A skid-mounted variable frequency instrument control ventilation module capable of preventing sand and dust from entering and avoiding internal negative pressure
Patent Information
- Application Number
- CN202611366981.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-09-04
- Publication Date
- 2026-11-03
AI Technical Summary
The existing prefabricated substation ventilation system lacks an exhaust channel control mechanism and a fan status monitoring and early warning mechanism, which leads to problems such as excessive negative pressure inside the skid-mounted frequency converter equipment, inability to open the door, sand and dust intrusion into the equipment, difficulty in fan maintenance, and sand and dust backflow after shutdown.
The system employs a differential pressure detection module, a frequency converter control module, a centrifugal fan drive module, an exhaust backflow prevention control module, and a fault self-diagnosis module to achieve active control of the exhaust duct and real-time monitoring of the fan's operating status. The exhaust volume is adjusted through differential pressure detection and frequency conversion regulation. The exhaust backflow prevention control module automatically closes the duct when the centrifugal fan stops. Combined with the fault self-diagnosis module, the system can detect and forcibly close the duct in real time, ensuring a balance between the intake and exhaust volumes.
It effectively solves the risk of sand and dust intrusion and equipment damage caused by the lack of exhaust channel control and fan status monitoring, achieves negative pressure balance in skid-mounted frequency converter equipment, prevents sand and dust backflow, and ensures stable and safe operation of the equipment.
Smart Images
Figure CN123028366A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of ventilation control technology for skid-mounted variable frequency drives (VFDs), specifically to a skid-mounted VFD ventilation control module that prevents sand and dust intrusion and avoids internal negative pressure. Background Technology
[0002] Most of the prefabricated substations in the CNPC system are installed in harsh natural environments, such as those with sandstorms, rain, snow, high temperatures, and large temperature differences. Currently, during long-term operation, prefabricated substations (skid-mounted frequency converter equipment) have long faced problems such as the cooling fan's output exceeding the air intake through the louvers after the frequency converter compressor is working normally, resulting in a persistent negative pressure inside the skid. This leads to problems such as doors being unable to open properly, external dust being directly drawn into the skid through the air ducts causing severe dust accumulation inside the equipment, and dust and debris flowing back into the frequency converter through the exhaust vents after the frequency converter stops. These problems persist and are difficult to resolve.
[0003] The existing ventilation system has the following defects: It lacks a control mechanism for the exhaust duct and a real-time monitoring and fault warning mechanism for the fan's operating status. This results in the exhaust duct remaining open and uncontrollable under persistent negative pressure. When a fan malfunctions, the system cannot detect it in real time, making it difficult for maintenance personnel to promptly identify and address the issue, further increasing the risk of dust intrusion and equipment damage. Furthermore, the existing ventilation system lacks a control mechanism for the exhaust duct when the centrifugal fan is stopped. This means that after the frequency converter stops, the exhaust duct cannot automatically close when the centrifugal fan stops operating. The negative pressure inside the skid is not completely eliminated, allowing external dust and debris to continuously backflow into the frequency converter through the exhaust vents.
[0004] In summary, the existing ventilation systems in prefabricated substations lack control mechanisms for exhaust ducts and fan status monitoring and early warning mechanisms. Furthermore, they lack control mechanisms for exhaust ducts when centrifugal fans are shut down, resulting in persistent problems with dust intrusion and equipment contamination. There is an urgent need for a ventilation control technology solution that integrates real-time fan status monitoring, active exhaust duct control, and automatic shutdown upon shutdown. Summary of the Invention
[0005] This invention provides a skid-mounted frequency converter control ventilation module that prevents sand and dust intrusion and avoids internal negative pressure. It aims to solve the technical problems existing in the ventilation systems of prefabricated substations and skid-mounted frequency converters, such as excessive negative pressure causing doors to be unable to open, sand and dust intrusion into the equipment, difficulty in fan maintenance, and backflow during shutdown.
[0006] To achieve the above objectives, the present invention provides a skid-mounted inverter control ventilation module that prevents sand and dust intrusion and avoids internal negative pressure, comprising: The differential pressure detection module is installed inside the skid-mounted house to detect the air pressure difference between the inside of the skid-mounted house and the external environment in real time and output the corresponding differential pressure signal. The variable frequency control module is connected to the differential pressure detection module and is used to receive the differential pressure signal and generate a variable frequency drive signal based on the differential pressure signal. The variable frequency drive signal is used to adjust the operating frequency of the exhaust equipment. The centrifugal fan drive module is connected to the frequency converter control module for receiving the frequency converter drive signal and driving the centrifugal fan to operate at a corresponding speed according to the frequency converter drive signal, so as to adjust the exhaust volume of the skid-mounted house to the outside. The exhaust backflow prevention control module is linked with the centrifugal fan drive module and is used to control the closure of the exhaust duct when the centrifugal fan stops running, so as to prevent external sand and debris from flowing back into the skid-mounted house through the exhaust duct.
[0007] As a further improvement to the module of the present invention, it also includes an air intake compensation module, which is used to monitor the air intake status of the air intake channel of the skid-mounted house, and send a compensation request to the frequency converter control module when the air intake is lower than a preset threshold. The frequency converter control module adjusts the frequency converter drive signal according to the compensation request to adjust the exhaust volume so that the air intake and exhaust volumes are kept in balance.
[0008] As a further improvement to the module of the present invention, an internal circulation control module is also included, which is signal-connected to the centrifugal fan drive module and the differential pressure detection module. When the differential pressure signal indicates that the pressure difference between the inside and outside of the skid-mounted house exceeds the preset safety range and the centrifugal fan is in a low-speed or stopped state, the internal circulation duct is opened to allow the air inside the skid-mounted house to circulate internally.
[0009] As a further improvement to the module of the present invention, the frequency conversion control module has a built-in differential pressure-frequency mapping table, which is used to query the corresponding target operating frequency according to the real-time received differential pressure signal, and use the target operating frequency as the output reference of the frequency conversion drive signal.
