Closed-loop control system and closed-loop control method based on EC fan

Abstract

The invention discloses a closed-loop control system and method based on an EC draught fan, and the system comprises a controller which is used for data processing, algorithm calculation and PWM control signal generation; an EC controller is arranged in the EC fan, and the rotating speed of the EC controller is adjusted according to the received PWM signals; the sensor group comprises a differential pressure sensor and a temperature sensor and is used for monitoring state parameters of a working system formed by the EC fan in real time; the communication module is used for realizing data interaction between the controller and the EC controller as well as between the controller and the sensor group; in the working process, feedback data of the sensor set and a set target control value serve as input of the controller, a PWM control signal is generated through calculation of a PID control algorithm, the generated PWM control signal is sent to the EC controller to be used for controlling the rotating speed of an EC fan, and a constant-air-volume, constant-static-pressure or constant-temperature control mode is achieved. According to the invention, a PID algorithm and a PWM speed regulation technology can be combined, multi-mode, high-precision and remotely controllable closed-loop control is realized, the control effect is good, and the cost is low.

Description

Technical Field

[0001] The present application relates to the technical field of heating, ventilation and air conditioning and cooling tower control, and in particular to a closed-loop control system and a closed-loop control method based on an EC fan. Background Art

[0002] An AHU (Air Handling Unit) is the core equipment in a building's ventilation and air conditioning system. It processes air (such as heating, cooling, humidifying, filtering, and dehumidifying) and distributes the treated air to various areas of the building (such as offices and shopping malls), while also recovering energy from the exhaust air. A CT (Cooling Tower) is a key component of the refrigeration system. Through heat exchange between water and air, it dissipates heat from circulating cooling water into the atmosphere, providing low-temperature cooling water for equipment such as chillers. It is commonly used in refrigeration cycles in commercial buildings, data centers, and other settings.

[0003] In an AHU or CT, a "fan wall" refers to an air supply / exhaust system consisting of multiple small fans connected in parallel. In an AHU, the fan wall delivers treated air into the building or extracts exhaust air from it. In a CT, the fan wall accelerates heat exchange between the water and air in the cooling tower through forced air flow (such as exhaust or forced draft), improving heat dissipation efficiency. Compared to the traditional "single large fan" design, the advantages of a fan wall include: Redundancy: When a single fan fails, the other fans can still maintain basic functions; Energy saving: When the load is partial, some fans can be turned off to reduce energy consumption; Low noise: small fans usually have lower speed and less noise; Easy to maintain: A single fan is small in size and light in weight, making replacement / repair more convenient.

[0004] In traditional fan control systems, fans in a fan wall often use fixed-frequency control or open-loop speed regulation, which has the following drawbacks: High energy consumption: The speed cannot be adjusted dynamically according to actual needs, resulting in energy waste; Low control accuracy: large fluctuations in static pressure, air volume or temperature affect environmental comfort; Poor scalability: The hardware interface is rigid and difficult to be compatible with different application scenarios. Summary of the Invention

[0005] The purpose of this application is to overcome the above problems or at least partially solve or alleviate the above problems.

[0006] According to one aspect of the present application, a closed-loop control system based on an EC fan is provided, comprising: Controller, used for data processing, algorithm calculation and generation of PWM control signals; EC fans have a built-in EC controller that adjusts the speed based on the received PWM signal; A sensor group, including a differential pressure sensor and a temperature sensor, is used to monitor the status parameters of the working system composed of the EC fan in real time; A communication module, used to realize data exchange between the controller, the EC controller and the sensor group; The controller uses the feedback data of the sensor group and the set target control value as input, calculates and generates a PWM control signal through a PID control algorithm, and sends the generated PWM control signal to the EC controller for controlling the speed of the EC fan to achieve constant air volume, constant static pressure or constant temperature control mode.

[0007] Optionally, the controller includes: a microprocessor unit configured to execute a PID control algorithm to calculate a duty cycle of the PWM control signal; The PWM generation unit outputs a PWM control signal with an adjustable duty cycle, and outputs a corresponding PWM signal according to the duty cycle calculated by the microprocessor unit.

[0008] Optionally, the closed-loop control system further includes a lower computer, the communication module is arranged in the lower computer, and the lower computer is provided with a Mod-bus remote control interface, and is connected to a remote server via the Mod-bus remote control interface.

[0009] Optionally, the PID control algorithm is implemented as follows: In constant air volume mode, the difference between the set air volume and the actual air volume obtained by collection and calculation is used as the input error; In the constant static pressure mode, the difference between the set static pressure and the actual static pressure obtained is used as the input error; In constant temperature mode, the difference between the set temperature and the actual temperature obtained is used as the input error; The PID control algorithm calculates the PWM duty cycle by adjusting the proportional, integral, and differential parameters according to the input error, and then generates a PWM signal with a corresponding duty cycle as a PWM control signal.

