An Adaptive Variable Frequency Airflow Control Method for Fans

Abstract

This invention proposes an adaptive variable frequency air volume control method for fans, belonging to the field of air volume control for variable air volume air conditioning systems. The method predicts the required air volume based on the actual operating conditions of each area and detects the actual air volume to calculate the total required air volume. Combined with the fan characteristic curve, the initial frequency of the fan is obtained. Then, by using the difference between the total required air volume and the total measured air volume and the opening of the terminal damper, the initial frequency of the fan is corrected according to the fan frequency correction rule, thereby achieving adaptive control of the fan frequency. This achieves energy-saving effects while taking into account the air volume demand of the most unfavorable terminal.

Description

Technical Field

[0001] This invention relates to the field of air volume control in variable air volume (VAV) air conditioning systems, and provides an adaptive fan frequency conversion air volume control method. Background Technology

[0002] In large public buildings, variable air volume (VAV) air conditioning systems automatically adjust airflow according to changes in load demand by controlling parameters such as the fan frequency of the air handling unit and adjusting the opening of dampers. Currently, VAV air conditioning systems generally employ variable frequency control strategies for their fans, including constant static pressure, variable static pressure, and total airflow. Constant and variable static pressure methods regulate fan frequency through duct static pressure, while total airflow determines the fan frequency based on the relationship between airflow and fan speed. All these methods have certain effects, but they also have corresponding drawbacks. The constant static pressure method maintains a high static pressure setpoint even under partial load operation, resulting in wasted fan energy. The variable static pressure method has complex and unstable system control, and is prone to insufficient ventilation. The total airflow method tends to sacrifice airflow demand at less desirable terminals, leading to localized overcooling or overheating, and cannot accurately meet the needs of all areas. Summary of the Invention

[0003] To address the problems existing in the air volume control methods of variable air volume (VAV) air conditioning systems in the background art, this invention proposes an adaptive fan frequency conversion air volume control method, which further optimizes the defects of VAV air conditioning systems and achieves the goals of energy saving, comfort, and stability.

[0004] The present invention proposes an adaptive variable frequency air volume control method for fans, which involves predicting the required air volume for each area based on actual operating conditions, detecting the actual air volume and the opening of each terminal damper, summing the required air volume and the measured air volume for each area to obtain the total required air volume and the total measured air volume, and obtaining the initial frequency of the fan from the total required air volume and the fan characteristic curve; then correcting the initial frequency of the fan by the difference between the total required air volume and the total measured air volume to obtain the fan frequency correction value; finally, optimizing the fan frequency correction value based on the opening of the terminal dampers to obtain the final fan frequency control value.

[0005] The method for correcting the fan frequency based on the difference between the required air volume and the measured air volume is as follows: obtain the difference between the required air volume and the measured air volume online in real time, compare the difference with a set threshold (2% of the device's maximum air volume), and if the result is not within the set threshold, increase or decrease the fan frequency; otherwise, the fan frequency correction value is zero, and finally obtain the fan frequency correction value.

[0006] The method for optimizing fan frequency by damper opening is as follows: The damper opening of each VAV terminal is acquired online in real time. A terminal damper opening of less than 80% is judged as low opening, a terminal damper opening between 80% and 95% is judged as moderate opening, and a terminal damper opening greater than 95% is judged as high opening. It is then determined whether there is a damper with high opening. If so, high opening optimization is performed; if not, it is determined whether there is a damper with appropriate opening. If so, no optimization is performed; if not, low opening optimization is performed.

[0007] High opening and low opening optimization rules: The fan frequency control value is determined based on the total number of terminal devices in operation and the number of dampers with high and low opening, that is: Fan frequency control value = Fan frequency correction value × (1 ± total number of terminal devices in operation × number of dampers with high and low opening %).

[0008] The beneficial effects of this invention are: it combines the significant energy-saving effect of the variable static pressure method with the advantage of the total air volume method in ensuring air volume. The initial frequency of the fan is determined by the total required air volume, and then the initial frequency of the fan is adjusted and optimized by the difference between the required air volume and the measured air volume and the opening of the terminal damper. This avoids the problems of the total air volume method being unable to meet the terminal demand and the variable static pressure method being insufficient in ventilation. It can achieve maximum energy-saving operation while meeting the ventilation needs of each area. Attached Figure Description

[0009] Figure 1 This is a flowchart of an adaptive variable frequency air volume control method for a fan according to the present invention. Detailed Implementation

[0010] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0011] This invention provides an adaptive variable frequency airflow control method for fans. It predicts the required airflow for different zones and determines the fan frequency control value through triple control logic to achieve energy saving and comfort. The specific method is as follows: Figure 1 As shown below:

[0012] The system predicts the required air volume for each area based on the actual operating conditions, and detects the actual air volume and the opening of each terminal damper. The total required air volume and the total measured air volume are obtained by summing the required air volume of each area and the measured air volume. The initial frequency of the fan is obtained from the total required air volume and the fan characteristic curve.

