A progressive control method for helium screw compressor units

Abstract

The present invention relates to the field of refrigeration technology, and more particularly to a progressive control method for a helium screw compressor unit, comprising the following steps: S1: presetting a pressure target value and a pressure adjustment interval for the helium screw compressor unit, and calculating a regulation ratio zone based on the pressure adjustment interval, wherein the pressure adjustment interval is (K2, K1); K1 is an upper pressure limit, and K2 is a lower pressure limit; S2: obtaining a control variable for the pressure of the helium screw compressor unit; S3: determining whether the control variable is within the pressure adjustment interval, and confirming the solenoid valve conduction duration and the solenoid valve power-on time based on the determination result. The present invention can ensure that the system operates in an optimal state, can prevent positive and negative deviation problems, and thus achieve the purpose of precise control.

Description

Technical Field

[0001] The present invention relates to the field of refrigeration technology, and in particular to a progressive control method for a helium screw compressor unit. Background Art

[0002] As the largest energy-consuming component in the compression refrigeration system, the helium screw compressor directly affects the accuracy and stability of the system in high-precision applications. The load position or internal volume ratio VI of the helium screw compressor is adjusted by controlling the oil circuit through the solenoid valve, such as Figure 1 As shown, when the first and second solenoid valves 1 and 2 are energized, the loading oil port 3 is opened, and oil pressure pushes the compressor energy slide valve or the internal volume ratio slide valve to load. When the third and fourth solenoid valves 4 and 5 are energized, the unloading oil port 6 is opened, and oil pressure pushes the compressor energy slide valve or the internal volume ratio slide valve in the opposite direction to unload. Conventional helium screw compressor capacity control and internal volume ratio (VI) control employs interval control. When the controlled variable exceeds the "set upper limit," the load is reduced intermittently; when the controlled variable falls below the "set lower limit," the load is increased intermittently. For example, in helium unit exhaust pressure control, when the exhaust pressure exceeds the "upper pressure limit" of 21 bar, the compressor is unloaded intermittently. When the exhaust pressure falls below the "lower pressure limit" of 19 bar, the compressor is unloaded intermittently. The goal is to maintain the exhaust pressure around 20 bar. The energization time and intervals for compressor load increase and decrease are fixed unless manually modified.

[0003] However, the main problems with the traditional interval control method are as follows: 1. The optimal state of a helium screw compressor unit is to always stabilize the exhaust pressure at a set point. For example, if the exhaust pressure is 20 bar, the interval control mode cannot accurately control the exhaust pressure of the helium unit at a certain set point, but can only be within a range. If the interval is set too small, frequent adjustments are required, resulting in system instability. If the interval is set too large, it cannot meet the requirements of the helium screw compressor unit to operate accurately at the design pressure. 2. The power-on time and interval time set in the interval control mode are fixed. When the interval is set too small, it takes a long time to adjust to the specified state, which cannot meet the initial rapid adjustment requirements. When the interval is set too large, overshoot is prone to occur, and frequent adjustments lead to large fluctuations and instability in the system. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a progressive control method for a helium screw compressor unit, which can ensure accurate control of the actual pressure or internal volume ratio of the solenoid valve.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A progressive control method for a helium screw compressor unit comprises the following steps:

[0007] S1: Preset the target pressure value and pressure adjustment range of the helium screw compressor unit, and calculate the adjustment ratio range based on the pressure adjustment range, where:

[0008] The pressure adjustment range is (K2, K1); K1 is the upper limit of pressure, and K2 is the lower limit of pressure;

[0009] S2: Get the control variable of the helium screw compressor unit pressure;

[0010] S3: Determine whether the control variable is within the pressure adjustment range, and confirm the solenoid valve conduction duration and solenoid valve power-on time based on the judgment result, as follows:

[0011] If the controlled variable is not within the pressure regulation range, the solenoid valve conduction duration is set to the preset maximum power-on time, and the solenoid valve conduction interval is set to the preset minimum interval time;

[0012] If the controlled variable is not within the pressure adjustment range, calculate the absolute value Q of the difference between the controlled variable and the pressure target value, set the solenoid valve conduction duration to decrease as the Q value decreases, and set the solenoid valve conduction interval time to increase as the Q value decreases.

