An energy-saving pressure-independent air conditioning pump valve control method and system

Abstract

This invention provides an energy-saving, pressure-independent air conditioning pump valve control method and system, comprising the following steps: S101. Matching the opening values ​​among the effective valves, and setting the valve with the largest opening value as the target valve; S102. If the target valve's position is lower than a first threshold and the target valve shows a tendency to continue closing, then reducing the operating frequency of the air conditioning pump; S103. If the target valve's position is higher than a second threshold and the target valve shows a tendency to continue opening, then increasing the operating frequency of the air conditioning pump; the first threshold is less than the second threshold. This invention collects valve opening values ​​and determines the control scheme for the air conditioning pump by comparing the changes in the opening values ​​of each valve. Compared with traditional water pump frequency conversion control methods, it is more energy-efficient and simpler and more practical to control.

Description

Technical Field

[0001] This invention belongs to the field of building energy conservation technology. The invention relates to an energy-saving control method and system for pump frequency and valve position when a variable flow rate chiller unit is used in a variable flow rate air conditioning primary pump system. Background Technology

[0002] Currently, variable flow chilled water systems with primary pumps are widely used in public buildings. However, when using variable flow chillers, there are many methods for pump frequency conversion control technology. The most common methods are temperature difference control, pressure difference control, and minimum resistance control. Temperature difference control is a method that maintains the supply and return water temperature difference at a certain value. The controller obtains the temperature difference between the supply and return water pipes, compares it with the set value, and then sets a reasonable pump frequency to ensure the flow rate meets the load requirements and the temperature difference returns to the set value. The advantage of temperature difference control is that the system impedance remains constant, and the pump can maximize energy savings. However, it has drawbacks such as susceptibility to hydraulic imbalance, lag response, and insensitivity to pressure changes leading to insufficient pressure difference in some branches. Therefore, it cannot be widely used and is more suitable for small systems with similar functions and smaller scale, such as shopping malls, stadiums, and supermarkets.

[0003] Differential pressure control is a method of controlling the pump frequency by using the pressure difference between the supply and return water in an air conditioning system. Depending on the location of the pressure difference adjustment, it is divided into two methods: main supply and return water differential pressure control and most unfavorable terminal differential pressure control. Currently, the most widely used method in single-stage pump variable flow systems is main supply and return water differential pressure control. When the room load decreases, the terminal valve is adjusted to a smaller value, causing the main system differential pressure to increase. The control system then reduces the pump frequency, thus reducing the flow rate and maintaining the differential pressure at the set value. When the room load increases, the terminal valve is adjusted to a larger value, causing the differential pressure to decrease. The pump frequency is then increased, maintaining a constant differential pressure. The advantages of differential pressure control are fewer influencing factors, faster response, and no lag. However, differential pressure control also suffers from wasted flow at the terminal, resulting in less significant energy savings. The differential pressure setpoint for main pipe constant differential pressure control is a theoretical value derived from calculations based on the resistance of the most unfavorable loop under full load and most unfavorable pipeline valve opening conditions. In actual operation, the system operates under partial load for most of the time, resulting in reduced actual flow and decreased overall system pipeline resistance. To maintain a constant pressure difference between the supply and return water mains, the opening of the end regulating valves must be reduced to increase the system resistance on the load side. This leads to significant static pressure consumption at the end valves, severely limiting the energy savings of the variable frequency pump. Secondly, the theoretically selected most unfavorable loop may become a different branch due to some end-users not needing to open or load changes, causing a larger deviation between the pressure difference setpoint and actual demand, resulting in more severe static pressure consumption at the valves and even worse pump energy efficiency. To overcome these shortcomings, some projects have adopted a most unfavorable end-point constant pressure difference control method. This method selects the most unfavorable loop by detecting and comparing the pressure differences of multiple end branches. Similar to the main pipe constant pressure difference control principle, the pump frequency is controlled by comparing the detected pressure difference value of the most unfavorable loop with the theoretical value. To maintain a constant static pressure difference before and after the end branch of the most unfavorable loop, the opening of the end regulating valves must be reduced to increase the system resistance of that end branch. Compared with the main pipe constant pressure differential control, since the terminal valve does not need to maintain a constant resistance of the entire load-side pipeline, the reduced closing amplitude of the terminal valve reduces static pressure consumption, thus improving the system's energy-saving effect to a certain extent. However, the head provided by the water pump is still greater than the actual requirement, so there is still room for further improvement in its energy-saving effect.

