Compressor control method, compressor, HVAC equipment and computer storage medium

Abstract

The present invention discloses a compressor control method, a compressor, HVAC equipment, and a computer storage medium. The compressor includes a screw, a slide valve, a frequency converter, and a motor. The frequency converter is used to control the motor to drive the screw, and the slide valve is used to adjust the effective working length of the screw. The compressor control method includes: obtaining the compressor exhaust pressure; and, based on the exhaust pressure exceeding a preset pressure value, reducing the motor frequency and / or unloading the slide valve to reduce the compressor load. The compressor control method of the present invention can, on the one hand, prevent compressor overheating; on the other hand, by reducing the compressor load, the motor current is reduced, thereby reducing the motor's heat generation and preventing motor overheating failures.

Description

Technical Field

[0001] The present invention relates to the technical field of compressors, and in particular to a compressor control method, compressor HVAC equipment, and a computer storage medium. Background Art

[0002] This section merely provides background information related to the present disclosure and is not necessarily prior art.

[0003] The variable frequency screw compressor is equipped with a frequency converter to control the motor frequency of the compressor, and a sliding valve is used to adjust the effective working length of the compressor screw, so that the variable frequency screw compressor can achieve capacity adjustment.

[0004] Under high-load conditions, the compressor exhaust pressure is too high, causing the compressor motor to be loaded. Due to the high load level of the compressor, the motor current is large, and the motor heat is at a high level. In severe cases, the compressor motor overheating fault will be triggered. Summary of the Invention

[0005] The purpose of the present invention is to at least solve the problem that controlling the motor frequency reduction under high load conditions may cause motor overheating and failure. This purpose is achieved through the following technical solutions:

[0006] A first aspect of the present invention proposes a control method for a compressor, which includes a screw, a sliding valve, a frequency converter and a motor, wherein the motor is transmission-connected to the screw, the frequency converter is used to control the movement frequency of the motor, and the sliding valve is used to adjust the effective working length of the screw. The control method for the compressor includes: obtaining the exhaust pressure of the compressor; adjusting the frequency of the motor and / or the position of the sliding valve according to the exhaust pressure being greater than a preset pressure value to reduce the load of the compressor.

[0007] According to the control method of the compressor of the present invention, when the exhaust pressure of the compressor is higher than the preset pressure value, it means that the load of the compressor is large. In order to prevent the compressor from being overloaded, the frequency of the motor is reduced and / or the slide valve is unloaded to reduce the effective working length of the screw, thereby reducing the suction volume of the compressor, and then gradually reducing the exhaust pressure of the compressor, thereby achieving the purpose of reducing the load of the compressor. On the one hand, it prevents the compressor from overheating. On the other hand, by reducing the load of the compressor, the current of the motor is reduced, thereby reducing the heat generated by the motor and preventing the occurrence of motor overheating failure.

[0008] In addition, the control method of the compressor according to the present invention may also have the following additional technical features:

[0009] In some embodiments of the present invention, the control method of the compressor also includes: obtaining the real-time operating frequency of the motor and the current position of the slide valve; obtaining the frequency lower limit value corresponding to the motor at the current position; the step of reducing the frequency of the motor and / or unloading the slide valve according to the exhaust pressure being greater than the pressure preset value includes: controlling the operating frequency of the motor to be reduced to the frequency lower limit value according to the exhaust pressure being greater than the pressure preset value and the real-time operating frequency being greater than the frequency lower limit value; or unloading the slide valve according to the exhaust pressure being greater than the pressure preset value and the real-time operating frequency being less than or equal to the frequency lower limit value.

[0010] In some embodiments of the present invention, after the step of obtaining the frequency lower limit value corresponding to the motor at the current position, the step further includes: obtaining the rated frequency Fmax and the frequency reduction tolerance ΔF of the motor, Fmax-ΔF ≥ the frequency lower limit value Fmin; the step of reducing the frequency of the motor and / or unloading the slide valve according to the exhaust pressure being greater than the preset pressure value includes: controlling the operating frequency of the motor to be reduced to Fmax-ΔF according to the exhaust pressure being greater than the preset pressure value and the real-time operating frequency being greater than Fmax-ΔF; unloading the slide valve according to the exhaust pressure being greater than the preset pressure value and the real-time operating frequency being less than or equal to Fmax-ΔF.

[0011] In some embodiments of the present invention, the step of unloading the slide valve includes: adjusting the position of the slide valve to reduce the effective working length of the screw.

