A method and system for controlling an air handling unit under unknown wet load conditions

Abstract

The present invention discloses a method and system for controlling an air handling unit under unknown wet load conditions, and relates to the technical field of air handling unit control. The steps include: determining the influencing parameters of the indoor environment according to the working process of the air handling unit; modeling the air handling unit according to the thermodynamic law and the law of physics in combination with the influencing parameters of the indoor environment to obtain an air handling unit model; introducing a gain coefficient to the air handling unit model to process related unknown parameters; and designing a controller according to the processed air handling unit model; and using the controller to control the air handling unit to regulate the indoor temperature, humidity and carbon dioxide concentration. The present invention dynamically analyzes the characteristics of the air handling unit, establishes a suitable physical model, designs a controller, and finally realizes the control of indoor temperature, humidity and carbon dioxide concentration, thereby solving the problem of air handling unit control under uncertain indoor wet load conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of air handling unit control, and in particular to a method and system for controlling an air handling unit under a condition where a wet load is unknown. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] HVAC systems have been widely used in modern buildings to improve indoor air quality. At present, building energy consumption accounts for about 40% of global energy consumption, and HVAC systems account for more than 50% of building energy consumption. The air handling unit is the end of the HVAC system that contacts the room and can adjust the indoor temperature and humidity. A good air handling unit control strategy can not only achieve indoor temperature and humidity control, but also has important significance for energy conservation and emission reduction.

[0004] The air handling unit is a typical multi-input multi-output system with strong coupling and nonlinearity. Traditional switch control and PID control are currently the most commonly used control methods for air handling units, but their control errors are large and they cannot adjust the indoor temperature, humidity and carbon dioxide concentration in time, resulting in poor indoor thermal comfort. At the same time, due to the large mobility of indoor personnel and the variability of the indoor environment, the indoor humidity load is usually unknown and uncertain. Ordinary control methods cannot achieve good control of air handling units. Therefore, it is particularly important to design a method that can accurately control the temperature, humidity and carbon dioxide of air handling units when the humidity load is unknown. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an air handling unit control method and system under the condition of unknown wet load. By dynamically analyzing the characteristics of the air handling unit, establishing a suitable physical model, and designing a controller, the indoor temperature, humidity and carbon dioxide concentration can be controlled, thereby solving the air handling unit control problem under the condition of uncertain indoor wet load.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A first aspect of the present invention provides a method for controlling an air handling unit when the wet load is unknown, comprising the following steps:

[0008] Determine the influencing parameters of the indoor environment according to the working process of the air handling unit;

[0009] According to the laws of thermodynamics and physics, the air handling unit is modeled based on the influencing parameters of the indoor environment to obtain an air handling unit model;

[0010] Introduce gain coefficients into the air handling unit model to process related unknown parameters; and design a controller based on the processed air handling unit model;

[0011] According to the relationship between the control input and related parameters in the controller, the control input size is adjusted to achieve control of indoor temperature, humidity and carbon dioxide concentration.

[0012] Furthermore, the air handling unit includes an air valve, a control valve, a filter, a cooling coil, a dehumidification device and a supply and return air fan.

[0013] Furthermore, the influencing parameters of the indoor environment include indoor temperature, supply air temperature, outdoor temperature, supply air flow, cold water flow, indoor humidity, supply air humidity, fresh air ratio, carbon dioxide generation, outdoor humidity, indoor load, wet load, air specific heat, water specific heat, indoor area, unit area, carbon dioxide concentration and inlet and return water temperature difference.

[0014] Furthermore, a gain coefficient is introduced into the air handling unit model to process related unknown parameters; and the specific steps of designing a controller according to the processed air handling unit model are as follows:

[0015] Set the desired humidity, desired CO2 concentration, and desired temperature according to the air handling unit model;

[0016] Introduce gain coefficients and construct the state equation based on the desired humidity, desired CO2 concentration, and desired temperature;

[0017] The controller design is achieved by solving the state variables according to the state equation.

[0018] Furthermore, the Lyapunov function is introduced through the backstepping method to design the controller by solving the state variables of the state equation in a step-by-step manner.

[0019] Furthermore, according to the uncertainty of the wet load, the wet load change is assumed to obtain the upper and lower limits of the wet load, and the air handling unit model is constrained according to the upper and lower limits of the wet load;

[0020] Furthermore, the control effect of the controller is verified based on the assumptions about the wet load variation and the Lyapunov stability theorem.