[0004] Minimum resistance control, also known as valve position control, regulates the frequency of the circulating water pump based on the opening degree of the regulating valves at the end of the air conditioning unit, ensuring that at least one of these valves is fully open or nearly fully open. Minimum resistance control always ensures that the valve opening is at its maximum, reducing system pressure loss and minimizing pump energy consumption, making it more energy-efficient than temperature difference control and pressure difference control.

[0005] A common minimum resistance control method involves using a Building Automation (BA) system to statistically analyze the average opening value of water valves within the system. The pressure difference between the average valve opening feedback value and the valve position setpoint is used to set the pressure difference between the chilled water supply and return main pipes or terminal branch pipes. This difference is then compared to the currently measured supply and return water pressure difference to control the pump frequency. From a control principle perspective, minimum resistance control controls the pump frequency through valve positions, which is not directly related to the system's supply and return water pressure difference. This method requires converting the supply and return water pressure difference for control, resulting in complex system control logic; it is essentially a variable pressure difference control method. Secondly, the minimum resistance control method sets the differential pressure setpoint based on the valve positions of each regulating valve in the air conditioning water system. Therefore, it requires all terminal air conditioning equipment to use electrically operated two-way proportional-integral (PI) valves. However, the conventional practice is to use PI valves only for the air conditioning unit and electrically operated two-way on / off valves for the fan coil units. These factors, to some extent, limit the application of the minimum resistance control method. Summary of the Invention

[0006] This invention provides an energy-saving, pressure-independent air conditioning pump valve control method to achieve energy-saving effects.

[0007] This invention provides an energy-saving, pressure-independent air conditioning pump valve control method, comprising the following steps:

[0008] S101. Among the effective valves, perform opening value matching and set the valve with the largest opening value as the target valve;

[0009] S102. If the target valve position is below the first threshold and the target valve has a tendency to continue to close, reduce the operating frequency of the air conditioning pump.

[0010] S103. If the target valve position is higher than the second threshold and the target valve has a tendency to continue to open wider, then increase the operating frequency of the air conditioning pump.

[0011] The first threshold is less than the second threshold.

[0012] Furthermore, the method for obtaining the effective valve is as follows:

[0013] S201. Obtain the operating status and opening information of multiple valves;

[0014] S202. Based on the current operating status and opening information, confirm the valid valves.

[0015] Furthermore, S202. Based on the current operating status and opening information, confirming the effective valves specifically includes:

[0016] If the valve is currently in a pressure-independent operating state (i.e., the operating mode is energy or flow control rather than position control) and the relative flow rate is not less than 10%, then it is a valid valve.

[0017] Furthermore, the first threshold is the 75% valve position.

[0018] Furthermore, the second threshold is the 90% valve position.

[0019] Furthermore, the valve is an electronic energy balance integrated valve (hereinafter referred to as an energy valve);

[0020] Furthermore, the air conditioning pump is a chilled water pump.

[0021] This invention also discloses an integrated air conditioning pump and valve system applying the above-mentioned air conditioning pump and valve control method, comprising several chiller units, several chilled water pumps, a main supply pipe, a main return pipe, and several branch pipes. The number of chilled water pumps is not less than the number of chiller units. The chiller units are connected in parallel, and the chilled water pumps are connected in parallel. The chiller units, main supply pipe, branch pipes, main return pipe, chilled water pumps, and chiller units are connected in sequence. A bypass pipe is also provided between the main supply pipe and the main return pipe. The bypass pipe is equipped with an electric proportional regulating valve; the branch includes a water supply branch pipe, a return water branch pipe, several air conditioning unit loops, several fan coil loops, and an energy valve. The water inlet of the air conditioning unit loop and the fan coil loop is connected to the water supply branch pipe. The water outlet of the air conditioning unit loop, the water outlet of the fan coil loop, and the energy valve are all located on the return water branch pipe. The water outlet of the fan coil loop, the energy valve, the water outlet of the air conditioning unit loop, and the return water main are connected in sequence.

[0022] Furthermore, the bypass pipe is connected to the return water main pipe near the chilled water pump and the supply water main pipe near the chiller unit, respectively. The air conditioning unit loop includes the air conditioning unit and the energy valve, and the energy valve is connected to the outlet of the air conditioning unit.

[0023] Furthermore, the fan coil loop includes a fan coil unit and an electric two-way valve, wherein the electric two-way valve is connected to the outlet of the fan coil unit.