[0010] As a further improvement to the module of the present invention, a fault self-checking module is also included, which is used to monitor the operating status of the centrifugal fan drive module in real time, and when a fault is detected in the centrifugal fan drive module, output a fault alarm signal and forcibly trigger the exhaust anti-backflow control module to perform the action of closing the exhaust channel.
[0011] This invention addresses the lack of exhaust duct control mechanisms and fan status monitoring and early warning mechanisms in existing ventilation systems. By incorporating an exhaust backflow prevention control module and a fault self-checking module, it achieves active control of the exhaust duct and real-time monitoring of the fan's operating status. The exhaust backflow prevention control module is linked to the centrifugal fan drive module. While the centrifugal fan is running, the exhaust duct remains open as needed. When a fan malfunctions, the fault self-checking module detects the issue in real time and forcibly triggers the closure of the exhaust duct. This effectively solves the problem of continuous dust intrusion and increased equipment damage risk caused by the lack of exhaust duct control and fan status monitoring and early warning mechanisms. Simultaneously, by incorporating a logic judgment unit linked to the centrifugal fan drive module, a shutdown command is automatically generated the instant the centrifugal fan stops operating, driving the electric damper actuator to close the exhaust duct. This solves the problem of dust backflow caused by the lack of exhaust duct control mechanisms when the centrifugal fan is stopped in existing ventilation systems. By actively controlling the exhaust duct and automatically closing it upon shutdown, the invention eliminates the pathways for dust to enter the equipment.
[0012] Furthermore, this invention achieves precise closed-loop control of the centrifugal fan speed by incorporating a differential pressure detection module and a frequency conversion control module. This ensures a dynamic balance between the air intake and exhaust volumes within the skid-mounted building, fundamentally solving the problem of excessive negative pressure preventing the doors from opening properly, while also preventing positive pressure. An air intake compensation module automatically adjusts the exhaust volume when the air intake volume decreases due to filter blockage, ensuring a constant balance between intake and exhaust. An internal circulation control module activates the internal circulation duct when the centrifugal fan is running at low speed or stopped, reducing the risk of external dust intrusion and achieving energy-saving operation. Upon completion and acceptance, the prefabricated substation using this invention has completely resolved previous problems such as excessive negative pressure, insufficient ventilation, excessive dust, filter deformation, reduced protection levels, and outdated control methods. The system operates stably and reliably. Attached Figure Description
[0013] Figure 1 This is a schematic diagram of a skid-mounted frequency converter control ventilation module of the present invention, which prevents sand and dust intrusion and avoids internal negative pressure. Detailed Implementation
[0014] Example 1 like Figure 1 As shown, this embodiment provides a skid-mounted frequency converter-controlled ventilation module that prevents sand and dust intrusion and avoids internal negative pressure, including a differential pressure detection module, a frequency converter control module, a centrifugal fan drive module, and an exhaust backflow prevention control module.
[0015] The differential pressure detection module is installed inside the skid-mounted cabin to detect the real-time pressure difference between the cabin's interior and the external environment, and generate a corresponding differential pressure signal. The module continuously collects the cabin's internal air pressure and external atmospheric pressure at a fixed sampling period, subtracts the two values to obtain the real-time differential pressure data, and calculates the rate of change of differential pressure based on the data from adjacent sampling times. The sign of the differential pressure data indicates the direction of the pressure state inside the skid, the absolute value of the differential pressure data indicates the magnitude of the deviation between the skid's internal and external atmospheric pressure, and the rate of change of differential pressure indicates the rate and trend of pressure change inside the skid. The differential pressure detection module packages the real-time differential pressure data and the rate of change of differential pressure together and outputs them to the frequency converter control module.
[0016] The variable frequency control module receives real-time differential pressure data and differential pressure change rate from the differential pressure detection module. Using the differential pressure data as the primary control variable and the differential pressure change rate as the feedforward correction variable, it performs closed-loop differential pressure regulation. The variable frequency control module internally stores a target differential pressure range. When the real-time differential pressure data falls within this range, the system is in equilibrium. At this point, the variable frequency control module further determines the direction of the differential pressure change rate: if the rate of change is zero or its absolute value is extremely small, the current output frequency remains unchanged; if the rate of change continues to accumulate in a certain direction, a small correction frequency opposite to that direction is output to suppress the gradual change caused by factors such as gradual blockage of the inlet filter or sudden changes in external wind speed, preventing the differential pressure from slowly drifting out of the target range over a long time scale.
[0017] When the real-time differential pressure data deviates from the target differential pressure range, the frequency converter control module first extracts the deviation. The direction of the deviation determines the adjustment direction, and the magnitude of the deviation determines the adjustment range. Simultaneously, the differential pressure change rate is introduced as an auxiliary decision variable. Specifically, the frequency converter control module inputs the deviation into the main mapping channel to obtain the basic target frequency; simultaneously, it inputs the differential pressure change rate into the feedforward correction channel to obtain the frequency correction. The frequency converter control module combines the basic target frequency and the frequency correction to generate the final target operating frequency. The direction of the frequency correction is opposite to the direction of the differential pressure change rate, and its magnitude is positively correlated with the magnitude of the change rate. Its physical meaning is: when the negative pressure inside the skid is rapidly increasing, even if the current deviation is small, the system applies a relatively large frequency reduction correction in advance; when the negative pressure inside the skid is slowly decreasing, even if the current deviation is large, the system appropriately reduces the frequency reduction amplitude to avoid over-adjustment.
[0018] The variable frequency control module encodes the final target operating frequency into a variable frequency drive signal and outputs it to the centrifugal fan drive module. After receiving the variable frequency drive signal, the centrifugal fan drive module drives the centrifugal fan to operate at the target frequency, adjusting the exhaust volume of the skid-mounted house.
[0019] While driving the centrifugal fan, the centrifugal fan drive module continuously monitors the fan's real-time operating parameters, including at least the operating current, operating frequency, and operating temperature. The module cross-compares these parameters with preset threshold parameters to generate a multi-dimensional state feature vector. This vector includes the following dimensions: the degree and direction of current deviation from the rated operating range, the frequency response deviation rate, and the temperature gradient. The centrifugal fan drive module then sends this state feature vector to the exhaust backflow prevention control module.