[0021] A second aspect of the present invention provides an air handling unit control system when the wet load is unknown, comprising:

[0022] An influencing factor module is configured to determine influencing parameters of the indoor environment according to a working process of the air handling unit;

[0023] The model building module is configured to model the air handling unit according to the thermodynamic law and the physical law in combination with the influencing parameters of the indoor environment to obtain the air handling unit model;

[0024] The controller design module is configured to introduce a gain coefficient into the air handling unit model to process related unknown parameters; and design a controller according to the processed air handling unit model;

[0025] The control module is configured to adjust the control input size according to the relationship between the control input and related parameters in the controller, thereby achieving control of indoor temperature, humidity and carbon dioxide concentration.

[0026] A third aspect of the present invention provides a medium having a program stored thereon, which, when executed by a processor, implements the steps of the method for controlling an air handling unit under unknown wet load conditions as described in the first aspect of the present invention.

[0027] The fourth aspect of the present invention provides a device, including a memory, a processor, and a program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps in the method for controlling an air handling unit under unknown wet load conditions as described in the first aspect of the present invention are implemented.

[0028] One or more of the above technical solutions have the following beneficial effects:

[0029] The present invention provides an air handling unit control method under the condition of unknown wet load, which is used to solve the air handling unit control problem under the condition of uncertain indoor wet load. The method first dynamically analyzes the characteristics of the air handling unit, establishes a suitable physical model based on its characteristics; transforms the model state, defines input and output and state variables, and constructs a mathematical model form suitable for backstepping design; introduces gain coefficients to process related unknown parameters, gradually selects appropriate Lyapunov functions through improved backstepping, designs controllers, and proves the stability of the closed-loop system, thereby realizing the control of indoor temperature, humidity and carbon dioxide concentration under the condition of wet load position.

[0030] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0032] Figure 1 This is a flow chart of a method for controlling an air handling unit when the wet load is unknown in Embodiment 1 of the present invention;

[0033] Figure 2 This is a structural diagram of an air handling unit in Embodiment 1 of the present invention. DETAILED DESCRIPTION

[0034] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0035] Embodiment 1:

[0036] Embodiment 1 of the present invention provides a method for controlling an air handling unit when the wet load is unknown. Figure 1 As shown, the following steps are included:

[0037] Step 1: Determine the influencing parameters of the indoor environment according to the working process of the air handling unit;

[0038] Step 2: Based on the influencing parameters of the indoor environment and the laws of thermodynamics and physics, the air handling unit is modeled to obtain an air handling unit model;

[0039] Step 3: Introduce a gain coefficient into the air handling unit model to process related unknown parameters; and design a controller based on the processed air handling unit model;

[0040] Step 4: Use the controller to control the air handling unit to adjust the indoor temperature, humidity and carbon dioxide concentration. Specifically, according to the relationship between the control input and related parameters in the controller, the control input size is adjusted to achieve the control of the indoor temperature, humidity and carbon dioxide concentration.

[0041] In step 1, the air handling unit includes a damper, a control valve, a filter, a cooling coil, a dehumidifier and a supply and return air fan. The specific structure is as follows: Figure 2 As shown. The HVAC supplies chilled water to the air handling unit in summer and hot water in winter, and provides cold air and hot air to the room through the heat exchanger. The dehumidification coil provides comfortable humidity, and the control valve adjusts the fresh air ratio to improve the indoor carbon dioxide concentration, ultimately maintaining good thermal comfort indoors.

[0042] The influencing parameters of the indoor environment include indoor temperature, supply air temperature, outdoor temperature, supply air flow, cold water flow, indoor humidity, supply air humidity, fresh air ratio, carbon dioxide generation, outdoor humidity, indoor load, wet load, air specific heat, water specific heat, indoor area, unit area, carbon dioxide concentration and inlet and return water temperature difference.

[0043] In step 2, based on the above-mentioned indoor environment influencing parameters, by analyzing the overall working process of the air handling unit and the relevant factors affecting the indoor environment, the air handling unit is modeled according to the laws of thermodynamics and physics as shown in formula (1):

[0044]

[0045] Among them, T t Indicates the indoor temperature, T s Indicates the supply air temperature, T 0 Indicates the outdoor temperature, f a Indicates the air flow rate, f w Indicates the cold water flow rate, w t Indicates indoor humidity, w s represents the supply air humidity, μ represents the fresh air ratio, C g represents the amount of carbon dioxide produced, w 0 Expressing outdoor humidity, Q o Indicates indoor load, M o Indicates wet load, C pa represents the specific heat of air, ρ a represents the specific heat of water, V t Indicates the indoor area, V c Indicates the unit area, C s represents the carbon dioxide concentration, and ΔT represents the inlet and return water temperature difference.

