Water quality intelligent monitoring and distributed control method and system, and storage medium

Abstract

This invention relates to the field of water quality monitoring and control technology, and discloses a method, system, and storage medium for intelligent water quality monitoring and distributed control. The method collects water quality parameters through an integrated control unit. During system initialization, multi-band calibration signals are applied to establish a frequency-impedance mapping table. During operation, equivalent impedance parameters are calculated from the mapping table based on the inverter's target frequency, and impedance compensation correction is performed on the current sample values. Dynamic feature template parameters are then obtained from the frequency-current feature mapping table for matching calculations. The actuator status is determined based on the matching degree, and control commands are output. This invention solves the problem of insufficient accuracy in determining the actuator status under combined operating conditions of long-distance cables and frequency converter drives.

Description

Technical Field

[0001] This invention relates to the field of water quality monitoring and control technology, and more specifically, to a method, system, and storage medium for intelligent water quality monitoring and distributed control. Background Technology

[0002] In scenarios such as urban water supply, sewage treatment, and rural decentralized water stations, water quality monitoring stations are geographically dispersed and require centralized monitoring. Each station needs to monitor multiple water quality parameters such as temperature, turbidity, pH, residual chlorine, total chlorine, and color, and control actuators such as sampling pumps and dosing pumps. Existing solutions employ a four-layer discrete architecture of dedicated transmitters, PLC controllers, touch screens, and communication modules for water quality monitoring and control.

[0003] The existing technical solution has the following drawbacks: In actual operation, the actuators at some sites are far from the control unit, with cable lengths ranging from tens to hundreds of meters, and frequency converters are used for precise flow regulation. Long-distance cables introduce line impedance; cable resistance causes a drop in the actual voltage at the actuator end, and cable inductance causes current waveform delay and distortion, resulting in the sampled current characteristics deviating from the standard template. Under frequency conversion drive, the normal operating current varies with the operating frequency; the pre-stored single characteristic template only corresponds to a specific frequency, and normal operation at other frequencies is misjudged as a fault. When long-distance cables are superimposed with frequency conversion drive, the influence of line impedance on current at different frequencies varies, and a single impedance compensation parameter cannot cover the entire frequency band, causing technical problems such as inaccurate actuator status determination under complex operating conditions. Summary of the Invention

[0004] This invention provides a method, system, and storage medium for intelligent water quality monitoring and distributed control, solving the technical problems in related technologies where the actuator's impedance characteristics change under frequency conversion control, leading to inaccurate fault diagnosis and the inability to achieve accurate status monitoring at dynamic frequencies.

[0005] This invention provides a method for intelligent water quality monitoring and distributed control, comprising: Water quality monitoring data is collected from various sensors through an integrated control unit, and the data is processed by a signal conditioning circuit to obtain digital measurement values ​​of various water quality parameters. To calibrate the multi-band impedance, a multi-band calibration signal sequence is applied sequentially to the actuator circuit. The response waveforms of each frequency band are collected. The equivalent impedance parameters corresponding to each frequency band are calculated based on the excitation voltage amplitude, response current amplitude, and phase difference of each frequency band, and a frequency-impedance mapping table is generated. Compensate dynamic impedance, obtain the target frequency setting value sent to the frequency converter, calculate the equivalent impedance parameter corresponding to the current frequency by interpolation from the frequency-impedance mapping table based on the target frequency setting value, perform impedance compensation correction operation on the current sample value, and obtain the compensated current characteristic quantity. Matching dynamic features involves interpolating the corresponding dynamic feature template parameters from the frequency-current feature mapping table based on the target frequency setting value, and then performing a matching operation between the compensated current feature quantity and the dynamic feature template parameters to obtain the matching degree result. The system identifies faults and outputs control commands. When the matching degree is lower than the dynamic threshold, the system marks the fault state and locks the control output. When the actuator is in normal condition, the system drives the actuator to move according to the control program.

[0006] Furthermore, the multi-band calibration signal sequence includes calibration signals corresponding to multiple discrete frequency points within the range from the lowest operating frequency to the highest operating frequency. The lowest and highest operating frequencies are determined by the frequency adjustment range of the inverter. The duration of the calibration signal at each frequency point is not less than 3 to 5 times the corresponding frequency period.

[0007] Furthermore, the calculation of the equivalent impedance parameter includes: extracting the amplitude of the fundamental component by performing a Fourier transform on the acquired current response waveform as the amplitude of the response current; calculating the phase angle difference between the excitation voltage and the fundamental component of the response current as the phase difference; determining the impedance amplitude based on the ratio of the excitation voltage amplitude to the response current amplitude; determining the equivalent resistance component based on the product of the impedance amplitude and the cosine of the phase angle; and determining the equivalent reactance component based on the product of the impedance amplitude and the sine of the phase angle.

