Variable frequency pump frequency distribution method based on emulsion control system

Abstract

The invention discloses a variable frequency pump frequency distribution method based on an emulsion control system. The variable frequency pump frequency distribution method comprises the following steps that S1, emulsion pressure at a total outlet is detected in real time; s2, comparing the emulsion pressure at the total outlet with the target pressure; s3, in a comparison result, if the pressure is greater than the target pressure, turning to step S4, and if the pressure is less than the target pressure, turning to step S6; s4, comparing the pressure duration with the target time, entering a production class mode if the pressure duration is less than the target time, and entering a maintenance class mode if the pressure duration is greater than the target time; and S5, ending. S6, comparing the pressure duration with the target time, if the pressure duration is less than the target time, entering a production class mode, if the pressure duration is greater than the target time, judging whether the state is a loading state, and if the state is a non-loading state, ending; in a loading state, the pressure is continuously timed; s7, comparing the pressure duration with the target time, and if the pressure duration is less than the target time, entering an end state; if the time is longer than the target time, entering a production class mode and ending; and S8, returning to the step S1 after finishing.

Description

Technical Field

[0001] The invention relates to the field of coal mine emulsion pump control, and in particular to a frequency distribution method for a variable frequency pump based on an emulsion control system. Background Art

[0002] Emulsion pump stations play the role of providing hydraulic power source in coal mines, which is crucial to ensuring the normal production of coal mines. With the increase in the advancement speed of the working face support, the emulsion pump station needs to adapt to higher pressure and greater flow requirements.

[0003] With the rapid innovation of coal mines, more and more coal mines adopt the configuration of multiple emulsification frequency conversion pumps, and new frequency conversion methods are urgently needed to meet the operation of multiple emulsification frequency conversion pumps; and the existing emulsification pump frequency conversion adjustment method is mainly based on the extensive PID frequency modulation method, and its frequency modulation method is too simple and cannot meet the complex working environment requirements of coal mines. It is necessary to improve it. Summary of the invention

[0004] The purpose of the present invention is to solve the above problems and provide a frequency distribution method for a variable frequency pump based on an emulsion control system, so as to further improve the working efficiency and accuracy of the emulsion pump, greatly enhance the intelligence level and stability of the system, and also bring about significant energy-saving effects.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] A frequency distribution method for variable frequency pumps based on an emulsion control system, the emulsion control system comprising a total outlet for collecting emulsions of a main emulsion variable frequency pump, a secondary emulsion variable frequency pump and a spare emulsion variable frequency pump, and a pressure sensor arranged at the total outlet for measuring the emulsion pressure at the total outlet, the main emulsion variable frequency pump, the secondary emulsion variable frequency pump and the spare emulsion variable frequency pump are controlled by a solenoid valve and a frequency converter, and the pressure sensor, the solenoid valve and the frequency converter are connected to a PID controller;

[0007] The variable frequency pump frequency distribution method comprises the following steps:

[0008] S1, the emulsion control system starts working, the PID controller inputs the target pressure of the control, and the pressure sensor detects the emulsion pressure at the total outlet in real time;

[0009] S2, PID controller compares the emulsion pressure at the total outlet with the target pressure, calculates the parameters that need to be adjusted for the frequency converter and / or the solenoid valve according to the comparison result, and then adjusts the frequency converter or the solenoid valve to perform loading and unloading actions, thereby controlling the discharge of the main emulsification frequency conversion pump, the secondary emulsification frequency conversion pump and the standby emulsification frequency conversion pump, and the pressure control duration is timed during the adjustment period;

[0010] S3, in the comparison result of the emulsion pressure at the total outlet and the target pressure, if the emulsion pressure at the total outlet is greater than the target pressure, proceed to step S4; if the emulsion pressure at the total outlet is less than the target pressure, proceed to step S6;

[0011] S4, compare the pressure duration with the target time, if it is less than the target time, enter the production shift mode, if it is greater than the target time, enter the maintenance shift mode;

[0012] S5. After the emulsion control system enters the maintenance shift mode or the production shift mode, it ends;

[0013] S6. Compare the pressure duration with the target time. If it is less than the target time, enter the production shift mode. If it is greater than the target time, determine whether the main emulsification frequency conversion pump, the secondary emulsification frequency conversion pump and the standby emulsification frequency conversion pump are in a loaded state. If they are in a non-loaded state, end; if they are in a loaded state, the pressure duration is counted.

