Intelligent control method for temperature control, pressure control and motor life loss management of cooling circulating water unit

Abstract

The invention provides an intelligent control method for temperature control, pressure control and motor life loss management of a cooling circulating water unit, which is applied to a manufacturing workshop adopting cooling circulating water for material and equipment cooling work, and directly analyzes the water supply pressure and the return water temperature of a workshop cooling circulating water system through a control module written by an STL language in a PLC. The target threshold value of the automatic adjustment control system is determined, and sampling filtering is realized through a PID adjustment algorithm of the single-path closed-loop control system, so that the liquid supply pump and the cooling fan in the cooling circulating water system are accurately and stably controlled, and finally, the workshop production demand conditions are met. The method solves the problems that in industrial production, real-time pressure supply of circulating water is insufficient, and the temperature cannot meet the cooling condition in real time, meanwhile, the operation time of each liquid supply pump and the cooling fan in the system is scientifically distributed, the risk of equipment abrasion is effectively reduced, the intelligent degree of industrial production is improved, and the production cost is reduced. And the reliability and the stability of production are improved.

Description

Technical Field

[0001] The present invention belongs to the field of intelligent control of production workshops, and specifically relates to an intelligent control method for temperature control, pressure control, and motor life loss management of a cooling circulating water unit. Background Art

[0002] Nowadays, in the process of industrial production in the production workshop, there are many processes that require cooling circulating water units to cool equipment, materials, liquid medicines, etc., such as precipitation, crystallization, insulation, condensation, etc. In these production processes, operators need to control the water supply pressure in the water supply link of the cooling circulating water unit. If the water supply pressure is too high, the pressure of the circulating pipeline may exceed the pressure it can withstand, resulting in cracks in the circulating water pipeline or even pipeline bursting; operators also need to control the return water temperature in the cooling circulating water unit. If the return water temperature exceeds the maximum temperature required by the production process, processes such as crystallization, precipitation, and condensation cannot be completed. If the return water temperature is too low, it means that the cooling circulating water is working beyond demand at this time, causing serious energy waste, which may lead to product quality not meeting expectations; operators and mechanics also need to control the use time of equipment in the system. If a delivery pump or refrigeration fan in the unit maintains a working state for a long time, it may reduce the working life of the equipment.

[0003] At present, most production workshops use manual control of cooling water supply pressure and return water temperature in the working process of cooling water circulation system. Through the system water supply pressure display, the operator manually adjusts the frequency converter to adjust the frequency and speed of a certain working delivery pump, and observes the return water temperature display in the cooling water circulation system, and manually turns on or off one or several cooling fans according to the feedback. This method has many defects: (1) The operator needs to manually adjust the motor frequency converter, which is usually not able to accurately adjust to the appropriate frequency to stabilize the system water supply pressure at the expected value; (2) The operator needs to adjust the number of cooling fans to be turned on according to the cooling fan temperature feedback from the system. Due to the large lag in the temperature adjustment ratio, overshoot often occurs during the manual operation of the operator, and the temperature cannot be adjusted in time to maintain the normal expected value; (3) Single motor equipment is often overused during manual operation. Summary of the invention

[0004] The purpose of the present invention is to provide an intelligent control method for temperature control, pressure control, and motor life loss management of a cooling circulating water unit to solve the problems that the water supply pressure and return water temperature of the cooling circulating water system cannot be automatically regulated, and the working hours and working nodes of related equipment cannot be protectively controlled.

[0005] An intelligent control method for temperature control, pressure control, and motor life loss management of a cooling circulating water unit comprises the following steps:

[0006] S1, setting the target values ​​of the water supply pressure and return water temperature of the cooling circulation water system;

[0007] S2, through the water supply and return pipe temperature and pressure transmitters, collect the water supply pressure value and return water temperature value in real time according to the set target value, and perform initial filtering according to the set waveform amplitude;

[0008] S3, through the PID algorithm in the program module, the actual sampling result is compared with the target expected value, and the start / stop signal and the adjustment frequency of the water supply delivery pump and the refrigeration fan are given;

[0009] S4, combined with the life loss management module in the program module, according to the working time of each device, the system automatically gives the operation plan of the delivery pump and the refrigeration fan according to the device number, and the system automatically controls the operation of the equipment;

[0010] S5, the algorithm module performs feedback correction based on the difference between the estimated value and the current sampling value, thereby realizing closed-loop control of the water supply pressure and return water temperature;

[0011] S6, through the start / stop and frequency curve of the delivery pump and refrigeration fan of the calculation module, can control the start / stop in real time, increase / decrease the number of devices working simultaneously for the delivery pump and refrigeration fan, switch the industrial frequency / variable frequency working mode of the delivery pump, and reasonably adjust the working time of each device.

