Intelligent control system for ventilation of coal mine based on PLC double-fan cooperative control

Abstract

The application discloses a coal mine ventilation intelligent regulation and control system based on PLC double-fan cooperative control and relates to the technical field of fan ventilation regulation and control.The system lays a foundation for data real-time sharing and seamless takeover by combining the mine equivalent ventilation impedance derived by a working analysis module and the dynamically determined standby fan coupling start parameters.A double-fan cooperative module dynamically adjusts standby fan parameters based on the frequency drop amplitude of a main fan, ensures smooth connection of the operation states of the main and standby fans, and avoids parameter faults during takeover.A feedback adjustment module accurately calculates a comprehensive balance error by using a frequency deviation and a double-path air pressure difference value, and provides real-time optimization basis for automatic regulation of air doors by combining air door pressure sensor signals.The system realizes efficient data sharing and seamless takeover control of two sets of PLCs, makes the automatic regulation of air door pressure sensors more targeted, and ultimately ensures continuous air flow during the whole main and standby fan switching process and stable underground air pressure.

Description

Technical Field

[0001] This invention relates to the field of ventilation control technology, specifically to a coal mine ventilation intelligent control system based on PLC dual-fan collaborative control. Background Technology

[0002] The uninterrupted airflow and stable air pressure control during the switching between primary and standby fans relies on the real-time data sharing and seamless takeover capabilities of the two PLC control systems. However, in actual coal mine ventilation scenarios, factors such as fan load fluctuations and dynamic changes in ventilation network resistance objectively exist. Existing technical solutions reveal the following shortcomings: First, the existing technology lacks a unified quantitative benchmark for ventilation network resistance between the two PLC control systems, and lacks accurate quantification and sharing of core common parameters such as the mine's equivalent ventilation impedance, making it impossible to form a unified judgment standard for collaborative control. Second, the existing solution does not design an adaptive parameter adjustment mechanism for the dynamic transition process of switching between primary and standby fans, making it difficult to achieve seamless connection of control authority and easily leading to airflow gaps or redundancy caused by parameter discontinuities. Finally, the existing automatic damper adjustment does not combine changes in ventilation network resistance and the operating status of primary and standby fans for linkage adaptation, and cannot accurately offset instantaneous air pressure disturbances during the switching process.

[0003] Therefore, there is an urgent need for an intelligent control system with a unified resistance quantification benchmark, dynamic parameter adaptive optimization, and fan and damper linkage adjustment functions to solve the above-mentioned technical bottlenecks, realize real-time data sharing and seamless takeover of the two PLC control systems, and ensure continuous airflow and stable downhole air pressure when switching between main and standby fans. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a coal mine ventilation intelligent control system based on PLC dual-fan collaborative control. This system solves the problems of existing technologies, such as difficulty in real-time data sharing and inconvenience in using pressure sensor signals at the damper to automatically adjust the damper opening degree, which can lead to air interruption or unstable air pressure.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: a coal mine ventilation intelligent control system based on PLC dual-fan collaborative control, comprising: a joint operation analysis module, used to analyze the main fan frequency, damper opening and main fan air pressure through the PLC controller to obtain the mine equivalent ventilation impedance, and with the goal of maintaining the benchmark air volume of the mine's total return airway, using the mine equivalent ventilation impedance as a feedforward condition, dynamically determining the coupling start frequency of the standby fan and the standby fan damper opening.

[0006] The dual-fan coordination module is used to start the standby fan at a coupled start frequency via a PLC controller, and adjusts the coupled start frequency and damper opening of the standby fan based on the determined frequency drop of the main fan.

[0007] The feedback adjustment module is used in the process of dual-fan coordination to determine the comprehensive balance error by using the frequency deviation of the main and standby fans and the pressure difference between the two channels, and to adjust the fan frequency and fan damper opening based on the comprehensive balance error so that the frequency deviation of the main and standby fans and the pressure difference between the two channels tend to be minimized.

[0008] The switching status judgment module is used to determine that the air volume power switching is complete when the main control PLC reduces the frequency of the main fan to the lower limit and the comprehensive balance error is continuously lower than the set threshold.

