High-efficiency energy-saving variable-frequency permanent magnet fan for a mineral powder feeding system and a control method thereof

Abstract

This invention provides a high-efficiency, energy-saving variable frequency permanent magnet blower and its control method for a mineral powder feeding system. The system includes a centrifugal suspension blower with a built-in variable frequency driver, a direct-connection conveying pipeline, and a main controller with a built-in control system. The control system includes a start-up module, a closed-loop module, an anomaly module, and a shutdown module. The start-up module performs segmented start-up based on real-time pressure feedback and locks the fluidization speed. The closed-loop module adjusts the blower's operating frequency based on the deviation between the set pressure and the real-time pressure. The anomaly module calculates a discrimination factor based on real-time pressure and stator current to distinguish between pipe blockage and surge states and generates different commands. The shutdown module controls the blower to perform a line-sweeping action and utilizes the pressure attenuation generated by rotor inertial sliding in conjunction with a check valve to achieve backflow prevention shutdown. This invention has the following advantages: it solves the problems of high energy consumption and difficult fault handling in valveless operation conditions of traditional solutions, achieving adaptive adjustment and efficient operation.

Description

Technical Field

[0001] This invention relates to the fields of pneumatic conveying equipment and automatic control technology, and in particular to a high-efficiency and energy-saving variable frequency permanent magnet fan and its control method for a mineral powder feeding system. Background Technology

[0002] In the pneumatic conveying process of mineral powder feeding systems, the blower, as the power source, directly determines the conveying efficiency and system energy consumption. Traditional mineral powder conveying systems typically use positive displacement Roots blowers as the main power equipment. Since the exhaust volume of the Roots blower is relatively fixed, in order to adapt to load changes during conveying or maintain stable pipeline pressure, the system must be equipped with vent valves or relief valves for bypass pressure relief regulation. While this regulation method can maintain system operation, it causes the motor to operate under a constant high load for extended periods, with some compressed air being directly discharged into the atmosphere, resulting in energy loss. Furthermore, the complex valve and pipeline structure not only increases system maintenance costs, but also, in the event of a sudden shutdown, if the vent valve operates slowly or the check valve fails, high-pressure air backflow can cause mechanical damage to the blower itself.

[0003] In terms of control strategies, existing technologies mostly employ direct start-up or simple soft start-up methods, lacking consideration for the physical characteristics of the breathable fabric inside the air chamber. At startup, the rapid build-up of airflow pressure can easily impact the relaxed breathable fabric, leading to damage or shortened lifespan. Furthermore, during normal conveying, the back pressure required to maintain fluidization dynamically changes with the material level in the hopper. Traditional control methods typically set fixed operating parameters, failing to automatically adjust output according to real-time load demands. This results in excessive purging at low material levels, wasting energy, or insufficient fluidization causing blockages at high material levels. In addition, existing technologies primarily rely on a single pressure threshold for monitoring abnormal operating conditions during conveying. When the pipeline pressure exceeds the set value, the system typically directly identifies a fault and triggers an alarm to shut down. However, in actual operation, both physical pipeline blockages and aerodynamic fan surge can cause abnormal pressure increases, but the physical mechanisms and countermeasures for these two faults are completely different. Simply relying on pressure amplitude cannot accurately distinguish between these two operating conditions. If surge is misjudged as blockage and an attempt is made to increase output to clear it, the fan vibration will be aggravated and the equipment will be damaged. If blockage is misjudged as surge and an emergency shutdown is made, it will cause material to accumulate and clump in the pipes, increasing the difficulty of subsequent handling. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a high-efficiency and energy-saving variable frequency permanent magnet fan and its control method for a mineral powder feeding system. This invention addresses the problems of high energy consumption and complex structure caused by valve pressure relief regulation, lack of adaptive matching to load characteristics during startup and operation leading to easy equipment damage, and single fault monitoring method that cannot accurately distinguish between pipe blockage and surge, resulting in inappropriate handling strategies.

[0005] To achieve the above and other related objectives, the present invention provides the following technical solution:

[0006] A high-efficiency and energy-saving variable frequency permanent magnet fan for a mineral powder feeding system includes a chassis, a centrifugal suspension fan is provided inside the chassis, a variable frequency driver is provided inside the centrifugal suspension fan for drawing in ambient air and outputting variable frequency adjustable high-speed airflow, and a motor monitor is provided inside the variable frequency driver for collecting the operating electrical indicators of the motor and outputting operating frequency, stator current and torque data.

[0007] The first air outlet of the centrifugal suspension fan is connected to the air inlet box at the bottom of the silo of the mineral powder feeding system via a direct-connection conveying pipe. The direct-connection conveying pipe is equipped with a check valve located between the centrifugal suspension fan and the feeding silo to physically block airflow and reverse flow of mineral powder. The direct-connection conveying pipe is also equipped with a pressure sensor for collecting static pressure signals in the pipe and outputting real-time pressure. The frequency converter, motor monitor and pressure sensor are all connected to the main controller.

[0008] In one embodiment of the present invention, the main controller is provided with a control system for receiving sensor data and sending control signals such as frequency control commands to the variable frequency drive, and the control system includes a start-up module, a closed-loop module, an abnormal module and a shutdown module; wherein, the start-up module is used to control the variable frequency drive to execute segmented start-up logic and output fluidized speed according to the real-time pressure fed back by the pressure sensor;

[0009] The closed-loop module receives the real-time pressure and fluidization speed, and adjusts the operating frequency of the centrifugal levitation fan by calculating the deviation between the set pressure and the real-time pressure. The anomaly module distinguishes between pipe blockage and surge states using statistical analysis based on the real-time pressure and the stator current fed back by the motor monitor, and generates disturbance commands or anti-surge commands respectively. The shutdown module controls the centrifugal levitation fan to perform a sweeping action to empty the direct-connection conveying pipeline, and controls the frequency converter to cut off the power supply to achieve backflow prevention shutdown by utilizing the natural pressure decay generated by rotor inertia.

