A control method, compressor and air conditioning system

Abstract

The application provides a control method, a compressor and an air conditioning system. The control method comprises the following steps: constructing a rectangular coordinate system according to the relationship between the operating frequency and the operating pressure ratio of the compressor; the horizontal coordinate of the coordinate system represents the operating pressure ratio of the compressor, and the vertical coordinate of the coordinate system represents the operating frequency of the compressor; wherein the operating pressure ratio is the ratio of the condensing pressure to the evaporating pressure of the unit to which the compressor belongs; obtaining the surge line of the compressor on the coordinate system; dividing the horizontal coordinate of the coordinate system into intervals; obtaining interval anti-surge lines according to different intervals respectively, fitting the interval anti-surge lines of different intervals to form an anti-surge control line; obtaining an operating area according to the anti-surge control line; wherein the operating area is an area above the anti-surge control line on the coordinate system; and controlling the operating frequency of the compressor according to the value in the operating area. The control method of the application solves the technical problem of poor anti-surge control precision of the compressor.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cooling technology, in particular to a control method, a compressor and an air conditioning system. BACKGROUND

[0002] In the process of cooling a data center room, a chilled water unit is usually used to provide 12-20 DEG C medium temperature chilled water to the room air conditioner, and an EC fan is used to form air flow organization, and cold air is sent downward and hot air is returned upward to take away the heat dissipation of the server. In the prior art, 7 DEG C low temperature chilled water in a vapor compression cycle chilled water (heat pump) unit, an industrial and commercial chilled water (heat pump) unit and the like is used to provide refrigerant to the room, and the refrigerant is much higher than the 12-20 DEG C medium temperature chilled water required by the room cooling. In the case of similar cooling water temperature, the pressure ratio of the medium temperature outlet water unit is obviously much lower. For the high sensible heat load density of the data center room and the 12-20 DEG C chilled water outlet condition, many compressor manufacturers have successively launched small pressure ratio centrifugal chilled water units.

[0003] At present, the compressor usually adopts a quadratic equation anti-surge line for anti-surge control, such as Figure 1 The F-Pr (frequency of centrifugal compressor operation-pressure ratio of operation) curve diagram, the surge line and the region below the surge line represent that when the centrifugal compressor operates at the current operating frequency and operating pressure ratio, the surge phenomenon will occur.

[0004] However, the existing surge line test results show that when the data center unit operates at a low cooling water temperature (pressure ratio Pr < 1.6), the anti-surge margin is large, the minimum load cannot be unloaded to 30% in automatic operation, and even cannot be unloaded to below 50%, and the unit adjustment range is narrow. From the minimum pressure ratio Pr1.1 to the limit pressure ratio Pr3.2, the overall fitting degree of the surge line is not high, and according to the existing surge line fitting method, the anti-surge line with poor precision is fitted, which results in a large anti-surge margin in some pressure ratio sections. The existing compressor is not energy-saving enough. SUMMARY

[0005] The present application aims to overcome the above technical deficiencies, and provides a control method, a compressor and an air conditioning system to solve the technical problem of poor anti-surge control precision of the compressor in the related art.

[0006] To achieve the above technical purposes, the application adopts the following technical solutions: a control method is provided, comprising: constructing a rectangular coordinate system according to the relationship between the operating frequency and the operating pressure ratio of a compressor; the horizontal coordinate of the coordinate system represents the operating pressure ratio of the compressor, and the vertical coordinate of the coordinate system represents the operating frequency of the compressor; wherein the operating pressure ratio is the ratio of the condensing pressure to the evaporating pressure of the unit to which the compressor belongs; obtaining the surge line of the compressor on the coordinate system; dividing the horizontal coordinate of the coordinate system into intervals; obtaining interval anti-surge lines according to different intervals respectively, and fitting the interval anti-surge lines of different intervals to form an anti-surge control line; obtaining an operating area according to the anti-surge control line; wherein the operating area is the area above the anti-surge control line on the coordinate system; and controlling the operating frequency of the compressor according to the value in the operating area.

[0007] Further, the method for obtaining the anti-surge control line comprises: obtaining a quadratic anti-surge line according to the equation F=APr 2 +BPr+C; wherein Pr is the operating pressure ratio, and F is the operating frequency; and obtaining the anti-surge control line according to the quadratic anti-surge line and the interval anti-surge line.

