Control method, compressor and air conditioning system

Abstract

The invention provides a control method, a compressor and an air conditioning system.The control method comprises the steps that a rectangular coordinate system is constructed according to the relation between the operation frequency and the operation pressure ratio of the compressor; the abscissa of the coordinate system represents the operation pressure ratio of the compressor, and the ordinate of the coordinate system represents the operation frequency of the compressor; wherein the operation pressure ratio is the ratio of the condensing pressure to the evaporating pressure of a unit to which the compressor belongs; on the coordinate system, a surge line of the compressor is obtained; dividing the horizontal coordinates of the coordinate system into intervals; interval anti-surge lines are obtained according to different intervals, and the interval anti-surge lines of the different intervals are fitted to form an anti-surge control line; obtaining an operation area according to the anti-surge control line; wherein the operation area is an area, located above the anti-surge control line, on the coordinate system; according to the value in the operation area, the operation frequency of the compressor is controlled, and the control method solves the technical problem that the anti-surge control precision of the compressor is poor.

Description

Technical Field

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

[0002] In the process of cooling the computer room in the data center, a chiller is usually used to provide 12-20°C medium-temperature chilled water to the computer room air conditioner. The EC fan forms an airflow organization, and the cold air is sent downward and the hot air is returned upward to take away the heat dissipation of the server. In the prior art, the 7°C low-temperature chilled water in the vapor compression cycle chiller (heat pump) unit, industrial and commercial chiller (heat pump) unit and similar purposes is used to provide refrigerant for the computer room. The above refrigerant is much higher than the 12-20°C medium-temperature chilled water required for the cooling of the computer room. Under the working conditions of similar cooling water temperature, the pressure ratio of the medium-temperature outlet water unit is obviously much lower. In view of the high sensible heat load density and the 12-20°C chilled water outlet working conditions of the data room, many compressor manufacturers have launched small pressure ratio centrifugal chillers.

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

[0004] However, the existing surge line test results show that for data center units operating under low cooling water temperature (pressure ratio Pr < 1.6), the anti-surge margin is large, and the minimum load cannot be unloaded to 30% during automatic operation, and cannot even be unloaded to below 50%, and the unit adjustment range is narrow. The surge line from the minimum pressure ratio Pr1.1 to the limit pressure ratio Pr3.2 does not fit the quadratic equation curve well as a whole. According to the existing surge line fitting method, the precision of the fitted anti-surge line is poor, resulting in a large anti-surge margin in some pressure ratio sections. This makes the existing compressors not energy-efficient enough. Summary of the invention

[0005] The purpose of the present invention is to overcome the above technical deficiencies and provide a control method, a compressor and an air-conditioning system to solve the technical problem of poor anti-surge control accuracy of the compressor in the related art.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: a control method is provided, including: constructing a rectangular coordinate system according to the relationship between the operating frequency and the operating pressure ratio of the compressor; the horizontal axis of the coordinate system represents the operating pressure ratio of the compressor, and the vertical axis 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; on the coordinate system, obtaining the surge line of the compressor; dividing the horizontal axis 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 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 within the operating area.

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

[0008] Furthermore, according to the secondary anti-surge line and the interval anti-surge line, the method for obtaining the operating area includes: setting a boundary value X, when the value of Pr is less than X, taking the interval anti-surge line as the anti-surge control line; when the value of Pr is greater than X, taking the secondary anti-surge line as the anti-surge control line.

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

[0010] Furthermore, the method for obtaining the interval anti-surge line includes: 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 ; Among them, the number of terms in 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] Furthermore, according to different intervals, interval anti-surge lines are obtained respectively, and the interval anti-surge lines of different intervals are fitted to form an anti-surge control line. The method includes: setting a limit value X, in the interval [X- / ,X], dividing the horizontal axis into n-2 areas, and each area is respectively based on the formula F=A n Pr n +B n Pr n-1 +Cn Pr n-2 +......+NPr+β n , obtain the interval anti-surge line, and fit the interval anti-surge lines of each area to form the anti-surge control line.

[0012] A compressor is applicable to the above control method.