[0010] In one embodiment of the present invention, the starting module includes a pre-tensioning unit and an inflection point capture unit; wherein, the pre-tensioning unit is used to generate a pre-pressure command after receiving a starting command, drive the centrifugal levitation fan to output a constant low speed according to the pre-pressure command, establish a pre-pressure in the direct-connection conveying pipeline, maintain a set pre-tensioning time, and then output a pre-tensioning signal; the inflection point capture unit is used to generate a climbing command in response to the pre-tensioning signal, control the centrifugal levitation fan to accelerate, receive the real-time pressure feedback from the pressure sensor, and simultaneously calculate the time derivative of the real-time pressure in real time. When it is determined that a sudden drop inflection point occurs in the pressure curve, the current rotational speed is locked as the fluidization speed.

[0011] In one embodiment of the present invention, the closed-loop module includes a deviation calculation unit, a PID calculation unit, and an instruction output unit: wherein the deviation calculation unit is used to read the set pressure and the real-time pressure, and calculate the pressure deviation between the two; the PID calculation unit is used to calculate the frequency increase instruction based on the pressure deviation and using the speed regulation formula; the instruction output unit is used to superimpose the frequency increase instruction on the current operating frequency of the variable frequency drive, generate a frequency control instruction, and send it to the variable frequency drive.

[0012] In one embodiment of the present invention, the PID calculation unit calculates a frequency increase command based on the pressure deviation and using a speed regulation formula, including: performing a proportional operation on the pressure deviation at the current moment using a proportional coefficient, performing an integral operation on the historical accumulated value of the pressure deviation using an integral coefficient, and performing a differential operation on the rate of change of the pressure deviation using a differential coefficient; summing the results of the proportional operation, integral operation, and differential operation to generate the frequency increase command and sending it to the frequency converter driver.

[0013] In one embodiment of the present invention, the anomaly module includes a feature extraction unit, a working condition discrimination unit, and a strategy execution unit: wherein, the feature extraction unit is used to perform statistical analysis on the collected real-time pressure and the stator current fed back by the motor monitor within a set time window, and obtain the pressure standard deviation, current standard deviation, pressure mean, and current mean based on the statistical analysis results.

[0014] The operating condition discrimination unit is used to calculate the discrimination factor based on the pressure standard deviation, current standard deviation, pressure mean, and current mean, and based on the feature discrimination formula; the strategy execution unit is used to compare the pressure mean with the high pressure threshold and compare the discrimination factor with the set standard, and determine whether the system is in the pipe blockage state or surge state based on the comparison result, and generate the disturbance command or anti-surge command respectively.

[0015] In one embodiment of the present invention, the operating condition discrimination unit calculates a discrimination factor based on the pressure standard deviation, current standard deviation, pressure mean, and current mean, and based on a feature discrimination formula, including: using the weighting coefficient of the pressure fluctuation feature to perform a weighted calculation on the ratio of the pressure standard deviation to the pressure mean, and using the weighting coefficient of the current fluctuation feature to perform a weighted calculation on the ratio of the current standard deviation to the current mean; and adding the results of the two weighted calculations to obtain the discrimination factor.

[0016] In one embodiment of the present invention, the specific execution logic of the strategy execution unit includes: maintaining the operation of the closed-loop module when the average pressure is not higher than the high pressure threshold; determining the pipe blockage state when the average pressure is higher than the high pressure threshold and the discrimination factor is less than or equal to a set standard, generating a disturbance command, and controlling the variable frequency drive to execute a pulse disturbance mode; and determining the surge state when the average pressure is higher than the high pressure threshold and the discrimination factor is greater than the set standard, generating an anti-surge command, and controlling the variable frequency drive to execute a forced speed reduction action.

[0017] In one embodiment of the present invention, the shutdown module includes a line-sweeping control unit and an inertial interlocking unit; wherein, the line-sweeping control unit is used to generate a line-sweeping command after receiving a shutdown command, drive the centrifugal levitation fan to enter a high-flow-rate, low-pressure state for a set line-sweeping time, and empty the residual mineral powder in the direct-connection conveying pipeline; the inertial interlocking unit is used to send a power-off command after the line-sweeping command ends, and use the rotor inertia of the centrifugal levitation fan to slide freely, so that the pressure at the first air outlet naturally decreases, and cooperates with the check valve to achieve the anti-backflow shutdown.

[0018] A control method for a high-efficiency and energy-saving variable frequency permanent magnet blower for a mineral powder feeding system, based on the aforementioned high-efficiency and energy-saving variable frequency permanent magnet blower for a mineral powder feeding system, includes the following steps: A start-up module responds to a start-up command by controlling a variable frequency drive to establish a pre-tensioning pressure through a pre-tensioning unit. After maintaining the pre-tensioning for a set time, a centrifugal suspension blower is controlled by an inflection point capture unit to perform a speed increase. The fluidization speed is locked when a sudden drop inflection point is detected in the real-time pressure curve fed back by a pressure sensor. A closed-loop module receives the real-time pressure and fluidization speed fed back by the pressure sensor, calculates the pressure deviation between the set pressure and the real-time pressure through a deviation calculation unit, calculates the frequency increase command using a PID calculation unit and a speed regulation formula, and sends a frequency control command to the variable frequency drive through a command output unit.

[0019] The anomaly module uses a feature extraction unit to collect characteristic data of the real-time pressure and stator current fed back by the motor monitor within a set time window. It calculates a discrimination factor using a condition discrimination unit and a feature discrimination formula, and compares the average pressure with a high-pressure threshold and the discrimination factor with a set standard through a strategy execution unit to distinguish between pipe blockage and surge states and execute disturbance or anti-surge commands respectively. The shutdown module responds to the shutdown command by controlling the centrifugal suspended fan to perform a line sweeping action through the line sweeping control unit and sending a power-off command through the inertial interlocking unit. It uses rotor inertial sliding in conjunction with a check valve to achieve anti-backflow shutdown.