[0014] S7, compare the pressure duration with the target time, if it is less than the target time, enter the end state; if it is greater than the target time, enter the production shift mode and end;

[0015] S8. After completion, return to step S1 and repeat the above steps.

[0016] Furthermore, the output formula of the PID controller is:

[0017] output=Kp*error+Ki*integral+Kd*derivative;

[0018] Among them, error is the current error, integral is the integral of the error, derivative is the differential of the error; Kp is the proportional parameter, Ki is the integral parameter, and Kd is the derivative parameter.

[0019] Furthermore, in step S3, the PID controller adjusts the frequency of the frequency converter including the following steps:

[0020] S21, in the comparison result between the emulsion pressure at the total outlet and the target pressure, when the emulsion pressure at the total outlet is less than the target pressure, the PID controller increases the frequency of the frequency converter and performs frequency distribution; when the emulsion pressure at the total outlet is greater than the target pressure, the PID controller decreases the frequency of the frequency converter and performs frequency distribution;

[0021] S22, comparing the expected frequency with the maximum frequency of the emulsion control system; when the expected frequency is greater than the maximum frequency of the emulsion control system, the PID controller uses the frequency converter to make the main emulsion frequency conversion pump, the secondary emulsion frequency conversion pump, and the standby emulsion frequency conversion pump all run at the maximum frequency; when the expected frequency is less than the maximum frequency of the emulsion control system, proceed to the next step;

[0022] S23, comparing the expected frequency with the minimum frequency of the emulsion control system; when the expected frequency is less than the minimum frequency of the emulsion control system, the PID controller uses the frequency converter to make the main emulsion variable frequency pump, the secondary emulsion variable frequency pump, and the standby emulsion variable frequency pump all run at the minimum frequency; when the expected frequency is greater than the minimum frequency of the emulsion control system, proceed to the next step;

[0023] S24, PID controller uses the frequency converter to make the main emulsification frequency conversion pump run at the maximum frequency, the secondary emulsification frequency conversion pump run at the frequency modulation frequency, and the standby emulsification frequency conversion pump run at the minimum frequency.

[0024] Furthermore, the production shift mode refers to a mode in which an intermediate pressure value is set within the constant pressure range of the emulsion control system to achieve rapid frequency modulation; the maintenance shift mode refers to a mode in which two intermediate pressure values ​​are set within the constant pressure range of the emulsion control system to maintain the minimum pressure and the minimum frequency.

[0025] Furthermore, in the production shift mode, the maximum output parameter, the minimum output parameter, and the task cycle parameter of the PID controller are dynamically adjusted by the pressure fluctuation frequency, and the dynamic adjustment operation includes the following steps:

[0026] S91, the emulsion control system starts to work, and the emulsion pressure at the total outlet is detected in real time;

[0027] S92, capturing the rising edge and the falling edge of the pressure curve;

[0028] S93, during the pressure boosting stage, record the pressure value and time the pressure duration, and compare the pressure duration with the target time; if it is less than the target time, return to step S91; if it is greater than the target time, calculate the speed increase during the pressure boosting stage;

[0029] S94, during the pressure reduction phase, the pressure value is recorded and the pressure duration is timed, and the pressure duration is compared with the target time; if it is less than the target time, return to step S91; if it is greater than the target time, the pressure reduction phase speed increase calculation is performed;

[0030] S95. Predict the pressure fluctuation frequency within 1 minute by calculating the growth rate in the boost phase and the growth rate in the buck phase; when the pressure fluctuation frequency within 1 minute is greater than 20 times, increase the maximum output parameter of the PID controller by 5 Hz, decrease the minimum output parameter by 10 Hz, and increase the task cycle parameter by 0.1 s; when the pressure fluctuation frequency within 1 minute is less than 5 times, increase the maximum output parameter of the PID controller by 2 Hz, decrease the minimum output parameter by 4 Hz, and increase the task cycle parameter by 0.5 s; when the pressure fluctuation frequency within 1 minute is not less than 5 times and not more than 20 times, increase the maximum output parameter of the PID controller by 5 Hz, decrease the minimum output parameter by 10 Hz, and increase the task cycle parameter by 0.5 s.