[0013] An air conditioning system comprises a compressor, and the compressor is suitable for the above-mentioned control method.

[0014] Furthermore, the air conditioning system includes: a condenser connected to the air inlet of the compressor; an evaporator connected to the air outlet of the compressor; and a control module, wherein the control module controls the operating frequency of the compressor according to the pressure of the condenser and the pressure of the evaporator.

[0015] Furthermore, the air-conditioning system includes: a condensing pressure sensor for detecting the pressure of the condenser; and an evaporating pressure sensor for detecting the pressure of the evaporator; wherein the control module calculates the operating pressure ratio of the air-conditioning system based on the ratio of the pressure value detected by the condensing pressure sensor to the pressure value detected by the evaporating pressure sensor; and the control module controls the operating frequency of the compressor within the range of the operating area based on the operating pressure ratio.

[0016] Beneficial effects:

[0017] 1. The control method of the present invention comprises: constructing a rectangular coordinate system according to the relationship between the operating frequency and the operating pressure ratio of the compressor; the horizontal axis of the coordinate system represents the operating pressure ratio of the compressor, and the vertical axis 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 axis 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 area according to the anti-surge control line; wherein the operating area is an area located 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. By adopting the above-mentioned setting, the values ​​of the compressor operating frequency are differentiated and controlled according to different operating pressure ratios of the unit, thereby broadening the value range of the compressor operating frequency. When the operating pressure ratio of the unit is small, the compressor can adopt a smaller operating frequency, and the anti-surge control is more precise, thereby reducing costs and solving the technical problem of poor anti-surge control accuracy of the compressor.

[0018] 2. The control method of the present invention realizes segmented adaptive and high-precision anti-surge operation of the compressor frequency;

[0019] 3. The control method of the present invention effectively increases the unloading margin of the unit and broadens the operating range of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0021] Figure 2 is a schematic diagram of an anti-surge control line used in an embodiment of the present invention;

[0022] Figure 3 It is a schematic diagram of the expanded operating range of the anti-surge control line used in the embodiment of the present invention compared with the anti-surge line of the prior art;

[0023] Figure 4 is a flow chart of an embodiment of a control method adopted in an embodiment of the present invention;

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

[0025] Figure 6 is a structural schematic diagram of an embodiment of an air conditioning system provided by an embodiment of the present invention;

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

[0027] The above drawings include the following reference numerals:

[0028] 1. Surge line; 2. Section 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 those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0031] See also Figures 1 to 7According to an embodiment of the present invention, 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 the compressor; the horizontal axis of the coordinate system represents the operating pressure ratio of the compressor, and the vertical axis 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 1 of the compressor on the coordinate system; dividing the horizontal axis of the coordinate system into intervals; obtaining interval anti-surge lines 2 according to different intervals, 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 the area located above the anti-surge control line 3 on the coordinate system; controlling the operating frequency of the compressor according to the value in the operating area 4. By adopting the above-mentioned setting, the values ​​of the compressor operating frequency are differentiated and controlled according to different operating pressure ratios of the unit, thereby broadening the value range of the compressor operating frequency. When the operating pressure ratio of the unit is small, the compressor can adopt a smaller operating frequency, and the anti-surge control is more precise, thereby reducing costs and solving the technical problem of poor anti-surge control accuracy of the compressor.

[0032] Specifically, in this 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] See also Figures 1 to 5 The method for obtaining the anti-surge control line 3 includes: according to the equation F = APr 2 +BPr+C to obtain the secondary anti-surge line 5; wherein Pr is the operating pressure ratio; F is the operating frequency; according to the secondary anti-surge line 5 and the interval anti-surge line 2, the anti-surge control line 3 is obtained.

[0034] Specifically, the anti-surge line represents the minimum value to which the operating frequency of the centrifugal unit can be reduced during operation. If the real-time operating frequency of the compressor is controlled by the program to be ≥ the calculated value of this curve, surge will not occur.