[0008] Further, the method for obtaining the operating area according to the quadratic anti-surge line and the interval anti-surge line comprises: setting a demarcation value X, taking the interval anti-surge line as the anti-surge control line when the value of Pr is less than X, and taking the quadratic anti-surge line as the anti-surge control line when the value of Pr is greater than X.

[0009] Further, the demarcation value X is greater than 1.1.

[0010] Further, the method for obtaining the interval anti-surge line comprises: the equation of the interval anti-surge line is F=A n Pr n +B n Pr n-1 +C n Pr n-2 +......+NPr+β n ; wherein the number of terms of the equation is n, that is, the number of coefficients A, B, C,..., N is n; F is the operating frequency, and Pr is the operating pressure ratio.

[0011] Further, the method for obtaining the interval anti-surge line according to different intervals respectively, fitting the interval anti-surge lines of different intervals to form an anti-surge control line comprises: setting a limit value X, dividing the horizontal coordinate into n-2 regions within the interval [X- / , X], and obtaining the interval anti-surge line according to the formula F=A n Pr n +B n Pr n-1 +Cn Pr n-2 +......+NPr+β n , obtaining the interval anti-surge lines, fitting the interval anti-surge lines of each region to form the anti-surge control line.

[0012] A compressor suitable for the control method described above.

[0013] An air conditioning system comprising a compressor suitable for the control method described above.

[0014] Further, the air conditioning system comprises: a condenser connected to the air inlet of the compressor; an evaporator connected to the air outlet of the compressor; a control module for controlling the operating frequency of the compressor according to the pressure of the condenser and the pressure of the evaporator.

[0015] Further, the air conditioning system comprises: a condenser pressure sensor for detecting the pressure of the condenser; an evaporator pressure sensor for detecting the pressure of the evaporator; wherein the control module calculates the operating pressure ratio of the air conditioning system according to the ratio of the pressure value detected by the condenser pressure sensor to the pressure value detected by the evaporator pressure sensor; and controls the operating frequency of the compressor within the range of the operating region according to the operating pressure ratio.

[0016] Advantages:

[0017] 1. The control method comprises: constructing a rectangular coordinate system according to the relationship between the operating frequency of the compressor and the operating pressure ratio; the horizontal coordinate of the coordinate system represents the operating pressure ratio of the compressor, and the vertical coordinate of the coordinate system represents the operating frequency of the compressor; wherein the operating pressure ratio is the ratio of the condenser pressure to the evaporator pressure of the unit to which the compressor belongs; obtaining the surge line of the compressor on the coordinate system; dividing the horizontal coordinate of the coordinate system into intervals; obtaining interval anti-surge lines according to different intervals, fitting the interval anti-surge lines of different intervals to form an anti-surge control line; obtaining an operating region according to the anti-surge control line; wherein the operating region is the region above the anti-surge control line on the coordinate system; and controlling the operating frequency of the compressor according to the values in the operating region. According to the above setting, the operating frequency of the compressor is divided into different values for control according to different operating pressure ratios of the unit, which widens the value range of the operating frequency of the compressor, allows the compressor to use a smaller operating frequency in the case of small operating pressure ratio of the unit, and makes the anti-surge control more accurate, thereby reducing the cost and solving the technical problem of poor anti-surge control accuracy of the compressor.

[0018] 2、The control method of the application realizes segmented self-adaption of compressor frequency and high-precision anti-surge operation;

[0019] 3、The control method of the application effectively improves unloadable margin of the unit and widens operation range of the unit. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a schematic diagram of an anti-surge line of the prior art;

[0021] Figure 2 is a schematic diagram of an anti-surge control line adopted by the embodiment of the application;

[0022] Figure 3 is a schematic diagram of widened operation range of the anti-surge control line adopted by the embodiment of the application relative to the anti-surge line of the prior art;

[0023] Figure 4 is a flow chart of one embodiment of the control method adopted by the embodiment of the application;

[0024] Figure 5 is a flow chart of another embodiment of the control method provided by the embodiment of the application;

[0025] Figure 6 is a structural schematic diagram of one embodiment of the air conditioning system provided by the embodiment of the application;

[0026] Figure 7 is a structural schematic diagram of another embodiment of the air conditioning system provided by the embodiment of the application.

[0027] Among the above drawings, the following reference signs are included:

[0028] 1, surge line; 2, interval anti-surge line; 3, anti-surge control line; 4, operation area; 5, secondary anti-surge line;

[0029] 10, compressor; 20, condenser; 30, evaporator; 40, control module; 50, condensing pressure sensor; 60, evaporating pressure sensor. DETAILED DESCRIPTION

[0030] In order to enable personnel in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work should fall within the protection scope of the present application.