[0020] The centrifugal fan drive module compares the real-time operating current with the rated operating current of the centrifugal fan to calculate the current deviation and its direction. The magnitude of the current deviation characterizes the degree to which the current mechanical load rate of the centrifugal fan deviates from the design load rate, while the direction characterizes the direction of the deviation. A positive deviation indicates that the current load rate is higher than the rated load rate, reflecting increased exhaust duct resistance or increased impeller load; a negative deviation indicates that the current load rate is lower than the rated load rate, reflecting decreased exhaust duct resistance, impeller unloading, or slippage in the transmission mechanism. The centrifugal fan drive module further quantifies the current deviation into three zones: normal deviation zone, allowable deviation zone, and over-limit deviation zone. The allowable deviation zone corresponds to the safety margin range within which the centrifugal fan can operate continuously for a long period, while the over-limit deviation zone corresponds to the dangerous area where the centrifugal fan cannot operate continuously. The direction of the current deviation and the zone quantization results constitute the first dimension of the multi-dimensional state feature vector.
[0021] The centrifugal fan drive module compares the real-time operating frequency with the target operating frequency sent by the frequency converter control module, calculating the frequency response deviation rate. The frequency response deviation rate is the ratio of the difference between the real-time operating frequency and the target operating frequency to the target operating frequency. This ratio characterizes the centrifugal fan drive module's accuracy in following the frequency converter control command. The direction and amplitude of the frequency response deviation rate are determined by a combination of factors: a positive deviation rate indicates that the actual speed of the centrifugal fan is higher than the commanded speed, reflecting overshoot in the frequency converter output or excessive motor slip compensation; a negative deviation rate indicates that the actual speed of the centrifugal fan is lower than the commanded speed, reflecting insufficient frequency converter output voltage, limited motor torque output, or the centrifugal fan mechanical load exceeding the motor's drive capacity; when the fluctuation amplitude of the deviation rate exceeds the preset response band width, it indicates a dynamic mismatch between the frequency converter control loop and the centrifugal fan mechanical load, and the system is in a non-steady-state adjustment process. The value, direction, and fluctuation amplitude of the frequency response deviation rate constitute the second dimension of the multi-dimensional state feature vector.
[0022] The centrifugal fan drive module performs time-series analysis on the real-time operating temperature to calculate the temperature gradient. The temperature gradient is the ratio of the difference between the operating temperature at the current sampling moment and the operating temperature at the previous sampling moment to the sampling interval, characterizing the rate of temperature change in the centrifugal fan motor windings and bearings. The physical meaning of the temperature gradient is: a positive gradient indicates the system is in the heat accumulation stage, and a negative gradient indicates the system is in the heat dissipation stage; the absolute value of the gradient represents the intensity of heat accumulation or heat dissipation. The centrifugal fan drive module compares the real-time operating temperature with a preset temperature threshold system, which includes at least a temperature warning threshold and a temperature protection threshold, and performs direction determination and amplitude quantification of the temperature gradient. When the temperature gradient is positive and the real-time temperature has exceeded the temperature warning threshold, it indicates that the centrifugal fan will gradually approach the temperature protection threshold during continuous operation, and the remaining safe operating time is calculated in real-time from the temperature gradient amplitude; when the temperature gradient is negative or close to zero, it indicates that the centrifugal fan has reached thermal equilibrium and the temperature has stabilized. The threshold range of the real-time temperature and the direction and amplitude of the temperature gradient constitute the third dimension of the multi-dimensional state feature vector.
[0023] The centrifugal fan drive module integrates the above three dimensions into a three-dimensional state feature vector. The centrifugal fan drive module then sends this three-dimensional state feature vector to the exhaust backflow prevention control module.
[0024] After receiving the three-dimensional state feature vector, the exhaust backflow prevention control module performs the following multi-dimensional comprehensive judgment: When the coordinates of the three-dimensional state feature vector in the three-dimensional state space meet the following conditions, the first dimension (current deviation) is located in the normal deviation zone or the allowable deviation zone, the absolute value of the second dimension (frequency response deviation rate) is located within the preset response band width, and the third dimension (real-time temperature is below the temperature warning threshold and the temperature gradient is negative or close to zero), the exhaust backflow prevention control module determines that the system is in normal operation and the exhaust channel remains open.
[0025] When the first dimension of the three-dimensional state feature vector is within the allowable deviation zone and its direction is positive (i.e., positive current deviation), the absolute value of the second dimension exceeds the response band width and its direction is negative (i.e., the actual frequency is lower than the target frequency), and the real-time temperature of the third dimension is still below the temperature warning threshold but the temperature gradient is positive, the exhaust backflow prevention control module determines that the system is in an abnormal load state. This state indicates that the resistance of the exhaust channel is abnormally increased or that the centrifugal fan impeller is mechanically stuck. The frequency conversion control module calculates the frequency reduction amplitude based on the deviation of the first dimension and the deviation rate of the second dimension in the feature vector to reduce the centrifugal fan speed and reduce the mechanical load.
[0026] When the first dimension of the three-dimensional state feature vector is in the over-limit deviation zone, the absolute value of the second dimension exceeds the response band width and is negative, and the temperature gradient of the third dimension is positive and its amplitude exceeds the preset temperature rise rate threshold, the exhaust backflow prevention control module determines that the system is in an overload state. This state indicates that the centrifugal fan drive module can no longer maintain the target operating frequency, the motor is in a continuous overcurrent state, and the heat accumulation rate exceeds the safety margin. The exhaust backflow prevention control module immediately sends an overload protection signal to the frequency converter control module. Based on this signal, the frequency converter control module cuts off the output of the frequency converter drive signal, the centrifugal fan stops running, and the exhaust backflow prevention control module simultaneously generates a shutdown command to close the exhaust channel.
