Multi-stage differential pressure reset air conditioning variable flow chilled water system and method

Abstract

The application relates to the technical field of air conditioner control, and discloses a multi-stage pressure difference reset air conditioner variable flow cold water system, which comprises 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; the riser system and the variable frequency water pump are signal-connected with the microcontroller MCU, and the microcontroller MCU is signal-connected with the control unit through a wireless communication module. The application also simultaneously provides a control method of the multi-stage pressure difference reset air conditioner variable flow cold water system. Through the multi-stage pressure difference reset, the application can adapt to the load through cold quantity adjustment, can dynamically carry out hydraulic balance according to actual conditions, can guarantee required flow, can minimize the water pump inlet and outlet pressure difference as much as possible, and can improve water system energy-saving capacity.

Description

Technical Field

[0001] This invention belongs to the field of air conditioning control technology, specifically relating to a multi-stage differential pressure reset air conditioning variable flow chilled water system and method. Background Technology

[0002] On / off control fan coil systems are widely used in my country's building air conditioning industry. Because the selection of equipment in its chilled water system, such as pumps and fan coil units, is based on the most unfavorable operating conditions under design conditions, while in actual operation, non-design conditions often occupy the majority of the operating time, thus providing considerable room for variable water volume energy-saving operation of the system.

[0003] Currently, the variable water volume control methods used in on / off control fan coil air conditioning systems mainly include the main pipe differential pressure control method and the terminal differential pressure control method. The purpose is to achieve variable water volume energy saving while ensuring the design available pressure head. Among them, the energy saving effect of the terminal differential pressure control method is better than that of the main pipe differential pressure control method. Taking the terminal differential pressure control method as an example, when the load decreases, the frequency of closing the on / off control valve of the fan coil unit in the system increases (the opening rate decreases), which increases the differential pressure at the terminal of the differential pressure control. This indicates that the flow rate through the fan coil unit exceeds the design flow rate. This differential pressure signal is fed back to the variable frequency water pump. By reducing the frequency and the pump head, the differential pressure at the control terminal decreases again and stabilizes near the set value, thereby avoiding the occurrence of overflow at the system terminal and reducing "unnecessary" flow waste. In this way, while ensuring that the flow rate through the fan coil unit is the design flow rate, its adaptability to load changes is actually adjusted by the opening rate of the fan coil unit. One problem with this control method is that it does not adapt to load changes by reducing the flow rate of the fan coil unit, i.e., by adjusting the cooling capacity, and the energy-saving potential of the water system is not fully explored. For example, the invention "Method and System for Quality Control of Central Air Conditioning Chilled Water Station" (publication number CN200710118464.2) uses constant differential pressure control based on the terminal pressure difference at a certain point in the chilled water supply network. When the load decreases to 70%, the flow rate decreases to 60%. This near-synchronous decrease is a key characteristic of on-time regulation. Although the flow rate decreases with the load, achieving the purpose of variable flow, it fails to utilize the characteristic that the fan coil unit's flow rate decreases faster than the cooling capacity for load adaptation, thus relatively reducing energy-saving effects. Another problem is that the system's hydraulic balance is generally only for the design conditions; under partial load conditions, it is not balanced, easily leading to "overflow." Therefore, considering the above two problems, it is necessary to propose a variable flow system and control method for on-off control of fan coil units. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a multi-stage differential pressure reset air conditioning variable flow chilled water system and method, so that the chilled water system can provide water delivery that adapts to partial load conditions, thereby achieving greater variable water volume energy saving effect and improving the energy saving of the system's water system.

[0005] To solve the above-mentioned technical problems, the present invention provides a multi-stage differential pressure reset air conditioning variable flow chilled water system, including a user-side water supply main pipe, a return main pipe, at least one riser system, a variable frequency water pump, a microcontroller MCU and a network-side control unit. The riser system is arranged in parallel between the water supply main pipe and the return main pipe, and the variable frequency water pump is located at the input end of the water supply main pipe.

