Optimization method for operation frequency of water supply variable frequency pump set

Abstract

The invention discloses a method for optimizing the operation frequency of a water supply variable-frequency pump set, and relates to the technical field of metallurgy, and the method comprises the steps: collecting the historical water data of a user point of a water supply pump set; determining the water pump lift required by the corresponding user point based on the historical water consumption data; determining the water pump rotating speed required by the user point according to the water pump lift required by the user point; and determining the motor shaft power of the corresponding user point based on the water pump rotating speed required by the user point. By analyzing the relation between the water pump performance and energy saving, the proportional relation between the flow and the water pump rotating speed, the water pump lift and the motor shaft power is determined, the water pump lift needed by a user point is determined by combining historical water use data of the user point, and then the water pump rotating speed is determined; therefore, the frequency of the frequency converter is determined, and maximization of the power-saving benefit is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, and particularly to an optimization method for the operating frequency of a water supply variable-frequency pump group. Background Art

[0002] At present, most of the variable-frequency devices in the water supply systems in the metallurgy field adopt system constant-pressure frequency conversion and water-level control frequency conversion. The system constant-pressure frequency conversion automatically varies the frequency according to the amount of water supply to ensure the stability of the pressure of the water supply main pipe; the water-level control frequency conversion automatically varies the frequency according to the level of the suction well liquid level. Neither of these two frequency conversion methods can maximize the power-saving effect of the system. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an optimization method for the operating frequency of a water supply variable-frequency pump group.

[0004] To solve the above technical problems, the technical solution of the present invention is as follows: An optimization method for the operating frequency of a water supply variable-frequency pump group includes: Collecting historical water consumption data of the user points of the water supply pump group; Determining the required pump head for the corresponding user points based on the historical water consumption data; Determining the required pump speed for the user points according to the required pump head for the user points; Determining the motor shaft power for the corresponding user points based on the required pump speed for the user points.

[0005] As a preferred scheme of the optimization method for the operating frequency of the water supply variable-frequency pump group of the present invention, wherein: the determining the required pump speed for the user points according to the required pump head for the user points includes: Determining the proportional coefficient between the pump operating frequency and the pump speed, and taking it as the first proportional coefficient; Determining the proportional coefficient between the pump head and the pump operating frequency, and taking it as the second proportional coefficient; Determining the rated head, rated operating frequency and rated speed of the pump; Calculating the ratio between the required pump head for the user points and the rated head of the pump, and calculating the required pump operating frequency for the user points based on this ratio, the rated operating frequency of the pump and the second proportional coefficient; Calculating the required pump speed for the user points based on the required pump operating frequency for the user points, the rated speed of the pump and the first proportional coefficient.

[0006] As a preferred scheme of the optimization method for the operating frequency of the water supply variable-frequency pump group of the present invention, wherein: the determining the proportional coefficient between the pump operating frequency and the pump speed, and taking it as the first proportional coefficient includes: Determine the proportionality coefficient between the operating frequency of the water pump and the rotational speed of the water pump through Formula 1. The Formula 1 is as follows: , where f is the operating frequency of the water pump, Nf is the rated operating frequency of the water pump, n is the rotational speed of the water pump, and Nn is the rated rotational speed of the water pump.

[0007] As a preferred embodiment of the optimization method for the operating frequency of the water supply variable-frequency pump unit of the present invention, wherein: determining the proportionality coefficient between the water pump head and the operating frequency of the water pump and using it as the second proportionality coefficient includes: Determine the proportionality coefficient between the water pump head and the operating frequency of the water pump through Formula 2. The Formula 2 is as follows: , where H is the water pump head and NH is the rated water pump head.

[0008] As a preferred embodiment of the optimization method for the operating frequency of the water supply variable-frequency pump unit of the present invention, wherein: based on the rotational speed of the water pump required at the user point, determining the motor shaft power corresponding to the user point includes: Determine the proportionality coefficient between the rotational speed of the water pump and the motor shaft power through Formula 3. The Formula 3 is as follows: , where P is the motor shaft power and NP is the rated motor shaft power.

[0009] As a preferred embodiment of the optimization method for the operating frequency of the water supply variable-frequency pump unit of the present invention, wherein: after determining the motor shaft power corresponding to the user point based on the rotational speed of the water pump required at the user point, it further includes: Calculating the operating power saving rate corresponding to the user point based on the motor shaft power corresponding to the user point.

[0010] As a preferred embodiment of the optimization method for the operating frequency of the water supply variable-frequency pump unit of the present invention, wherein: calculating the operating power saving rate corresponding to the user point based on the motor shaft power corresponding to the user point includes: Calculate the operating power saving rate corresponding to the user point through Formula 4. The Formula 4 is: ξ = 100 - P, where ξ is the operating power saving rate corresponding to the user point.