[0027] When the first dimension of the three-dimensional state feature vector is negative and its amplitude continues to increase (i.e., negative current deviation), the fluctuation amplitude of the second dimension exceeds the response band width, and the real-time temperature of the third dimension shows a decreasing trend with a negative temperature gradient, the exhaust backflow prevention control module determines that the system is in an impeller unloaded state or a transmission breakage state. This state indicates that the mechanical connection between the centrifugal fan impeller and the motor shaft has failed or the impeller itself has detached. Although the centrifugal fan motor still operates at the target frequency, there is no effective exhaust volume output. The exhaust backflow prevention control module sends a mechanical fault signal to the frequency converter control module. Based on this signal, the frequency converter control module stops the frequency converter drive output, and the exhaust backflow prevention control module generates a shutdown command to close the exhaust channel.
[0028] After receiving the multi-dimensional state feature vector sent by the centrifugal fan drive module, the exhaust backflow prevention control module executes the opening and closing control of the exhaust channel based on multi-dimensional comprehensive judgment. The exhaust backflow prevention control module internally includes shutdown judgment logic, which is based on cross-validation of three dimensions: current, frequency, and temperature. When the operating current is within the rated operating range, the operating frequency is consistent with the target frequency, and the temperature gradient is normal, the exhaust backflow prevention control module determines that the system is in normal operating condition, and the exhaust duct remains open.
[0029] When the operating current decreases but has not yet reached the shutdown threshold, the operating frequency has dropped to zero, and the temperature shows a downward trend, the exhaust backflow prevention control module determines that the centrifugal fan is in the process of decelerating and stopping. At this time, the exhaust backflow prevention control module estimates the time required for the centrifugal fan to completely stop based on the rate of current decrease and the rate of frequency decay. Within the estimated time, the exhaust duct remains open to discharge residual hot air, and a preparatory closing signal is sent to the damper actuator before the estimated time ends, putting the damper actuator into a standby state. Once the centrifugal fan's driving torque has completely disappeared, the closing action is executed immediately. This estimated closing mechanism upgrades the damper closing action from a passive response after shutdown to an active prediction before shutdown, eliminating the response delay window between shutdown and closing.
[0030] When the operating current is below the shutdown threshold, the operating frequency is zero, and the temperature has dropped to the ambient temperature, the exhaust backflow prevention control module directly determines that the centrifugal fan is in a completely stopped state, immediately generates a shutdown command and sends it to the damper actuator to close the exhaust channel.
[0031] When the operating current fluctuates abnormally (below a certain percentage of the rated current but not to zero), the operating frequency is displayed as zero, and the temperature continues to rise, the exhaust backflow prevention control module determines that the centrifugal fan drive module has a stall fault. At this time, after receiving the fault signal, the frequency converter control module immediately cuts off the output of the frequency converter drive signal. At the same time, the exhaust backflow prevention control module forcibly generates a shutdown command to close the exhaust channel to prevent sand and dust from entering under fault conditions.
[0032] When the relationship between operating current and operating frequency deviates from the inherent characteristic curve of the centrifugal fan (i.e., the current is too high but the frequency is too low), the exhaust backflow prevention control module determines that there is mechanical blockage in the exhaust channel or abnormal load on the centrifugal fan impeller. It then sends a load abnormality signal to the frequency converter control module. Based on this signal, the frequency converter control module adjusts the effective gain of the pressure difference-frequency mapping relationship and appropriately reduces the frequency response amplitude in subsequent adjustment cycles to prevent the centrifugal fan from overloading under abnormal load.
[0033] The exhaust backflow prevention control module continuously receives multi-dimensional state feature vectors throughout the entire adjustment process. Its internal state machine continuously operates based on a three-dimensional state space of current-frequency-temperature. The position of the current state point in the three-dimensional state space determines the control strategy of the exhaust channel. Based on the above-mentioned multi-dimensional comprehensive discrimination logic, the exhaust backflow prevention control module dynamically switches the working state of the exhaust channel. The working states include at least the normal operation state, the deceleration prediction state, the complete shutdown state, and the fault state.
[0034] The state machine defines multiple discrete states, each state corresponding to a control strategy for the exhaust channel. The state machine drives the state to transition between multiple discrete states based on the position of the current state point in the three-dimensional state space and the motion trajectory of the state point.
[0035] The exhaust backflow prevention control module has a pre-set three-dimensional state space. The three coordinate axes of this three-dimensional state space are the current deviation axis, the frequency response deviation rate axis, and the temperature gradient axis. The three-dimensional state feature vector received at each moment uniquely corresponds to a state point in the three-dimensional state space. The spatial coordinates of this state point are jointly determined by the current deviation and direction, the frequency response deviation rate and direction, and the temperature gradient and direction at the current moment.
[0036] The exhaust backflow prevention control module performs a difference calculation between the spatial coordinates of the current state point and the spatial coordinates of historical state points within each control cycle to obtain the motion trajectory of the state point in the three-dimensional state space. The current position of the state point determines the current control strategy, while the direction and speed of the state point's motion trajectory determine the state transition direction and timing of the state machine. Specifically, the velocity vector of the state point in the three-dimensional state space is obtained by dividing the difference in the coordinates of the state point within adjacent control cycles by the control cycle time. The direction of this velocity vector represents the deterioration or improvement trend of the system state, and the magnitude of the velocity vector represents the degree of drastic change in the system state.
[0037] The pre-set state machine within the exhaust backflow prevention control module includes at least the following discrete states: normal operation state, abnormal load state, deceleration prediction state, complete shutdown state, and fault state. Each discrete state corresponds to one or more specific regions in the three-dimensional state space.
[0038] The state space region corresponding to normal operation is as follows: the current deviation is within ±15% of the rated current, the absolute value of the frequency response deviation rate is less than 5% of the target frequency, and the real-time temperature is below the temperature warning threshold with a negative or near-zero temperature gradient. When the state point is within this region, the state machine remains in normal operation, and the exhaust duct remains open.