[0013] The beneficial effects of the present invention are as follows: the present invention provides a progressive control method for a helium screw compressor unit. When the Q value is within the pressure regulation range, the solenoid valve conduction duration is set to decrease as the Q value decreases, and the solenoid valve conduction interval is set to increase as the Q value decreases. As the controlled variable approaches the target value, the solenoid valve conduction duration becomes shorter and the solenoid valve conduction interval becomes longer, thereby reducing the regulation speed to ensure that the actual value accurately matches the target value, avoiding overshoot and ensuring response speed and stability. In addition, by changing the target value from the traditional upper and lower limit range to a set point, the present invention can ensure that the system operates in an optimal state when the control target is achieved, preventing positive and negative deviation problems, and thus achieving the purpose of precise control. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of the oil circuit structure of the solenoid valve recorded in the prior art;

[0015] Figure 2 It is a structural diagram of a solenoid valve recorded in the prior art;

[0016] Figure 3 This is a flowchart of the steps of a progressive control method for a helium screw compressor unit according to the present invention;

[0017] Figure 4Schematic diagram of a progressive control method for a helium screw compressor unit according to the present invention;

[0018] Description of labels:

[0019] 1. First solenoid valve; 2. Second solenoid valve; 3. Loading oil port; 4. Third solenoid valve; 5. Fourth solenoid valve; 6. Unloading oil port; 7. Intake pipe; 8. Oil inlet channel; 9. Oil return channel; 10. Energy slide valve; 11. Internal volume ratio slide valve. DETAILED DESCRIPTION

[0020] To illustrate the technical content, achieved objectives and effects of the present invention in detail, the following description is given in conjunction with the embodiments and accompanying drawings.

[0021] Please refer to Figures 3 and 4 , provides a progressive control method for a helium screw compressor unit, comprising the following steps:

[0022] S1: Preset the target pressure value and pressure adjustment range of the helium screw compressor unit, and calculate the adjustment ratio range based on the pressure adjustment range, where:

[0023] The pressure adjustment range is (K2, K1);

[0024] K1 is the upper limit of pressure, K2 is the lower limit of pressure;

[0025] S2: Get the control variable of the helium screw compressor unit pressure;

[0026] S3: Determine whether the control variable is within the pressure adjustment range, and confirm the solenoid valve conduction duration and solenoid valve power-on time based on the judgment result, as follows:

[0027] If the controlled variable is not within the pressure regulation range, the solenoid valve conduction duration is set to the preset maximum power-on time, and the solenoid valve conduction interval is set to the preset minimum interval time;

[0028] If the controlled variable is not within the pressure adjustment range, calculate the absolute value Q of the difference between the controlled variable and the pressure target value, set the solenoid valve conduction duration to decrease as the Q value decreases, and set the solenoid valve conduction interval time to increase as the Q value decreases.

[0029] As can be seen from the above description, the beneficial effects of the present invention are: providing a progressive control method for a helium screw compressor unit, when the Q value is ≤ K, the control variable is within the pressure regulation range, the solenoid valve conduction duration is set to decrease as the Q value decreases, and the solenoid valve conduction interval is set to increase as the Q value decreases. The closer the control variable is to the target value, the shorter the solenoid valve conduction duration and the longer the solenoid valve conduction interval, thereby reducing the regulation speed to ensure that the actual value accurately matches the target value, avoid overshoot, and ensure response speed and stability; in addition, by changing the target value from the traditional upper and lower limit interval to the set point, the present invention can ensure that the system operates in the optimal state when the control target is achieved, and can prevent the occurrence of positive and negative deviation problems, thereby achieving the purpose of precise control.