[0009] Compared with existing technologies, this invention has the following advantages: The mine equivalent ventilation impedance derived by the joint working analysis module and the dynamically determined standby fan coupling start-up parameters ensure that the control judgment standards of the two PLCs are completely consistent, laying the foundation for real-time data sharing and seamless takeover; the dual-fan coordination module dynamically adjusts the standby fan parameters based on the main fan frequency drop, ensuring smooth connection between the main and standby fan operation states and avoiding parameter gaps during takeover; the feedback adjustment module accurately calculates the comprehensive balance error using frequency deviation and dual-path air pressure difference, combined with the pressure sensor signal at the air door, providing real-time optimization basis for automatic air door adjustment, and offsetting deviations in the coordination process by synchronously adjusting the fan frequency and air door opening, preventing air pressure fluctuations; the dual-condition judgment of the switching status judgment module ensures accurate switching timing, avoiding the risk of air outage caused by switching too early or too late. This achieves efficient data sharing and seamless takeover control between the two PLCs, and makes the automatic adjustment of the air door pressure sensor more targeted, ultimately ensuring continuous airflow and stable underground air pressure throughout the main and standby fan switching process. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the module connection of the intelligent control system for coal mine ventilation based on PLC dual-fan coordinated control of the present invention.

[0011] Figure 2 This invention provides a flowchart for determining the coupling start frequency and standby fan damper opening in a coal mine ventilation intelligent control system based on PLC dual-fan collaborative control.

[0012] Figure 3 This is a flowchart illustrating the adjustment of fan frequency and fan damper opening based on comprehensive balance error in the intelligent control system for coal mine ventilation based on PLC dual-fan collaborative control. Detailed Implementation

[0013] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Please refer to the accompanying drawings. Figure 1This invention provides a technical solution: a coal mine ventilation intelligent control system based on PLC dual-fan collaborative control, comprising: a joint operation analysis module, used to analyze the main fan frequency, damper opening and main fan air pressure through the PLC controller to obtain the mine equivalent ventilation impedance, and dynamically determine the coupling start frequency of the standby fan and the standby fan damper opening with the mine equivalent ventilation impedance as the feedforward condition, with the goal of maintaining the benchmark air volume of the mine's total return airway as the target.

[0014] Considering that the mine ventilation network consists of roadways and facilities, its resistance distribution is complex and inherent. When switching, the main and standby fans need to share the same ventilation network. The equivalent ventilation impedance is a comprehensive quantification of the network's resistance characteristics. Without this parameter, the pressure loss requirement of the standby fan cannot be accurately calculated, and the frequency and damper opening can only be blindly matched, which can easily lead to insufficient air volume replenishment (lower than the reference air volume) or excessive output (sudden increase in air pressure). Therefore, the process of obtaining the mine's equivalent ventilation impedance is as follows: calculate the absolute value of the difference between the main fan's air pressure and the theoretical expected air pressure value, and use it as the total pressure loss value of the system.

[0015] The ratio of the total pressure loss of the system to the real-time air volume of the main fan is calculated to obtain the unit air volume resistance coefficient, which is a direct measured derivative value of the ventilation network resistance under the current operating conditions and can accurately reflect the real resistance deviation caused by changes in physical structure.

[0016] Based on the current frequency of the main fan and the opening of the damper, the corresponding theoretical unit air volume resistance coefficient range is retrieved from the preset database.

[0017] Determine whether the unit air volume resistance coefficient is within the range of the theoretical unit air volume resistance coefficient; otherwise, determine that the ventilation is in an abnormal state.

[0018] If so, the median of the theoretical unit air volume resistance coefficient range is calculated, and the median is weighted and summed with the unit air volume resistance coefficient according to a preset weight to obtain the mine equivalent ventilation impedance.

[0019] When the unit air volume resistance coefficient exceeds the theoretical unit air volume resistance coefficient range, the system immediately issues an alarm signal, stops the main fan frequency reduction operation, and the standby fan maintains the current state. After the maintenance personnel troubleshoot the fault (such as roadway blockage or sensor failure) and reset it, the collaborative switching process is restarted.

[0020] The theoretical expected wind pressure is a pre-determined calibration value based on the main fan's factory characteristic curve and on-site calibration data. It represents the upper limit of theoretical wind pressure output under the current operating frequency and damper opening conditions of the main fan, without external ventilation load (i.e., ideal idling condition) or only overcoming the standard reference resistance. This value serves as a quantitative benchmark for the fan's theoretical output capacity and is used for subsequent comparative analysis with actual operating conditions.

