A combined air conditioning unit constant temperature and humidity automatic control system

Abstract

The application discloses a combined air conditioning unit constant temperature and humidity automatic control system, which is used for the combined air conditioning unit, and the control system comprises two closed loop control circuits, namely a temperature control loop and a humidity control loop. The temperature control loop comprises a return air temperature PID controller, a high-temperature water valve actuator, a fan frequency converter, an ambient temperature sensor and a return air temperature sensor. The humidity control loop comprises a return air humidity PID controller, a normal-temperature water valve actuator and a return air humidity sensor. The temperature control loop and the humidity control loop are interactively connected through a temperature feedforward decoupler and a humidity feedforward decoupler respectively. The combined air conditioning unit based control system can realize precise constant temperature and humidity adjustment control while saving energy in some areas.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of air conditioning unit control, in particular to a combined air conditioning unit constant temperature and humidity automatic control system. BACKGROUND

[0002] At present, the air handling unit of the combined air conditioning system mostly adopts air internal circulation to meet the temperature and humidity requirements of the target area, and the common automatic control mode includes using the return air temperature of the return air section of the unit as a reference to adjust the opening size of the water valve of the cooling coil, so as to adjust the output of the cooling capacity and ensure the environmental temperature of the large space area. When the return air temperature value is used as feedback to adjust the cooling capacity of the target area, the temperature adjustment period is relatively long due to the long air circulation loop. The return air temperature value can better and stably ensure the environmental temperature of the target area when controlling the opening size of the water valve of the cooling coil to control the air temperature, so that the temperature control reaches a stable level, and the humidity in the air can be adjusted to a certain extent, so that the target area is at a more appropriate temperature and humidity level. However, for the southern region with humid climate and frequent summer rainstorms, simply relying on the return air temperature value to adjust the temperature and humidity is difficult to ensure the temperature of the target area while meeting the environmental humidity conditions of the national standards. In actual operation, there are often some areas that are suitable in temperature but very "stuffy", which shows that the traditional air conditioning unit control method is not suitable for target areas with high air environmental conditions, and therefore it is relatively important to ensure the temperature while ensuring the humidity.

[0003] At present, the common dehumidification methods on the market include heating dehumidification and cooling dehumidification.

[0004] For target areas with high air environmental conditions, such as information and weak current machine rooms, heating dehumidification is usually used after the supply air temperature is greatly reduced, so as to meet the air humidity requirements of the target area. Heating dehumidification is to increase a section of cooling capacity and then sacrifice part of the cooling capacity to ensure that the temperature and humidity can meet the air environmental condition requirements of the target area, but this method does not meet the requirements of energy saving and consumption reduction.

[0005] The temperature and humidity control system is used for the combined air conditioning unit, and the control system comprises two closed-loop control circuits of a temperature control circuit and a humidity control circuit. SUMMARY

[0006] To solve the above problems, the application provides a combined air conditioning unit constant temperature and humidity automatic control system to solve the problem that the temperature and humidity of a large space environment area cannot meet the design standard requirements in the prior art.

[0007] The application provides a combined air conditioning unit constant temperature and humidity automatic control system, and the specific technical scheme is as follows.

[0008] The control system is used for the combined air conditioning unit, and the control system comprises two closed-loop control circuits of a temperature control circuit and a humidity control circuit.

[0009] The temperature control circuit comprises a return air temperature PID controller, a high-temperature water valve actuator, a fan frequency converter, an environment temperature sensor and a return air temperature sensor. The PID controller controls the output of the high-temperature water valve opening degree and the fan frequency.

[0010] The humidity control loop comprises a return air humidity PID controller, a constant temperature water valve actuator and a return air humidity sensor; the return air humidity PID controller drives the opening degree of the electric two-way valve on the constant temperature secondary coil through the constant temperature water valve actuator;

[0011] The temperature control loop and the humidity control loop are respectively connected through a temperature feedforward decoupler and a humidity feedforward decoupler.

[0012] Further, the transfer function of the temperature feedforward decoupler is as follows:

[0013]

[0014] Wherein, G 11 (s) represents the current environment temperature control channel transfer function, G 12 (s) represents the humidity control coupling channel transfer function affected by temperature.

[0015] Further, the transfer function of the humidity feedforward decoupler is as follows:

[0016]

[0017] Wherein, G 22 (s) represents the humidity control channel transfer function, G 21 (s) represents the temperature control coupling channel transfer function affected by humidity.

[0018] Further, the transfer function model of the system is as follows:

[0019]

[0020] Wherein, K represents the amplification coefficient of the regulation area, T represents the inertial time constant of the regulation area, and τ represents the time delay of the regulation area.

[0021] Further, the control system further comprises a BP neural network, and the BP neural network is used for adaptively adjusting the control parameters K P , T I , T d , wherein K P represents the proportional coefficient in the PID logic loop, T i represents the differential time in the PID logic loop, and T d represents the integral time in the PID logic loop.