[0006] Both the riser system and the variable frequency water pump are connected to the microcontroller (MCU) via signal transmission. The MCU is connected to the control unit via a wireless communication module.

[0007] An improvement to the multi-stage differential pressure reset air conditioning variable flow chilled water system 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. A riser dynamic differential pressure balancing valve is installed at the input end of the water supply riser. At least one horizontal pipe system is installed in parallel between the water supply riser and the return riser.

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

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

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

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

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

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

[0015] This invention also provides a control method for an air conditioning variable flow chilled water system utilizing a multi-stage differential pressure resetting mechanism, comprising:

[0016] S1. Operation of the branch piping system:

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

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

[0019] The horizontal pipe differential pressure controller selects the most unfavorable terminal device based on the same set of terminal device data, generates a differential pressure setting command, and sends it to the horizontal pipe dynamic differential pressure balancing valve in the branch pipe system where the most unfavorable terminal device is located to control the valve opening.

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

[0021] S3, Operation of the riser system

[0022] The riser differential pressure controller obtains valve position data from each horizontal pipe dynamic differential pressure balancing valve, determines the most unfavorable horizontal pipe system based on the same set of valve position data, generates a differential pressure setting command, and sends it to the riser dynamic differential pressure balancing valve in the riser system where the most unfavorable horizontal pipe system is located to control the valve opening.

[0023] Each riser's dynamic differential pressure balancing valve transmits its valve position opening information to the main pipeline differential pressure controller;

[0024] S4. Operation of the main pipeline system

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

[0026] An improvement to the control method of a multi-stage differential pressure reset air conditioning variable flow chilled water system according to the present invention:

[0027] The rule for determining the most unfavorable terminal device is:

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

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

[0030]

[0031] In the formula, k is the terminal number of the fan coil unit, and t k The room temperature where the fan coil unit is located, Δt k For the temperature change of room temperature, γ k1 γ is the temperature variation weighting coefficient. k2 k is a weighting coefficient for the importance of the room. max This is the number of the end unit of the fan coil unit with the highest overall thermal performance in this horizontal tube system;

[0032] The setting rules for the differential pressure setting command of the horizontal pipe dynamic differential pressure balancing valve (3) are as follows:

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

[0034] In the formula k p k is a proportionality constant. I I is the integration constant. max / γ max The thermal comprehensive index of the most unfavorable terminal equipment without considering the room importance weighting factor, I 0,max This is the set value for the comprehensive thermal index of the most unfavorable terminal equipment.

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

[0036] The rule for determining the most unfavorable horizontal pipe system is: the horizontal pipe system in which the horizontal pipe dynamic differential pressure balancing valve (3) with the largest valve position opening is located is the most unfavorable horizontal pipe system;

[0037] The setting rules for the differential pressure setting command of the riser dynamic differential pressure balancing valve (5) are as follows:

[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,maxFor the valve position of the dynamic differential pressure balancing valve (3) in the most unfavorable horizontal pipe system, y h,0 The valve position setting value for the dynamic differential pressure balancing valve of the horizontal pipe system in the most unfavorable horizontal pipe system.

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

[0041] The rule for determining the most unfavorable riser system is: the riser system where the riser dynamic differential pressure balancing valve with the largest valve opening is located is the most unfavorable riser system.

[0042] The setting rules for the differential pressure setting command for the main pipeline are as follows:

[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 For the most unfavorable riser system, the riser dynamic differential pressure balancing valve position is y. l,0 The valve position setting value for the riser dynamic differential pressure balancing valve of the most unfavorable riser system.

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

[0046] The data acquisition cycle of the fan coil unit is less than the differential pressure command setting cycle of the horizontal pipe differential pressure controller, which is less than the differential pressure command setting cycle of the vertical pipe differential pressure controller, which is less than the differential pressure command setting cycle of the main pipe differential pressure controller.

