Multi-stage gas-water heat exchanger temperature coordination control method and system based on hydraulic balance calculation

Abstract

The present application belongs to the field of thermal automatic control, and particularly relates to a multi-stage gas-water heat exchanger temperature collaborative control method and system based on hydraulic balance calculation. The method first sets variables corresponding to the multi-stage gas-water heat exchanger system, constructs a state space model and a prediction model describing the thermal dynamic characteristics of the multi-stage gas-water heat exchanger; uses a state estimator to process the multi-stage gas-water heat exchanger system to obtain an estimated value of the system state; then, reference values of the water side flow rates of each branch are calculated; a pressure-flow hydraulic balance model of the multi-branch pipe network is established by establishing continuity equations and pipe segment pressure drop equations of each node; under the condition of satisfying the constraints of the hydraulic balance model, reference values of the opening degrees of the corresponding valves are solved according to the reference values of the water side flow rates of each branch to adjust the water side flow rates of each branch. The present application can maintain good temperature tracking performance and system stability under the conditions of uncertain system parameters, changing operating conditions and mutual interaction of multiple loops.

Description

Technical Field

[0001] This invention belongs to the field of thermal automatic control, specifically relating to a method and system for coordinated temperature control of a multi-stage gas-water heat exchanger based on hydraulic balance calculation. Background Technology

[0002] With the increasing demands for energy efficiency and operational stability in industrial processes, multistage gas-water heat exchangers, as crucial equipment for gas cooling, waste heat recovery, and temperature regulation, have been widely applied in energy, chemical, power, and data center cooling industries. Multistage gas-water heat exchanger systems typically consist of multiple parallel heat exchange loops. The outlet gas temperature of different heat exchange units is controlled by adjusting the water-side flow rate of each loop. These systems offer advantages such as compact structure, high heat exchange efficiency, and flexible adjustment. However, their operation involves the coupling of thermodynamic and hydraulic processes, resulting in complex system dynamic characteristics and placing high demands on control strategies.

[0003] In multi-stage gas-water heat exchanger systems, each heat exchange loop typically shares a common water-side supply and return water network, and the branches are coupled to each other through the network's pressure distribution. Adjusting the water-side flow rate in one heat exchange loop often causes passive changes in the flow rates of other loops, thus affecting the outlet gas temperature of the corresponding heat exchanger. Furthermore, the water-side network contains frictional resistance and local resistance, and the relationship between valve opening and branch flow rate exhibits a significant nonlinearity, resulting in strong nonlinearity and coupling characteristics throughout the system. These factors make it difficult to solve the temperature control problem of multi-stage gas-water heat exchangers using simple independent loop adjustment methods.

[0004] Model predictive control (MRC), a rolling time-domain optimization control method based on a system model, can comprehensively consider the dynamic characteristics and future behavior of a system under constraints and has been widely applied in the field of temperature control for heat exchange processes. Existing research often uses MRC to design individual heat exchange loops, adjusting the water-side flow rate of the loop to achieve tracking control of the corresponding outlet gas temperature. However, these methods typically treat each heat exchange loop as an independent entity, neglecting the hydraulic coupling relationship between loops in the water-side network. Under multi-loop parallel operation conditions, the above simplified assumptions cannot accurately reflect the actual operating characteristics of the system, easily leading to flow distribution imbalances, decreased control performance, and even mutual interference between loops. Therefore, there is an urgent need for a temperature control method that can comprehensively consider the hydraulic balance characteristics of the water-side network and achieve coordinated regulation between loops in multi-stage gas-water heat exchangers. Summary of the Invention

[0005] The present invention aims to at least partially solve one of the technical problems in the related art.