[0046] Formula (1) represents the dynamic model of the air handling unit, defining the state variable x i , input variable u i and the output variable y i for:

[0047] x 1 =w t , x 2 =C s , x 3 =T t , x 4 =T s

[0048] u 1 =f a ,u 2 =1-μ,u 3 =f w

[0049] y 1 =x 1 ,y 2 =x 2 ,y 3 =x 3 (2)

[0050] Therefore, the physical model of the system can be simplified as follows:

[0051]

[0052] To simplify the model, α is introduced 1 , α 2 , α 3 , β 1 , β 2 , β 3 , β 4 and β 5 are all constant quantities, among which

[0053] The parameters related to the air handling unit system model are all physical parameters, which have practical significance and there is no zero parameter. Therefore, α 1 , α 2 , α 3 , β 1 , β 2 , β 3 , β 4 and β 5 is also a non-zero constant.

[0054] In step 3, a gain coefficient is introduced into the air handling unit model to process related unknown parameters; and the specific steps of designing a controller according to the processed air handling unit model are as follows:

[0055] Set the desired humidity, desired CO2 concentration, and desired temperature according to the air handling unit model;

[0056] Introduce gain coefficients and construct the state equation based on the desired humidity, desired CO2 concentration, and desired temperature;

[0057] The controller design is achieved by solving the state variables according to the state equation.

[0058] More specifically, the purpose of air handling unit control is to adjust the control input u i , i = 1, 2, 3, so that the indoor temperature, humidity and carbon dioxide concentration are stable at the expected values. Therefore, in order to achieve the control target, the expected humidity W(t), the expected carbon dioxide concentration C(t) and the expected temperature T(t) are introduced. In practice, they are all continuous and bounded.

[0059] According to the uncertainty of the wet load, the wet load change is assumed to obtain the upper and lower limits of the wet load, and the air handling unit model is constrained according to the upper and lower limits of the wet load. Due to the uncertainty of the indoor wet load caused by the change of the indoor environment, but the wet load change has a certain range, so the following assumptions are made: there is a positive constant M oand and Due to M o The value is uncertain, which leads to α 1 and α 3 Uncertain, it can be deduced that there is and And α 1 and α 3 The upper and lower bounds depend on M o and Then we can get:

[0060]

[0061] In order to make the state variable x i Ability to track expected values ​​and introduce new variables z i The gain L is introduced to process the unknown parameters of the system. According to practical experience, M o The lower and upper limits of , and finally select L to achieve the control target.

[0062] Combining equations (3) and (4), the state equation is transformed into equation (5).

[0063]

[0064] The Lyapunov function is introduced through the backstepping method, and the state variables of the state equation are solved step by step to design the controller. The controller and the air handling unit form a closed-loop system. For the unknown wet load, a high gain is introduced to handle the unknown quantity. The backstepping control method is also called the inversion control method. As the name of the control method suggests, the high-order system is decomposed into multiple first-order systems. The variables of the next level are treated as virtual inputs and act on the first-level system. At the same time, the Lyapunov function is established according to the previous level system to achieve system stability. Until the last system is controlled and the input quantity is obtained. It is guaranteed that under any circumstances, there is a Lyapunov function so that the system can be stable. At the same time, a reference input is found using the function, and finally the derivation and design of the input are realized. This embodiment improves the backstepping method to design a controller that makes the closed-loop system run stably. The specific process includes:

[0065] S1: Consider the state variable z 1 , choose the following Lyapunov function: Obviously, it is positive definite, radially unbounded and continuously differentiable, so V 1 The time derivative of is:

[0066]

[0067] First, deal with the first term on the right side of the above equation.

[0068]

[0069] The gain L is introduced to process the unknown parameters of the system. By combining formula (7), a suitable L value is selected to offset the influence of the unknown parameters on the system control.

[0070] Among them, ε>0 is a very small constant, which can be adjusted according to the control target, and we can get:

[0071]

[0072] Design input signal u 1 for:

[0073]

[0074] where k 1 is a constant greater than zero. Substituting formula (9) into formula (8) yields:

[0075] S2: For the second state variable z 2 , choose the Lyapunov function as:

[0076]

[0077] Formula (5) is simplified to:

[0078]

[0079] Design input signal u 2 for:

[0080]

[0081] where k 2 is a positive design constant. Therefore, Simplified:

[0082]

[0083] S3: For the third state variable z 3 , the Lyapunov function is expressed as: but:

[0084]

[0085] To simplify the calculation, we define therefore:

[0086]

[0087] V3 The derivative is:

[0088]

[0089] The fourth term on the right side of the above inequality is:

[0090]

[0091] The equation is:

[0092]

[0093] Introduce a virtual control signal δ:

[0094]

[0095] where k 3 is a positive design parameter.

