Energy-saving full-automatic control water inlet control method for waterworks

Abstract

The invention discloses an energy-saving full-automatic control water inlet control method for a waterworks, and the method comprises the steps: building a clean water tank water inlet flow model according to a difference value between an actual water level of a clean water tank and a preset water level of the clean water tank and the water inlet amount of the clean water tank, and calculating a clean water tank water inlet flow sequence value; calculating the preset water level of the clarification tank according to the water inlet flow sequence value of the clear water tank, and constructing a clarification tank valve adjustment model according to the actual water level of the clarification tank and the preset water level of the clarification tank to obtain the valve opening of the clarification tank; according to the actual water level of the clean water tank, the actual effect of the water level control method is judged, and the clean water tank water inlet flow sequence value and the clarification tank valve opening degree are continuously optimized based on the real-time data feedback result. Aiming at the time lag characteristic of a multi-stage series process of a water plant, a strategy of combining water inlet flow sequence prediction and valve opening dynamic compensation is adopted, the limitation of slow response of traditional PID control to a lag link is broken through, and the high water level of a clean water tank is maintained.

Description

Technical Field

[0001] The present invention relates to the field of information technology, and particularly to a fully automatic control water inlet control method for energy saving in a waterworks. Background Art

[0002] The difficulty in unattended operation of a waterworks is the automation of water distribution in the waterworks. A typical waterworks adopts a technological process of water distribution + coagulation sedimentation + filtration + clear water tank + water supply pump house. The total process time is relatively long, generally calculated in hours. An algorithm that can not only achieve water distribution automation but also save energy has high application value. The capacity of the clear water tank is generally 20% of the daily water production of the tap water. It is mainly used to maintain the stability of the water treatment process when the customer water consumption (outlet water) fluctuates. Raising the water level of the clear water tank can not only cope with abnormal customer demands but also reduce the total head of the water supply pump house when meeting the water pressure required by the public water supply network. Generally, the depth of the clear water tank is 4 - 5 meters, which accounts for a relatively large proportion in the total head. Keeping the clear water tank at a high water level has obvious energy-saving effects.

[0003] The production process of a waterworks is a typical series system. Raw water generally enters the clarifier after passing through an inlet electric butterfly valve; the clarification process, that is, the coagulation sedimentation process, is equivalent to a lagging inertial link; the clarified water after sedimentation enters the filter tank. Since the filter tank adopts constant water level control for filtration and adjusts the filtration resistance by controlling the outlet valve to keep the filtration water level constant, the filtration rate of the filter tank is proportional to the water inflow of the filter tank and can be approximated as a pure lagging link. The filtered clear water enters the clear water tank to complete the water treatment process. Due to the large number of links and long time in the water treatment process, it is difficult to complete full-automatic water distribution by automatically adjusting the inlet valve and achieve the purpose of operating at a high water level in the clear water tank. Summary of the Invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention provides a fully automatic control water inlet control method for energy saving in a waterworks, which mainly includes:

[0005] Construct a clear water tank water inlet flow model according to the difference between the actual water level and the preset water level of the clear water tank and the water inflow of the clear water tank, calculate the sequence value of the clear water tank water inlet flow, and determine the clear water tank water inlet control scheme;

[0006] Convert the preset water level of the clarifier according to the sequence value of the clear water tank water inlet flow, construct a clarifier valve adjustment model according to the actual water level and the preset water level of the clarifier, obtain the opening degree of the clarifier valve, and determine the clear water tank water inlet control scheme;

[0007] Judge the actual effect of the water level control method according to the actual water level of the clear water tank, and continuously optimize the sequence value of the clear water tank water inlet flow and the opening degree of the clarifier valve based on the real-time data feedback result.

