Compressor control method, compressor, heating and ventilation equipment and computer storage medium

Abstract

The invention discloses a control method of a compressor, the compressor, heating and ventilation equipment and a computer storage medium, the compressor comprises a screw rod, a slide valve, a frequency converter and a motor, the frequency converter is used for controlling the motor to drive the screw rod, and the slide valve is used for adjusting the effective working length of the screw rod; the control method of the compressor comprises the steps of obtaining exhaust pressure of the compressor; and reducing the frequency of the motor and / or unloading the slide valve according to the condition that the exhaust pressure is greater than the preset pressure value to reduce the load of the compressor. According to the control method of the compressor, on one hand, the compressor can be prevented from being overheated, and on the other hand, the current of the motor is reduced by reducing the load of the compressor, so that the heating value of the motor is reduced, and the motor overheating fault is prevented.

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 also uses a sliding valve to adjust the effective working length of the compressor screw, so that the variable frequency screw compressor can achieve capacity regulation.

[0004] Under high load conditions, the compressor exhaust pressure is too high, causing the compressor motor to be limited by load. As the compressor is at a high load level, 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 the motor overheating failure may be caused by controlling the motor frequency reduction under high load conditions. This purpose is achieved by the following technical solutions:

[0006] A first aspect of the present invention proposes a control method for a compressor, wherein the compressor includes a screw, a sliding valve, a frequency converter and a motor, wherein the motor is drivingly 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 lower frequency 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 preset pressure value includes: controlling the operating frequency of the motor to be reduced to the lower frequency limit value according to the exhaust pressure being greater than the preset pressure value and the real-time operating frequency being greater than the lower frequency limit value; or 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 lower frequency limit value.

[0010] In some embodiments of the present invention, after the step of obtaining the lower frequency 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 lower frequency 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 lower frequency limit value; the step of obtaining the lower frequency limit value corresponding to the motor at the current position includes: obtaining the nth level lower frequency limit value corresponding to the motor and the nth level adjustable position; the step of controlling the operating frequency of the motor to be reduced to the lower frequency limit value includes: according to the slide valve being in the nth level adjustable position, controlling the operating frequency of the motor to be reduced to the nth level lower frequency 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, wherein the motor is drivingly 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 compressor also includes: a pressure sensor for detecting the exhaust pressure of the compressor; a control device, which is electrically connected to the sliding valve, the frequency converter, the pressure sensor and the motor respectively, and the control device is used to obtain the exhaust pressure of the compressor, and reduce the frequency of the motor and / or unload 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 according to the current position. The control device also controls 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, and unloads 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.

[0016] In some embodiments of the present invention, the control device is also used to obtain the rated frequency Fmax and the frequency reduction tolerance ΔF of the motor, Fmax-ΔF ≥ the frequency lower limit Fmin, and according to 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, according to 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, the HVAC equipment comprising 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 a 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 of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference numerals are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0020] Figure 1 A schematic flow chart of a compressor control method according to some embodiments of the present invention is schematically shown;

[0021] Figure 2 A schematic flow chart of a compressor control method according to some embodiments of the present invention is schematically shown;

[0022] Figure 3 A schematic flow chart of a compressor control method according to some embodiments of the present invention is schematically shown;

[0023] Figure 4 The block diagram of the control device and each device 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] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the 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. On the contrary, these embodiments are provided in order 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 only for the purpose of describing specific example embodiments 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 "include", "comprise", "contain", and "have" are inclusive, and therefore specify the existence of stated features, steps, operations, elements and / or parts, but do not exclude the existence 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 interpreted as necessarily requiring them to be performed in the specific order described or illustrated, unless the execution order 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, 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, spatial 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 figure, such as "inside", "outside", "inner side", "outer side", "below", "below", "above", "above", etc. Such spatial relative terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figure. For example, if the device in the figure is turned over, then the elements described as "below other elements or features" or "below other elements or features" will subsequently be oriented as "above other elements or features" or "above other elements or features". Therefore, the example term "below..." can include both upper and lower orientations. The device can be oriented otherwise (rotated 90 degrees or in other directions) and the spatial relative descriptors used in the text 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 running current of the motor will increase, and there is a risk of burning the motor. It also aggravates the consumption of lubricating oil in the compressor and makes it thinner, affecting the lubrication effect, and is accompanied by overheating of the compressor and excessive 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 above-mentioned various risks caused by the excessively high 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, so as to achieve the purpose of reducing the load of the compressor, on the one hand, to prevent the compressor from overheating, and 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.