[0006] Therefore, the first objective of this invention is to propose a method for coordinated temperature control of a multi-stage gas-water heat exchanger based on hydraulic balance calculations, comprising the following steps:

[0007] S1: Set the variables corresponding to the multi-stage gas-water heat exchanger system, and construct a state-space model describing the thermal dynamic characteristics of the multi-stage gas-water heat exchanger based on the water flow rate of each branch and the air temperature at the outlet of each stage heat exchanger. Process the state-space model through the state expansion method to obtain the prediction model required for predictive control. S2: Based on the state space model and the outlet air temperature of each stage of heat exchanger, design a state estimator to estimate the state of the multi-stage gas-water heat exchanger system and obtain the estimated value of the system state. S3: For each stage of heat exchanger, construct model predictive control problems based on the state space model, and calculate the reference values ​​of the water flow rate of each branch according to the deviation between the corresponding output variable and its temperature setpoint. S4: The nodal method is used to perform hydraulic calculations on the water-side pipe network of the multi-stage heat exchanger system. By establishing the continuity equation and the pressure drop equation of each node and pipe section, the flow distribution of each branch is obtained, and a pressure-flow hydraulic balance model of the multi-branch pipe network is established. S5: Under the condition of satisfying the constraints of the hydraulic balance model, the reference value of the opening degree of the corresponding valve is solved according to the reference value of the water flow of each branch. The valve actuator is controlled according to the valve opening reference value so that each valve reaches the corresponding valve opening degree to regulate the water flow of each branch. S6: In the next control cycle, collect the operating data of the multi-stage gas-water heat exchanger system, and update the state estimator and model predictive control calculation based on the collected outlet air temperature to realize the rolling optimization control of the multi-stage gas-water heat exchanger.

[0008] In one embodiment of the present invention, S2 further includes: S11, For a multi-stage air-water heat exchanger system, the air-side outlet temperature of each heat exchanger is selected as the controlled variable, the water-side flow rate of each heat exchanger is set as the control variable, and the changes in air-side flow rate and air-side inlet temperature are set as disturbances. S12, using the water flow rate of each branch as the control variable and the air temperature at the outlet of each heat exchanger as the output variable, construct a state-space model, and then discretize the state-space model to obtain a discrete state-space model. S13, the discrete state-space model is expanded to obtain the incremental state-space equation, which serves as the prediction model in predictive control design.

[0009] In one embodiment of the present invention, S2 further includes: S21. Use a Kalman filter observer to estimate the state variables of the state-space model in real time to obtain the state observer model. S22, using a prediction model to predict the outlet air temperature of each stage of heat exchanger in the prediction time domain.

[0010] In one embodiment of the present invention, S3 further includes: S31, calculates the water-side mass flow rate of each stage of the gas-water heat exchanger based on the model predictive control algorithm; S32, the water-side mass flow rate of each air-water heat exchanger is processed using the index optimization function to obtain the reference value of the water-side flow rate of each branch.

[0011] In one embodiment of the present invention, S32 further includes: For the i-th gas-water heat exchanger, its corresponding performance index optimization function is:

[0012] The performance indicators include the deviation between the system output and the setpoint, as well as the increment of the control variable; in the formula... For the output of the prediction model, The set value output for the controlled object; These are the upper and lower limits of the increment of the control variable, respectively; These are the upper and lower limits of the control variable, respectively. Here is the weight coefficient matrix, where, and It is a diagonal matrix. The elements in the diagonal matrix correspond to the weights of the temperature deviation of the heat transfer fluid at the air-side outlet of each stage of the heat exchanger during the optimization calculation. The elements in the diagonal matrix correspond to the weights of the increments of the water-side fluid mass flow rates in each stage of the heat exchanger during the optimization calculation.

[0013] In one embodiment of the present invention, S4 further includes: S41, The nodal method is used to perform hydraulic calculations on the water-side pipe network of the multi-stage heat exchanger system. The pressure of each node is taken as an unknown quantity, and a continuity equation that satisfies the mass conservation of each node is established. S42, Establish the pressure drop equation for the water-side pipe section of a multi-stage heat exchanger system based on the pressure loss coefficient; S43. By solving the continuity equation and the pressure drop equation simultaneously, the flow distribution of each branch is obtained, and a pressure-flow hydraulic balance model for a multi-branch pipeline network is constructed.

[0014] In one embodiment of the present invention, the continuity equation in step S41 is established based on the sum of the mass flow rates of the branch pipes flowing into the nodes in the pipe network and the sum of the mass flow rates of the nodes flowing out to the branch pipes in the water-side pipe network. The pressure drop equation in step S42 is obtained by multiplying the sum of the equivalent coefficient of the friction loss along the pipe section and the equivalent coefficient of the local pressure loss of the pipe section by the square of the mass flow rate passing through the pipe section.

