is decreased, and if the load flow rate QF increases, the set differential pressure ΔPsp is increased.

  FIG. 9 shows a flowchart corresponding to FIG. 5 when the set differential pressure ΔPsp is changed in accordance with the load flow rate QF. In this flowchart, in step S200, the measured load flow rate QF is captured, and in step S201, the set differential pressure ΔPsp corresponding to the captured load flow rate QF is set as the current set differential pressure ΔPspnow. And the process of step S202-S210 corresponding to step S102-S110 is performed. Thus, when the load flow rate QF is small, that is, when the valve 6-1 in the external load 6 is throttled (when the terminal differential pressure is high), the rotational speed of the primary pump 2 is reduced. It is possible to save energy by lowering. Such control is called water supply pressure variable control by load flow rate.

  As an example of automatically changing the set differential pressure ΔPsp, the differential pressure on the inlet side and the outlet side of the external load 6 is actually measured as a terminal differential pressure, and the set differential pressure ΔPsp is determined according to the measured terminal differential pressure. It is also possible to change. In this case, when the measured value of the terminal differential pressure increases, the set differential pressure ΔPsp is decreased, and when the measured value of the terminal differential pressure decreases, the set differential pressure ΔPsp is increased. Further, for example, when there are a plurality of external loads 6, the opening degree of the valve 6-1 in these external loads 6 is monitored, and the opening degree of the valve 6-1 is 100%. If so, it is conceivable to increase the set differential pressure ΔPsp.

In the above-described embodiment, the inverter output lower limit value INV _MIN now corresponding to the current set differential pressure ΔPspnow is obtained from the table TB1 stored in the inverter output lower limit value storage unit 12A. The lower limit value INV _MIN now of the inverter output corresponding to the return differential pressure ΔPpvnow may be acquired.

  Further, in the above-described embodiment, the differential pressure between the heat source water between the forward header 4 and the return header 8, that is, the difference between the supply pressure of the heat source water to the external load 6 and the return water pressure is measured as the forward differential pressure ΔPpv. The primary pump heat source variable flow rate control system in which the return differential pressure ΔPpv is made to coincide with the set differential pressure ΔPsp has been described, but the water supply pressure of the heat source water to the external load 6 is measured, and this water supply pressure is A similar method can also be adopted in a primary pump heat source variable flow rate control system that matches the set water supply pressure.

  In this case, as shown in FIG. 10, the water supply pressure PSpv of the heat source water to the external load 6 is measured by the pressure gauge 14, and the measured water supply pressure PSpv is sent to the control device 12. In the control device 12, the water supply pressure Pspv from the pressure gauge 14 is compared with the set water supply pressure PSsp, and the inverter output INV to the primary pump 2 and the valve opening output to the bypass valve 10 are set so that Pspv = PSsp. Adjust θ.

At this time, the control device 12 takes in the set water pressure PSsp as the current set water pressure PSspnow (FIG. 11: Step S301), and sets the lower limit value INV _MIN now of the inverter output corresponding to the fetched current set water pressure PSspnow. Obtain from the table showing the relationship between the water supply pressure PSsp and the lower limit value INV _MIN of the inverter output (step S302), and the obtained lower limit value INV _MIN now of the inverter output is set as the lower limit of the inverter output at the current set water supply pressure PSspnow. The value is INV _MIN sp (step S303). Thereafter, the processes of steps S304 to S310 are executed in the same manner as steps S104 to S110 in the flowchart shown in FIG.

In the system for controlling the water supply pressure to be constant, the set water supply pressure Psp may be manually changed or automatically changed as in the system for controlling the return differential pressure to be constant. May be. FIG. 12 shows a flowchart corresponding to FIG. 9 when the set water supply pressure Psp is changed in accordance with the load flow rate QF. Further, the relationship between the set water supply pressure PS and the lower limit value INV _MIN of the inverter output may be a relationship obtained by changing the set water supply PSsp by at least two points as a theoretical value, or a relationship obtained as an actual value. There may be. Further, the lower limit value INV _MIN now of the inverter output corresponding to the current water supply pressure PSpvnow may be acquired from a table indicating the relationship between the set water supply pressure PSsp and the lower limit value INV _MIN of the inverter output.

In the above-described embodiment, the relationship between the set differential pressure ΔPsp and the lower limit value INV _MIN of the inverter output and the relationship between the set water pressure PS and the lower limit value INV _MIN of the inverter output are not necessarily stored as a table. For example, it may be stored as an equation.

  In the above-described embodiment, the system having the forward header 4 and the return header 8 has been described as an example. However, the system can be similarly applied to a system that does not have the forward header 4 and the return header 8.

  The primary pump type heat source variable flow rate control system and method of the present invention can be used in various fields such as heat loads such as air conditioners and fan coils, and air conditioning systems that use district cooling and heating customers as external loads. It is.

  DESCRIPTION OF SYMBOLS 1 ... Heat source machine, 2 ... Primary pump, 3 ... Inverter, 4 ... Out header, 5 ... Outbound pipe line, 6 ... External load, 6-1 ... Valve, 7 ... Return water line, 8 ... Return header, 9 ... Bypass pipe, 10 ... Bypass valve, 11 ... Differential pressure gauge, 12 ... Control device, 12A ... Inverter output lower limit value storage unit, 12B ... Inverter output lower limit value acquisition unit, 12C ... Inverter output calculation unit, 12D ... Inverter output regulation unit , 12E ... valve opening output calculation unit, TB1 ... table.

