CN112254237A - Air conditioner circulating water system pressure difference control system - Google Patents

Air conditioner circulating water system pressure difference control system Download PDF

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CN112254237A
CN112254237A CN202010994175.4A CN202010994175A CN112254237A CN 112254237 A CN112254237 A CN 112254237A CN 202010994175 A CN202010994175 A CN 202010994175A CN 112254237 A CN112254237 A CN 112254237A
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CN112254237B (en
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陈明锋
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Wuxi Chaotic Energy Technology Co ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F5/00—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
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Abstract

The invention discloses a variable pressure difference control system of an air conditioner circulating water system, which relates to the field of intelligent control of air conditioners and comprises a water collector, a water separator, a refrigeration host, a refrigeration circulating pump, a variable pressure difference controller, a water pump frequency converter, a flowmeter and a water pipe pressure difference sensor, wherein the water pump frequency converter, the flowmeter and the water pipe pressure difference sensor are connected with the variable pressure difference controller; the system comprises a water pump frequency converter, a freezing circulating pump, a water pipe differential pressure sensor, a flow meter, a main pipe supply and return water differential pressure set value algorithm model, a variable pressure differential controller, a PID algorithm and a PID algorithm, wherein the water pump frequency converter is connected with the freezing circulating pump, the water pipe differential pressure sensor is arranged on a pipeline between a water collector and a water distributor, the flow meter is arranged on a return water pipeline of the water collector, the main pipe supply and return water differential pressure set value algorithm model is deployed in the variable pressure differential controller, the variable pressure differential controller obtains the actual measurement flow of the freezing water and substitutes the actual measurement flow into the algorithm model to obtain the main pipe supply and return water.

Description

Air conditioner circulating water system pressure difference control system
Technical Field
The invention relates to the field of intelligent control of air conditioners, in particular to a variable pressure difference control system of an air conditioner circulating water system.
Background
The energy consumption of a central air-conditioning water system occupies about 60% of the total energy consumption of a building, the central air-conditioning system transmits chilled water to the tail end of an air conditioner through a chilled water circulating pump, and the tail end automatically adjusts the flow of the chilled water according to the load demand. The flow of the freezing water is too small, so that the flow requirement of the tail end cannot be ensured; the refrigerating water flow is too large, so that the pipeline resistance is increased, and the energy consumption of transmission and distribution is increased.
The prior commonly used variable flow control method of the chilled water circulation system has the following defects:
(1) the main pipe temperature difference control method is characterized in that the temperature difference of a water supply main pipe and a water return main pipe is kept unchanged, when the tail end load changes, the rotating speed and the water flow of a water pump are adjusted through a temperature difference controller and a water pump frequency converter, the adjusting method is only suitable for small systems with synchronous tail end load change trends and is not suitable for systems with large tail end load differences, and the worst tail end pressure difference is too small or the pressure difference is too large;
(2) the main pipe pressure difference control method is characterized in that a pressure difference controller is arranged between water supply and return main pipes, the change of terminal loads is not considered in the running process of a system, only the pressure difference between the main pipes is kept unchanged, the method cannot timely cope with the change of the terminal loads, and the worst terminal pressure difference is too small or the pressure difference is too large.