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

[0048] This invention achieves hydraulic balance in the chilled water system by resetting multi-stage pressure differentials, thereby saving energy consumption in the chilled water system's transmission and distribution.

[0049] This invention adapts to the load by adjusting the cooling capacity, and can perform dynamic hydraulic balance according to the actual situation. It ensures the required flow rate while minimizing the pressure difference between the inlet and outlet of the water pump, thereby improving the energy saving of the water system. Under the premise of ensuring that the load requirements are met, it can achieve the minimum water supply of the cooling water system and can dynamically determine the most unfavorable loop according to the actual operating conditions. Attached Figure Description

[0050] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0051] Figure 1This is a schematic diagram of the structure of a multi-stage differential pressure reconfigured air conditioning variable flow chilled water system according to the present invention;

[0052] Figure 2 This is a schematic diagram of the control process of a multi-stage differential pressure reset air conditioning variable flow chilled water system according to the present invention. Detailed Implementation

[0053] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0054] Example 1: A multi-stage differential pressure reset air conditioning variable flow chilled water system, such as... Figure 1 As shown.

[0055] The multi-stage differential pressure reset air conditioning variable flow chilled water system mainly consists of a user-side water supply main pipe, a return main pipe, a riser system, a variable frequency water pump 7, a microcontroller MCU, and a network-side control unit. The variable frequency water pump 7 is located 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 mainly consists of a water supply riser, a return riser, a horizontal pipe system, and a riser dynamic differential pressure balancing valve 5. 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 differential pressure balancing valve 5 is located at the input end of the water supply riser of each riser system. Several horizontal pipe systems are connected in parallel to the water supply riser and the return riser.

[0057] The horizontal pipe system mainly consists of a water supply horizontal pipe, a return horizontal pipe, branch pipe system 1, and a horizontal pipe dynamic differential pressure balancing valve 3. The water supply horizontal pipe is connected to the water supply riser, and the return horizontal pipe is connected to the return riser. The horizontal pipe dynamic differential pressure balancing valve 3 is located 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] Branch system 1 mainly consists of water supply branch pipes, on / off valves, fan coil units, and return water branch pipes. The water supply branch pipes are connected to the water supply horizontal pipes. The water supply branch pipes are connected to the return water horizontal pipes through on / off valves, fan coil units, and return water branch pipes. The feedback signals from the fan coil units are the open / closed status signals of the on / off valves and the room temperature signal.

[0059] Cold water in the main supply pipe flows into the parallel riser systems on the user side via the variable frequency pump 7, and then flows out from the return main pipe. In each riser system, cold water flows in from the supply riser, passes through the riser dynamic differential pressure balancing valve 5, flows into the parallel horizontal pipe systems, and then flows out from the return riser into the return main pipe. In each horizontal pipe system, cold water flows in from the supply horizontal pipe, passes through the horizontal pipe dynamic differential pressure balancing valve 3, flows into the parallel branch pipe systems 1, and then flows out from the return horizontal pipe into the return riser. In each branch pipe system 1, cold water flows in through the supply branch pipe, and then flows into the return horizontal pipe through the on / off valve, fan coil unit, and return branch pipe.

[0060] The control unit includes a main pipe differential pressure controller 6, a riser differential pressure controller 4, and a horizontal pipe differential pressure controller 2. All three controllers are located on a cloud platform, which receives, stores, and processes data from each fan coil unit, horizontal pipe dynamic differential pressure balancing valve 3, riser dynamic differential pressure balancing valve 5, and variable frequency water pump 7. Each of these components is connected to a microcontroller (MCU). The MCU communicates with the main pipe differential pressure controller 6, riser differential pressure controller 4, horizontal pipe differential pressure controller 2, and variable frequency water pump 7 via a wireless communication module, such as a Wi-Fi module. Figure 2 As shown.