[0031] Furthermore, the target time of the voltage boost phase is 250 ms; and the target time of the voltage drop phase is 50 ms.

[0032] Compared with the prior art, the present invention has the following advantages and positive effects:

[0033] The present invention proposes a frequency distribution method for a variable frequency pump based on an emulsion control system, which divides the emulsion control system into a maintenance shift mode or a production shift mode by comparing the pressure duration, target time and target pressure, thereby realizing different operational controls on the flow and pressure of the emulsion pump station, thereby meeting the changing needs of industrial production such as coal mines; and, the present invention adjusts the operating frequency of the emulsion variable frequency pump in real time by comparing the real-time system pressure with the target pressure, thereby improving the working efficiency and accuracy of the emulsion pump, ensuring the efficient and stable operation of the liquid supply system, and greatly improving the intelligence level and stability of the emulsion control system. At the same time, the present invention has a significant energy-saving effect through the precise control of the PID controller, providing a strong guarantee for coal enterprises to improve their economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be 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 paying creative labor.

[0035] Figure 1 This is the working principle diagram of the PID controller;

[0036] Figure 2 It is the pressure curve diagram of the maintenance shift mode and the production shift mode;

[0037] Figure 3 A flow chart for distinguishing working modes;

[0038] Figure 4 This is a curve diagram of the maintenance class mode;

[0039] Figure 5 It is a curve diagram of the production shift mode;

[0040] Figure 6 This is the parameter adjustment flow chart of the PID controller in the production shift mode;

[0041] Figure 7 It is a working schematic diagram of an emulsification variable frequency pump in the prior art;

[0042] Figure 8 It is the working logic diagram of multiple emulsification variable frequency pumps;

[0043] Fig. 9 This is the frequency modulation flow chart of multiple emulsification variable frequency pumps. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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, any modifications, equivalent substitutions, improvements, etc., should be included in the protection scope of the present invention.

[0045] At present, the frequency conversion regulation of coal mine emulsification pumps mainly adopts the widely used PID regulation method, but it is not applicable to the scenario of frequency conversion control of coal mine emulsification pumps. The problem of rapid mutation of the target emulsification pump pressure in the whole frequency modulation process cannot be solved by the PID frequency modulation in the conventional sense. The present invention is based on the widely used PID algorithm, and aims at the special operating environment of coal mine emulsification pumps to form a new parameter setting method and a new segmented control PID algorithm, which further improves the working efficiency and accuracy of the emulsification pump.

[0046] Before explaining the technical solution, some related concepts are introduced first:

[0047] Emulsion pump pressure output related: solenoid valve loading and unloading action, frequency converter to achieve frequency regulation. The solenoid valve is responsible for controlling the emulsion pump's liquid output (loading: liquid hits the working surface, unloading: liquid returns to the liquid tank), the frequency converter controls the emulsion pump's output frequency, and then changes the emulsion pump's flow rate to control the emulsion pump's liquid output (different frequencies represent different flow rates); as shown in Table 1;

[0048] Table 1

[0049]

[0050] 1. PID control

[0051] PID control is a regulation method that combines three control modes: proportional, integral, and derivative, and is used to accurately control the behavior of the system.

[0052] The following are the core points of PID control:

[0053] 1. Proportional control (P): It adjusts the control output according to the current error so that the system responds quickly and approaches the target value. The proportional parameter Kp determines the sensitivity and reaction intensity to the current error. The larger the Kp, the faster the system reacts to the error, but too large a Kp may cause overshoot or oscillation.

[0054] 2. Integral control (I): The integral term is adjusted according to the system's error accumulation over a period of time to eliminate long-standing deviations and achieve steady-state error-free control. The integral parameter Ki determines the degree of response to historical error accumulation and helps to reduce or eliminate steady-state errors.

[0055] 3. Differential control (D): predict future trends by detecting the rate of change of the error and make corresponding adjustments to reduce system oscillation and improve system stability. The differential parameter Kd affects the system's responsiveness to the rate of error change.

[0056] 4. Maximum output (yMax): The maximum adjustment step of the PID controller, which ensures timely response of frequency increase by dynamically adjusting the maximum output.