Disclosure of Invention
The invention provides a variable differential pressure control system of an air-conditioning circulating water system aiming at the problems and the technical requirements, the system can effectively avoid the problem of unstable remote communication, can also avoid the over-small or over-large differential pressure of the worst tail end, and can reduce the transmission and distribution energy consumption of the air-conditioning water system at the same time, and the technical scheme of the invention is as follows:
a variable pressure difference control system of an air conditioner circulating water system comprises a water collector, a water separator, a refrigeration host, a refrigeration circulating pump, a variable pressure difference controller, a water pump frequency converter, a flowmeter and a water pipe pressure difference sensor, wherein the water pump frequency converter, the flowmeter and the water pipe pressure difference sensor are connected with the variable pressure difference controller; the water outlet of the refrigeration host is connected with one end of a refrigeration circulating pump, the other end of the refrigeration circulating pump is connected with a water separator, a water collector is connected with the water inlet of the refrigeration host, a water pump frequency converter is connected with the refrigeration circulating pump and carries out frequency conversion adjustment on the refrigeration circulating pump, a water pipe differential pressure sensor is arranged on a pipeline between the water collector and the water separator, and a flowmeter is arranged on a return water pipeline of the water collector;
a manifold water supply and return pressure difference set value algorithm model is deployed in the variable pressure difference controller, the variable pressure difference controller obtains the actual measurement flow of the chilled water through a flowmeter and substitutes the actual measurement flow into the manifold water supply and return pressure difference set value algorithm model to obtain a manifold water supply and return pressure difference set value, and the variable pressure difference controller adjusts the frequency of the refrigeration circulating pump through a PID algorithm according to the manifold water supply and return pressure difference set value and a manifold water supply and return pressure difference actual measurement value collected by a water pipe pressure difference sensor.
The air conditioner circulating water system variable pressure difference control system further comprises an air conditioner tail end group, wherein the air conditioner tail end group comprises a plurality of air conditioner tail ends, air conditioner tail end regulating valves connected in series on water return pipe branches of the air conditioner tail ends and worst pressure difference sensors connected with the variable pressure difference controller, the air conditioner tail ends are arranged between the water collector and the water distributor in parallel, and the worst pressure difference sensors are arranged on worst air conditioner tail end pipelines at the air conditioner tail ends;
acquiring and storing a main pipe supply and return water pressure difference measured value, a chilled water flow and a worst tail end pressure difference value through a water pipe pressure difference sensor, a flow meter and a worst pressure difference sensor, taking the measured values as data samples, continuously adjusting the opening and the opening number of a tail end adjusting valve of the air conditioner to change the resistance characteristic of a tail end pipe network, and acquiring a large number of data samples under different tail end pipe network resistance characteristics;
preprocessing the data sample, and screening out the most unfavorable tail end pressure difference value meeting the preset conditions and the corresponding actual measured value of the pressure difference of the main pipe supply water and the main pipe return water and the flow of the chilled water; wherein the predetermined conditions are:
90% end rated water pressure drop < worst end differential pressure value < 110% end rated water pressure drop;
performing model training on the screened data samples by adopting a random forest method, fitting the characteristic relation between the actual measured value of the pressure difference between the supply water and the return water of the header pipe and the flow rate of the chilled water, and determining an algorithm model of the set value of the pressure difference between the supply water and the return water of the header pipe as follows:
ΔPS＝(ΔPmax-ΔPmin)·[ax2+(1-a)x]+ΔPmin
wherein, Δ PSSupply and return pressure difference set value, delta P, for main pipemaxFor a terminal full open maximum pressure differential set point, Δ PminIs a set value of minimum differential pressure at the end of the full-open, a is a characteristic coefficient of resistance of the pipeline, x is a flow coefficient, and
Figure BDA0002691933640000021
q is the actually measured flow of the chilled watersThe maximum design flow.
When the measured value of the pressure difference between the water supply and the water return of the main pipe is smaller than the set value of the pressure difference between the water supply and the water return of the main pipe, the variable pressure difference controller controls the frequency converter of the water pump to increase the frequency of the refrigeration circulating pump according to the set value of the frequency obtained by the PID algorithm; when the actual measured value of the pressure difference between the water supply and the water return of the header pipe is larger than the set value of the pressure difference between the water supply and the water return of the header pipe, the variable pressure difference controller controls the frequency converter of the water pump to reduce the frequency of the refrigeration circulating pump according to the frequency set value obtained by the PID algorithm, so that the actual measured value of the pressure difference between the water supply and the water return of the header pipe collected by the pressure difference sensor.