[0022] Further, the control system further optimizes the BP neural network through an SSA algorithm, and the specific process is as follows:

[0023] Based on the network structure of BP neural network, the network weight is initialized, and the corresponding learning rate is set.

[0024] Given the temperature and humidity input, the three control parameters K P 、T I 、T d of the PID controller are obtained by optimizing the SSA algorithm.

[0025] The system error e is used as the training index of the SSA optimization algorithm for network training and parameter setting.

[0026] The beneficial effects of the present application are as follows:

[0027] The control system of the present application utilizes PID and feedforward decoupling to achieve constant temperature and humidity control, and realizes a combined air conditioning unit based on two-stage heat exchange coil. In the area where temperature and humidity are not coordinated, the temperature is reduced to the set value, and the humidity reaches the set value without wasting cold energy and energy consumption, realizing simultaneous regulation of constant temperature and humidity. At the same time, the system eliminates the interference of the coupling relationship between temperature and humidity through pre-decoupling, realizing independent closed-loop regulation and control of temperature and humidity.

[0028] The control system also introduces BP neural network, which automatically models the system according to historical operation data for different field environments, and adaptively adjusts the control parameters of the PID controller. The BP neural network is also optimized by SSA algorithm to realize adaptive adjustment of control parameters in different processing areas and automatic optimization. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a schematic diagram of the logic structure of the control system;

[0030] Figure 2 is a schematic diagram of the feedforward controller structure;

[0031] Figure 3 is a schematic diagram of the control system architecture;

[0032] Figure 4 is a high-temperature water valve fan segmented control diagram;

[0033] Figure 5 is a combined air conditioning unit sensor and controller distribution diagram. DETAILED DESCRIPTION

[0034] In the following description, the technical solutions in the embodiments of the present application are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0035] In the description of the embodiments of the present application, it should be noted that the indicated position or positional relationship is based on the position or positional relationship shown in the drawings, or the position or positional relationship commonly used when the product of the present application is used, or the position or positional relationship commonly understood by those skilled in the art, or the position or positional relationship commonly used when the product of the present application is used, only for the convenience of describing the present application and simplifying the description, and is not intended to indicate or imply that the indicated device or element must have a particular position, be constructed and operated in a particular position, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first", "second" are only used for differentiation and cannot be understood as indicating or implying relative importance.

[0036] In the description of the embodiments of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "set", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0037] Embodiment 1

[0038] Embodiment 1 of the present application discloses a combined air conditioning unit constant temperature and humidity automatic control system, the control system is used for a combined air conditioning unit, such as Figure 5 As shown, the combined air conditioning unit includes a fan unit, a two-stage cooling unit and a plurality of temperature sensors and humidity sensors;

[0039] The fan unit includes a fan group, a fan air supply section, the fan air supply section communicates with an air conditioning area, and the air conditioning area and the fan air supply section are provided with temperature sensors and humidity sensors;

[0040] The two-stage cooling unit includes a two-stage cooling unit and a corresponding connected cooling coil, including a high-temperature first coil and a normal-temperature second coil, and an electric two-way valve is arranged on each cooling coil, and first temperature chilled water and second temperature chilled water are respectively supplied in the pipes;

[0041] In this embodiment, the temperature of the first temperature chilled water is 15-21℃, and the temperature of the second temperature chilled water is 7-12℃, and the chilled water temperature can be set according to the current regional environment, which is not limited here.

[0042] The air conditioning area is connected to the two-stage cooling coil through a return air section, and the return air section is provided with temperature sensors and humidity sensors.

[0043] Based on the above combined air conditioning unit, the general constant temperature and humidity control is to compare the return air temperature feedback value with the set value, to adjust the opening of the electric two-way valve on the single-stage cooling coil return water pipeline according to the deviation value of the two to adjust the cooling capacity, and to ensure that the environmental temperature in the target area is maintained at the return air temperature set value.

[0044] Meanwhile, the air conditioning temperature and humidity control system is a large time-delay, time-varying, nonlinear and strongly coupled multivariable system, and there is strong coupling between temperature and humidity. The temperature and humidity control loops interfere with each other. In order to make the system stable on the basis of reaching the set value and improve the utilization rate of the system, the control system of the embodiment independently controls the temperature and humidity through temperature and humidity feedforward decoupling and SSA-BP-PID algorithm.

[0045] As shown in Figure 1 , the specific implementation is as follows:

[0046] The control system includes a temperature control loop and a humidity control loop, two closed-loop control loops.

[0047] The temperature control loop includes a return air temperature PID controller, a high-temperature water valve actuator, a fan frequency converter, an environmental temperature sensor and a return air temperature sensor.