[0012] Furthermore, the water supply pressure of the cooling circulating water system is set in S1 as follows: first, the sampling period of the PID algorithm module in the control module is set. When the second count pointer #X_P_INT exceeds the set value, the multiplier pointer #X_POINT is assigned a value. The second count pointer is adjusted according to the actual situation, so as to achieve a value greater than this period. The setting value can be adjusted according to the actual data collection experiment. If the value changes slowly, the sampling frequency can be appropriately reduced, otherwise the sampling frequency can be increased.

[0013] Furthermore, the PID closed-loop control formula in the control algorithm module in S3 is:

[0014] Mv=Kp(An1-An)+Ki(Sp-An)+Kd(2An1-An-An2)

[0015] Among them, Mv is the adjustment increment output value, Kp is the proportional coefficient, Ki is the proportional integral coefficient, Kd is the proportional differential coefficient, An is the nth sampling value, An1 is the n-1th sampling value, and An2 is the n-2th sampling value. The given value Mv of the circulating pump rotation frequency is transferred to the frequency given register and superimposed with the current frequency value. The sampling process is that the frequency pointer is the sampling period, and the real-time pressure value is assigned to the nth sampling register, the n-1th sampling register, and the n-2th sampling register in turn.

[0016] Furthermore, the life loss management module in S4 transmits the accumulated operation time of each delivery pump in the cooling circulating water system to the duration comparison register for comparison, selects the delivery pump with the shortest accumulated working time, and thus determines the delivery pump number to be started first.

[0017] Furthermore, in S5, in terms of regulating the return water temperature, the PID algorithm module in the temperature and pressure control system module determines whether to start the refrigeration fan. If necessary, the life loss management module determines the number of the refrigeration fan to be started first according to the working time of each fan.

[0018] Furthermore, in S6, when a delivery pump has reached full frequency but still cannot reach the target desired water supply pressure setting value, the life loss management module determines to increase the number of the delivery pump put into operation, and at the same time resets the incremental value of the PID control algorithm module, and transfers the PID frequency adjustment incremental interface to the newly added delivery pump, that is, while keeping the previous delivery pump working at full frequency, the frequency of the second delivery pump is adjusted to gradually increase or decrease the number of delivery pumps put into operation; when the water supply pressure needs to be reduced, in the same way, the life loss module in the algorithm selects the current variable frequency delivery pump according to the working time of the delivery pump used, and after the frequency modulation is 0, the PID frequency adjustment incremental interface is transferred to the delivery pump frequency adjustment interface.

[0019] Furthermore, in S6, when a fan has been working for a set time and the return water temperature still cannot reach the target expected set value, the life loss management module is called to decide to increase the number of the refrigeration fan put into operation, and the incremental value of the PID control algorithm module is reset, and the PID incremental interface is transferred to the refrigeration fan added. That is, while keeping the previous refrigeration fan working, the second refrigeration fan is added, so as to gradually increase or decrease the number of refrigeration fans put into operation.

[0020] Furthermore, in S6, when the delivery pump has reached the maximum working number and the last delivery pump put into operation has reached full frequency operation, and the water supply pressure still cannot meet the target expected value, an alarm is issued to prompt the operator, and the same applies to the refrigeration fan.

