JP2011112277A - System and method for controlling water supply pressure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform change control of a set differential pressure and a set water supply pressure without causing problems even in a system having both an inverter pump and a constant-speed pump. <P>SOLUTION: A lower limit set value change function of inverter output is provided in a control device 14. In accordance with an expression of INV<SB>MIN</SB>=(ΔPpv/P<SB>SHUT</SB>)<SP>1/2</SP>+α, wherein shutoff pressure during operation at rated rotational frequency of a secondary pump 9 is represented as P<SB>SHUT</SB>, current pump before/after differential pressure as ΔPpv and an allowance as α, the control part 14 calculates a lower limit value INV<SB>MIN</SB>of inverter output to the inverter pump 9-1. The calculated lower limit value INV<SB>MIN</SB>of the inverter output is used as a lower limit set value INV<SB>MIN</SB>sp of current inverter output. Inverter output INV to the inverter pump 9-1 is regulated not to become below the lower limit set value INV<SB>MIN</SB>sp. Similarly, also when the set water supply pressure is used, in accordance with the predetermined expression, the lower limit set value INV<SB>MIN</SB>sp of current inverter output is calculated. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a water supply pressure control system and method for controlling the water supply pressure of heat source water to an external load.

  FIG. 11 shows an instrumentation diagram of a conventional water supply pressure control system. This water supply pressure control system is a type that does not perform change control of the water supply pressure, and for example, a technique similar to Patent Document 1 is shown.

  In FIG. 11, 1 is a heat source unit that generates heat source water, 2 is a primary pump that conveys heat source water generated by the heat source unit 1, and 3 is an external load (a heat load such as an air conditioner or a fan coil, a demand for district cooling and heating) 4-1 and 4-2 are the first and second forward headers provided in the heat source water supply path from the heat source unit 1 to the external load 3, and 5 is the forward headers 4-1 and 4- 2 is a return water pipe for the heat source water to the external load 3 via 2, 6 is a return water pipe for the heat source water from the external load 3, 7 is a return header to which the heat source water sent via the return water pipe 6 is returned, 8 is a bypass line for communicating the forward header 4-1 and the return header 8, and 12 is a pressure difference between the heat source water between the first forward header 4-1 and the second forward header 4-2 before and after the pump. A differential pressure sensor 13 for measuring the differential pressure ΔPpv is a flow rate of heat source water returned from the external load 3 as a load flow rate QF. Flowmeter for measuring Te, 14 denotes a control unit. The external load 3 is provided with a valve 3-1 for adjusting the flow rate of the supplied heat source water.

  In this water supply pressure control system, between the first forward header 4-1 and the second forward header 4-2, the first secondary pump 9-1 and the second secondary pump 9 as the secondary pump 9 are provided. The pump 9-2 is connected in parallel. Further, a bypass valve 10 is provided between the first forward header 4-1 and the second forward header 4-2 in a bypass passage L1 that communicates between the forward headers 4-1 and 4-2. It has been.

  The first secondary pump 9-1 and the second secondary pump 9-2 have the same rated rotational speed, and an inverter 11 for adjusting the rotational speed is attached only to the first secondary pump 9-1. Yes. That is, the first secondary pump 9-1 is a pump whose rotation speed can be adjusted, and the second secondary pump 9-2 is a pump operated at a rated rotation speed. Hereinafter, the first secondary pump 9-1 is called an inverter pump, and the second secondary pump 9-2 is called a constant speed pump.

  In this water supply pressure control system, the heat source water pumped by the primary pump 2 is cooled or heated by the heat source unit 1 and reaches the forward header 4-1, and is sent by the secondary pump 9 (9-1, 9-2). It is pumped to the forward header 4-2 and supplied to the external load 3 through the forward water pipeline 5. Then, heat is exchanged in the external load 3, returned to the return header 7 through the return water pipe 6, 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.

(Operation number control)
The control device 14 switches on / off the constant speed pump 9-2 according to the load flow rate QF measured by the flow meter 13. In this example, the constant speed pump 9-2 is turned off until the load flow rate QF exceeds the predetermined value Qth, and only the inverter pump 9-1 is operated independently. When the load flow rate QF exceeds a predetermined value Qth, the constant speed pump 9-2 is turned on, and the inverter pump 9-1 and the constant speed pump 9-2 are operated in parallel.