[0021] The theoretical ventilation resistance range is determined by querying a pre-set database based on the current actual operating frequency of the main fan and the actual damper opening. This database is constructed using factory test data of the main fan, mine ventilation network design parameters, and on-site operational statistics, and will not be elaborated upon further here. The median of the theoretical unit airflow resistance coefficient range is weighted and fused with the unit airflow resistance coefficient to ensure that the fused equivalent mine ventilation impedance neither deviates from the theoretical design principles nor fails to accurately reflect the current actual operating conditions.

[0022] As an example, based on the factory characteristic curves and field calibration data provided by the wind turbine manufacturer, a theoretical wind pressure expectation value mapping table is pre-established. At different frequencies (1Hz step) and damper openings (5%), the wind pressure values ​​during no-load operation of the wind turbine are measured and stored in the PLC database. During actual system operation, based on the current actual operating frequency of the main wind turbine and the actual damper opening, the corresponding theoretical wind pressure expectation value is read in real-time from the mapping table using linear interpolation.

[0023] As an example, assuming the main fan is currently operating at a frequency of 45Hz and the damper opening is 75%, the theoretical expected wind pressure is 2150Pa according to the theoretical expected wind pressure mapping table. Meanwhile, the pressure sensor measures the main fan's wind pressure at 1950Pa, so the total pressure loss of the system is |1950-2150|=200Pa. The air volume sensor measures the real-time air volume of the main fan at 10500m³ / min, so the unit air volume resistance coefficient is 200 / 10500≈0.01905Pa·min / m³.

[0024] The theoretical unit air volume resistance coefficient range for the current operating conditions is 0.0185-0.0195 obtained from the preset database. If the measured unit air volume resistance coefficient is within this range, the ventilation is considered normal.

[0025] The equivalent ventilation impedance of a mine is a comprehensive quantitative parameter characterizing the overall resistance characteristics of the mine's ventilation network. Its value directly corresponds to the strength of the ventilation network's resistance; a larger value indicates a stronger ability of the network to impede airflow, resulting in more energy consumption (pressure loss) for the airflow; a smaller value indicates a weaker network resistance and smoother ventilation. Essentially, it involves converting various ventilation resistances dispersed in roadways and facilities into a unified resistance benchmark value through the calculation of total system pressure loss, verification of unit airflow resistance coefficients, and weighted fusion.

[0026] The meaning of equivalent ventilation impedance in a mine includes two aspects: First, it reflects the inherent resistance level of the mine ventilation network. The magnitude of the value is directly related to the physical structure of the roadway, such as cross-section, length, and support form, and is an inherent attribute identifier of the mine ventilation network. Second, it serves as the basis for adapting the operation of the fans. It is used to determine the ventilation status, calculate the pressure loss value that the fans need to overcome, screen the optimal frequency and damper opening combination, and ensure that the fan output matches the network resistance.

[0027] Calculating the equivalent ventilation impedance of a mine can provide a unified and accurate resistance benchmark for the coordinated switching of dual fans in a PLC. This benchmark can support the optimal combination selection of the standby fan's coupling start-up frequency and damper opening, ensuring that the standby fan accurately compensates for the main fan's airflow gap to maintain the benchmark airflow. It can also determine ventilation anomalies by verifying the unit airflow resistance coefficient, predict the impedance change after the main fan's frequency reduction, and select the optimal frequency reduction range. Furthermore, it can provide a reference for the dynamic adjustment of dual fans and the correction of feedback deviations that conforms to the inherent characteristics of the mine ventilation network. Ultimately, this achieves stable air pressure and constant airflow during the switching of dual fans, while avoiding ventilation failures and ineffective equipment losses, thus ensuring the safety of mine ventilation.

[0028] To ensure the total air volume is not lower than the baseline air volume, and considering energy saving, consumption reduction, and equipment wear control to minimize system disturbance during switching, the process for determining the coupling start frequency and damper opening of the standby fan is as follows: If the main fan air volume is less than the baseline air volume, the standby fan air volume is the difference between the baseline air volume and the main fan air volume. If the main fan air volume is equal to the baseline air volume, the standby fan air volume is the difference between the set maximum safe air volume and the main fan air volume. The set maximum safe air volume is the upper limit of the instantaneous maximum total air volume allowed during switching, typically set to 110%-120% of the baseline air volume.

[0029] The pressure loss value of the standby fan is obtained by multiplying the standby fan's air volume by the mine's equivalent ventilation impedance.

[0030] The combination of frequency and damper opening of the selected standby fan is matched to ensure that the difference between the theoretical expected wind pressure of the corresponding combination and the pressure loss of the standby fan is equal to the current wind pressure of the standby fan.