[0015] In one embodiment of the present invention, S5 further includes: Based on the reference values ​​of water-side flow rate of each stage of heat exchanger obtained by model predictive control calculation, and taking into account the flow-pressure relationship model of the water-side pipe network, the opening reference values ​​of the regulating valves of each stage of heat exchanger that match the water-side flow rate reference values ​​are solved to achieve coordinated distribution of water-side flow rate in each heat exchanger loop.

[0016] To achieve the above objectives, a second aspect of the present invention proposes a multi-stage gas-water heat exchanger temperature coordination control system based on hydraulic balance calculation, comprising: The state space module and the prediction model construction module are used to set the variables corresponding to the multi-stage gas-water heat exchanger system, and construct a state space model describing the thermal dynamic characteristics of the multi-stage gas-water heat exchanger based on the water side flow rate of each branch and the outlet air temperature of each stage heat exchanger. The state space model is processed by the state amplification method to obtain the prediction model required in predictive control. The system state estimation module is used to design a state estimator based on the state space model and the outlet air temperature of each stage of heat exchanger, to estimate the state of the multi-stage gas-water heat exchanger system and obtain the estimated value of the system state. The water-side flow calculation module is used to construct model predictive control problems based on the state-space model for each stage of heat exchanger, and calculate the reference value of the water-side flow of each branch according to the deviation between the corresponding output variable and its temperature setpoint. The pressure-flow hydraulic balance model construction module is used to perform hydraulic calculations on the water-side pipe network of a multi-stage heat exchanger system using the nodal method. By establishing the continuity equation and pipe section pressure drop equation for each node, the flow distribution of each branch is obtained, and a pressure-flow hydraulic balance model of the multi-branch pipe network is established. The system control module is used to solve for the corresponding valve opening reference value based on the reference value of the water-side flow of each branch under the condition of satisfying the constraints of the hydraulic balance model, and to control the valve actuator according to the valve opening reference value so that each valve reaches the corresponding valve opening degree, thereby adjusting the water-side flow of each branch.

[0017] To achieve the above objectives, a third aspect of the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the method described in the first aspect.

[0018] Compared with existing technologies, the method, system, and storage medium of this invention introduce hydraulic balance calculations within a model predictive control framework. This explicitly incorporates the hydraulic coupling relationships between loops in a multi-stage gas-water heat exchanger system into the control scheme, achieving coordinated optimization of multi-loop temperature regulation and water-side flow distribution. This method avoids the problem of drastically increased computational scale caused by treating the entire multi-stage heat exchanger system as a single object for centralized optimization. It also overcomes the performance degradation resulting from neglecting hydraulic coupling in traditional single-loop control methods. This invention maintains good temperature tracking performance and system stability under conditions of uncertain system parameters, changing operating conditions, and multi-loop interactions, achieving efficient and coordinated operation of the multi-stage gas-water heat exchanger system.

[0019] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 A structural diagram of a multi-stage gas-water heat exchanger system in an existing compressed air energy storage system. Figure 2 This is a flowchart of the multi-stage air-water heat exchanger temperature collaborative control method based on hydraulic balance calculation in this invention. Figure 3 Block diagram of predictive control algorithm for a single heat exchanger model; Figure 4 For the output disturbance of heat exchanger #1; Figure 5 The changes of air-side outlet temperature, water-side flow rate, and water-side flow rate over time in a multi-stage air-water heat exchanger temperature coordination control based on hydraulic balance calculations; Figure 6 The change of valve opening of the water-side inlet regulating valve of each stage heat exchanger with time under the temperature coordinated control of a multi-stage air-water heat exchanger based on hydraulic balance calculation; Figure 7 This is a structural diagram of the multi-stage gas-water heat exchanger temperature collaborative control system based on hydraulic balance calculation in this invention. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0023] The following describes, with reference to the accompanying drawings, a method for coordinated temperature control of a multi-stage gas-water heat exchanger based on hydraulic balance calculation, according to an embodiment of the present invention.

[0024] Example 1 like Figure 1 The diagram shows the structure of a multi-stage gas-water heat exchanger system in a prior art compressed air energy storage system. For this system, the present invention proposes a multi-stage gas-water heat exchanger temperature coordination control method based on hydraulic balance calculations. The steps are as follows: Figure 2 As shown.