[0020] As described above, the high-efficiency energy-saving variable frequency permanent magnet blower and its control method for a mineral powder feeding system of the present invention have the following beneficial effects: 1. The present invention replaces the traditional control method of bypassing pressure relief by using a combination architecture of centrifugal suspension blower, fully enclosed direct-connection conveying pipeline and check valve. The centrifugal suspension blower directly matches the load demand by using variable frequency speed regulation, avoiding the energy loss caused by pressure relief by the check valve. Combined with the rotor inertial sliding when the machine is stopped and the physical blockage of the check valve, it prevents high pressure backflow under the condition of no check valve, simplifies the pipeline structure and reduces maintenance costs.

[0021] 2. This invention utilizes a starting module to execute a segmented flexible starting strategy. First, the breathable cloth is tensioned by low-pressure pre-tensioning to eliminate the risk of airflow impact. Then, the fluidization state is accurately determined by the pressure derivative inflection point, and the optimal base speed is locked. Combined with closed-loop operation adjustment, the output frequency can be automatically adjusted according to the material level change in the silo, and the pipeline pressure is always maintained within the set range, thereby achieving adaptive matching and energy consumption optimization in the conveying process.

[0022] 3. This invention establishes a fault decoupling mechanism based on the statistical characteristics of pressure and current through an anomaly module, which solves the problem that a single pressure threshold cannot distinguish between physical blockage and pneumatic surge. Based on the discrimination factor, it accurately identifies the blockage state of low-fluctuation high pressure and the surge state of violently fluctuating high pressure, and executes pulse disturbance to clear the pipeline or force speed reduction to protect the equipment respectively, thereby improving the continuous operation capability while ensuring the safety of the fan. Attached Figure Description

[0023] Figure 1 This is a front view of the overall structure of the high-efficiency and energy-saving variable frequency permanent magnet blower for the mineral powder feeding system disclosed in this embodiment of the invention;

[0024] Figure 2 This is an overall structural block diagram of the high-efficiency and energy-saving variable frequency permanent magnet blower for the mineral powder feeding system disclosed in this embodiment of the invention;

[0025] Figure 3This is a flowchart of the control logic of the abnormal module in the high-efficiency energy-saving variable frequency permanent magnet fan for the mineral powder feeding system disclosed in this embodiment of the invention.

[0026] Figure 4 This is a flowchart of the control logic of the shutdown module in the high-efficiency energy-saving variable frequency permanent magnet fan for the mineral powder feeding system disclosed in this embodiment of the invention.

[0027] Figure 5 This is a flowchart illustrating the overall architecture of the control method for a high-efficiency, energy-saving variable frequency permanent magnet fan used in a mineral powder feeding system, as disclosed in this embodiment of the invention.

[0028] Component designation explanation

[0029] 1. Chassis; 2. Centrifugal suspension fan; 3. First air inlet; 4. Second air inlet; 5. First air outlet; 6. Second air outlet; 7. Direct-connected conveying pipeline; 8. Check valve; 9. Pressure sensor. Detailed Implementation

[0030] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. It should be noted that, unless otherwise specified, the following embodiments and features described herein can be combined with each other.

[0031] The first embodiment of the present invention relates to a high-efficiency and energy-saving variable frequency permanent magnet fan for a mineral powder feeding system. Please refer to the following for details. Figure 1 and Figure 2 This device is applied to pneumatic conveying scenarios in mineral powder feeding systems. It includes a chassis 1, inside which is a centrifugal suspension fan 2. The centrifugal suspension fan 2 has a first air inlet 3, a second air inlet 4, a first air outlet 5, and a second air outlet 6. The first air inlet 3 is an air inlet, the second air inlet 4 is a fan cooling inlet, the first air outlet 5 is a main duct outlet, and the second air outlet 6 is a cooling venting outlet. The centrifugal suspension fan 2 adopts a built-in permanent magnet motor direct drive and air suspension bearing support structure, and integrates a frequency converter driver to draw in ambient air and output variable frequency adjustable high-speed airflow. A motor monitor is integrated inside the frequency converter driver to collect the motor's operating electrical parameters and output operating frequency, stator current, and torque data.

[0032] The first air outlet 5 of the centrifugal levitation fan 2 is connected to the air filling box at the bottom of the silo of the mineral powder feeding system via a direct-connection conveying pipe 7. One end of the direct-connection conveying pipe 7 is connected to the first air outlet 5 of the centrifugal levitation fan 2, and the other end is connected to the air filling box at the bottom of the silo of the mineral powder feeding system. The direct-connection conveying pipe 7 is configured as a fully enclosed direct air supply circuit, eliminating the conventional venting valve used for regulation, and is only used to establish a closed airflow transmission channel. The check valve 8 is installed in series on the main line of the direct-connection conveying pipe 7, located between the centrifugal levitation fan 2 and the feeding silo, to physically block the airflow and reverse flow of mineral powder. The pressure sensor 9 is installed on the direct-connection conveying pipe 7 to collect the static pressure signal in the pipe and output the real-time pressure. In practical applications, the pressure sensor 9 is also arranged at various key nodes of the system and is also used to monitor the filter pressure difference and the inlet and outlet pressure difference of the fan.

[0033] The variable frequency drive, motor monitor, and pressure sensor 9 are all connected to the main controller. The main controller is connected to the motor monitor, pressure sensor 9, and the variable frequency drive of the centrifugal suspending fan 2 via an industrial communication bus. It is used to receive sensor data and send control signals such as frequency control commands to the variable frequency drive. The main controller has a built-in control system configured to perform logical operations and strategy distribution during the mineral powder feeding process. The control system includes a start-up module, a closed-loop module, an exception module, and a shutdown module.

[0034] The startup module manages the transition process of the centrifugal suspending fan from a static state to a closed-loop fluidized bed state. The startup module is configured to execute a segmented flexible startup strategy. By controlling the output characteristics of the centrifugal suspending fan and cooperating with the pressure feedback in the direct-connection delivery pipeline 7, it achieves pressure control of the air-permeable cloth in the air-filled box and determines the minimum fluidization state. The startup module includes a pre-tensioning unit and an inflection point capture unit. The pre-tensioning unit and the inflection point capture unit work together to complete the transition from a static system to the establishment of a stable fluidized bed.