[0008] Further, based on the difference between the actual water level and the preset water level of the clear water tank and the water inflow of the clear water tank, a water inflow model of the clear water tank is constructed to calculate the sequence values of the water inflow of the clear water tank, including:

[0009] The real-time water inflow and the real-time water outflow are obtained by the water inflow meter and the water outflow meter installed in the clear water tank, and the real-time water level of the clear water tank is obtained by the water level meter installed in the clear water tank. A preset water demand level of the clear water tank is set. Taking the water level of the clear water tank as the control variable and the water inflow as the input variable, an integral time-delay model of the water inflow of the clear water tank is constructed where h is the difference between the actual water level and the preset water level of the clear water tank, s is the area of the clear water tank, and q in is the change in water inflow relative to the initial state at time t0, and q out is the change in water outflow relative to the initial state at time t0, and τ is the water inflow lag time. The sequence values of the water inflow of the clear water tank are calculated.

[0010] Further, the above integral model is discretized and analyzed, including:

[0011] The integral time-delay model of the water inflow of the clear water tank is discretized and analyzed,

[0012] where Ts is the discrete time interval, and k d = τ / T s is the number of lag steps. When k is less than k d , the measured flow value corresponding to the input flow of the clear water tank is used for substitution.

[0013] Further, according to the sequence values of the water inflow of the clear water tank, the preset water level of the clarifier is converted, including:

[0014] When the filter tank adopts constant water level control, a quadratic function of constant water level between the water level of the clarifier and the water outflow of the clarifier is constructed, and the sequence values of the water inflow of the clear water tank are converted into the preset water level of the clarifier through this quadratic function;

[0015] Further, based on the actual water level of the clear water tank, the actual effect of the water level control method is judged, and based on the real-time data feedback result, the sequence values of the water inflow of the clear water tank and the opening degree of the clarifier valve are continuously optimized, including:

[0016] An optimization function is constructed where Q is the error weight matrix, R is the control weight matrix, and w r (k) is the setpoint trajectory, and w r (k) is constantly the set value. The sequence values of the water inflow of the clear water tank are tracked and controlled through this optimization function, and the instant water level of the clear water tank is measured as the initial value of the next round of calculation, and enters the next round of calculation, and so on in a cycle.

[0017] Further, in the backwashing stage, the required water level value of the clarifier is obtained through a water level gauge to obtain the backwashing water level value of the clarifier. In the subsequent backwashing stage, the backwashing water level of the clarifier is used to replace the preset water level of the clarifier.

[0018] Further, based on the inlet water control scheme of the clarifier and the inlet water control scheme of the clear water tank, a water level adjustment strategy is constructed to judge the water level control effect. Based on the real-time data feedback result, the inlet water lag time of the clear water tank and the clarifier is adjusted to continuously optimize the water level adjustment strategy.

[0019] The technical solution provided by the embodiment of the present invention may include the following beneficial effects:

[0020] The present invention provides a fully automatic control inlet water control method for energy saving in a waterworks. Aiming at the time-delay characteristics of the multi-stage series process in the waterworks, a strategy combining inlet water flow sequence prediction and dynamic compensation of valve opening is adopted to break through the limitation that the traditional PID control is insensitive to the lag link. While maintaining a high water level in the clear water tank, the water level set value of the clarifier is dynamically corrected based on real-time water level monitoring data, effectively balancing the contradiction between energy saving requirements and system stability, reducing the amplitude of the water level fluctuation in the whole process compared with the prior art, and realizing the accurate tracking of the preset trajectory of the clear water tank water level without relying on manual experience adjustment, and finally achieving the goal of continuous energy-saving operation without unattended operation. Description of the Drawings

[0021] Figure 1 is a flowchart of the present invention;

[0022] Figure 2 is a schematic diagram of a waterworks;

[0023] Figure 3 is a schematic diagram of the present invention; Detailed Embodiments

[0024] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be described in detail below with reference to the drawings and specific embodiments.