[0008] Furthermore, the impedance compensation correction operation is as follows: multiply the real-time current waveform by the ratio of the reference impedance value to the current equivalent impedance parameter to obtain the compensated current waveform; The reference impedance value is the equivalent impedance parameter corresponding to the reference operating frequency, and the reference operating frequency is the rated operating frequency of the actuator; the current characteristic quantities extracted from the compensated current waveform include at least one of current amplitude, current phase, and current harmonic content. The frequency distribution density in the multi-band calibration signal sequence is adaptively adjusted according to the impedance change gradient, which is obtained by calculating the ratio of the impedance difference to the frequency difference between adjacent frequency points. When the impedance change gradient exceeds a preset gradient threshold, additional frequency points are inserted in the interval corresponding to the adjacent frequency points for supplementary calibration.

[0009] Furthermore, the establishment of the frequency-current feature mapping table includes: driving the actuator to perform a complete action process of starting, steady-state operation and stopping at each calibration frequency point; collecting the current waveform at each calibration frequency point and extracting the current feature quantity after performing impedance compensation correction calculation; statistically averaging the current feature quantity collected from multiple normal operations to obtain the current feature template parameter; and associating and storing the current feature template parameter with the corresponding calibration frequency point.

[0010] Furthermore, the matching operation includes: normalizing the compensated current characteristic quantity and the dynamic characteristic template parameter; calculating the Euclidean distance between the normalized current characteristic quantity vector and the normalized dynamic characteristic template parameter vector; and determining the matching degree based on the ratio of the Euclidean distance to the norm of the normalized dynamic characteristic template parameter vector, wherein the matching degree is equal to 1 minus the ratio.

[0011] Furthermore, the fault determination and output control command also includes: setting a threshold for the number of consecutive determinations, and confirming the fault state when the matching degree of a preset number of consecutive determinations is lower than the dynamic threshold; the dynamic threshold is adaptively adjusted according to the operating frequency, and the dynamic threshold is reduced when the operating frequency is in the range of drastic impedance changes, and increased when the operating frequency is in the range of gradual impedance changes.

[0012] Furthermore, it also includes: periodically performing local impedance verification, applying a single-frequency verification signal to the actuator circuit during the actuator's idle period, calculating the deviation between the current impedance value and the corresponding value in the frequency-impedance mapping table, and triggering the frequency-impedance mapping table update or issuing a maintenance prompt when the deviation exceeds a preset threshold; uploading water quality monitoring data, equipment operating status, and alarm information to the cloud platform through the communication module, and pushing alarm messages through at least one of the following methods when an alarm flag is generated: WeChat mini-program, mobile phone text message, email, and on-site audible and visual alarm.

[0013] This invention provides a water quality intelligent monitoring and distribution control system, comprising: The data acquisition module is used to collect water quality monitoring data from various sensors, and after processing by the signal conditioning circuit, obtain the digital measurement values ​​of each water quality parameter. The impedance calibration module is used to sequentially apply a multi-band calibration signal sequence to the actuator circuit, collect the response waveform of each frequency band, calculate the equivalent impedance parameters corresponding to each frequency band, and generate a frequency-impedance mapping table. The impedance compensation module is used to obtain the target frequency setting value sent to the frequency converter, interpolate the equivalent impedance parameter corresponding to the current frequency from the frequency-impedance mapping table according to the target frequency setting value, perform impedance compensation correction operation on the current sample value, and obtain the compensated current characteristic quantity. The feature matching module is used to interpolate and calculate the corresponding dynamic feature template parameters from the frequency-current feature mapping table according to the target frequency setting value, and to perform matching operation between the compensated current feature quantity and the dynamic feature template parameters to obtain the matching degree result. The fault determination and control module is used to mark the fault state and lock the control output when the matching degree is lower than the dynamic threshold, and drive the actuator to act according to the control program when the actuator is in normal state.

[0014] A storage medium for storing computer-readable instructions that, when read, enable the execution of the aforementioned intelligent water quality monitoring and distributed control method.

[0015] The beneficial effects of this invention are as follows: This invention generates a frequency-impedance mapping table through multi-band impedance calibration, enabling the equivalent impedance parameter to be dynamically adjusted according to the actual operating frequency, thus eliminating the differential impedance influence of long-distance cables on currents of different frequencies. It establishes a correspondence between operating frequency and normal current characteristics through a frequency-current characteristic mapping table, allowing the current characteristic template parameter to change synchronously with the actual operating frequency, preventing normal operation from being misjudged as a fault under frequency conversion drive. Through the synergistic application of dynamic impedance compensation and dynamic characteristic matching, it solves the technical problem of insufficient accuracy in actuator status determination under combined operating conditions of long-distance cables and frequency conversion drives, achieving the technical effect of improving the accuracy of actuator response status determination under combined operating conditions. Attached Figure Description

[0016] Figure 1 This is a flowchart of the intelligent water quality monitoring and distribution control method of the present invention; Figure 2 This is a diagram showing the results of the digital conversion of water quality monitoring data according to the present invention; Figure 3 This is the multi-band impedance calibration curve diagram of the present invention; Figure 4 This is a graph showing the impedance phase angle as a function of frequency in this invention. Figure 5 This is a comparison diagram of the current before and after dynamic impedance compensation according to the present invention; Figure 6 This is a comparison diagram of the current characteristic quantity and dynamic template matching of the present invention; Figure 7 This is a diagram showing the cable length and rated power distribution of the three water pumps of this invention. Detailed Implementation

[0017] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0018] At least one embodiment of the present invention discloses a method for intelligent water quality monitoring and distributed control, such as... Figure 1 As shown, it includes the following steps: Step 1: Collect water quality monitoring data and obtain digital measurement values ​​of various water quality parameters.