[0021] The beneficial effect of the present invention is that in the present invention, each independent device is equipped with an independent PID logic control algorithm. For example, in a circulating water refrigeration system, multiple circulating water delivery pumps are equipped with multiple PID circulation control algorithm schemes for improvement. In a circulating water refrigeration system, multiple circulating water delivery pumps share a set of adjustment control algorithms. This algorithm is simpler and easier to maintain. In the actual production process, when the production environment changes, only one set of PID input domain parameters needs to be adjusted to complete the adaptation of the new production environment. This scheme adjusts the output interface of the PID control algorithm, adjusts the algorithm, and configures it to different devices, so that when the control algorithm increases the pressure, it only needs to adjust the frequency of the last delivery pump turned on, and other pumps need to maintain full-frequency working state; when the pressure is reduced, it only needs to control the delivery pump that reduces the frequency last, and other pumps only need to maintain a closed working state. This not only ensures the stability of the system, but also greatly improves the adjustment efficiency and reduces the difficulty of maintenance and adaptation. The present invention can realize real-time automatic regulation of multiple water supply delivery pump groups and multiple refrigeration fans by the system, so that the water supply pressure and return water temperature can quickly and stably reach and maintain the target expected values, and during the regulation process, the life loss management module in the program will reasonably allocate the working time of each equipment in the circulating water system, thereby realizing the protection of the equipment.

[0022] The present invention also has the following advantages:

[0023] (1) An intelligent control algorithm for temperature control, pressure control, and motor life management of a cooling water circulation unit. The algorithm can expand a set of PID control controllers to be shared by multiple regulating and delivering pump groups in the same system, so that the system can be uniformly controlled.

[0024] (2) The algorithm has an equipment life loss management submodule, which can systematically manage the usage time and usage nodes of each device in the circulating water working system, so as to minimize the equipment working loss and save costs for users.

[0025] (3) The module has adjustment limits and high and low alarm functions related to temperature and pressure.

[0026] (4) High degree of automation, full background operation, eliminating the possibility of human intervention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 To ask the invention flow chart;

[0028] Figure 2 This is a water supply pressure curve diagram after the temperature and pressure control algorithm module is adopted in the present invention;

[0029] Figure 3 This is a return water temperature curve diagram when the refrigeration fan is manually controlled in the present invention;

[0030] Figure 4This is a return water temperature curve diagram when the temperature and pressure control algorithm module is used in the present invention;

[0031] Figure 5 This is a schematic diagram of the input and output of the temperature and pressure control algorithm module of the present invention. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with the accompanying drawings.

[0033] like Figure 1 As shown, a cooling circulating water unit temperature control, pressure control, motor life loss management intelligent control method includes the following steps:

[0034] S1, setting the target values ​​of the water supply pressure and return water temperature of the cooling circulation water system;

[0035] First, set the sampling period of the PID algorithm module in the control module. When the second count pointer #X_P_INT exceeds the set value, assign a value to the frequency multiplication pointer #X_POINT. Adjust the second count pointer according to the actual situation. In this way, the value greater than this period can be adjusted according to the actual data collection experiment. If the value changes slowly, the sampling frequency can be appropriately reduced, otherwise the sampling frequency can be increased.

[0036] S2, through the water supply and return pipe temperature and pressure transmitters, collect the water supply pressure value and return water temperature value in real time according to the set target value, and perform initial filtering according to the set waveform amplitude;

[0037] S3, through the PID algorithm in the program module, the actual sampling result is compared with the target expected value, and the start / stop signal and the adjustment frequency of the water supply delivery pump and the refrigeration fan are given;

[0038] The PID algorithm module performs the first filtering according to the set waveform amplitude, and according to the PID closed-loop control formula in the control algorithm module:

[0039] Mv=Kp(An1-An)+Ki(Sp-An)+Kd(2An1-An-An2)

[0040] Among them, Mv is the adjustment increment output value, Kp is the proportional coefficient, Ki is the proportional integral coefficient, Kd is the proportional differential coefficient, An is the nth sampling value, An1 is the n-1th sampling value, and An2 is the n-2th sampling value. The given value Mv of the circulating pump rotation frequency is transferred to the frequency given register and superimposed with the current frequency value. The sampling process is that the frequency pointer is the sampling period, and the real-time pressure value is assigned to the nth sampling register, the n-1th sampling register, and the n-2th sampling register in turn;

[0041] S4, combined with the life loss management module in the program module, according to the working time of each device, the system automatically gives the operation plan of the delivery pump and the refrigeration fan according to the device number, and the system automatically controls the operation of the equipment;

[0042] The life loss management module within the program system transmits the accumulated operation time of each delivery pump in the cooling circulating water system to the duration comparison register for comparison, and selects the delivery pump with the shortest accumulated working time, thereby determining the delivery pump number to be started first;