[0025] As Figures 1-3 , a fully automatic control inlet water control method for energy saving in a waterworks in this embodiment may specifically include:

[0026] Step S1, for the control algorithm of the clear water tank water level control system, according to the difference between the actual water level of the clear water tank and the preset water level of the clear water tank and the water inflow of the clear water tank, a clear water tank water inflow model is constructed, the clear water tank water inflow sequence value is calculated, and the clear water tank inlet water control scheme is determined.

[0027] Specifically, the real-time influent flow rate and the real-time effluent flow rate are obtained through the influent flowmeter and the effluent flowmeter installed in the clear water tank, and the real-time water level of the clear water tank is obtained through the water level gauge installed in the clear water tank. A preset required water level of the clear water tank is set. Taking the water level of the clear water tank as the control variable and the influent flow rate as the input variable, an integral time-delay model of the influent flow rate of the clear water tank is constructed. where h is the difference between the actual water level of the clear water tank and the preset water level of the clear water tank, s is the area of the clear water tank, and q in is the change in the influent flow rate relative to the initial state at time t0, and q out is the change in the effluent flow rate relative to the initial state at time t0, and τ is the influent lag time, and the sequence value of the influent flow rate of the clear water tank is calculated.

[0028] For the integral time-delay model of the influent flow rate of the clear water tank carry out discrete analysis,

[0029] where Ts is the discrete time interval and k d = τ / T s is the number of lag steps.

[0030] The parameters of the pure lag time period are set as follows: Since there is a pure lag time in the system, the determination of the parameters of the pure lag time period depends on the actual situation of the on-site process. In the discretization formula, when k is less than k d , q in cannot be calculated. From the actual situation, during the pure lag time period, since the newly calculated input flow rate has not affected the clear water tank after implementation, the input volume of the clear water tank can be replaced by the corresponding measured flow rate value. Considering that there is generally no flowmeter installed between the effluent of the clarifier and the influent of the clear water tank, and the clarifier is generally equipped with a water level gauge, its flow rate can be converted by the water level of the clarifier. The output flow rate of the clear water tank also adopts the measured value.

[0031] When k is less than k d , the input flow rate of the clear water tank is replaced by the corresponding measured flow rate value, and this measured flow rate value is converted by the water level of the clarifier.

[0032] Denote the influent flow rate as u(k), the depth of the clear water tank as x(k), the pure lag time as k d , the effluent flow rate as d(k), and the influent flow rate q in during the lag period as u0(k). Then the constant term D(k) takes the value of D(k) = u0(k) - d(k) during the pure lag time period and -d(k) after the lag time. The discretized equation is written in the following vector form:

[0033] X(k + 1) = x(K) + Bu(k) + D(k)

[0034] Let α = Ts / S, outside the control time domain, u(k) no longer changes, the prediction time domain is p, and the control time domain is m; starting from time k, expand the formula X(k + 1) = x(K) + Bu(k) + D(k) according to the prediction steps, and we get:

[0035]

[0036] According to the above expansion formula, the coefficient matrix corresponding to the formula X(k + 1) = x(K) + Bu(k) + D(k) is as follows, where the number of rows of the 0 in the B matrix is the number of lag time steps k d 。

[0037]

[0038] Obtain the sequence values of the influent flow rate of the clear water tank.

[0039] Since there is generally no flow meter installed between the clarifier and the filter, therefore, for the calculated flow rate values above, they cannot be directly used as the control variables for the next control link. And generally, a water level gauge is installed in the clarifier, so this flow rate value can be converted into the corresponding water level value. There is a filter between the clarifier and the clear water tank. Generally, the filter adopts constant water level control. Therefore, during normal filtration, the flow rate from the clarifier to the filter is solely determined by the water level of the clarifier; since the filter generally adopts a water-sealed outlet structure to isolate the influence of the outlet main pipe pressure or the water level of the clear water tank on filtration, the filtration flow rate has nothing to do with the water level of the clear water tank. The relationship between the water level and the water output of the clarifier can be measured in advance, and generally, the least squares method can be used to fit it into a quadratic function. According to the actual situation of the on-site process facilities, if the water output of the clarifier is related to the water level of the filter, it is changed to measure the relationship between the water output and the water level difference between the two. The converted water level is used as the set water level value of the clarifier control system. In view of the non-linear relationship between the water level and the flow rate of the clarifier, the invention adopts a two-stage control system to calculate separately instead of directly using a series system to calculate, reducing the complexity of the calculation; adopting a two-stage separate control system also lies in that when encountering process changes such as backwashing in the process, it can be easily operated normally by changing the set value. Accordingly, step S2 is set.