[0019] Water quality monitoring data is collected from various sensors via an integrated control unit. This integrated control unit physically integrates signal conditioning circuitry, intelligent computing control module, touchscreen display, and communication module into a single hardware device. The signal conditioning circuit includes dedicated signal conditioning channels for six water quality parameters: temperature, turbidity, pH, residual chlorine, total chlorine, and color. The integrated control unit collects raw signals from each sensor via an RS485 bus, and after filtering, amplification, and analog-to-digital conversion by the signal conditioning circuit, obtains and stores the digital measurement values ​​of each water quality parameter.

[0020] It should be noted that the sensor interface described above is a switchable, universal interface. When it is necessary to change the sensor type, the input impedance matching parameters of the signal conditioning circuit can be adjusted via hardware jumpers, and the corresponding software signal processing parameters can be set via the touchscreen configuration interface. This allows the same physical interface to connect to different types of sensors such as pH sensors, ORP sensors, residual chlorine sensors, and total chlorine sensors.

[0021] Step 2: Calibrate the multi-band impedance and generate a frequency-impedance mapping table.

[0022] During the system initialization phase, the integrated control unit sequentially applies a multi-band calibration signal sequence to each actuator loop, collects the response waveforms of each frequency band, calculates the equivalent impedance parameters corresponding to each frequency band, and generates a frequency-impedance mapping table.

[0023] Specifically, the integrated control unit calibrates the multi-band impedance according to the following sub-steps: Step 201: Generate a multi-band calibration signal sequence covering the operating frequency range. The multi-band calibration signal sequence contains calibration signals corresponding to multiple discrete frequency points within the range from the lowest operating frequency to the highest operating frequency.

[0024] Furthermore, the minimum and maximum operating frequencies are determined by the frequency adjustment range of the frequency converter. For pump-type actuators, the minimum operating frequency is usually set to 25Hz to 30Hz to ensure normal operation of the pump body, and the maximum operating frequency is usually set to 50Hz to 60Hz to correspond to the rated frequency of the power grid.

[0025] Step 202: Apply calibration signals corresponding to each frequency point to the actuator circuit in sequence, and the current sampling module synchronously collects the current response waveforms under each frequency band.

[0026] Furthermore, the acquisition of the current response waveform is achieved through the current sampling module built into the integrated control unit. The current sampling module uses a Hall current sensor or a current transformer to convert the AC current signal in the actuator circuit into a voltage signal, which is then digitally acquired by an analog-to-digital converter at a sampling rate of no less than 64 sampling points per cycle, thereby obtaining a discrete data sequence that can accurately reflect the characteristics of the current waveform.

[0027] Step 203: Calculate the equivalent impedance parameters for each frequency band based on the excitation voltage amplitude, response current amplitude, and phase difference. in, For the first The equivalent impedance corresponding to each frequency point The index of the frequency point. This is the equivalent resistance component. For the equivalent reactance component, For the first The excitation voltage amplitude at each frequency point For the first The response current amplitude at each frequency point For the first Phase difference at each frequency point It is the imaginary unit.

[0028] Furthermore, the amplitude of the response current The phase difference is obtained by extracting the amplitude of the fundamental component after performing a Fourier transform on the acquired current response waveform. This represents the phase angle difference between the fundamental component of the excitation voltage and the response current. The amplitude of the excitation voltage... The voltage sampling channel of the integrated control unit synchronously acquires the power supply voltage waveform of the actuator circuit, and the amplitude of the fundamental component is extracted by Fourier transform.

[0029] Furthermore, the equivalent resistance component and equivalent reactance component From the equivalent impedance through complex number operations The equivalent resistance component is obtained by separating the impedance from the phase angle. The equivalent reactance component is equal to the product of the impedance amplitude and the phase angle cosine. The equivalent resistance component reflects the resistance characteristics of the cable and the active power consumption of the actuator. The equivalent reactance component reflects the inductive characteristics of the cable and the reactive power consumption of the actuator.

[0030] Step 204: Associate each frequency point with the corresponding equivalent impedance parameter to generate a frequency-impedance mapping table and store it in the integrated control unit.

[0031] It should be noted that the above multi-band calibration signal sequence can be applied sequentially using single-frequency sinusoidal signals or continuously using swept-frequency signals. When applying single-frequency sinusoidal signals sequentially, the duration of the calibration signal at each frequency point should be no less than 3 to 5 times the corresponding period to obtain the steady-state response waveform.