The air conditioner circulating water system variable pressure difference control system further comprises a bypass regulating valve connected with the variable pressure difference controller, and the bypass regulating valve is arranged on a header pipe of the water collector and the water distributor;
in the control process, when the actual measured value of the pressure difference of the water supply and return of the header pipe is greater than the maximum pressure difference set value of the full opening at the tail end, the variable pressure difference controller controls the opening of the bypass regulating valve to increase according to the opening value of the bypass regulating valve obtained by the PID algorithm; when the actual measured value of the pressure difference between the water supply and the water return of the header pipe is smaller than the set value of the maximum pressure difference between the tail ends of the header pipe and the water return, the variable pressure difference controller controls the opening of the bypass regulating valve to be reduced according to the opening value of the bypass regulating valve obtained by the PID algorithm, so that the actual measured value of the pressure difference between the water supply and the water return of the header pipe is not higher than.
The system comprises a variable pressure difference control system of the air-conditioning circulating water system, a master pipe supply and return water pressure difference real-time measured value and a master pipe supply and return water pressure difference set value, wherein the variable pressure difference control system of the air-conditioning circulating water system also comprises a workstation connected with the variable pressure difference controller, and the workstation records the frozen water flow, the master pipe supply and return water pressure difference real-time measured value and the master pipe supply and return water pressure difference set value in real time, is used for; and modifying and optimizing an algorithm model of a main pipe water supply and return pressure set value through a workstation.
The beneficial technical effects of the invention are as follows:
(1) the local acquisition control is realized through the variable differential pressure controller, so that the variable differential pressure control system is ensured to directly acquire the required feedback signal and send the corresponding control signal, the instability of remote transmission communication signal transmission and the complexity of signal interface butt joint are effectively avoided, and the stability of the flow control of the air-conditioning circulating water system is improved;
(2) the method comprises the steps that a main pipe water supply and return pressure difference set value algorithm model is designed in a variable pressure difference controller in advance, in the control process, a main pipe water supply and return pressure difference set value is automatically calculated through the acquired actually measured flow of chilled water, and then is compared with the main pipe water supply and return pressure difference measured value, the variable pressure difference controller adjusts the frequency of a refrigeration circulating pump through a PID algorithm, the refrigeration circulating pump is guaranteed to run at the optimal frequency, the condition that the worst end pressure difference is too small or the pressure difference is too large is effectively avoided, the flow supply requirement is guaranteed, and meanwhile, the transmission and distribution energy consumption and the running;
(3) the bypass regulating valve is controlled to ensure that the variable differential pressure control system of the air-conditioning circulating water system cannot generate overpressure under the working condition that the refrigeration circulating pump runs at the optimal frequency, so that the safety of the system is improved.
(4) The variable differential pressure control system of the air conditioner circulating water system is an integrated system, construction according to design drawings on site is guaranteed, the phenomenon that the installation position of the worst differential pressure sensor is difficult to determine and is difficult to construct is effectively avoided, and the operation difficulty of site construction is reduced.
Drawings
Fig. 1 is a schematic block diagram of a variable pressure difference control system of an air conditioner circulating water system provided by the present application.
FIG. 2 is a flow chart of an algorithm model for designing a total pipe supply and return water pressure difference set value provided by the application.
Fig. 3 is a logic diagram for the freeze cycle pump frequency adjustment provided herein.
FIG. 4 is a logic diagram of the bypass regulator valve opening adjustment provided herein.
FIG. 5 is a logical schematic of the PID algorithm provided herein.
Fig. 6 is a graph for verifying the experimental result of the variable pressure difference control system of the air-conditioning circulating water system provided by the application.
Detailed Description
The following further describes the embodiments of the present invention with reference to the drawings.
The application discloses air conditioner circulating water system becomes pressure differential control system, its system's functional block diagram is shown in fig. 1, including water collector 1, water knockout drum 2, refrigeration host computer 3, refrigeration circulating pump 4, air conditioner end group, vary voltage difference controller 5 and with vary voltage difference controller 5 water pump converter 6, flowmeter 7 and the water pipe differential pressure sensor 8 that passes through the signal line and link to each other.