[0012] In some embodiments of the present invention, the sliding valve includes multiple adjustable positions, each adjustable position corresponds to an effective working length of the screw; the step of adjusting the position of the sliding valve to reduce the effective working length of the screw includes: controlling the sliding valve to adjust from the current nth adjustable position to the n-1th adjustable position, the effective working length of the screw corresponding to the nth adjustable position is greater than the effective working length of the screw corresponding to the n-1th adjustable position, wherein n≥2.

[0013] In some embodiments of the present invention, each level of the adjustable position corresponds to a frequency lower limit value; the step of obtaining the frequency lower limit value corresponding to the motor at the current position includes: obtaining the n-th level frequency lower limit value corresponding to the motor and the n-th level of the adjustable position; the step of controlling the operating frequency of the motor to be reduced to the frequency lower limit value includes: according to the slide valve being in the n-th level of the adjustable position, controlling the operating frequency of the motor to be reduced to the n-th level of the frequency lower limit value.

[0014] According to a second aspect of the present invention, a compressor is also proposed, which includes a screw, a sliding valve, a frequency converter and a motor, the motor being transmission-connected to the screw, the frequency converter being used to control the movement frequency of the motor, and the sliding valve being used to adjust the effective working length of the screw; the compressor also includes: a pressure sensor for detecting the exhaust pressure of the compressor; a control device being electrically connected to the sliding valve, the frequency converter, the pressure sensor and the motor, respectively, the control device being used to obtain the exhaust pressure of the compressor, and reducing the frequency of the motor and / or unloading the sliding valve according to the exhaust pressure being greater than a preset pressure value.

[0015] In some embodiments of the present invention, the compressor also includes a displacement sensor, which is electrically connected to the control device and is used to detect the current position of the slide valve. The control device obtains the real-time operating frequency of the motor and the current position, and obtains the frequency lower limit value of the motor corresponding to the current position based on the current position. The control device also controls the operating frequency of the motor to be reduced to the frequency lower limit value based on the exhaust pressure being greater than the pressure preset value and the real-time operating frequency being greater than the frequency lower limit value, and unloads the slide valve based on the exhaust pressure being greater than the pressure preset value and the real-time operating frequency being less than or equal to the frequency lower limit value.

[0016] In some embodiments of the present invention, the control device is further used to obtain the rated frequency Fmax and the frequency reduction tolerance ΔF of the motor, Fmax-ΔF ≥ the frequency lower limit Fmin, and based on the exhaust pressure being greater than the pressure preset value and the real-time operating frequency being greater than Fmax-ΔF, control the operating frequency of the motor to be reduced to Fmax-ΔF, or, based on the exhaust pressure being greater than the pressure preset value and the real-time operating frequency being less than or equal to Fmax-ΔF, unload the slide valve.

[0017] According to a third aspect of the present invention, a HVAC equipment is further provided, which includes the compressor described in the technical solution of the second aspect.

[0018] According to a fourth aspect of the present invention, a computer storage medium is further proposed, on which computer-readable instructions are stored. When the computer-readable instructions are executed by one or more processors, one or more of the processors execute the compressor control method as described in any one of the technical solutions of the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference numerals are used throughout the accompanying drawings to denote the same components. In the accompanying drawings:

[0020] Figure 1 Schematically showing a flow chart of a method for controlling a compressor according to some embodiments of the present invention;

[0021] Figure 2 Schematically showing a flow chart of a method for controlling a compressor according to some embodiments of the present invention;

[0022] Figure 3 Schematically showing a flow chart of a method for controlling a compressor according to some embodiments of the present invention;

[0023] Figure 4 The block diagram of the control device and various components according to some embodiments of the present invention is schematically shown.

[0024] The reference numerals are as follows:

[0025] 10. Pressure sensor;

[0026] 20. Frequency converter;

[0027] 30. Slide valve;

[0028] 40. Motor;

[0029] 50. Displacement sensor;

[0030] 60. Control device; 61. Memory; 62. Processor. DETAILED DESCRIPTION

[0031] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0032] It should be understood that the terms used herein are for the purpose of describing specific example embodiments only and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "comprise", "include", "contain" and "have" are inclusive and therefore specify the presence of stated features, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring them to be performed in the specific order described or illustrated, unless the order of execution is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0033] Although the terms first, second, third, etc. can be used in the text to describe multiple elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms can only be used to distinguish an element, component, region, layer or section from another region, layer or section. Unless the context clearly indicates otherwise, terms such as "first", "second" and other numerical terms do not imply order or sequence when used in the text. Therefore, the first element, component, region, layer or section discussed below can be referred to as the second element, component, region, layer or section without departing from the teaching of the example embodiments.