(Constant pressure control)
The control device 14 monitors the pump front-rear differential pressure ΔPpv measured by the differential pressure gauge 12, and controls the rotation speed of the inverter pump 9-1 and the opening degree of the bypass valve 10 so that the pump front-rear differential pressure ΔPpv is constant. To do. That is, the pump front-rear differential pressure ΔPpv measured by the differential pressure gauge 12 is compared with a preset differential pressure ΔPsp, and an inverter for controlling the rotational speed to the inverter pump 9-1 is set so that ΔPpv = ΔPsp. The output INV (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 inverter pump 9-1. This lower limit set value INV _MIN is determined for the following reason. For example, at the time of parallel operation of the inverter pump 9-1 and the constant speed pump 9-2, if the rotational speed of the inverter pump 9-1 is decreased too much, the constant speed pump 9-2 is operated at the rated rotational speed. The pump pressure of the inverter pump 9-1 becomes smaller than the pump pressure of the constant speed pump 9-2, and the heat source water does not flow out of the inverter pump 9-1. . The lower limit set value INV _MIN for the inverter output INV to the inverter pump 9-1 is set higher so that such a heating risk does not occur.

[Constant pressure control by inverter pump speed: INV ≧ INV _MIN ]
When the pump front-rear differential pressure ΔPpv increases, the control device 14 decreases the inverter output INV to the inverter pump 9-1 (decreases the rotational speed of the inverter pump 9-1) so that ΔPpv = ΔPsp.

Here, when the inverter output INV obtained internally is equal to or higher than the lower limit set value INV _MIN , the control device 14 sends the 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 based on the inverter pump rotation speed (see region S1 shown in FIG. 12).

[Constant pressure control by opening of bypass valve: INV <INV _MIN ]
When the internally obtained inverter output INV is smaller than the lower limit set value INV _MIN , the control device 14 regulates the inverter output INV to the inverter pump 9-1 so as not to fall below the lower limit set value INV _MIN . That is, the inverter output INV to the inverter pump 9-1 is set to INV _MIN . In this case, the control device 14 controls the opening degree of the bypass valve 10 so that ΔPpv = ΔPsp. This is called constant pressure control based on the opening degree of the bypass valve (see region S2 shown in FIG. 12).

In the constant pressure control based on the opening degree of the bypass valve, the inverter output INV to the inverter pump 9-1 is restricted to the lower limit set value INV _MIN .

JP-A-61-180315 JP-A-8-261190

However, in the above-described water supply pressure control system, the lower limit set value INV _MIN of the inverter output is set as a fixed value on the premise that the change control of the water supply pressure is not performed, and when the set differential pressure ΔPsp is increased, the lower limit set value When the rotational speed is regulated by INV _MIN , the pressure of the inverter pump becomes lower than the applied pressure, and when the pressure is lost or the set differential pressure ΔPsp is lowered, the rotational speed is regulated by the lower limit set value INV _MIN . Since the pressure of the inverter pump at that time becomes higher than the applied pressure, the bypass flow rate increases and the energy increases, and it is difficult to perform change control of the set differential pressure ΔPsp.

  For this reason, when changing control of the set differential pressure ΔPsp is performed, all the secondary pumps are inverter pumps, and by controlling the rotation speed of these inverter pumps, the pump differential pressure ΔPpv matches the set differential pressure ΔPsp. (For example, refer to Patent Document 2). However, in such a system, it is necessary to install inverters in all the secondary pumps, increasing the initial cost and deteriorating the return on investment.

  In the above description, the water supply pressure is such that the differential pressure of the heat source water between the first forward header and the second forward header is the differential pressure before and after the pump, and the differential pressure before and after the pump matches the set differential pressure. Although the control system has been described, the same problem arises in the water supply pressure control system in which the water supply pressure from the second forward header matches the set water supply pressure.

  The present invention has been made to solve such a problem, and the object of the present invention is a system in which an inverter pump and a constant speed pump are mixed without using all the secondary pumps as inverter pumps. However, an object of the present invention is to provide a water supply pressure control system and method capable of performing change control of the set differential pressure and the set water supply pressure without any trouble.

  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 supply of heat source water from the heat source device to an external load. The first and second forward headers provided on the road, the pump capable of adjusting the rotational speed as the first secondary pump (inverter pump), and the pump operated at the rated rotational speed as the second secondary pump ( Constant speed pump), the first secondary pump and the second secondary pump are mixed and the rated rotational speed connected in parallel between the first forward header and the second forward header is the same. A plurality of secondary pumps, a bypass valve provided in a bypass passage for communicating the first forward header and the second forward header, and heat source water between the first forward header and the second forward header The differential pressure of the pump is the differential pressure before and after the pump so that the differential pressure before and after the pump matches the set differential pressure. In a water supply pressure control system comprising: an inverter output for controlling the rotational speed to the first secondary pump; and a control means for adjusting the valve opening output for controlling the opening to the bypass valve. The lift at zero flow rate when the pump is rotated at the rated speed is the cutoff pressure at the rating, and the inverter output to the first secondary pump is calculated from the cutoff pressure at the rating and the current differential pressure across the pump. The inverter output lower limit value calculating means for calculating the lower limit value, and the lower limit value of the inverter output calculated by the inverter output lower limit value calculating means is set as the current lower limit set value of the inverter output. Inverter output restricting means for restricting the inverter output to the secondary pump 1 is provided.