[0040] Step S2, according to the sequence values of the influent flow rate of the clear water tank, convert to the preset water level of the clarifier, including:

[0041] When the filter adopts constant water level control, construct a constant water level quadratic function between the water level of the clarifier and the effluent flow rate of the clarifier, and convert the sequence values of the influent flow rate of the clear water tank into the preset water level of the clarifier through this quadratic function;

[0042] Step S3, the control algorithm of the clarifier water level control system, according to the actual water level of the clarifier and the preset water level of the clarifier, construct a clarifier valve adjustment model, obtain the opening degree of the clarifier valve, and determine the control scheme for the influent of the clear water tank.

[0043] Specifically, by controlling the opening of the inlet valve to track the set value of the clarifier water level, first calculate the required inlet flow rate. The inlet flow rate can be converted into the valve opening, and then through the inlet valve control system, adjust the valve opening to complete the control of the clarifier water level.

[0044] The control algorithm of the clarifier water level control system is the same as the above-mentioned clear water tank water level control algorithm. Briefly speaking, in the control algorithm of the clarifier water level control system, the preset water level of the clarifier is equivalent to the preset water level of the clear water tank, and the inlet flow rate, outlet flow rate, pool area, and inlet lag time are also calculated in the same way, and the same integral time-delay model is adopted. Details are not elaborated here. Its mathematical model is similar to that of the clear water tank water level control system, but the pure lag time is shorter and the inertia is slightly larger. Therefore, there are differences in the selection of model parameters. By selecting the step size, prediction time domain, and control time domain, its dynamic characteristics are matched with those of the clear water tank water level control system, so as to complete the tracking control of the clarifier water level well. In the control algorithm, the processing of the lag time and the processing of the inlet flow rate and outlet flow rate during the lag period are the same as the above method, and both are dealt with by changing the coefficient matrix of the control system.

[0045] Step S4: According to the actual water level of the clear water tank, judge the actual effect of the water level control method, and continuously optimize the inlet flow rate sequence value of the clear water tank and the valve opening of the clarifier based on the real-time data feedback result.

[0046] Construct an optimization function for the control algorithm of the clarifier and the control algorithm of the clear water tank. Through this optimization function, track and control the inlet flow rate sequence value of the clear water tank, measure the instantaneous water level of the clear water tank, use it as the initial value for the next round of calculation, and enter the next round of calculation, and so on in a cycle.

[0047] Where Q is the error weight matrix, R is the control weight matrix, w r (k) is the set value trajectory, w r (k) is constantly the set value. Through this optimization function, track and control the inlet flow rate sequence value of the clear water tank, measure the instantaneous water level of the clear water tank, use it as the initial value for the next round of calculation, and enter the next round of calculation, and so on in a cycle.