[0034] For ease of description, spatially relative terms may be used herein to describe the relationship of one element or feature relative to another element or feature as shown in the figures, such as "inside," "outside," "inside," "outside," "below," "beneath," "above," and the like. Such spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is flipped, an element described as "below" or "below" another element or feature would then be oriented as "above" or "above" another element or feature. Thus, the example term "below" can include both above and below orientations. The device may be otherwise oriented (rotated 90 degrees or in other orientations) and the spatially relative descriptors used herein are interpreted accordingly.

[0035] According to an embodiment of the present invention, a control method for a compressor is also proposed. The compressor in the present invention is a screw compressor, which includes a screw, a sliding valve, a frequency converter and a motor. The frequency converter is used to control the motor to drive the screw, and the sliding valve is used to adjust the effective working length of the screw.

[0036] Among them, Figure 1 As shown, the compressor control method includes the following steps:

[0037] Step S101: obtaining the exhaust pressure of the compressor;

[0038] Step S102: according to the exhaust pressure being greater than the preset pressure value, the frequency of the motor is reduced and / or the slide valve is unloaded to reduce the load of the compressor.

[0039] In step S101 and step S102, the exhaust pressure of the compressor refers to the pressure of the refrigerant gas in the exhaust pipe at the outlet of the compressor, which is the pressure of the gas finally discharged by the compressor. When the exhaust pressure of the compressor is too high, the operating current of the motor will increase, which may burn the motor. It will also aggravate the consumption of lubricating oil in the compressor and make it thinner, affecting the lubrication effect. It will also cause the compressor to overheat and produce excessively high exhaust temperature, leading to problems such as carbonization of lubricating oil. Therefore, different compressors need to set a preset pressure value. When the exhaust pressure exceeds the preset pressure value, it means that the exhaust pressure of the compressor is too high and there are the various risks mentioned above caused by excessive exhaust pressure. Therefore, by reducing the frequency of the motor and / or unloading the slide valve to reduce the effective working length of the screw, the suction volume of the compressor is reduced, and then the exhaust pressure of the compressor is gradually reduced to achieve the purpose of reducing the load of the compressor. On the one hand, it prevents the compressor from overheating. On the other hand, by reducing the load of the compressor, the current of the motor is reduced, thereby reducing the heat generated by the motor and preventing motor overheating failure.

[0040] It should be noted that the preset pressure value has different values ​​depending on the compressor model and is not specifically limited here.

[0041] Among them, the unloading slide valve means adjusting the position of the slide valve to reduce the effective working length of the screw, forming a bypass branch between the air inlet and the air outlet of the compressor, and redistributing part of the refrigerant from the air inlet to the air outlet of the compressor to the air inlet of the compressor, thereby reducing the exhaust volume of the compressor, so as to achieve the purpose of reducing the exhaust pressure of the compressor and the load of the compressor.

[0042] According to some embodiments of the present invention, Figure 2 As shown, the compressor control method includes the following steps:

[0043] Step S201: obtaining the exhaust pressure of the compressor;

[0044] Step S202: obtaining the real-time operating frequency of the motor and the current position of the slide valve;

[0045] Step S203: Obtain the lower limit value of the motor frequency corresponding to the current position;

[0046] Step S204: According to the exhaust pressure being greater than the preset pressure value and the real-time operating frequency being greater than the frequency lower limit, the operating frequency of the motor is controlled to be reduced to the frequency lower limit;

[0047] Step S205: Unloading the slide valve according to the exhaust pressure being greater than the preset pressure value and the real-time operating frequency being less than or equal to the frequency lower limit value.

[0048] In this embodiment, step S201 is the same as step S101 and will not be described again here.

[0049] It should be noted that under high load conditions, the exhaust pressure of the compressor is too high. To prevent the compressor from overheating, the motor is generally controlled to operate at a reduced frequency. However, when the motor is operating at a reduced frequency, the suction volume of the compressor is smaller than when the motor is operating at the maximum frequency, which will lead to poor cooling of the motor that relies on refrigerant cooling. Since the exhaust pressure drop process of the compressor is slower than the change in the suction volume, when the refrigerant flow used to cool the motor decreases, the exhaust pressure of the compressor is still in a relatively high range, so that the motor still has a large load, and the motor current is positively correlated with the load, and the motor current is positively correlated with the heat generated by the motor. Therefore, the control method of controlling the motor frequency reduction may cause the cooling capacity of the refrigerant delivered to the motor to be less than the heat generated by the motor, causing the motor temperature to rise while the motor frequency is reduced, and then causing the motor to overheat.

