Control method of LBV valve, refrigerating unit and storage medium

Abstract

The invention provides a control method of an LBV valve, a refrigerating unit and a storage medium, and relates to the field of refrigeration. The actual load and the required load of a compressor in the refrigerating unit are obtained; and when the actual load is larger than the required load, the flow characteristic curve of the LBV and the actual mass flow and the required mass flow of the compressor are obtained, so that the opening degree of the LBV is adjusted, and the adjusting time is more accurate. And the target bypass flow of the LBV valve is determined according to the flow difference value of the required mass flow and the actual mass flow. And the target valve opening degree is determined according to the target bypass flow and the flow characteristic curve, the opening degree of the LBV valve is adjusted to be the target valve opening degree, on one hand, the refrigeration requirement is met, and on the other hand, compressor surge is avoided. Due to the fact that the flow characteristic curve has continuity, the valve opening degree is adjusted according to the flow characteristic curve and the target bypass flow, adjustment of the valve opening degree is smoother, and then the compressor works more stably.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of refrigeration, and particularly to a control method of an LBV valve, a refrigeration unit and a storage medium. BACKGROUND

[0002] When the compressor in the refrigeration unit is running at low load, the actual mass flow of the compressor is relatively low, which may cause surge, leading to unstable operation of the compressor and even damage. Therefore, an LBV valve (Load balance valve) is provided in the compressor to increase the actual mass flow of the compressor by opening the LBV valve to avoid surge.

[0003] Currently, whether the compressor is running at low load is determined by reading the minimum capacity flag of the compressor. When the minimum capacity flag is the flag corresponding to the minimum capacity of the compressor, the LBV valve is controlled by PI (Proportional-Integral) according to the difference between the actual outlet water temperature and the target outlet water temperature of the refrigeration unit. The PI control corresponds to multiple preset difference ranges, and the valve opening degree corresponding to each preset difference range is different.

[0004] On the one hand, the minimum capacity flag of the compressor has hysteresis, which is not stable and accurate enough, resulting in inaccurate timing of adjusting the opening degree of the LBV valve. On the other hand, adjusting the opening degree of the LBV valve according to the framed preset difference ranges lacks flexibility and continuity, and the control of the LBV valve is not smooth, which easily causes fluctuations in the working state of the compressor. SUMMARY

[0005] Therefore, the present application provides a control method of an LBV valve, which comprises: obtaining the actual load and the demand load of the compressor in the refrigeration unit; the demand load being a load determined according to the refrigeration demand of the refrigeration unit; when the actual load is greater than the demand load, obtaining the flow characteristic curve of the LBV valve, the actual mass flow and the demand mass flow of the compressor; the flow characteristic curve being used to represent the corresponding relationship between flow and valve opening degree; determining the target bypass flow of the LBV valve according to the flow difference between the demand mass flow and the actual mass flow; determining the target valve opening degree based on the target bypass flow and the flow characteristic curve, and adjusting the opening degree of the LBV valve to the target valve opening degree.

[0006] Optionally, the method of determining the target valve opening degree based on the target bypass flow and the flow characteristic curve comprises: The flow equal to the target bypass flow in the flow characteristic curve is taken as a target flow, and a valve opening degree corresponding to the target flow is taken as an initial valve opening degree; determining whether the demand load is less than a minimum load of the compressor; the minimum load is a minimum value of a load required for the compressor to maintain a running state; if yes, obtaining a last opening degree increment of the LBV valve, and taking a sum of the last opening degree increment and a first preset opening degree increment as a current opening degree increment; taking a sum of the current opening degree increment and the initial valve opening degree as the target valve opening degree; if no, taking the initial valve opening degree as the target valve opening degree.

[0007] Optionally, after the opening degree of the LBV valve is adjusted to the target valve opening degree, the method further comprises: obtaining a surge early warning index; the surge early warning index comprises at least one of a unit pressure ratio and a bearing displacement of a magnetic suspension bearing in the compressor; the unit pressure ratio is a ratio of a condenser pressure to an evaporator pressure of the refrigeration unit; determining whether the surge early warning index meets a trigger condition of surge protection; if yes, taking a first preset valve opening degree as a surge protection valve opening degree; if no, obtaining a last surge protection valve opening degree every interval of a preset period, and taking a difference obtained by subtracting a second preset opening degree increment from the last surge protection valve opening degree as the surge protection valve opening degree, until the surge protection valve opening degree reaches a minimum threshold; after the surge protection valve opening degree is determined, adjusting the opening degree of the LBV valve to a maximum opening degree of the surge protection valve opening degree and the target valve opening degree.

[0008] Optionally, the surge early warning index comprises the unit pressure ratio, and the determining whether the surge early warning index meets the trigger condition of surge protection comprises: determining a pressure ratio change characteristic parameter according to the unit pressure ratio; the pressure ratio change characteristic parameter is used to represent a change degree of the ratio of the condenser pressure to the evaporator pressure of the refrigeration unit; the pressure ratio change characteristic parameter is positively correlated with the change degree; if the pressure ratio change characteristic parameter is greater than a first preset parameter, it is determined that the trigger condition is met; if the pressure ratio change characteristic parameter is not greater than the first preset parameter, it is determined that the trigger condition is not met.