[0031] The optimal combination of standby fan frequencies selected will be used as the coupling start-up frequencies of the standby fans.

[0032] The optimal combination of damper openings selected will be used as the backup damper openings.

[0033] By setting the backup fan's make-up air volume differently, the requirement that the total air volume should not be lower than the baseline air volume is met, while energy waste caused by redundant air volume is avoided by making up air on demand, thus balancing ventilation safety and energy saving needs. By matching the difference between the theoretical expected air pressure and the backup fan's pressure loss value with the current air pressure of the backup fan, the matching logic can be used to select the backup fan frequency and backup fan damper opening combination that matches the ventilation network resistance and the fan's own operating characteristics, ensuring the rationality of parameter matching. This controls the fan's operating energy consumption from the start-up source, reduces equipment mechanical wear, and avoids disturbances to the system caused by large parameter adjustments, so that the startup parameters of the backup fan match the actual operating requirements.

[0034] If none of the alternative combinations can satisfy the condition that the difference between the theoretical expected wind pressure and the standby fan pressure loss value equals the current wind pressure of the standby fan, then the combination with the smallest difference between the theoretical expected wind pressure and the sum of the current wind pressure and the standby fan pressure loss value is selected as the optimal combination, and the absolute value of this difference must not exceed 10% of the theoretical expected wind pressure; if it does, then the standby fan air volume and pressure loss value are recalculated at 1.1 times the maximum set safe air volume, and the combination is screened again.

[0035] Considering the need for energy conservation, consumption reduction, equipment loss control, and system disturbance reduction during collaborative control, the process of matching and judging the combination of standby fan frequency and damper opening is as follows: sort the standby fan frequencies of each combination from low to high, and select the combination with the lowest standby fan frequency value.

[0036] If there are multiple combinations of standby fans with the same frequency value, sort the damper opening adjustment range of the combinations from smallest to largest, and select the combination with the smallest damper opening adjustment range as the optimal combination.

[0037] First, selecting the combination with the lowest frequency minimizes energy consumption during the startup and operation of the standby fan, reducing the operating load and mechanical wear of the fan motor, and effectively achieving energy saving, consumption reduction, and equipment protection. At the same frequency, selecting the combination with the smallest damper opening adjustment range avoids sudden increases and decreases in underground air pressure caused by large damper openings and closings, reducing instantaneous disturbances to the ventilation system, ensuring system stability, and minimizing wear on the damper actuator, extending the service life of damper-related equipment. Furthermore, the overall selection rules are simple, clear, quantifiable, and can be embedded in a PLC control system for automatic and rapid selection, improving the efficiency and accuracy of standby fan parameter matching.

[0038] The dual-fan coordination module is used to start the standby fan at a coupled start frequency via a PLC controller, and adjusts the coupled start frequency and damper opening of the standby fan based on the determined frequency drop of the main fan.

[0039] Because excessively large frequency reductions in the main fan can lead to sudden changes in air volume, causing short-term fluctuations in the mine's equivalent ventilation impedance that exceed safe limits, this can result in deviations in the calculation of pressure loss for the standby fan, sudden increases or decreases in air pressure, or even air outages. Conversely, excessively small reductions can prolong the coordination time between the main and standby fans, increase energy redundancy, and easily accumulate airflow disturbances. Therefore, the process for determining the frequency reduction range of the main fan is as follows: multiple different single frequency reduction ranges are preset using the PLC controller, and the historical changes in the mine's equivalent ventilation impedance after the main fan executes a single frequency reduction range are analyzed and predicted for each single frequency reduction range.

[0040] Among the historical frequency decreases that have never exceeded the threshold of the equivalent ventilation impedance change in the mine, the frequency decrease that can be stabilized the fastest within a preset stable time is selected as the frequency decrease of the main fan.

[0041] On the one hand, although the equivalent ventilation impedance of a mine is an inherent property determined by the mine structure, the air volume adjustment caused by the change in the frequency of the main fan will lead to predictable short-term fluctuations. Moreover, the fluctuation pattern can be accumulated through long-term operation data to form historical samples, which provides a basis for analysis and prediction. On the other hand, the frequency reduction of the main fan is positively correlated with the impedance fluctuation amplitude and the stabilization time (the larger the frequency reduction amplitude, the more violent the fluctuation and the longer the stabilization time). This objective correlation provides logical support for screening the frequency reduction amplitude through impedance change.

