A method for controlling dissolved oxygen concentration in a biological aeration tank and related components

Abstract

The present invention provides a method for controlling dissolved oxygen concentration in a biological aeration tank and related components, and relates to the field of environmental protection technology. A fuzzy controller is designed based on the water inlet and dissolved oxygen concentration data sequence. Specifically, the present application adopts a double-loop control strategy, in which the outer loop calculates the desired air volume of the aeration tank based on the fuzzy controller, and the inner loop adjusts the valve opening to ensure that the actual output air volume of the aeration tank is consistent with the desired air volume. Compared with the prior art, this solution requires fewer instruments, has the advantages of low cost and strong robustness, and can effectively overcome the influence of water inlet fluctuations on dissolved oxygen concentration control, thereby indirectly ensuring the effluent quality of the sewage treatment plant.

Description

Technical Field

[0001] The invention relates to the technical field of environmental protection, and in particular to a method for controlling dissolved oxygen concentration in a biological aeration tank and related components. Background Art

[0002] The dissolved oxygen control in the sewage aeration tank can provide a good living environment for the growth of microorganisms and the degradation of pollutants, thereby indirectly ensuring the effluent quality after biochemical treatment. The dissolved oxygen concentration control in the aeration tank is usually achieved by precise aeration, that is, the precise air volume is provided to the aeration tank through the aeration equipment to achieve precise control of the dissolved oxygen concentration in the aeration tank, thereby improving the effluent quality and reducing the energy consumption of the sewage treatment plant.

[0003] The traditional method of precise dissolved oxygen control is mainly based on the ASM (Activated sludge Model) strategy. This method calculates the oxygen demand of the aeration tank by establishing an activated sludge model of the biochemical tank. This method is complex to model, requires many monitoring instruments during project implementation, and requires regular calibration of the model, which affects its application in actual engineering. Summary of the invention

[0004] The purpose of the present invention is to provide a method for controlling dissolved oxygen concentration in a biological aeration tank and related components. The implementation of this solution requires only a small number of instruments and has the advantages of low cost and strong robustness. It can effectively overcome the influence of water inlet fluctuations on dissolved oxygen concentration control and provide important support for the normal operation of the aeration tank.

[0005] In order to solve the above technical problems, the present invention provides a method for controlling dissolved oxygen concentration in a biological aeration tank, comprising:

[0006] Obtaining a data sequence of water inflow into an aeration tank and dissolved oxygen concentration in the aeration tank during a current control period;

[0007] Determine the desired air volume based on the water inflow, the dissolved oxygen concentration data sequence and a pre-designed fuzzy controller;

[0008] The opening of the valve is adjusted according to the desired air volume to ensure that the actual output air volume output to the aeration tank is consistent with the desired air volume.

[0009] Preferably, the dissolved oxygen concentration data sequence includes N dissolved oxygen concentration data, where N is an integer greater than 1;

[0010] Determining the desired air volume based on the water inflow, the dissolved oxygen concentration data sequence and a pre-designed fuzzy controller includes:

[0011] Subtracting each dissolved oxygen concentration data from a preset dissolved oxygen concentration reference value to obtain corresponding deviation data, each deviation data forming a deviation sequence, and the total number of the deviation data is N;

[0012] Inputting the deviation sequence, the water inflow and the dissolved oxygen concentration data sequence as input items into a pre-designed fuzzy controller;

[0013] The desired air volume is determined based on the output term of the fuzzy controller and the deviation sequence.

[0014] Preferably, before deducting each of the dissolved oxygen concentration data from the preset dissolved oxygen concentration reference value, the method further comprises:

[0015] Determining whether the current control period is within a preset transition time range;

[0016] If so, determining a corresponding preset dissolved oxygen concentration reference value based on the first preset relationship;

[0017] The first preset relationship is:

[0018]

[0019] Wherein, S is the preset dissolved oxygen concentration reference value, S0 is the preset steady-state reference value, Δt is the time difference between the end time of the current control cycle and the initial time of starting aeration, and T1 is the preset transition time;

[0020] If not, the corresponding preset dissolved oxygen concentration reference value is determined to be the preset steady-state reference value.

[0021] Preferably, the output term of the fuzzy controller includes a first coefficient k1 and a second coefficient k2;

[0022] Determining the desired air volume based on the output item of the fuzzy controller and the deviation sequence includes:

[0023] Determining a dissolved oxygen concentration equivalent deviation based on a second preset relationship and the deviation sequence;

[0024] The second preset relationship is:

[0025]

[0026] in, is the equivalent deviation of dissolved oxygen concentration, e i is the i-th deviation data, ω i is the weighting coefficient corresponding to the i-th deviation data;

[0027] Processing the deviation sequence based on a third preset relationship to obtain integral item data;

[0028] The third preset relationship is:

[0029]

[0030] Wherein, esum is the integral term data, and ΔT is the current control cycle interval;

[0031] Determine the desired air volume based on the first coefficient k1 and the second coefficient k2, the dissolved oxygen concentration equivalent deviation, the integral term data and a fourth preset relationship;

[0032] The fourth preset relationship is:

[0033]

[0034] Wherein, F is the desired air volume.