[0096] Define ψ=z 4 -δ, then formula (19) is transformed into:

[0097]

[0098] S4: For the fourth state variable z 4 , construct the Lyapunov function as: Taking its derivative we get:

[0099]

[0100] To simplify the calculation, define:

[0101] but:

[0102]

[0103] Formula (22) is transformed into:

[0104]

[0105] Design controller u 3 for:

[0106]

[0107] where k 4 is a positive design parameter. Finally, the final state of the closed-loop system is obtained:

[0108]

[0109] In step 4, the controller is used to control the air handling unit to adjust the indoor temperature, humidity and carbon dioxide concentration. The control effect of the controller is verified based on the assumption of wet load change and Lyapunov stability theorem.

[0110] Specifically, to ensure the stability of the closed-loop system, select the control parameter k i , i = 1, 2, 3, 4 and L, according to Lyapunov's stability theorem and formula (26), k i Must be a positive number. Based on the assumption, we can get α 1 ≤α 1 and α 3 ≤α 3 , select the design parameters and Therefore, we can get:

[0111]

[0112] Let k = min{k i ,i=1,2,3,4}, is a positive number. And formula (27) can be derived:

[0113]

[0114] therefore,

[0115]

[0116] because,

[0117]

[0118] We can get:

[0119]

[0120] ε is a small enough positive constant, then the state of the closed-loop system is close to a very small value. If ε→0, we can get According to formula (4), ε→0, w t , T t and C s It is close to the expected W(t), T(t) and C(t), so the closed-loop system containing the controller in this embodiment has excellent stability.

[0121] Embodiment 2:

[0122] Embodiment 2 of the present invention provides an air handling unit control system when the wet load is unknown, including:

[0123] An influencing factor module is configured to determine influencing parameters of the indoor environment according to a working process of the air handling unit;

[0124] The model building module is configured to model the air handling unit according to the thermodynamic law and the physical law in combination with the influencing parameters of the indoor environment to obtain the air handling unit model;

[0125] The controller design module is configured to introduce a gain coefficient into the air handling unit model to process related unknown parameters; and design a controller according to the processed air handling unit model;

[0126] The control module is configured to adjust the control input size according to the relationship between the control input and related parameters in the controller, thereby achieving control of indoor temperature, humidity and carbon dioxide concentration.

[0127] Embodiment three:

[0128] Embodiment 3 of the present invention provides a medium on which a program is stored. When the program is executed by a processor, the steps of the air handling unit control method under the condition of unknown wet load as described in Embodiment 1 of the present invention are implemented. The steps are:

[0129] Determine the influencing parameters of the indoor environment according to the working process of the air handling unit;

[0130] According to the laws of thermodynamics and physics, the air handling unit is modeled based on the influencing parameters of the indoor environment to obtain an air handling unit model;

[0131] Introduce gain coefficients into the air handling unit model to process related unknown parameters; and design a controller based on the processed air handling unit model;

[0132] The controller is used to control the air handling unit to adjust the indoor temperature, humidity and carbon dioxide concentration.

[0133] The detailed steps are the same as those of the air handling unit control method under the condition of unknown wet load provided in Example 1, and will not be repeated here.

[0134] Embodiment 4:

[0135] Embodiment 4 of the present invention provides a device, including a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, the steps of the air handling unit control method under the condition of unknown wet load as described in Embodiment 1 of the present invention are implemented, and the steps are:

[0136] Determine the influencing parameters of the indoor environment according to the working process of the air handling unit;

[0137] According to the laws of thermodynamics and physics, the air handling unit is modeled based on the influencing parameters of the indoor environment to obtain an air handling unit model;

[0138] Introduce gain coefficients into the air handling unit model to process related unknown parameters; and design a controller based on the processed air handling unit model;

[0139] The controller is used to control the air handling unit to adjust the indoor temperature, humidity and carbon dioxide concentration.

[0140] The detailed steps are the same as those of the air handling unit control method under the condition of unknown wet load provided in Example 1, and will not be repeated here.

[0141] The steps involved in the above embodiments 2, 3 and 4 correspond to the method embodiment 1, and the specific implementation methods can refer to the relevant description part of embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood to include any medium that can store, encode or carry an instruction set for execution by a processor and enable the processor to execute any method in the present invention.