[0025] S1: Set the variables corresponding to the multi-stage gas-water heat exchanger system, and construct a state-space model describing the thermal dynamic characteristics of the multi-stage gas-water heat exchanger based on the water flow rate of each branch and the air temperature at the outlet of each stage of the heat exchanger. Process the state-space model through the state expansion method to obtain the prediction model required for predictive control.

[0026] Specifically, for a multi-stage air-water heat exchanger system, the air-side outlet temperature of each heat exchanger is selected as the controlled variable, the water-side flow rate of each heat exchanger is set as the control variable, and the changes in air-side flow rate and air-side inlet temperature are set as disturbances.

[0027] A state-space model is constructed using the water flow rate of each branch as the control variable and the outlet air temperature of each stage of heat exchanger as the output variable. The expression is as follows:

[0028] in, These are the state variables of the system; u The control variable is the water-side mass flow rate of the gas-water heat exchanger; y The output variable is the air-side outlet temperature of the air-water heat exchanger. For time; This is the system correlation matrix.

[0029] Furthermore, the system correlation matrix in the state-space model of the multi-stage gas-water heat exchanger The heat transfer equations for the water-side system of a multi-stage heat exchanger system are obtained and expressed in block matrix form:

[0030] in, The matrix represents the number of heat exchanger branches in a multi-stage steam-water heat exchanger. The dynamics of each stage of the heat exchanger are described separately:

[0031] in, For gas-water heat exchangers# The state; For gas-water heat exchangers# Water-side mass flow rate; For gas-water heat exchangers The air-side outlet temperature.

[0032] Furthermore, in step S2, formula (1) is discretized to obtain the discrete state-space model shown in formula (4) below:

[0033] in This is a discrete mathematical model for a multi-stage gas-water heat exchanger system. Specifically, it includes a single-stage gas-water heat exchanger. The discretized state-space model is as follows:

[0034] Based on the established state-space model, the prediction model required for predictive control is obtained through state expansion. The state-space model of a single gas-water heat exchanger shown in equation (5) is expanded to obtain the incremental state-space equation shown in equation (6), which serves as the prediction model in predictive control design.

[0035] in, Indicates the parameter increment. , ; This represents the expanded system state. .

[0036] S2: The system state variables are estimated in real time by a Kalman filter observer. The state observer model is shown in Equation (7):

[0037] in, Let covariance matrix be the variance matrix. For observer gain, and The covariance matrix reflects the covariance of process noise and measurement noise, respectively. State estimation for a multi-stage gas-water heat exchanger system. (Subscript) This indicates that the variable is a gas-water heat exchanger. The attributes or control system status.

[0038] S3: Based on the prediction model of formula (6), for the future Step's system output variables The prediction is made as shown in equation (8):

[0039] in

[0040]

[0041] in, To predict the time domain, To control the time domain, .

[0042] For each stage of the gas-water heat exchanger, the water-side mass flow rate is calculated based on a model predictive control algorithm. Specifically, for the gas-water heat exchanger # The performance index optimization function in step S3 is expressed as follows:

[0043] The performance indicators include the deviation between the system output and the setpoint, as well as the increment of the control variable; in the formula... For the output of the prediction model, This is the weight coefficient matrix. The set value output for the controlled object; These are the upper and lower limits of the increment of the control variable, respectively; These are the upper and lower limits of the control variable, respectively.

[0044] S4: The nodal method is used to perform hydraulic calculations on the water-side pipe network of the multi-stage heat exchanger system. The pressure at each node is taken as an unknown quantity, and a continuity equation that satisfies the mass conservation of each node and a pipe section pressure drop equation based on the pressure loss coefficient are established. Under the assumption of incompressible flow, the nodal continuity equation and the pipe section pressure drop equation are shown in equations (12)-(13):

[0045]

[0046] in, The mass flow rate of the branch pipes flowing into the node in the water-side pipe network. This refers to the mass flow rate from a node in the water-side pipe network to a branch pipe. This refers to the mass flow rate passing through the pipe section. For the pressure loss of the pipe section, This is the equivalent coefficient for the friction loss along the pipe section. This represents the equivalent coefficient for local pressure loss in the pipe section. The flow distribution of each branch is obtained by simultaneously solving the continuity equation and the pressure drop equation.