[0057] 5. Minimum output (yMin): The minimum adjustment step of the PID controller. It dynamically adjusts the minimum output to ensure timely response to frequency reduction.

[0058] 6. Task Cycle (taskCyc): The task cycle of PID control is to dynamically adjust the task cycle to meet the rapid changes in pressure.

[0059] Formula expression: The output of the PID controller is given by the following mathematical formula: output = Kp*error+Ki*integral+Kd*derivative, where error is the current error, integral is the integral of the error, and derivative is the differential of the error. The setting of Kp, Ki and Kd parameters in the variable frequency regulation mode of the emulsion system is no different from the widespread PID parameter setting. The biggest difference in this example lies in the setting of the three newly added output parameters yMax, yMin and taskCyc. In this embodiment, for the variable frequency motor of the emulsification pump and the special operating environment of the coal mine, it is necessary to adjust the maximum output parameter, the minimum output parameter and the task cycle in real time to meet the complex and special operating environment of the coal mine, such as Figure 1 shown.

[0060] 2. Parameter Setting

[0061] The purpose of the emulsion control system is to stabilize the pressure of the pump station within a range. Different control strategies are adopted for the production team and the maintenance team, so that the pump can not only meet the requirements of rapid response of the production team, but also meet the requirements of energy saving and consumption reduction of the maintenance team.

[0062] 1. Mode differentiation

[0063] like Figure 2 As shown in the figure, the pressure action curve of the emulsification pump during the liquid supply process is analyzed, the characteristic sample values ​​are extracted, and the working mode is judged based on the pressure action curve of the emulsification pump. Figure 3 As shown, the distinguishing process is as follows;

[0064] S1, the emulsion control system starts working, the PID controller inputs the target pressure of the control, and the pressure sensor detects the emulsion pressure at the total outlet in real time;

[0065] S2, PID controller compares the emulsion pressure at the total outlet with the target pressure, calculates the parameters that need to be adjusted for the frequency converter and / or the solenoid valve according to the comparison result, and then adjusts the frequency converter or the solenoid valve to perform loading and unloading actions, thereby controlling the discharge of the main emulsification frequency conversion pump, the secondary emulsification frequency conversion pump and the standby emulsification frequency conversion pump, and the pressure control duration is timed during the adjustment period;

[0066] S3, in the comparison result of the emulsion pressure at the total outlet and the target pressure, if the emulsion pressure at the total outlet is greater than the target pressure, proceed to step S4; if the emulsion pressure at the total outlet is less than the target pressure, proceed to step S6;

[0067] S4, compare the pressure duration with the target time, if it is less than the target time, enter the production shift mode, if it is greater than the target time, enter the maintenance shift mode;

[0068] S5. After the emulsion control system enters the maintenance shift mode or the production shift mode, it ends;

[0069] S6. Compare the pressure duration with the target time. If it is less than the target time, enter the production shift mode. If it is greater than the target time, determine whether the main emulsification frequency conversion pump, the secondary emulsification frequency conversion pump and the standby emulsification frequency conversion pump are in a loaded state. If they are in a non-loaded state, end; if they are in a loaded state, the pressure duration is counted.

[0070] S7, compare the pressure duration with the target time, if it is less than the target time, enter the end state; if it is greater than the target time, enter the production shift mode and end;

[0071] S8. After completion, return to step S1 and repeat the above steps.

[0072] 2. Maintenance class mode

[0073] In the maintenance shift, the amount of liquid used is small, and the pump station only needs to maintain the necessary pressure and the lowest operating speed. Taking the constant pressure range of 25-30Mpa as an example, two intermediate pressures can be set at this time, one is 28Mpa and the other is 25.5Mpa, and the minimum frequency of the inverter can be reduced to 20Hz. Since the pressure reduction rate of the production shift is very slow, when the pressure drops to 25.5Mpa, the frequency increase can also meet the requirements; its pressure change curve is as follows Figure 4 As shown, the adjustment process is shown in Table 2;

[0074] Table 2

[0075]

[0076] 3. Production shift mode

[0077] The production class is mainly based on rapid response. Taking the constant pressure range of 25-30Mpa as an example, an intermediate pressure of 28Mpa can be set, and the minimum frequency of the inverter is set to 30Hz; the pressure change curve is as follows Figure 5 The adjustment process is shown in Table 3;