In this invention, the lower limit value of the inverter output to the inverter pump is calculated from the cutoff pressure at the time of rating (the lift at zero flow rate when the secondary pump is rotated at the rated speed) and the current differential pressure across the pump. Is done. For example, if the shutoff pressure at the time of rating is P _SHUT , the current differential pressure before and after the pump is ΔPpv, and the margin is α, the lower limit value INV _MIN of the inverter output is INV _MIN = (ΔPpv / P _SHUT ) ^{1 /} It may be calculated as ² + α. In the present invention, when the rated speed of the secondary pump is operated with a commercial power source, there are a rated speed at 50 Hz and a rated speed at 60 Hz, which vary depending on the type of power source. It is.

  In the present invention, the lower limit value of the inverter output calculated in this way is set as the lower limit set value of the current inverter output, and the inverter output to the inverter pump is restricted so as not to fall below the lower limit set value. For example, if the set differential pressure is increased and the pump front-rear differential pressure increases accordingly, the lower limit value of the inverter output corresponding to the increased pump front-rear differential pressure is calculated, and the calculated lower limit of the inverter output is calculated. The value is set as the lower limit set value of the inverter output, and the inverter output to the inverter pump is restricted so as not to fall below the lower limit set value. Further, if the set differential pressure is lowered and the pump front-rear differential pressure decreases following this, the lower limit value of the inverter output corresponding to the lowered pump front-rear differential pressure is calculated, and the calculated lower limit of the inverter output is calculated. The value is set as the lower limit set value of the inverter output, and the inverter output to the inverter pump is restricted so as not to fall below the lower limit set value.

  Thus, in the present invention, when the set differential pressure is changed, the lower limit set value of the inverter output is automatically changed according to the pump front-rear differential pressure that changes following the change of the set differential pressure. The Even if the set differential pressure is changed by automatically changing the lower limit set value of the inverter output, the set differential pressure can be controlled without any trouble without causing pressure loss or increasing energy. Is possible.

  In the present invention, the set differential pressure may be changed manually or automatically. For example, the flow rate of the heat source water returned from the external load is measured as the load flow rate, and the set differential pressure is determined based on the measured load flow rate. In this case, the set differential pressure is automatically changed according to the load flow rate.

As a modification of the present invention, the lower limit value of the inverter output to the inverter pump is calculated not from the rated closing pressure and the current differential pressure across the pump but from the rated cutoff pressure and the current set differential pressure. You may make it do. For example, as an example, assuming that the cutoff pressure at the time of rating is P _SHUT , the current set differential pressure is ΔPsp, and the margin is α, the lower limit value INV _MIN of the inverter output is INV _MIN = (ΔPsp / P _SHUT ) ^1/2 It is conceivable to calculate as + α.

  As a modification of the present invention, the water supply pressure of the heat source water from the second forward header may be used instead of the pump front-rear differential pressure, and the set water supply pressure may be used instead of the set differential pressure. In this case, the control means is for controlling the output of the inverter for controlling the rotational speed to the inverter pump and controlling the opening to the bypass valve so that the water supply pressure of the heat source water from the second forward header matches the set water supply pressure. Adjust the valve opening output. The lift at zero flow rate when the secondary pump is rotated at the rated speed is the rated cutoff pressure, and the inverter is calculated from the rated cutoff pressure and the current water supply pressure (or the current set water supply pressure). Calculate the lower limit of output.

  According to the present invention, the lift at zero flow rate when the secondary pump is rotated at the rated rotational speed is set as the cutoff pressure at the rating, and the cutoff pressure at the rating and the current differential pressure before and after the pump (or the current setting). The lower limit value of the inverter output to the inverter pump is calculated from the differential pressure), and the calculated lower limit value of the inverter output is set as the current lower limit set value of the inverter output. Inverter output is regulated so that even if the set differential pressure is changed, pressure loss will not occur and energy will not increase, even in systems where inverter pumps and constant speed pumps coexist. Therefore, it is possible to carry out the change control of the set differential pressure.