[0042] By selecting amplitudes that do not exceed the impedance change threshold, the system disturbances caused by frequency reduction can be limited to a safe range, avoiding excessive impedance fluctuations that could lead to imbalance in the shared data reference between the two PLCs and inaccurate adjustment of the damper pressure sensor, thus ensuring stable downhole air pressure and continuous airflow. Prioritizing the amplitude that stabilizes fastest can shorten the duration of impedance fluctuations, reduce the lag in adjusting the standby fan parameters, improve switching efficiency, and reduce energy redundancy.

[0043] It should be noted that stabilization refers to the state in which the measured calculated value of the mine's equivalent ventilation impedance quickly converges to the inherent reference value determined by the mine's physical structure after the main fan operates at a single frequency decrease.

[0044] The threshold for the change of equivalent ventilation impedance in a mine is based on the inherent benchmark value of the mine ventilation network theory, and is calibrated by combining the maximum fluctuation value within the 95% confidence interval during long-term operation, specifically ±10% of the theoretical benchmark value.

[0045] Furthermore, such as Figure 2 As shown, the process of adjusting the coupling start frequency and damper opening of the standby fan is as follows: after the main fan frequency is reduced each time according to the decrease in the main fan frequency, the difference between the reference air volume and the remaining ventilation volume of the main fan is taken as the required ventilation volume of the standby fan.

[0046] After the equivalent ventilation impedance of the mine stabilizes, the pressure loss value after the backup fan is obtained by multiplying it by the required ventilation volume of the backup fan.

[0047] Based on the pressure loss value after the backup fan is updated, the updated frequency and damper opening of the backup fan are selected to be suitable, and the coupling start frequency and the damper opening of the backup fan are replaced.

[0048] Each time the main fan reduces its frequency by a predetermined amount, the remaining ventilation volume of the main fan will change accordingly. The required ventilation volume of the standby fan is updated by the difference between the baseline air volume and the remaining air volume. This can accurately make up for the air volume gap after the main fan reduces its frequency, and ensure that the total air volume is not lower than the baseline requirement. The pressure loss value is calculated and updated after the equivalent ventilation impedance of the mine stabilizes. This can avoid the pressure loss calculation deviation caused by impedance fluctuations and ensure the accuracy of parameter adaptation.

[0049] By selecting and matching the frequency and damper opening of the backup fan based on the new pressure loss value and replacing the original parameters, the output of the backup fan can always match the current ventilation network resistance and make-up air demand. This avoids pressure fluctuations or energy waste caused by the disconnect between the original starting parameters and dynamic operating conditions. At the same time, it provides support for the real-time sharing of accurate data between the two PLC control systems, ensuring a smooth connection in the coordination process between the main and backup fans. Ultimately, it achieves continuous airflow and stable underground air pressure during switching, taking into account both energy saving and consumption reduction and equipment wear control.

[0050] The feedback adjustment module is used in the process of dual-fan coordination to determine the comprehensive balance error by using the frequency deviation of the main and standby fans and the pressure difference between the two channels, and to adjust the fan frequency and fan damper opening based on the comprehensive balance error so that the frequency deviation of the main and standby fans and the pressure difference between the two channels tend to be minimized.

[0051] Considering that during the dual-fan coordination process, the frequency reduction of the main fan and the parameter update of the standby fan will lead to dynamic changes in frequency and wind pressure, the deviation of a single parameter cannot fully reflect the system imbalance state and is prone to one-sided adjustment. Therefore, the frequency deviation of the main and standby fans and the difference in wind pressure between the two paths are used to determine the comprehensive balance error. The specific process is as follows: calculate the difference between the actual frequency of the main fan and the target frequency reduction frequency, and the difference between the frequency of the standby fan after the update and the target coupling frequency to obtain the frequency deviation of the main and standby fans.

[0052] Calculate the difference between the actual wind pressure of the main fan and the target wind pressure of the main fan, and the difference between the actual wind pressure of the standby fan and the target wind pressure of the standby fan to obtain the pressure difference between the two circuits.

[0053] The frequency deviation and the difference in wind pressure between the two paths are combined to obtain the deviation vector. The elements in the deviation vector are normalized and their absolute values ​​are taken. The four absolute values ​​are then weighted and summed to obtain the balance error.