[0032] Furthermore, to improve the coverage accuracy of the frequency-impedance mapping table, the frequency point distribution density can be adaptively adjusted based on the impedance change gradient. Specifically, the frequency point density is increased in regions where impedance changes drastically with frequency, and decreased in regions where impedance changes gradually with frequency, thereby obtaining a more accurate impedance characteristic curve under limited storage space. The impedance change gradient is obtained by calculating the ratio of the impedance difference to the frequency difference between adjacent frequency points. When the ratio of the impedance difference to the frequency difference exceeds a preset gradient threshold, additional frequency points are inserted in the interval corresponding to the adjacent frequency points for supplementary calibration.

[0033] Step 3: Compensate for dynamic impedance and obtain the current characteristic quantity after compensation.

[0034] During normal operation, the integrated control unit obtains the target frequency setpoint sent to the frequency converter, calculates the equivalent impedance parameter corresponding to the current frequency by interpolation from the frequency-impedance mapping table based on the target frequency setpoint, performs impedance compensation correction calculation on the current sample value, and obtains the compensated current characteristic quantity.

[0035] Specifically, the integrated control unit compensates for dynamic impedance according to the following sub-steps: Step 301: Obtain the currently issued target frequency setting value from the inverter control interface.

[0036] Furthermore, the target frequency setting value is obtained by reading the control signal output from the integrated control unit to the frequency converter. The control signal can be an analog voltage signal or a digital communication command. When analog control is used, the target frequency setting value is calculated by the linear correspondence between voltage value and frequency. When digital control is used, the frequency setting register value of the frequency converter is directly read through RS485 or Modbus communication protocol.

[0037] Step 302: Find two calibration frequency points adjacent to the target frequency setting value in the frequency-impedance mapping table, wherein the two adjacent calibration frequency points are located on both sides of the target frequency setting value.

[0038] Step 303: Calculate the equivalent impedance parameters corresponding to the target frequency setting using a linear interpolation algorithm.

[0039] Step 304: Perform impedance compensation correction calculation on the real-time current waveform acquired by the current sampling module: in, The current waveform after compensation. This is a real-time current waveform. For reference impedance value, The equivalent impedance parameter corresponding to the target frequency setting. It is a time variable.

[0040] Furthermore, the reference impedance value The equivalent impedance parameter corresponding to the reference operating frequency selected during system calibration is used to normalize the current waveforms at different frequencies to a unified impedance reference. The reference operating frequency is usually selected as the rated operating frequency of the actuator. For a water pump actuator powered by a 50Hz mains grid, the reference operating frequency is set to 50Hz, and the corresponding reference impedance value is the equivalent impedance parameter corresponding to the 50Hz frequency point in the frequency-impedance mapping table.

[0041] Furthermore, the physical significance of the impedance compensation correction operation lies in eliminating the distortion effect of cable impedance on the current waveform. When the actuator operates at a non-reference frequency, the cable impedance differs from the impedance at the reference frequency, causing the sampled current waveform to undergo amplitude scaling and phase shift relative to the actual current consumed by the actuator. By multiplying the sampled current by the ratio of the reference impedance value to the current equivalent impedance parameter, it is equivalent to restoring the sampled current from its distorted state under the current impedance condition to its standard state under the reference impedance value condition, thereby achieving comparability of current characteristics at different frequencies.

[0042] Step 305: Extract current characteristic quantities from the compensated current waveform. The current characteristic quantities include at least one of current amplitude, current phase, and current harmonic content.

[0043] Furthermore, the current amplitude is obtained by calculating the effective value of the compensated current waveform, the current phase is obtained by calculating the phase difference between the compensated current waveform and the reference voltage waveform, and the current harmonic content is obtained by extracting the percentage of the amplitude of each harmonic component relative to the fundamental amplitude after performing a fast Fourier transform on the compensated current waveform.

[0044] It should be noted that the above linear interpolation algorithm is suitable for cases where the impedance changes approximately linearly with frequency. When the impedance changes nonlinearly with frequency, spline interpolation or polynomial interpolation methods can be used to improve the calculation accuracy.

[0045] Furthermore, to accommodate impedance drift caused by cable aging or changes in ambient temperature, the integrated control unit can periodically perform local impedance verification. Specifically, during idle periods of the actuator, a single-frequency verification signal is applied to the actuator circuit to calculate the deviation between the current impedance value and the corresponding value in the frequency-impedance mapping table. When the deviation exceeds a preset threshold, the frequency-impedance mapping table is updated or a maintenance prompt is issued.

[0046] Step 4: Match dynamic features and obtain matching results.

[0047] The integrated control unit calculates the corresponding dynamic characteristic template parameters by interpolation from the frequency-current characteristic mapping table based on the target frequency setting value, and performs matching calculations between the current characteristic quantity after impedance compensation correction and the dynamic characteristic template parameters to obtain the matching degree result.