[0050] Based on the above, in step S202, the current position of the slide valve refers to the position of the slide valve in the axial direction of the screw. Specifically, a screw compressor compresses gas by reducing its working volume. Its core component is a pair of intermeshing male and female rotors. To adjust the compressor's gas output, axially movable slide valves are installed on the high-pressure side of each rotor. This movement of the slide valve changes the effective working length of the screw, thereby affecting the compressor's gas output and energy efficiency.

[0051] Before the slide valve moves, its initial position maximizes the air volume in the screw compressor's primary volume, and the compressor operates at 100% load. As the slide valve moves toward the compressor's discharge end, the effective working length of the screw decreases, reducing the amount of air in the primary volume and, consequently, the compressor's output and load. Therefore, by determining the slide valve's position, we can determine the current effective working length of the screw and the compressor's load.

[0052] In step S203 , the lower limit of the frequency corresponding to the current position of the motor and the slide valve means that the current load state of the compressor can be obtained according to the current position of the slide valve. Therefore, the lower limit of the frequency of the motor can be obtained based on the load state of the compressor.

[0053] The lower frequency limit refers to the minimum frequency at which the motor can operate while ensuring sufficient refrigerant circulation to cool the motor, based on the compressor load. Understandably, if the motor's operating frequency falls below the lower frequency limit after the motor's lower frequency limit is determined, sufficient refrigerant circulation will not be ensured to cool the motor, potentially causing the motor to overheat.

[0054] The specific value of the frequency lower limit is measured by experimental simulation of the same model of compressor or the same compressor. When the compressor is under different load conditions, multiple frequency lower limit value data corresponding to the load conditions of the compressor are established. The load conditions of the compressor correspond to the position of the slide valve. Therefore, a mapping relationship between the different positions of the slide valve and the corresponding multiple frequency lower limit values ​​can be established, that is, each position of the slide valve has a frequency lower limit value corresponding to the position.

[0055] In step S204, when the exhaust pressure is greater than the preset pressure value, it means that the exhaust pressure of the current compressor is too high, and the real-time operating frequency of the motor is greater than the lower frequency limit, then it means that the compressor can maintain sufficient refrigerant circulation volume to meet the cooling of the motor when operating at any operating frequency within the range from the current real-time operating frequency to the lower frequency limit. Therefore, the operating frequency of the motor can be controlled to be reduced to the lower frequency limit. On the premise of ensuring that the motor can be effectively cooled, the exhaust volume of the compressor is reduced by reducing the operating frequency of the motor, thereby reducing the exhaust pressure and preventing the compressor from overheating.

[0056] It should be noted that in step S204, if the exhaust pressure remains greater than the preset pressure value after the operating frequency of the control motor is reduced to the lower frequency limit and the preset time has passed, the step of unloading the slide valve is executed. The preset time can be set to any time period, such as 20 seconds, 30 seconds, one minute, five minutes, ten minutes, two minutes, etc. The purpose of setting the preset time is to provide a certain buffer time to determine the fact that the exhaust pressure cannot be reduced after the operating frequency of the control motor is reduced to the lower frequency limit.

[0057] In step S205, when the exhaust pressure is greater than the preset pressure value, it means that the exhaust pressure of the current compressor is too high, and the real-time operating frequency of the motor is less than or equal to the frequency lower limit. If the machine reduces the exhaust pressure by reducing the motor operating frequency, it will inevitably cause the refrigerant circulation volume to be reduced to a level that cannot meet the cooling needs of the motor, which may cause the motor to overheat. Therefore, in this step, when the real-time operating frequency of the motor is less than or equal to the frequency lower limit, the motor operating frequency is not reduced, but the slide valve is unloaded to reduce the load of the compressor by reducing the effective working length of the screw. On the one hand, reducing the exhaust pressure of the compressor prevents the compressor from overheating. On the other hand, reducing the load of the compressor can also reduce the current of the motor, thereby reducing the heat generated by the motor and preventing the occurrence of motor overheating.