The water outlet of the refrigeration host 3 is connected with one end of a refrigeration circulating pump 4, the other end of the refrigeration circulating pump 4 is connected with a water separator 2, and a water collector 1 is connected with the water inlet of the refrigeration host 3. Optionally, this application adopts a plurality of parallel operation's refrigeration circulating pump 4, and every water pump converter 6 passes through the motor of a refrigeration circulating pump 4 of power line connection and carries out the frequency conversion regulation to it. The water pipe differential pressure sensor 8 is arranged on a pipeline between the water collector 1 and the water separator 2, and the flowmeter 7 is arranged on a water return pipeline of the water collector 1. The air conditioner tail end group comprises a plurality of air conditioner tail ends 9, air conditioner tail end regulating valves 10 which are connected in series on water return pipe branches of the air conditioner tail ends 9, and worst differential pressure sensors 11 which are connected with the variable differential pressure controller 5, wherein the air conditioner tail ends 9 are arranged between the water collector 1 and the water distributor 2 in parallel, and the worst differential pressure sensors 11 are arranged on worst air conditioner tail end pipelines of the air conditioner tail ends 9. The variable differential pressure control system of the air conditioner circulating water system is an integrated system, construction according to design drawings on site is guaranteed, the phenomenon that the installation position of the worst differential pressure sensor is difficult to determine and is difficult to construct is effectively avoided, and the operation difficulty of site construction is reduced.
A main pipe supply and return water differential pressure set value algorithm model is deployed in the variable pressure differential controller 5, the variable pressure differential controller 5 obtains the actual measurement flow of the chilled water through a flowmeter 7 and substitutes the actual measurement flow into the main pipe supply and return water differential pressure set value algorithm model to obtain a main pipe supply and return water differential pressure set value, and the variable pressure differential controller 5 adjusts the frequency of the refrigeration circulating pump 4 through a PID algorithm according to the main pipe supply and return water differential pressure set value and a main pipe supply and return water differential pressure measured value collected by a water pipe differential pressure sensor 8.
The flow chart of the algorithm model for designing the set value of the pressure difference between the water supply and the water return of the main pipe is shown in figure 2, and comprises the following steps:
step 1: the water pipe differential pressure sensor 8, the flowmeter 7 and the most unfavorable differential pressure sensor 11 collect and store a main water supply and return water differential pressure measured value, a chilled water flow and a most unfavorable terminal differential pressure value, and the measured values are used as data samples, and meanwhile, the opening degree and the opening quantity of the air conditioner terminal adjusting valve 10 are continuously adjusted to change the terminal pipe network resistance characteristics, so that a large number of data samples are obtained under different terminal pipe network resistance characteristics. The resistance characteristic of the end pipe network is a characteristic coefficient of the pressure difference control system.
Step 2: and preprocessing the data sample, and screening out the most unfavorable tail end pressure difference value meeting the preset conditions, the corresponding actual measured value of the pressure difference of the main water supply and return water and the flow rate of the frozen water.
Wherein the predetermined conditions are:
90% end rated water pressure drop < worst end pressure drop value < 110% end rated water pressure drop, the end rated water pressure drop being a known constant.
And step 3: performing model training on the screened data samples by adopting a random forest method, fitting the characteristic relation between the actual measured value of the pressure difference between the supply water and the return water of the header pipe and the flow rate of the chilled water, and determining an algorithm model of the set value of the pressure difference between the supply water and the return water of the header pipe as follows:
ΔPS＝(ΔPmax-ΔPmin)·[ax2+(1-a)x]+ΔPmin
wherein, Δ PSSupply and return pressure difference set value, delta P, for main pipemaxFor a terminal full open maximum pressure differential set point, Δ PminIs a set value of minimum differential pressure at the end of the full-open, a is a characteristic coefficient of resistance of the pipeline, x is a flow coefficient, and
Figure BDA0002691933640000051
q is the actually measured flow of the chilled watersFor maximum design flow, Δ P as described abovemax、ΔPminA and QsAre all known constants.