[0035] Preferably, after determining the dissolved oxygen concentration equivalent deviation based on the second preset relationship and the deviation sequence, the method further includes:

[0036] Determining an equivalent deviation difference value in the current control cycle based on the deviation sequence of the current control cycle and the deviation sequence of the previous control cycle;

[0037] Determine whether the dissolved oxygen concentration equivalent deviation and the corresponding equivalent deviation difference value satisfy the following fifth preset relationship:

[0038]

[0039] Wherein, sign represents a sign function, and de represents the equivalent deviation difference value;

[0040] If not, proceed to the step of processing the deviation sequence based on a third preset relationship to obtain integral item data;

[0041] If so, determining the desired air volume of the current control cycle based on the sixth preset relationship, the dissolved oxygen concentration equivalent deviation and the desired air volume of the previous control cycle;

[0042] The sixth preset relationship is:

[0043]

[0044] Among them, k3 is the third coefficient, F is the expected air volume of the current control cycle, and F0 is the expected air volume of the previous control cycle.

[0045] Preferably, it also includes:

[0046] Obtaining the actual output air volume output to the aeration tank during the current control cycle;

[0047] Determining a dilution rate according to the water inflow and the effective volume of the aeration tank;

[0048] Based on the dissolved oxygen concentration data sequence, the actual output air volume, the dilution rate, the sludge return ratio of the aeration tank and a pre-designed oxygen consumption rate calibration model, the oxygen consumption rate of the aeration tank in the next control cycle is determined and stored.

[0049] Preferably, the dissolved oxygen concentration data sequence includes N dissolved oxygen concentration data, where N is an integer greater than 1;

[0050] Based on the dissolved oxygen concentration data sequence, the actual output air volume, the dilution rate, the sludge return ratio of the aeration tank and a pre-designed oxygen consumption rate calibration model, the oxygen consumption rate of the aeration tank in the next control cycle is determined and stored, including:

[0051] Determine a theoretical dissolved oxygen concentration data sequence with oxygen consumption rate as a parameter to be determined based on the seventh preset relationship;

[0052] The seventh preset relationship is:

[0053] S(k+1)=f(U)S sat ΔT m +[1-q(1+r)ΔT m -f(U)ΔT m ]S(k)-OURΔT m

[0054] Wherein, S(k+1) is the k+1th theoretical dissolved oxygen concentration data in the theoretical dissolved oxygen concentration data sequence, and S(k) is the kth theoretical dissolved oxygen concentration data, 1≤k≤N-1 and k is an integer; f(U) is the oxygen transfer coefficient corresponding to the actual output air volume in the current control period, S sat is the saturated dissolved oxygen concentration of the aeration tank, q is the dilution rate, r is the sludge return ratio, ΔT m is the time difference between the sampling time corresponding to the k+1th dissolved oxygen concentration data and the sampling time corresponding to the kth dissolved oxygen concentration data;

[0055] And wherein, the first dissolved oxygen concentration data in the current control period is used as the first theoretical dissolved oxygen concentration data;

[0056] Based on the dissolved oxygen concentration data sequence A={a i}, the theoretical dissolved oxygen concentration data sequence B = {b i}, establishing an objective function with the oxygen consumption rate as a decision variable;

[0057] The objective function is:

[0058]

[0059] The decision variable of the objective function is the oxygen consumption rate OUR, and the constraint condition of the objective function is:

[0060] OUR∈[OUR min ,OUR max ]

[0061] Among them, the above is OUR min is the lower limit of the oxygen consumption rate OUR, the OUR max is the upper limit of the oxygen consumption rate OUR;

[0062] The objective function is optimized and solved to determine the oxygen consumption rate of the aeration tank.

[0063] In order to solve the above technical problems, the present invention also provides a biological aeration tank dissolved oxygen concentration control system, comprising:

[0064] A first data acquisition unit, used to acquire a data sequence of water inflow into the aeration tank and dissolved oxygen concentration in the aeration tank during a current control period;

[0065] A desired air volume calculation unit, used to determine the desired air volume based on the water inflow, the dissolved oxygen concentration data sequence and a pre-designed fuzzy controller;

[0066] The air volume tracking unit is used to adjust the opening of the valve according to the expected air volume to ensure that the actual output air volume output to the aeration tank is consistent with the expected air volume.

[0067] Preferably, it also includes:

[0068] A second data acquisition unit, used to acquire the actual output air volume output to the aeration tank during the current control period;

[0069] a dilution rate determination unit, used to determine the dilution rate according to the water inflow and the effective volume of the aeration tank;

[0070] The oxygen consumption rate calibration unit is used to determine and store the oxygen consumption rate of the aeration tank in the next control cycle based on the dissolved oxygen concentration data sequence, the actual output air volume, the dilution rate, the sludge return ratio of the aeration tank and a pre-designed oxygen consumption rate calibration model.

[0071] In order to solve the above technical problems, the present invention also provides a biological aeration tank dissolved oxygen concentration control device, comprising:

[0072] Memory for storing computer programs;

[0073] A processor is used to execute the steps of the method for controlling dissolved oxygen concentration in a biological aeration tank as described above.