[0142] Those skilled in the art should understand that the modules or steps of the present invention described above can be implemented by a general-purpose computer device, or alternatively, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. The present invention is not limited to any specific combination of hardware and software.

[0143] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A method for controlling an air handling unit when the wet load is unknown, characterized in that: The following steps are involved: Determine the influencing parameters of the indoor environment according to the working process of the air handling unit; According to the laws of thermodynamics and physics, the air handling unit is modeled based on the influencing parameters of the indoor environment to obtain an air handling unit model; The gain coefficient is introduced into the air handling unit model to process the related unknown parameters; and the controller is designed according to the processed air handling unit model. The specific steps are as follows: Set the desired humidity, desired CO2 concentration, and desired temperature according to the air handling unit model; Introduce the gain coefficient and construct the state equation based on the desired humidity, desired carbon dioxide concentration, and desired temperature: in W(t) is the desired humidity, C(t) is the desired carbon dioxide concentration, T(t) is the desired temperature, and w s is the supply air humidity, z1, z2, z3, z4 are state variables, u1, u2, u3 are input variables, T0 is the outdoor temperature, w0 is the outdoor humidity, and L is the gain coefficient; Solve the state variables according to the state equation to achieve controller design; The Lyapunov function is introduced by backstepping method to design the controller by solving the state variables of the state equation in a step-by-step manner; According to the relationship between the control input and related parameters in the controller, the control input size is adjusted to achieve control of indoor temperature, humidity and carbon dioxide concentration.

2. The air handling unit control method under unknown wet load condition according to claim 1, characterized in that: The air handling unit includes air dampers, control valves, filters, cooling coils, dehumidifiers and supply and return air fans.

3. The air handling unit control method under unknown wet load condition according to claim 1, characterized in that: The influencing parameters of the indoor environment include indoor temperature, supply air temperature, outdoor temperature, supply air flow, cold water flow, indoor humidity, supply air humidity, fresh air ratio, carbon dioxide generation, outdoor humidity, indoor load, wet load, air specific heat, water specific heat, indoor area, unit area, carbon dioxide concentration and inlet and return water temperature difference.

4. The air handling unit control method under unknown wet load condition according to claim 1, characterized in that: According to the uncertainty of the wet load, the wet load change is assumed to obtain the upper and lower limits of the wet load, and the air handling unit model is constrained according to the upper and lower limits of the wet load.

5. The air handling unit control method under unknown wet load condition according to claim 4, characterized in that: The control effect of the controller is verified based on the assumptions about wet load variation and Lyapunov stability theorem.

6. A control system for an air handling unit with unknown wet load, characterized in that: include: An influencing factor module is configured to determine influencing parameters of the indoor environment according to a working process of the air handling unit; The model building module is configured to model the air handling unit according to the thermodynamic law and the physical law in combination with the influencing parameters of the indoor environment to obtain the air handling unit model; The controller design module is configured to introduce a gain coefficient to the air handling unit model to process related unknown parameters; and design a controller according to the processed air handling unit model, and the specific steps are: Set the desired humidity, desired CO2 concentration, and desired temperature according to the air handling unit model; Introduce the gain coefficient and construct the state equation based on the desired humidity, desired carbon dioxide concentration, and desired temperature: in W(t) is the desired humidity, C(t) is the desired carbon dioxide concentration, T(t) is the desired temperature, and w s is the supply air humidity, z1, z2, z3, z4 are state variables, u1, u2, u3 are input variables, T0 is the outdoor temperature, w0 is the outdoor humidity, and L is the gain coefficient; Solve the state variables according to the state equation to achieve controller design; The Lyapunov function is introduced by backstepping method to design the controller by solving the state variables of the state equation in a step-by-step manner; The control module is configured to adjust the control input size according to the relationship between the control input and related parameters in the controller, thereby achieving control of indoor temperature, humidity and carbon dioxide concentration.

7. A computer-readable storage medium, characterized in that: A plurality of instructions are stored therein, and the instructions are suitable for being loaded by a processor of a terminal device and executed by the air handling unit control method under the condition of unknown wet load as described in any one of claims 1-5.

8. A terminal device, characterized in that: It includes a processor and a computer-readable storage medium, the processor is used to implement various instructions; the computer-readable storage medium is used to store multiple instructions, and the instructions are suitable for being loaded by the processor and executing the air handling unit control method under the condition of unknown wet load described in any one of claims 1-5.

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