[0009] Optionally, the surge early warning index comprises the bearing displacement, and the determining whether the surge early warning index meets the trigger condition of surge protection comprises: Displacement characteristic parameters are determined based on the bearing displacement; the displacement characteristic parameters are positively correlated with the bearing displacement. If the displacement characteristic parameter is greater than the second preset parameter, then the triggering condition is determined to be met; If the displacement characteristic parameter is not greater than the second preset parameter, then the triggering condition is determined not to be met.

[0010] Optionally, the method further includes: Upon receiving a shutdown signal, the opening degree of the LBV valve is adjusted to the second preset valve opening degree; Obtain the condenser pressure and evaporator pressure of the refrigeration unit; When the pressure difference between the condenser pressure and the evaporator pressure is less than the pressure balance value, or when the pressure balance time is greater than a preset time, the LBV valve is closed; the pressure balance time is the duration for which the LBV valve is opened to the second preset valve opening. Control the refrigeration unit to stop.

[0011] Optionally, the method further includes: Upon receiving a start signal, the evaporator inlet water temperature and the condenser inlet water temperature of the refrigeration unit are acquired. Determine the absolute value of the temperature difference between the evaporator inlet water temperature and the condenser inlet water temperature; If the absolute value is greater than the temperature difference threshold, the opening of the LBV valve is adjusted to the third preset valve opening, and the refrigeration unit is started. If the absolute value is not greater than the temperature difference threshold, then the LBV valve is closed and the refrigeration unit is started.

[0012] Optionally, after determining the target valve opening based on the target bypass flow rate and the flow characteristic curve, the method further includes: Obtain the preset opening limit value and the previous valve opening value; The sum of the opening limit value and the previous valve opening is used as the upper boundary value of the target opening range, and the difference between the previous valve opening and the opening limit value is used as the lower boundary value of the target opening range. If the target valve opening is greater than the upper boundary value, then the upper boundary value is taken as the final valve opening. If the target valve opening is less than or equal to the upper boundary value and greater than or equal to the lower boundary value, then the target valve opening is taken as the final valve opening. If the target valve opening is less than the lower boundary value, then the lower boundary value is taken as the final valve opening. Correspondingly, adjusting the opening degree of the LBV valve to the target valve opening degree includes: Adjust the opening degree of the LBV valve to the final valve opening degree.

[0013] This application also provides a refrigeration unit, the unit comprising: Memory, used to store computer programs; A processor, used to implement the steps of any of the above-described LBV valve control methods when executing the computer program.

[0014] This application also provides a storage medium storing a computer program, which, when executed by a processor, implements the steps of any of the above-described LBV valve control methods.

[0015] In summary, this application provides a control method for an LBV valve, a refrigeration unit, and a storage medium. The method includes acquiring the actual load and demand load of the compressor in the refrigeration unit; when the actual load exceeds the demand load, acquiring the flow characteristic curve of the LBV valve, the actual mass flow rate of the compressor, and the demand mass flow rate, in order to adjust the opening of the LBV valve more precisely. Based on the flow difference between the demand mass flow rate and the actual mass flow rate, the target bypass flow rate of the LBV valve is determined. Based on the target bypass flow rate and the flow characteristic curve, the target valve opening is determined, and the opening of the LBV valve is adjusted to the target valve opening, thus satisfying the refrigeration demand while preventing compressor surge. Because the flow characteristic curve is continuous, adjusting the valve opening based on the flow characteristic curve and the target bypass flow rate makes the valve opening adjustment smoother, thereby making the compressor operation more stable. Attached Figure Description

[0016] Figure 1 A first flow diagram of a control method for an LBV valve provided in this application; Figure 2 A schematic diagram illustrating the principle of a control method for an LBV valve provided in this application; Figure 3 This application provides a second flow diagram of a control method for an LBV valve. Figure 4 A third flow diagram of a control method for an LBV valve provided in this application; Figure 5 This is a structural schematic diagram of a refrigeration unit provided in this application. Detailed Implementation

[0017] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0018] Please refer to Figure 1 , Figure 1 A first flow diagram of a control method for an LBV valve provided in this application is shown. The method includes: S101. Obtain the actual load and demand load of the compressor in the refrigeration unit; the demand load is the load determined based on the refrigeration demand of the refrigeration unit.

[0019] The actual load of the compressor is the actual cooling capacity output by the compressor during operation. Specific methods for determining the actual load include, but are not limited to, using the condenser heat balance method based on the heat dissipation of the condenser in the refrigeration unit; or using the power back-calculation method based on the compressor's input power, etc. This application does not impose any particular limitations on these methods.

[0020] The compressor's demand load is the cooling capacity that the compressor needs to provide to meet the user's cooling needs. This application does not specify a particular method for determining the demand load; for example, it may determine the temperature difference between the actual outlet water temperature of the chiller unit and the cooling temperature required by the user, and then determine the demand load based on the temperature difference.

[0021] S102. When the actual load is greater than the demand load, obtain the flow characteristic curve of the LBV valve, the actual mass flow rate of the compressor, and the demand mass flow rate; the flow characteristic curve is used to characterize the correspondence between flow rate and valve opening.