[0074] The present application provides a biological aeration tank dissolved oxygen concentration control method and related components. A fuzzy controller is designed based on the water inlet and dissolved oxygen concentration data sequence. Specifically, the present application adopts a dual-loop control strategy, that is, the desired air volume of the aeration tank is calculated based on the fuzzy controller to achieve the desired air volume control of the outer loop; the valve opening is adjusted based on the desired air volume to achieve the valve opening control of the inner loop, thereby ensuring that the actual output air volume of the aeration tank is consistent with the desired air volume. Compared with the prior art, this solution requires fewer instruments, has the advantages of low cost and strong robustness, can effectively overcome the influence of water inlet fluctuations on dissolved oxygen concentration control, and thus indirectly ensure the effluent water quality of the biochemical pool. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the prior art and the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0076] Figure 1 A flow chart of a method for controlling dissolved oxygen concentration in a biological aeration tank provided by the present invention;

[0077] Figure 2 A structural block diagram of a double-loop control strategy for dissolved oxygen concentration in a biological aeration tank provided by the present invention;

[0078] Figure 3 A curve diagram of water inflow changing with time provided by the present invention;

[0079] Figure 4a It is a curve diagram of dissolved oxygen concentration changing with time in the prior art;

[0080] Figure 4b Another graph showing the change of dissolved oxygen concentration over time in the prior art;

[0081] Figure 5 A curve diagram of dissolved oxygen concentration changing over time provided by the present invention;

[0082] Figure 6 A curve diagram of oxygen consumption rate changing with time provided by the present invention;

[0083] Figure 7 A schematic diagram of the structure of a biological aeration tank dissolved oxygen concentration control system provided by the present invention;

[0084] Figure 8 The present invention provides a schematic structural diagram of a biological aeration tank dissolved oxygen concentration control device. DETAILED DESCRIPTION

[0085] The core of the present invention is to provide a biological aeration tank dissolved oxygen concentration control method and related components, which require fewer instruments and have the advantages of low cost and strong robustness. It can effectively overcome the influence of water inlet fluctuations on dissolved oxygen concentration control and provide important support for the normal operation of the aeration tank.

[0086] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0087] In this embodiment, it is considered that the methods for accurately controlling dissolved oxygen in the prior art are mainly: the control model established based on the ASM strategy has the disadvantages of complex modeling, more monitoring instruments required during project implementation, and regular calibration of the model, which affects its application in engineering practice. In order to solve the above technical problems, the present application provides a method for controlling dissolved oxygen concentration in a biological aeration tank.

[0088] Please refer to Figure 1 , Figure 1 The present invention provides a flow chart of a method for controlling dissolved oxygen concentration in a biological aeration tank.

[0089] The biological aeration tank dissolved oxygen concentration control method comprises:

[0090] S11: Obtaining a data sequence of water inflow into the aeration tank and dissolved oxygen concentration in the aeration tank during the current control period;

[0091] Specifically, the instrument used to obtain the water inlet volume may be a water inlet flow meter, and the instrument used to obtain the dissolved oxygen concentration data sequence may be an online dissolved oxygen concentration monitor. Correspondingly, the specific process of obtaining the dissolved oxygen concentration data sequence may be: obtaining the dissolved oxygen concentration data collected by the online dissolved oxygen concentration monitor with a preset sampling period, and the preset sampling period is usually within 1 minute and can be set according to actual needs.

[0092] It should be noted that this method specifically includes but is not limited to application in PLC control cabinets and industrial computers, and the PLC control cabinet can also be connected to a host computer so that the monitoring results can be intuitively displayed to developers; the specific duration of the control cycle is not particularly limited here and can be set according to actual needs, such as 15 minutes.

[0093] S12: Determine the desired air volume based on the water inflow, dissolved oxygen concentration data sequence and a pre-designed fuzzy controller;

[0094] Specifically, the present application adopts a dual-loop control strategy, so the desired air volume calculation of the outer loop can be realized according to step S12.

[0095] S13: adjusting the opening of the valve according to the desired air volume to ensure that the actual output air volume output to the aeration tank is consistent with the desired air volume.

[0096] It is understandable that the blower air volume regulating system is connected to the valve, and when the opening of the valve (such as the electric regulating valve) changes, the actual output air volume output by the blower air volume regulating system to the aeration tank will change accordingly. As an example, the description of step S13 is given. Assuming that in the current control cycle (corresponding to 15:00-15:15), the desired air volume is determined based on step S12, then the opening of the valve can be adjusted according to the desired air volume to ensure that the actual output air volume is consistent with the desired air volume within the preset adjustment time of the next control cycle (such as 15:15-15:19).

[0097] In summary, this application provides a biological aeration tank dissolved oxygen concentration control method and related components, and designs a fuzzy controller based on the water inlet and dissolved oxygen concentration data sequence. Specifically, this application adopts a dual-loop control strategy, that is, the outer loop calculates the desired air volume of the aeration tank based on the fuzzy controller, and the inner loop adjusts the valve opening to ensure that the actual output air volume of the aeration tank is consistent with the desired air volume. Compared with the prior art, this solution requires fewer instruments, has the advantages of low cost and strong robustness, can effectively overcome the impact of water inlet fluctuations on dissolved oxygen concentration control, and provides important support for the normal operation of the aeration tank.