[0039] The state space region corresponding to the abnormal load state is as follows: the positive deviation of the current is 15% to 40% of the rated current, the frequency response deviation rate is negative and the absolute value is between 5% and 15% of the target frequency, and the real-time temperature is below the temperature warning threshold but the temperature gradient is positive. When the state point is within this region, the state machine switches to the abnormal load state, the exhaust backflow prevention control module sends a load abnormality signal to the frequency converter control module, and the frequency converter control module reduces the target operating frequency output accordingly.
[0040] The state space region corresponding to the deceleration prediction state is as follows: the current deviation is between 5% and 15% of the rated current and the direction is negative; the frequency response deviation rate is negative and the absolute value is between 15% and 30% of the target frequency; and the temperature gradient is negative. At this time, the three dimensions together represent that the centrifugal fan is decelerating but has not yet completely stopped. When the state point falls into this region, the state machine switches to the deceleration prediction state. The exhaust anti-backflow control module calculates the remaining time for the centrifugal fan to completely stop based on the movement speed of the state point along the current axis and frequency axis. Within the calculated remaining time, it outputs a pre-closing signal to the damper actuator, causing the damper actuator to enter the standby state.
[0041] The state space corresponding to the complete shutdown state is as follows: the current deviation is 0% to 5% of the rated current and the direction is negative (i.e., the current approaches zero); the frequency response deviation rate is negative and the absolute value is greater than 95% of the target frequency; and the temperature gradient approaches zero. These three dimensions together characterize that the centrifugal fan has completely stopped operating. The state machine switches to the complete shutdown state, and the exhaust anti-backflow control module immediately generates a shutdown command and sends it to the damper actuator to close the exhaust channel.
[0042] The state space region corresponding to the fault state includes at least the following sub-regions: The first sub-region is characterized by a negative current deviation with an amplitude continuously increasing to below -50% of the rated current, a frequency response deviation rate fluctuation exceeding 20% of the target frequency and alternating between positive and negative values, and a negative temperature gradient; these three characteristics collectively indicate impeller unloading or transmission breakage. The second sub-region is characterized by a positive current deviation exceeding 40% of the rated current, a negative frequency response deviation rate with an absolute value greater than 15% of the target frequency, and a positive temperature gradient with an amplitude exceeding the preset temperature rise rate threshold; these three characteristics collectively indicate overload and stall. When the state point falls into any of the above sub-regions, the state machine switches to the fault state, the exhaust backflow prevention control module forcibly triggers the exhaust duct to close, and sends a cut-off signal to the frequency converter control module.
[0043] The state transition logic of a state machine includes dual constraints: boundary crossing conditions and time accumulation conditions.
[0044] The boundary crossing condition is that the state machine triggers a state transition when a state point continuously crosses the boundary plane between two state regions in any direction in the three-dimensional state space. The boundary plane in the three-dimensional state space is either a plane perpendicular to a certain coordinate axis or a surface defined by two coordinate axes. The moment the state point crosses the boundary plane is the trigger moment for the state transition. For example, when a state point crosses the ±15% boundary of the normal operating region along the current axis to the 15% to 40% region of the load abnormality region, the transition from the normal operating state to the load abnormality state is triggered.
[0045] The time accumulation condition is as follows: the state machine only confirms the state transition and executes the corresponding control strategy switch after the state point has continuously resided within the target state region for a preset confirmation time threshold. The introduction of the time accumulation condition eliminates misjudgments caused by brief boundary crossings of state points due to instantaneous disturbances. The preset confirmation time threshold is negatively correlated with the depth of the boundary crossing: the greater the boundary crossing depth, the shorter the confirmation time threshold; the smaller the boundary crossing depth, the longer the confirmation time threshold. Specifically, the exhaust backflow prevention control module starts a timer after detecting that a state point has crossed the boundary plane, while simultaneously monitoring the position fluctuation range of the state point within the crossed state region. If the state point returns to the original state region during the timing period, the timer is reset and monitoring resumes; if the state point remains within the target state region until the timing reaches the confirmation time threshold, the state machine executes the final state transition.
[0046] The exhaust backflow prevention control module performs short-term extrapolation prediction of the motion trajectory of state points based on the current moment and the coordinate sequence of state points within several historical control cycles. Specifically, the module performs linear fitting on the coordinates of state points from the most recent N control cycles to obtain a motion trend line of the state points in the three-dimensional state space. This trend line is then extended outward for a preset time length to obtain the predicted position of the state points in the future. If the predicted position falls within a target state region, the module pre-executes the control strategy corresponding to that target state region before the state point actually reaches its boundary. The lead time of the advance control is related to the confidence level of the predicted position: the smaller the fitting residual, the higher the consistency of the trend line direction, and the earlier the advance control is initiated; the larger the fitting residual, the later the advance control is initiated, or it may be delayed until the state point actually crosses the boundary before execution.
[0047] In the three-dimensional state space, transition zones are established between adjacent state regions. The width of the transition zone is the spatial range covered by a preset percentage extension on both sides of the boundary of each state region. When a state point is located within the transition zone, its spatial coordinates cannot be uniquely mapped to a single state region. The exhaust backflow prevention control module executes fuzzy decision logic for state points within the transition zone: it calculates the weighted distances from the state point to the core points of the two adjacent state regions, with the weighting coefficients preset according to the physical importance of each dimension; it selects the state region with the smaller weighted distance as the current state point's affiliation and executes the corresponding control strategy for that state region. Simultaneously, the dwell time of the state point within the transition zone serves as an auxiliary decision variable. The longer the dwell time, the higher the probability of the state point shifting towards the side with the larger weighted distance. If the dwell time exceeds a preset transition zone dwell threshold, the exhaust backflow prevention control module forcibly assigns the state point to a state region with a higher safety level and executes a more conservative control strategy.
[0048] The aforementioned differential pressure detection module, frequency converter control module, centrifugal fan drive module, and exhaust backflow prevention control module constitute a complete closed-loop control system: the differential pressure detection module provides both differential pressure amplitude information and differential pressure change trend information; the frequency converter control module makes main channel frequency decisions based on the deviation and performs feedforward correction based on the rate of change; the centrifugal fan drive module feeds back the operating status to the exhaust backflow prevention control module in the form of a multi-dimensional feature vector; and the exhaust backflow prevention control module performs comprehensive discrimination and multi-state switching control based on the multi-dimensional state space.
