Air conditioner variable flow cold water system and method for multi-stage pressure difference resetting

Abstract

The invention relates to the technical field of air conditioner control, and discloses a multi-stage pressure difference rearranged air conditioner variable flow cold water system which comprises a water supply main pipe on a user side, a water return main pipe, at least one vertical pipe system, a variable frequency water pump, a microcontroller MCU and a control unit on a network side, and the vertical pipe systems are arranged between the water supply main pipe and the water return main pipe in parallel. The variable-frequency water pump is arranged at the input end of the water supply main pipe; the vertical pipe system and the variable frequency water pump are both in signal connection with the microcontroller MCU, and the microcontroller MCU is in signal connection with the control unit through the wireless communication module. The invention further provides a control method of the multi-stage pressure difference rearranged air conditioner variable flow cold water system. Dynamic hydraulic balance can be performed according to actual conditions through multi-stage pressure difference re-setting and cooling capacity adjustment to adapt to loads, the required flow is guaranteed, the pressure difference of an inlet and an outlet of a water pump is reduced as much as possible, and the energy saving amount of a water system is increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of air conditioning control, and in particular relates to an air conditioning variable flow chilled water system and method with multi-stage pressure difference reset. Background Art

[0002] On-off control fan coil system is widely used in the field of building air conditioning in my country. Since the equipment selection of its chilled water system, such as water pumps and fan coils, is considered according to the most unfavorable working conditions under design conditions, and in actual operation, non-design conditions often occupy most of the operating time, it provides a lot of space for the variable water volume energy-saving operation of the system.

[0003] The variable water volume control methods currently used in on-off control fan coil air-conditioning systems mainly include main pipe pressure difference control method and terminal pressure difference control method. Their purpose is to achieve variable water volume energy saving on the basis of ensuring the designed pressure head. Among them, the energy saving effect of the terminal pressure difference control method is better than that of the main pipe pressure difference control method. Taking the terminal pressure difference control method as an example, when the load decreases, the frequency of closing the on-off control valve of the fan coil in the system increases (the opening rate decreases), which increases the pressure difference at the end of the pressure difference control, indicating that the flow through the fan coil exceeds the design flow. The pressure difference signal is fed back to the variable frequency water pump, and the pressure difference at the control end is reduced again and stabilized near the set value by reducing the frequency and reducing the pump head, thereby avoiding the occurrence of excessive flow at the end of the system and reducing "meaningless" flow waste. In this way, on the basis of ensuring that the flow through the fan coil is the design flow, its adaptability to load changes is actually adjusted by the opening rate of the fan coil. One problem brought about by this control method is that it does not adapt to load changes by reducing the flow of the fan coil, that is, by adjusting the cooling capacity, and the energy-saving potential of the water system has not been fully tapped. For example, the invention "Central Air Conditioning Refrigeration Station Quality Adjustment Control Method and System" with publication number CN200710118464.2 performs constant pressure difference control based on the terminal pressure difference at a certain point in the cold water supply network. When the load is reduced to 70%, the flow rate is reduced to 60%. This approximate synchronous decline is the main feature of the opening rate regulation. Although the flow rate decreases with the load reduction, the purpose of variable flow rate is achieved, but the characteristic that the fan coil flow rate decreases faster than the cooling capacity is not used to adapt to the load, which relatively reduces the energy saving effect. Another problem is that the hydraulic balance of the system is generally only for the design conditions. Under partial load conditions, it is not balanced, which can easily cause "overflow" conditions. Therefore, in combination with the above two problems, it is necessary to propose a variable flow system and control method for on-off control of fan coil systems. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an air-conditioning variable flow chilled water system and method with a multi-stage pressure difference reset, so that the chilled water system can provide water delivery that adapts to partial load conditions, so as to achieve a greater variable water volume energy-saving effect and improve the system's lifting water system energy saving.

[0005] In order to solve the above technical problems, the present invention provides an air conditioning variable flow chilled water system with multi-stage pressure difference reset, comprising a water supply main pipe, a return water main pipe, at least one riser system, a variable frequency water pump, a microcontroller MCU and a control unit on the network side, the riser system is arranged in parallel between the water supply main pipe and the return water main pipe, and the variable frequency water pump is arranged at the input end of the water supply main pipe;

[0006] The riser system and the variable frequency water pump are both connected to the microcontroller MCU signal, and the microcontroller MCU is connected to the control unit signal through the wireless communication module.