[0078] Table 3

[0079]

[0080] In order to solve the pressure fluctuations of different frequencies caused by inconsistent fluid conditions in production shifts and to ensure the smoothness of the frequency setting of the inverter, it is necessary to dynamically adjust the maximum output, minimum output and task cycle of the boost and buck stages, such as Figure 6 As shown, the processing flow is as follows:

[0081] S91, the emulsion control system starts to work, and the emulsion pressure at the total outlet is detected in real time;

[0082] S92, capturing the rising edge and the falling edge of the pressure curve;

[0083] S93, in the pressure boosting stage, record the pressure value and time the pressure duration, and compare the pressure duration with the target time 250ms; if it is less than the target time 250ms, return to step S91; if it is greater than the target time 250ms, calculate the speed increase in the pressure boosting stage;

[0084] S94, in the pressure reduction stage, record the pressure value and time the pressure duration, and compare the pressure duration with the target time of 50ms; if it is less than the target time of 50ms, return to step S91; if it is greater than the target time of 50ms, calculate the speed increase of the pressure reduction stage;

[0085] S95. Predict the pressure fluctuation frequency within 1 minute by calculating the growth rate in the boost phase and the growth rate in the buck phase; when the pressure fluctuation frequency within 1 minute is greater than 20 times, increase the maximum output parameter of the PID controller by 5 Hz, decrease the minimum output parameter by 10 Hz, and increase the task cycle parameter by 0.1 s; when the pressure fluctuation frequency within 1 minute is less than 5 times, increase the maximum output parameter of the PID controller by 2 Hz, decrease the minimum output parameter by 4 Hz, and increase the task cycle parameter by 0.5 s; when the pressure fluctuation frequency within 1 minute is not less than 5 times and not more than 20 times, increase the maximum output parameter of the PID controller by 5 Hz, decrease the minimum output parameter by 10 Hz, and increase the task cycle parameter by 0.5 s.

[0086] 3. Frequency calculation and allocation

[0087] The frequency regulation of emulsification pumps usually adopts a mainstream configuration, that is, multiple emulsification variable frequency pumps running at a fixed frequency are combined with a variable frequency emulsification pump. However, when it comes to the configuration of multiple emulsification variable frequency pumps, the regulation method of a single variable frequency pump is still used, which leads to a lack of coordination between multiple variable frequency pumps in the case of rapid frequency regulation, thus causing pressure fluctuation problems, such as Figure 7 Therefore, the existing system needs a new frequency adjustment method to better manage the frequencies of multiple emulsification variable frequency pumps and ensure the stability and efficiency of the production process. This embodiment provides a new adjustment method, such as Figure 8 As shown;

[0088] The basis of frequency allocation is to automatically define the variable frequency pump as the main pump, secondary pump and standby pump according to the startup logic sequence. When allocating frequencies to multiple emulsification variable frequency pumps, the remaining frequencies are secondary allocated according to the logic priority of main-secondary-standby while ensuring the minimum operating frequency of each pump. For example Fig. 9 As shown, the specific process is as follows:

[0089] S21, start;

[0090] S22, manual pump start;

[0091] S23, obtaining the primary and secondary order of each pump;

[0092] S24, real-time detection of total outlet pressure;

[0093] S25. Compare the pressure ranges of each pump;

[0094] S26. When the pressure range of each pump is less than the minimum threshold, the loading solenoid valve of the emulsification pump is opened; when the pressure range of each pump is greater than the minimum threshold, the unloading solenoid valve of the emulsification pump is opened;

[0095] S27, judging whether there is a variable frequency pump in each pump, if there is no variable frequency pump, returning to step S34; if there is a variable frequency pump, comparing the total outlet pressure with the target pressure;

[0096] S28, in the comparison result between the emulsion pressure at the total outlet and the target pressure, when the emulsion pressure at the total outlet is less than the target pressure, the PID controller increases the frequency of the frequency converter and performs frequency allocation; when the emulsion pressure at the total outlet is greater than the target pressure, the PID controller decreases the frequency of the frequency converter and performs frequency allocation;