  Further, according to the present invention, by using the water supply pressure of the heat source water from the second forward header instead of the pump front-rear differential pressure, and using the set water supply pressure instead of the set differential pressure, the pump front-back differential pressure In the same way as when using the set differential pressure, even if the set water supply pressure is changed, a system in which an inverter pump and a constant speed pump are mixed without causing pressure loss or increasing energy. However, it becomes possible to carry out the change control of the set water supply pressure without any trouble.

1 is an instrumentation diagram of a water supply pressure control system (a water supply pressure control system in which a pump differential pressure and a set differential pressure are made to coincide with each other) showing an embodiment of the present invention. It is a functional block diagram of the principal part of the control apparatus in this water supply pressure control system. It is a flowchart which shows the processing operation at the time of the constant pressure control in this control apparatus. It is a flowchart which shows the processing operation at the time of operation number control in this control apparatus. It is a functional block diagram of the principal part of a control device at the time of determining a setting differential pressure according to load flow. It is a flowchart which shows the processing operation at the time of pressure constant control in this control apparatus. It is a figure which shows the relationship (QH characteristic) of the flow volume at the time of the independent operation of only an inverter pump, and the parallel operation of an inverter pump and a constant speed pump. It is an instrumentation figure of the water supply pressure control system (water supply pressure control system which made the water supply pressure and the set water supply pressure correspond) which shows other embodiments of the present invention. It is a flowchart which shows the processing operation at the time of the constant pressure control in the control apparatus of this water supply pressure control system. It is a flowchart which shows the processing operation at the time of pressure fixed control at the time of determining a setting water supply pressure according to the load flow rate in the control apparatus of this water supply pressure control system. It is an instrumentation figure of the conventional water supply pressure control system. It is a figure explaining the pressure constant control (the pressure constant control by an inverter pump rotation speed, and the pressure constant control by a bypass valve opening degree) in this water supply pressure control system.

  Hereinafter, the present invention will be described in detail based on embodiments. FIG. 1 is an instrumentation diagram of a water supply pressure control system showing an embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 11 denote the same or equivalent components as those described with reference to FIG.

  In this embodiment, a point different from the conventional water supply pressure control system is a function of the control device 14. The control device 14 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 the present embodiment, the 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 14 including the function of changing the lower limit set value of the inverter output.

The control device 14 stores the _lifting pressure at the rated flow when the secondary pump 9 (9-1, 9-2) is rotated at the rated rotation speed, and the lift at zero flow rate is stored as the rated closing pressure P _SHUT. Section (memory) 14A, the rated cutoff pressure P _SHUT stored in the rated cutoff pressure storage section 14A and the current pump front-rear differential pressure ΔPpv (ΔPpvnow), the inverter output to the inverter pump 9-1 From the inverter output lower limit value calculation unit 14B for calculating the lower limit value INV _MIN (INV _MIN now), the current pump differential pressure ΔPpv (ΔPpvnow) and the current set differential pressure ΔPsp (ΔPspnow), ΔPpvnow = ΔPspnow And an inverter output calculation unit 14C for obtaining an inverter output INV (INV = 0 to 100%) to the inverter pump 9-1.

Further, the control device 14 sets the lower limit value INV _MIN now of the inverter output calculated by the inverter output lower limit value calculation unit 14B as the lower limit set value INV _MIN sp of the current inverter output, and does not fall below the lower limit set value INV _MIN sp. As described above, ΔPpvnow = ΔPspnow from the inverter output regulating unit 14D that regulates the inverter output INV from the inverter output calculating unit 14C to the inverter pump 9-1 and the current pump differential pressure ΔPpvnow and the current set differential pressure ΔPspnow. Based on the valve opening degree output calculation unit 14E for calculating the valve opening degree output θ (θ = 0 to 100%) to the bypass valve 10 and the load flow rate QF measured by the flow meter 13, the constant speed pump 9− And an operating number switching unit 14 </ b> F that switches 2 on / off. The valve opening output calculation unit 14E normally outputs θ = 0 as the valve opening output θ, and opens the valve only when the inverter output restriction unit 14D restricts the inverter output INV to the inverter pump 9-1. The degree output θ is calculated.