[0007] As an improvement of the air conditioning variable flow cold water system with multi-stage pressure difference reset of the present invention:

[0008] The riser system includes a water supply riser and a return riser. The water supply riser is connected to the water supply main pipe, and the return riser is connected to the return water main pipe. The riser dynamic pressure difference balancing valve is arranged at the input end of the water supply riser, and at least one horizontal pipe system is arranged in parallel between the water supply riser and the return riser.

[0009] As a further improvement of the air conditioning variable flow chilled water system with multi-stage pressure difference reset of the present invention:

[0010] The horizontal pipe system includes a water supply horizontal pipe and a return water horizontal pipe. The water supply horizontal pipe is connected to the water supply riser, and the return water horizontal pipe is connected to the return water riser. The horizontal pipe dynamic pressure difference balancing valve is arranged at the input end of the water supply horizontal pipe, and at least one branch pipe system is arranged in parallel between the water supply horizontal pipe and the return water horizontal pipe.

[0011] As a further improvement of the air conditioning variable flow chilled water system with multi-stage pressure difference reset of the present invention:

[0012] The branch pipe system comprises a water supply branch pipe and a water return branch pipe. The water supply branch pipe is connected with the water supply horizontal pipe. The water supply branch pipe is connected with the water return horizontal pipe after passing through the on-off valve, the fan coil unit and the water return branch pipe.

[0013] As a further improvement of the air conditioning variable flow chilled water system with multi-stage pressure difference reset of the present invention:

[0014] The control unit includes a main pipe pressure differential controller, a riser pressure differential controller and a cross pipe pressure differential controller; the fan coil, the cross pipe dynamic pressure differential balancing valve, the riser dynamic pressure differential balancing valve and the variable frequency water pump are all connected to the microcontroller MCU signal, and the microcontroller MCU is connected to the main pipe pressure differential controller, the riser pressure differential controller, the cross pipe pressure differential controller and the variable frequency water pump signal through a wireless communication module.

[0015] The present invention also provides a control method for an air-conditioning variable flow chilled water system using a multi-stage pressure difference reset, comprising:

[0016] S1. Operation of branch pipe system:

[0017] Each fan coil unit collects data and transmits it to the cross-pipe differential pressure controller, including room temperature, set room temperature, and the on / off status of the on / off valve;

[0018] S2. Operation of the cross pipe system:

[0019] The cross-pipe differential pressure controller selects the most unfavorable terminal device based on the same group of terminal device data, generates a differential pressure setting instruction, and sends it to the cross-pipe dynamic differential pressure balancing valve in the branch system where the most unfavorable terminal device is located to control the valve position opening;

[0020] Each horizontal pipe dynamic differential pressure balancing valve transmits valve position opening data to the vertical pipe differential pressure controller;

[0021] S3. Operation of the riser system

[0022] The riser pressure differential controller determines the most unfavorable cross pipe system from the valve position data sent by the dynamic pressure differential balancing valves of each cross pipe according to the same set of valve position data, and generates a pressure differential setting instruction, which is sent to the riser dynamic pressure differential balancing valve in the riser system where the most unfavorable cross pipe system is located, to control the valve position opening;

[0023] Each riser dynamic differential pressure balancing valve transmits valve position opening information to the main pipe differential pressure controller;

[0024] S4. Operation of the main pipe system

[0025] The main pipe pressure difference controller determines the most unfavorable riser system from the valve position data sent by the dynamic pressure difference balancing valves of each riser, and generates a main pipe pressure difference setting instruction to send to the variable frequency water pump; the variable frequency water pump controls the operating frequency according to the main pipe pressure difference setting instruction.

[0026] As an improvement of the control method of a multi-stage pressure difference reset air conditioning variable flow chilled water system of the present invention:

[0027] The judgment rule of the most unfavorable terminal device is:

[0028] For the feedback data of the fan coil units in the same group, the thermal comprehensive index of each fan coil unit terminal is calculated by weighting the temperature and temperature change. The terminal device with the highest thermal comprehensive index is the most unfavorable terminal device. The thermal comprehensive index is:

[0029] I k =(t k +g k1 Δt k )γ k2, k∈n (1)

[0030]

[0031] Where k is the fan coil terminal number, t k is the room temperature where the fan coil is located, Δt k is the temperature change of the room, γ k1 is the temperature change weighting coefficient, γ k2 is the room importance weighting coefficient, k max The number of the fan coil end with the highest comprehensive thermal index in the horizontal pipe system;

[0032] The setting rule of the pressure difference setting instruction of the cross-pipe dynamic pressure difference balancing valve (3) is:

[0033] p h =k p (I max / γ max -I 0,max )+k I ∫(I max / γ max -I 0,max )dt (3)

[0034] Where k p is the proportionality constant, k I is the integration constant, I max / γ max I is the most unfavorable thermal comprehensive index of the terminal equipment without considering the weighted coefficient of room importance, 0,max It is the setting value of the most unfavorable comprehensive thermal index of the terminal equipment.