[0054] The frequency of the blower directly determines the output air volume, and the air pressure is a direct indicator of the stability of underground ventilation. The two together constitute the key factors affecting the coordinated stability of the dual blowers. Moreover, the quantitative data of frequency deviation and the difference in air pressure between the two channels can be collected in real time by the PLC. At the same time, normalization can eliminate the difference in dimensions between frequency and air pressure, and weighted summation can assign reasonable weights to the two types of deviations according to the priority of ventilation safety. This meets the execution requirements of the PLC control system for quantitative indicators and also meets the requirements of constant air volume and stable air pressure in coal mine ventilation.

[0055] Considering that adjusting a single parameter or making irregular adjustments can easily lead to system oscillations and sudden changes in wind pressure, it is necessary to clearly define the adjustment direction of the frequency and damper. Therefore, as follows... Figure 3 As shown, the process of adjusting the fan frequency and fan damper opening based on the comprehensive balance error to minimize the frequency deviation of the main and standby fans and the pressure difference between the two circuits is as follows: if the deviation corresponding to the frequency is positive, the fan frequency is adjusted to decrease. If it is negative, the fan frequency is adjusted to increase.

[0056] If the corresponding deviation of the fan air pressure is positive, the damper opening should be adjusted to increase. If it is negative, the damper opening should be adjusted to decrease.

[0057] Based on the frequency adjustment step size, the actual frequency of the main fan and the updated frequency of the standby fan are synchronously adjusted according to the corresponding adjustment direction. After each synchronous adjustment, the sum of the absolute values ​​of the frequency deviations of the main and standby fans is calculated.

[0058] After each adjustment of the actual frequency of the main fan and the frequency of the standby fan following an update, the opening of the dampers for both the main fan and the standby fan is adjusted synchronously based on the adjustment step size until the maximum allowable adjustment is reached. The maximum allowable adjustment range for the fan frequency is 30%-80% of the rated fan frequency, and the maximum allowable adjustment range for the damper opening is 0%-100% of the damper's mechanical travel. Both must not exceed the rated parameters of the equipment and must meet the following requirements: the underground air pressure must not exceed the roadway's design compressive strength, and the air volume must not be lower than the approved minimum value.

[0059] After each synchronous adjustment of the main fan damper opening and the standby fan damper opening, the sum of the absolute values ​​of the pressure difference between the two circuits is calculated.

[0060] The adjusted actual frequency of the main fan, the updated frequency of the standby fan, the damper opening of the main fan, and the damper opening of the standby fan are determined to minimize the sum of the absolute values ​​of the frequency deviations and the sum of the absolute values ​​of the dual-path wind pressure differences, and are taken as the final adjusted state.

[0061] If the sum of the absolute values ​​of the pressure difference between the two airways is still not minimized after the damper is adjusted to the maximum allowable adjustment, then the current damper opening is maintained, and the fan frequency is adjusted only until the sum of the absolute values ​​of the frequency deviation and the sum of the absolute values ​​of the pressure difference is minimized, or the frequency reaches the maximum allowable adjustment.

[0062] The frequency of the fan directly determines the output air volume. The positive or negative value of the frequency deviation corresponds to the direction of the air volume supply and demand imbalance (positive deviation means that the actual frequency is higher than the target, resulting in redundant air volume; negative deviation means that the air volume is insufficient). Therefore, adjusting the frequency according to positive decrease and negative increase conforms to the physical logic of air volume matching. The damper opening affects the air pressure by changing the ventilation cross-sectional area. The positive or negative value of the air pressure deviation reflects the air pressure supply and demand status (positive deviation requires increasing the ventilation area to relieve pressure, and negative deviation requires decreasing the area to increase pressure). The adjustment direction of positive increase and negative decrease conforms to the engineering law of air pressure regulation.

[0063] Adjusting in a clearly defined direction can quickly offset deviations and prevent the accumulation of system imbalances; fixed-step synchronous adjustment can reduce instantaneous disturbances during the adjustment process, ensuring stable downhole air pressure and continuous airflow, and eliminating the risk of air outages; step-by-step calculation of deviations and locking in the optimal state can ensure that the combination of main and backup fan frequencies and damper openings is most suitable for the current operating conditions, avoiding both redundant and insufficient airflow, and reducing ineffective losses in fan motors and damper actuators, thus achieving energy saving and consumption reduction; at the same time, the standardized adjustment process can be directly embedded into PLC automated execution, improving adjustment efficiency and accuracy, providing stable parameter support for seamless takeover control of two sets of PLCs, and ensuring a smooth transition during the switching process.