[0048] Specifically, the integrated control unit matches dynamic features according to the following sub-steps: Step 401: Obtain the pre-stored frequency-current feature mapping table. The frequency-current feature mapping table records the current feature template when the actuator is operating normally at each calibrated frequency point.

[0049] Furthermore, the frequency-current characteristic mapping table is established through calibration experiments during the system initialization phase. The specific method is as follows: after completing the impedance calibration in step 2, the actuator is driven to perform a complete action process such as normal start-up, steady-state operation, and stop at each calibration frequency point. The current waveform at each calibration frequency point is collected synchronously. After performing impedance compensation correction calculation on the collected current waveform, the current characteristic quantity is extracted. The extracted current characteristic quantity is stored as the current characteristic template parameter of the calibration frequency point, thereby establishing the mapping relationship between frequency and normal current characteristics.

[0050] Furthermore, the current characteristic template parameters include standard values ​​of current amplitude, current phase, and current harmonic content during normal operation at the calibration frequency point. These standard values ​​are obtained by statistically averaging the current characteristic quantities collected from multiple normal operations to eliminate random errors in a single measurement.

[0051] Step 402: Based on the current target frequency setting, find the adjacent calibration frequency points in the frequency-current feature mapping table, and use a linear interpolation algorithm to calculate the dynamic feature template parameters corresponding to the current target frequency setting.

[0052] Step 403: Normalize the compensated current characteristic quantity and dynamic characteristic template parameter to eliminate the dimensional differences between different characteristic parameters.

[0053] Step 404: Calculate the matching degree between the normalized current characteristic quantity and the dynamic characteristic template parameters: in, For matching degree, This is the normalized vector of current characteristics. This is the normalized dynamic feature template parameter vector. This represents the Euclidean distance.

[0054] Furthermore, the matching degree The range of values ​​is The matching degree is 1 when the current characteristic quantity is completely consistent with the current characteristic template parameter. The greater the difference between the current characteristic quantity and the current characteristic template parameter, the closer the matching degree is to 0. The physical meaning of the matching degree is the degree of similarity between the actual current characteristic after quantitative compensation and the current characteristic template parameter under normal operating conditions. The higher the matching degree, the closer the current response state of the actuator is to the normal operating condition. The lower the matching degree, the more likely the actuator has faults such as jamming, overload, or phase loss.

[0055] It should be noted that the aforementioned frequency-current characteristic mapping table can be obtained through calibration tests during the system initialization phase, or it can be obtained through offline simulation calculations combined with on-site correction. During calibration tests, the actuator is driven to perform normal operations at each calibration frequency point, current waveforms are collected, and current characteristic quantities are extracted as current characteristic template parameters.

[0056] Furthermore, to improve the robustness of the matching operation, the current characteristic template parameters can be represented in interval form. Specifically, each current characteristic template parameter is stored in the form of mean and tolerance. During the matching operation, it is determined whether the compensated current characteristic quantity falls within the corresponding tolerance interval, thereby reducing the impact of sensor noise on the matching result.

[0057] Step 5: Determine the fault and output control commands.

[0058] The integrated control unit performs fault determination based on the matching degree result. When the matching degree is lower than the dynamic threshold, a fault state is marked. When the actuator is in normal condition, the actuator is driven to act according to the control program, and control commands are output.

[0059] Specifically, the integrated control unit determines the fault and outputs control commands according to the following sub-steps: Step 501: Compare the matching degree with a preset dynamic threshold. When the matching degree is greater than or equal to the dynamic threshold, the actuator response is determined to be normal; when the matching degree is less than the dynamic threshold, the actuator response is determined to be abnormal, and a fault state is marked.

[0060] Furthermore, the dynamic threshold is determined based on the balance between the false positive rate and the false negative rate required by the system, and is usually set between 0.7 and 0.85. When it is required to reduce the false positive rate, the dynamic threshold is increased, and when it is required to reduce the false negative rate, the dynamic threshold is decreased.

[0061] Step 502: When the actuator responds normally, the integrated control unit executes the control logic according to the pre-stored control program, performs timing control according to the start and stop time parameters set by the touch screen configuration interface, generates control commands and drives the sampling pump, dosing pump and valve to switch on and off through the output circuit.

[0062] Step 503: When the actuator responds abnormally or the water quality parameters exceed the limit, the integrated control unit locks the control output, prohibits the actuator from operating, and generates an alarm flag.

[0063] It should be noted that the dynamic threshold mentioned above can be set to a fixed value or can be adaptively adjusted according to the operating frequency. When the operating frequency is in a range of drastic impedance changes, the dynamic threshold should be appropriately lowered to improve fault tolerance; when the operating frequency is in a range of gradual impedance changes, the dynamic threshold should be appropriately increased to improve judgment sensitivity.