[0022] On the one hand, if the actual load of the compressor is greater than the demand load, it means that the actual cooling capacity provided by the compressor is greater than the required cooling capacity, i.e., the compressor's cooling capacity is excessive, which may cause the actual ambient temperature to be lower than the cooling temperature required by the user. Therefore, it is necessary to open the LBV valve to provide a virtual load to the compressor, reduce the effective cooling capacity of the compressor, and ensure that the actual ambient temperature meets the cooling temperature required by the user.

[0023] On the other hand, if the actual load of the compressor is greater than the demand load, it indicates that the current demand load is low. When the compressor operates at a low load, its actual mass flow rate is relatively low, which can cause compressor surge, leading to unstable compressor operation or even damage. Therefore, it is necessary to open the LBV valve to increase the actual mass flow rate of the compressor, thereby avoiding compressor surge and ensuring compressor safety.

[0024] To achieve smooth control of the LBV valve opening and avoid fluctuations in compressor operating conditions, this application utilizes a continuous flow characteristic curve to determine the LBV valve opening. The LBV valve flow characteristic curve characterizes the correspondence between the LBV valve flow rate and the valve opening. When determining the target valve opening corresponding to the LBV valve using the flow characteristic curve, it is necessary to first determine the target bypass flow rate of the LBV valve. Therefore, this application also obtains the compressor's actual mass flow rate and required mass flow rate.

[0025] The actual mass flow rate of the compressor refers to the mass of refrigerant actually flowing through the compressor per unit time. The actual mass flow rate can be obtained directly by reading the mass flow meter installed in the compressor. The required mass flow rate of the compressor refers to the mass of refrigerant that the compressor needs to deliver per unit time to meet current cooling demand. The required mass flow rate can be determined using a heat balance calculation formula; alternatively, it can be determined by a pre-built compressor simulation model based on the actual load, required load, suction saturation temperature, and discharge saturation temperature. This application does not impose any particular limitation on this.

[0026] Furthermore, for situations where the actual demand is not greater than the demand load, this application does not impose any special restrictions on the state of the LBV valve, such as controlling the LBV valve to be closed.

[0027] S103. Determine the target bypass flow rate of the LBV valve based on the flow rate difference between the required mass flow rate and the actual mass flow rate.

[0028] After obtaining the actual and required mass flow rates of the compressor, the target bypass flow rate of the LBV valve can be determined based on the difference between the two. For example, the difference between the actual and required mass flow rates can be used as the flow difference; the flow difference, or the product of the flow difference and a preset coefficient, can be used as the target bypass flow rate. The preset coefficient is greater than 1, and its specific value can be set according to actual needs. Using the product of the flow difference and the preset coefficient as the target bypass flow rate helps to quickly meet the user's cooling temperature requirements and improves the prevention of compressor surge.

[0029] S104. Based on the target bypass flow rate and flow characteristic curve, determine the target valve opening and adjust the LBV valve opening to the target valve opening.

[0030] After determining the target bypass flow rate of the LBV valve, the target valve opening can be determined based on the flow characteristic curve. For example, the flow rate on the flow characteristic curve that equals the target bypass flow rate can be identified, and the valve opening corresponding to that flow rate can be used as the target valve opening. After determining the target valve opening, the LBV valve opening can be adjusted to the target valve opening to meet the user's cooling needs, avoid compressor surge, and ensure compressor safety.

[0031] Therefore, the LBV valve control method provided in this application determines the timing of opening the LBV valve by judging whether the actual load of the compressor is greater than the demand load, resulting in more precise control timing. Furthermore, the target bypass flow rate of the LBV valve is determined based on the flow difference between the actual mass flow rate and the demand mass flow rate of the compressor; and the target valve opening is determined based on the target bypass flow rate and the continuous flow characteristics, making the adjustment of the LBV valve opening smoother, thereby making the compressor operation more stable.

[0032] Based on the above embodiments: The process of determining the target valve opening is explained in detail below.

[0033] As an optional embodiment, the target valve opening is determined based on the target bypass flow rate and flow characteristic curve, including: The flow rate that is equal to the target bypass flow rate in the flow characteristic curve is taken as the target flow rate, and the valve opening corresponding to the target flow rate is taken as the initial valve opening. Determine whether the demand load is less than the compressor's minimum load; the minimum load is the minimum load required for the compressor to maintain operation. If so, obtain the previous opening increment of the LBV valve, and use the sum of the previous opening increment and the first preset opening increment as the current opening increment; use the sum of the current opening increment and the initial valve opening as the target valve opening. If not, the initial valve opening will be used as the target valve opening.

[0034] As mentioned earlier, the flow characteristic curve of the LBV valve is used to characterize the relationship between the flow rate and the valve opening. Therefore, in this embodiment, the flow rate that is equal to the target bypass flow rate in the flow characteristic curve is taken as the target flow rate, and the valve opening corresponding to the target flow rate in the flow characteristic curve is taken as the initial valve opening, which serves as the basis for subsequently determining the target valve opening.

[0035] In this embodiment, the minimum load of the compressor is also pre-acquired. The minimum load is the minimum load required for the compressor to maintain its operating state. As mentioned earlier, when the actual load of the compressor is greater than the demand load, it indicates that the current demand load is relatively low, and the compressor faces the risk of entering a low-load operating state. Therefore, the LBV valve needs to be opened to avoid compressor surge. In this embodiment, it is further determined whether the demand load is less than the minimum load. If the demand load is less than the minimum load, the risk of compressor surge is higher, and the opening of the LBV valve needs to be increased to ensure the safety of the compressor. If the demand load is not less than the minimum load, the initial valve opening is used as the target valve opening to ensure the safe operation of the compressor.