[0047] S5: Based on the reference values ​​of water-side flow rate of each stage of heat exchanger obtained by model predictive control calculation, and taking into account the flow-pressure relationship model of the water-side pipe network, the opening reference values ​​of the regulating valves of each stage of heat exchanger that match the reference values ​​of water-side flow rate are solved to achieve coordinated distribution of water-side flow rate in each heat exchanger loop.

[0048] S6: In the performance metric optimization function, weights This is a diagonal matrix, where the elements correspond to the weights of the temperature deviations of the heat transfer fluid at the air-side outlet of each stage of the heat exchanger during the optimization calculation; weights It is a diagonal matrix, and the elements in the diagonal matrix correspond to the weights of the increments of the water-side fluid mass flow rates of each stage of the heat exchanger during the optimization calculation.

[0049] Furthermore, in step S8, under the premise of satisfying the constraints in (11), the controller solves the optimization problem at each sampling time and feeds the calculated valve opening to the actual multi-stage gas-water heat exchanger water-side pipeline system.

[0050] Based on the above scheme, in order to verify the effectiveness and superiority of the method of the present invention, simulation verification is performed in this embodiment, as follows: This embodiment demonstrates the simulation verification of the multi-stage gas-water heat exchanger temperature coordination control method based on hydraulic balance calculation proposed in this invention. Figure 2 A schematic diagram of the multi-stage air-water heat exchanger system structure used for simulation verification of the compressed air energy storage system. Figures 3 to 5 The diagram shows the control effect of the proposed control method. In the simulation experiment, heat exchanger #1 was subjected to an output step disturbance with an amplitude of 1 and a sign of "+" at 800 seconds, while the setpoint underwent multiple step changes.

[0051] All controller parameters are set as follows: The range of variation of the single-loop fluid mass flow rate on the water side is: The rate of change does not exceed .

[0052] Depend on Figures 4 to 6As shown, the multi-stage gas-water heat exchanger temperature coordination control method proposed in this invention, based on hydraulic balance calculation, comprehensively considers the flow-pressure relationship of the water-side pipeline network within a model predictive control framework. By coordinating the solution of the opening degrees of the corresponding regulating valves of each stage of the heat exchanger, it achieves a reasonable distribution of the multi-loop water-side flow. Under the action of this control method, the outlet gas temperature of each stage of the heat exchanger can be stably regulated and gradually tends to the set value, effectively suppressing temperature fluctuations during system operation and maintaining overall stable operation.

[0053] This invention designs a multi-stage air-water heat exchanger temperature coordination control method based on hydraulic balance calculation, decoupling temperature regulation from hydraulic distribution in the control structure. Specifically, by constructing predictive control problems for each stage of the heat exchanger, the computational complexity caused by large-scale centralized optimization of the entire multi-stage system is avoided. Simultaneously, a hydraulic balance model of the water-side pipe network is introduced at the execution layer, comprehensively considering the pressure coupling relationship between branches and valve characteristics, achieving a unified solution from water-side flow reference values ​​to valve opening reference values. This approach explicitly incorporates the hydraulic coupling between loops into the control calculation process, overcoming the problem of flow distribution imbalance caused by neglecting the mutual influence between loops in traditional methods.

[0054] Example 2 like Figure 7 As shown, this invention proposes a multi-stage gas-water heat exchanger temperature coordination control system based on hydraulic balance calculation, comprising: The state space module and the prediction model construction module are used to set the variables corresponding to the multi-stage gas-water heat exchanger system, and construct a state space model describing the thermal dynamic characteristics of the multi-stage gas-water heat exchanger based on the water side flow rate of each branch and the outlet air temperature of each stage heat exchanger. The state space model is processed by the state amplification method to obtain the prediction model required in predictive control. The system state estimation module is used to design a state estimator based on the state space model and the outlet air temperature of each stage of heat exchanger, to estimate the state of the multi-stage gas-water heat exchanger system and obtain the estimated value of the system state. The water-side flow calculation module is used to construct model predictive control problems based on the state-space model for each stage of heat exchanger, and calculate the reference value of the water-side flow of each branch according to the deviation between the corresponding output variable and its temperature setpoint. The pressure-flow hydraulic balance model construction module is used to perform hydraulic calculations on the water-side pipe network of a multi-stage heat exchanger system using the nodal method. By establishing the continuity equation and pipe section pressure drop equation for each node, the flow distribution of each branch is obtained, and a pressure-flow hydraulic balance model of the multi-branch pipe network is established. The system control module is used to solve for the corresponding valve opening reference value based on the reference value of the water-side flow of each branch under the condition of satisfying the constraints of the hydraulic balance model, and to control the valve actuator according to the valve opening reference value so that each valve reaches the corresponding valve opening degree, thereby adjusting the water-side flow of each branch.