[0035] In the control method of this embodiment, see Figures 1 to 5 According to the secondary anti-surge line 5 and the interval anti-surge line 2, the method for obtaining the operation area 4 includes: setting a boundary value X, when the value of Pr is less than X, taking the interval anti-surge line 2 as the anti-surge control line 3; when the value of Pr is greater than X, taking the secondary anti-surge line 5 as the anti-surge control line 3. In this way, the operation range of the unit's operation frequency in the low pressure ratio stage is widened.

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

[0037] In the control method of this embodiment, the method for obtaining the interval anti-surge line 2 includes: 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 ; Among them, the number of terms in 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 conditions of the unit, and βn is the difference between the anti-surge line and the surge line, which is the anti-surge margin.

[0039] The above-mentioned setting can prevent surge while widening the operating range of the unit, especially in small load conditions with smaller pressure ratios. This method can expand the operating range, thus avoiding frequent shutdowns of the unit or high-load operation.

[0040] See also Figures 1 to 5 In the control method of this embodiment, the interval anti-surge line 2 is obtained according to different intervals, and the interval anti-surge line 2 of different intervals is fitted to form the anti-surge control line 3. The method includes: setting a limit value X, dividing the horizontal axis into n-2 areas in the interval [XX-1.1 / n-2,X], and each area is respectively according to the formula F=A n Pr n +B n Pr n-1 +C n Pr n-2 +......+NPr+β n , obtain the interval anti-surge line 2, and fit the interval anti-surge lines 2 of each area to form the anti-surge control line 3.

[0041] With the above settings, you can customize the selection to set the segmented fitting anti-surge line to start controlling the pressure ratio and widen the unit's operating range according to the operating differences of different units.

[0042] The compressor of this embodiment is suitable for the above-mentioned control method.

[0043] The air conditioning system of this embodiment includes a compressor 10, and the compressor 10 is suitable for the above-mentioned control method.

[0044] Specifically, the air-conditioning system adopts the above-mentioned pressure ratio segmented multi-time equation anti-surge line control method to achieve segmented adaptive, high-precision anti-surge operation. Through the anti-surge curve with variable anti-surge minimum frequency according to the pressure ratio, the unit's unloading margin is effectively improved and the unit's operating range is widened.

[0045] In the air conditioning system of this embodiment, see Figure 6 The air conditioning system includes: a condenser 20 connected to the air inlet of the compressor 10; an evaporator 30 connected to the air outlet of the compressor 10; and a control module 40, wherein the control module 40 controls the operating 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 this embodiment, see Figure 7 The air-conditioning system includes: a condensing pressure sensor 50, used to detect the pressure of the condenser 20; an evaporating pressure sensor 60, used to detect the pressure of the evaporator 30; wherein the control module 40 calculates the operating 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; the control module 40 controls the operating frequency of the compressor 10 within the range of the operating area 4 according to the operating pressure ratio.

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

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

[0049] In the early stage of the refrigeration unit, when the terminal load is small, the unit operating pressure is relatively small, and an excessively large anti-surge margin is not required at this time, otherwise it is easy to cause low energy efficiency and frequent start and stop of the unit under small load conditions. An anti-surge control method is proposed, in which the anti-surge line is dynamically adjusted with the pressure ratio, the smaller the operating pressure ratio, the smaller the anti-surge margin, and the wider the operating range.

[0050] like 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 designed for the compressor. Based on the existing quadratic equation anti-surge line, the initial value X of the segmented fitting anti-surge line pressure ratio is set according to the need to expand the operating range, and X>1.1.

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

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

[0053] Assuming n is the power of the anti-surge line equation, the pressure ratio in the range of 1.1 to X is evenly divided into n-2 segmented anti-surge control intervals. In the range of X-(X-1.1) / (n-2)≤Pr<X, the anti-surge line is controlled according to the n-power anti-surge line equation:

[0054] F=A n Pr n +B n Pr n-1 +C n Pr n-2 +......+NPr+β n , where the number of terms in 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, within the ranges of 1.475≤Pr<1.6, 1.35≤Pr<1.475, 1.225≤Pr<1.35, and 1.1≤Pr<1.225, anti-surge control is performed according to the anti-surge lines of the cubic equation, the quartic equation, the quintic equation, and the sextic equation, respectively, that is:

[0056] 1.475≤Pr<1.6, according to the cubic anti-surge line F=A3Pr 3 +B3Pr 2 +C3Pr+β3;

[0057] 1.35≤Pr<1.475, according to the fourth power anti-surge line F=A4Pr 4 +B4Pr 3 +C4Pr 2 +D4Pr+β4;

[0058] 1.225≤Pr<1.35, according to the fifth power anti-surge line F=A5Pr 5 +B5Pr 4 +C5Pr 3 +D5Pr 2 +E4Pr+β5;

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

[0060] Depend on Figure 3 After multi-equation segmented anti-surge control, within the pressure ratio range of 1.1 to X, the multi-equation segmented anti-surge line has a larger frequency adjustment range than the original quadratic equation anti-surge line, which broadens the operating range and makes the anti-surge control closer to the real surge line.

[0061] Through the segmented anti-surge line control under small pressure ratio conditions, the anti-surge line control follows the pressure ratio change, effectively reducing the anti-surge line control margin of the compressor at small pressure ratio, widening the operating range of the unit, and achieving energy-saving operation under small load conditions.

[0062] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

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

[0064] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0065] In the above embodiments of the present application, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments.

[0066] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A control method, characterized in that: include: According to the relationship between the operating frequency and the operating pressure ratio of the compressor, a rectangular coordinate system is constructed; the abscissa of the coordinate system represents the operating pressure ratio of the compressor, and the ordinate 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; On the coordinate system, obtaining a surge line (1) of the compressor; Dividing the abscissa of the coordinate system into intervals; Obtaining interval anti-surge lines (2) according to different intervals respectively, fitting the interval anti-surge lines (2) of different intervals to form anti-surge control lines (3); obtaining an operating area (4) according to the anti-surge control line (3); wherein the operating area (4) is an area located above the anti-surge control line (3) on the coordinate system; The operating frequency of the compressor is controlled according to the value within the operating region (4).

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

3. The control method according to claim 2, characterized in that: The method for obtaining the operating area (4) according to the secondary anti-surge line (5) and the interval anti-surge line (2) comprises: A demarcation value X is set. When the value of Pr is less than X, the interval anti-surge line (2) is taken as the anti-surge control line (3); when the value of Pr is greater than X, the secondary anti-surge line (5) is taken as the anti-surge control line (3).

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

1.

5. The control method according to claim 1, characterized in that: 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 ; Among them, the number of terms in 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.

6. The control method according to claim 5, characterized in that: The method of obtaining interval anti-surge lines (2) according to different intervals and fitting the interval anti-surge lines (2) of different intervals to form an anti-surge control line (3) includes: Set the limit value X, and divide the horizontal axis into n-2 regions in the interval [X-(X-1.1) / (n-2),X]. Each region is divided according to the formula F=A n Pr n +B n Pr n-1 +C n Pr n-2 +......+NPr+β n , obtain the interval anti-surge line (2), and fit the interval anti-surge line (2) of each area to form the anti-surge control line (3).

7. A compressor, characterized in that: The compressor is suitable for the control method according to any one of claims 1 to 6.

8. An air conditioning system, comprising a compressor (10), characterized in that: The compressor (10) is suitable for the control method according to any one of claims 1 to 6.

9. The air conditioning system according to claim 8, characterized in that: The air conditioning system comprises: A condenser (20) connected to an air inlet of the compressor (10); an evaporator (30) connected to the air outlet of the compressor (10); A control module (40), wherein the control module (40) controls the operating frequency of the compressor (10) according to the pressure of the condenser (20) and the pressure of the evaporator (30).

10. The air conditioning system according to claim 9, characterized in that: The air conditioning system comprises: A condensation pressure sensor (50), used for detecting the pressure of the condenser (20); an evaporation pressure sensor (60), used for detecting the pressure of the evaporator (30); The control module (40) calculates the operating 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 operating frequency of the compressor (10) within the range of the operating area (4) according to the operating pressure ratio.

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