[0064] Furthermore, to avoid misjudgments caused by transient interference, fault determination can adopt a strategy of only confirming a fault when the matching degree is lower than the dynamic threshold for multiple consecutive times. Specifically, a threshold for the number of consecutive determinations is set, and the fault state is finally confirmed and the control output is locked only when the matching degree is lower than the dynamic threshold for a preset number of consecutive times.

[0065] Furthermore, in order to achieve remote monitoring and multi-channel alarms, the following steps are also included in step 5: the integrated control unit uploads water quality monitoring data, equipment operating status and alarm information to the smart water affairs cloud platform through the built-in 4G or Ethernet communication module; when an alarm tag is generated, an alarm message is pushed to the operation and maintenance personnel through at least one of the following methods: WeChat mini program, mobile phone text message, email, and on-site sound and light alarm.

[0066] This implementation obtains the equivalent impedance parameters corresponding to each frequency point through multi-band impedance calibration, generating a frequency-impedance mapping table. This allows the equivalent impedance parameters to be dynamically adjusted according to the actual operating frequency, rather than using a single fixed value. Therefore, when long-distance cables have different impedance effects on currents of different frequencies, dynamic impedance compensation can select the corresponding equivalent impedance parameters for the current frequency, eliminating the distortion effect of cable impedance on the current sampling waveform.

[0067] This implementation establishes a correspondence between operating frequency and normal current characteristics through a frequency-current characteristic mapping table, enabling the current characteristic template parameters to change synchronously with the actual operating frequency. Therefore, when the normal operating current changes with the frequency under variable frequency drive, the dynamic characteristic template parameters can provide a matching reference adapted to the current frequency, avoiding the problem of a single fixed current characteristic template parameter misjudging normal operation as a fault at non-calibrated frequencies.

[0068] This implementation combines dynamic impedance compensation with dynamic characteristic matching. Impedance compensation eliminates waveform distortion introduced by the cable, while dynamic characteristic matching eliminates characteristic drift caused by frequency conversion. Therefore, in the combined operating conditions of long-distance cable and frequency conversion drive, the current characteristic quantity after impedance compensation correction can accurately match the dynamic characteristic template parameters corresponding to the current frequency, thereby achieving accurate determination of the actuator response state under combined operating conditions.

[0069] A decentralized water station in a rural suburb of a city, located in a mountainous area 25 kilometers from the city center, is responsible for providing drinking water to approximately 2,000 households in six surrounding villages. Built in 2023, the station's main pump house and chemical dosing room are 180 meters apart, while the sampling pump house and main control room are 220 meters apart. The station is equipped with three water quality sensors: turbidity, pH, and residual chlorine. The main actuators include one main water supply pump (rated power 11kW), one chemical dosing pump (rated power 0.75kW), and one sampling pump (rated power 0.37kW). To achieve energy-saving operation and precise flow control, all three pumps are driven by frequency converters, operating at a frequency range of 25Hz to 50Hz. Due to the mountainous terrain, the control unit and actuators are connected by direct-buried cables, with the main water supply pump cable reaching 185 meters in length (YJV-3×10mm). 2 The dosing pump cable is up to 95 meters long (YJV-3×2.5mm). 2 The sampling pump cable is 225 meters long (YJV-3×2.5mm). 2 In January 2026, the integrated control unit was put into operation for upgrade and transformation.

[0070] Example of implementing core step 1: collecting water quality monitoring data.

[0071] At 10:15 AM on January 21, 2026, the integrated control unit acquired raw signals from various sensors via an RS485 bus. The turbidity sensor output a 4-20mA current signal, the pH sensor outputs a 0-10V voltage signal, and the residual chlorine sensor outputs a 4-20mA current signal. The signal conditioning circuit converted these analog signals into digital quantities, which were then filtered, amplified, and stored.

[0072] Table 1. Input raw signal data for step 1: Table 2 shows the output digital measurement values ​​from step 1: The conversion and calculation process of turbidity digital measurement values: The conversion and calculation process of digital pH measurement values: The conversion and calculation process of residual chlorine digital measurement values: Figure 2 The digital measurements of three parameters—turbidity (5.5 NTU), pH (7.35), and residual chlorine (0.35 mg / L)—are compared with the upper limit of their measurement ranges.

[0073] Example of implementing core step 2: Calibrate multi-band impedance.

[0074] During the system initialization phase on January 21, 2026, multi-band impedance calibration was performed on the sampling pump (cable length 225 meters). The sampling pump inverter operates in the frequency range of 25Hz to 50Hz, and six calibration frequency points were selected: 25Hz, 30Hz, 35Hz, 40Hz, 45Hz, and 50Hz.

[0075] Table 3. Calibration signal sequence parameters for step 2: Impedance calculation example at 25Hz frequency: The response current waveform acquired by the current sampling module is subjected to Fourier transform, and the amplitude of the fundamental component is extracted. The phase difference is Excitation voltage amplitude .

[0076] Calculation of equivalent resistance and reactance components: Table 4. Frequency-Impedance Mapping Table for Step 2: Figure 3 The impedance characteristics of the sampling pump (cable length 225 meters) were demonstrated at six calibrated frequency points from 25Hz to 50Hz.