[0036] Therefore, for situations where the demand load is less than the minimum load, this embodiment will add the current opening increment to the initial valve opening to increase the LBV valve opening and minimize compressor surge. The aforementioned current opening increment is obtained by adding a first preset opening increment to the previous opening increment. This embodiment does not limit the value of the first preset opening increment and can set it according to actual needs; for example, the first preset opening increment can be set to 5%.

[0037] It is understood that the LBV valve control method provided in this application embodiment can be executed once at preset time intervals, and the value of the preset time interval can be adjusted according to actual needs. When the LBV valve control method provided in this embodiment is executed for the first time and it is determined that the demand load is less than the minimum load, the value of the previous opening increment is zero, and the current opening increment is the first preset opening increment. During the Nth execution (N greater than or equal to 2), if the demand load is still less than the minimum load, the current opening increment is the previous opening increment plus the first preset opening increment, that is, the current opening increment is N times the first preset opening increment; if the demand load is not less than the minimum load, the previous opening increment can be regarded as zero, and the initial valve opening can be directly used as the target valve opening.

[0038] In summary, this embodiment further determines the specific method for calculating the target valve opening based on the judgment result of whether the demand load is less than the minimum load. When the demand load is less than the minimum load, the LBV valve opening is increased by adding the current opening increment to the initial valve opening, thus avoiding compressor surge and ensuring compressor safety. When the demand load is not less than the minimum load, the initial valve opening is used as the target valve opening; this method is simple, reliable, and ensures the stability of the compressor's operating state.

[0039] This application also utilizes surge warning indicators to protect the compressor from surge, further ensuring the compressor's safety. The surge protection process is described in detail below.

[0040] As an optional embodiment, after adjusting the opening degree of the LBV valve to the target valve opening degree, the method further includes: Obtain surge warning indicators; surge warning indicators include at least one of the unit pressure ratio and the bearing displacement of the magnetic levitation bearing in the compressor; the unit pressure ratio is the ratio of the condenser pressure to the evaporator pressure of the refrigeration unit; Determine whether the surge warning indicators meet the triggering conditions for surge protection; If so, the first preset valve opening will be used as the surge protection valve opening. If not, then at each preset interval, obtain the previous surge protection valve opening, and use the difference between the previous surge protection valve opening and the second preset opening increment as the surge protection valve opening, until the surge protection valve opening reaches the minimum threshold. After determining the surge protection valve opening, adjust the LBV valve opening to the maximum of the surge protection valve opening and the target valve opening.

[0041] For refrigeration units, both the unit pressure ratio and compressor load are factors influencing compressor surge. When a refrigeration unit experiences a sudden increase in condenser pressure or a sharp drop in evaporator pressure within a short period, the unit pressure ratio rises instantaneously. When the unit pressure ratio exceeds a certain range, compressor surge will occur. Therefore, this embodiment uses the refrigeration unit pressure ratio as one of the surge warning indicators.

[0042] This embodiment also considers that when the compressor experiences surge, the airflow fluctuations caused by the surge will trigger displacement fluctuations in the magnetic levitation bearing within the compressor. Therefore, this embodiment also uses the bearing displacement of the magnetic levitation bearing as a surge warning indicator. It should be noted that the aforementioned bearing displacement refers to FROD (Front Radial Orbit Displacement), which is the sum of the squares of the horizontal and vertical displacements of the magnetic levitation bearing.

[0043] Based on the above, this embodiment, after adjusting the LBV valve opening to the target valve opening, further acquires surge warning indicators to determine whether surge has occurred. Specifically, corresponding trigger conditions are preset for the unit pressure ratio and bearing displacement. If the surge warning indicator meets the corresponding trigger conditions, it is considered that the compressor has surged, and surge protection of the compressor is required. Subsequent embodiments will describe in detail the trigger conditions corresponding to the unit pressure ratio and bearing displacement, which will not be repeated here.

[0044] If the surge warning index meets the triggering conditions for surge protection, the first preset valve opening is directly used as the surge protection valve opening. The value of the first preset valve opening can be set according to actual needs, and this embodiment does not impose any special limitations on it. For example, the first preset valve opening can be set to 50%.

[0045] If the surge warning indicators do not meet the surge protection trigger conditions, it indicates that the compressor has no risk of surge and is in a stable operating state, therefore surge protection can be deactivated. Furthermore, to avoid drastic changes in the LBV valve opening that could cause fluctuations in the compressor's operating state, this embodiment will gradually reduce the LBV valve opening, that is, gradually reduce the surge protection valve opening, until the surge protection valve opening is reduced to the minimum threshold. The value of the minimum threshold can also be set according to actual needs, and this embodiment does not impose any special limitations on it. For example, the minimum threshold can be set to 0.1%.