[0061] The horizontal pipe differential pressure controller 2 receives feedback signals from each fan coil unit and, after signal analysis, provides the differential pressure setpoint for the horizontal pipe dynamic differential pressure balancing valve 3. The horizontal pipe dynamic differential pressure balancing valve 3 adjusts its opening according to the differential pressure setpoint to maintain the differential pressure between the supply and return horizontal pipes within the set range. The feedback signal from the horizontal pipe dynamic differential pressure balancing valve 3 is its opening degree signal.

[0062] The riser differential pressure controller 4 receives feedback signals from the dynamic differential pressure balancing valves 3 of each horizontal pipe, and after signal analysis, provides the differential pressure setting value for the riser dynamic differential pressure balancing valve 5. The riser dynamic differential pressure balancing valve 5 adjusts the valve opening according to the differential pressure setting value to maintain the differential pressure between the water supply riser and the return riser within the set differential pressure range.

[0063] The main pipe differential pressure controller 6 receives feedback signals from the dynamic differential pressure balancing valves 5 of each riser, and provides the main pipe differential pressure setpoint after signal analysis. The variable frequency water pump 7 adjusts its frequency according to the main pipe differential pressure setpoint to maintain the differential pressure between the water supply riser and the return riser within the set differential pressure range.

[0064] The purpose of setting the pressure of the horizontal pipe differential pressure controller 2 is to minimize the water supply volume of the horizontal pipe while ensuring the room thermal comfort borne by the branch pipe system 1, and at the same time minimize the overall resistance coefficient of the horizontal pipe system.

[0065] The purpose of setting the pressure of the riser differential pressure controller 4 is to minimize the overall resistance coefficient of the riser system.

[0066] The purpose of setting the pressure of the main pipeline differential pressure controller 6 is to minimize the overall resistance coefficient on the user side of the main pipeline system.

[0067] The control method of a multi-stage differential pressure reset air conditioning variable flow chilled water system according to the present invention is as follows:

[0068] Operating steps of branch pipe system 1

[0069] The fan coil units (terminal devices) of branch system 1 control the room temperature according to the local on / off control logic.

[0070] The data signals collected by each fan coil unit are connected to a wireless communication module, such as a Wi-Fi module, via a microcontroller (MCU) to transmit the data to the horizontal 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] End devices connected to the same horizontal pipe system are considered to be in the same group.

[0072] 2. Operation steps of the horizontal pipe system

[0073] 2.1 Operating Procedures of Horizontal Pipe Differential Pressure Controller 2

[0074] Based on the data from the same set of terminal devices, the horizontal pipe differential pressure controller 2 identifies the most unfavorable terminal device and generates a differential pressure setting command for the corresponding horizontal pipe dynamic differential pressure balancing valve 3 (i.e., the branch system 1 where the most unfavorable terminal device is located). The cloud platform then returns this differential pressure setting command to the controller of the corresponding horizontal pipe dynamic differential pressure balancing valve 3 via a wireless communication module.

[0075] The rule for determining the most unfavorable terminal device based on data from the same set of terminal devices is as follows:

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

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

[0078]

[0079] In the formula, k is the terminal number of the fan coil unit, and tk The room temperature where the fan coil unit is located, Δt k For the temperature change of room temperature, γ k1 γ is the temperature variation weighting coefficient. k2 k is a weighting factor for the importance of the room, determined empirically; in this invention, it is 1.0. max This is the number of the fan coil unit terminal with the highest overall thermal performance in the horizontal pipe system. This number represents the most unfavorable terminal in the horizontal pipe system.

[0080] The horizontal pipe differential pressure controller 2 generates a differential pressure setting command for the horizontal pipe dynamic differential pressure balancing valve 3 based on the comprehensive thermal index of the most unfavorable terminal equipment. The setting rules are as follows:

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

[0082] In the formula k p k is a proportionality constant. I I is the integration constant. max / γ max The thermal comprehensive index of the most unfavorable terminal equipment without considering the room importance weighting factor, I 0,max This is the set value for the comprehensive thermal index of the most unfavorable terminal equipment. Reaching this value means that the thermal comfort of the room where the most unfavorable terminal equipment is located has reached the upper limit of acceptable comfort.