[0077] Figure 4 It shows the increasing trend of phase angle in the frequency range of 25Hz to 50Hz.

[0078] Example of implementing core step 3: compensating for dynamic impedance.

[0079] At 14:30 on January 21, 2026, the water station entered normal operation. Based on the water quality monitoring requirements, the control unit issued a target frequency setting of 38Hz to the sampling pump inverter, driving the sampling pump to collect water samples at a medium flow rate.

[0080] The target frequency of 38Hz falls between the calibration frequencies of 35Hz and 40Hz. Linear interpolation is used to calculate the equivalent impedance parameters corresponding to the current frequency. Select 50Hz as the reference operating frequency, and use the reference impedance value. .

[0081] The effective value of the real-time current waveform acquired by the current sampling module is Perform impedance compensation correction calculation: Table 5 shows the impedance compensation data for step 3: Table 6 shows the results of current feature extraction in step 3: Figure 5 The results before and after compensation are shown in terms of current amplitude and current phase.

[0082] Implementation example of core step 4: matching dynamic features.

[0083] The integrated control unit calculates dynamic feature template parameters by interpolation from a pre-stored frequency-current feature mapping table for a 38Hz operating frequency.

[0084] Current characteristic template parameters corresponding to 35Hz and 40Hz in the frequency-current characteristic mapping table: 35Hz: Standard current amplitude 1.75A, standard current phase 41.8°, standard third harmonic content 4.8%. 40Hz: Standard value for current amplitude is 1.85A, standard value for current phase is 43.3°, and standard value for third harmonic content is 5.5%. Linear interpolation at 38Hz: Table 7 Feature matching data for step 4: Construct the normalized feature vector: Calculate the Euclidean distance: Calculate the matching degree: Figure 6 The normalized comparison of three characteristic parameters at 38Hz is shown.

[0085] Example of implementing core step 5: Determine the fault and output control commands.

[0086] The system's preset dynamic threshold is 0.80, and the current matching degree is... The sampling pump was determined to be responding normally.

[0087] According to the pre-stored control program, the integrated control unit continuously drives the sampling pump to operate from 14:30 to 14:45, collecting water samples for online monitoring of three indicators: turbidity, pH, and residual chlorine. The control unit sends a frequency setting signal (analog voltage 7.6V, corresponding to 38Hz) to the sampling pump inverter through the output circuit, and at the same time outputs a relay contact closing signal to start the sampling pump.

[0088] Table 8 Control output data for step 5: During the same period, the integrated control unit uploaded water quality monitoring data (turbidity 5.5 NTU, pH 7.35, residual chlorine 0.35 mg / L) and equipment operating status (sampling pump operating at 38 Hz, matching degree 0.9965) to the smart water management cloud platform via the 4G communication module. Maintenance personnel could then monitor the water station's operating status in real time via a WeChat mini-program to confirm that all indicators were normal.

[0089] Figure 7 The comparison of cable length and rated power distribution of the three water pumps is shown.

[0090] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A method for intelligent water quality monitoring and distributed control, characterized in that, Includes the following steps: Collect water quality monitoring data. Collect water quality monitoring data from each sensor through an integrated control unit. After processing by the signal conditioning circuit, obtain the digital measurement values ​​of each water quality parameter. To calibrate the multi-band impedance, a multi-band calibration signal sequence is applied sequentially to the actuator circuit. The response waveforms of each frequency band are collected. The equivalent impedance parameters corresponding to each frequency band are calculated based on the excitation voltage amplitude, response current amplitude, and phase difference of each frequency band, and a frequency-impedance mapping table is generated. Compensate dynamic impedance, obtain the target frequency setting value sent to the frequency converter, calculate the equivalent impedance parameter corresponding to the current frequency by interpolation from the frequency-impedance mapping table based on the target frequency setting value, perform impedance compensation correction operation on the current sample value, and obtain the compensated current characteristic quantity. Matching dynamic features involves interpolating the corresponding dynamic feature template parameters from the frequency-current feature mapping table based on the target frequency setting value, and then performing a matching operation between the compensated current feature quantity and the dynamic feature template parameters to obtain the matching degree result. The system identifies faults and outputs control commands. When the matching degree is lower than the dynamic threshold, the system marks the fault state and locks the control output. When the actuator is in normal condition, the system drives the actuator to move according to the control program.

2. The intelligent water quality monitoring and distribution control method according to claim 1, characterized in that, The multi-band calibration signal sequence includes calibration signals corresponding to multiple discrete frequency points within the range from the lowest operating frequency to the highest operating frequency. The lowest and highest operating frequencies are determined by the frequency adjustment range of the frequency converter. The duration of the calibration signal at each frequency point is not less than 3 to 5 times the corresponding frequency period.