[0035] As a further improvement of the control method of the air-conditioning variable flow chilled water system with multi-stage pressure difference reset of the present invention:

[0036] The most unfavorable cross pipe system is determined by the following rule: the cross pipe system where the cross pipe dynamic pressure difference balancing valve (3) with the largest valve position opening is located is the most unfavorable cross pipe system;

[0037] The setting rule of the pressure difference setting instruction of the riser dynamic pressure difference balancing valve (5) is:

[0038] p l =k p,h (y h,max -y h,0 )+k I,h ∫(y h,max -y h,0 )dt (4)

[0039] In the formula, y h,maxis the valve position of the cross pipe dynamic pressure differential balancing valve (3) in the most unfavorable cross pipe system, y h,0 It is the valve position setting value of the cross pipe dynamic pressure difference balancing valve in the most unfavorable cross pipe system.

[0040] As a further improvement of the control method of the air-conditioning variable flow chilled water system with multi-stage pressure difference reset of the present invention:

[0041] The judgment rule of the most unfavorable riser system is: the riser system where the riser dynamic pressure differential balancing valve with the largest valve position opening is located is the most unfavorable riser system;

[0042] The setting rules of the main pipe pressure difference setting instruction are:

[0043] p g =k p,l (y l,max -y l,0 )+k l,I ∫(y l,max -y l,0 )dt (5)

[0044] In the formula, y l,max is the valve position of the dynamic differential pressure balance valve of the most unfavorable riser system, y l,0 It is the valve position setting value of the riser dynamic pressure differential balancing valve of the most unfavorable riser system.

[0045] As a further improvement of the control method of the air-conditioning variable flow chilled water system with multi-stage pressure difference reset of the present invention:

[0046] The fan coil data collection period < the pressure difference instruction setting period of the horizontal pipe pressure difference controller < the pressure difference instruction setting period of the vertical pipe pressure difference controller < the pressure difference instruction setting period of the main pipe pressure difference controller.

[0047] The beneficial effects of the present invention are mainly reflected in:

[0048] The present invention realizes hydraulic balance of the cold water system through multi-stage pressure difference reset, thereby saving the transmission and distribution energy consumption of the cold water system.

[0049] The present invention can adapt to the load by adjusting the cooling capacity, and can perform dynamic hydraulic balance according to actual conditions, thereby ensuring the required flow rate and minimizing the pressure difference between the inlet and outlet of the water pump as much as possible, thereby increasing the energy saving of the water system, and realizing the smallest possible water supply to the cold water system under the premise of meeting the load requirements, and can dynamically determine the most unfavorable loop according to actual operating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings.

[0051] Figure 1It is a structural schematic diagram of an air-conditioning variable flow chilled water system with multi-stage pressure difference reset according to the present invention;

[0052] Figure 2 The present invention is a control flow diagram of an air-conditioning variable flow chilled water system with multi-stage pressure difference reset. DETAILED DESCRIPTION

[0053] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0054] Embodiment 1: A variable flow chilled water system for air conditioning with multi-stage pressure difference, such as Figure 1 shown.

[0055] The air-conditioning variable flow chilled water system with multi-stage pressure difference is mainly composed of a water supply main pipe, a return main pipe, a riser system, a variable frequency water pump 7, a microcontroller MCU and a control unit on the network side. Among them, the variable frequency water pump 7 is arranged at the input end of the water supply main pipe, and several riser systems are connected in parallel to the water supply main pipe and the return main pipe.

[0056] The riser system is mainly composed of a water supply riser, a return riser, a transverse pipe system and a riser dynamic differential pressure balancing valve 5. The water supply riser is connected to the water supply main pipe, the return riser is connected to the return water main pipe, the riser dynamic differential pressure balancing valve 5 is arranged at the input end of the water supply riser of each riser system, and a number of transverse pipe systems are connected in parallel to the water supply riser and the return riser.

[0057] The horizontal pipe system is mainly composed of a water supply horizontal pipe, a return horizontal pipe, a branch pipe system 1 and a horizontal pipe dynamic pressure difference balance valve 3. Among them, the water supply horizontal pipe is connected with the water supply riser, the return horizontal pipe is connected with the return riser, and the horizontal pipe dynamic pressure difference balance valve 3 is arranged at the input end of the water supply horizontal pipe. Several branch pipe systems 1 are connected in parallel to the water supply horizontal pipe and the return horizontal pipe.