[0035] Upon receiving a start command, the pre-tensioning unit generates a pre-pressure command. The frequency converter drives the motor to output a constant low speed according to this command, establishing a pre-pressure within the direct-connection conveying pipeline. This pre-pressure continuously acts on the breathable fabric inside the inflation box, maintaining a set value for a specified time. Subsequently, the pretensioning unit outputs a pretensioning signal to the inflection point capture unit; after being triggered, the inflection point capture unit generates a climbing command, controls the frequency converter driver to perform an acceleration action, and simultaneously calculates the time derivative of the real-time pressure. When the calculation results show that the pressure curve has an inflection point, that is, the pressure drops slightly after the speed increases, the inflection point capture unit determines that the air path has been opened, records the current speed as the fluidization speed, and sends it to the closed-loop module. The pre-tensioning time is set in advance based on the mechanical response characteristics of the breathable fabric.

[0036] Furthermore, after the system is powered on and receives the start command, the pre-tensioning unit is activated first. The pre-tensioning unit generates a pre-pressure command and sends it to the frequency converter. In response to the pre-pressure command, the frequency converter drives the permanent magnet motor of the centrifugal suspension fan to run at a constant low speed, thereby establishing and maintaining a pre-pressure in the direct-connection conveying pipeline and the air box. The pre-pressure is set according to the physical resistance characteristics of the breathable cloth in the air box. The physical resistance characteristics are obtained through offline calibration or preset breathable cloth parameters. The value is set to be sufficient to overcome the weight and initial tension of the breathable cloth itself, so that it changes from a relaxed state to a flat and taut state. However, the value is not enough to overcome the static pressure resistance of the mineral powder layer above. That is, the mineral powder layer has not yet been blown through or fluidized. The specific value of the pre-pressure is determined according to the material density of the breathable cloth and the geometric dimensions of the air box, for example, set as a constant value between 2 kPa and 5 kPa.

[0037] The pretensioning unit controls the duration of the pre-tension to reach the set value. , setting value It is set based on the mechanical response time of the breathable fabric under the action of airflow, in order to ensure that the breathable fabric completely eliminates mechanical wrinkles and forms uniform air cushion support, for example, set to 5 to 15 seconds; through this low-pressure pre-inflation method, the system avoids the pressure impact of the instantaneous high-pressure airflow on the breathable fabric in a relaxed state when the traditional fan is hard-started.

[0038] When the duration reaches the set value Subsequently, the pre-tensioning unit generates a pre-tensioning signal and transmits it to the inflection point capture unit, triggering the next stage of control logic. Upon receiving this signal, the inflection point capture unit generates a climb command and sends it to the frequency converter driver, controlling the centrifugal suspending fan speed to increase linearly according to a preset slope or according to an S-curve. During the speed climb, the pressure in the direct-connection delivery pipeline will rise accordingly. The inflection point capture unit reads the real-time pressure feedback from the pressure sensor and calculates the derivative of the real-time pressure with respect to time in real time. In the physical process of pneumatic conveying, the resistance of the material layer will increase first as the air supply increases;

[0039] The moment gas can penetrate the material bed and establish a fluidization channel, the material bed transforms from a fixed bed to a fluidized bed, and the system back pressure exhibits a characteristic slight drop or a decrease in the rate of pressure rise; the inflection point capture unit monitors this. The change in pressure is detected when the calculation results show an inflection point in the pressure curve. From positive to negative value or When the value falls below the preset inflection point threshold, the gas path is determined to be fully open. This inflection point threshold is determined based on the critical fluidization characteristics of the mineral powder and the volumetric hysteresis characteristics of the pipeline system, for example, it is set to -0.1 kPa / s. Once an inflection point is determined, the inflection point capture unit immediately locks the current motor operating speed and records it as the fluidization speed. This fluidization speed represents the minimum energy consumption speed required to maintain the minimum fluidization state of the mineral powder at the current material level in the silo. Subsequently, the inflection point capture unit sends this fluidization speed as a reference parameter to the closed-loop module, marking the end of the start-up process and the system switching to the closed-loop regulation state.

[0040] The closed-loop module is used for automatic pressure balance control during the normal conveying phase. The closed-loop module includes a deviation calculation unit, a PID calculation unit, and an instruction output unit. The closed-loop module is configured to perform pressure-based automatic balance control after the system enters the normal conveying phase. Relying on the logical operations of the deviation calculation unit, PID calculation unit, and instruction output unit, the closed-loop module maintains constant pressure in the direct conveying pipeline by adjusting the operating frequency of the centrifugal suspension fan in real time without the participation of the vent valve. After entering the normal conveying state, the closed-loop module continuously receives the real-time pressure collected by the pressure sensor 9 and the set pressure provided by the system preset parameters. The set pressure is determined based on the conveying distance of the mineral powder feeding system, the bulk density of the mineral powder, and the required fluidization velocity, for example, set to 40 kPa to 60 kPa.

[0041] The deviation calculation unit reads the set pressure and the real-time pressure, and calculates the pressure deviation between them; the PID calculation unit calculates the frequency increase command based on the pressure deviation using the speed regulation formula; the speed regulation formula is as follows: In the formula: For the first The frequency increment command is output to the frequency converter driver at the next sampling time; This is the proportionality coefficient; The integral coefficient; These are the differential coefficients; For the current number Pressure deviation between the set pressure and the real-time pressure at the next sampling time; The summation operator is used to accumulate the sequence. For the cumulative variable in the summation operation, it changes from 0 to... ; For the first Pressure deviation at the next sampling time; The previous sampling time, i.e., the first The pressure deviation is measured; the command output unit superimposes the frequency increase command onto the current operating frequency to generate the final frequency control command, which is then sent to the frequency converter drive;

[0042] In other words, the deviation calculation unit periodically reads the set pressure and the real-time pressure, and calculates the difference between the two to generate a pressure deviation. This pressure deviation reflects the degree of mismatch between the current air supply capacity of the pneumatic conveying system and the load demand. If the pressure deviation is positive, it indicates that the current air supply pressure is insufficient and the speed needs to be increased. If the pressure deviation is negative, it indicates that the current air supply pressure is too high and the speed needs to be reduced.