[0043] The life loss management module within the program system transmits the accumulated operation time of each delivery pump in the cooling circulating water system to the duration comparison register for comparison, and selects the delivery pump with the shortest accumulated working time, thereby determining the delivery pump number to be started first;

[0044] S5, the algorithm module performs feedback correction based on the difference between the estimated value and the current sampling value, thereby realizing closed-loop control of the water supply pressure and return water temperature;

[0045] When a delivery pump has reached full frequency but still cannot reach the target water supply pressure setting value, the life loss management module determines the number of the delivery pump to be added, and resets the incremental value of the PID control algorithm module at the same time, and transfers the PID frequency adjustment incremental interface to the newly added delivery pump, that is, while keeping the previous delivery pump working at full frequency (or fixed frequency), adjust the frequency of the second delivery pump, in this way gradually increase or decrease the number of delivery pumps put into use; when the water supply pressure needs to be reduced, in the same way, the life loss module in the algorithm selects the current variable frequency delivery pump according to the working time of the delivery pump used, and after the frequency modulation is 0, the PID frequency adjustment incremental interface is transferred to the delivery pump frequency adjustment interface;

[0046] When a fan has been working for a set time and the return water temperature still cannot reach the target expected set value, the life loss management module is called to determine the number of the refrigeration fan to be added, and the incremental value of the PID control algorithm module is reset, and the PID incremental interface is transferred to the added refrigeration fan, that is, while keeping the previous refrigeration fan working, the second refrigeration fan is added, and the number of refrigeration fans put into operation is gradually increased or decreased in this way;

[0047] S6, through the start / stop and frequency curve of the delivery pump and refrigeration fan of the calculation module, can control the start / stop in real time, increase / decrease the number of devices working at the same time, switch the power frequency / variable frequency working mode of the delivery pump, and reasonably adjust the working time of each device;

[0048] When the delivery pump has reached the maximum working number, and the last delivery pump put into operation has reached full frequency, but the water supply pressure still cannot meet the target expected value, an alarm will be issued to remind the operator, and the same applies to the refrigeration fan;

[0049] When the number of delivery pumps has dropped to only one pump group working, the program module for reducing the pump group will be stopped to ensure that at least one circulating water delivery pump group is working, so that the workshop maintains the supply of cooling circulating water and issues corresponding prompts to the operator.

[0050] like Figure 2 As shown in the figure, the cooling water supply pressure curve is shown from 8:00 to 15:00 after the cooling circulating water system is started. It can be seen from the figure that during the regulation process using the temperature and pressure control algorithm module, the water supply pressure is maintained between 0.19MPa and 0.2MPa, and the fluctuation difference is maintained between 0.01MPa.

[0051] like Figure 3 As shown in the figure, the return water temperature curve of the cooling circulating water system is controlled by the operator manually operating the refrigeration fan from 9:00 to 16:00. As shown in the figure, although the temperature trend is decreasing, the temperature fluctuation range during the cooling process is very large, which will seriously affect the production efficiency and product quality.

[0052] like Figure 4 As shown in the figure, the return water temperature curve of the cooling circulating water system after the temperature and pressure control algorithm module is put into control from 3:00 to 7:00 is shown. As shown in the figure, the return water temperature drops steadily under the stable control of the algorithm module, and the entire cooling circulating water system cools down steadily.

[0053] like Figure 5 As shown, the target device operating variables for input acquisition parameters and output regulation of this operating system.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An intelligent control method for temperature control, pressure control, and motor life loss management of a cooling circulating water unit, characterized in that: The following steps are involved: S1, setting the target values ​​of the water supply pressure and return water temperature of the cooling circulation water system; S2, through the water supply and return pipe temperature and pressure transmitters, collect the water supply pressure value and return water temperature value in real time according to the set target value, and perform initial filtering according to the set waveform amplitude; S3, through the PID algorithm in the program module, the actual sampling result is compared with the target expected value, and the start / stop signal and the adjustment frequency of the water supply delivery pump and the refrigeration fan are given; S4, combined with the life loss management module in the program module, according to the working time of each device, the system automatically gives the operation plan of the delivery pump and the refrigeration fan according to the device number, and the system automatically controls the operation of the equipment; S5, the algorithm module performs feedback correction based on the difference between the estimated value and the current sampling value, thereby realizing closed-loop control of the water supply pressure and return water temperature; S6, through the start / stop and frequency curve of the delivery pump and refrigeration fan of the calculation module, can control the start / stop in real time, increase / decrease the number of devices working simultaneously for the delivery pump and refrigeration fan, switch the industrial frequency / variable frequency working mode of the delivery pump, and reasonably adjust the working time of each device.