[0011] The beneficial effects of the present invention are: By analyzing the relationship between the water pump performance and energy saving, the present invention determines the proportional relationship between the flow rate and the rotational speed of the water pump, the water pump head, and the motor shaft power, and then combines the historical water consumption data of the user point to determine the water pump head required at the user point, and further determines the rotational speed of the water pump. On the premise of meeting the water use requirements of on-site users, the rotational speed of the water pump can be determined, and then the frequency of the frequency converter can be determined to ensure the maximization of the power saving benefit. Description of the Drawings

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0013] Figure 1 It is a schematic flow chart of the optimization method for the operating frequency of the water supply variable-frequency pump group provided by the present invention. Detailed implementation manners

[0014] To make the content of the present invention easier to be clearly understood, the following will further elaborate on the present invention in detail according to the detailed implementation manners and in combination with the drawings.

[0015] Figure 1 It is a schematic flow chart of the optimization method for the operating frequency of the water supply variable-frequency pump group provided by the present application. The method specifically includes the following steps: Step S101: Collect the historical water consumption data of the user points of the water supply pump group.

[0016] Step S102: Determine the required pump head for the corresponding user points based on the historical water consumption data.

[0017] Specifically, for the water use process and water use mode of the user points of the water supply pump group, determine the maximum water volume, minimum water volume required for production of the corresponding user points, and the actual required pump head of the user points.

[0018] Step S103: Determine the required pump speed for the user points according to the required pump head of the user points.

[0019] Specifically, first, determine the proportionality coefficient between the pump operating frequency and the pump speed, and take it as the first proportionality coefficient. Determine the proportionality coefficient between the pump operating frequency and the pump speed through Formula 1. Formula 1 is: , where f is the pump operating frequency, Nf is the rated operating frequency of the pump, n is the pump speed, and Nn is the rated speed of the pump.

[0020] After that, determine the proportionality coefficient between the pump head and the pump operating frequency, and take it as the second proportionality coefficient. Determine the proportionality coefficient between the pump head and the pump operating frequency through Formula 2. Formula 2 is: , where H is the pump head and NH is the rated pump head.

[0021] After determining the first proportionality coefficient and the second proportionality coefficient, determine the rated head, rated operating frequency, and rated speed of the water pump, calculate the ratio between the water pump head required at the user point and the rated head of the water pump, and calculate the water pump operating frequency required at the user point based on this ratio, the rated operating frequency of the water pump, and the second proportionality coefficient.

[0022] Finally, calculate the water pump speed required at the user point based on the water pump operating frequency required at the user point, the rated speed of the water pump, and the first proportionality coefficient.

[0023] Table 1 is a table showing the relationship between water pump performance and energy conservation. See Table 1:

[0024] Table 1 Analyze the relationship between water pump performance and energy conservation: When the flow rate decreases, when the water pump speed drops to 90% of the rated speed, that is, the frequency is 45HZ, the water pump head is 81% of the rated head, and the motor shaft power drops by 27.1%; when the water pump speed drops to 80% of the rated speed, that is, the frequency is 40HZ, the water pump head is 64% of the rated head, and the motor shaft power drops by 48.8%, and so on for calculation (the calculation method is the same as above); on the premise of meeting the water use requirements of on-site users, determine the water pump speed and determine the frequency converter frequency to ensure the maximization of power-saving benefits.

[0025] From this, it can be obtained that for a water pump, the flow rate is proportional to the speed N, the head H is proportional to the square of the speed N, and the shaft power P is proportional to the cube of the speed N.

[0026] Step S104: Determine the motor shaft power corresponding to the user point based on the water pump speed required at the user point.

[0027] Specifically, determine the proportionality coefficient between the water pump speed and the motor shaft power through Formula Three. Formula Three is: , where P is the motor shaft power and NP is the rated shaft power of the motor.

[0028] After determining the motor shaft power corresponding to the user point, calculate the operating power-saving rate corresponding to the user point through Formula Four. Formula Four is: ξ = 100 - P, where ξ is the operating power-saving rate corresponding to the user point.

[0029] Based on Step S103, it can be known that the power-saving rate can also be calculated through Formula Five. Formula Five is: Power-saving rate = (1 - frequency converter operating frequency / 50HZ) 3 *100%. For example: When the water pump speed drops by 10% of the rated speed, that is, 45HZ, the operating power-saving rate is: (1 - 45 / 50) 3 *100% = 27.1%.

[0030] The following is illustrated through specific embodiments.

[0031] According to the water-using process and water-using method at the user points of the low-pressure water supply pump group in a heavy plate rolling mill (the main users of the low-pressure water supply pump: high-pressure descaling water, intermediate billet cooling water, roller table cooling water, straightening machine cooling water, and rolling mill backup roll cooling water. Among them, the high-pressure descaling water and intermediate billet cooling water users use water intermittently due to the requirements of the steel rolling process, and the pressure at the on-site water-using points shall not be lower than 0.4 Mpa). According to the observation during normal production operation, there are 2 water volume change intervals in the production of this system (when the high-pressure descaling water and intermediate billet cooling water are using water, the system water supply is large, and when these two users do not use water, the system water volume is small): 1. Flow rate: 800 - 1000 m3 / h (pressure 0.45 - 0.5 Mpa); 2. Flow rate: 2020 - 2600 m3 / h (pressure 0.39 - 0.45 Mpa).