[0058] The branch pipe system 1 is mainly composed of a water supply branch pipe, an on-off valve, a fan coil unit and a return branch pipe. The water supply branch pipe is connected to the water supply transverse pipe. The water supply branch pipe is connected to the return transverse pipe through the on-off valve, the fan coil unit and the return branch pipe. The feedback signal of the fan coil unit is the on / off state signal of the on-off valve and the room temperature signal.

[0059] The cold water in the water supply main pipe flows into each parallel riser system on the user side through the variable frequency water pump 7, and then flows out from the return water main pipe. In each riser system, cold water flows in from the water supply riser, flows into each parallel cross pipe system after passing through the riser dynamic pressure difference balancing valve 5, and then flows out from the return water riser into the return water main pipe. In each cross pipe system, cold water flows in from the water supply cross pipe, flows into each parallel branch pipe system 1 after passing through the cross pipe dynamic pressure difference balancing valve 3, and then flows out from the return water cross pipe into the return water riser. In each branch pipe system 1, cold water flows in through the water supply branch pipe, and then flows into the return water cross pipe through the on-off valve, fan coil unit, and return water branch pipe.

[0060] The control unit includes a main pipe differential pressure controller 6, a riser differential pressure controller 4 and a cross pipe differential pressure controller 2. The main pipe differential pressure controller 6, the riser differential pressure controller 4 and the cross pipe differential pressure controller 2 are all arranged on a cloud platform, and the cloud platform receives, stores and processes data sent from each fan coil unit, the cross pipe dynamic differential pressure balancing valve 3, the riser dynamic differential pressure balancing valve 5 and the variable frequency water pump 7. The fan coil unit, the cross pipe dynamic differential pressure balancing valve 3, the riser dynamic differential pressure balancing valve 5 and the variable frequency water pump 7 are all connected to the microcontroller MCU signal, and the microcontroller MCU is connected to the main pipe differential pressure controller 6, the riser differential pressure controller 4, the cross pipe differential pressure controller 2 and the variable frequency water pump 7 through a wireless communication module, such as a Wi-Fi module. Figure 2 shown.

[0061] The cross-pipe differential pressure controller 2 is used to receive feedback signals from each fan coil unit, and after signal analysis, it gives the differential pressure setting value of the cross-pipe dynamic differential pressure balancing valve 3. The cross-pipe dynamic differential pressure balancing valve 3 adjusts the valve opening according to the differential pressure setting value to keep the differential pressure between the water supply cross-pipe and the return cross-pipe within the set differential pressure range. The feedback signal of the cross-pipe dynamic differential pressure balancing valve 3 is: the opening signal of the cross-pipe dynamic balancing valve 3.

[0062] The riser pressure differential controller 4 is used to receive feedback signals from the dynamic pressure differential balancing valves 3 of each horizontal pipe, and after signal analysis, it gives the pressure differential setting value of the riser dynamic pressure differential balancing valve 5. The riser dynamic pressure differential balancing valve 5 adjusts the valve opening according to the pressure differential setting value to ensure that the pressure differential between the water supply riser and the return riser is kept within the set pressure differential range.

[0063] The main pipe differential pressure controller 6 receives the feedback signal from each riser dynamic differential pressure balancing valve 5, and gives the main pipe differential pressure setting value after signal analysis. The variable frequency water pump 7 adjusts its frequency according to the main pipe differential pressure setting value to ensure that the differential pressure between the water supply riser and the return riser is kept within the set differential pressure range.

[0064] The purpose of setting the pressure of the cross-pipe differential pressure controller 2 is to ensure that the cross-pipe water supply is as small as possible while ensuring the thermal comfort of the room supported by the branch pipe system 1, and at the same time to make the comprehensive resistance coefficient of the cross-pipe system as small as possible.

[0065] The purpose of setting the pressure of the riser differential pressure controller 4 is to make the comprehensive resistance coefficient of the riser system as small as possible.

[0066] The purpose of setting the pressure of the main pipe differential pressure controller 6 is to make the comprehensive resistance coefficient on the user side of the main pipe system as small as possible.

[0067] A control method for a variable flow chilled water system of an air conditioner with a multi-stage pressure difference reset of the present invention is as follows:

[0068] 1 Branch pipe system 1 operation steps

[0069] The fan coil unit (terminal device) of branch pipe system 1 controls the room temperature according to the local on-off control logic.

[0070] The data signals collected by each fan coil are connected to a wireless communication module, such as a Wi-Fi module, through a microcontroller MCU to transmit the data to the cross-pipe differential pressure controller 2. The transmitted information includes room temperature, set room temperature, and the on-off status of the on-off valve.