[0058] In some embodiments, the slide valve includes multiple adjustable positions, each of which corresponds to an effective working length of the screw, enabling the compressor to transition between various load conditions. For example, in one exemplary embodiment, the slide valve includes three adjustable positions: a first, a second, and a third. The third adjustable position is the initial position of the slide valve, at which the effective working length of the screw corresponding to the slide valve is maximum and the compressor load is 100%. The effective working length of the screw corresponding to the second adjustable position is less than the effective working length of the screw corresponding to the third adjustable position, and the compressor load is 75%. The effective working length of the screw corresponding to the first adjustable position is less than the effective working length of the screw corresponding to the second adjustable position, and the compressor load is 50%.

[0059] Furthermore, the process of unloading the slide valve refers to adjusting the third adjustable position of the slide valve to the second adjustable position, or adjusting the second adjustable position of the slide valve to the first adjustable position.

[0060] It is understandable that the multi-stage adjustable position is not limited to three stages, but can also be set to two stages of adjustable positions and correspond to 100% compressor load and 50% compressor load respectively, or can also be set to four stages, five stages, six stages, etc., which are not listed here one by one. Among them, taking n as a representative of the total number of levels, the step of adjusting the position of the slide valve to reduce the effective working length of the screw includes: controlling the slide valve to adjust from the current nth adjustable position to the n-1th adjustable position, the effective working length of the screw corresponding to the nth adjustable position is greater than the effective working length of the screw corresponding to the n-1th adjustable position, wherein n≥2.

[0061] In some embodiments, the step of obtaining a lower limit value of the frequency corresponding to the position of the motor and the slide valve includes: obtaining an nth-level lower limit value of the frequency corresponding to the motor and the nth-level adjustable position;

[0062] The step of controlling the operating frequency of the motor to decrease to the frequency lower limit includes: controlling the operating frequency of the motor to decrease to the nth frequency lower limit according to the slide valve being in the nth adjustable position.

[0063] In the step of obtaining the nth frequency lower limit value corresponding to the motor and the nth adjustable position, each adjustable position corresponds to a frequency lower limit value. That is, when the compressor is in different load states, the corresponding frequency lower limit value is different. For example, in a case where the multi-level adjustable position includes two adjustable positions, the first adjustable position corresponds to a compressor load of 50%, and the second adjustable position corresponds to a compressor load of 100%.

[0064] The first frequency lower limit corresponds to a 50% compressor load. Based on this 50% compressor load, the first frequency lower limit is the minimum frequency value required to ensure sufficient refrigerant circulation to cool the motor. Understandably, if the motor's operating frequency falls below the first frequency lower limit at 50% compressor load, insufficient refrigerant circulation will be ensured to cool the motor, potentially causing the motor to overheat. Therefore, at 50% compressor load, the motor's operating frequency must be controlled to be greater than or equal to the first frequency lower limit to prevent overheating.

[0065] The second lower frequency limit corresponds to a 100% compressor load. Based on this 100% compressor load, the second lower frequency limit is the minimum frequency required to ensure sufficient refrigerant circulation to cool the motor. Understandably, if the motor's operating frequency falls below the second lower frequency limit when the compressor is at 100% load, insufficient refrigerant circulation will be ensured to cool the motor, potentially causing the motor to overheat. Therefore, when the compressor is at 100% load, the motor's operating frequency must be controlled to be greater than or equal to the second lower frequency limit to prevent overheating.

[0066] Therefore, in this embodiment, the step of controlling the operating frequency of the motor to be reduced to the lower limit of the frequency includes: according to the slide valve being in the nth adjustable position, controlling the operating frequency of the motor to be reduced to the nth lower limit of the frequency, ensuring that the motor can obtain sufficient refrigerant cooling supply to ensure normal heat dissipation of the motor, so that when the exhaust pressure is too high, the frequency of the motor can be reduced to a larger range, so as to quickly reduce the exhaust pressure and prevent the compressor from overheating.

[0067] According to some embodiments of the present invention, Figure 3 As shown, the compressor control method includes the following steps:

[0068] Step S301: obtaining the exhaust pressure of the compressor;

[0069] Step S302: Acquire the real-time operating frequency of the motor and the current position of the slide valve;

[0070] Step S303: Obtain the lower limit value of the motor frequency corresponding to the current position;

[0071] Step S304: obtaining the rated frequency Fmax and the frequency reduction tolerance ΔF of the motor, where Fmax-ΔF≥the frequency lower limit Fmin;

[0072] Step S305: According to the exhaust pressure being greater than the preset pressure value and the real-time operating frequency being greater than Fmax-ΔF, the operating frequency of the motor is controlled to decrease to Fmax-ΔF;

[0073] Step S306 : Unloading the slide valve according to the exhaust pressure being greater than the preset pressure value and the real-time operating frequency being less than or equal to Fmax-ΔF.