[0083] The control logic of the horizontal pipe differential pressure controller 2 is to maximize the opening frequency of the most unfavorable fan coil terminal while ensuring thermal comfort, so as to reduce the overall resistance coefficient of the horizontal pipe system.

[0084] 2.2 Operating Procedures of Horizontal Pipe Dynamic Differential Pressure Balancing Valve 3

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

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

[0087] The horizontal pipe dynamic differential pressure balancing valve 3 connected to the same riser system is considered to be in the same group of valve positions.

[0088] 3. Operation steps of the riser system

[0089] 3.1 Operating Procedures of Riser Differential Pressure Controller 4

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

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

[0092] The riser differential pressure controller 4 generates a differential pressure setting command for the riser dynamic differential pressure balancing valve 5 based on the valve position opening of the most unfavorable horizontal pipe system. The setting rules are as follows:

[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 For the valve position of the dynamic differential pressure balancing valve 3 in the most unfavorable horizontal pipe system, y h,0 The valve position setting value for the dynamic differential pressure balancing valve 3 of the horizontal pipe system in the most unfavorable horizontal pipe system is such that reaching this value means that the valve position of the dynamic differential pressure balancing valve 3 of the horizontal pipe system in the most unfavorable horizontal pipe system is almost fully open.

[0095] The control logic of the riser differential pressure controller 4 is to keep the valve position of the dynamic differential pressure balancing valve 3 in the most unfavorable horizontal pipe system as fully open as possible, so as to reduce the overall resistance coefficient of the riser system.

[0096] 3.2 Operating Procedures of Riser Dynamic Differential Pressure Balancing Valve 5

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

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

[0099] 4. Operation steps of the main pipeline system

[0100] 4.1 Operating Procedures of the Main Pipe Differential Pressure Controller 6

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

[0102] The main pipe differential pressure controller 6 determines the most unfavorable riser system based on the valve position data of the riser dynamic differential pressure balancing valve 5. The rule for determining the most unfavorable riser system is: 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 differential pressure controller 6 generates a main pipe differential pressure setting command based on the valve opening degree of the most unfavorable riser system. The setting rules are as follows:

[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 For the most unfavorable riser system, the riser dynamic differential pressure balancing valve 5 is in position y. l,0 This is the valve position setting value for the dynamic differential pressure balancing valve 5 of the riser system in the most unfavorable riser system. Reaching this value means that the valve position of the dynamic differential pressure balancing valve 5 of the riser system in the most unfavorable riser system is almost fully open.

[0106] The control logic of the main pipe differential pressure controller 6 is to keep the valve position of the riser dynamic differential pressure balancing valve 5 in the most unfavorable riser system as fully open as possible, so as to reduce the overall resistance coefficient of the main pipe system.

[0107] 4.2 Operating Procedures of Variable Frequency Water Pump 7

[0108] The variable frequency water pump 7 has a built-in controller that controls its frequency according to the pressure difference setting command of the main pipe, so that the pressure difference of the main pipe is maintained within the pressure difference setting range.

[0109] 5. Sampling period setting

[0110] To achieve local control as much as possible, the cycle setting principle involved in the control system is as follows: fan coil unit data acquisition cycle < differential pressure command setting cycle of horizontal pipe differential pressure controller 2 < differential pressure command setting cycle of vertical pipe differential pressure controller 4 < differential pressure command setting cycle of main pipe differential pressure controller 6.