[0010] Furthermore, the sensor group includes a differential pressure sensor and a temperature sensor, wherein: The differential pressure sensor is provided on the air guide ring of the EC fan and is used to determine the difference between the air inlet of the EC fan and the standard atmospheric pressure, so as to realize the constant static pressure mode or constant air volume mode of the system; The temperature sensor is installed in the material or environment to be cooled, and is used to realize the constant temperature mode of the system according to the difference between the feedback data of the temperature change and the set temperature.

[0011] Furthermore, the constant static pressure mode or the constant air volume mode is applied to an air handling unit, and the constant temperature reading mode is applied to a cooling tower.

[0012] Optionally, the EC fan achieves stepless speed regulation by adjusting the PWM duty cycle, and the speed regulation range is 20%-100% of the rated speed of the EC fan.

[0013] In particular, the present application also provides a closed-loop control method based on an EC fan, which comprises the following steps: S1: Initialize system parameters and set target control values; S2: The sensor group collects pressure difference or temperature data in real time; S3: The controller calculates the difference between the feedback data of the sensor group and the target control value and uses the difference as input to calculate the PWM duty cycle through the PID control algorithm and generate a PWM control signal; S4: The EC fan adjusts its speed according to the PWM control signal; S5: Execute S2-S4 in a loop until the target control value is reached.

[0014] Optionally, the mathematical model of the PID control algorithm is:

[0015] in, is the PWM duty cycle, is the error between the target control value and the feedback data, i.e., the actual value.

[0016] Compared with the prior art, the closed-loop control system and closed-loop control method based on EC fans provided in this application have the following beneficial effects or advantages: This paper provides a multi-mode, high-precision, remotely controllable closed-loop control system and method that can combine PID algorithm and PWM speed regulation technology to achieve multi-mode dynamic control. Specific beneficial effects may include: Multi-mode adaptive control: For AHUs, constant air volume control, constant static pressure control, and PWM independent control modes are available to meet different application requirements. For cooling towers (CTs), constant temperature control is available. Each control mode is independent of the others, covering the different needs of AHUs and CTs and improving system flexibility. High-precision control: PID algorithm combined with PWM speed regulation achieves ±2% air volume / static pressure accuracy and ±0.5℃ temperature control; Remote maintainability: Modbus interface supports remote parameter adjustment, reducing maintenance costs; Energy-saving and high efficiency: EC fan has stepless speed regulation, which saves more than 30% energy compared with traditional three-speed control.

[0017] Based on the detailed description of the specific embodiments of the present application in conjunction with the accompanying drawings below, those skilled in the art will become more aware of the above and other objects, advantages and features of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Hereinafter, some specific embodiments of the present application will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 1 is a schematic diagram of the framework structure of a closed-loop control system according to an embodiment of the present application; Figure 2 It is a schematic diagram of the working principle of a closed-loop control method according to an embodiment of the present application. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0020] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] This embodiment describes a closed-loop control system based on an EC fan, such as Figure 1 As shown, it includes: Controller, used for data processing, algorithm calculation and generation of PWM control signals; EC fans have a built-in EC controller that adjusts the speed based on the received PWM signal; A sensor group, including a differential pressure sensor and a temperature sensor, is used to monitor the status parameters of the working system composed of the EC fan in real time; A communication module, used to realize data exchange between the controller, the EC controller and the sensor group; The controller uses the feedback data of the sensor group and the set target control value as input, calculates and generates a PWM control signal through a PID control algorithm, and sends the generated PWM control signal to the EC controller for controlling the speed of the EC fan to achieve constant air volume, constant static pressure or constant temperature control mode.

[0022] The closed-loop control system of the present application has the following beneficial effects compared to the prior art: EC fan drive: Using EC fan as the actuator, the built-in intelligent controller (EC controller) is used to achieve precise speed control, fast response and strong anti-interference ability; PWM control: The speed of the EC fan is controlled through pulse width modulation (PWM) technology. PWM is a technology that uses the digital output of a microprocessor to control analog circuits. It is suitable for scenarios that require frequent speed adjustment, such as constant air volume control and constant static pressure control. Feedback control: Use sensors (such as differential pressure sensors and temperature sensors) to monitor the system status in real time and feed the data back to the controller; Control algorithm: Based on feedback data, an advanced PID control algorithm is used to calculate the optimal PWM signal; Multi-mode control: Multiple control modes are integrated to suit various application scenarios. For AHUs, constant air volume control, constant static pressure control, and independent PWM control modes are available to meet different application requirements. For cooling towers (CTs), constant temperature control is available. Each control mode is independent of the others.