[0071] Terminal equipment connected to the same cross pipe system are considered as the same group.

[0072] 2 Operation steps of the cross pipe system

[0073] 2.1 Operation steps of cross pipe differential pressure controller 2

[0074] The cross pipe differential pressure controller 2 determines the most unfavorable terminal device based on the same set of terminal device data, and generates a corresponding pressure differential setting instruction for the cross pipe dynamic differential pressure balancing valve 3 (i.e., the branch pipe system 1 where the most unfavorable terminal device is located). The cloud platform returns the pressure differential setting instruction to the controller of the corresponding cross pipe dynamic differential pressure balancing valve 3 through the wireless communication module.

[0075] The cross pipe differential pressure controller 2 determines the most unfavorable terminal device based on the same set of terminal device data:

[0076] For the feedback data from the fan coil terminals of the same group, the thermal comprehensive index of each fan coil terminal is calculated by weighting the temperature and temperature change. The terminal with the highest thermal comprehensive index is the most unfavorable terminal. The temperature change is the difference between the current temperature value and the temperature value at the previous sampling time. The thermal comprehensive index is calculated according to the following formula:

[0077] I k =(t k +g k1 Δt k )γ k2 , k∈n (1)

[0078]

[0079] Where k is the fan coil terminal number, tk is the room temperature where the fan coil is located, Δt k is the temperature change of the room, γ k1 is the temperature change weighting coefficient, γ k2 k is the weighted coefficient of room importance, which is determined based on experience and is 1.0 in the present invention. max It is the number of the fan coil end with the highest comprehensive thermal index in the cross-duct system. The fan coil end with this number represents the most unfavorable end of the cross-duct system.

[0080] The cross-pipe differential pressure controller 2 generates a differential pressure setting instruction for the cross-pipe dynamic differential pressure balancing valve 3 according to the thermal comprehensive index of the most unfavorable terminal equipment, and its setting rule is:

[0081] p h =k p (I max / γ max -I 0,max )+k I ∫(I max / γ max -I 0,max )dt (3)

[0082] Where k p is the proportionality constant, k I is the integration constant, I max / γ max I is the most unfavorable thermal comprehensive index of the terminal equipment without considering the weighted coefficient of room importance, 0,max It is the set value of the most unfavorable terminal equipment thermal comprehensive index. Reaching this value means that the thermal comfort of the room where the most unfavorable terminal equipment is located has reached the acceptable upper limit.

[0083] The control logic of the cross-pipe pressure difference controller 2 is to maximize the opening frequency of the most unfavorable fan coil end while ensuring thermal comfort, so as to reduce the comprehensive resistance coefficient of the cross-pipe system.

[0084] 2.2 Operation steps of horizontal pipe dynamic pressure differential balancing valve 3

[0085] The cross-pipe dynamic differential pressure balancing valve 3 controls its valve position opening according to the differential pressure setting so that the cross-pipe differential pressure is maintained within the differential pressure setting range.

[0086] Each cross pipe dynamic differential pressure balancing valve 3 is connected to a wireless communication module, such as a Wi-Fi module, through a microcontroller MCU to transmit data to the riser differential pressure controller 4. The transmitted information is the valve position opening of the cross pipe dynamic differential pressure balancing valve 3.

[0087] The horizontal pipe dynamic pressure differential balancing valves 3 connected to the same riser system are regarded as the same group of valve positions.

[0088] 3 Operation steps of the riser system

[0089] 3.1 Operation steps of the riser pressure differential controller 4

[0090] The riser pressure differential controller 4 is implemented on the cloud platform. The cloud platform receives, stores and processes the valve position data sent from each cross pipe dynamic pressure differential balancing valve 3. Based on the same set of valve position data, the most unfavorable cross pipe system is determined, and the corresponding riser dynamic pressure differential balancing valve 5 (i.e., the riser system where the most unfavorable cross pipe system is located) pressure differential setting instructions are generated. The cloud platform returns the pressure differential setting instructions to the controller of the corresponding riser dynamic pressure differential balancing valve 5 through the wireless communication module.

[0091] The riser pressure differential controller 4 determines the most unfavorable cross pipe system according to the valve position data of the same group of cross pipe dynamic pressure differential balancing valves 3: the cross pipe system where the cross pipe dynamic pressure differential balancing valve 3 with the largest valve position opening is located is the most unfavorable cross pipe system.