[0049] As a further improvement to the module of the present invention, an air intake compensation module is also included.
[0050] An air intake compensation module is installed within the air intake duct of the skid-mounted building to monitor the real-time air intake status and send an air intake compensation signal to the frequency converter control module. The air intake compensation module includes at least a wind speed detection unit and an air intake calculation unit. The wind speed detection unit is positioned on the cross-section of the air intake duct in a multi-point array to detect the real-time wind speed values at multiple detection points within the duct. The air intake calculation unit receives the real-time wind speed values from each detection point, performs area-weighted integration on the multi-point wind speed values, and calculates the real-time effective air intake volume of the air intake duct. The air intake calculation unit compares the real-time effective air intake volume with a preset lower limit threshold. The lower limit threshold is the minimum air intake volume required to maintain heat dissipation during normal operation of the frequency converter equipment in the skid-mounted building; this threshold is determined by the total heat generation of the frequency converter equipment in the skid-mounted building, the allowable temperature rise, and the specific heat capacity of the air.
[0051] When the real-time effective air intake volume is higher than the lower limit threshold, the air intake volume compensation module determines that the air intake volume is sufficient and does not output a compensation signal. When the real-time effective air intake volume is lower than the lower limit threshold, the air intake volume compensation module determines that there is an abnormal increase in air intake resistance in the air intake channel. This abnormality is usually caused by factors such as dust accumulation on the dust filter, freezing of the air intake louvers, or changes in external wind pressure. The air intake volume compensation module generates an air intake volume compensation signal and sends it to the frequency converter control module. The air intake volume compensation signal includes the deviation between the real-time air intake volume and the lower limit threshold, as well as the direction of the deviation.
[0052] After receiving the intake air volume compensation signal, the frequency converter control module incorporates the intake air volume deviation as a feedforward compensation term into the differential pressure-frequency mapping decision process. Specifically, after calculating the basic target frequency using differential pressure-frequency mapping, the frequency converter control module calculates the frequency compensation amount based on the intake air volume deviation. The direction of the frequency compensation amount is the same as the direction of the intake air volume deviation. When the intake air volume is below a threshold, the compensation amount is negative, meaning the centrifugal fan speed is reduced to decrease the exhaust air volume, allowing the intake and exhaust air volumes to rebalance under the new conditions. The amplitude of the frequency compensation amount is non-linearly positively correlated with the intake air volume deviation; the larger the intake air volume deviation, the larger the increase in the amplitude of the frequency compensation amount. Its mapping curve is pre-calibrated based on the resistance characteristics of the intake channel. The frequency converter control module superimposes the basic target frequency and the frequency compensation amount to generate the final target operating frequency.
[0053] The variable frequency control module also uses the intake air volume deviation as an online correction factor for the pressure difference-frequency mapping relationship, and dynamically adjusts the slope of the mapping relationship: when the intake air volume deviation is positive and continues to accumulate, the mapping relationship curve shifts downward as a whole, and the target frequency corresponding to the same pressure difference deviation decreases by a larger margin, so that the system can maintain pressure balance with a lower exhaust volume under the condition of obstructed air intake.
[0054] As a further improvement to the module of the present invention, an internal circulation control module is also included.
[0055] The internal circulation control module is signal-connected to the differential pressure detection module and the centrifugal fan drive module, and is used to control the opening and closing of the internal circulation duct located inside the skid-mounted house. Both the air inlet and outlet of the internal circulation duct are located inside the skid-mounted house. An air damper actuator is installed inside the internal circulation duct, which is driven by the control signal from the internal circulation control module. When the internal circulation duct is open, it allows the air inside the skid-mounted house to circulate along the internal circulation duct; when the internal circulation duct is closed, it cuts off the internal circulation path.
[0056] The internal circulation control module receives real-time differential pressure data from the differential pressure detection module and real-time operating parameters of the centrifugal fan from the centrifugal fan drive module, and executes two-dimensional judgment logic. The two dimensions of the two-dimensional judgment logic are the differential pressure status dimension and the centrifugal fan operating status dimension.
[0057] In terms of differential pressure status, the internal circulation control module has a built-in differential pressure safety range. The upper and lower limits of this safety range are jointly determined by the sealing performance of the skid-mounted house and the amplitude of wind pressure fluctuations in the external environment. When the absolute value of the real-time differential pressure data exceeds the upper limit of the differential pressure safety range, the differential pressure status dimension outputs an activation signal. In terms of centrifugal fan operating status, the internal circulation control module receives the real-time operating frequency and real-time operating current of the centrifugal fan. When the operating frequency is lower than a preset low-frequency threshold and the operating current is lower than a preset no-load current threshold, the centrifugal fan operating status dimension outputs an activation signal.
[0058] When both of the above dimensions simultaneously output activation signals, the internal circulation control module determines the current operating condition as follows: the external environment is not suitable for introducing fresh air and there is no active exhaust power in the skid-mounted room. If all vents are completely closed at this time, the air inside the skid-mounted room will be stagnant, and the heat generated by the inverter equipment will accumulate locally, forming a heat island effect. The internal circulation control module sends an opening command to the damper actuator located on the internal circulation duct, opening the internal circulation duct and allowing the air inside the skid-mounted room to circulate. This carries the heat near the inverter equipment to a uniform distribution throughout the entire skid-mounted room space, preventing excessively high local temperatures.
[0059] The internal circulation control module also receives the current target operating frequency from the frequency converter control module. When the target operating frequency is lower than the preset low-frequency threshold, the centrifugal fan outputs an activation signal in the operating status dimension. The internal circulation control module further incorporates the changing trend of the differential pressure signal into its judgment: when the differential pressure signal continues to accumulate in the same direction and the rate of change shows a decreasing trend, it indicates that the external environment has become stable, and the internal circulation control module keeps the internal circulation duct open; when the rate of change of the differential pressure signal shows an increasing trend, it indicates that the external environment is deteriorating, and the internal circulation control module continues to keep the internal circulation duct open and increases the speed of the internal circulation fan in the internal circulation duct to accelerate internal air circulation.