In a further aspect, the variable pressure difference controller 5 adjusts the frequency of the refrigeration circulating pump 4 by a PID algorithm according to a difference between a set value of the pressure difference between the water supply and return of the header pipe and an actual measured value of the pressure difference between the water supply and return of the header pipe acquired by the pressure difference sensor 8 of the water pipe, and a logic diagram of the frequency adjustment of the refrigeration circulating pump is shown in fig. 3, and specifically includes:
when the actual measured value of the pressure difference between the water supply and the water return of the header pipe is smaller than the set value of the pressure difference between the water supply and the water return of the header pipe, the variable pressure difference controller 5 controls the water pump frequency converter 6 to increase the frequency of the refrigeration circulating pump 4 according to the set value of the frequency obtained by the PID algorithm; when the actual measured value of the pressure difference between the water supply and the water return of the header pipe is larger than the set value of the pressure difference between the water supply and the water return of the header pipe, the variable pressure difference controller 5 controls the frequency converter 6 of the water pump to reduce the frequency of the freezing circulating pump 4 according to the frequency set value obtained by the PID algorithm, the frequency of the freezing circulating pump 4 is changed between the maximum frequency set value and the minimum frequency set value, and the actual measured value of the pressure difference between the water supply and the water return of the header pipe collected by the. Such as: (1) measured value delta P of pressure difference between water supply and water return of main pipe is 150kPa<Pressure difference set value delta P for supplying and returning water of main pipeSWhen 180kPa is satisfied, the frequency of the refrigerating cycle pump 4 is increased; (2) the measured value delta P of the pressure difference between the water supply and the water return of the header pipe is 180kPa & gt the set value delta P of the pressure difference between the water supply and the water return of the header pipeSThe frequency of the refrigerating cycle pump 4 is decreased at 150 kPa.
Optionally, the air-conditioning circulating water system pressure difference control system further comprises a bypass regulating valve 12 connected with the pressure difference controller 5, and the bypass regulating valve 12 is arranged on the header pipe of the water collector 1 and the water separator 2.
In the control process, the variable pressure difference controller 5 obtains the opening value of the bypass regulating valve 12 through a PID algorithm according to the difference between the final full-open maximum differential pressure setting value and the actual measured value of the main pipe supply and return water differential pressure, and a logic diagram of the opening adjustment of the bypass regulating valve is shown in fig. 4, and specifically includes:
when the actual measured value of the pressure difference between the water supply and the water return of the header pipe is larger than the set value of the maximum pressure difference of the tail end full opening, the variable pressure difference controller 5 controls the opening of the bypass regulating valve 12 to increase according to the opening value of the bypass regulating valve obtained by the PID algorithm; when the actual measured value of the pressure difference between the water supply and the water return of the header pipe is smaller than the set value of the maximum pressure difference between the tail ends of the two pipes, the variable pressure difference controller 5 controls the opening of the bypass regulating valve 12 to be reduced according to the opening value of the bypass regulating valve obtained by the PID algorithm, so that the actual measured value of the pressure difference between the water supply and the water return of the header pipe is not higher than theA pressure differential set point. Such as: (1) the measured value delta P of the pressure difference between the water supply and the water return of the main pipe is 230kPa > the maximum pressure difference set value delta P of the full opening at the tail endmaxThe opening degree of the bypass regulating valve 12 is increased as 220 kPa; (2) measured value delta P of pressure difference between water supply and water return of header pipe is 180kPa<End full open maximum differential pressure setpoint Δ PmaxWhen the optimum frequency of the refrigerating cycle pump 4 is not reached, the opening degree of the bypass adjusting valve 12 can be appropriately reduced at 220 kPa. The opening of the bypass adjusting valve 12 is controlled to ensure that the variable differential pressure control system of the air-conditioning circulating water system cannot generate overpressure under the working condition that the refrigeration circulating pump operates at the optimal frequency, so that the safety of the system is improved.