[0098] Based on the above embodiments:

[0099] As a preferred embodiment, the dissolved oxygen concentration data sequence includes N dissolved oxygen concentration data, where N is an integer greater than 1;

[0100] Determine the desired air volume based on the water inflow, dissolved oxygen concentration data sequence and the pre-designed fuzzy controller, including:

[0101] Subtract each dissolved oxygen concentration data from the preset dissolved oxygen concentration reference value to obtain each deviation data, each deviation data constitutes a deviation sequence, and the total number of deviation data is N;

[0102] The deviation sequence, water inflow and dissolved oxygen concentration data sequence are input into the pre-designed fuzzy controller as input items;

[0103] The desired air volume is determined based on the output of the fuzzy controller and the deviation sequence.

[0104] In this embodiment, a specific method for determining the desired air volume is provided. The implementation steps have been described above and will not be repeated here. It can be seen that the determination of the desired air volume is reliably achieved through the above method, and it is easy to implement and debug on site.

[0105] Specifically, the fuzzy controller can essentially be understood as an executable software program installed in the PLC control cabinet. The fuzzy controller includes fuzzy reasoning rules, which can fuzzify the parameters input to the fuzzy controller, namely the deviation sequence, water inlet and dissolved oxygen concentration data sequence, and perform fuzzy reasoning according to the fuzzy reasoning rules, and defuzzify the results of the fuzzy reasoning as the output items of the fuzzy controller.

[0106] For details, please refer to Figure 2 , the figure shows a structural block diagram of a dual-loop control strategy for dissolved oxygen concentration in a biological aeration tank, wherein the circle in front of the fuzzy controller and the plus sign inside only represent the parameters input to the fuzzy controller and do not act as a comparator. Therefore, the inner loop realizes the control of the valve opening, and the outer loop realizes the control of the desired air volume. It can be seen that this application takes into account the influence of water inlet fluctuations and adds the water inlet as a feedforward link.

[0107] As a preferred embodiment, before deducting each dissolved oxygen concentration data from the preset dissolved oxygen concentration reference value, the method further includes:

[0108] Determine whether the current control cycle is within the preset transition time range;

[0109] If so, determining a corresponding preset dissolved oxygen concentration reference value based on the first preset relationship;

[0110] The first preset relationship is:

[0111]

[0112] Wherein, S is the preset reference value of dissolved oxygen concentration, S0 is the preset steady-state reference value, Δt is the time difference between the end time of the current control cycle and the initial time of starting aeration, and T1 is the preset transition time;

[0113] If not, the corresponding preset dissolved oxygen concentration reference value is determined to be a preset steady-state reference value.

[0114] In this embodiment, the inventor further considers that in the actual control process, the overshoot of the dissolved oxygen concentration in the initial stage of aeration control is likely to be too large, resulting in system instability. This application introduces a transition strategy, that is, by changing the preset dissolved oxygen concentration reference value, the purpose of reducing the overshoot of the dissolved oxygen concentration in the initial stage of aeration control is achieved, and the implementation method is simple and reliable. It should be noted that the preset dissolved oxygen concentration reference value and the preset transition time range are set according to actual needs, and the initial time of starting aeration can be the initial time of the first control cycle.

[0115] For details, please refer to Figure 3 , the figure gives a curve of water inflow changing with time, where the horizontal axis is time, the unit is day, and the vertical axis is water inflow Q, the unit is m 3 / day; it can be seen that the water intake fluctuates;

[0116] Please refer to Figure 4a , Figure 4a It is a curve diagram of the change of dissolved oxygen concentration over time in the prior art, wherein the horizontal axis is time, the unit is day, and the vertical axis is DO (Dissolved Oxygen, dissolved oxygen concentration), the unit is mg / L, and the control method of the prior art here does not introduce the feedforward control amount of the water inlet described in this application, nor does it introduce the regulation of the overshoot of the dissolved oxygen concentration that may exist in the initial stage of aeration control, that is, Figure 4a As mentioned in the above, “no transition process is introduced”, it can be clearly seen that Figure 4a There is a large overshoot in the initial stage;

[0117] Please refer to Figure 4b , Figure 4b Another graph of dissolved oxygen concentration changing with time in the prior art, wherein the horizontal axis is time in days, and the vertical axis is DO in mg / L, corresponding to Figure 3 It can be clearly seen that when the water inflow fluctuates, the dissolved oxygen concentration also fluctuates greatly in the control method of the prior art;

[0118] As a comparison, Figure 5A curve chart of the change of dissolved oxygen concentration over time provided by the present application is shown, wherein the horizontal axis is time, the unit is day, and the vertical axis is DO, the unit is mg / L. It can be clearly seen that the dissolved oxygen concentration control method of the biological aeration tank provided by the present application can not only eliminate the problem of overshoot of dissolved oxygen concentration in the initial stage of aeration control, but also resist the influence of water inlet fluctuation on dissolved oxygen concentration, so that the practicality, reliability and accuracy of the method provided by the present application are strongly proved. In summary, it can be seen that the method provided by the present application has high control accuracy and the control is smooth and without overshoot in the startup stage.