[0043] The PID calculation unit receives the pressure deviation and performs calculations based on the discrete PID control algorithm to generate a frequency increase command for adjusting the motor speed. The speed regulation formula used by the PID calculation unit is as follows: The proportionality coefficient in the above formula Integral coefficient and differential coefficients It is determined based on the rotational inertia of the centrifugal levitation fan and the aerodynamic characteristics of the directly connected conveying pipeline. For example, for long-distance conveying pipelines, the integral coefficient... The value is usually set relatively small to avoid integral saturation; the PID calculation unit uses this formula to calculate the frequency adjustment required at the current sampling moment, i.e., the frequency increase instruction;

[0044] The command output unit superimposes the frequency increment command onto the current operating frequency of the centrifugal levitation fan. At the initial moment of closed-loop control, the current operating frequency is the frequency corresponding to the fluidization speed transmitted by the start-up module. In subsequent operation, this operating frequency is the final output frequency of the previous control cycle. The command output unit sends the superimposed calculation result as the final frequency control command to the frequency converter. The frequency converter adjusts the speed of the permanent magnet motor according to the frequency control command, changing the output air volume and air pressure of the centrifugal levitation fan. When the material level in the hopper decreases, causing the back pressure to decrease, the real-time pressure drops and the pressure deviation increases. The PID calculation unit outputs a positive frequency increment command to increase the speed to maintain the set pressure. Conversely, when the material level increases or the pipeline resistance increases, the system automatically adjusts the speed to adapt to the load change.

[0045] Please see Figure 3 The anomaly module is used to distinguish and handle pipe blockage and surge faults in real time. The anomaly module includes a feature extraction unit, a working condition discrimination unit, and a strategy execution unit. The anomaly module is configured to run in parallel with the closed-loop module to distinguish between physical pipe blockage and aerodynamic surge. The handling logic for these two faults is different: pipe blockage requires increasing airflow disturbance to clear it, while surge requires reducing the load or changing the speed.

[0046] Within a set time window, the feature extraction unit performs statistical analysis on the collected real-time pressure and stator current, calculating the standard deviation of pressure, the standard deviation of current, the mean pressure, and the mean current. The operating condition discrimination unit uses the above statistical data to calculate the discrimination factor based on the feature discrimination formula, which is as follows: In the formula: As the discriminant factor; The weighting coefficients for pressure fluctuation characteristics; The standard deviation of pressure for real-time pressure within a set time window; The average pressure value for real-time pressure within a set time window; The weighting coefficients for the current fluctuation characteristics; To set the standard deviation of the stator current within the set time window; To set the average stator current within a given time window, the weighting coefficient for pressure fluctuation characteristics is... Weighting coefficients for current fluctuation characteristics It is preset based on the signal-to-noise ratio of the pressure sensor and motor monitor;

[0047] The strategy execution unit compares the average pressure with the high-pressure threshold and the discrimination factor with the set standard: when the average pressure is higher than the high-pressure threshold and the discrimination factor is less than or equal to the set standard, the strategy execution unit determines that the system is in a blocked state and generates a disturbance command to send to the frequency converter; when the average pressure is higher than the high-pressure threshold and the discrimination factor is greater than the set standard, the strategy execution unit determines that the system is in a surge state and generates an anti-surge command, i.e., a forced speed reduction signal, to send to the frequency converter. The high-pressure threshold is preset based on the design pressure bearing capacity of the direct-connected conveying pipeline 7, and the set time window is preset based on the surge frequency characteristics of the centrifugal suspended fan and the pressure fluctuation cycle of the direct-connected conveying pipeline 7.

[0048] Furthermore, the feature extraction unit reads the real-time pressure collected by the pressure sensor and the stator current collected by the motor monitor in real time. The feature extraction unit sets a rolling time window, the length of which is determined based on the surge frequency characteristics of the centrifugal levitation fan and the period of pipeline pressure fluctuation, for example, set to 2 to 5 seconds. Within this time window, the feature extraction unit performs statistical analysis on the sampled data and calculates the pressure standard deviation of the real-time pressure. and average pressure and the standard deviation of the stator current. and average current Pressure standard deviation and current standard deviation These respectively characterize the degree of fluctuation in airflow pressure and motor load;

[0049] The operating condition discrimination unit receives the above statistical characteristic data and uses the characteristic discrimination formula to calculate the operating condition characteristic discrimination factor to quantify the fluctuation state of the current system. The characteristic discrimination formula is as follows: The weighting coefficients in the above formula and It is determined based on the signal-to-noise ratio of the system sensors and the coupling characteristics of the fan and duct. Larger values ​​are used to emphasize the judgment of aerodynamic characteristics, for example... Set to 0.6 to 0.8. Set to 0.2 to 0.4, this formula allows the operating condition discrimination unit to integrate the normalized fluctuation characteristics of pressure and current into a scalar index, namely the discrimination factor. ;

[0050] The strategy execution unit performs hierarchical decision-making based on the average pressure and the discrimination factor. The strategy execution unit first compares the average pressure with the high pressure threshold. The high pressure threshold is set based on the design pressure bearing capacity of the direct-connected conveying pipeline and the maximum exhaust pressure of the centrifugal suspended fan. It is used to determine whether the system is in a high-load danger zone, for example, it is set to 80 kPa.

[0051] If the average pressure is not higher than the high-pressure threshold, the system is judged to be under normal or general high load and continues to maintain closed-loop control; if the average pressure is higher than the high-pressure threshold, the strategy execution unit further calculates the discrimination factor. The comparison is made with a set standard, which is based on the statistical value of typical fluctuation amplitude when surge occurs, for example, set to 0.15; when the average pressure is higher than the high-pressure threshold and the discrimination factor... When the value is less than or equal to the set standard, the strategy execution unit determines that the system is in a blocked state. At this time, the strategy execution unit generates a disturbance command and sends it to the frequency converter driver. The frequency converter driver executes the pulse disturbance mode and controls the output frequency of the centrifugal suspension fan to rapidly alternate between the current reference frequency and the current reference frequency, for example, fluctuating with an amplitude of ±5Hz and a frequency of 1Hz, using the generated airflow pulsation to loosen the blockage point in the pipe.