[0060] When the activation signal of any dimension is removed, the internal circulation control module executes a delayed shutdown logic based on the state of the other dimension: if the differential pressure state dimension is still active while the centrifugal fan operating state dimension has been deactivated, the internal circulation control module maintains the internal circulation duct open and starts a timer. The internal circulation duct is closed only after the timer reaches the preset safety delay time; if the centrifugal fan operating state dimension is still active while the differential pressure state dimension has been deactivated, the internal circulation control module immediately closes the internal circulation duct. As a further improvement to the module of the present invention, a fault self-test module is also included.
[0061] The fault self-test module is signal-connected to the centrifugal fan drive module to acquire multi-dimensional operating parameters of the centrifugal fan in real time. These parameters include at least operating current, operating voltage, operating frequency, operating temperature, and vibration amplitude. The fault self-test module has a pre-set multi-level threshold system for each parameter, including at least alarm thresholds and protection thresholds. The module performs threshold comparisons for each parameter and simultaneously executes cross-validation logic between parameters.
[0062] The fault self-test module compares the real-time operating current with the current alarm threshold and the current protection threshold, the real-time operating voltage with the voltage alarm threshold and the voltage protection threshold, the real-time operating temperature with the temperature alarm threshold and the temperature protection threshold, and the real-time operating frequency with the target operating frequency sent by the frequency converter control module to calculate the frequency tracking deviation.
[0063] The fault self-test module executes cross-validation logic between parameters, which is based on the physical coupling relationship between the parameters: under normal operating conditions, the operating current changes linearly with the operating frequency, the operating temperature increases with the integral of the product of the operating current and the operating time, and the vibration amplitude is positively correlated with the square of the operating frequency. When the fault self-test module detects an abnormality in a certain parameter, it first verifies whether other coupled parameters are synchronously abnormal.
[0064] Specifically, if the operating current exceeds the current alarm threshold but the operating temperature does not rise synchronously and the vibration amplitude does not increase abnormally, the fault self-test module determines it as a momentary current spike and executes the delay debouncing logic: it continues to monitor within a preset delay window, and if the current falls back below the alarm threshold within the delay window, the fault is not triggered. If the operating current exceeds the current protection threshold and the operating temperature rises synchronously and the vibration amplitude increases synchronously, the abnormal directions of the three coupling parameters are consistent, and the fault self-test module determines it as a mechanical overload fault.
[0065] If the operating current is lower than the no-load current threshold but the operating frequency is the same as the target frequency, and the vibration amplitude exhibits non-periodic random fluctuations, then the abnormal directions of the three coupling parameters are inconsistent. The fault self-check module determines this as an impeller unloading or transmission breakage fault and outputs a mechanical fault signal. If the operating temperature exceeds the temperature protection threshold but the operating current is within the normal range and the operating frequency is the same as the target frequency, then this is determined to be a heat dissipation system fault, and a heat dissipation fault signal is output.
[0066] After comprehensively determining that a fault has occurred, the fault self-diagnosis module executes the following parallel processing logic: First, a fault alarm signal is output, which includes a fault type code and the time of fault occurrence. This signal is sent to the remote monitoring terminal via a data recording and remote communication module. Second, the exhaust backflow prevention control module is forcibly triggered to close the exhaust duct. Third, a fault protection request is sent to the frequency converter control module. The frequency converter control module executes the corresponding protection strategy based on the fault type code: if it is a mechanical overload fault or a heat dissipation fault, the frequency converter control module gradually reduces the output frequency of the frequency converter drive signal in predetermined steps until the centrifugal fan operates at a safe frequency or stops completely; if it is an impeller unloading fault, the frequency converter control module immediately cuts off the frequency converter drive signal output.
[0067] The fault self-test module also includes fault locking logic: after a fault is triggered, even if the operating parameters recover to the threshold range in subsequent sampling cycles, the fault locking logic keeps the fault state and the corresponding protection action effective until an external manual reset signal is received before the lock is released.
[0068] As a further improvement to the module of the present invention, the frequency conversion control module has a built-in differential pressure-frequency mapping table, which is used to query the corresponding target operating frequency according to the real-time received differential pressure signal, and use the target operating frequency as the output reference of the frequency conversion drive signal.
[0069] As a further improvement to the module of the present invention, a fault self-checking module is also included, which is used to monitor the operating status of the centrifugal fan drive module in real time, and when a fault is detected in the centrifugal fan drive module, output a fault alarm signal and forcibly trigger the exhaust anti-backflow control module to perform the action of closing the exhaust channel.
[0070] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A skid-mounted inverter control ventilation module that prevents sand and dust intrusion and avoids internal negative pressure, characterized in that, include: The differential pressure detection module is installed inside the skid-mounted house to detect the air pressure difference between the inside of the skid-mounted house and the external environment in real time and output the corresponding differential pressure signal. The variable frequency control module is connected to the differential pressure detection module and is used to receive the differential pressure signal and generate a variable frequency drive signal based on the differential pressure signal. The variable frequency drive signal is used to adjust the operating frequency of the exhaust equipment. The centrifugal fan drive module is connected to the frequency converter control module for receiving the frequency converter drive signal and driving the centrifugal fan to operate at a corresponding speed according to the frequency converter drive signal, so as to adjust the exhaust volume of the skid-mounted house to the outside. The exhaust backflow prevention control module is linked with the centrifugal fan drive module and is used to control the closure of the exhaust duct when the centrifugal fan stops running, so as to prevent external sand and debris from flowing back into the skid-mounted house through the exhaust duct.