[0024] Compared with existing technologies, this invention collects valve opening values ​​and determines the control scheme for the air conditioning pump by comparing the changes in the opening values ​​of each valve. Compared with traditional water pump frequency conversion control methods, it is more energy-efficient and simpler and more practical to control. Attached Figure Description

[0025] Figure 1 This is a system diagram of an embodiment of the present invention. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0027] This invention discloses an energy-saving, pressure-independent air conditioning pump valve control method, comprising the following steps:

[0028] S101. Among the effective valves, perform opening value matching and set the valve with the largest opening value as the target valve;

[0029] Among them, by acquiring the target valve, the pump frequency is controlled based on the valve with the largest opening value; by detecting the opening of each valve in real time, the most unfavorable terminal is determined, and then the air conditioning water pump is directly frequency-regulated according to the opening and changes of the valves in the loop where the most unfavorable terminal is located, without having to switch to differential pressure control.

[0030] S102. If the target valve position is below the first threshold and the target valve has a tendency to continue to close, reduce the operating frequency of the air conditioning pump.

[0031] S103. If the target valve position is higher than the second threshold and the target valve has a tendency to continue to open wider, then increase the operating frequency of the air conditioning pump.

[0032] The first threshold is less than the second threshold.

[0033] Optionally, the first threshold is 75% of the valve position.

[0034] Optionally, the second threshold is the 90% valve position.

[0035] Optionally, the valve is an electronic energy balance integrated valve (hereinafter referred to as an energy valve);

[0036] Optionally, the air conditioning pump is a chilled water pump.

[0037] If the target valve is at a position greater than 90% and the target valve has a tendency to continue to open further, the chilled water pump will increase its frequency.

[0038] If the target valve is at less than 75% and shows a tendency to continue closing, the chilled water pump frequency should be reduced. During this adjustment process, the total flow rate on the load side needs to be monitored, and the electric proportional control valve on the bypass pipe needs to be adjusted to ensure the chiller unit operates at a flow rate higher than the minimum allowable flow rate.

[0039] The pressure-independent integrated air conditioning pump and valve system of this invention aims to ensure the valve opening is always at its maximum. However, to prevent frequent frequency changes and start-stop cycles of the air conditioning water pump, which could cause severe system fluctuations and control failures, the relatively fully open state of the valve is defined as within a certain range, namely 75% to 90%. Although the valve in this invention cannot achieve 100% full opening, compared to other control technologies, it minimizes static pressure loss, allowing the water pump to deliver chilled water to the terminal with minimal energy consumption, achieving maximum energy savings. Furthermore, the control method of this invention directly controls the water pump frequency conversion through the valve position, requiring no other conversions, resulting in simple system control logic that is easy to implement.

[0040] Optionally, the method for obtaining the effective valve (energy valve) is as follows:

[0041] S201. Obtain the operating status and opening information of multiple valves;

[0042] S202. Based on the current operating status and opening information, confirm the valid valves.

[0043] Specifically, by determining the valve's status, it can be determined whether the valve is in a pressure-independent operating mode; by determining the valve's opening information, it can be determined whether the corresponding branch or demand end of the valve is in operation. If either of these conditions is not met, the valve is considered invalid and is thus excluded to avoid data interference from valves that are not in operation.

[0044] Specifically, S202. Based on the current operating status and opening information, confirming the effective valve includes:

[0045] If the energy valve operates in an energy or flow control mode rather than a position control mode, then the energy valve is in a pressure-independent operating state. Secondly, by determining the relative flow rate of the energy valve, if the relative flow rate of the energy valve is not less than 10% of the maximum set flow rate of the energy valve, it indicates that the energy valve is in normal operation, and the value is a reference value.

[0046] This invention also discloses an integrated air conditioning pump and valve system using the above-described air conditioning pump and valve control method, comprising several chiller units, several chilled water pumps, a main supply pipe, a main return pipe, and several branch pipes. The number of chilled water pumps is not less than the number of chiller units. The chiller units are connected in parallel, and the chilled water pumps are connected in parallel. The chiller units, main supply pipe, branch pipes, main return pipe, chilled water pumps, and chiller units are connected sequentially. A bypass is also provided between the main supply pipe and the main return pipe. The bypass pipe is equipped with an electric proportional regulating valve; the branch includes a water supply branch pipe, a return branch pipe, several air conditioning unit loops, several fan coil loops, and an energy valve. The inlet ends of the air conditioning unit loops and fan coil loops are connected to the water supply branch pipe. The outlet ends of the air conditioning unit loops, the fan coil loops, and the energy valve are all located on the return branch pipe. The outlet ends of the fan coil loops, the energy valve, the air conditioning unit loops, and the main return pipe are connected in sequence.