[0074] In this embodiment, step S301 is the same as step S201, step S302 is the same as step S202, and step S303 is the same as step S203, which will not be repeated here.

[0075] In step S304, the frequency reduction tolerance ΔF is a buffer frequency value obtained through experimental simulation of a compressor sample. Different frequency reduction tolerances ΔF can be set for compressors with different rated frequencies. The larger the rated frequency of the compressor, the larger the frequency reduction tolerance value. For example, for a compressor with a rated frequency of 50 Hz, the frequency reduction tolerance ΔF can be set to 5 Hz, and for a compressor with a rated frequency of 60 Hz, the frequency reduction tolerance ΔF can be set to 8 Hz. In this application, the value of the frequency reduction tolerance ΔF can take any value in the range of [0 Hz, 10 Hz]. For example, the frequency reduction tolerance ΔF can be set to 1 Hz, 2 Hz, 4 Hz, 5 Hz, 6 Hz, 7 Hz, 8 Hz, 9 Hz, 10 Hz, etc.

[0076] It should also be noted that the value of the frequency reduction tolerance ΔF must also satisfy Fmax-ΔF≥the frequency lower limit Fmin.

[0077] It should be noted that in step S304, if the exhaust pressure remains greater than the preset pressure value after the operating frequency of the control motor is reduced to Fmax-ΔF and the preset time has passed, the step of unloading the slide valve is executed. The preset time can be set to any period of time, such as 20 seconds, 30 seconds, one minute, 5 minutes, 10 minutes, 2 minutes, etc. The purpose of setting the preset time is to provide a certain buffer time to determine the fact that the exhaust pressure cannot be reduced after the operating frequency of the control motor is reduced to Fmax-ΔF.

[0078] In step S305, when the exhaust pressure is greater than the preset pressure value and the real-time operating frequency of the motor is greater than Fmax-ΔF, it means that the compressor can maintain sufficient refrigerant circulation volume to meet the cooling of the motor when operating at any operating frequency within the range from the current real-time operating frequency to Fmax-ΔF. Therefore, the operating frequency of the motor can be controlled to be reduced to Fmax-ΔF. On the premise of ensuring that the motor can be effectively cooled, the exhaust volume of the compressor is reduced by reducing the operating frequency of the motor, thereby reducing the exhaust pressure and preventing the compressor from overheating.

[0079] It should also be noted that the purpose of Fmax-ΔF≥the frequency lower limit Fmin is to have a buffering effect when controlling the motor frequency reduction of the compressor, so that the actual operating frequency of the motor after frequency reduction is greater than or equal to the frequency lower limit, so as to ensure that sufficient cooling capacity can be provided to the motor in the refrigerant cycle and prevent the motor from overheating.

[0080] In step S306, when the exhaust pressure is greater than the preset pressure value and the real-time operating frequency of the motor is less than or equal to Fmax-ΔF, it means that if the machine reduces the exhaust pressure by reducing the operating frequency of the motor, the refrigerant circulation volume may be reduced to a level that cannot meet the cooling needs of the motor, which may cause the motor to overheat. Therefore, in this step, when the real-time operating frequency of the motor is less than or equal to Fmax-ΔF, the operating frequency of the motor is not reduced, but the load of the first-level slide valve is directly reduced. For example, the third-level adjustable position of the slide valve is reduced to the second-level adjustable position, even if the compressor load is reduced from 100% to 75%, thereby reducing the load of the compressor. On the one hand, reducing the exhaust pressure of the compressor prevents the compressor from overheating. On the other hand, reducing the load of the compressor can also reduce the current of the motor, thereby reducing the heat generated by the motor and preventing the motor from overheating.

[0081] According to the second aspect of the present invention, a compressor is also provided. The compressor in this embodiment is a screw compressor, also known as a helical compressor. Figure 4 As shown, the compressor is used to implement the control method of the compressor as in the first aspect. The compressor includes a body, a screw, a slide valve 30, an inverter 20 and a motor 40, wherein the screw includes a female rotor and a male rotor that mesh with each other. The rotor with convex teeth in the pitch circle is called the male rotor (active rotor), which is connected to the motor, while the rotor with concave teeth in the pitch circle is called the female rotor (driven rotor), which is driven to rotate by the male rotor. The female rotor and the male rotor are arranged in parallel in the shell, and a series of closed spaces are formed between the female rotor and the male rotor. As the female rotor and the male rotor rotate, the gas is sucked in from the air intake of the shell and compressed in these closed spaces, and finally discharged through the exhaust port of the shell. The inverter is electrically connected to the motor and is used to adjust the operating frequency of the motor. The slide valve 30 is used to adjust the effective working length of the screw.