[0052] When the mean pressure is higher than the high pressure threshold and the discriminant factor When the value exceeds the set standard, the strategy execution unit determines that the system is in a surge state. At this time, the strategy execution unit generates an anti-surge command and sends it to the frequency converter driver. The frequency converter driver performs a forced speed reduction action to quickly reduce the motor speed, so that the operating point of the fan quickly leaves the surge boundary and prevents equipment damage. The set standard is preset based on the statistical value of the fluctuation amplitude when the surge occurs.

[0053] Please see Figure 4 The shutdown module is used to perform self-cleaning safety shutdown in a valveless environment. It is configured to execute a valveless self-cleaning safety shutdown strategy. The shutdown module includes a line-sweeping control unit and an inertial interlocking unit, which work in sequence to ensure safe system shutdown. Upon receiving a shutdown command, the line-sweeping control unit generates a line-sweeping command, and the frequency converter driver controls the centrifugal suspension fan to enter a high-flow-rate, low-pressure state for a set line-sweeping time based on this command. The residual mineral powder in the direct-connection conveying pipeline is blown into the silo; after the sweeping command is completed, the inertial interlocking unit sends a power-off command to the frequency converter driver, and the centrifugal suspension fan uses the rotor inertia to slide freely, causing the outlet pressure to naturally decrease. This, combined with the check valve, achieves anti-backflow shutdown. The sweeping time is set. It is preset based on the physical length of the direct-connection conveying pipeline and the flow rate of the sweeping airflow;

[0054] Furthermore, the sweeping control unit starts in response to a stop command from the human-machine interface. Upon receiving the stop command, the sweeping control unit generates a sweeping command and sends it to the frequency converter driver. The frequency converter driver controls the centrifugal suspension fan to enter sweeping mode, adjusting the motor speed to a specific ratio of its rated speed (e.g., 80% to 90%), causing the fan to output a high-velocity airflow. This high-velocity airflow is used to purge the direct-connection conveying pipeline after material stoppage, blowing all residual mineral powder in the pipeline into the hopper for emptying. The sweeping control unit maintains this sweeping state for a duration of [duration missing]. , It is calculated and set based on the physical length of the direct-connection delivery pipeline, the pipeline diameter, and the average flow rate of the sweeping airflow to ensure that the airflow can complete at least one replacement of the entire pipeline, for example, set to 30 to 60 seconds.

[0055] When the scanning mode running time reaches Afterwards, the sweep control unit stops outputting and switches the logic to the inertial interlock unit. The inertial interlock unit then generates a power-off command and sends it to the frequency converter driver to cut off the power input of the permanent magnet motor. At this time, because the centrifugal levitation fan is supported by an air suspension bearing, there is no mechanical friction between the rotor and the bearing, and the permanent magnet rotor has a large moment of inertia. The fan rotor will not stop immediately, but will enter a free gliding state. During the gliding process, the fan speed decreases over time, and the pressure output from its outlet also decreases accordingly.

[0056] This pressure decay process, achieved through inertial gliding, maintains a gradually decreasing but always positive pressure differential between the direct-connection conveying pipeline and the blower, with the direction always pointing towards the silo. This positive pressure differential persists until the rotational speed drops to a low level, preventing backflow of mineral powder due to sudden changes in back pressure at the moment of shutdown. As the pressure at the blower outlet further decreases, when it falls below the residual pressure in the direct-connection conveying pipeline or the back pressure of the silo, the check valve installed in series on the main pipeline automatically closes under the action of the pressure differential, physically blocking the air path. The inertial interlocking unit utilizes this physical process to achieve a safe shutdown of the system, ensuring that high-pressure gas and materials will not backflow into the blower cavity without active pressure relief from the vent valve.

[0057] The second embodiment of the present invention relates to a control method for a high-efficiency and energy-saving variable frequency permanent magnet fan used in a mineral powder feeding system. Please refer to the following for details. Figure 5 This method, based on the aforementioned hardware architecture and control system, achieves intelligent and efficient operation of the mineral powder feeding process through four core steps: segmented flexible start-up, closed-loop operation adjustment, decoupling handling of abnormal working conditions, and inertial line sweeping self-cleaning shutdown. The control method specifically includes the following steps:

[0058] Step S101: Execute the segmented flexible start-up strategy: In response to the start-up command, the start-up module controls the frequency converter to establish a pre-tensioning pressure through the pre-tensioning unit. After maintaining the set pre-tensioning time, it controls the centrifugal suspension fan to perform speed increase through the inflection point capture unit. When the real-time pressure curve fed back by the pressure sensor shows a sudden drop inflection point, the fluidization speed is locked.

[0059] Specifically, in response to an externally input start command, the start module first controls the frequency converter to drive the centrifugal suspension fan at a constant low speed. The centrifugal suspension fan establishes a pre-pressure in the direct-connection delivery pipeline. This pre-pressure continuously acts on the breathable fabric in the inflation box, enabling it to overcome physical resistance and complete flattening and tensioning, eliminating mechanical wrinkles. The system maintains this pre-pressure state until the set pre-tensioning time is reached. ;

[0060] Once the set time is reached, the system controls the centrifugal suspension fan to perform a speed increase action and uses the inflection point capture unit to monitor the time derivative of the real-time pressure fed back by the pressure sensor in real time. During the speed increase process, once the calculated time derivative shows a sudden drop in the pressure curve from rising to falling, the system determines that the air path is completely open, immediately locks the current motor speed and records it as the basic fluidization speed, and then transfers control to the closed-loop operation adjustment stage.

[0061] Step S102: Execute the closed-loop operation adjustment strategy: The closed-loop module receives the real-time pressure and fluidization speed feedback from the pressure sensor, calculates the pressure deviation between the set pressure and the real-time pressure through the deviation calculation unit, calculates the frequency increase command using the PID calculation unit and the speed regulation formula, and sends the frequency control command to the frequency converter through the command output unit.