Claims (10)

A heat source machine for generating heat source water;
A primary pump for conveying heat source water generated by the heat source unit;
An external load that receives supply of heat source water from the heat source unit;
A water source water outlet line from the heat source unit to the external load;
A return pipe to the heat source water of the heat source water from the external load;
A bypass line for communicating the outgoing water line and the return water line;
A bypass valve provided in the bypass line;
The difference between the supply water pressure and the return water pressure of the heat source water to the external load is defined as a forward / return differential pressure, and an inverter output for controlling the rotational speed to the primary pump so that the forward / backward differential pressure matches the set differential pressure. And a primary pump type heat source variable flow rate control system comprising a control means for adjusting a valve opening output for opening control to the bypass valve,
The control means includes
Inverter output that stores the relationship between the set differential pressure when the set differential pressure is changed and the lower limit value of the inverter output to the primary pump that can ensure the minimum flow rate determined for the heat source unit A lower limit storage means;
Inverter output lower limit value acquisition means for acquiring the lower limit value of the inverter output corresponding to the current set differential pressure from the relationship between the set differential pressure stored in the inverter output lower limit value storage means and the lower limit value of the inverter output;
The lower limit value of the inverter output acquired by the inverter output lower limit value acquisition means is set as the lower limit set value of the inverter output at the current set differential pressure, and the inverter output to the primary pump is set so as not to fall below the lower limit set value. A primary pump type heat source variable flow rate control system comprising: an inverter output regulating means for regulating. In the primary pump type heat source variable flow rate control system according to claim 1,
The inverter output lower limit storage means is
The primary pump type heat source variable flow rate control system is characterized by storing a relationship between the set differential pressure obtained as a theoretical value by changing the set differential pressure at least two points and a lower limit value of the inverter output. In the primary pump type heat source variable flow rate control system according to claim 1,
The inverter output lower limit storage means is
The primary pump type heat source variable flow rate control system is characterized in that the relationship between the set differential pressure obtained as an actual value by changing the set differential pressure at least two points and the lower limit value of the inverter output is stored. In the primary pump type heat source variable flow rate control system described in any one of claims 1-3,
The inverter output lower limit storage means is
Based on the relationship between the set differential pressure stored in the inverter output lower limit value storage means and the lower limit value of the inverter output, the lower limit value of the inverter output corresponding to the current return differential pressure is obtained instead of the current set differential pressure A primary pump type heat source variable flow rate control system characterized by: In the primary pump type heat source variable flow rate control system described in any one of claims 1-4,
The control means includes
Use the water supply pressure of the heat source water to the external load instead of the return differential pressure,
A primary pump type heat source variable flow rate control system using a set water supply pressure instead of the set differential pressure. A heat source device that generates heat source water, a primary pump that conveys the heat source water generated by the heat source device, an external load that receives supply of heat source water from the heat source device, and an external load from the heat source device to the external load Provided in the bypass pipe, a water supply water outlet pipe, a return water pipe from the external load to the heat source water to the heat source machine, a bypass pipe that connects the outgoing water pipe and the return water pipe A bypass valve, and the difference between the water supply pressure and the return water pressure of the heat source water to the external load is a return differential pressure, and the return differential pressure and the set differential pressure are matched with each other to the primary pump. In a primary pump heat source variable flow rate control method for adjusting an inverter output for rotational speed control and a valve opening degree output for opening degree control to the bypass valve,
The relationship between the set differential pressure when the set differential pressure is changed and the lower limit value of the inverter output to the primary pump that can secure the minimum flow rate determined for the heat source unit is stored in the memory. Steps,
Obtaining a lower limit value of the inverter output corresponding to the current set differential pressure from the relationship between the set differential pressure stored in the memory and the lower limit value of the inverter output;
The obtained lower limit value of the inverter output is set as the lower limit set value of the inverter output at the current set differential pressure, and the inverter output to the primary pump is regulated so as not to fall below the lower limit set value. A primary pump type heat source variable flow rate control method characterized by the above. In the primary pump type heat source variable flow rate control method described in claim 6,
The relationship between the set differential pressure stored in the memory and the lower limit value of the inverter output is a relationship obtained by changing the set differential pressure by at least two points as a theoretical value. Control method. In the primary pump type heat source variable flow rate control method described in claim 6,
The relationship between the set differential pressure stored in the memory and the lower limit value of the inverter output is a relationship obtained by changing the set differential pressure by at least two points as an actual value. Control method. In the primary pump type heat source variable flow rate control method described in any one of claims 6-8,
The step of obtaining the lower limit value of the inverter output includes:
Based on the relationship between the set differential pressure stored in the inverter output lower limit value storage means and the lower limit value of the inverter output, the lower limit value of the inverter output corresponding to the current return differential pressure is obtained instead of the current set differential pressure A primary pump type heat source variable flow rate control method characterized by: In the primary pump type heat source variable flow rate control method described in any one of claims 6-9,
Use the water supply pressure of the heat source water to the external load instead of the return differential pressure,
A primary pump type heat source variable flow rate control method using a set water supply pressure instead of the set differential pressure.

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