The following equation (1) is used to calculate the lower limit value INV _MIN (%) of the inverter output in the inverter output lower limit value calculation unit 14B. In the equation (1), α is a margin and is predetermined as a predetermined value.
INV _MIN = (ΔPpv / P _SHUT ) ^1/2 + α (1)

Paying attention to the above equation (1), P _SHUT (the cutoff pressure at the time of rating): ΔPsp (set differential pressure) = 1: (INV _MIN / 100) ² , and ΔPsp = P _SHUT × (INV _MIN / 100) ² , (INV _MIN / 100) ² = (ΔPsp / P _SHUT ), INV _MIN = (ΔPsp / P _SHUT ) ^1/2 , replace ΔPsp with ΔPpv, and INV _MIN = (ΔPpv / P _SHUT ) ^1/2, and a margin α is added to this to derive INV _MIN = (ΔPpv / P _SHUT ) ^1/2 + α. Note that by replacing ΔPsp with ΔPpv, that is, by using ΔPpv that changes following ΔPsp, INV _MIN suitable for the actual situation can be obtained.

  Next, processing operations unique to the present embodiment in the control device 14 will be described with reference to the flowcharts shown in FIGS. 3 and 4. In this example, it is assumed that the set differential pressure ΔPsp is manually changed during operation.

In the control device 14, the inverter output lower limit value calculation unit 14 </ b> B takes in the pump front-rear differential pressure ΔPpv measured by the differential pressure sensor 12 as the current pump front-rear differential pressure ΔPpvnow (FIG. 3: step S <b> 102). The inverter output lower limit value INV _MIN now is calculated using the above equation (1) from the pressure ΔPpvnow and the rated cutoff pressure P _SHUT stored in the rated cutoff pressure storage unit 14A (step S103). The calculated lower limit value INV _MIN now of the inverter output is sent to the inverter output restricting unit 14D as the current lower limit set value INV _MIN sp of the inverter output (step S104).

  The inverter output calculation unit 14C takes in the set differential pressure ΔPsp as the current set differential pressure ΔPspnow (step S101), and ΔPpvnow = ΔPspnow from the fetched current set differential pressure ΔPspnow and the current pump differential pressure ΔPpvnow. Inverter output INV is obtained (step S105) and sent to inverter output restricting unit 14D.

The inverter output restriction unit 14D compares the inverter output INV from the inverter output calculation unit 14C with the lower limit set value INV _MIN sp of the inverter output from the inverter output lower limit calculation unit 14B (step S106).

Here, if INV ≧ INV _MIN sp (YES in step S106), the inverter output restricting unit 14D outputs the inverter output INV from the inverter output calculating unit 14C as it is as the inverter output INV to the inverter pump 9-1. (Step S110). At this time, the valve opening output calculation unit 14E sets the valve opening output θ to θ = 0 because the inverter output restriction unit 14D does not restrict the inverter output INV to the inverter pump 9-1 (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 14D uses the inverter output INV from the inverter output calculation unit 14C as the lower limit of the inverter output from the inverter output lower limit value calculation unit 14B. 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 inverter pump 9-1 (step S110). At this time, since the inverter output restricting unit 14D restricts the inverter output INV to the inverter pump 9-1, the valve opening degree output calculating unit 14E determines the current set differential pressure ΔPspnow and the current pump differential pressure ΔPpvnow. Then, the valve opening output θ that satisfies ΔPpvnow = ΔPspnow is calculated, and the calculated valve opening output θ is output as the valve opening output θ to the bypass valve 10 (step S110).

  On the other hand, the operating unit switching unit 14F monitors the load flow rate QF measured by the flow meter 13 (FIG. 4: step S201), and until the load flow rate QF exceeds a predetermined value Qth (NO in step S202), the constant flow rate QF is monitored. The high speed pump 9-2 is turned off (step S203), and when the load flow rate QF exceeds a predetermined value Qth (YES in step S202), the constant speed pump 9-2 is turned on (step S204). Thus, the inverter pump 9-1 alone is operated until the load flow rate QF exceeds the predetermined value Qth, and when the load flow rate QF exceeds the predetermined value Qth, the inverter pump 9-1 and the constant speed pump 9-2 are operated. And parallel operation.

[When the set differential pressure ΔPsp is changed]
The control device 14 repeats the processing operations in steps S101 to S110 and the processing operations in steps S201 to S204 described above at regular intervals. Here, when the set differential pressure ΔPsp is changed and the pump front-rear differential pressure ΔPpv changes following this, the inverter output lower limit value calculation unit 14B uses the changed pump front-rear differential pressure ΔPpv as the current pump front-rear differential pressure ΔPpvnow. (Step S102), and using the above equation (1), the lower limit of the inverter output is calculated from the fetched pump front-rear differential pressure ΔPpvnow and the rated cutoff pressure P _SHUT stored in the rated cutoff pressure storage unit 14A. The value INV _MIN now is calculated (step S103), and the calculated lower limit value INV _MIN now of the inverter output is sent to the inverter output restricting unit 14D as the lower limit set value INV _MIN sp of the current inverter output (step S104).