[0111] experiment:

[0112] Simulation calculations were performed on a multi-stage differential pressure resetting air conditioning variable flow chilled water system and method according to the present invention. The parameters are shown in Table 1. The multi-stage differential pressure resetting air conditioning variable flow chilled water system has four parallel riser systems, each riser system has six parallel horizontal pipe systems, and each horizontal pipe system is connected to ten parallel fan coil unit terminals (branch system 1). The design resistance of each branch system 1 (fan coil unit terminal) is 33 kPa. The design resistance of the branch between each branch system 1 on the horizontal pipe (horizontal pipe branch design resistance) is 4 kPa, and the design resistance of the horizontal pipe dynamic differential pressure balancing valve when fully open is 10 kPa. The design resistance of the branch between each horizontal pipe system on the riser is 4 kPa (riser branch design resistance), and the design resistance of the riser dynamic differential pressure balancing valve when fully open is 10 kPa. The design resistance of the branch between each riser system (main pipe branch design resistance) is 10 kPa. Using the water distribution energy consumption (proportional to the product of the main pipe set pressure difference and the water volume) under the design conditions (load rate of 1), the water volume, the main pipe set pressure difference, and the cold water delivery coefficient as comparison benchmarks (all values ​​are set to 1), when the load rate (the ratio of load to design load) of each terminal is 70%, the delivery flow rate, main pipe set pressure difference, water distribution 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-method (this invention) are 0.425, 0.207, 0.088, and 11.36, respectively. It is evident that the water transport energy consumption of this invention is far less than that of the main pipe differential pressure control method and the terminal control method, and the cold water transport coefficient is far greater than the former two. This is because this invention can achieve the matching of water volume and load by adjusting the dynamic differential pressure balancing valve of the horizontal pipe and the dynamic differential pressure balancing valve of the vertical pipe, while ensuring the hydraulic balance of the water system. Therefore, it can save cold water transport energy consumption and improve the cold water transport coefficient, effectively realizing the original intention of this 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, etc., so as to balance the applicability and economy of the system.

[0117] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A multi-stage differential pressure reset air conditioning variable flow chilled water system, characterized in that: The system comprises a water supply main pipe, 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, the riser system is connected 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 signal connected with the microcontroller MCU, and the microcontroller MCU is signal connected with the control unit through a wireless communication module. The riser system comprises a water supply riser and a return water riser, the water supply riser is connected with the water supply main pipe, the return water riser is connected with the return water main pipe, a riser dynamic pressure difference balance valve (5) is arranged at the input end of the water supply riser, and at least one cross pipe system is connected in parallel between the water supply riser and the return water riser. The cross pipe system comprises a water supply cross pipe and a return water cross pipe, the water supply cross pipe is connected with the water supply riser, the return water cross pipe is connected with the return water riser, a cross pipe dynamic pressure difference balance valve (3) is arranged at the input end of the water supply cross pipe, and at least one branch pipe system (1) is connected in parallel between the water supply cross pipe and the return water cross pipe. The control unit comprises a main pipe pressure difference controller (6), a riser pressure difference controller (4) and a cross pipe pressure difference controller (2), the fan coil, the cross pipe dynamic pressure difference balance valve (3), the riser dynamic pressure difference balance valve (5) and the variable frequency water pump (7) are signal connected with the microcontroller MCU, and the microcontroller MCU is signal connected with the main pipe pressure difference controller (6), the riser pressure difference controller (4), the cross pipe pressure difference controller (2) and the variable frequency water pump (7) through the wireless communication module.

2. The multi-stage pressure difference reconfigured air conditioning variable flow cold water system according to claim 1, characterized in that: The branch pipe system (1) comprises a water supply branch pipe and a return water branch pipe, the water supply branch pipe is connected with the water supply cross pipe, and the water supply branch pipe is connected with the return water cross pipe through an on-off valve, a fan coil and a return water branch pipe.