[0030] Furthermore, step S1 specifically includes:

[0031] The interval setting value is preset as K, and the pressure adjustment interval is calculated based on the interval setting value and the pressure target value, where:

[0032] K1=SK, K2=S+K, S is the target pressure value.

[0033] From the above description, it can be seen that by pre-setting the interval setting value and the pressure target value, the pressure adjustment interval can be quickly calculated according to the formula, and then the adjustment proportional area can be further obtained. The obtained adjustment proportional area is compared with the absolute value Q to obtain the interval time and duration of the solenoid valve conduction, thereby achieving precise control.

[0034] Furthermore, step S1 specifically includes:

[0035] The pressure adjustment range includes a dead zone adjustment range, and the pressure target value is within the dead zone adjustment range;

[0036] The dead zone adjustment range is (K2', K1'), as follows:

[0037] K2'=S-K', K1'=S+K'.

[0038] Dead zone corresponding to the adjustment ratio area

[0039] When the controlled variable is within the deadband adjustment interval, the solenoid valve conduction duration is set to a preset minimum power-on time.

[0040] From the above description, it can be seen that by adding a dead band control function in the pressure regulation range, when the difference between the control variable and the target is within the dead band, the solenoid valve conduction duration is 0, and the system does not make any adjustments, achieving the best stability effect, thereby ensuring that the exhaust pressure of the helium screw compressor unit remains stable for a long time.

[0041] Furthermore, step S1 specifically includes:

[0042] The calculated regulation proportion area is divided into a plurality of proportion regulation intervals, and a corresponding solenoid valve conduction duration and solenoid valve conduction interval are set for each proportion regulation interval.

[0043] Furthermore, step S1 specifically includes:

[0044] The calculated adjustment ratio area is divided into three ratio adjustment intervals, and the ranges of the three ratio adjustment intervals are:

[0045] The first proportional adjustment range is or The second proportional adjustment range is or The third proportional adjustment range is or

[0046] When the Q value is within the first proportional adjustment range,

[0047] When the Q value is within the second proportional adjustment range,

[0048] When the Q value is within the third proportional adjustment range,

[0049] Wherein, T1 is the duration of the solenoid valve conduction, T2 is the interval time of the solenoid valve conduction, t1 is the preset maximum power-on time, and t2 is the preset maximum interval time.

[0050] From the above description, it can be seen that by dividing the pressure adjustment interval into multiple adjustment intervals, segmented adjustment can be achieved, avoiding the problem of too large an adjustment interval. This allows for rapid adjustment when the control variable is far away from the target value, and fine-tuning when the control variable is close to the target value, thereby achieving progressive regulation and ensuring the response speed and stability of the system.

[0051] Furthermore, the preset maximum power-on time is 1 s, and the preset maximum interval time is 10 s.

[0052] Furthermore, the control variable of the helium screw compressor unit pressure is obtained every other cycle, and the cycle period is set to 3 seconds.

[0053] From the above description, it can be seen that the control variable of the helium screw compressor unit pressure is obtained every 3 seconds. When the calculated Q value exceeds the dead zone range, cyclic adjustment can be performed according to the adjustment range of the Q value to make the system return to the target value and continue to operate stably.

[0054] Please refer to Figures 3 and 4, embodiment 1 of the present invention is:

[0055] A progressive control method for a helium screw compressor unit is provided. The method is applied to the solenoid valves of the helium screw compressor unit. The solenoid valves include a first solenoid valve 1, a second solenoid valve 2, a loading oil port 3, a third solenoid valve 4, a fourth solenoid valve 5, a deloading oil port 6, an intake pipe 7, an oil inlet channel 8, and an oil return channel 9. Specifically, the first solenoid valve connects the oil inlet channel to the loading oil port, the third solenoid valve connects the loading oil port to one end of the oil return channel, the fourth solenoid valve connects the oil inlet channel to the deloading oil port, and the second solenoid valve connects the deloading oil port to one end of the oil return channel. The other end of the oil return channel connects to the intake pipe. When the first and second solenoid valves are energized, the loading oil port is opened, and oil pressure pushes the compressor's energy slide valve 10 or internal volume ratio slide valve 11 to load. When the third and fourth solenoid valves are energized, the deloading oil port is opened, and oil pressure reversely pushes the compressor's energy slide valve or internal volume ratio slide valve to deload. A progressive control method for a helium screw compressor unit of the present application realizes progressive control by controlling the on-time interval and on-duration of the third solenoid valve, the first solenoid valve, the fourth solenoid valve, and the second solenoid valve.