[0097] S29, comparing the expected frequency with the maximum frequency of the emulsion control system; when the expected frequency is greater than the maximum frequency of the emulsion control system, the PID controller uses the frequency converter to make the main emulsion frequency conversion pump, the secondary emulsion frequency conversion pump, and the standby emulsion frequency conversion pump all run at the maximum frequency; when the expected frequency is less than the maximum frequency of the emulsion control system, proceed to the next step;

[0098] S210, comparing the expected frequency with the minimum frequency of the emulsion control system; when the expected frequency is less than the minimum frequency of the emulsion control system, the PID controller uses the frequency converter to make the main emulsion variable frequency pump, the secondary emulsion variable frequency pump, and the standby emulsion variable frequency pump all run at the minimum frequency; when the expected frequency is greater than the minimum frequency of the emulsion control system, proceed to the next step;

[0099] S211, PID controller uses the frequency converter to make the main emulsification frequency conversion pump run at the maximum frequency, the secondary emulsification frequency conversion pump run at the frequency modulation frequency, and the standby emulsification frequency conversion pump run at the minimum frequency.

[0100] The present invention proposes a frequency distribution method for a variable frequency pump based on an emulsion control system, which divides the emulsion control system into a maintenance shift mode or a production shift mode by comparing the pressure duration, target time and target pressure, thereby realizing different operational controls on the flow and pressure of the emulsion pump station, thereby meeting the changing needs of industrial production such as coal mines; and, the present invention adjusts the operating frequency of the emulsion variable frequency pump in real time by comparing the real-time system pressure with the target pressure, thereby improving the working efficiency and accuracy of the emulsion pump, ensuring the efficient and stable operation of the liquid supply system, and greatly improving the intelligence level and stability of the emulsion control system. At the same time, the present invention has a significant energy-saving effect through the precise control of the PID controller, providing a strong guarantee for coal enterprises to improve their economic benefits.

Claims

1. A frequency distribution method for a variable frequency pump based on an emulsion control system, characterized in that: The emulsion control system comprises a total outlet for collecting emulsions from the main emulsion variable frequency pump, the secondary emulsion variable frequency pump and the standby emulsion variable frequency pump, and a pressure sensor arranged at the total outlet for measuring the pressure of the emulsion at the total outlet. The main emulsion variable frequency pump, the secondary emulsion variable frequency pump and the standby emulsion variable frequency pump are controlled by a solenoid valve and a frequency converter, and the pressure sensor, the solenoid valve and the frequency converter are connected to a PID controller; The variable frequency pump frequency distribution method comprises the following steps: S1, the emulsion control system starts working, the PID controller inputs the target pressure of the control, and the pressure sensor detects the emulsion pressure at the total outlet in real time; S2, PID controller compares the emulsion pressure at the total outlet with the target pressure, calculates the parameters that need to be adjusted for the frequency converter and / or the solenoid valve according to the comparison result, and then adjusts the frequency converter or the solenoid valve to perform loading and unloading actions, thereby controlling the discharge of the main emulsification frequency conversion pump, the secondary emulsification frequency conversion pump and the standby emulsification frequency conversion pump, and the pressure control duration is timed during the adjustment period; S3, in the comparison result of the emulsion pressure at the total outlet and the target pressure, if the emulsion pressure at the total outlet is greater than the target pressure, proceed to step S4; if the emulsion pressure at the total outlet is less than the target pressure, proceed to step S6; S4, compare the pressure duration with the target time, if it is less than the target time, enter the production shift mode, if it is greater than the target time, enter the maintenance shift mode; S5. After the emulsion control system enters the maintenance shift mode or the production shift mode, it ends; S6. Compare the pressure duration with the target time. If it is less than the target time, enter the production shift mode. If it is greater than the target time, determine whether the main emulsification frequency conversion pump, the secondary emulsification frequency conversion pump and the standby emulsification frequency conversion pump are in a loaded state. If they are in a non-loaded state, end; if they are in a loaded state, the pressure duration is counted. S7, compare the pressure duration with the target time, if it is less than the target time, enter the end state; if it is greater than the target time, enter the production shift mode and end; S8. After completion, return to step S1 and repeat the above steps.