[0048] The specific calculation is as follows:

[0049]

[0050] R = diag(r1r2…r m )

[0051] w r (k + 1) = [w r (k + 1)wr (k + 2)…w r (k + p)] T

[0052] Write the equation X(k + 1) = x(K) + Bu(k) + D(k) in matrix form

[0053]

[0054] Rewrite it as

[0055]

[0056] Denote the above equation as: x = Bu + m, and substitute it into the optimization function

[0057] Let H = 2(B T QB + R), c T = (-2(m - w r ) T QB), Remove the terms unrelated to optimization and write the function in standard quadratic form:

[0058]

[0059] The constraint condition for the water level in the clear water tank is x max , and the inlet water constraint condition is u max . From the equation x(k + 1) = x(k) + Bu(k) + D(k), the constraint conditions are:

[0060] u(k) ≤ u max

[0061] x(k + 1) = x(k) + Bu(k) + D(k) ≤ x max That is, Bu(k) ≤ x max -x(k) - D(k)

[0062] Write the optimization function and constraint conditions in standard quadratic form

[0063]

[0064] In this way, the rolling optimization becomes a quadratic programming problem with inequality constraints

[0065] For the above quadratic programming problem with constraints, due to the presence of inequality constraints, its optimal solution can only be obtained numerically. Since H is a positive definite matrix, it can be solved under the KKT conditions. For the equation

[0066]

[0067] Introduce Lagrange vector multipliers λ1 ≥ 0, λ2 ≥ 0 and construct the Lagrangian function

[0068]

[0069] The KKT conditions are as follows:

[0070]

[0071] The above formula is solved numerically online by a computer. After obtaining the optimal sequence value online, the calculated sequence value is used as the influent flow rate sequence value of the clear water tank. Then, the preset water level of the clarifier is converted through step S2, and the opening of the influent valve is adjusted by the clarifier water level control system for tracking control. The instant water level of the clear water tank is measured and used as the initial value for the next round of calculation, and the next round of calculation is entered, and so on in a cycle.

[0072] For the control algorithm of the above control system, feedback correction can also be performed using measured values. Specifically, the value of the water level of the clear water tank, i.e., the state variable x(k), measured in real time is used as the initial value for the new round of iterative calculation to achieve feedback control.

[0073] During the backwashing stage of the waterworks, the filter media in the filter gradually become blocked due to intercepting impurities and need to be backwashed with reverse water flow to restore the filtration performance. During this process, the water in the clear water tank needs to be used for backwashing, resulting in a significant reduction in the actual influent flow rate of the clear water tank and a decrease in the water level of the clear water tank. At this time, if the influent control scheme described in the present invention is adopted, it will result in a greater calculated demand for the influent flow rate of the clear water tank and a corresponding large demand for the effluent flow rate of the clarifier, thus causing the system to get out of control. Therefore, during the backwashing stage, the influent flow rate sequence value of the clear water tank obtained in step S1 is discarded, and the preset water level of the clarifier obtained by other methods is directly used in step S3. The specific method is as follows: The required flow rate or the corresponding water level value during the backwashing stage is calculated offline in advance, the backwash water level of the clarifier is calculated, and this is used as the preset water level of the clarifier during the backwashing stage and substituted into the control algorithm of the clarifier water level control system, and the remaining steps remain unchanged. Finally, it can be avoided that the influent control method for the full-automatic control of energy conservation of the entire waterworks gets out of control.

[0074] For the clarifier influent control scheme and the clear water tank influent control scheme, feedback correction can also be performed according to the actual measurement results and actual effects. Specifically, based on the clarifier influent control scheme and the clear water tank influent control scheme, a water level adjustment strategy is constructed, the water level control effect is judged, and based on the real-time data feedback result, the influent lag time of the clear water tank and the clarifier is adjusted to continuously optimize the water level adjustment strategy.

[0075] The influent lag time refers to the specific value of τ in the integral time-delay model mentioned above in it.

[0076] The above description is only a preferred embodiment of the present application and an explanation of the applied technical principles. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solutions formed by the specific combination of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the concept of the present application. For example, the technical solutions formed by mutually replacing the above features with the technical features (but not limited to) disclosed in the present application that have similar functions.