Here, when the set differential pressure ΔPsp is changed in the increasing direction and the pump front-rear differential pressure ΔPpvnow increases following this, the lower limit set value INV of the inverter output to the inverter output restricting portion 14D is calculated by the calculation according to the equation (1). _MIN sp increases. When the set differential pressure ΔPsp is changed in the descending direction and the pump front-rear differential pressure ΔPpvnow decreases following this, the lower limit set value INV _MIN sp of the inverter output to the inverter output restricting unit 14D is calculated by the calculation according to the equation (1). Get smaller.

The inverter output restriction unit 14D compares the inverter output INV from the inverter output calculation unit 14C with the changed lower limit value INV _MIN sp of the inverter output from the inverter output lower limit calculation unit 14B, and INV ≧ INV _MIN sp If present (YES in step S106), the inverter output INV from the inverter output calculation unit 14C is output as it is as the inverter output INV to the inverter pump 9-1 (step S110), and if INV <INV _MIN sp (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 calculation unit 14B is output as the inverter output INV to the inverter pump 9-1 ( Step S110).

In this case, the lower limit set value INV _MIN sp of the changed inverter output is calculated as INV _MIN sp suitable for the current pump front-rear differential pressure ΔPpvnow (changed set differential pressure ΔPsp) by the calculation according to the equation (1). Therefore, during the regulation of the inverter output INV at the lower limit set value INV _MIN sp, the pressure of the inverter pump 9-1 does not become lower than the pressure applied at that time, and the pressure loss state does not occur. . Further, since the lower limit set value INV _MIN sp is set as the inverter output immediately before the inverter pump 9-1 is closed, it does not increase energy.

  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 an example, as shown in FIG. 5, it is conceivable to provide a set differential pressure determination unit 14G in the control device 14 so as to determine the set differential pressure ΔPsp according to the measured 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. 6 shows a flowchart corresponding to FIG. 3 when the set differential pressure ΔPsp is changed according to the load flow rate QF. In this flowchart, in step S300, the measured load flow rate QF is captured, and in step S301, 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 S302-S310 corresponding to step S102-S110 is performed. By doing so, when the load flow rate QF is small, that is, when the valve 6-1 in the external load 3 is throttled (when the terminal differential pressure is high), the rotational speed of the inverter pump 9-1. As a result, the energy can be saved. Such control is referred to as variable water pressure control based on the load flow rate.

  FIG. 7A shows the relationship (QH characteristics) between the flow rate and pressure when the inverter pump 9-1 alone is operated alone. In FIG. 7A, characteristic I shows the relationship between the set differential pressure ΔPsp and the flow rate, and characteristic II shows the relationship between the pump pressure and the flow rate when the inverter output INV is 100% (QH during constant speed operation). Characteristic III shows the relationship between the pump pressure and the flow rate when the inverter output INV is regulated by the lower limit set value INVsp with the set differential pressure ΔPsp when the flow rate is zero (the cutoff state QH characteristic). In this case, the set differential pressure ΔPsp increases as the load flow rate increases, and when the pump front-rear differential pressure ΔPpv increases following this set differential pressure ΔPsp, the lower limit setting of the inverter output is calculated by the calculation according to the above equation (1). The value INVsp goes up.

  FIG. 7B shows the relationship (QH characteristics) between the flow rate and pressure during parallel operation of the inverter pump 9-1 and the constant speed pump 9-2. In FIG. 7B, the characteristic I shows the relationship between the set differential pressure ΔPsp and the flow rate, and the characteristic IV shows the relationship between the pump pressure and the flow rate when the inverter output INV is 100% (QH during constant speed operation). The characteristic V indicates the relationship between the pump pressure and the flow rate when the inverter output INV is regulated by the lower limit set value INVsp with the set differential pressure ΔPsp secured only by the constant speed pump 9-2 (the cutoff state QH). Characteristic). In this case, the set differential pressure ΔPsp increases as the load flow rate increases, and when the pump front-rear differential pressure ΔPpv increases following this set differential pressure ΔPsp, the lower limit setting of the inverter output is calculated by the calculation according to the above equation (1). The value INVsp goes up.

  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 3 is actually measured as the terminal differential pressure, and the set differential pressure ΔPsp is changed according to the measured terminal differential pressure. It is also possible to do. 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. For example, when there are a plurality of external loads 3, the opening degree of the valve 3-1 in these external loads 3 is monitored, and the opening degree of the valve 3-1 includes 100% opening degree. If so, it is conceivable to increase the set differential pressure ΔPsp.