[0046] The process of gradually reducing the surge protection valve opening is described below. If the surge warning index is determined not to meet the surge protection triggering conditions, the previous surge protection valve opening is obtained at preset intervals. A second preset opening increment is then subtracted from the previous surge protection valve opening, and the difference is used as the current surge protection valve opening. This embodiment does not impose specific limitations on the preset interval and the second preset opening increment; they can be set according to actual needs. For example, to gradually reduce the surge protection valve opening over a specified time period, the quotient obtained by dividing the first preset valve opening by the specified time period is used as the second preset opening increment.

[0047] It should also be noted that, as mentioned above, the unit pressure ratio, bearing displacement, and compressor load are all related to compressor surge. Therefore, in this embodiment, after determining the surge protection valve opening each time, the current surge protection valve opening is compared with the target valve opening. The LBV valve opening is then adjusted to the maximum of the surge protection valve opening and the target valve opening, thus determining the optimal opening that can minimize compressor surge and ensure the safe operation of the compressor.

[0048] As an optional embodiment, the surge warning index includes the unit pressure ratio. Determining whether the surge warning index meets the triggering conditions for surge protection includes: The pressure ratio variation characteristic parameter is determined based on the unit's pressure ratio; the pressure ratio variation characteristic parameter is used to characterize the degree of change in the ratio of the condenser pressure to the evaporator pressure of the refrigeration unit; the pressure ratio variation characteristic parameter is positively correlated with the degree of change; If the characteristic parameter of the pressure ratio change is greater than the first preset parameter, then the triggering condition is determined to be met; If the characteristic parameter of pressure ratio change is not greater than the first preset parameter, then the triggering condition is determined not to be met.

[0049] Please refer to Figure 2 , Figure 2 This is a schematic diagram illustrating the principle of a control method for an LBV valve provided in this application. Figure 2As shown, in this embodiment, based on the unit pressure ratio, a pressure ratio change characteristic parameter is determined to characterize the range of pressure ratio change, and the pressure ratio change characteristic parameter is used as the basis for triggering surge protection.

[0050] This embodiment does not specifically limit the method for determining the characteristic parameters of pressure ratio change. For example, according to a preset time step, the condenser pressure and evaporator pressure are collected at 10 consecutive time points, and the unit pressure ratio corresponding to each time point is determined. Then, the pressure ratio difference between the first unit at the first time point and the fifth unit at the fifth time point is determined; the pressure ratio difference between the second unit at the second time point and the sixth unit at the sixth time point is determined; the pressure ratio difference between the third unit at the third time point and the seventh unit at the seventh time point is determined; and so on, to obtain the pressure ratio difference for the fourth and fifth units. Then, the average value of the pressure ratio differences of each unit is determined, that is, the average unit pressure ratio difference is determined. Finally, the average unit pressure ratio difference is divided by the interval time to obtain the characteristic parameters of pressure ratio change. The interval duration is the time between the first and fifth time points, and its specific value is related to the preset time step.

[0051] In this embodiment, the pressure ratio change characteristic parameter is positively correlated with the degree of change in the unit pressure ratio. Therefore, this embodiment determines whether the unit pressure ratio meets the surge protection trigger condition by judging whether the pressure ratio change characteristic parameter is greater than a first preset parameter. If the pressure ratio change characteristic parameter is greater than the first preset parameter, it indicates that the unit pressure ratio change is large, which may cause surge, and therefore it is determined that the surge protection trigger condition is met at this time; conversely, it indicates that the possibility of the compressor surging is small, and the surge protection trigger condition is not met.

[0052] As an optional embodiment, the surge warning index includes bearing displacement. Determining whether the surge warning index meets the triggering conditions for surge protection includes: The displacement characteristic parameters are determined based on the bearing displacement; the displacement characteristic parameters are positively correlated with the bearing displacement. If the displacement characteristic parameter is greater than the second preset parameter, then the triggering condition is determined to be met; If the displacement characteristic parameter is not greater than the second preset parameter, then the triggering condition is not met.

[0053] When a compressor experiences surge, the resulting airflow fluctuations can cause displacement fluctuations in the magnetic bearings within the compressor. Therefore, as... Figure 2 As shown, in this embodiment, displacement characteristic parameters that are positively correlated with bearing displacement are determined based on bearing displacement, and these displacement characteristic parameters are used as the basis for triggering surge protection.

[0054] This embodiment does not impose any particular limitation on the specific implementation method for determining the displacement characteristic parameters. For example, the bearing displacement of the magnetic levitation bearing in the compressor can be collected at a preset number of time points; the average value of each bearing displacement can be used as the displacement characteristic parameter.

[0055] In this embodiment, the displacement characteristic parameter of the magnetic levitation bearing is positively correlated with the bearing displacement. Furthermore, as mentioned earlier, the airflow caused by surge will cause fluctuations in the displacement of the magnetic levitation bearing. The more severe the surge, the more pronounced the displacement of the magnetic levitation bearing, and correspondingly, the larger the displacement characteristic parameter. Therefore, this embodiment determines whether the surge protection trigger condition is met by judging whether the displacement characteristic parameter is greater than a second preset parameter. This embodiment does not particularly limit the value of the second preset parameter and can set it differently according to the type of compressor.

[0056] In summary, in this embodiment, the displacement characteristic parameters of the magnetic levitation bearing are used as the basis for triggering surge protection. By judging whether the displacement characteristic parameters are greater than the second preset parameter, it is determined whether surge protection is required. The judgment method is simple and sensitive, and can trigger surge protection in a timely manner.