[0064] It should be noted that the frequency adjustment step size and the opening adjustment step size can be determined based on long-term operating data, selecting the frequency adjustment step size and the opening adjustment step size that results in the fastest deviation convergence speed and the smallest system disturbance. For example, the frequency adjustment step size is calibrated to 0.5-1 Hz / time, and the opening adjustment step size is calibrated to 5%-10% / time.

[0065] The switching status judgment module is used to determine that the air volume power switching is complete when the main control PLC reduces the frequency of the main fan to the lower limit and the comprehensive balance error continues for a set time (e.g., 3 seconds) below the set threshold.

[0066] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0067] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0068] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0069] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0070] Finally, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A coal mine ventilation intelligent control system based on PLC dual-fan coordinated control, characterized in that, include: The joint working analysis module is used to analyze the main fan frequency, damper opening and main fan pressure through the PLC controller to obtain the mine equivalent ventilation impedance. With the goal of maintaining the benchmark air volume of the mine's total return airway, the mine equivalent ventilation impedance is used as a feedforward condition to dynamically determine the coupling start frequency of the standby fan and the standby fan damper opening. The dual-fan coordination module is used to start the standby fan at a coupling start frequency via a PLC controller, and to adjust the coupling start frequency and standby fan damper opening based on the determined main fan frequency drop. The feedback adjustment module is used in the process of dual-fan coordination to determine the comprehensive balance error by using the frequency deviation of the main and standby fans and the pressure difference between the two channels, and to adjust the fan frequency and fan damper opening based on the comprehensive balance error so that the frequency deviation of the main and standby fans and the pressure difference between the two channels tend to be minimized. The switching status judgment module is used to determine that the air volume power switching is complete when the main control PLC reduces the frequency of the main fan to the lower limit and the comprehensive balance error is continuously lower than the set threshold. The process of determining the overall balance error using the frequency deviation of the main and standby fans and the pressure difference between the two channels is as follows: Calculate the difference between the actual frequency of the main fan and the target frequency reduction, and the difference between the frequency of the standby fan after the update and the target coupling frequency to obtain the frequency deviation between the main and standby fans. Calculate the difference between the actual wind pressure of the main fan and the target wind pressure of the main fan, and the difference between the actual wind pressure of the standby fan and the target wind pressure of the standby fan to obtain the pressure difference between the two circuits. The frequency deviation and the difference in wind pressure between the two paths are combined to obtain a deviation vector. The elements in the deviation vector are normalized and their absolute values ​​are taken. The four absolute values ​​are then weighted and summed to obtain the comprehensive balance error. The process of adjusting the fan frequency and fan damper opening based on the comprehensive balance error to minimize the frequency deviation of the main and standby fans and the pressure difference between the two circuits is as follows: The adjustment direction of the fan frequency and fan damper opening is determined by the deviation vector obtained from the frequency deviation of the main and standby fans and the pressure difference between the two channels; Based on the frequency adjustment step size, the actual frequency of the main fan and the updated frequency of the standby fan are synchronously adjusted in the corresponding adjustment direction. After each synchronous adjustment, the sum of the absolute values ​​of the frequency deviations of the main and standby fans is calculated. After each adjustment of the actual frequency of the main fan and the frequency of the standby fan after each update, the opening of the damper of the main fan and the damper of the standby fan are adjusted synchronously based on the opening adjustment step size until the maximum allowable adjustment amount is reached. After each synchronous adjustment of the main fan damper opening and the standby fan damper opening, calculate the sum of the absolute values ​​of the pressure difference between the two circuits. The adjusted actual frequency of the main fan, the updated frequency of the standby fan, the damper opening of the main fan, and the damper opening of the standby fan are determined to minimize the sum of the absolute values ​​of the frequency deviations and the sum of the absolute values ​​of the dual-path wind pressure differences, and are taken as the final adjusted state.