2. According to claim 1, a cooling circulating water unit temperature control, pressure control, motor life loss management intelligent control method is characterized in that: The water supply pressure of the cooling circulating water system is set in S1 as follows: first, the sampling period of the PID algorithm module in the control module is set. When the second count pointer #X_P_INT exceeds the set value, the multiplier pointer #X_POINT is assigned a value. The second count pointer is adjusted according to the actual situation. In this way, the setting value of the cycle can be adjusted according to the actual data collection experiment. If the value changes slowly, the sampling frequency can be appropriately reduced, otherwise the sampling frequency can be increased.

3. According to claim 1, a cooling circulating water unit temperature control, pressure control, motor life loss management intelligent control method is characterized in that: The PID closed-loop control formula in the control algorithm module in S3 is: Mv=Kp(An1-An)+Ki(Sp-An)+Kd(2An1-An-An2) Among them, Mv is the adjustment increment output value, Kp is the proportional coefficient, Ki is the proportional integral coefficient, Kd is the proportional differential coefficient, An is the nth sampling value, An1 is the n-1th sampling value, and An2 is the n-2th sampling value. The given value Mv of the circulating pump rotation frequency is transferred to the frequency given register and superimposed with the current frequency value. The sampling process is that the frequency pointer is the sampling period, and the real-time pressure value is assigned to the nth sampling register, the n-1th sampling register, and the n-2th sampling register in turn.

4. The method for controlling temperature, pressure and motor life loss of a cooling circulating water unit according to claim 1 is characterized in that: The life loss management module in S4 transmits the accumulated operation time of each delivery pump in the cooling circulating water system to the duration comparison register for comparison, selects the delivery pump with the shortest accumulated working time, and thus determines the delivery pump number to be started first.

5. The method for controlling temperature, pressure and motor life loss of a cooling circulating water unit according to claim 4 is characterized in that: In S4, in terms of regulating the return water temperature, the PID algorithm module in the temperature and pressure control system module is used to decide whether to start the refrigeration fan. If necessary, the life loss management module is used to determine the number of the refrigeration fan to be started first according to the working time of each fan.

6. The method for controlling temperature, pressure and motor life loss of a cooling circulating water unit according to claim 5 is characterized in that: In S6, when a delivery pump has reached full frequency but still cannot reach the target desired water supply pressure setting value, the life loss management module determines to increase the number of the delivery pump put into operation, and at the same time resets the incremental value of the PID control algorithm module, and transfers the PID frequency adjustment incremental interface to the newly added delivery pump, that is, while keeping the previous delivery pump working at full frequency, the frequency of the second delivery pump is adjusted to gradually increase or decrease the number of delivery pumps put into operation; when the water supply pressure needs to be reduced, in the same way, the life loss module in the algorithm selects the current variable frequency delivery pump according to the working time of the delivery pump used, and after the frequency modulation is 0, the PID frequency adjustment incremental interface is transferred to the delivery pump frequency adjustment interface.

7. The method for controlling temperature, pressure and motor life loss of a cooling circulating water unit according to claim 6 is characterized in that: In S6, when a fan has been working for a set time and the return water temperature still cannot reach the target expected set value, the life loss management module is called to decide to increase the number of the refrigeration fan put into operation, and the incremental value of the PID control algorithm module is reset, and the PID incremental interface is transferred to the refrigeration fan added. That is, while keeping the previous refrigeration fan working, the second refrigeration fan is added, so as to gradually increase or decrease the number of refrigeration fans put into operation.

8. The method for controlling temperature, pressure and motor life loss of a cooling water circulating unit according to claim 7 is characterized in that: In S6, when the delivery pump has reached the maximum working number and the last delivery pump put into operation has reached full frequency operation, and the water supply pressure still cannot meet the target expected value, an alarm is issued to prompt the operator, and the same applies to the refrigeration fan.

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