[0057] Furthermore, as an optional embodiment, a preset displacement range can be predetermined based on the type of compressor. If the displacement characteristic parameter is within the preset displacement range, the triggering condition is determined to be met; if the displacement characteristic parameter is not within the preset displacement range, the triggering condition is determined not to be met. By setting a preset displacement range, a certain margin is provided, reducing the risk of falsely triggering surge protection.

[0058] This application also provides shutdown protection for the refrigeration unit by actively opening the LBV valve, avoiding risks such as liquid slugging caused by starting the compressor with liquid. The shutdown protection process is described in detail below.

[0059] As an optional embodiment, the method further includes: Upon receiving a shutdown signal, the opening of the LBV valve is adjusted to the second preset valve opening. Obtain the condenser and evaporator pressures of the refrigeration unit; The LBV valve will be closed when the pressure difference between the condenser pressure and the evaporator pressure is less than the pressure balance value, or when the pressure balance time is greater than the preset time. The pressure balance time is the duration of the LBV valve opening being the second preset valve opening. Control the shutdown of the refrigeration unit.

[0060] In existing technology, refrigeration units typically shut down directly upon receiving a shutdown signal. However, after shutdown, a pressure difference exists between the condenser and evaporator sides. Liquid refrigerant on the high-pressure side migrates to the low-pressure side and slowly accumulates in the compressor. When the refrigeration unit restarts, the compressor starts with liquid, which may cause liquid slugging and damage the compressor.

[0061] Please refer to Figure 2 and Figure 3 , Figure 2 This is a schematic diagram illustrating the principle of a control method for an LBV valve provided in this application. Figure 3 This is a second flowchart illustrating a control method for an LBV valve provided in this application. In this embodiment, upon receiving a shutdown signal, the refrigeration unit is not directly shut down. Instead, the LBV valve is first opened, and its opening degree is adjusted to a second preset valve opening degree to balance the condenser pressure and evaporator pressure. The value of the second preset valve opening degree can be set according to actual needs, and this embodiment does not impose any particular limitation on it. For example, the second preset valve opening degree can be set to 100%, that is, the LBV valve is fully opened to quickly balance the condenser pressure and evaporator pressure.

[0062] After opening the LBV valve, the condenser pressure and evaporator pressure of the refrigeration unit are obtained. If the pressure difference between the condenser pressure and evaporator pressure is less than the pressure balance value, the pressures are considered balanced, and the refrigerant will not migrate to the compressor due to the pressure difference. Therefore, the LBV valve is closed, and the refrigeration unit is shut down. If the condenser and evaporator pressures balance slowly, and the pressure balancing time exceeds a preset time, the pressure difference is considered relatively small. Therefore, the LBV valve is closed in response to a shutdown signal to control the refrigeration unit to stop. This embodiment does not impose any particular limitation on the value of the pressure balance value.

[0063] In summary, this embodiment achieves compressor safety by actively opening the LBV valve to balance the condenser and evaporator pressures, preventing refrigerant migration to the compressor, avoiding the risk of liquid slugging in the compressor.

[0064] This application also reduces the difficulty of starting the refrigeration unit by actively opening the LBV valve, and the implementation process is described in detail below.

[0065] As an optional embodiment, the method further includes: Upon receiving the start signal, the evaporator inlet water temperature and condenser inlet water temperature of the refrigeration unit are acquired; Determine the absolute value of the temperature difference between the evaporator inlet water temperature and the condenser inlet water temperature; If the absolute value is greater than the temperature difference threshold, the opening of the LBV valve will be adjusted to the third preset valve opening, and the refrigeration unit will be started. If the absolute value is not greater than the temperature difference threshold, close the LBV valve and start the refrigeration unit.

[0066] Considering that the refrigeration unit is relatively difficult to start when there is a large temperature difference between the evaporator inlet water temperature and the condenser inlet water temperature, in this embodiment, the LBV valve is actively opened to provide a bypass path, thereby balancing the evaporator inlet water temperature and the condenser inlet water temperature, thus reducing the difficulty of starting the refrigeration unit and enabling the refrigeration unit to start smoothly.

[0067] Please refer to Figure 4 , Figure 4 This is a third flowchart illustrating a control method for an LBV valve provided in this application. Specifically, upon receiving a start signal, the evaporator inlet water temperature and condenser inlet water temperature of the refrigeration unit are acquired, and the absolute value of the temperature difference between them is determined. It is then determined whether the absolute value is greater than a temperature difference threshold. If the absolute value is greater than the temperature difference threshold, it is considered that starting the refrigeration unit is relatively difficult, therefore the opening degree of the LBV valve is adjusted to a third preset valve opening degree. If the absolute value is not greater than the temperature difference threshold, it is considered that the refrigeration unit can start smoothly, therefore the LBV valve is closed, and the refrigeration unit is started.

[0068] Furthermore, this embodiment does not impose a specific limitation on the cycle for obtaining the evaporator inlet water temperature and the condenser inlet water temperature; the inlet water temperature can be obtained according to a pre-set cycle. The value of the aforementioned third preset valve opening is also not specifically limited and can be set according to actual needs. For example, the third preset valve opening can be set to 50%.