[0056] A progressive control method for a helium screw compressor unit comprises the following steps:

[0057] S1: Preset the target pressure value and pressure adjustment range of the helium screw compressor unit, and calculate the adjustment ratio range based on the pressure adjustment range, where:

[0058] The pressure adjustment range is (K2, K1);

[0059] K1 is the upper limit of pressure, K2 is the lower limit of pressure;

[0060] S2: Get the control variable of the helium screw compressor unit pressure;

[0061] S3: Determine whether the control variable is within the pressure adjustment range, and confirm the solenoid valve conduction duration and solenoid valve power-on time based on the judgment result, as follows:

[0062] If the controlled variable is not within the pressure regulation range, the solenoid valve conduction duration is set to the preset maximum power-on time, and the solenoid valve conduction interval is set to the preset minimum interval time;

[0063] If the controlled variable is not within the pressure adjustment range, calculate the absolute value Q of the difference between the controlled variable and the pressure target value, set the solenoid valve conduction duration to decrease as the Q value decreases, and set the solenoid valve conduction interval time to increase as the Q value decreases.

[0064] Step S1 specifically also includes:

[0065] The interval setting value is preset as K, and the pressure adjustment interval is calculated based on the interval setting value and the pressure target value, where:

[0066] K1=SK, K2=S+K, S is the target pressure value.

[0067] Specifically, the object of the progressive control method is the actual pressure or volume ratio of the helium screw compressor unit. Taking the actual pressure as an example, in step S1, the pressure target value of the helium screw compressor unit is pre-set within the pressure regulation range and the middle value of the pressure regulation range is taken as the target value. The control system of the helium screw compressor unit needs to enter the control program to set the operating parameters before operation. The preset operating parameters include the pressure target value, the preset maximum power-on time of the solenoid valve, the preset minimum power-on time of the solenoid valve, the preset maximum interval time of the solenoid valve, the preset minimum interval time of the solenoid valve, and the corresponding upper and lower pressure limits of the pressure regulation range. Preferably, the pressure target value S is 20 bar, the interval setting value K is 1 bar, the upper pressure limit K1 is 21 bar, the lower pressure limit K2 is 19 bar, the preset maximum power-on time is 1 second, and the preset maximum interval time is 10 seconds. The above operating parameters can be flexibly set according to the system model and oil pressure of the helium screw compressor unit to match different system requirements.

[0068] In this embodiment, step S1 specifically further includes:

[0069] The pressure adjustment range includes the dead zone adjustment range. The pressure target value is within the dead zone adjustment range. The dead zone corresponds to the adjustment ratio range.

[0070] Specifically, the dead zone adjustment interval is (K2', K1'), wherein K2'=S-K', K1'=S+K'.

[0071] When the control variable is within the deadband adjustment range, the solenoid valve conduction duration is set to a preset minimum power-on time.

[0072] Preferably, when K' is 0.1 bar, the dead zone adjustment interval is (19.9 bar, 20.1 bar). When the control variable is within the dead zone adjustment interval, such as when the control variable is 19.99 or 20.05, and the control variable is also within the dead zone adjustment interval, the solenoid valve conduction duration is 0s, that is, the solenoid valve is no longer conductive. Because as long as the solenoid valve is conductive, regardless of the amplitude and interval time, the pressure state of the system will fluctuate, so when the control variable enters the dead zone, the solenoid valve will not be adjusted, ensuring that the exhaust pressure of the helium screw compressor unit remains stable for a long time, achieving the best stabilization effect, and thus ensuring that the system can continue to operate stably in the current state.