[0092] The riser pressure differential controller 4 generates a pressure differential setting instruction for the riser dynamic pressure differential balancing valve 5 according to the valve position opening of the most unfavorable cross pipe system, and its setting rule is:

[0093] p l =k p,h (y h,max -y h,0 )+k I,h ∫(y h,max -y h,0 )dt (4)

[0094] In the formula, y h,max is the valve position of the cross pipe dynamic pressure difference balancing valve 3 in the most unfavorable cross pipe system, y h,0 is the valve position setting value of the cross pipe dynamic differential pressure balancing valve 3 of the most unfavorable cross pipe system. Reaching this value means that the valve position of the cross pipe dynamic differential pressure balancing valve 3 of the most unfavorable cross pipe system is almost fully open.

[0095] The control logic of the riser pressure difference controller 4 is to make the valve position of the cross pipe dynamic pressure difference balancing valve 3 in the most unfavorable cross pipe system as fully open as possible to reduce the comprehensive resistance coefficient of the riser system.

[0096] 3.2 Operation steps of the vertical pipe dynamic pressure differential balancing valve 5

[0097] The riser dynamic differential pressure balancing valve 5 controls its valve position opening according to the differential pressure setting so that the riser differential pressure is maintained within the differential pressure setting range.

[0098] Each riser dynamic differential pressure balancing valve 5 is connected to a wireless communication module, such as a Wi-Fi module, through a microcontroller MCU to transmit data to the main pipe differential pressure controller 6. The transmitted information is the valve position opening of the riser dynamic differential pressure balancing valve 5.

[0099] 4 Operation steps of the main pipe system

[0100] 4.1 Operation steps of dry pipe differential pressure controller 6

[0101] The main pipe pressure difference controller 6 is implemented on the cloud platform. The cloud platform receives, stores and processes the valve position data sent from each riser dynamic pressure difference balancing valve 5. Based on the valve position data, the most unfavorable riser system is determined and a main pipe pressure difference setting instruction is generated. The cloud platform returns the pressure difference setting instruction to the variable frequency water pump 7 through the wireless communication module.

[0102] The main pipe differential pressure controller 6 determines the most unfavorable riser system according to the valve position data of the riser dynamic differential pressure balancing valve 5 : the riser system where the riser dynamic differential pressure balancing valve 5 with the largest valve position opening is located is the most unfavorable riser system.

[0103] The main pipe pressure difference controller 6 generates a main pipe pressure difference setting instruction according to the valve position opening of the most unfavorable riser system, and its setting rule is:

[0104] p g =k p,l (y l,max -y l,0 )+k l,I ∫(y l,max -y l,0 )dt (5)

[0105] In the formula, y l,max The most unfavorable riser system dynamic pressure differential balancing valve 5 valve position, y l,0 It is the valve position setting value of the riser dynamic pressure differential balancing valve 5 of the most unfavorable riser system. Reaching this value means that the valve position of the riser dynamic pressure differential balancing valve 5 of the most unfavorable riser system is almost fully open.

[0106] The control logic of the main pipe pressure difference controller 6 is to make the valve position of the riser dynamic pressure difference balancing valve 5 of the most unfavorable riser system as fully open as possible to reduce the comprehensive resistance coefficient of the main pipe system.

[0107] 4.2 Operation steps of variable frequency water pump 7

[0108] The controller of the variable frequency water pump 7 controls its frequency according to the main pipe pressure difference setting instruction so that the main pipe pressure difference is maintained within the pressure difference setting range.

[0109] 5. Sampling period setting

[0110] In order to achieve local control as much as possible, the cycle setting principle involved in the control system is: fan coil data acquisition cycle < pressure difference instruction setting cycle of horizontal pipe pressure difference controller 2 < pressure difference instruction setting cycle of vertical pipe pressure difference controller 4 < pressure difference instruction setting cycle of main pipe pressure difference controller 6.

[0111] experiment:

[0112] The simulation calculation of the variable flow chilled water system and method of the air conditioner with multi-stage pressure difference reset of the present invention is implemented, and the parameters are shown in Table 1. The variable flow chilled water system of the air conditioner with multi-stage pressure difference reset has 4 parallel riser systems, each riser system has 6 parallel transverse pipe systems, and each transverse pipe system is connected to 10 parallel fan coil ends (branch system 1). The design resistance of each branch system 1 (fan coil end) is 33kpa, the branch design resistance between each branch system 1 on the transverse pipe (cross pipe branch design resistance) is 4kpa, and the design resistance of the cross pipe dynamic pressure difference balancing valve when it is fully opened is 10kpa. The branch design resistance between each cross pipe system on the riser is 4kpa (riser branch design resistance), and the design resistance of the riser dynamic pressure difference balancing valve when it is fully opened is 10kpa. The branch design resistance between each riser system (main pipe branch design resistance) is 10kpa. Taking the water distribution energy consumption (proportional to the product of the main pipe set pressure difference and the water volume) under the design working condition (load rate is 1), the water volume, the main pipe set pressure difference and the cold water delivery coefficient as the comparison benchmark (their values ​​are all set to 1), when the load rate (the ratio of load to design load) of each terminal is 70%, the delivery flow, main pipe set pressure difference, water delivery energy consumption and cold water delivery coefficient of the main pipe pressure difference control method are 0.82, 1, 0.82 and 1.22 respectively, the results of the terminal pressure difference control method are 0.7, 0.728, 0.51 and 1.96 respectively, and the results of the multi-stage pressure difference re-management method (the present invention) are 0.425, 0.207, 0.088 and 11.36 respectively. It can be seen that the water transportation energy consumption of the present invention is much smaller than the water transportation energy consumption corresponding to the main pipe pressure difference control method and the terminal control method, and the cold water transportation coefficient is much larger than the former two. This is because the present invention can achieve the matching of water volume and load by adjusting the dynamic pressure difference balancing valve of the horizontal pipe and the dynamic pressure difference balancing valve of the vertical pipe, while ensuring the hydraulic balance of the water system. Therefore, it can save the energy consumption of cold water transportation and improve the cold water transportation coefficient, effectively realizing the original intention of the present invention.

[0113] Table 1 Comparison of results between the present invention and on-off control

[0114]

[0115]

[0116] The design parameters of the system can be reasonably determined by comprehensively considering specific usage conditions and requirements, technical and economic performance and other factors to take into account both the applicability and economy of the system.

[0117] Finally, it should be noted that the above examples are only some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. An air conditioning variable flow chilled water system with multi-stage pressure difference reset, characterized in that: It comprises a water supply main pipe on the user side, a return water main pipe, at least one riser system, a variable frequency water pump (7), a microcontroller MCU and a control unit on the network side, wherein the riser system is arranged in parallel between the water supply main pipe and the return water main pipe, and the variable frequency water pump (7) is arranged at the input end of the water supply main pipe; The riser system and the variable frequency water pump (7) are both connected to the microcontroller MCU by signal, and the microcontroller MCU is connected to the control unit by signal via a wireless communication module.

2. The air conditioning variable flow chilled water system with multi-stage pressure difference reset according to claim 1, characterized in that: The riser system comprises a water supply riser and a water return riser, the water supply riser is connected to a water supply main pipe, the water return riser is connected to a water return main pipe, a riser dynamic pressure difference balancing valve (5) is arranged at the input end of the water supply riser, and at least one horizontal pipe system is arranged in parallel between the water supply riser and the water return riser.

3. The air conditioning variable flow chilled water system with multi-stage pressure difference reset according to claim 2, characterized in that: The horizontal pipe system comprises a water supply horizontal pipe and a water return horizontal pipe, the water supply horizontal pipe is connected to the water supply vertical pipe, the water return horizontal pipe is connected to the water return vertical pipe, a horizontal pipe dynamic pressure difference balancing valve (3) is arranged at the input end of the water supply horizontal pipe, and at least one branch pipe system (1) is arranged in parallel between the water supply horizontal pipe and the water return horizontal pipe.

4. The air conditioning variable flow chilled water system with multi-stage pressure difference reset according to claim 3, characterized in that: The branch pipe system (1) comprises a water supply branch pipe and a water return branch pipe, wherein the water supply branch pipe is connected to the water supply horizontal pipe, and the water supply branch pipe is connected to the water return horizontal pipe after passing through an on-off valve, a fan coil unit and a water return branch pipe.

5. The air conditioning variable flow chilled water system with multi-stage pressure difference reset according to claim 4, characterized in that: The control unit comprises a main pipe differential pressure controller (6), a riser differential pressure controller (4) and a cross pipe differential pressure controller (2); the fan coil unit, the cross pipe dynamic differential pressure balancing valve (3), the riser dynamic differential pressure balancing valve (5) and the variable frequency water pump (7) are all connected to the microcontroller MCU by signal, and the microcontroller MCU is connected to the main pipe differential pressure controller (6), the riser differential pressure controller (4), the cross pipe differential pressure controller (2) and the variable frequency water pump (7) by signal through a wireless communication module.