[0013] like Figure 1 As shown, the difference between the total required air volume and the total measured air volume is calculated. This difference is then compared to a set threshold, which is set to 2% of the maximum air volume of all devices. If the absolute value of the difference is within the threshold range, the damper opening is corrected; if the absolute value of the difference is not within the threshold range, the fan frequency is corrected. The formula for the fan frequency correction is as follows:

[0014] Fan frequency correction value = (demanded air volume - measured air volume) / maximum fan air volume × maximum fan speed

[0015] like Figure 1 As shown, the opening degree of the damper at the end of each VAV is judged in real time. The opening degree of the damper at the end is judged as low opening, the opening degree of the damper at the end is judged as moderate opening between 80% and 95%, and the opening degree of the damper at the end is judged as high opening. It is determined whether there is a damper with high opening. If there is, high opening optimization is performed; if not, it is determined whether there is a damper with appropriate opening. If there is, no optimization is performed; if not, low opening optimization is performed.

[0016] High and low opening optimization rules: The fan frequency control value is determined based on the total number of terminal devices in operation and the number of dampers with high and low opening. The formula is as follows: Fan frequency control value = Fan frequency correction value × (1 ± total number of terminal devices in operation × number of dampers with high and low opening).

[0017] The above-described embodiments are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. Therefore, the present invention is not limited to the embodiments described herein, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from its scope should be within the protection scope of the present invention.

Claims

1. An adaptive variable frequency air volume control method for fans, characterized in that, Each region predicts the required air volume based on actual operating conditions, and detects the actual air volume and the opening of each terminal damper. The required air volume of each region is summed with the measured air volume to obtain the total required air volume and the total measured air volume. The initial frequency of the fan is obtained from the total required air volume and the fan characteristic curve to achieve feedforward control. Then, the fan frequency correction value is obtained by correcting the initial frequency of the fan through the difference between the total required air volume and the total measured air volume to achieve feedback control. Finally, the fan frequency correction value is optimized based on the opening of the terminal dampers to obtain the fan frequency control value, and ultimately achieves adaptive control of the fan frequency.

2. The adaptive fan variable frequency air volume control method according to claim 1, characterized in that, The method for correcting the initial frequency of the fan by the difference between the required air volume and the measured air volume is as follows: the difference between the required air volume and the measured air volume is obtained online in real time, and the difference is compared with a set threshold. The threshold is set to 2% of the maximum air volume of the terminal device. If the result is not within the set threshold, the fan frequency is increased or decreased; otherwise, the fan frequency correction value is zero, and the fan frequency correction value is obtained.

3. The adaptive fan variable frequency air volume control method according to claim 1, characterized in that, The method for optimizing the fan frequency correction value by adjusting the damper opening is as follows: the damper opening of each VAV terminal is acquired online in real time. A damper opening of less than 80% is judged as low opening, a damper opening between 80% and 95% is judged as moderate opening, and a damper opening greater than 95% is judged as high opening. It is then determined whether there is a damper with a high opening. If so, high opening optimization is performed; if not, it is determined whether there is a damper with a suitable opening. If so, no optimization is performed; if not, low opening optimization is performed.

4. The adaptive fan variable frequency air volume control method according to claim 3, characterized in that, The high opening optimization is as follows: the fan frequency control value is determined based on the total number of terminal devices in operation and the number of dampers with high opening, that is: fan frequency control value = fan frequency correction value × (1 + total number of terminal devices in operation × number of dampers with high opening %).

5. The adaptive fan variable frequency air volume control method according to claim 3, characterized in that, The low opening optimization is as follows: the fan frequency control value is determined based on the total number of terminal devices in operation and the number of dampers with low opening, that is: fan frequency control value = fan frequency correction value × (1 - total number of terminal devices in operation × number of dampers with low opening %).

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