2. The frequency distribution method of the variable frequency pump based on the emulsion control system according to claim 1, characterized in that: The output formula of the PID controller is: output=Kp*error+Ki*integral+Kd*derivative; Among them, error is the current error, integral is the integral of the error, derivative is the differential of the error; Kp is the proportional parameter, Ki is the integral parameter, and Kd is the derivative parameter.

3. The frequency distribution method of the variable frequency pump based on the emulsion control system according to claim 2, characterized in that: In step S2, the PID controller adjusts the frequency of the frequency converter, including the following steps: S21, in the comparison result between the emulsion pressure at the total outlet and the target pressure, when the emulsion pressure at the total outlet is less than the target pressure, the PID controller increases the frequency of the frequency converter and performs frequency distribution; when the emulsion pressure at the total outlet is greater than the target pressure, the PID controller decreases the frequency of the frequency converter and performs frequency distribution; S22, comparing the expected frequency with the maximum frequency of the emulsion control system; when the expected frequency is greater than the maximum frequency of the emulsion control system, the PID controller uses the frequency converter to make the main emulsion frequency conversion pump, the secondary emulsion frequency conversion pump, and the standby emulsion frequency conversion pump all run at the maximum frequency; when the expected frequency is less than the maximum frequency of the emulsion control system, proceed to the next step; S23, comparing the expected frequency with the minimum frequency of the emulsion control system; when the expected frequency is less than the minimum frequency of the emulsion control system, the PID controller uses the frequency converter to make the main emulsion variable frequency pump, the secondary emulsion variable frequency pump, and the standby emulsion variable frequency pump all run at the minimum frequency; when the expected frequency is greater than the minimum frequency of the emulsion control system, proceed to the next step; S24, PID controller uses the frequency converter to make the main emulsification frequency conversion pump run at the maximum frequency, the secondary emulsification frequency conversion pump run at the frequency modulation frequency, and the standby emulsification frequency conversion pump run at the minimum frequency.

4. The frequency distribution method of the variable frequency pump based on the emulsion control system according to claim 3, characterized in that: The production shift mode refers to a mode in which an intermediate pressure value is set within the constant pressure range of the emulsion control system to achieve rapid frequency modulation; the maintenance shift mode refers to a mode in which two intermediate pressure values ​​are set within the constant pressure range of the emulsion control system to maintain the minimum pressure and the minimum frequency.

5. The frequency distribution method of the variable frequency pump based on the emulsion control system according to claim 4, characterized in that: In the production shift mode, the maximum output parameter, the minimum output parameter, and the task cycle parameter of the PID controller are dynamically adjusted by the pressure fluctuation frequency, and the dynamic adjustment operation includes the following steps: S91, the emulsion control system starts to work, and the emulsion pressure at the total outlet is detected in real time; S92, capturing the rising edge and the falling edge of the pressure curve; S93, during the pressure boosting stage, record the pressure value and time the pressure duration, and compare the pressure duration with the target time; if it is less than the target time, return to step S91; if it is greater than the target time, calculate the speed increase during the pressure boosting stage; S94, during the pressure reduction phase, the pressure value is recorded and the pressure duration is timed, and the pressure duration is compared with the target time; if it is less than the target time, return to step S91; if it is greater than the target time, the pressure reduction phase speed increase calculation is performed; S95. Predict the pressure fluctuation frequency within 1 minute by calculating the growth rate in the boost phase and the growth rate in the buck phase; when the pressure fluctuation frequency within 1 minute is greater than 20 times, increase the maximum output parameter of the PID controller by 5 Hz, decrease the minimum output parameter by 10 Hz, and increase the task cycle parameter by 0.1 s; when the pressure fluctuation frequency within 1 minute is less than 5 times, increase the maximum output parameter of the PID controller by 2 Hz, decrease the minimum output parameter by 4 Hz, and increase the task cycle parameter by 0.5 s; when the pressure fluctuation frequency within 1 minute is not less than 5 times and not more than 20 times, increase the maximum output parameter of the PID controller by 5 Hz, decrease the minimum output parameter by 10 Hz, and increase the task cycle parameter by 0.5 s.

6. The frequency distribution method of the variable frequency pump based on the emulsion control system according to claim 5, characterized in that: The target time of the voltage step-up phase is 250 ms; the target time of the voltage step-down phase is 50 ms.

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