[0119] As a preferred embodiment, the output term of the fuzzy controller includes a first coefficient k1 and a second coefficient k2;

[0120] The desired air volume is determined based on the output items and deviation sequence of the fuzzy controller, including:

[0121] Determining a dissolved oxygen concentration equivalent deviation based on a second preset relationship and a deviation sequence;

[0122] The second preset relationship is:

[0123]

[0124] in, is the equivalent deviation of dissolved oxygen concentration, e i is the i-th deviation data, ω i is the weighting coefficient corresponding to the i-th deviation data;

[0125] Processing the deviation sequence based on a third preset relationship to obtain integral item data;

[0126] The third preset relationship is:

[0127]

[0128] Among them, esum is the integral term data, ΔT is the current control cycle interval;

[0129] Determine the desired air volume based on the first coefficient k1 and the second coefficient k2, the dissolved oxygen concentration equivalent deviation, the integral term data and the fourth preset relationship;

[0130] The fourth preset relationship is:

[0131]

[0132] Where F is the desired air volume.

[0133] In this embodiment, how to determine the desired air volume based on the output item of the fuzzy controller and the deviation sequence is given. The specific steps have been explained above and will not be repeated here. It should be noted that the first coefficient k1 here is essentially equivalent to the proportional coefficient, and the second coefficient k2 is essentially equivalent to the integral coefficient. It should be noted that the current control cycle interval is the duration of the current control cycle. For example, the current control cycle corresponds to the start time 15:00 and the end time 15:15, then ΔT corresponds to the time difference between the end time and the start time.

[0134] It can be seen that the above implementation is simple and reliable, and is convenient for subsequent maintenance and operation.

[0135] As a preferred embodiment, after determining the equivalent deviation of dissolved oxygen concentration based on the second preset relationship and the deviation sequence, the method further includes:

[0136] Determine the equivalent deviation difference value in the current control cycle based on the deviation sequence of the current control cycle and the deviation sequence of the previous control cycle;

[0137] Determine whether the dissolved oxygen concentration equivalent deviation and the corresponding equivalent deviation difference value satisfy the following fifth preset relationship:

[0138]

[0139] Among them, sign represents the sign function, de represents the equivalent deviation difference value;

[0140] If not, proceed to the step of processing the deviation sequence based on the third preset relationship to obtain integral item data;

[0141] If so, determining the desired air volume of the current control cycle based on the sixth preset relationship, the dissolved oxygen concentration equivalent deviation, and the desired air volume of the previous control cycle;

[0142] The sixth preset relationship is:

[0143]

[0144] Wherein, k3 is the third coefficient, F is the expected air volume of the current control cycle, and F0 is the expected air volume of the previous control cycle.

[0145] In this embodiment, the inventor further considers that the dissolved oxygen concentration control of the aeration tank is a complex nonlinear control problem, and the difficulty lies in the nonlinearity of the oxygen supply process; the oxygen consumption of the activated sludge microorganisms in the aeration tank is dynamically fluctuating, and is subject to many interference factors, such as water intake, etc.; and there is a high probability of time lag in the control process. In order to solve the above-mentioned time lag problem, the inventor provides the above strategy, that is, to determine whether the equivalent deviation of the dissolved oxygen concentration and the corresponding equivalent deviation difference value satisfy the fifth preset relationship, and to perform subsequent control according to the judgment result. It should be noted that the third coefficient k3 here can be a specific value or a pre-set relationship, which is not particularly limited here and is set according to actual needs.

[0146] Specifically, here, for the step of determining the equivalent deviation difference value in the current control cycle based on the deviation sequence of the current control cycle and the deviation sequence of the previous control cycle, a specific implementation method is given:

[0147] The first deviation data in the deviation sequence of the current control cycle is used to subtract the last deviation data in the deviation sequence of the previous control cycle, and the result is used as the first equivalent deviation difference data;

[0148] Using the j-th deviation data in the deviation sequence of the current control cycle, subtract the j-1-th deviation data in the deviation sequence of the current control cycle, and the result is used as the j-th equivalent deviation difference data, where 2≤j≤N and j is an integer;

[0149] Thus, an equivalent deviation difference sequence consisting of N equivalent deviation difference data is obtained;

[0150] The equivalent deviation difference value can be determined based on the following relationship and the equivalent deviation difference sequence:

[0151]

[0152] Among them, θ j is the weighted weight corresponding to the jth equivalent deviation difference data, de j is the jth equivalent deviation differential data, and de is the equivalent deviation differential value.

[0153] It can be seen that the setting of the above execution logic can reliably reduce the influence of system time delay, further ensuring the accuracy and stability of the system.

[0154] As a preferred embodiment, it also includes:

[0155] Get the actual output air volume to the aeration tank during the current control cycle;

[0156] Determine the dilution rate based on the water inflow and the effective volume of the aeration tank;

[0157] Based on the dissolved oxygen concentration data sequence, the actual output air volume, the dilution rate, the sludge return ratio of the aeration tank and the pre-designed oxygen consumption rate calibration model, the oxygen consumption rate of the aeration tank for the next control cycle is determined and stored.