[0031] Reference is made to Figures 1 to 7According to the embodiment of the present application, a control method is provided, comprising: constructing a rectangular coordinate system according to the relationship between the operating frequency and the operating pressure ratio of a compressor; the horizontal coordinate of the coordinate system represents the operating pressure ratio of the compressor, and the vertical coordinate of the coordinate system represents the operating frequency of the compressor; wherein the operating pressure ratio is the ratio of the condensing pressure to the evaporating pressure of the unit to which the compressor belongs; obtaining a surge line 1 of the compressor on the coordinate system; dividing the horizontal coordinate of the coordinate system into intervals; obtaining interval anti-surge lines 2 according to different intervals respectively, and fitting the interval anti-surge lines 2 of different intervals to form an anti-surge control line 3; obtaining an operating area 4 according to the anti-surge control line 3; wherein the operating area 4 is an area above the anti-surge control line 3 on the coordinate system; and controlling the operating frequency of the compressor according to the value in the operating area 4. With the above arrangement, the value range of the operating frequency of the compressor is widened by dividing the value of the operating frequency of the compressor according to different operating pressure ratios of the unit, so that the compressor can adopt a smaller operating frequency in the case of a small operating pressure ratio of the unit, and the anti-surge control is more accurate, thereby reducing the cost and solving the technical problem of poor anti-surge control accuracy of the compressor.

[0032] Specifically, in the embodiment, the condensing pressure is the pressure of the condenser of the centrifugal unit, and the evaporating pressure is the pressure of the evaporator of the centrifugal unit.

[0033] Referring to Figures 1 to 5 The method for obtaining the anti-surge control line 3 comprises: obtaining a quadratic anti-surge line 5 according to the equation F=APr 2 +BPr+C; wherein Pr is the operating pressure ratio, and F is the operating frequency; and obtaining the anti-surge control line 3 according to the quadratic anti-surge line 5 and the interval anti-surge line 2.

[0034] Specifically, the anti-surge line represents the minimum value of the operating frequency to which the centrifugal unit can be reduced during operation, and the compressor will not surge if the real-time operating frequency of the compressor controlled by the program is greater than or equal to the calculated value of the curve.

[0035] In the control method of the embodiment, referring to Figures 1 to 5 The method for obtaining the operating area 4 according to the quadratic anti-surge line 5 and the interval anti-surge line 2 comprises: setting a demarcation value X, taking the interval anti-surge line 2 as the anti-surge control line 3 when the value of Pr is less than X, and taking the quadratic anti-surge line 5 as the anti-surge control line 3 when the value of Pr is greater than X. In this way, the operating range of the operating frequency of the unit in the low pressure ratio stage is widened.

[0036] Referring to Figures 1 to 5In the control method of the embodiment, the demarcation value X is greater than 1.1. In this way, the operating frequency range of the unit in the low pressure ratio stage is widened, and the calculation of the anti-surge line in the high pressure ratio stage is simplified.

[0037] In the control method of the embodiment, the method for obtaining the interval anti-surge line 2 comprises: the equation of the interval anti-surge line 2 is F=A n Pr n +B n Pr n-1 +C n Pr n-2 +......+NPr+β n ; wherein the number of terms of the equation is n, that is, the number of coefficients A, B, C,..., N is n; F is the operating frequency, and Pr is the operating pressure ratio.

[0038] Specifically, A, B, C,..., N are set values selected according to the operating condition of the unit, and βn is the difference between the anti-surge line and the surge line, which is the anti-surge allowance.

[0039] With the above setting, the anti-surge is prevented, and the operating range of the unit is widened, especially in the small load condition with smaller pressure ratio. The operating range widened by the method is wider, and the frequent shutdown of the unit is avoided, or in the case of high load operation.

[0040] Referring to Figures 1 to 5 In the control method of the embodiment, the interval anti-surge line 2 is obtained according to different intervals, and the interval anti-surge lines 2 of different intervals are fitted to form the anti-surge control line 3. The method comprises: setting a demarcation value X, dividing the horizontal coordinate into n-2 regions within the interval [X-X-1.1 / n-2, X], and obtaining the interval anti-surge line 2 according to the formula F=A n Pr n +B n Pr n-1 +C n Pr n-2 +......+NPr+β n in each region, and fitting the interval anti-surge lines 2 of each region to form the anti-surge control line 3.