[0048] The humidity control loop includes a return air humidity PID controller, a constant temperature water valve actuator and a return air humidity sensor.

[0049] The high-temperature water valve actuator and the constant-temperature water valve actuator are connected with the electric two-way valve of the combined air conditioning unit, and respectively control the opening of the electric two-way valve on the high-temperature primary coil and the constant-temperature secondary coil.

[0050] The return air temperature sensor and the return air humidity sensor are respectively arranged in the return air section of the combined air conditioning unit, and are respectively used for detecting the return air temperature and the return air humidity.

[0051] The environmental temperature sensor is arranged in the target area of the air conditioner service, and is used for detecting the environmental temperature of the target area.

[0052] The temperature control loop and the humidity control loop are respectively connected through a temperature feedforward decoupler and a humidity feedforward decoupler.

[0053] In the embodiment, the structure of the temperature feedforward decoupler and the humidity feedforward decoupler can be adaptively adjusted according to different environments.

[0054] Specifically, the system mathematical model transfer function is determined, as shown below:

[0055]

[0056] Wherein, K represents the amplification factor of the adjustment area, T represents the inertia time constant of the adjustment area, τ represents the time delay of the adjustment area;

[0057] According to the operation data and historical data of the combined air conditioning unit, K, T and τ are identified by the least square method after smoothing processing, and the current environment temperature control channel transfer function, the humidity control channel transfer function, the temperature control coupling channel transfer function on humidity, and the humidity control coupling channel transfer function on temperature are obtained.

[0058] In this embodiment, the transfer function of the temperature feedforward decoupler is represented as follows:

[0059]

[0060] In this embodiment, the transfer function of the humidity feedforward decoupler is represented as follows:

[0061]

[0062] Wherein, G 11 (s) represents the current environment temperature control channel transfer function, G 22 (s) represents the humidity control channel transfer function, G 21 (s) represents the temperature control coupling channel transfer function on humidity, and G 12 (s) represents the humidity control coupling channel transfer function on temperature.

[0063] According to the transfer functions of the temperature feedforward decoupler and the humidity feedforward decoupler, the structure of the feedforward decoupler is determined, as shown in Figure 2 .

[0064] The temperature control loop detects the return air temperature and the service area environment temperature in real time. In order to reduce the influence of sensor measurement error and actual installation position, the actual temperature of the service area is truly represented, and the detected return air temperature feedback value is compared with the environment temperature feedback value. That is, when the difference between the detected return air temperature feedback value and the service area environment temperature feedback value is less than 1℃, the return air temperature is taken as the actual temperature feedback value; when the difference between the detected return air temperature feedback value and the service area environment temperature feedback value is greater than 1℃, the environment temperature is taken as the actual temperature feedback value. According to the deviation between the actual temperature feedback value and the temperature set value, PID calculation is performed. Considering the strong coupling between the temperature control loop and the humidity control loop, temperature and humidity decoupling is performed by increasing the feedforward decoupler, and then the PID controller output is accumulated to adjust the electric two-way water valve opening degree on the high-temperature primary coil (pre-cooling) return water pipe and the fan frequency. Considering the actual heat exchange capacity and energy consumption comparison of the high-temperature primary coil (pre-cooling) and the fan, the high-temperature water valve opening degree and the fan frequency are controlled correspondingly in sections, as shown in Figure 4As shown, the PID output of 0-75% part adjusts the high temperature water valve opening, 75%-80% is the adjustment dead zone, that is, the PID control buffer area, and the PID output of 80%-100% part adjusts the fan supply air volume, and the actual set frequency upper and lower limits are used as the adjustment range. The cooling coil section air-water heat exchange capacity is adjusted to ensure that the actual temperature feedback value is stable near the return air temperature set value.

[0065] The humidity control loop detects the return air humidity in real time, performs PID calculation according to the deviation of the return air humidity feedback value and the set value, adds the output of the feedforward decoupler, and adjusts the opening of the electric two-way water valve on the constant temperature secondary coil (recooling) return water pipe. The temperature adjustment capacity is increased while providing stable humidity.

[0066] In this embodiment, the control system further comprises a BP neural network, which adaptively adjusts the PID controller control parameters K P , T I , T d ; the feedforward decoupler is combined with the BP-PID controller to form a closed loop control, so that the temperature and humidity of the air conditioning room can be stably output within a specified range, and the required control effect of the system is achieved.

[0067] In this embodiment, the SSA algorithm is also used to optimize the BP-PID controller to solve the problem that the BP neural network is easy to fall into local extreme value, and further improve the control accuracy of the temperature and relative humidity of the air conditioning room;

[0068] The specific process is as follows:

[0069] Based on the network structure of the BP neural network, the network weight is initialized, and the corresponding learning rate is set;

[0070] Given the temperature and humidity input, the three control parameters K P , T I , T d of the PID controller are obtained by optimization of the SSA algorithm, and the control law is calculated according to the incremental PID algorithm;

[0071] The system error e is used as the training index of the SSA optimization algorithm for network training and parameter setting.