[0062] Specifically, after entering the normal conveying stage, the closed-loop module periodically acquires the real-time pressure collected by the pressure sensor and compares it with the system's preset target pressure to calculate the pressure deviation. The PID calculation unit receives the pressure deviation and performs discrete PID calculation using the speed regulation formula to calculate the frequency increment command required at the current moment. The command output unit converts the frequency increment command into a frequency control command and sends it to the frequency converter to dynamically adjust the operating frequency of the centrifugal suspension fan in real time. Through this step, the system automatically increases or decreases the output air volume according to the dynamic changes in the material level in the silo without the participation of the vent valve, always maintaining the pressure in the direct conveying pipeline constant near the set value.

[0063] Step S103: Execute abnormal operating condition decoupling and handling strategy: The abnormal module uses the feature extraction unit to collect real-time pressure and stator current feature data fed back by the motor monitor within a set time window, calculates the discrimination factor using the operating condition discrimination unit and feature discrimination formula, and compares the average pressure with the high pressure threshold and the discrimination factor with the set standard through the strategy execution unit to distinguish between pipe blockage state and surge state and execute disturbance command or anti-surge command respectively.

[0064] Specifically, during the entire system operation process, the anomaly module monitors the system operating conditions in parallel; the feature extraction unit continuously collects real-time pressure and stator current fed back by the motor monitor, and performs statistical analysis on the data within the sliding time window to calculate the pressure standard deviation, current standard deviation, pressure mean, and current mean; the operating condition discrimination unit uses the above statistical feature data and applies the feature discrimination formula to calculate the operating condition feature discrimination factor.

[0065] The strategy execution unit compares the average pressure with the high-pressure threshold in real time and compares the operating condition characteristic discrimination factor with the set standard. If the average pressure exceeds the high-pressure threshold and the operating condition characteristic discrimination factor is less than the set standard, the system identifies it as a pipe blockage state, and the frequency converter executes a disturbance command to control the fan frequency to rapidly alternate and jump to clear the pipe. If the average pressure exceeds the high-pressure threshold and the operating condition characteristic discrimination factor is greater than the set standard, the system identifies it as a surge state, and the frequency converter executes an anti-surge command to forcibly reduce the speed so that the operating point is out of the surge zone.

[0066] Step S104: Execute the inertial sweeping self-cleaning shutdown strategy: The shutdown module responds to the shutdown command, controls the centrifugal suspended fan to perform the sweeping action through the sweeping control unit, and sends a power-off command through the inertial interlocking unit. The rotor inertial sliding, in conjunction with the check valve, achieves anti-backflow shutdown.

[0067] Specifically, when a shutdown command is received, the shutdown module does not immediately cut off the power, but instead controls the centrifugal suspension fan to enter the line sweeping mode; the frequency converter drives the fan to run at a high flow rate for a duration reaching the set value. The system uses high-speed airflow to blow all the suspended mineral powder remaining in the direct-connection conveying pipeline into the silo for emptying. After the sweeping process is completed, the system sends a power-off command to cut off the power input of the permanent magnet motor. The centrifugal suspension fan uses the high-speed rotational inertia of the rotor to enter a free-sliding state, causing the pressure in the direct-connection conveying pipeline to naturally decrease as the speed decreases. During this process, the check valve automatically closes under the action of pressure difference, physically blocking the air path, thereby preventing the high-pressure mineral powder in the silo from flowing back into the fan under the condition of no venting valve, and achieving safe shutdown.

[0068] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. All equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this invention should still be covered by the claims of this invention.

Claims

1. A high-efficiency, energy-saving variable frequency permanent magnet blower for a mineral powder feeding system, characterized in that: Includes a chassis (1), wherein a centrifugal suspension fan (2) is provided inside the chassis (1), wherein a variable frequency drive is provided inside the centrifugal suspension fan (2) for drawing in ambient air and outputting variable frequency adjustable high-speed airflow, wherein a motor monitor is provided inside the variable frequency drive for collecting the operating electrical indicators of the motor and outputting operating frequency, stator current and torque data; The first air outlet (5) of the centrifugal suspension fan (2) is connected to the air-filling box at the bottom of the ore powder feeding system silo via a direct-connection conveying pipe (7). The direct-connection conveying pipe (7) is equipped with a check valve (8) located between the centrifugal suspension fan (2) and the feeding silo, which is used to physically block the airflow and reverse flow of ore powder. The direct-connection conveying pipe (7) is also equipped with a pressure sensor (9) for collecting static pressure signals in the pipe and outputting real-time pressure. The frequency converter, motor monitor and pressure sensor (9) are all connected to the main controller.

2. The high-efficiency energy-saving variable frequency permanent magnet blower for a mineral powder feeding system according to claim 1, characterized in that: The main controller is equipped with a control system for receiving sensor data and sending control signals such as frequency control commands to the frequency converter driver, and the control system includes a start-up module, a closed-loop module, an abnormal module and a shutdown module. The starting module is used to control the frequency converter to execute segmented starting logic and output fluidized speed based on the real-time pressure fed back by the pressure sensor (9); The closed-loop module is used to receive the real-time pressure and fluidization speed, and adjust the operating frequency of the centrifugal suspension fan (2) by calculating the deviation between the set pressure and the real-time pressure. The anomaly module is used to distinguish between pipe blockage and surge states based on the real-time pressure and the stator current fed back by the motor monitor using statistical analysis methods, and to generate disturbance commands or anti-surge commands respectively. The shutdown module is used to control the centrifugal suspension fan (2) to perform a sweeping action to empty the direct-connection conveying pipeline (7), and to control the frequency converter to cut off the power supply so as to use the pressure generated by the rotor inertia to naturally decay and achieve anti-backflow shutdown.