The logic diagram of the PID algorithm is shown in FIG. 5, and the set value delta P of the pressure difference between the supply water and the return water of the main pipe is input into the PID algorithmSAnd a measured value delta P of the pressure difference between the water supply and the water return of the header pipe are regulated by PID, and then a frequency set value is input into the refrigeration circulating pump 4 through an actuating mechanism (namely a water pump frequency converter 6). Or inputting a tail end full-open maximum pressure difference set value delta P into the PID algorithmmaxAnd a measured value delta P of the pressure difference between the water supply and the water return of the header pipe are input into the bypass regulating valve 12 through an actuating mechanism (namely, the variable pressure difference controller 5) after PID regulation. The measuring element in the figure is also the water pipe differential pressure sensor 8.
Optionally, the variable pressure difference control system of the air-conditioning circulating water system further comprises a workstation 13 connected with the variable pressure difference controller 5, wherein the workstation 13 records the freezing water flow, the actual measured value of the total pipe supply and return water pressure difference and the set value of the total pipe supply and return water pressure difference in real time, and is used for analyzing the performance of the variable pressure difference control system of the air-conditioning circulating water system to play a monitoring role; the algorithm model for optimizing the set value of the pressure difference between the water supply and the water return of the main pipe can be modified through the workstation 13.
In this embodiment, the actual air-conditioning circulating water system is used to verify the pressure difference control system, and the result is shown in fig. 6. As can be seen from the figure 6, the set value of the pressure difference of the water supply and the water return of the main pipe is automatically adjusted along with the change of the actually measured flow, the pressure difference of the worst tail end is stabilized at the qualification pressure head, and the control precision is up to +/-5 percent.
The variable differential pressure control system of the air-conditioning circulating water system effectively avoids instability of remote communication signal transmission and complexity of signal interface butt joint through local acquisition control of the variable differential pressure controller, improves stability of flow control of the air-conditioning circulating water system, avoids over-small or over-large differential pressure at the worst tail end, reduces transmission and distribution energy consumption and operation cost of the air-conditioning circulating water system while guaranteeing flow supply requirements, and has very important realization significance on automatic control of a central air-conditioning water system.
What has been described above is only a preferred embodiment of the present application, and the present invention is not limited to the above embodiment. It is to be understood that other modifications and variations directly derivable or suggested by those skilled in the art without departing from the spirit and concept of the present invention are to be considered as included within the scope of the present invention.

Claims (5)

1. A variable pressure difference control system of an air conditioner circulating water system is characterized by comprising a water collector, a water separator, a refrigeration host, a refrigeration circulating pump, a variable pressure difference controller, a water pump frequency converter, a flowmeter and a water pipe pressure difference sensor, wherein the water pump frequency converter, the flowmeter and the water pipe pressure difference sensor are connected with the variable pressure difference controller; the water outlet of the refrigeration host is connected with one end of the refrigeration circulating pump, the other end of the refrigeration circulating pump is connected with the water separator, the water collector is connected with the water inlet of the refrigeration host, the water pump frequency converter is connected with the refrigeration circulating pump and performs frequency conversion adjustment on the refrigeration circulating pump, the water pipe differential pressure sensor is arranged on a pipeline between the water collector and the water separator, and the flowmeter is arranged on a water return pipeline of the water collector;
the variable pressure difference controller is provided with a main pipe supply and return water differential pressure set value algorithm model, the variable pressure difference controller obtains the actual measurement flow of the chilled water through the flowmeter and substitutes the actual measurement flow into the main pipe supply and return water differential pressure set value algorithm model to obtain a main pipe supply and return water differential pressure set value, and the variable pressure difference controller adjusts the frequency of the refrigeration circulating pump through a PID algorithm according to the main pipe supply and return water differential pressure set value and a main pipe supply and return water differential pressure measured value collected by the water pipe differential pressure sensor.