In the above-described embodiment, the current pump differential pressure ΔPpv is used when calculating the lower limit value INV _MIN of the inverter output. However, the current set differential pressure ΔPsp may be used. In this case, the following formula (2) is used instead of the above formula (1).
INV _MIN = (ΔPsp / P _SHUT ) ^1/2 + α (2)

  In the above-described embodiment, the differential pressure of the heat source water between the first forward header 4-1 and the second forward header 4-2 is measured as the pump front-rear differential pressure ΔPpv, and this pump front-rear differential pressure is measured. Although the system in which ΔPpv is made to coincide with the set differential pressure ΔPsp has been described, the same applies to a system in which the water supply pressure of the heat source water to the external load 3 is measured and this water supply pressure is made to coincide with the set water supply pressure. A scheme can be adopted.

  In this case, as shown in FIG. 8, the water supply pressure PSpv of the heat source water from the second forward header 4-2 is measured by the pressure sensor 15, and the measured water supply pressure PSpv is sent to the control device 14. The control device 14 compares the water supply pressure PSpv from the pressure sensor 15 with the set water supply pressure PSsp, and the inverter output INV to the inverter pump 9-1 and the valve opening to the bypass valve 10 so that PSpv = PSsp. Adjust the output θ.

At this time, the control device 14 takes in the set water pressure PSsp as the current set water pressure PSspnow (FIG. 9: Step S401), takes in the water pressure PSpv measured by the pressure sensor 15 as the current water supply ΔPSpvnow (Step S402), The lower limit value INV _MIN now of the inverter output is calculated from the fetched water supply pressure PSpvnow and the rated cutoff pressure P _SHUT stored in the rated cutoff pressure storage unit 14A using the following equation (3) (step) S403).

INV _MIN = ((PSpv−Pback) / P _SHUT ) ^1/2 + α (3)
In this equation (3), Pback indicates the back pressure of the pump (the pressure of the heat source water in the forward header 4-1), and this back pressure Pback is set in advance as a predetermined value.

The calculated lower limit value INV _MIN now of the inverter output is set as the lower limit set value INV _MIN sp of the inverter output at the current water supply pressure PSpvnow (step S404). Thereafter, the processes of steps S404 to S410 are executed in the same manner as steps S104 to S110 in the flowchart shown in FIG.

  In this system as well, the set water supply pressure PSsp may be changed manually or automatically, as in the system for controlling the differential pressure across the pump to be constant. FIG. 10 shows a flowchart corresponding to FIG. 6 when the set water supply pressure PSsp is changed according to the load flow rate QF.

In this system, when calculating the lower limit value INV _MIN of the inverter output, the current set water supply pressure PSsp may be used instead of the current water supply pressure PSpv. In this case, the following equation (4) is used instead of the above equation (3).
INV _MIN = ((PSsp−Pback) / P _SHUT ) ^1/2 + α (4)

  In the embodiment described above, the secondary pump 9 is two units of the inverter pump 9-1 and the constant speed pump 9-2 in order to simplify the explanation, but the inverter pump 9-1 and the constant speed pump are used. Any system can be used as long as 9-2 is mixed, and the number is not limited to one. For example, a system with one inverter pump 9-1 and a plurality of constant speed pumps 9-2 may be used. Further, a plurality of inverter pumps 9-1 may be provided.

  The water supply pressure control system and method of the present invention can be used in various fields such as a heat load such as an air conditioner and a fan coil, and a cooling and heating system using a district cooling and heating consumer as an external load.

  DESCRIPTION OF SYMBOLS 1 ... Heat source machine, 2 ... Primary pump, 3 ... External load, 3-1 ... Valve, 4-1 ... 1st outbound header, 4-2 ... 2nd outbound header, 5 ... Outbound pipeline, 6 ... Return water pipe, 7 ... Return header, 8 ... Bypass pipe, 9 ... Secondary pump, 9-1 ... First secondary pump (inverter pump), 9-2 ... Second secondary pump (constant speed pump) 10) Bypass valve, L1 ... Bypass path, 11 ... Inverter, 12 ... Differential pressure sensor, 13 ... Flow meter, 14 ... Control device, 14A ... Rated cutoff pressure storage unit, 14B ... Inverter output lower limit value calculation unit, DESCRIPTION OF SYMBOLS 14C ... Inverter output calculation part, 14D ... Inverter output control part, 14E ... Valve opening output calculation part, 14F ... Operation number control part, 14G ... Set differential pressure determination part, 15 ... Pressure sensor.