[0069] As an optional embodiment, after determining the target valve opening based on the target bypass flow rate and flow characteristic curve, the method further includes: Obtain the preset opening limit value and the previous valve opening value; The sum of the opening limit value and the previous valve opening value is used as the upper boundary value of the target opening range, and the difference between the previous valve opening value and the opening limit value is used as the lower boundary value of the target opening range. If the target valve opening is greater than the upper boundary value, then the upper boundary value will be used as the final valve opening. If the target valve opening is less than or equal to the upper boundary value and greater than or equal to the lower boundary value, then the target valve opening is taken as the final valve opening. If the target valve opening is less than the lower boundary value, then the lower boundary value will be used as the final valve opening. Correspondingly, adjusting the LBV valve opening to the target valve opening includes: Adjust the LBV valve opening to the final valve opening.

[0070] In this embodiment, considering that a large change in the opening degree of the LBV valve can affect the operational stability of the compressor, after determining the target valve opening degree, based on the obtained opening degree limit value and the previous valve opening degree, it is determined whether the change in the target valve opening degree compared to the previous valve opening degree meets the requirements. Here, the previous valve opening degree is the target valve opening degree corresponding to the LBV valve when the LBV valve control method was executed last time; the opening degree limit value can be set according to actual needs, and this embodiment does not impose any special limitations on it, for example, setting the opening degree limit value to 5%.

[0071] Specifically, the sum of the opening limit value and the previous valve opening is used as the upper boundary value of the target opening range, and the difference between the previous valve opening and the opening limit value is used as the lower boundary value of the target opening range. By determining whether the target valve opening is within the target opening range, it is determined whether the change in the target valve opening compared to the previous valve opening meets the requirements.

[0072] If the target valve opening is less than or equal to the above upper boundary value and greater than or equal to the above lower boundary value, then the valve opening change is determined to meet the requirements. The target valve opening can be directly used as the final valve opening, and the opening of the LBV valve can be adjusted to the final valve opening.

[0073] If the target valve opening is greater than the upper boundary value or less than the lower boundary value, the valve opening change is determined to be unacceptable, and the valve opening change needs to be restricted to ensure the compressor's operational stability. Therefore, in this embodiment, for the case where the target valve opening is greater than the upper boundary value, the upper boundary value is used as the final valve opening; similarly, for the case where the target valve opening is less than the lower boundary value, the lower boundary value is used as the final valve opening, and the LBV valve opening is adjusted to the final valve opening.

[0074] In summary, this embodiment uses the opening limit value and the previous valve opening to determine whether the valve opening change of the LBV valve meets the requirements, and determines the final valve opening based on the judgment result, so as to avoid the negative impact of the LBV valve opening fluctuation on the compressor operation and ensure the stability of the compressor operation.

[0075] Please refer to Figure 5 , Figure 5 This application provides a schematic diagram of the structure of a refrigeration unit, which includes: Memory 501 is used to store computer programs; Processor 502 is used to implement the steps of any of the above-described LBV valve control methods when executing a computer program.

[0076] For a detailed description of the refrigeration unit provided in this application, please refer to the embodiments of the control method of the LBV valve described above; this application will not repeat the details here.

[0077] This application also provides a storage medium storing a computer program, which, when executed by a processor, implements the steps of any of the above-described LBV valve control methods.

[0078] The aforementioned storage media include all forms of non-volatile memory, media, and memory devices, such as semiconductor memory devices (e.g., EPROM, EEPROM, and flash memory devices), magnetic disks (e.g., internal hard disks or removable disks), magneto-optical disks, and CD-ROMs and DVD-ROMs. Processors and memory may be supplemented by or integrated into dedicated logic circuitry.

[0079] For a detailed description of the storage medium provided in this application, please refer to the embodiments of the control method for the LBV valve described above; this application will not repeat the details here.

[0080] While this specification contains numerous specific implementation details, these should not be construed as limiting the scope of any invention or the scope of the claims, but rather are primarily intended to describe features of specific embodiments of a particular invention. Certain features described in the various embodiments herein may also be implemented in combination in a single embodiment. Conversely, various features described in a single embodiment may also be implemented separately in various embodiments or in any suitable sub-combination. Furthermore, while features may function in certain combinations as described above and even initially claimed in this way, one or more features from a claimed combination may be removed from that combination in some cases, and a claimed combination may refer to a sub-combination or a variation thereof.

[0081] Similarly, although the operations are depicted in a specific order in the accompanying drawings, this should not be construed as requiring these operations to be performed in the specific order shown or sequentially, or requiring all illustrated operations to be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system modules and components in the above embodiments should not be construed as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

Claims

1. A control method for an LBV valve, characterized in that, The method includes: Obtain the actual load and demand load of the compressor in the refrigeration unit; the demand load is the load determined based on the refrigeration demand of the refrigeration unit. When the actual load is greater than the required load, the flow characteristic curve of the LBV valve, the actual mass flow rate of the compressor, and the required mass flow rate are obtained; the flow characteristic curve is used to characterize the correspondence between flow rate and valve opening. The target bypass flow rate of the LBV valve is determined based on the flow rate difference between the required mass flow rate and the actual mass flow rate. Based on the target bypass flow rate and the flow characteristic curve, the target valve opening is determined, and the opening of the LBV valve is adjusted to the target valve opening.