6. A control method for an air-conditioning variable flow chilled water system with multi-stage pressure difference reset as claimed in any one of claims 1 to 5, characterized in that: S1. Operation of branch pipe system (1): Each fan coil unit collects data and transmits it to the cross-pipe differential pressure controller (2), including room temperature, set room temperature and the on / off status of the on / off valve; S2. Operation of the cross pipe system: The cross pipe differential pressure controller (2) selects the most unfavorable terminal device according to the same group of terminal device data, generates a differential pressure setting instruction, and sends it to the cross pipe dynamic differential pressure balancing valve (3) in the branch pipe system (1) where the most unfavorable terminal device is located, to control the valve position opening; Each horizontal pipe dynamic differential pressure balancing valve (3) transmits valve position opening data to a vertical pipe differential pressure controller (4); S3. Operation of the riser system The riser pressure differential controller (4) determines the most unfavorable cross pipe system from the valve position data sent by each cross pipe dynamic pressure differential balancing valve (3) based on the same set of valve position data, and generates a pressure differential setting instruction, which is sent to the riser dynamic pressure differential balancing valve (5) in the riser system where the most unfavorable cross pipe system is located, to control the valve position opening; Each riser dynamic differential pressure balancing valve (5) transmits valve position opening information to the main pipe differential pressure controller (6); S4. Operation of the main pipe system The main pipe pressure difference controller (6) determines the most unfavorable riser system from the valve position data sent by each riser dynamic pressure difference balancing valve (5), and generates a main pipe pressure difference setting instruction and sends it to the variable frequency water pump (7); the variable frequency water pump (7) controls the operating frequency according to the main pipe pressure difference setting instruction.

7. The control method of a variable flow chilled water system of an air conditioner with multi-stage pressure difference reset according to claim 6, characterized in that: The judgment rule of the most unfavorable terminal device is: For the feedback data of the fan coil units in the same group, the thermal comprehensive index of each fan coil unit terminal is calculated by weighting the temperature and temperature change. The terminal device with the highest thermal comprehensive index is the most unfavorable terminal device. The thermal comprehensive index is: I k =(t k +g k1 Δt k )γ k2 , k∈n (1) Where k is the fan coil terminal number, t k is the room temperature where the fan coil is located, Δt k is the temperature change of the room, γ k1 is the temperature change weighting coefficient, γ k2 is the room importance weighting coefficient, k max The number of the fan coil end with the highest comprehensive thermal index in the horizontal pipe system; The setting rule of the pressure difference setting instruction of the cross-pipe dynamic pressure difference balancing valve (3) is: p h =k p (I max / γ max -I 0,max )+k I ∫(I max / γ max -I 0,max )dt (3) Where k p is the proportionality constant, k I is the integration constant, I max / γ max I is the most unfavorable thermal comprehensive index of the terminal equipment without considering the weighted coefficient of room importance, 0,max It is the setting value of the most unfavorable comprehensive thermal index of the terminal equipment.

8. The control method of a variable flow chilled water system for air conditioning with multi-stage pressure difference reset according to claim 7, characterized in that: The most unfavorable cross pipe system is determined by the following rule: the cross pipe system where the cross pipe dynamic pressure difference balancing valve (3) with the largest valve position opening is located is the most unfavorable cross pipe system; The setting rule of the pressure difference setting instruction of the riser dynamic pressure difference balancing valve (5) is: p l =k p,h (y h,max -y h,0 )+k I,h ∫(y h,max -y h,0 )dt (4) In the formula, y h,max is the valve position of the cross pipe dynamic pressure differential balancing valve (3) in the most unfavorable cross pipe system, y h,0 It is the valve position setting value of the cross pipe dynamic differential pressure balancing valve (3) of the most unfavorable cross pipe system.

9. The control method of a variable flow chilled water system for air conditioning with multi-stage pressure difference reset according to claim 8, characterized in that: The judgment rule of the most unfavorable riser system is: the riser system where the riser dynamic pressure difference balancing valve (5) with the largest valve position opening is located is the most unfavorable riser system; The setting rules of the main pipe pressure difference setting instruction are: p g =k p,l (y l,max -y l,0 )+k l,I ∫(y l,max -y l,0 )dt (5) In the formula, y l,max is the valve position of the dynamic differential pressure balance valve (5) of the most unfavorable riser system, y l,0 It is the valve position setting value of the riser dynamic differential pressure balancing valve (5) of the most unfavorable riser system.

10. The control method of a variable flow chilled water system of an air conditioner with multi-stage pressure difference reset according to claim 9, characterized in that: The fan coil unit data collection period is less than the pressure difference instruction setting period of the horizontal pipe pressure difference controller (2) and less than the pressure difference instruction setting period of the vertical pipe pressure difference controller (4) and less than the pressure difference instruction setting period of the main pipe pressure difference controller (6).

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