[0082] The compressor also includes: a pressure sensor 10 and a control device 60. The pressure sensor 10 is used to detect the exhaust pressure of the compressor, wherein the pressure sensor 10 includes but is not limited to a piezoresistive pressure sensor 10, a capacitive pressure sensor 10, etc., and can be connected to the exhaust end of the compressor via a pressure lead pipe. The pressure sensor 10 is installed on the pressure lead pipe, and the exhaust pressure is led to the sensor installation position through the pressure lead pipe to realize the measurement of the exhaust pressure of the compressor.

[0083] The control device 60 is electrically connected to the slide valve 30, the frequency converter 20, the pressure sensor 10 and the motor 40 respectively. The exhaust pressure data detected by the pressure sensor 10 is transmitted to the control device 60 in the form of an electrical signal. The control device 60 reduces the frequency of the motor 40 and / or unloads the slide valve 30 by controlling the frequency converter 20 according to the exhaust pressure being greater than the preset pressure value.

[0084] After receiving the exhaust pressure signal, the control device 60 calculates a control signal based on the exhaust pressure signal and outputs the control signal to a drive actuator connected to the spool valve 30, thereby driving the spool valve 30 to move. The drive actuator includes, but is not limited to, a linear motor 40, a hydraulic cylinder, or a pneumatic cylinder.

[0085] In some embodiments, the compressor also includes a displacement sensor 50 for detecting the current position of the slide valve 30. Specifically, the displacement sensor 50 includes, but is not limited to, a Hall effect sensor or an inductive displacement sensor. For example, a Hall effect sensor uses a magnet mounted on the slide valve 30. When the slide valve 30 moves, the magnet's magnetic field lines pass through the Hall element in the sensor, causing the resistance of the Hall element to change. The circuitry within the Hall effect sensor converts this resistance change into a voltage or current signal, which is then amplified and filtered to ultimately output a stable electrical signal. This electrical signal is proportional to the position of the slide valve 30, thereby enabling accurate position detection.

[0086] The displacement sensor 50 inputs the measured position information of the slide valve 30 into the control device 60 in the form of an electrical signal. The control device 60 obtains the real-time operating frequency of the motor 40 and obtains the frequency lower limit value corresponding to the current position of the motor 40 based on the current position of the slide valve 30. The control device 60 also controls the operating frequency of the motor 40 to decrease to the frequency lower limit value based on the exhaust pressure being greater than the preset pressure value and the real-time operating frequency being greater than the frequency lower limit value. The slide valve 30 is unloaded based on the exhaust pressure being greater than the preset pressure value and the real-time operating frequency being less than or equal to the frequency lower limit value.

[0087] In this embodiment, the control device 60 is used to obtain the rated frequency Fmax and the frequency reduction tolerance ΔF of the motor 40, Fmax-ΔF ≥ the frequency lower limit Fmin, and based on the exhaust pressure being greater than the pressure preset value and the real-time operating frequency being greater than Fmax-ΔF, control the operating frequency of the motor 40 to be reduced to Fmax-ΔF, and based on the exhaust pressure being greater than the pressure preset value and the real-time operating frequency being less than or equal to Fmax-ΔF, unload the slide valve 30.

[0088] In this embodiment, the control device 60 includes a memory 61 and at least one processor 62, wherein the memory 61 stores programs or instructions that can be run on the processor 62, and when the processor 62 executes the program or instruction, the steps of the compressor control method in this application are implemented.

[0089] According to an embodiment of the present invention, a HVAC equipment is also proposed, which includes a compressor. The HVAC equipment also includes a refrigerant circulation pipeline, an evaporator and a condenser. The compressor, evaporator and condenser are arranged in the refrigerant circulation pipeline in sequence. The compressor is used to drive the circulation flow of the refrigerant in the refrigerant circulation pipeline to achieve cooling using the evaporator or heating using the condenser.

[0090] According to an embodiment of the present invention, a computer storage medium is further provided, the computer storage medium storing computer-readable instructions. When executed by one or more processors, the computer-readable instructions cause the one or more processors to perform the compressor control method according to any embodiment of the present invention. The compressor control method may include, but is not limited to, at least one of the following steps: obtaining the exhaust pressure of the compressor; and, based on the exhaust pressure being greater than a preset pressure value, reducing the frequency of the motor and / or unloading the slide valve to reduce the load on the compressor.