2. The control method for the LBV valve as described in claim 1, characterized in that, Determining the target valve opening based on the target bypass flow rate and the flow characteristic curve includes: The flow rate that is equal to the target bypass flow rate in the flow characteristic curve is taken as the target flow rate, and the valve opening corresponding to the target flow rate is taken as the initial valve opening. Determine whether the demand load is less than the minimum load of the compressor; the minimum load is the minimum load required for the compressor to maintain its operating state; If so, then obtain the previous opening increment of the LBV valve, and use the sum of the previous opening increment and the first preset opening increment as the current opening increment; use the sum of the current opening increment and the initial valve opening as the target valve opening. If not, then the initial valve opening is taken as the target valve opening.

3. The control method for the LBV valve as described in claim 1, characterized in that, After adjusting the opening degree of the LBV valve to the target valve opening degree, the method further includes: Obtain surge warning indicators; the surge warning indicators include at least one of the unit pressure ratio and the bearing displacement of the magnetic levitation bearing in the compressor; the unit pressure ratio is the ratio of the condenser pressure to the evaporator pressure of the refrigeration unit; Determine whether the surge warning index meets the triggering conditions for surge protection; If so, the first preset valve opening will be used as the surge protection valve opening. If not, then at each preset interval, the previous surge protection valve opening is obtained, and the difference between the previous surge protection valve opening and the second preset opening increment is used as the surge protection valve opening, until the surge protection valve opening reaches the minimum threshold. After determining the surge protection valve opening, the LBV valve opening is adjusted to the maximum of the surge protection valve opening and the target valve opening.

4. The control method for the LBV valve as described in claim 3, characterized in that, The surge warning index includes the unit pressure ratio, and determining whether the surge warning index meets the triggering conditions for surge protection includes: The pressure ratio variation characteristic parameter is determined based on the unit pressure ratio; the pressure ratio variation characteristic parameter is used to characterize the degree of change in the ratio of the condenser pressure to the evaporator pressure of the refrigeration unit; the pressure ratio variation characteristic parameter is positively correlated with the degree of change; If the pressure ratio change characteristic parameter is greater than the first preset parameter, then the triggering condition is determined to be met; If the pressure ratio change characteristic parameter is not greater than the first preset parameter, then the triggering condition is determined not to be met.

5. The control method for the LBV valve as described in claim 3, characterized in that, The surge warning index includes the bearing displacement, and determining whether the surge warning index meets the triggering conditions for surge protection includes: Displacement characteristic parameters are determined based on the bearing displacement; the displacement characteristic parameters are positively correlated with the bearing displacement. If the displacement characteristic parameter is greater than the second preset parameter, then the triggering condition is determined to be met; If the displacement characteristic parameter is not greater than the second preset parameter, then the triggering condition is determined not to be met.

6. The control method for the LBV valve as described in claim 1, characterized in that, The method further includes: Upon receiving a shutdown signal, the opening degree of the LBV valve is adjusted to the second preset valve opening degree; Obtain the condenser pressure and evaporator pressure of the refrigeration unit; When the pressure difference between the condenser pressure and the evaporator pressure is less than the pressure balance value, or when the pressure balance time is greater than a preset time, the LBV valve is closed; the pressure balance time is the duration for which the LBV valve is opened to the second preset valve opening. Control the refrigeration unit to stop.

7. The control method for the LBV valve as described in claim 1, characterized in that, The method further includes: Upon receiving a start signal, the evaporator inlet water temperature and the condenser inlet water temperature of the refrigeration unit are acquired. Determine the absolute value of the temperature difference between the evaporator inlet water temperature and the condenser inlet water temperature; If the absolute value is greater than the temperature difference threshold, the opening of the LBV valve is adjusted to the third preset valve opening, and the refrigeration unit is started. If the absolute value is not greater than the temperature difference threshold, then the LBV valve is closed and the refrigeration unit is started.

8. The control method for the LBV valve as described in claim 1, characterized in that, After determining the target valve opening based on the target bypass flow rate and the flow characteristic curve, the method further includes: Obtain the preset opening limit value and the previous valve opening value; The sum of the opening limit value and the previous valve opening is used as the upper boundary value of the target opening range, and the difference between the previous valve opening and the opening limit value is used as the lower boundary value of the target opening range. If the target valve opening is greater than the upper boundary value, then the upper boundary value is taken as the final valve opening. If the target valve opening is less than or equal to the upper boundary value and greater than or equal to the lower boundary value, then the target valve opening is taken as the final valve opening. If the target valve opening is less than the lower boundary value, then the lower boundary value is taken as the final valve opening. Correspondingly, adjusting the opening degree of the LBV valve to the target valve opening degree includes: Adjust the opening degree of the LBV valve to the final valve opening degree.

9. A refrigeration unit, characterized in that, The unit includes: Memory, used to store computer programs; A processor for executing the computer program to implement the steps of the control method for the LBV valve as described in any one of claims 1 to 8.

10. A storage medium, characterized in that, The storage medium stores a computer program, which, when executed by a processor, implements the steps of the LBV valve control method as described in any one of claims 1 to 8.

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