[0041] With the above setting, the start control pressure ratio of the segmented fitting anti-surge line can be selected according to the difference in the operation of different units, and the operating range of the unit is widened.

[0042] The compressor of the embodiment is suitable for the control method described above.

[0043] The air conditioning system of the embodiment comprises a compressor 10, and the compressor 10 is suitable for the control method described above.

[0044] Specifically, the air conditioning system adopts the above-mentioned pressure ratio segmented multiple equation anti-surge line control method to realize segmented self-adaption and high-precision anti-surge operation, and effectively improves the unloadable margin of the unit and widens the operation range of the unit through the anti-surge curve with variable anti-surge minimum frequency according to the pressure ratio.

[0045] In the air conditioning system of the embodiment, referring to Figure 6 , the air conditioning system comprises: a condenser 20 connected with the gas inlet of the compressor 10; an evaporator 30 connected with the gas outlet of the compressor 10; and a control module 40, which controls the operation frequency of the compressor 10 according to the pressure of the condenser 20 and the pressure of the evaporator 30.

[0046] In the air conditioning system of the embodiment, referring to Figure 7 , the air conditioning system comprises: a condensing pressure sensor 50 for detecting the pressure of the condenser 20; an evaporating pressure sensor 60 for detecting the pressure of the evaporator 30; wherein the control module 40 calculates the operation pressure ratio of the air conditioning system according to the ratio of the pressure value detected by the condensing pressure sensor 50 to the pressure value detected by the evaporating pressure sensor 60; and the control module 40 controls the operation frequency of the compressor 10 to be within the range of the operation region 4 according to the operation pressure ratio.

[0047] The control method of the embodiment is described as follows:

[0048] Surge is an inherent characteristic of centrifugal compressors, and the surge line thereof can be obtained by fitting test data, which is usually a quadratic equation F=APr 2 +BPr+C, wherein F is the operation frequency of the centrifugal compressor; the condensing pressure of the unit and the evaporating pressure of the unit can be detected, and the ratio of the two is the operation pressure ratio Pr of the unit. Usually, on the basis of the fitted surge line, a proper anti-surge margin β is added to obtain a quadratic equation anti-surge line, such as F=APr 2 +BPr+C+β.

[0049] At the initial stage of use of the refrigeration unit, under the condition of small terminal load, the operation pressure ratio of the unit is small, and at this time, a large anti-surge margin is not needed, otherwise, it is easy to cause low energy efficiency and frequent start-stop of the unit under small load conditions. A kind of anti-surge control method is proposed, which dynamically adjusts the anti-surge line according to the pressure ratio, and the smaller the operation pressure ratio, the smaller the anti-surge margin, which widens the operation range to a greater extent.

[0050] As Figure 2, the horizontal axis is the operating pressure ratio Pr, the vertical axis is the operating frequency F, and Pr = 1.1 is the minimum pressure ratio of the compressor design. On the basis of the existing quadratic anti-surge line, the initial value X of the segmented fitting anti-surge line pressure ratio is set according to the need to broaden the operating range, and X > 1.1.

[0051] When the current operating pressure ratio is greater than X, the operating frequency is controlled according to the conventional quadratic anti-surge line F = APr 2 +BPr+C+β.

[0052] When the current operating pressure ratio is less than X, the anti-surge control is performed according to the segmented fitting anti-surge control.

[0053] Set n as the power of the anti-surge line equation, then the pressure ratio in the range of 1.1 to X is divided into n-2 segmented anti-surge control intervals, and in the range of X-(X-1.1) / (n-2)≤Pr

[0054] F = A n Pr n +B n Pr n-1 +C n Pr n-2 +......+NPr+β n , where the number of terms of the equation is n, that is, the number of coefficients A, B, C,..., N is n.

[0055] For example, when X = 1.6 and n = 6, in the ranges of 1.475≤Pr

[0056] 1.475≤Pr 3 +B3Pr 2 +C3Pr+β3.

[0057] 1.35≤Pr 4 +B4Pr 3 +C4Pr 2 +D4Pr+β4.

[0058] 1.225≤Pr 5 +B5Pr 4 +C5Pr 3 +D5Pr 2 +E4Pr+β5.

[0059] 1.1≤Pr<1.225, according to the 6th power anti-asthma line F=A6Pr 6 +B6Pr 5 +C6Pr 4 +D6Pr 3 +E6Pr 2 +F6Pr+β6.