[0158] In this embodiment, a reliable online calibration method for oxygen consumption rate is further provided, which saves the extra cost of setting up a respiratory rate meter and is convenient for practical application. The specific implementation method is as described above and will not be repeated here. It should be noted that the instrument used to obtain the actual output air volume can be an air flow meter; the specific method for determining the dilution rate can be: divide the water intake by the effective volume, and the result obtained is the dilution rate of the biological aeration tank.

[0159] As a preferred embodiment, the dissolved oxygen concentration data sequence includes N dissolved oxygen concentration data, where N is an integer greater than 1;

[0160] Based on the dissolved oxygen concentration data sequence, actual output air volume, dilution rate, sludge return ratio of the aeration tank and the pre-designed oxygen consumption rate calibration model, the oxygen consumption rate of the aeration tank for the next control cycle is determined and stored, including:

[0161] Determine a theoretical dissolved oxygen concentration data sequence with oxygen consumption rate as a parameter to be determined based on the seventh preset relationship;

[0162] The seventh preset relationship is:

[0163] S(k+1)=f(U)S sat ΔT m +[1-q(1+r)ΔT m -f(U)ΔT m ]S(k)-OURΔT m

[0164] Where, S(k+1) is the k+1th theoretical dissolved oxygen concentration data in the theoretical dissolved oxygen concentration data sequence, and S(k) is the kth theoretical dissolved oxygen concentration data, 1≤k≤N-1 and k is an integer; f(U) is the oxygen transfer coefficient corresponding to the actual output air volume in the current control period, S sat is the saturated dissolved oxygen concentration in the aeration tank, q is the dilution rate, r is the sludge return ratio, ΔT m is the time difference between the sampling time corresponding to the k+1th dissolved oxygen concentration data and the sampling time corresponding to the kth dissolved oxygen concentration data;

[0165] And wherein, the first dissolved oxygen concentration data in the current control cycle is used as the first theoretical dissolved oxygen concentration data;

[0166] Based on the dissolved oxygen concentration data series A = {ai}、Theoretical dissolved oxygen concentration data series B={b i}, establish the objective function with oxygen consumption rate as the decision variable;

[0167] The objective function is:

[0168]

[0169] The decision variable of the objective function is the oxygen consumption rate OUR, and the constraints of the objective function are:

[0170] OUR∈[OUR min ,OUR max ]

[0171] Among them, OUR min is the lower limit of oxygen consumption rate OUR, OUR max is the upper limit of the oxygen consumption rate OUR;

[0172] The objective function is optimized to determine the oxygen consumption rate of the aeration tank.

[0173] In this embodiment, how to determine the oxygen consumption rate of the aeration tank is given. The specific process has been explained above and will not be repeated here. It should be noted that the lower limit of the oxygen consumption rate OUR and the upper limit of the oxygen consumption rate OUR are set according to actual needs, and the optimization solution method for the objective function includes but is not limited to the greedy optimization algorithm and various intelligent optimization algorithms, which are not particularly limited here.

[0174] It should be noted that, considering the linear relationship between the oxygen transfer coefficient and the actual output air volume, the oxygen transfer coefficient here, as a numerical value, can be obtained by direct measurement or by calibrating a function corresponding to the actual output air volume.

[0175] For details, please refer to Figure 6 , Figure 6 The present invention provides a graph showing the change of oxygen consumption rate over time, wherein the horizontal axis is time in days, and the vertical axis is the oxygen consumption rate. In order to better demonstrate the effectiveness of the oxygen consumption rate calibration method provided in the present application, the oxygen consumption rate (actual OUR) measured by the respirometer is represented by a solid line, and the oxygen consumption rate (estimated OUR) determined by the method provided in the present application is represented by a dotted line, which once again proves the effectiveness of the method provided in the present application and eliminates the additional cost of setting up a respirometer.

[0176] Please refer to Figure 7 , Figure 7 The present invention provides a schematic structural diagram of a biological aeration tank dissolved oxygen concentration control system.

[0177] The biological aeration tank dissolved oxygen concentration control system includes:

[0178] The first data acquisition unit 21 is used to acquire the water inflow of the aeration tank and the dissolved oxygen concentration data sequence of the aeration tank in the current control period;

[0179] The desired air volume calculation unit 22 is used to determine the desired air volume based on the water inflow, dissolved oxygen concentration data sequence and a pre-designed fuzzy controller;

[0180] The air volume tracking unit 23 is used to adjust the opening of the valve according to the expected air volume to ensure that the actual output air volume output to the aeration tank is consistent with the expected air volume.

[0181] For an introduction to the biological aeration tank dissolved oxygen concentration control system provided in the present invention, please refer to the above-mentioned embodiment of the biological aeration tank dissolved oxygen concentration control method, which will not be described in detail here.

[0182] As a preferred embodiment, it also includes:

[0183] A second data acquisition unit is used to acquire the actual output air volume output to the aeration tank during the current control period;

[0184] A dilution rate determination unit, used for determining the dilution rate according to the water inflow and the effective volume of the aeration tank;

[0185] The oxygen consumption rate calibration unit is used to determine and store the oxygen consumption rate of the aeration tank for the next control cycle based on the dissolved oxygen concentration data sequence, the actual output air volume, the dilution rate, the sludge return ratio of the aeration tank and the pre-designed oxygen consumption rate calibration model.