3. The intelligent water quality monitoring and distribution control method according to claim 1, characterized in that, The calculation of the equivalent impedance parameter includes: extracting the amplitude of the fundamental component by performing a Fourier transform on the acquired current response waveform as the amplitude of the response current; calculating the phase angle difference between the excitation voltage and the fundamental component of the response current as the phase difference; determining the impedance amplitude based on the ratio of the excitation voltage amplitude to the response current amplitude; determining the equivalent resistance component based on the product of the impedance amplitude and the cosine of the phase angle; and determining the equivalent reactance component based on the product of the impedance amplitude and the sine of the phase angle.

4. The intelligent water quality monitoring and distribution control method according to claim 1, characterized in that, The impedance compensation correction operation is as follows: multiply the real-time current waveform by the ratio of the reference impedance value to the current equivalent impedance parameter to obtain the compensated current waveform. The reference impedance value is the equivalent impedance parameter corresponding to the reference operating frequency, and the reference operating frequency is the rated operating frequency of the actuator; the current characteristic quantities extracted from the compensated current waveform include at least one of current amplitude, current phase, and current harmonic content. The frequency distribution density in the multi-band calibration signal sequence is adaptively adjusted according to the impedance change gradient, which is obtained by calculating the ratio of the impedance difference to the frequency difference between adjacent frequency points. When the impedance change gradient exceeds a preset gradient threshold, additional frequency points are inserted in the interval corresponding to the adjacent frequency points for supplementary calibration.

5. The intelligent water quality monitoring and distribution control method according to claim 1, characterized in that, The establishment of the frequency-current feature mapping table includes: driving the actuator to perform a complete action process of starting, steady-state operation and stopping at each calibration frequency point; collecting the current waveform at each calibration frequency point and extracting the current feature quantity after performing impedance compensation correction calculation; statistically averaging the current feature quantity collected from multiple normal operations to obtain the current feature template parameter; and associating and storing the current feature template parameter with the corresponding calibration frequency point.

6. The intelligent water quality monitoring and distribution control method according to claim 1, characterized in that, The matching operation includes: normalizing the compensated current characteristic quantity and the dynamic characteristic template parameter; calculating the Euclidean distance between the normalized current characteristic quantity vector and the normalized dynamic characteristic template parameter vector; and determining the matching degree based on the ratio of the Euclidean distance to the norm of the normalized dynamic characteristic template parameter vector, wherein the matching degree is equal to 1 minus the ratio.

7. The intelligent water quality monitoring and distribution control method according to claim 1, characterized in that, The method for determining the fault and outputting control commands further includes: setting a threshold for the number of consecutive determinations; when the matching degree of a preset number of consecutive determinations is lower than the dynamic threshold, the fault state is confirmed; the dynamic threshold is adaptively adjusted according to the operating frequency; when the operating frequency is in the range of drastic impedance changes, the dynamic threshold is reduced; when the operating frequency is in the range of gradual impedance changes, the dynamic threshold is increased.

8. The intelligent water quality monitoring and distribution control method according to claim 1, characterized in that, Also includes: Periodically perform local impedance verification. During idle periods of the actuator, apply a single-frequency verification signal to the actuator circuit to calculate the deviation between the current impedance value and the corresponding value in the frequency-impedance mapping table. When the deviation exceeds a preset threshold, trigger the frequency-impedance mapping table update or issue a maintenance prompt. Upload water quality monitoring data, equipment operating status, and alarm information to the cloud platform through the communication module. When an alarm flag is generated, push alarm messages through at least one of the following methods: WeChat mini program, mobile phone SMS, email, and on-site audible and visual alarm.

9. A water quality intelligent monitoring and distribution control system, used to execute the water quality intelligent monitoring and distribution control method according to any one of claims 1 to 8, characterized in that, include: The data acquisition module is used to collect water quality monitoring data from various sensors, and after processing by the signal conditioning circuit, obtain the digital measurement values ​​of each water quality parameter. The impedance calibration module is used to sequentially apply a multi-band calibration signal sequence to the actuator circuit, collect the response waveform of each frequency band, calculate the equivalent impedance parameters corresponding to each frequency band, and generate a frequency-impedance mapping table. The impedance compensation module is used to obtain the target frequency setting value sent to the frequency converter, interpolate the equivalent impedance parameter corresponding to the current frequency from the frequency-impedance mapping table according to the target frequency setting value, perform impedance compensation correction operation on the current sample value, and obtain the compensated current characteristic quantity. The feature matching module is used to interpolate and calculate the corresponding dynamic feature template parameters from the frequency-current feature mapping table according to the target frequency setting value, and to perform matching operation between the compensated current feature quantity and the dynamic feature template parameters to obtain the matching degree result. The fault determination and control module is used to mark the fault state and lock the control output when the matching degree is lower than the dynamic threshold, and drive the actuator to act according to the control program when the actuator is in normal state.

10. A storage medium for storing computer-readable instructions, characterized in that, When the computer-readable instructions are read, the water quality intelligent monitoring and distribution control method according to any one of claims 1 to 9 can be executed.

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