Claims

1. A fully automatic water inlet control method for energy saving in a waterworks, characterized in that: The method comprises: According to the difference between the actual water level of the clear water tank and the preset water level of the clear water tank and the water inflow of the clear water tank, a clear water tank inflow flow model is constructed, the clear water tank inflow flow sequence value is calculated, and the clear water tank inflow control plan is determined; According to the sequence value of the clear water tank inlet flow, the preset water level of the clarifier tank is calculated; According to the actual water level of the clarifier and the preset water level of the clarifier, the clarifier inlet flow model is constructed to obtain the clarifier valve opening and determine the clarifier inlet control plan; According to the actual water level of the clear water tank, the actual effect of the water level control method is judged, and based on the real-time data feedback results, the clear water tank inlet flow sequence value and the clarifier valve opening are continuously optimized.

2. The method according to claim 1, wherein: The method is characterized in that: according to the difference between the actual water level of the clear water tank and the preset water level of the clear water tank and the water inflow of the clear water tank, a clear water tank inflow flow model is constructed, the clear water tank inflow flow sequence value is calculated, and the clear water tank inflow control scheme is determined. The real-time inlet flow rate and real-time outlet flow rate are obtained through the inlet flow meter and outlet flow meter installed in the clean water tank, and the real-time water level of the clean water tank is obtained through the water level meter installed in the clean water tank. A required water level of the clean water tank is preset, and the water level of the clean water tank is used as the control variable and the inlet flow rate is used as the input variable to construct an integral time-lag model of the inlet flow rate of the clean water tank. Where h is the difference between the actual water level of the clean water tank and the preset water level of the clean water tank, s is the area of ​​the clean water tank, q in The change of water inlet flow rate relative to the initial state at time t0, q out is the change in the outflow flow rate relative to the initial state at time t0, τ is the water inlet lag time, and the sequence value of the clear water tank inlet flow rate is calculated.

3. The energy-saving fully automatic water inlet control method of a waterworks according to claim 2 is characterized in that: Integral time-delay model for the inflow flow of clean water tank To perform discretization analysis, Where Ts is the discrete time interval, k d =τ / T s is the number of lag steps, when k is less than k d When the input flow of the clean water tank is replaced by the corresponding measured flow value.

4. The energy-saving fully automatic water inlet control method of a waterworks according to claim 1, wherein: According to the sequence value of the water flow rate of the clear water tank, the preset water level of the clarifier tank is calculated, which is characterized by: When the filter tank adopts constant water level control, a constant water level quadratic function of the clarifier water level and the clarifier effluent flow is constructed, and the clear water tank inlet flow sequence value is converted into the clarifier preset water level through the quadratic function.

5. According to the energy-saving fully automatic water inlet control method of the waterworks of claim 1, the actual effect of the water level control method is judged according to the actual water level of the clear water tank, and the sequence value of the clear water tank inlet flow and the valve opening of the clarifier tank are continuously optimized based on the real-time data feedback results, characterized in that: Building an optimization function Where Q is the error weight matrix, R is the control weight matrix, and w r (k) is the set value trajectory, w r (k) is constant as a set value. The optimization function is used to track and control the sequence value of the water flow rate of the clean water tank, measure the instantaneous water level of the clean water tank, and use it as the initial value for the next round of calculations to enter the next round of calculations, and repeat this cycle.

6. The energy-saving fully automatic water inlet control method of a waterworks according to claim 1, characterized in that: In the backwash stage, the required water level value of the clarifier is obtained by a water level meter to obtain the backwash water level value of the clarifier. In the subsequent backwash stage, the backwash water level of the clarifier is used to replace the preset water level of the clarifier.

7. The energy-saving fully automatic water inlet control method of a waterworks according to claim 2, characterized in that: Based on the clarifier tank inlet control scheme and the clear water tank inlet control scheme, a water level adjustment strategy is constructed to judge the water level control effect. Based on the real-time data feedback results, the water inlet lag time of the clear water tank and the clarifier tank is adjusted to continuously optimize the water level adjustment strategy.

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