[0186] Please refer to Figure 8 , Figure 8 The present invention provides a schematic structural diagram of a biological aeration tank dissolved oxygen concentration control system.

[0187] The biological aeration tank dissolved oxygen concentration control device comprises:

[0188] A memory 31, used for storing computer programs;

[0189] The processor 32 is used to execute the steps of the method for controlling dissolved oxygen concentration in a biological aeration tank as described above.

[0190] For an introduction to the biological aeration tank dissolved oxygen concentration control device provided in the present invention, please refer to the embodiment of the biological aeration tank dissolved oxygen concentration control method described above, which will not be described in detail here.

[0191] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0192] Relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device that includes a series of elements includes not only those elements, but also other elements that are not explicitly listed, or also includes elements that are inherent to such process, method, article, or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or device that includes the element.

[0193] Professionals may further realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function.

[0194] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for controlling dissolved oxygen concentration in a biological aeration tank, characterized in that: include: Obtaining a data sequence of water inflow into an aeration tank and dissolved oxygen concentration in the aeration tank during a current control period; Determine the desired air volume based on the water inflow, the dissolved oxygen concentration data sequence and a pre-designed fuzzy controller; Adjusting the opening of the valve according to the desired air volume to ensure that the actual output air volume output to the aeration tank is consistent with the desired air volume; The dissolved oxygen concentration data sequence includes N dissolved oxygen concentration data, where N is an integer greater than 1; Determining the desired air volume based on the water inflow, the dissolved oxygen concentration data sequence and a pre-designed fuzzy controller includes: Subtracting each dissolved oxygen concentration data from a preset dissolved oxygen concentration reference value to obtain corresponding deviation data, each deviation data forming a deviation sequence, and the total number of the deviation data is N; Input the deviation sequence, the water inflow and the dissolved oxygen concentration data sequence as input items into a pre-designed fuzzy controller; Determining a desired air volume based on an output item of the fuzzy controller and the deviation sequence; The output term of the fuzzy controller includes a first coefficient k1 and a second coefficient k2; wherein the first coefficient is a proportional coefficient and the second coefficient is an integral coefficient; The fuzzy controller is used to fuzzify the deviation sequence, the water inflow and the dissolved oxygen concentration data sequence and perform fuzzy reasoning according to fuzzy reasoning rules, and defuzzify the results obtained by the fuzzy reasoning rules to obtain the output items of the fuzzy controller; Determining the desired air volume based on the output item of the fuzzy controller and the deviation sequence includes: Determining a dissolved oxygen concentration equivalent deviation based on a second preset relationship and the deviation sequence; The second preset relationship is: ； in, is the dissolved oxygen concentration equivalent deviation, is the i-th deviation data, is the weighting coefficient corresponding to the i-th deviation data; Processing the deviation sequence based on a third preset relationship to obtain integral item data; The third preset relationship is: ； in, is the integral item data, is the current control cycle interval; Determine the desired air volume based on the first coefficient k1 and the second coefficient k2, the dissolved oxygen concentration equivalent deviation, the integral term data and a fourth preset relationship; The fourth preset relationship is: ； Wherein, F is the desired air volume.

2. The method for controlling dissolved oxygen concentration in a biological aeration tank according to claim 1, characterized in that: Before deducting each of the dissolved oxygen concentration data from the preset dissolved oxygen concentration reference value, the method further includes: Determining whether the current control period is within a preset transition time range; If so, determining a corresponding preset dissolved oxygen concentration reference value based on the first preset relationship; The first preset relationship is: ； Wherein, S is the preset dissolved oxygen concentration reference value, is the preset steady-state reference value, is the time difference between the end time of the current control cycle and the initial time of starting aeration, is the preset transition duration; If not, the corresponding preset dissolved oxygen concentration reference value is determined to be the preset steady-state reference value.

3. The method for controlling dissolved oxygen concentration in a biological aeration tank according to claim 1, wherein: After determining the dissolved oxygen concentration equivalent deviation based on the second preset relationship and the deviation sequence, the method further includes: Determining an equivalent deviation difference value in the current control cycle based on the deviation sequence of the current control cycle and the deviation sequence of the previous control cycle; Determine whether the dissolved oxygen concentration equivalent deviation and the corresponding equivalent deviation difference value satisfy the following fifth preset relationship: ； in, represents the symbolic function, de represents the equivalent deviation difference value; If not, proceed to the step of processing the deviation sequence based on a third preset relationship to obtain integral item data; If so, determining the desired air volume of the current control cycle based on the sixth preset relationship, the dissolved oxygen concentration equivalent deviation and the desired air volume of the previous control cycle; The sixth preset relationship is: ； Among them, k3 is the third coefficient, F is the expected air volume of the current control cycle, and F0 is the expected air volume of the previous control cycle.

4. The method for controlling dissolved oxygen concentration in a biological aeration tank according to any one of claims 1 to 3, characterized in that: Also includes: Obtaining the actual output air volume output to the aeration tank during the current control cycle; Determining a dilution rate according to the water inflow and the effective volume of the aeration tank; Based on the dissolved oxygen concentration data sequence, the actual output air volume, the dilution rate, the sludge return ratio of the aeration tank and a pre-designed oxygen consumption rate calibration model, the oxygen consumption rate of the aeration tank in the next control cycle is determined and stored.