[0023] Based on the above system, such as Figure 2 As shown, the closed-loop control method during the working process can generally include the following working steps: S1: Initialize system parameters and set target control values; S2: The sensor group collects pressure difference or temperature data in real time; S3: The controller calculates the difference between the feedback data of the sensor group and the target control value and uses the difference as input to calculate the PWM duty cycle through the PID control algorithm and generate a PWM control signal; S4: The EC fan adjusts its speed according to the PWM control signal; S5: Execute S2-S4 in a loop until the target control value is reached.

[0024] Among them, the mathematical model of the PID control algorithm is:

[0025] in, is the PWM duty cycle, is the error between the target control value and the feedback data, i.e., the actual value.

[0026] The PID control algorithm is implemented as follows: In constant air volume mode, the difference between the set air volume and the actual air volume obtained by collection and calculation is used as the input error; In the constant static pressure mode, the difference between the set static pressure and the actual static pressure obtained is used as the input error; In constant temperature mode, the difference between the set temperature and the actual temperature obtained is used as the input error; The PID control algorithm calculates the PWM duty cycle by adjusting the proportional, integral, and differential parameters according to the input error, and then generates a PWM signal with a corresponding duty cycle as a PWM control signal.

[0027] like Figure 2 As shown in the figure, the working principle of the fan closed-loop control system in the AHU generally includes the following steps: The sensor group monitors the pressure difference parameters in real time; The controller receives the feedback data collected by the sensor group in real time and compares it with the set target control value; The controller calculates the duty cycle of the PWM control signal according to the PID control algorithm and generates the corresponding PWM control signal; The EC controller of the EC fan receives the PWM control signal, i.e., adjusts the speed of the EC fan according to the PWM control signal; EC fans adjust their speed to change the pressure difference in the AHU system; The above steps are executed cyclically to realize closed-loop feedback control.

[0028] like Figure 2 As shown, the working principle of the fan closed-loop control system in CT generally includes the following steps: The sensor group monitors water temperature parameters in real time; The controller receives the feedback data collected by the sensor group in real time and compares it with the set target control value; The controller calculates the duty cycle of the PWM control signal according to the PID control algorithm and generates the corresponding PWM control signal; The EC controller of the EC fan receives the PWM control signal, i.e., adjusts the speed of the EC fan according to the PWM control signal; The EC fan adjusts its speed to change the temperature of the CT system; The above steps are executed cyclically to realize closed-loop feedback control.

[0029] In one embodiment, the controller includes: a microprocessor unit configured to execute a PID control algorithm to calculate a duty cycle of the PWM control signal; The PWM generation unit outputs a PWM control signal with an adjustable duty cycle, and outputs a corresponding PWM signal according to the duty cycle calculated by the microprocessor unit.

[0030] In another optimized implementation, the closed-loop control system further includes a lower computer, the communication module is arranged in the lower computer, and the lower computer is provided with a Mod-bus remote control interface, and is connected to a remote server via the Mod-bus remote control interface.

[0031] In one embodiment, the sensor group includes a differential pressure sensor and a temperature sensor, wherein: The differential pressure sensor is provided on the air guide ring of the EC fan and is used to determine the difference between the air inlet of the EC fan and the standard atmospheric pressure, so as to realize the constant static pressure mode or constant air volume mode of the system; The temperature sensor is installed in the material or environment to be cooled, and is used to realize the constant temperature mode of the system according to the difference between the feedback data of the temperature change and the set temperature.

[0032] Optionally, the constant static pressure mode or the constant air volume mode is applied to an air handling unit, and the constant temperature reading mode is applied to a cooling tower.

[0033] Optionally, the EC fan achieves stepless speed regulation by adjusting the PWM duty cycle, and the speed regulation range is 20%-100% of the rated speed of the EC fan.

[0034] Based on the above embodiments, it can be seen that the EC fan-based closed-loop control system and closed-loop control method of the present application are suitable for two application scenarios: AHU (air conditioning unit) and CT (cooling tower). In the AHU application scenario, two control modes are available: constant static pressure mode and constant air volume mode. In the cooling tower application scenario, a constant temperature mode can be used. Only one of the three control modes, constant static pressure mode, constant air volume mode, and constant temperature mode, is active at any one time. These modes are independent of each other and do not affect or interfere with each other. During control, an error value is calculated by subtracting the user's set values ​​(temperature, air volume, static pressure) from the current values ​​actually measured by the sensors. The current total air volume value is calculated based on the static pressure ΔPw, the current air density ρs, the standard air density ρ, the fan k factor (which varies for each fan and is obtained from a table), the number of installed units n, and the correction factor c. The error value is used as the PID input (only one input is allowed at the same time depending on the control mode). The traditional PID control algorithm is used to calculate the output PWM signal to control the fan speed. It includes three steps: proportional, integral, and differential. By adjusting the parameters, precise control can be achieved to continuously approach the user's set value.