[0040] It should be noted that the preset pressure value has different values ​​according to different models of compressors 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 frequency corresponding to the motor at 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 value, the operating frequency of the motor is controlled to be reduced to the frequency lower limit value;

[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 in detail herein.

[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 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 to reduce the frequency 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 situation, 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. In detail, the screw compressor compresses gas by reducing the working volume, and its core component is a pair of mutually meshing yin and yang rotors. In order to adjust the gas output of the compressor, a slide valve that can move axially is installed on the high-pressure side of the two rotors. The movement of the slide valve will change the effective working length of the screw, thereby affecting the gas output and energy efficiency of the compressor.

[0051] When the slide valve has not moved, its initial position makes the gas filling in the basic volume of the screw compressor maximum, and the compressor works at 100% load. As the slide valve moves toward the discharge end of the compressor, the effective working length of the screw decreases, the gas filling in the basic volume decreases, and the compressor output and load also decrease accordingly. Therefore, by obtaining the position of the slide valve, the current effective working length of the screw and the load state of the compressor can be obtained.

[0052] In step S203, the lower limit value 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 value of the frequency of the motor can be obtained based on the load state of the compressor.

[0053] The frequency lower limit refers to the minimum frequency value of the motor under the condition of ensuring sufficient refrigerant circulation to cool the motor based on the load state of the compressor. It is understandable that if the motor's operating frequency is lower than the frequency lower limit after the motor's frequency lower limit is determined, sufficient refrigerant circulation cannot be ensured to cool the motor, thereby causing an overheating fault of the motor.

[0054] Among them, the specific numerical value of the frequency lower limit is measured by experimental simulation of the same model compressor or the same compressor, and the frequency lower limit data corresponding to the load state of multiple compressors are established when the compressor is under different load states. The load state of the compressor corresponds 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 limits can be established, that is, each position of the slide valve has a frequency lower limit 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. When the real-time operating frequency of the motor is greater than the lower frequency limit, it means that the compressor can maintain sufficient refrigerant circulation volume to cool 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 is still greater than the preset pressure value after the operating frequency of the control motor is reduced to the frequency lower limit and the preset time is run, the step of unloading the slide valve is performed. The preset time can be set to any time period, 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 the frequency lower 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 lower frequency limit. If the machine reduces the exhaust pressure by reducing the operating frequency of the motor, it will inevitably lead to a reduction in the refrigerant circulation volume to a level that cannot meet the cooling 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 lower frequency limit, the operating frequency of the motor 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, the exhaust pressure of the compressor is reduced to prevent 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.

[0058] In some embodiments, the slide valve includes multiple adjustable positions, and each adjustable position of the slide valve corresponds to an effective working length of a screw, so that the compressor can switch between multiple load states. For example, in an exemplary embodiment, the slide valve includes three adjustable positions, namely the first level, the second level and the third level. The third adjustable position is the initial position of the slide valve, at which time the effective working length of the screw corresponding to the slide valve is the largest, and the load of the compressor 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 load of the compressor is 75%, and 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 load of the compressor is 50%.

[0059] Furthermore, the process of unloading the slide valve refers to adjusting the third-level adjustable position of the slide valve to the second-level adjustable position, or adjusting the second-level adjustable position of the slide valve to the first-level 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, five, six, 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 the lower limit value of the frequency corresponding to the position of the motor and the slide valve includes: obtaining the lower limit value of the nth level 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 a frequency lower limit value includes: according to the slide valve being in an nth adjustable position, controlling the operating frequency of the motor to decrease to an nth frequency lower limit value.

[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. Taking the multi-level adjustable position including two adjustable positions as an example, the first adjustable position corresponds to 50% of the compressor load, and the second adjustable position corresponds to 100% of the compressor load.