2. The intelligent control system for coal mine ventilation based on PLC dual-fan coordinated control according to claim 1, characterized in that, The process of analyzing the main fan frequency and main fan pressure using a PLC controller to obtain the equivalent ventilation impedance of the mine is as follows: Acquire real-time main fan frequency, real-time damper opening, and real-time main fan air pressure; Based on the factory characteristic curve of the main fan and the field calibration data, determine the theoretical wind pressure expectation value corresponding to the current main fan frequency and damper opening. The theoretical wind pressure expectation value is the calibration value. Calculate the absolute value of the difference between the main fan pressure and the theoretical expected pressure, and use it as the total pressure loss of the system; The ratio of the total pressure loss of the system to the real-time air volume of the main fan is calculated to obtain the resistance coefficient per unit air volume; Based on the current frequency of the main fan and the opening of the damper, the corresponding theoretical unit air volume resistance coefficient range is retrieved from the preset database; Determine whether the unit air volume resistance coefficient is within the range of the theoretical unit air volume resistance coefficient; otherwise, determine that the ventilation is in an abnormal state. If so, the median of the theoretical unit air volume resistance coefficient range is calculated, and the median is weighted and summed with the unit air volume resistance coefficient according to a preset weight to obtain the mine equivalent ventilation impedance.

3. The intelligent control system for coal mine ventilation based on PLC dual-fan coordinated control according to claim 1, characterized in that, With the goal of maintaining the baseline air volume in the mine's total return airway, and using the mine's equivalent ventilation impedance as a feedforward condition, the process of determining the coupling start-up frequency of the standby fan and the standby fan damper opening is as follows: Determine the standby fan air volume, and multiply the standby fan air volume by the mine's equivalent ventilation impedance to obtain the standby fan pressure loss value; The combination of frequency and damper opening of the selected standby fan is matched to ensure that the difference between the theoretical expected wind pressure of the corresponding combination and the pressure loss of the standby fan is equal to the current wind pressure of the standby fan. The optimal combination of standby fan frequencies selected will be used as the coupling start-up frequencies of the standby fans. The optimal combination of damper openings selected will be used as the backup damper openings.

4. The intelligent control system for coal mine ventilation based on PLC dual-fan coordinated control according to claim 3, characterized in that, The process of matching and determining the combination of frequency and damper opening of the selected standby fan is as follows: Sort the standby fan frequencies of each combination from low to high, and select the combination with the lowest standby fan frequency value. If there are multiple combinations of standby fans with the same frequency value, sort the damper opening adjustment range of the combinations from smallest to largest, and select the combination with the smallest damper opening adjustment range as the optimal combination.

5. The intelligent control system for coal mine ventilation based on PLC dual-fan coordinated control according to claim 3, characterized in that, The process of determining the standby fan air volume is as follows: If the main fan's air volume is less than the reference air volume, the standby fan's air volume is the difference between the reference air volume and the main fan's air volume; if the main fan's air volume is equal to the reference air volume, the standby fan's air volume is the difference between the set maximum safe air volume and the main fan's air volume.

6. The intelligent control system for coal mine ventilation based on PLC dual-fan coordinated control according to claim 1, characterized in that, The process for determining the frequency drop of the main fan is as follows: By presetting multiple different single frequency drop amplitudes using the PLC controller, the historical changes in the mine's equivalent ventilation impedance after the main fan executes a single frequency drop amplitude are analyzed and predicted for each single frequency drop amplitude. Among the historical frequency decreases that have never exceeded the threshold of the equivalent ventilation impedance change in the mine, the frequency decrease that can be stabilized the fastest within a preset stable time is selected as the frequency decrease of the main fan.

7. The intelligent control system for coal mine ventilation based on PLC dual-fan coordinated control according to claim 1, characterized in that, The process of adjusting the coupling start-up frequency of the standby fan and the damper opening of the standby fan based on the determined main fan frequency drop is as follows: After the main fan frequency is reduced each time according to the decrease in the main fan frequency, the difference between the base air volume and the remaining ventilation volume of the main fan is used as the required ventilation volume of the standby fan. After the equivalent ventilation impedance of the mine stabilizes, the pressure loss value after the standby fan is obtained by multiplying it by the required ventilation volume of the standby fan. Based on the pressure loss value after the backup fan is updated, the updated frequency and damper opening of the backup fan are selected to be suitable, and the coupling start frequency and the damper opening of the backup fan are replaced.

8. The intelligent control system for coal mine ventilation based on PLC dual-fan coordinated control according to claim 1, characterized in that, The process of determining the adjustment direction of the fan frequency and fan damper opening based on the deviation vector obtained from the frequency deviation of the main and standby fans and the pressure difference between the two channels is as follows: If the deviation corresponding to the frequency is positive, the fan frequency is adjusted to decrease; if it is negative, the fan frequency is adjusted to increase. If the corresponding deviation of the fan air pressure is positive, the damper opening is adjusted to increase; if it is negative, the damper opening is adjusted to decrease.

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