5. The method for controlling dissolved oxygen concentration in a biological aeration tank according to claim 4, characterized in that: The dissolved oxygen concentration data sequence includes N dissolved oxygen concentration data, where N is an integer greater than 1; Based on the dissolved oxygen concentration data sequence, the actual output air volume, the dilution rate, the sludge return ratio of the aeration tank and a pre-designed oxygen consumption rate calibration model, the oxygen consumption rate of the aeration tank in the next control cycle is determined and stored, including: Determine a theoretical dissolved oxygen concentration data sequence with oxygen consumption rate as a parameter to be determined based on the seventh preset relationship; The seventh preset relationship is: ； Wherein, S(k+1) is the k+1th theoretical dissolved oxygen concentration data in the theoretical dissolved oxygen concentration data sequence, and S(k) is the kth theoretical dissolved oxygen concentration data, 1≤k≤N-1 and k is an integer; f(U) is the oxygen transfer coefficient corresponding to the actual output air volume in the current control period, is the saturated dissolved oxygen concentration of the aeration tank, q is the dilution rate, r is the sludge return ratio, is the time difference between the sampling time corresponding to the k+1th dissolved oxygen concentration data and the sampling time corresponding to the kth dissolved oxygen concentration data; And wherein, the first dissolved oxygen concentration data in the current control period is used as the first theoretical dissolved oxygen concentration data; Based on the dissolved oxygen concentration data sequence A={a i }, the theoretical dissolved oxygen concentration data sequence B = {b i }, establishing an objective function with the oxygen consumption rate as a decision variable; The objective function is: ； The decision variable of the objective function is the oxygen consumption rate , and the constraint condition of the objective function is: ； in, The oxygen consumption rate The lower limit of the value of The oxygen consumption rate The upper limit of the value of ; The objective function is optimized and solved to determine the oxygen consumption rate of the aeration tank.

6. A biological aeration tank dissolved oxygen concentration control system, characterized in that: include: A first data acquisition unit, used to acquire a data sequence of water inflow into the aeration tank and dissolved oxygen concentration in the aeration tank during a current control period; A desired air volume calculation unit, used to determine the desired air volume based on the water inflow, the dissolved oxygen concentration data sequence and a pre-designed fuzzy controller; An air volume tracking unit, used to adjust the opening of the valve according to the desired air volume to ensure that the actual output air volume output to the aeration tank is consistent with the desired air volume; The dissolved oxygen concentration data sequence includes N dissolved oxygen concentration data, where N is an integer greater than 1; The desired air volume calculation unit is specifically used for: Subtracting each dissolved oxygen concentration data from a preset dissolved oxygen concentration reference value to obtain corresponding deviation data, each deviation data forming a deviation sequence, and the total number of the deviation data is N; Input the deviation sequence, the water inflow and the dissolved oxygen concentration data sequence as input items into a pre-designed fuzzy controller; Determining a desired air volume based on an output item of the fuzzy controller and the deviation sequence; The output term of the fuzzy controller includes a first coefficient k1 and a second coefficient k2; wherein the first coefficient is a proportional coefficient and the second coefficient is an integral coefficient; The fuzzy controller is used to fuzzify the deviation sequence, the water inflow and the dissolved oxygen concentration data sequence and perform fuzzy reasoning according to fuzzy reasoning rules, and defuzzify the results obtained by the fuzzy reasoning rules to obtain the output items of the fuzzy controller; Determining the desired air volume based on the output item of the fuzzy controller and the deviation sequence includes: Determining a dissolved oxygen concentration equivalent deviation based on a second preset relationship and the deviation sequence; The second preset relationship is: ； in, is the dissolved oxygen concentration equivalent deviation, is the i-th deviation data, is the weighting coefficient corresponding to the i-th deviation data; Processing the deviation sequence based on a third preset relationship to obtain integral item data; The third preset relationship is: ； in, is the integral item data, is the current control cycle interval; Determine the desired air volume based on the first coefficient k1 and the second coefficient k2, the dissolved oxygen concentration equivalent deviation, the integral term data and a fourth preset relationship; The fourth preset relationship is: ； Wherein, F is the desired air volume.

7. The biological aeration tank dissolved oxygen concentration control system according to claim 6, characterized in that: Also includes: A second data acquisition unit, used to acquire the actual output air volume output to the aeration tank during the current control period; a dilution rate determination unit, used to determine the dilution rate according to the water inflow and the effective volume of the aeration tank; The oxygen consumption rate calibration unit is used to determine and store the oxygen consumption rate of the aeration tank in the next control cycle based on the dissolved oxygen concentration data sequence, the actual output air volume, the dilution rate, the sludge return ratio of the aeration tank and a pre-designed oxygen consumption rate calibration model.

8. A biological aeration tank dissolved oxygen concentration control device, characterized in that: include: Memory for storing computer programs; A processor, used to execute the steps of the method for controlling dissolved oxygen concentration in a biological aeration tank as described in any one of claims 1 to 5.

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