[0047] Optionally, an ultrasonic flow meter, a temperature sensor, and a pressure sensor are also installed on the return water main located between the bypass pipe and the chilled water pump.

[0048] Specifically, temperature and pressure sensors are also installed on the main water supply pipe located between the bypass pipe and the chiller unit.

[0049] Among them, such as Figure 1 As shown, there are two chiller units, each with one chilled water pump, and one spare chilled water pump. To ensure that the chiller units operate at a flow rate not less than the minimum allowable flow rate, a bypass pipe is installed on the supply and return water mains, and an electric proportional regulating valve is installed on the bypass pipe.

[0050] This invention, through the configuration of a bypass pipe and an electrically operated proportional regulating valve, regulates the flow rates of the main supply and return water pipes. The integrated air conditioning pump and valve system has a flow sensor on the main return water pipe on the cold source side to detect the total flow rate of the return water pipe. This invention, by incorporating an ultrasonic flow meter, temperature sensor, and pressure sensor, can effectively collect information from the main supply and return water pipes. Furthermore, when the water pump frequency drops to a certain level and the total flow rate of the main return water pipe is less than the minimum allowable flow rate for starting the main unit, the electrically operated proportional regulating valve on the bypass pipe opens. Based on the bypass flow rate calculated by the system, the opening degree of the bypass valve is automatically controlled to ensure that the chiller unit operates under conditions exceeding the minimum allowable flow rate.

[0051] The energy valve is an electronic pressure-independent energy regulating valve with pressure-independent flow control, energy control, and proportional-integral functions. Its corresponding electrical signal can be connected to the BAS system via standard communication interfaces such as RJ45 or RS485 to view parameters such as opening degree or flow rate, and to allocate energy as needed according to changes in the terminal load. To improve the transmission rate of valve position information and avoid the impact of communication bandwidth on system response speed, it is generally required to use an RJ45 interface to connect to the control center via Ethernet. In this embodiment of the invention, the energy valve includes an ultrasonic flow meter, an intelligent actuator, and supply and return water temperature sensors. The ultrasonic flow meter and intelligent actuator form the valve body, which is installed on the return water branch pipe. The inlet ends of each fan coil unit loop, the inlet ends of each air conditioning unit loop, and the main water supply pipe are connected sequentially.

[0052] In this embodiment of the invention, the various fan coil unit loops are connected in parallel to form a fan coil unit loop group structure. The inlet and outlet ends of the fan coil unit loop group structure are connected to the valve body of the energy valve and the water supply branch pipe, respectively. Each air conditioning unit loop is directly connected to the main water supply pipe and the main water return pipe through the water supply branch pipe and the return water branch pipe. This embodiment of the invention utilizes the energy valve to achieve separate adjustment of the air conditioning unit loop and the fan coil unit loop on the same branch. Furthermore, in the actual control process of this embodiment of the invention, by obtaining the energy valve with the largest set opening value as the target valve, the water pump can be frequency-controlled based on the energy valve with the largest opening value; by detecting the opening of the energy valve at each end in real time, the most unfavorable end is determined by the opening of the energy valve in each branch, and then the air conditioning water pump is directly frequency-regulated according to the opening of the energy valve in the most unfavorable loop, without having to switch to differential pressure control; optionally, the bypass pipe is connected to the return water main pipe near the chilled water pump and the supply water main pipe near the chiller unit respectively, and the air conditioning unit loop includes the air conditioning unit and the energy valve, and the energy valve is connected to the outlet of the air conditioning unit.

[0053] The valve body of the energy valve is located at the outlet of the air conditioning unit, and the supply and return water temperature sensors of the energy valve are located at the inlet and outlet of the air conditioning unit.