3. The high-efficiency energy-saving variable frequency permanent magnet blower for a mineral powder feeding system according to claim 2, characterized in that: The startup module includes a pre-tensioning unit and an inflection point capture unit; The pre-tensioning unit is used to generate a pre-pressure command after receiving the start command, drive the centrifugal suspension fan (2) to output a constant low speed according to the pre-pressure command, establish a pre-pressure in the direct-connection conveying pipeline (7), maintain the set pre-tensioning time, and output a pre-tensioning signal. The inflection point capture unit is used to generate a climbing command in response to the pre-tensioning signal, control the centrifugal suspension fan (2) to accelerate, and receive the real-time pressure feedback from the pressure sensor (9). At the same time, it calculates the time derivative of the real-time pressure in real time. When it is determined that the pressure curve has a sudden drop inflection point, it locks the current speed as the fluidization speed.

4. The high-efficiency energy-saving variable frequency permanent magnet blower for a mineral powder feeding system according to claim 2, characterized in that: The closed-loop module includes a deviation calculation unit, a PID calculation unit, and an instruction output unit: The deviation calculation unit is used to read the set pressure and the real-time pressure, and calculate the pressure deviation between them; the PID calculation unit is used to calculate the frequency increase command based on the pressure deviation and the speed regulation formula; the command output unit is used to superimpose the frequency increase command on the current operating frequency of the variable frequency drive, generate a frequency control command, and send it to the variable frequency drive.

5. The high-efficiency energy-saving variable frequency permanent magnet blower for a mineral powder feeding system according to claim 4, characterized in that: The PID calculation unit calculates the frequency increase command based on the pressure deviation and using the speed regulation formula, including: The pressure deviation at the current moment is proportionally calculated using a proportionality coefficient, the historical cumulative value of the pressure deviation is integrally calculated using an integral coefficient, and the rate of change of the pressure deviation is differentially calculated using a differential coefficient. The results of the proportional, integral, and differential operations are summed to generate the frequency increase command, which is then sent to the frequency converter.

6. The high-efficiency energy-saving variable frequency permanent magnet blower for a mineral powder feeding system according to claim 2, characterized in that: The anomaly module includes a feature extraction unit, a working condition discrimination unit, and a strategy execution unit: The feature extraction unit is used to perform statistical analysis on the real-time pressure and stator current fed back by the motor monitor within a set time window, and obtain the pressure standard deviation, current standard deviation, pressure mean and current mean based on the statistical analysis results. The operating condition discrimination unit is used to calculate the discrimination factor based on the pressure standard deviation, current standard deviation, pressure mean, and current mean, and based on the feature discrimination formula. The strategy execution unit is used to compare the average pressure with the high pressure threshold and the discrimination factor with the set standard. Based on the comparison result, it determines whether the system is in the pipe blockage state or the surge state, and generates the disturbance command or anti-surge command respectively.

7. The high-efficiency energy-saving variable frequency permanent magnet blower for a mineral powder feeding system according to claim 6, characterized in that: The operating condition discrimination unit calculates discrimination factors based on the pressure standard deviation, current standard deviation, pressure mean, and current mean, and based on the feature discrimination formula, including: The ratio of the pressure standard deviation to the pressure mean is calculated using a weighting coefficient based on the pressure fluctuation characteristics, and the ratio of the current standard deviation to the current mean is calculated using a weighting coefficient based on the current fluctuation characteristics. The discriminant factor is obtained by adding the results of the two weighted calculations.

8. A high-efficiency energy-saving variable frequency permanent magnet blower for a mineral powder feeding system according to claim 6, characterized in that: The specific execution logic of the strategy execution unit includes: When the average pressure is not higher than the high pressure threshold, the closed-loop module continues to operate; When the average pressure is higher than the high pressure threshold and the discrimination factor is less than or equal to the set standard, it is determined to be a pipe blockage state, a disturbance command is generated, and the frequency converter is controlled to execute the pulse disturbance mode. When the average pressure is higher than the high pressure threshold and the discrimination factor is greater than the set standard, it is determined to be a surge state, an anti-surge command is generated, and the variable frequency drive is controlled to perform a forced speed reduction action.

9. A high-efficiency energy-saving variable frequency permanent magnet blower for a mineral powder feeding system according to claim 2, characterized in that: The shutdown module includes a sweep control unit and an inertial interlocking unit; The sweeping control unit is used to generate a sweeping command after receiving a shutdown command, drive the centrifugal suspension fan (2) to enter a high flow rate and low pressure state to set a sweeping time, and empty the residual mineral powder in the direct conveying pipeline (7). The inertial interlocking unit is used to send a power-off command after the sweeping command ends, and to use the rotor inertia of the centrifugal suspension fan (2) to slide freely, so that the pressure at the first air outlet (5) naturally decreases, and works with the check valve (8) to achieve the anti-backflow shutdown.

10. A control method for a high-efficiency and energy-saving variable frequency permanent magnet blower used in a mineral powder feeding system, characterized in that: The high-efficiency energy-saving variable frequency permanent magnet blower for the mineral powder feeding system according to any one of claims 1-9 includes the following steps: The starting module responds to the starting command, controls the frequency converter to establish the pre-tensioning pressure through the pre-tensioning unit, maintains the set pre-tensioning time, controls the centrifugal suspension fan (2) to perform speed increase through the inflection point capture unit, and locks the fluidization speed when the real-time pressure curve fed back by the pressure sensor (9) shows a sudden drop inflection point. The closed-loop module receives the real-time pressure and fluidization speed feedback from the pressure sensor (9), calculates the pressure deviation between the set pressure and the real-time pressure through the deviation calculation unit, calculates the frequency increase command using the PID calculation unit and the speed regulation formula, and sends the frequency control command to the frequency converter through the command output unit. The anomaly module uses the feature extraction unit to collect the feature data of the real-time pressure and the stator current fed back by the motor monitor within a set time window. It uses the operating condition discrimination unit and feature discrimination formula to calculate the discrimination factor. The strategy execution unit compares the average pressure with the high pressure threshold and the discrimination factor with the set standard to distinguish between the pipe blockage state and the surge state and executes the disturbance command or anti-surge command respectively. The shutdown module responds to the shutdown command by controlling the centrifugal suspended fan (2) to perform the sweeping action through the sweeping control unit, and sends a power-off command through the inertial interlocking unit. It uses the rotor inertial sliding in conjunction with the check valve (8) to achieve anti-backflow shutdown.

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