[0055] The proposed collaborative control system, based on a model predictive control design framework and a state-space model of a multi-stage gas-water heat exchanger system, addresses the problem of coordinated regulation of the outlet gas temperature of each heat exchanger under multi-loop parallel operation conditions. It proposes a temperature collaborative control method incorporating hydraulic balance calculations. By using the water-side flow rate of each heat exchanger as the control variable, model predictive control is used to perform rolling optimization regulation of the outlet gas temperature of each heat exchanger, satisfying the temperature setpoint while considering the system's dynamic characteristics and operational constraints. Furthermore, based on the flow-pressure relationship model of the water-side pipe network, this invention maps the water-side flow rate reference value calculated by model predictive control to the corresponding regulating valve opening, achieving coordinated distribution of the water-side flow rate in the multi-stage gas-water heat exchanger system, thereby causing the outlet gas temperature of each heat exchanger to tend towards its respective setpoint.

[0056] The present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the above-described method for coordinated temperature control of a multi-stage gas-water heat exchanger based on hydraulic balance calculation.

[0057] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0058] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

Claims

1. A method for coordinated temperature control of a multi-stage gas-water heat exchanger based on hydraulic balance calculation, characterized in that, Includes the following steps: S1: Set the variables corresponding to the multi-stage gas-water heat exchanger system, and construct a state-space model describing the thermal dynamic characteristics of the multi-stage gas-water heat exchanger based on the water flow rate of each branch and the air temperature at the outlet of each stage heat exchanger. Process the state-space model through the state expansion method to obtain the prediction model required for predictive control. S2: Based on the state space model and the outlet air temperature of each stage of heat exchanger, design a state estimator to estimate the state of the multi-stage gas-water heat exchanger system and obtain the estimated value of the system state. S3: For each stage of heat exchanger, construct model predictive control problems based on the state space model, and calculate the reference values ​​of the water flow rate of each branch according to the deviation between the corresponding output variable and its temperature setpoint. S4: The nodal method is used to perform hydraulic calculations on the water-side pipe network of the multi-stage heat exchanger system. By establishing the continuity equation and the pressure drop equation of each node and pipe section, the flow distribution of each branch is obtained, and a pressure-flow hydraulic balance model of the multi-branch pipe network is established. S5: Under the condition of satisfying the constraints of the hydraulic balance model, the reference value of the opening degree of the corresponding valve is solved according to the reference value of the water flow of each branch. The valve actuator is controlled according to the valve opening reference value so that each valve reaches the corresponding valve opening degree to regulate the water flow of each branch. S6: In the next control cycle, collect the operating data of the multi-stage gas-water heat exchanger system, and update the state estimator and model predictive control calculation based on the collected outlet air temperature to realize the rolling optimization control of the multi-stage gas-water heat exchanger.

2. The method according to claim 1, characterized in that, S2 further includes: S11, For a multi-stage air-water heat exchanger system, the air-side outlet temperature of each heat exchanger is selected as the controlled variable, the water-side flow rate of each heat exchanger is set as the control variable, and the changes in air-side flow rate and air-side inlet temperature are set as disturbances. S12, using the water flow rate of each branch as the control variable and the air temperature at the outlet of each heat exchanger as the output variable, construct a state-space model, and then discretize the state-space model to obtain a discrete state-space model. S13, the discrete state-space model is expanded to obtain the incremental state-space equation, which serves as the prediction model in predictive control design.

3. The method according to claim 1, characterized in that, S2 further includes: S21. Use a Kalman filter observer to estimate the state variables of the state-space model in real time to obtain the state observer model. S22, using a prediction model to predict the outlet air temperature of each stage of heat exchanger in the prediction time domain.