[0054] In this embodiment of the invention, at the terminal side, the air conditioning unit and fan coil unit are each independently configured with a loop. The fan coil unit branches are divided into large branches for different areas and are arranged horizontally in the same direction, while the air conditioning unit branches are arranged in a different direction. Each air conditioning unit terminal and each area's large fan coil branch is equipped with an energy valve. In addition to balancing the water system resistance, this valve can also measure the chilled water flow rate and supply-return water temperature difference of each branch in real time. When the load at the air conditioning unit terminal changes, the energy valve on the air conditioning terminal branch compares the detected water flow rate and temperature difference with the required energy and directly and quickly adjusts the valve opening, avoiding the need for feedback from the indoor temperature control. Therefore, the valve position reflects the demand for changes in terminal load in real time, which not only directly improves the sensitivity of system control but also improves the thermal comfort of the indoor environment. In addition, the energy valve in this embodiment of the invention also has the function of a conventional proportional-integral two-way valve. When the set temperature of the air conditioning terminal thermostat changes, the water flow is adjusted through the action of the water circuit energy valve to achieve the room temperature control effect required by the terminal. The fan coil units still use traditional on / off type electric two-way valves to reduce system complexity and engineering costs. Their terminal control is the same as conventional air conditioning control, meaning the water circuit only has on / off control. However, the energy valves on the main branches of the fan coil unit area can adjust their operation by detecting the temperature of the supply and return water branch pipes. For example, when the supply and return water temperature difference is less than the design temperature difference, it indicates that the current terminal has low cooling requirements, so the valve is adjusted smaller; conversely, the valve is adjusted larger. Alternatively, the control center can use the BA system to statistically analyze the on / off status of the fan coil unit's two-way valves and then issue commands to adjust the energy valves on the coil branch circuits.

[0055] Specifically, the fan coil loop includes a fan coil unit and an electric two-way valve, the electric two-way valve being connected to the outlet of the fan coil unit.

[0056] Optionally, the integrated air conditioning pump and valve system also includes an expansion tank, which is connected to the return water main.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading this application specification, they can still modify or make equivalent substitutions to the specific implementation of the present invention, but these modifications or changes do not depart from the protection scope of the pending claims of the present invention.

Claims

1. A control method of an air conditioning pump-valve integrated system, characterized by, The integrated air conditioning pump and valve system includes several chiller units, several chilled water pumps, a main water supply pipe, a main water return pipe, and several branch lines. The number of chilled water pumps is no less than the number of chiller units. The chiller units are connected in parallel, and the chilled water pumps are also connected in parallel. The chiller units, main water supply pipe, branch lines, main water return pipe, chilled water pumps, and chiller units are connected sequentially. A bypass pipe is also provided between the main water supply pipe and the main water return pipe, and an electrical connection is provided on the bypass pipe. A proportional regulating valve; the branch circuit includes a water supply branch pipe, a return water branch pipe, several air conditioning unit loops, several fan coil loops, and an energy valve. The inlet ends of the air conditioning unit loops and fan coil loops are connected to the water supply branch pipe. The outlet ends of the air conditioning unit loops, the fan coil loops, and the energy valve are all located on the return water branch pipe. The outlet ends of the fan coil loops, the energy valve, the air conditioning unit loops, and the main return water pipe are connected in sequence. The system control method includes the following steps: S101. Among the effective valves, perform opening value matching and set the valve with the largest opening value as the target valve; S102. If the target valve position is below the first threshold and the target valve has a tendency to continue to close, reduce the operating frequency of the air conditioning pump. S103. If the target valve position is higher than the second threshold and the target valve has a tendency to continue to open wider, then increase the operating frequency of the air conditioning pump. The first threshold is less than the second threshold; The method for obtaining the effective valve is as follows: S201. Obtain the operating status and opening information of multiple valves; S202. Based on the current operating status and opening information, confirm the valid valves; S202. Based on the current operating status and opening information, the specific effective valves confirmed include: If the valve is currently in a pressure-independent operating state, that is, the operating mode is energy or flow control rather than position control, and the relative flow rate is not less than 10%, then it is a valid valve; The first threshold is 75% valve position; The second threshold is 90% valve position; the valve is an electronic energy balance integrated valve.

2. The control method of claim 1, wherein the pump valve integrated system is an air conditioner. The air conditioning pump is a chilled water pump.

3. The control method of claim 2, wherein the pump valve integrated system is an air conditioner. The bypass pipe is connected to the return water main pipe near the chilled water pump and the supply water main pipe near the chiller unit. The air conditioning unit loop includes the air conditioning unit and the energy valve, and the energy valve is connected to the outlet of the air conditioning unit.

4. The control method for an integrated air conditioning pump and valve system according to claim 1, characterized in that, The fan coil loop includes a fan coil unit and an electric two-way valve, wherein the electric two-way valve is connected to the outlet of the fan coil unit.

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