[0072] As Figure 3 shown, in this embodiment, the control system further comprises a PLC controller, a system switch, a system upper computer workstation, a control algorithm integrated server, a system server, a system client and a VPN router.

[0073] The PLC controller is connected with a PID controller and a temperature and humidity sensor, receives temperature and humidity sensor data and uploads the data to a system server in real time through a network, the system server saves the data to a historical database and a real-time database for reading by a user interface, the system server provides functions of system configuration, control program writing, user interface configuration and the like, and has a data docking function for external systems.

[0074] A VPN router is additionally arranged to facilitate external access in consideration of the independent networking requirement of the user system.

[0075] Considering the limited computing and data storage capacity of the PLC controller in the air conditioning unit, the control algorithm integration server is used to calculate the control parameters in the current environment in real time and send them to the PLC controller, so as to ensure the real-time response of the system.

[0076] The present application is not limited to the foregoing specific embodiments. The present application extends to any novel one, or any new combination, of the characteristics disclosed in this specification, as well as to any novel method or process steps disclosed, or any new combination thereof.

Claims

1. A constant temperature and humidity automatic control system for a combined air-conditioning unit, characterized in that: For combined air conditioning units, the control system includes two closed-loop control loops: temperature control loop and humidity control loop; The temperature control loop includes a return air temperature PID controller, a high temperature water valve actuator, a fan frequency converter, an ambient temperature sensor, and a return air temperature sensor; The humidity control loop includes a return air humidity PID controller, a normal temperature water valve actuator and a return air humidity sensor; The two-stage surface cooler unit includes two-stage surface coolers and corresponding surface cooling coils, including a high-temperature primary coil and a normal-temperature secondary coil. The surface cooling coils are equipped with electric two-way valves, and the pipes are respectively supplied with chilled water of the first temperature and the second temperature. The temperature control loop and the humidity control loop are interconnected via a temperature feedforward decoupler and a humidity feedforward decoupler respectively; The high-temperature water valve actuator and the normal-temperature water valve actuator are connected to the electric two-way valve of the combined air-conditioning unit to control the opening of the electric two-way valve on the high-temperature primary coil and the normal-temperature secondary coil, respectively; the humidity control loop detects the return air humidity in real time, performs PID calculation based on the deviation between the return air humidity feedback value and the set value, and adjusts the opening of the electric two-way water valve on the return water pipe of the normal-temperature secondary coil after accumulating the calculated value with the output of the feedforward decoupler; The control system also includes a BP neural network, which adaptively adjusts the PID controller control parameters KP, Ti, and Td through the BP neural network, and combines the feedforward decoupler with the BP-PID controller to form a closed-loop control, wherein KP represents the proportional coefficient in the PID logic loop, Ti represents the differential time in the PID logic loop, and Td represents the integral time in the PID logic loop; the control system also uses an SSA algorithm to optimize the BP neural network; The output of the PID controller is allocated corresponding control quantities according to the high-temperature water valve opening and the fan frequency; the high-temperature water valve opening is adjusted with the first 0-75% part of the PID, 75%-80% is the adjustment dead zone, that is, the PID control buffer area, and the last 80%-100% part of the PID adjusts the fan air supply.

2. The constant temperature and humidity automatic control system for a combined air-conditioning unit according to claim 1, characterized in that: The transfer function of the temperature feedforward decoupler is expressed as follows: Among them, G 11 (s) represents the current ambient temperature control channel transfer function, G 12 (s) represents the coupled channel transfer function of the effect of humidity control on temperature.

3. The constant temperature and humidity automatic control system for a combined air-conditioning unit according to claim 1, characterized in that: The transfer function of the humidity feedforward decoupler is expressed as follows: Among them, G 22 (s) represents the humidity control channel transfer function, G 21 (s) represents the coupled channel transfer function of the effect of temperature control on humidity.

4. The constant temperature and humidity automatic control system for a combined air-conditioning unit according to any one of claims 2-3, characterized in that: The transfer function model of the system is expressed as follows: Wherein, K represents the amplification factor of the adjustment area, T represents the inertia time constant of the adjustment area, and τ represents the time lag time of the adjustment area.

5. The constant temperature and humidity automatic control system for a combined air-conditioning unit according to claim 1, characterized in that: The BP neural network is optimized, and the specific process is as follows: Based on the network structure of BP neural network, initialize the network weights and set the corresponding learning rate; Given the temperature and humidity input, the three control parameters K of the PID controller are obtained by SSA algorithm optimization: P 、T i 、T d ; The system error e is used as the training indicator of the SSA optimization algorithm for network training and parameter tuning.

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