2. The skid-mounted inverter control ventilation module for preventing sand and dust intrusion and avoiding internal negative pressure as described in claim 1, characterized in that, It also includes an air intake compensation module, which is installed in the air intake channel of the skid-mounted house to monitor the real-time air intake status of the air intake channel and send an air intake compensation signal to the frequency converter control module when the real-time air intake is lower than a preset threshold. After receiving the intake air volume compensation signal, the frequency conversion control module adjusts the frequency conversion drive signal according to the intake air volume compensation signal to regulate the exhaust air volume, so that the intake air volume and the exhaust air volume are kept in balance.
3. The skid-mounted inverter control ventilation module for preventing sand and dust intrusion and avoiding internal negative pressure as described in claim 1, characterized in that, It also includes an internal circulation control module, which is connected to the centrifugal fan drive module and the differential pressure detection module. When the differential pressure signal indicates that the pressure difference between the inside and outside of the skid-mounted house exceeds the preset safety range and the centrifugal fan is at low speed or stopped, the internal circulation duct set inside the skid-mounted house is opened to allow the air inside the skid-mounted house to circulate internally.
4. The skid-mounted inverter control ventilation module for preventing sand and dust intrusion and avoiding internal negative pressure as described in claim 1, characterized in that, The frequency conversion control module has a built-in differential pressure-frequency mapping table, which is used to query the corresponding target operating frequency based on the real-time received differential pressure signal, and use the target operating frequency as the output reference of the frequency conversion drive signal.
5. The skid-mounted frequency converter control ventilation module for preventing sand and dust intrusion and avoiding internal negative pressure as described in claim 1, characterized in that, It also includes a fault self-diagnosis module, which is connected to the centrifugal fan drive module by signal. It is used to obtain the operating status of the centrifugal fan drive module in real time, and when a fault is detected in the centrifugal fan drive module, it outputs a fault alarm signal and forcibly triggers the exhaust anti-backflow control module to perform the action of closing the exhaust channel.
6. The skid-mounted frequency converter control ventilation module for preventing sand and dust intrusion and avoiding internal negative pressure as described in claim 1, characterized in that, The differential pressure detection module continuously collects the air pressure value inside the skid and the external atmospheric pressure value at a fixed sampling period, obtains the real-time differential pressure data by subtracting the two, and calculates the differential pressure change rate based on the differential pressure data at adjacent sampling times. The real-time differential pressure data and the differential pressure change rate are output together to the frequency conversion control module. The frequency conversion control module uses the differential pressure data as the main control variable and the differential pressure change rate as the feedforward correction variable to perform differential pressure closed-loop regulation: when the real-time differential pressure data deviates from the preset target differential pressure range, the frequency conversion control module extracts the deviation and inputs it into the main mapping channel to obtain the basic target frequency, and at the same time inputs the differential pressure change rate into the feedforward correction channel to obtain the frequency correction amount, and combines the basic target frequency and the frequency correction amount to generate the final target operating frequency; The direction of the frequency correction is opposite to the direction of the rate of change of pressure, and the amplitude is positively correlated with the magnitude of the rate of change of pressure.
7. The skid-mounted frequency converter control ventilation module for preventing sand and dust intrusion and avoiding internal negative pressure as described in claim 4, characterized in that, The pressure difference-frequency mapping table takes pressure difference data as input and the target operating frequency as output. The method for obtaining the pressure difference-frequency mapping relationship is as follows: Under the actual operating conditions of the skid-mounted house, the centrifugal fan is set to operate at multiple different frequency points. After the pressure difference between the inside and outside of the skid-mounted house reaches a steady state at each frequency point, the corresponding steady-state pressure difference value is recorded. After forming frequency-pressure difference data points, a continuous mapping relationship is generated by interpolation fitting.
8. The skid-mounted frequency converter control ventilation module for preventing sand and dust intrusion and avoiding internal negative pressure as described in claim 1, characterized in that, While driving the centrifugal fan, the centrifugal fan drive module continuously monitors the real-time operating parameters of the centrifugal fan, including at least the operating current, operating frequency, and operating temperature. The centrifugal fan drive module compares the operating current with the rated operating current to obtain the current deviation and direction, compares the operating frequency with the target operating frequency sent by the frequency conversion control module to obtain the frequency response deviation rate, performs time series analysis on the operating temperature to obtain the temperature gradient, integrates the current deviation and direction, the frequency response deviation rate, and the temperature gradient to generate a three-dimensional state feature vector and sends it to the exhaust backflow prevention control module.
9. The skid-mounted frequency converter control ventilation module for preventing sand and dust intrusion and avoiding internal negative pressure as described in claim 8, characterized in that, The exhaust backflow prevention control module receives the three-dimensional state feature vector and performs the opening and closing control of the exhaust channel based on the position of the three-dimensional state feature vector in the preset three-dimensional state space. The exhaust backflow prevention control module has a pre-installed state machine. The state machine continuously operates based on a three-dimensional state space constructed by the current deviation axis, frequency response deviation rate axis, and temperature gradient axis. The position and trajectory of the current state point in the three-dimensional state space determine the opening of the exhaust channel. The state machine includes at least a normal operation state, a deceleration prediction state, a complete shutdown state, and a fault state. The exhaust backflow prevention control module sends an opening and holding command or a closing command to the damper actuator located in the exhaust channel according to the current state of the state machine.
10. The skid-mounted frequency converter control ventilation module for preventing sand and dust intrusion and avoiding internal negative pressure as described in claim 3, characterized in that, The internal circulation control module receives real-time differential pressure data sent by the differential pressure detection module and real-time operating parameters of the centrifugal fan sent by the centrifugal fan drive module, and performs a two-dimensional judgment: When the differential pressure state dimension and the centrifugal fan operating state dimension simultaneously meet the activation conditions, an opening command is sent to the damper actuator set on the internal circulation duct to open the internal circulation duct and allow the air inside the skid-mounted house to circulate. The activation condition for the differential pressure state dimension is that the absolute value of the real-time differential pressure data is greater than the preset upper limit of the differential pressure safety range, and the activation condition for the centrifugal fan operating state dimension is that the operating frequency is lower than the preset low frequency threshold and the operating current is lower than the preset no-load current threshold. When the activation signal is removed in any dimension, the inner loop control module executes delayed shutdown logic.