[0035] Taking the constant static pressure mode for AHU control as an example, the working process is as follows: 1. Set the target static pressure P_set.

[0036] 2. Read the actual feedback voltage V_actual (0-5 VDC) from the differential pressure sensor. The differential pressure sensor has a range of 0-2000 Pa. The feedback voltage is proportional to the differential pressure. Static pressure P_actual = V_actual / 5*2000.

[0037] 3. Calculate the pressure difference deviation e = P_set - P_actual.

[0038] 4. Calculate the duty cycle of the PWM signal according to the PID algorithm:

[0039] Generate PWM signal to control the speed of EC fan.

[0040] 6. Repeat the above steps until the target static pressure is reached.

[0041] The working process of constant air volume mode and constant temperature mode is similar to this, except that the collected feedback data and the set target control values ​​are different.

[0042] The above description is merely a preferred embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A closed-loop control system based on EC fans, characterized in that: include: Controller, used for data processing, algorithm calculation and generation of PWM control signals; EC fans have a built-in EC controller that adjusts the speed based on the received PWM signal; A sensor group, including a differential pressure sensor and a temperature sensor, is used to monitor the status parameters of the working system composed of the EC fan in real time; A communication module, used to realize data exchange between the controller, the EC controller and the sensor group; The controller uses the feedback data of the sensor group and the set target control value as input, calculates and generates a PWM control signal through a PID control algorithm, and sends the generated PWM control signal to the EC controller for controlling the speed of the EC fan to achieve constant air volume, constant static pressure or constant temperature control mode.

2. The closed-loop control system according to claim 1, characterized in that: The controller includes: a microprocessor unit configured to execute a PID control algorithm to calculate a duty cycle of the PWM control signal; The PWM generation unit outputs a PWM control signal with an adjustable duty cycle, and outputs a corresponding PWM signal according to the duty cycle calculated by the microprocessor unit.

3. The closed-loop control system according to claim 1 or 2, characterized in that: It also includes a lower computer, the communication module is arranged in the lower computer, and the lower computer is provided with a Mod-bus remote control interface, and is connected to a remote server through the Mod-bus remote control interface.

4. The closed-loop control system according to claim 1 or 2, characterized in that: The PID control algorithm is implemented as follows: In constant air volume mode, the difference between the set air volume and the actual air volume obtained by collection and calculation is used as the input error; In the constant static pressure mode, the difference between the set static pressure and the actual static pressure obtained is used as the input error; In constant temperature mode, the difference between the set temperature and the actual temperature obtained is used as the input error; The PID control algorithm calculates the PWM duty cycle by adjusting the proportional, integral, and differential parameters according to the input error, and then generates a PWM signal with a corresponding duty cycle as a PWM control signal.

5. The closed-loop control system according to claim 4, characterized in that: The sensor group includes a differential pressure sensor and a temperature sensor, wherein: The differential pressure sensor is provided on the air guide ring of the EC fan and is used to determine the difference between the air inlet of the EC fan and the standard atmospheric pressure, so as to realize the constant static pressure mode or constant air volume mode of the system; The temperature sensor is installed in the material or environment to be cooled, and is used to realize the constant temperature mode of the system according to the difference between the feedback data of the temperature change and the set temperature.

6. The closed-loop control system according to claim 4, characterized in that: The constant static pressure mode or the constant air volume mode is applied to an air handling unit, and the constant temperature reading mode is applied to a cooling tower.

7. The closed-loop control system according to claim 1, characterized in that: The EC fan achieves stepless speed regulation by adjusting the PWM duty cycle, and the speed regulation range is 20%-100% of the rated speed of the EC fan.

8. A closed-loop control method based on EC fan, characterized in that: Based on the closed-loop control system according to any one of claims 1 to 7, the method comprises the following working steps: S1: Initialize system parameters and set target control values; S2: The sensor group collects pressure difference or temperature data in real time; S3: The controller calculates the difference between the feedback data of the sensor group and the target control value and uses the difference as input to calculate the PWM duty cycle through the PID control algorithm and generate a PWM control signal; S4: The EC fan adjusts its speed according to the PWM control signal; S5: Execute S2-S4 in a loop until the target control value is reached.

9. The method according to claim 7, characterized in that The mathematical model of the PID control algorithm is: in, is the PWM duty cycle, is the error between the target control value and the feedback data, i.e., the actual value.

Images