[0091] The logic and / or steps represented in the flowcharts or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing the logical functions, and can be embodied in any computer-readable storage medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (e.g., a computer-based system, a system including a processor, or other system that can fetch and execute instructions from an instruction execution system, apparatus, or device). For purposes of this specification, a "computer-readable storage medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable storage media include the following: an electrical connection with one or more wires (electronic device), a portable computer disk cartridge (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM, or flash memory), a fiber optic device, and a portable compact disc read-only memory (CDROM). In addition, the computer-readable storage medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering, or processing in another suitable manner as necessary, and then stored in a computer memory.

[0092] It should be understood that various parts of the present invention can be implemented using hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used to implement the hardware: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0093] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for controlling a compressor, wherein the compressor comprises a screw, a slide valve, a frequency converter, and a motor, wherein the motor is connected to the screw in a transmission manner, the frequency converter is used to control the movement frequency of the motor, and the slide valve is used to adjust the effective working length of the screw, characterized in that: The compressor control method includes: obtaining the exhaust pressure of the compressor; reducing the frequency of the motor and / or unloading the slide valve according to the exhaust pressure being greater than a preset pressure value, so as to reduce the load of the compressor; Obtaining the real-time operating frequency of the motor and the current position of the slide valve; Obtaining a lower frequency limit value corresponding to the motor at the current position; Obtain the rated frequency Fmax and the frequency reduction tolerance ΔF of the motor, where Fmax-ΔF ≥ the frequency lower limit Fmin; The step of reducing the frequency of the motor and / or unloading the slide valve according to the exhaust pressure being greater than the preset pressure value comprises: According to the exhaust pressure being greater than the preset pressure value and the real-time operating frequency being greater than Fmax-ΔF, controlling the operating frequency of the motor to decrease to Fmax-ΔF; According to the exhaust pressure being greater than a preset pressure value and the real-time operating frequency being less than or equal to Fmax-ΔF, the slide valve is unloaded.

2. The compressor control method according to claim 1, characterized in that: The step of unloading the slide valve includes adjusting the position of the slide valve to reduce the effective working length of the screw.

3. The compressor control method according to claim 2, characterized in that: The slide valve includes multiple adjustable positions, each adjustable position corresponding to an effective working length of the screw; The step of adjusting the position of the slide valve to reduce the effective working length of the screw comprises: The sliding valve is controlled to adjust from the current nth adjustable position to the n-1th adjustable position, and the effective working length of the screw corresponding to the nth adjustable position is greater than the effective working length of the screw corresponding to the n-1th adjustable position, wherein n≥2.

4. The compressor control method according to claim 3, characterized in that: Each level of the adjustable position corresponds to a frequency lower limit value; The step of obtaining the lower limit value of the frequency corresponding to the motor at the current position includes: Obtain the lower limit value of the frequency of the motor at the nth level corresponding to the adjustable position at the nth level.

5. A compressor, used to implement the compressor control method according to any one of claims 1 to 4, characterized in that: The compressor includes a screw, a slide valve, a frequency converter and a motor, wherein the motor is connected to the screw in a transmission manner, the frequency converter is used to control the movement frequency of the motor, and the slide valve is used to adjust the effective working length of the screw; The compressor further comprises: a pressure sensor, configured to detect the exhaust pressure of the compressor; A control device is electrically connected to the slide valve, the frequency converter, the pressure sensor and the motor respectively. The control device is used to obtain the exhaust pressure of the compressor and reduce the frequency of the motor and / or unload the slide valve according to the exhaust pressure being greater than a preset pressure value.

6. The compressor according to claim 5, characterized in that The control device is further used to obtain the rated frequency Fmax and the frequency reduction tolerance ΔF of the motor, Fmax-ΔF ≥ the frequency lower limit Fmin, and control the operating frequency of the motor to be reduced to Fmax-ΔF based on the exhaust pressure being greater than the preset pressure value and the real-time operating frequency being greater than Fmax-ΔF, or to unload the slide valve based on the exhaust pressure being greater than the preset pressure value and the real-time operating frequency being less than or equal to Fmax-ΔF.

7. A HVAC equipment, characterized in that: The HVAC equipment includes the compressor according to any one of claims 5 to 6.

8. A computer storage medium, characterized in that The computer storage medium stores computer-readable instructions, and when the computer-readable instructions are read by one or more processors, the one or more processors are enabled to execute the compressor control method according to any one of claims 1 to 4.

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