4. The method according to claim 1, characterized in that, S3 further includes: S31, calculates the water-side mass flow rate of each stage of the gas-water heat exchanger based on the model predictive control algorithm; S32, the water-side mass flow rate of each air-water heat exchanger is processed using the index optimization function to obtain the reference value of the water-side flow rate of each branch.

5. The method according to claim 1, characterized in that, S32 further includes: For the i-th gas-water heat exchanger, its corresponding performance index optimization function is: The performance indicators include the deviation between the system output and the setpoint, as well as the increment of the control variable; in the formula... For the output of the prediction model, The set value output for the controlled object; These are the upper and lower limits of the increment of the control variable, respectively; These are the upper and lower limits of the control variable, respectively. Here is the weight coefficient matrix, where, and It is a diagonal matrix. The elements in the diagonal matrix correspond to the weights of the temperature deviation of the heat transfer fluid at the air-side outlet of each stage of the heat exchanger during the optimization calculation. The elements in the diagonal matrix correspond to the weights of the increments of the water-side fluid mass flow rates in each stage of the heat exchanger during the optimization calculation.

6. The method according to claim 1, characterized in that, S4 further includes: S41, The nodal method is used to perform hydraulic calculations on the water-side pipe network of the multi-stage heat exchanger system. The pressure of each node is taken as an unknown quantity, and a continuity equation that satisfies the mass conservation of each node is established. S42, Establish the pressure drop equation for the water-side pipe section of a multi-stage heat exchanger system based on the pressure loss coefficient; S43. By solving the continuity equation and the pressure drop equation simultaneously, the flow distribution of each branch is obtained, and a pressure-flow hydraulic balance model for a multi-branch pipeline network is constructed.

7. The method according to claim 6, characterized in that, The continuity equation described in step S41 is based on the sum of the mass flow rates of the branch pipes flowing into the nodes in the pipe network and the sum of the mass flow rates of the nodes flowing out to the branch pipes in the water-side pipe network. The pressure drop equation in step S42 is obtained by multiplying the sum of the equivalent coefficient of the friction loss along the pipe section and the equivalent coefficient of the local pressure loss of the pipe section by the square of the mass flow rate passing through the pipe section.

8. The method according to claim 1, characterized in that, The S5 also includes: Based on the reference values ​​of water-side flow rate of each stage of heat exchanger obtained by model predictive control calculation, and taking into account the flow-pressure relationship model of the water-side pipe network, the opening reference values ​​of the regulating valves of each stage of heat exchanger that match the water-side flow rate reference values ​​are solved to achieve coordinated distribution of water-side flow rate in each heat exchanger loop.

9. A multi-stage gas-water heat exchanger temperature coordination control system based on hydraulic balance calculation, characterized in that, include: The state space module and the prediction model construction module are used to set the variables corresponding to the multi-stage gas-water heat exchanger system, and construct a state space model describing the thermal dynamic characteristics of the multi-stage gas-water heat exchanger based on the water side flow rate of each branch and the outlet air temperature of each stage heat exchanger. The state space model is processed by the state amplification method to obtain the prediction model required in predictive control. The system state estimation module is used to design a state estimator based on the state space model and the outlet air temperature of each stage of heat exchanger, to estimate the state of the multi-stage gas-water heat exchanger system and obtain the estimated value of the system state. The water-side flow calculation module is used to construct model predictive control problems based on the state-space model for each stage of heat exchanger, and calculate the reference value of the water-side flow of each branch according to the deviation between the corresponding output variable and its temperature setpoint. The pressure-flow hydraulic balance model construction module is used to perform hydraulic calculations on the water-side pipe network of a multi-stage heat exchanger system using the nodal method. By establishing the continuity equation and pipe section pressure drop equation for each node, the flow distribution of each branch is obtained, and a pressure-flow hydraulic balance model of the multi-branch pipe network is established. The system control module is used to solve for the corresponding valve opening reference value based on the reference value of the water-side flow of each branch under the condition of satisfying the constraints of the hydraulic balance model, and to control the valve actuator according to the valve opening reference value so that each valve reaches the corresponding valve opening degree, thereby adjusting the water-side flow of each branch.

10. A computer-readable storage medium storing a computer program that, when executed by a processor, implements the method as claimed in any one of claims 1-8.

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