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;
First and second forward headers provided in a supply path to the external load of heat source water from the heat source unit;
A pump capable of adjusting the rotational speed is a first secondary pump, and a pump operated at the rated rotational speed is a second secondary pump. The first secondary pump and the second secondary pump are mixed. A plurality of secondary pumps having the same rated rotational speed and connected in parallel between the first forward header and the second forward header;
A bypass valve provided in a bypass passage for communicating the first forward header and the second forward header;
The pressure difference between the heat source water between the first forward header and the second forward header is defined as a pump front-rear differential pressure, and the first secondary pressure is set so that the pump front-rear differential pressure and the set differential pressure coincide with each other. In a water supply pressure control system comprising an inverter output for controlling the rotational speed to the pump and a control means for adjusting a valve opening output for opening control to the bypass valve,
The control means includes
The lift at zero flow rate when the secondary pump is rotated at the rated rotational speed is defined as a cutoff pressure at the rated time, and the first secondary pump is calculated from the cutoff pressure at the rated time and the current differential pressure across the pump. Inverter output lower limit value calculating means for calculating the lower limit value of the inverter output to,
The lower limit value of the inverter output calculated by the inverter output lower limit value calculation means is set as the current lower limit set value of the inverter output, and the inverter output to the first secondary pump is restricted so as not to fall below the lower limit set value. An inverter output regulating means. A water supply pressure control system comprising: In the water supply pressure control system according to claim 1,
A water supply pressure control system comprising: a set differential pressure changing means for changing the set differential pressure. In the water supply pressure control system according to claim 1,
Load flow rate measuring means for measuring the flow rate of the heat source water returned from the external load as a load flow rate,
A water supply pressure control system comprising: a set differential pressure determining unit that determines the set differential pressure based on the measured load flow rate. In the water supply pressure control system described in any one of Claims 1-3,
Instead of the inverter output lower limit calculation means,
The lift at zero flow rate when the first secondary pump is rotated at the rated rotational speed is defined as the cutoff pressure at the rated time, and the first 2 is calculated from the cutoff pressure at the rated time and the current set differential pressure. A water supply pressure control system comprising means for calculating a lower limit value of an inverter output to the next pump. In the water supply pressure control system described in any one of Claims 1-4,
The control means includes
Use the water supply pressure of the heat source water from the second forward header instead of the pump front-rear differential pressure,
A water supply pressure control system using a set water supply pressure instead of the set differential pressure. A heat source unit that generates heat source water, a primary pump that conveys the heat source water generated by the heat source unit, and first and second outputs provided in a supply path from the heat source unit to an external load of the heat source water. A header and a pump capable of adjusting the rotational speed are a first secondary pump, and a pump operated at a rated rotational speed is a second secondary pump. The first secondary pump and the second secondary pump A plurality of secondary pumps having the same rated rotational speed and connected in parallel between the first forward header and the second forward header, and the first forward header and the second forward header The differential pressure of the heat source water between the bypass valve provided in the bypass passage that communicates with the first forward header and the second forward header is used as a pump front-rear differential pressure, and the pump front-rear differential pressure and the set difference The inverter output for controlling the rotational speed to the first secondary pump and the output of the first secondary pump so that the pressure matches. In water supply pressure control method for adjusting the valve opening degree output for opening control to the bypass valve,
The lift at zero flow rate when the secondary pump is rotated at the rated rotational speed is defined as a cutoff pressure at the rated time, and the first secondary pump is calculated from the cutoff pressure at the rated time and the current differential pressure across the pump. Calculating a lower limit value of the inverter output to
And a step of setting the lower limit value of the calculated inverter output as a lower limit set value of the current inverter output and regulating the inverter output to the first secondary pump so as not to fall below the lower limit set value. Water supply pressure control method. In the water supply pressure control method according to claim 6,
A water supply pressure control method comprising the step of changing the set differential pressure. In the water supply pressure control method according to claim 6,
Measuring the flow rate of the heat source water returned from the external load as a load flow rate,
A water pressure control method comprising: determining the set differential pressure based on the measured load flow rate. In the water supply pressure control method described in any one of Claims 6-8,
Instead of calculating the lower limit value of the inverter output,
The lift at zero flow rate when the first secondary pump is rotated at the rated rotational speed is defined as the cutoff pressure at the rated time, and the first 2 is calculated from the cutoff pressure at the rated time and the current set differential pressure. A water supply pressure control method comprising: calculating a lower limit value of an inverter output to the next pump. In the water supply pressure control method described in any one of Claims 6-9,
Use the water supply pressure of the heat source water from the second forward header instead of the pump front-rear differential pressure,
A set water supply pressure is used instead of the set differential pressure.

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