[0032] When using a large amount of water, the motor runs at 50 HZ. When using a small amount of water, the frequency setting is calculated as follows: According to the requirement that the pressure at the on-site water-using points shall not be lower than 0.4 Mpa (40-meter head), first calculate the minimum frequency of the motor according to the pressure requirement: According to the nameplate parameters of this pump type: rated flow rate 1033 m 3 / h, rated head 59 meters, and the pump head H% is deduced from the above table (the relationship between pump performance and energy conservation): 40 / 59 = 67%, and the corresponding motor frequency is 40 HZ. Considering the pipeline friction loss, the motor frequency is initially set to 42 HZ. At this frequency, the pump speed is 84% of the rated speed.

[0033] Two frequencies are set for the frequency converter: low frequency 42 HZ for using a small amount of water and high frequency 50 HZ for using a large amount of water. By comparing and observing the operating parameters after the transformation and frequency adjustment, there is a large energy-saving space under the condition of meeting the production requirements of the intermediate billet cooling water in the heavy plate. Before the adjustment, the normal flow rate of the system is 800 - 1000 m3 / h, the pressure is 0.62 Mpa, and the operating current of each motor is 14 A. When using a large amount of water (intermediate billet water), the system flow rate is 2300 m3 / h, the pressure is 0.48 Mpa, and the operating current of each motor is 18 A. After the adjustment, the normal flow rate of the system is 800 - 1000 m3 / h, the pressure is 0.47 Mpa, the motor operating current is 8 A. When using a large amount of water (intermediate billet water), the system flow rate is 2300 m3 / h, the pressure is 0.42 Mpa, and the motor operating current is 12 A. The average shaft power reduction per pump per hour is: 1.732 * 10 * ((14 + 18) - (8 + 12)) / 2 * 0.85 = 88.32 kw. The monthly electricity cost savings is: 2 motors * 88.33 * 24 * 31 * 0.57 = 74,900 yuan. The annual electricity cost savings is: 898,800 yuan.

[0034] Thus, on the premise of meeting the water use requirements of on-site users, the technical solution of this application can determine the pump speed and then determine the frequency converter frequency to ensure the maximization of power saving benefits.

[0035] In addition to the above embodiments, the present invention may have other embodiments; all technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention.

Claims

1. A method for optimizing the operating frequency of a water supply variable frequency pump group, characterized in that: include: Collect historical water consumption data of water supply pump group user points; Determine the water pump head required for the corresponding user point based on the historical water use data; Determine the required pump speed at the user point based on the pump head required at the user point; The motor shaft power of the corresponding user point is determined based on the water pump speed required by the user point.

2. The method for optimizing the operating frequency of a water supply variable frequency pump group according to claim 1, characterized in that: Determining the required water pump speed of the user point according to the water pump head required by the user point includes: Determine a proportionality coefficient between the operating frequency of the water pump and the rotating speed of the water pump, and use it as a first proportionality coefficient; Determine the proportionality coefficient between the pump head and the pump operating frequency, and use it as the second proportionality coefficient; Determine the rated head, rated operating frequency and rated speed of the water pump; Calculating the ratio between the water pump head required by the user point and the rated water pump head, and calculating the water pump operating frequency required by the user point based on the ratio, the rated operating frequency of the water pump and the second proportionality coefficient; The water pump speed required by the user point is calculated based on the water pump operating frequency required by the user point, the water pump rated speed, and the first proportionality coefficient.

3. The method for optimizing the operating frequency of a water supply variable frequency pump group according to claim 2, characterized in that: The step of determining the proportionality coefficient between the water pump operating frequency and the water pump speed and using it as the first proportionality coefficient includes: The proportional coefficient between the water pump operating frequency and the water pump speed is determined by formula 1, which is: , where f is the operating frequency of the water pump, Nf is the rated operating frequency of the water pump, n is the speed of the water pump, and Nn is the rated speed of the water pump.

4. The method for optimizing the operating frequency of a water supply variable frequency pump group according to claim 3 is characterized in that: The method of determining the proportionality coefficient between the water pump head and the water pump operating frequency and using it as the second proportionality coefficient includes: The proportional coefficient between the pump head and the pump operating frequency is determined by Formula 2, which is: , where H is the pump head and NH is the rated pump head.

5. The method for optimizing the operating frequency of a water supply variable frequency pump set according to claim 4 is characterized in that: Determining the motor shaft power of the corresponding user point based on the water pump speed required by the user point includes: The proportional coefficient between the water pump speed and the motor shaft power is determined by Formula 3, which is: , where P is the motor shaft power and NP is the motor rated shaft power.

6. The method for optimizing the operating frequency of a water supply variable frequency pump set according to claim 1, characterized in that: After determining the motor shaft power of the corresponding user point based on the water pump speed required by the user point, the method further includes: The operation power saving rate of the corresponding user point is calculated based on the motor shaft power of the corresponding user point.

7. The method for optimizing the operating frequency of a water supply variable frequency pump set according to claim 3, characterized in that: The calculation of the operation power saving rate of the corresponding user point based on the motor shaft power of the corresponding user point includes: The operating power saving rate of the corresponding user point is calculated by formula 4, and the formula 4 is: ξ=100-P, where ξ is the operating power saving rate of the corresponding user point.

Images