[0060] Depend on Figure 3 Through multi-equation segmented surge control, within the pressure ratio range of 1.1 to X, the multi-equation segmented surge control line has a wider frequency adjustment range than the original quadratic equation surge control line, thus expanding the operating range and making the surge control closer to the real surge line.

[0061] By using segmented anti-surge control under low pressure ratio conditions, the anti-surge control follows the pressure ratio changes, effectively reducing the compressor anti-surge control margin at low pressure ratios, expanding the unit's operating range, and achieving energy-saving operation under low load conditions.

[0062] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0063] Optionally, specific examples in this embodiment can refer to the examples described in the above embodiments, and will not be repeated here.

[0064] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0065] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0066] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A control method, characterized in that, include: Based on the relationship between the compressor's operating frequency and operating pressure ratio, a rectangular coordinate system is constructed; the horizontal axis of the coordinate system represents the compressor's operating pressure ratio, and the vertical axis represents the compressor's operating frequency; wherein, the operating pressure ratio is the ratio of the condensing pressure to the evaporating pressure of the unit to which the compressor belongs; On the coordinate system, the surge line (1) of the compressor is obtained; Divide the x-coordinate of the coordinate system into intervals; According to different intervals, obtain interval anti-surge lines (2) respectively, fit the interval anti-surge lines (2) of different intervals to form anti-surge control lines (3); according to the anti-surge control lines (3), obtain the operating area (4); wherein, the operating area (4) is the area located above the anti-surge control lines (3) on the coordinate system; The operating frequency of the compressor is controlled according to the value within the operating range (4); the method for obtaining the anti-surge line (2) of the interval includes: The equation for the anti-surge line (2) in the interval is F=A n Pr n +B n Pr n-1 +C n Pr n-2 +......+NPr+β n The equation has n terms, meaning the number of coefficients A, B, C...N is n; F is the operating frequency, and Pr is the operating pressure ratio. The method of obtaining interval asthma prevention lines (2) according to different intervals and fitting the interval asthma prevention lines (2) of different intervals to form an asthma prevention control line (3) includes: Set a boundary value X. Within the interval [X - (X - 1.1) / (n - 2), X], divide the x-axis into n-2 regions. For each region, apply the formula F = A. n Pr n +B n Pr n-1 +C n Pr n-2 +......+NPr+β n Obtain the interval anti-asthma line (2), and fit the interval anti-asthma line (2) of each region to form the anti-asthma control line (3).

2. The control method according to claim 1, characterized in that, The method for obtaining the asthma control line (3) includes: According to the equation F=APr 2 +BPr+C yields the secondary anti-surge line (5); where Pr is the operating pressure ratio; and F is the operating frequency; Based on the secondary anti-asthma line (5) and the interval anti-asthma line (2), the anti-asthma control line (3) is obtained.

3. The control method according to claim 2, characterized in that, The method for obtaining the operating area (4) based on the secondary anti-surge line (5) and the interval anti-surge line (2) includes: Set a boundary value X. When the value of Pr is less than X, take the interval anti-asthma line (2) as the anti-asthma control line (3); when the value of Pr is greater than X, take the secondary anti-asthma line (5) as the anti-asthma control line (3).

4. The control method according to claim 3, characterized in that, The dividing value X is greater than 1.

1.

5. A compressor, characterized in that, The compressor is applicable to the control method described in any one of claims 1 to 4.

6. An air conditioning system, said air conditioning system comprising a compressor (10), characterized in that, The compressor (10) is applicable to the control method of any one of claims 1 to 5.

7. The air conditioning system according to claim 6, characterized in that, The air conditioning system includes: The condenser (20) is connected to the air inlet of the compressor (10); An evaporator (30) is connected to the outlet of the compressor (10); The control module (40) controls the operating frequency of the compressor (10) based on the pressure of the condenser (20) and the pressure of the evaporator (30).

8. The air conditioning system according to claim 7, characterized in that, The air conditioning system includes: A condensing pressure sensor (50) is used to detect the pressure of the condenser (20); An evaporation pressure sensor (60) is used to detect the pressure of the evaporator (30); The control module (40) calculates the operating pressure ratio of the air conditioning system based on the ratio of the pressure value detected by the condensing pressure sensor (50) to the pressure value detected by the evaporating pressure sensor (60); the control module (40) controls the operating frequency of the compressor (10) to be within the range of the operating area (4) based on the operating pressure ratio.

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