[0064] The first frequency lower limit value corresponds to the case of 50% load of the compressor. Based on the 50% load state of the compressor, the first frequency lower limit value is the minimum frequency value for ensuring sufficient refrigerant circulation to meet the motor operation in the motor cooling state. Understandably, when the compressor is in the 50% load state, if the motor operating frequency is lower than the first frequency lower limit value, it cannot ensure sufficient refrigerant circulation to meet the motor cooling state, thereby causing the motor to overheat. Therefore, when the compressor is in the 50% load state, the motor operating frequency needs to be controlled to be greater than or equal to the first frequency lower limit value to prevent the motor from overheating.

[0065] The second frequency lower limit value corresponds to the case where the compressor load is 100%. Based on the 100% load state of the compressor, the second frequency lower limit value is the minimum frequency value for ensuring sufficient refrigerant circulation to meet the motor operation in the motor cooling state. Understandably, when the compressor is in the 100% load state, if the motor operating frequency is lower than the second frequency lower limit value, it cannot ensure sufficient refrigerant circulation to meet the motor cooling state, thereby causing the motor overheating fault. Therefore, when the compressor is in the 100% load state, the motor operating frequency needs to be controlled to be greater than or equal to the second frequency lower limit value to prevent the motor from overheating.

[0066] Therefore, in this embodiment, the step of controlling the operating frequency of the motor to be reduced to the lower frequency limit 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 frequency lower limit, while 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 in a wider 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: obtaining 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 frequency corresponding to the motor at the current position;

[0071] Step S304: obtaining the rated frequency Fmax and the frequency reduction tolerance ΔF of the motor, 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 be reduced 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 described in detail herein.

[0075] In step S304, the frequency reduction tolerance ΔF is a buffer frequency value obtained by experimental simulation of a compressor sample. Different frequency reduction tolerances ΔF can be set according to compressors with different rated frequencies. The larger the rated frequency of the compressor, the larger the value of the frequency reduction tolerance. For example, for a compressor with a rated frequency of 50HZ, the frequency reduction tolerance ΔF can be set to 5HZ, and for a compressor with a rated frequency of 60HZ, the frequency reduction tolerance ΔF can be set to 8HZ. In the present application, the value of the frequency reduction tolerance ΔF can take any value in [0HZ, 10HZ]. For example, the frequency reduction tolerance ΔF can be set to 1HZ, 2HZ, 4HZ, 5HZ, 6HZ, 7HZ, 8HZ, 9HZ, 10HZ, 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 is still greater than the preset pressure value after the operating frequency of the control motor is reduced to Fmax-ΔF and the preset time is run, the step of unloading the slide valve is performed. The preset time can be set to any time period, 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 cool the motor when operating at any operating frequency in 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≥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 during 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 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 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 a 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 in the first aspect, and the compressor includes a body, a screw, a slide valve 30, a frequency converter 20 and a motor 40, wherein the screw includes a female rotor and a male rotor meshing 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 by transmission, and 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 from the air intake port of the shell and compressed in these closed spaces, and finally discharged through the exhaust port of the shell. The frequency converter is electrically connected to the motor and is used to adjust the operating frequency of the motor, and 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. 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 achieve 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 according to the exhaust pressure signal, outputs the control signal to a driving actuator that is transmission-connected to the slide valve 30, and uses the driving actuator to drive the slide valve 30 to move. The driving actuator includes but is not limited to a linear motor 40, a hydraulic cylinder, or a pneumatic cylinder.

[0085] In some embodiments, the compressor further includes a displacement sensor 50, which is used to detect the current position of the slide valve 30. Specifically, the displacement sensor 50 includes but is not limited to a Hall position sensor and an inductive displacement sensor 50. Taking the Hall position sensor as an example, a magnet is installed on the slide valve 30. When the slide valve 30 moves, the magnetic lines of force of the magnet pass through the Hall element in the Hall position sensor, causing the resistance of the Hall element to change. The circuit inside the Hall position sensor converts this resistance change into a voltage or current signal, and after amplification and filtering, it finally outputs a stable electrical signal. This electrical signal is proportional to the position of the slide valve 30, thereby realizing the detection of the position of the slide valve 30.