3. The control method of the multi-stage pressure difference reconfigured air conditioning variable flow cold water system according to claim 2, characterized in that: S1, operation of the branch pipe system (1): Each fan coil collects data and transmits the data to the cross pipe pressure difference controller (2), including room temperature, set room temperature and on-off state of the on-off valve; S2, operation of the cross pipe system: The cross pipe pressure difference controller (2) selects the most unfavorable terminal equipment according to the same group of terminal equipment data, generates a pressure difference setting instruction, and sends the pressure difference setting instruction to the cross pipe dynamic pressure difference balance valve (3) in the branch pipe system (1) where the most unfavorable terminal equipment is located, to control the valve opening degree; Each cross pipe dynamic pressure difference balance valve (3) transmits the valve opening degree data to the riser pressure difference controller (4); The judgment rule of the most unfavorable terminal equipment is: For the same group of fan coil terminal feedback data, the heat comprehensive index of each fan coil terminal is calculated according to temperature and temperature change weighting, and the fan coil terminal with the highest heat comprehensive index is the most unfavorable terminal equipment, and the heat comprehensive index is: I k = (t k + γ k1 Δt k )γ k2 , k∈n (1) where k is the number of the fan-coil terminal, t k is the temperature of the room 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 is the number of the fan-coil terminal with the highest heat comprehensive index in the cross-pipe system; The setting rule of the pressure difference setting instruction of the cross pipe dynamic pressure difference balance 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 a proportionality constant, k I is an integration constant, I max / γ max is the thermal overall index of the most disadvantaged end device, I 0,max is the set value of the thermal overall index of the most disadvantaged end device; S3, operation of the riser system The riser differential pressure controller (4) determines the most unfavorable horizontal pipe system from the valve position data sent by each horizontal pipe dynamic differential pressure balance valve (3) according to the same group of valve position data, generates a differential pressure setting instruction, and sends it to the riser dynamic differential pressure balance valve (5) in the riser system where the most unfavorable horizontal pipe system is located, to control the valve opening degree; The judgment rule of the most unfavorable horizontal pipe system is that the horizontal pipe system where the horizontal pipe dynamic differential pressure balance valve (3) with the largest valve opening degree is located is the most unfavorable horizontal pipe system; The setting rule of the differential pressure setting instruction of the riser dynamic differential pressure balance valve (5) is that the valve opening degree of the riser dynamic differential pressure balance valve (5) in the most unfavorable horizontal pipe system is the largest; p l = k p,h (y h,max -y h,0 )+k I,h ∫(y h,max -y h,0 )dt (4) where y h,max is the valve position of the cross pipe dynamic pressure difference balance valve (3) in the most unfavorable cross pipe system, y h,0 is the valve position setting value of the cross pipe dynamic pressure difference balance valve (3) of the most unfavorable cross pipe system; Each riser dynamic differential pressure balance valve (5) transmits valve opening degree information to the dry pipe differential pressure controller (6); S4, operation of the dry pipe system The dry pipe differential pressure controller (6) determines the most unfavorable riser system from the valve position data sent by each riser dynamic differential pressure balance valve (5), generates a dry pipe differential pressure setting instruction, and sends it to the variable frequency water pump (7); the variable frequency water pump (7) controls the operation frequency according to the dry pipe differential pressure setting instruction; The judgment rule of the most unfavorable riser system is that the riser system where the riser dynamic differential pressure balance valve (5) with the largest valve opening degree is located is the most unfavorable riser system; The setting rule of the dry pipe differential pressure setting instruction is that the valve opening degree of the riser dynamic differential pressure balance valve (5) in the most unfavorable horizontal pipe system is the largest. p g = k p,l (y l,max -y l,0 )+k l,I ∫(y l,max -y l,0 )dt (5) where y l,max is the riser dynamic pressure differential equalizing valve (5) valve position for the most disadvantaged riser system, y l,0 is the riser dynamic pressure differential equalizing valve (5) valve position set value for the most disadvantaged riser system.

4. The control method of the multi-stage differential pressure reset variable flow cold water system of the air conditioner according to claim 3, characterized in that: The fan coil data acquisition period < the differential pressure instruction setting period of the horizontal pipe differential pressure controller (2) < the differential pressure instruction setting period of the riser differential pressure controller (4) < the differential pressure instruction setting period of the dry pipe differential pressure controller (6).

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