2. The air-conditioning circulating water system variable pressure difference control system as claimed in claim 1, wherein the air-conditioning circulating water system variable pressure difference control system further comprises an air-conditioning end group, the air-conditioning end group comprises a plurality of air-conditioning ends, air-conditioning end regulating valves connected in series on water return pipe branches of the air-conditioning ends, and worst pressure difference sensors connected with the variable pressure difference controller, the air-conditioning ends are arranged in parallel between the water collector and the water separator, and the worst pressure difference sensors are arranged on worst air-conditioning end pipes of the air-conditioning ends;
acquiring and storing a main water supply and return water pressure difference measured value, a chilled water flow and a most unfavorable tail end pressure difference value through the water pipe pressure difference sensor, the flow meter and the most unfavorable pressure difference sensor, taking the measured values as data samples, continuously adjusting the opening and the opening number of the air conditioner tail end adjusting valve to change the tail end pipe network resistance characteristic, and acquiring a large number of data samples under different tail end pipe network resistance characteristics;
preprocessing the data sample, and screening out the worst tail end pressure difference value meeting the preset conditions and the corresponding actual measured value of the pressure difference of the main pipe supply and return water and the flow of the chilled water; wherein the predetermined condition is:
90% end rated water pressure drop < worst end differential pressure value < 110% end rated water pressure drop;
performing model training on the screened data samples by adopting a random forest method, fitting the characteristic relation between the actual measured value of the pressure difference between the supply water and the return water of the header pipe and the flow rate of the chilled water, and determining an algorithm model of the set value of the pressure difference between the supply water and the return water of the header pipe as follows:
ΔPS＝(ΔPmax-ΔPmin)·[ax2+(1-a)x]+ΔPmin
wherein, Δ PSSupply and return water pressure difference set value, delta P, for said main pipemaxFor a terminal full open maximum pressure differential set point, Δ PminIs a set value of minimum differential pressure at the end of the full-open, a is a characteristic coefficient of resistance of the pipeline, x is a flow coefficient, and
Figure FDA0002691933630000021
q is the actually measured flow of the chilled water, QsThe maximum design flow.
3. The air-conditioning circulating water system variable pressure difference control system as claimed in claim 1,
when the actual measured value of the pressure difference between the water supply and the water return of the header pipe is smaller than the set value of the pressure difference between the water supply and the water return of the header pipe, the variable pressure difference controller controls the frequency converter of the water pump to increase the frequency of the refrigeration circulating pump according to the set value of the frequency obtained by the PID algorithm; when the actual measured value of the pressure difference between the water supply and the water return of the header pipe is larger than the set value of the pressure difference between the water supply and the water return of the header pipe, the variable pressure difference controller controls the frequency converter of the water pump to reduce the frequency of the refrigeration circulating pump according to the frequency set value obtained by the PID algorithm, so that the actual measured value of the pressure difference between the water supply and the water return of the header pipe collected by the pressure difference sensor of the water pipe is maintained at the set.
4. The air-conditioning circulating water system variable pressure difference control system according to claim 1, wherein the air-conditioning circulating water system variable pressure difference control system further comprises a bypass regulating valve connected with the variable pressure difference controller, and the bypass regulating valve is arranged on a header pipe of the water collector and the water distributor;
in the control process, when the actual measured value of the pressure difference of the supply water and the return water of the header pipe is greater than the maximum pressure difference set value of the full opening at the tail end, the variable pressure difference controller controls the opening of the bypass regulating valve to increase according to the opening value of the bypass regulating valve obtained by the PID algorithm; when the actual measured value of the pressure difference between the water supply and the water return of the header pipe is smaller than the set value of the maximum pressure difference between the tail ends of the water supply and the water return, the variable pressure difference controller controls the opening of the bypass regulating valve to be reduced according to the opening value of the bypass regulating valve obtained by the PID algorithm, so that the actual measured value of the pressure difference between the water supply and the water return of the header pipe is not higher than the set value of the maximum pressure.
5. The air-conditioning circulating water system variable pressure difference control system according to any one of claims 1 to 4, wherein the air-conditioning circulating water system variable pressure difference control system further comprises a workstation connected with the variable pressure difference controller, and the workstation records the chilled water flow, the actual measured value of the total pipe supply and return water pressure difference and the set value of the total pipe supply and return water pressure difference in real time, is used for analyzing the performance of the air-conditioning circulating water system variable pressure difference control system, and plays a role in monitoring; and modifying and optimizing the algorithm model of the total pipe water supply and return pressure difference set value through the workstation.
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