[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 according to the current position of the slide valve 30. The control device 60 also controls the operating frequency of the motor 40 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, and unloads the slide valve 30 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.

[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 according to the exhaust pressure being greater than the pressure preset value and the real-time operating frequency being greater than Fmax-ΔF, the operating frequency of the motor 40 is controlled to be reduced to Fmax-ΔF, and according to the exhaust pressure being greater than the pressure preset value and the real-time operating frequency being less than or equal to Fmax-ΔF, the slide valve 30 is unloaded.

[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, the evaporator and the 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, on which computer readable instructions are stored, and when the computer readable instructions are executed by one or more processors, the one or more processors execute the compressor control method in 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; reducing the frequency of the motor and / or unloading the slide valve according to the exhaust pressure being greater than the preset pressure value to reduce the load of the compressor.

[0091] The logic and / or steps represented in the flowchart or otherwise described herein, for example, may be considered as an ordered list of executable instructions for implementing logical functions, and may be embodied in any computer-readable storage medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, apparatus, or device and execute instructions), or in conjunction with such instruction execution system, apparatus, or device. For purposes of this specification, a "computer-readable storage medium" may be any device that can contain, store, communicate, propagate, or transmit a program for use by an instruction execution system, apparatus, or device, or in conjunction with such instruction execution system, apparatus, or device. More specific examples of computer-readable storage media (a non-exhaustive list) include the following: an electrical connection with one or more wirings (electronic devices), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM, Erasable Programmable Read-Only Memory, or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM, Compact Disc Read-Only Memory). In addition, the computer-readable storage medium may even be a 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 the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiment, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA, Programmable Gate Array), a field programmable gate array (FPGA, Field Programmable Gate Array), etc.

[0093] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A control method for a compressor, the compressor comprising a screw, a slide valve, a frequency converter and a motor, the motor is drivingly connected to the screw, 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 control method of the compressor comprises: Obtaining the exhaust pressure of the compressor; According to the exhaust pressure being greater than a preset pressure value, the frequency of the motor is reduced and / or the slide valve is unloaded to reduce the load of the compressor.

2. The compressor control method according to claim 1, characterized in that: The compressor control method further comprises: Acquiring the real-time operating frequency of the motor and the current position of the slide valve; Obtaining a 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 a 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 the frequency lower limit value, controlling the operating frequency of the motor to decrease to the frequency lower limit value; Alternatively, the slide valve is unloaded according to the exhaust pressure being greater than a preset pressure value and the real-time operating frequency being less than or equal to the frequency lower limit value.

3. The compressor control method according to claim 2, characterized in that: After the step of obtaining the lower limit value of the frequency corresponding to the motor at the current position, the step further includes: Obtain the rated frequency Fmax and the frequency reduction tolerance ΔF of the motor, 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 a 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.

4. The compressor control method according to claim 2 or 3, 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.

5. The method for controlling a compressor according to claim 4, 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 slide valve is controlled 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.

6. The method for controlling a compressor according to claim 5, 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: Obtaining the lower limit value of the frequency at the nth level corresponding to the motor and the adjustable position at the nth level; The step of controlling the operating frequency of the motor to decrease to the frequency lower limit value includes: controlling the operating frequency of the motor to decrease to the frequency lower limit value of the nth level according to the slide valve being in the nth level of the adjustable position.

7. A compressor, used to implement the compressor control method according to any one of claims 1 to 6, characterized in that: The compressor comprises a screw, a slide valve, a frequency converter and a motor, wherein the motor is drivingly connected to the screw, 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 also includes: A pressure sensor, used 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, and 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.

8. The compressor according to claim 7, characterized in that 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 according to the current position. The control device also controls the operating frequency of the motor to be reduced to the frequency lower limit value 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 value, and unloads 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.

9. The compressor according to claim 8, characterized in that The control device is also 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 according to the exhaust pressure being greater than the preset pressure value and the real-time operating frequency being greater than Fmax-ΔF, or unload 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.

10. A HVAC equipment, characterized in that: The HVAC equipment comprises the compressor according to any one of claims 7 to 9.

11. 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 execute the compressor control method according to any one of claims 1 to 6.

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