[0073] In this embodiment, step S1 specifically further includes:

[0074] The calculated adjustment ratio area is divided into three ratio adjustment intervals, and the ranges of the three ratio adjustment intervals are:

[0075] The first proportional adjustment range is or The second proportional adjustment range is or The third proportional adjustment range is or

[0076] When the Q value is within the first proportional adjustment range,

[0077] When the Q value is within the second proportional adjustment range,

[0078] When the Q value is within the third proportional adjustment range,

[0079] Wherein, T1 is the duration of the solenoid valve conduction, T2 is the interval time of the solenoid valve conduction, t1 is the preset maximum power-on time, and t2 is the preset maximum interval time.

[0080] Refer to Table 1 below:

[0081]

[0082] Table 1

[0083] Working principle:

[0084] When the controlled variable is not within the pressure regulation range, the controlled variable is outside the pressure regulation range, the solenoid valve conduction duration is set to the preset maximum power-on time, and the solenoid valve conduction interval is set to the preset minimum interval time. The solenoid valve has the fastest response speed and the fastest regulation speed;

[0085] When the controlled variable is within the pressure regulation range, because the proportional regulation range is divided into three proportional regulation ranges and a deadband regulation range, it is necessary to determine which proportional regulation range or deadband regulation range the controlled variable is within. When the controlled variable is within the first proportional regulation range, the difference between the controlled variable and the target pressure value is large. The solenoid valve's on-time duration is relatively long, reaching three-quarters of the maximum on-time, while the solenoid valve's on-time interval is short, only one-quarter of the maximum on-time. This enables rapid response and high-speed regulation of the solenoid valve. When the controlled variable is within the second proportional regulation range, the difference between the controlled variable and the target pressure value decreases. The solenoid valve's on-time duration is shortened to one-half of the maximum on-time, while the solenoid valve's on-time interval is only one-half of the maximum on-time. Compared to the first proportional regulation range, both the solenoid valve's response speed and regulation efficiency are further reduced. When the controlled variable is within the third proportional regulation range, the difference between the controlled variable and the target pressure value is further reduced. The solenoid valve's on-time duration is shortened to only one-quarter of the maximum on-time, and the solenoid valve's on-time interval is only three-quarters of the maximum on-time. Compared to the second proportional control range, the solenoid valve's response speed and regulation efficiency are further reduced. When the controlled variable is also within the dead zone, the solenoid valve's on-time duration is 0 seconds, meaning the solenoid valve is no longer conducting. Through this segmented regulation, as the controlled variable approaches the target value, the regulation speed and response speed gradually decrease. This allows the solenoid valve to quickly adjust in the early stages, fine-tune in the later stages, and finally not adjust within the dead zone. This ensures regulation efficiency while avoiding overshoot, guaranteeing both the solenoid valve's control accuracy and stability.

[0086] In this embodiment, step S2 specifically further includes:

[0087] The control variable of the helium screw compressor unit pressure is obtained every 3 seconds. When the calculated control variable exceeds the dead zone adjustment range, the control is re-adjusted according to the adjustment ratio range of the control variable until the system returns to the target value and continues to operate stably.

[0088] In this embodiment, the modes of the helium screw compressor unit include a manual control mode and a system automatic control mode.

[0089] In summary, the progressive control method for a helium screw compressor unit provided by the present invention has the following advantages: 1. By dividing the pressure regulation interval into multiple regulation intervals, segmented regulation can be achieved, avoiding the problem of an excessively large regulation interval, thereby enabling rapid regulation when the control variable is far from the target value, and fine-tuning when the control variable is close to the target value, thereby achieving progressive regulation, thereby ensuring the response speed and stability of the system; 2. By adding a dead zone control function to the pressure regulation interval, when the difference between the control variable and the target is within the dead zone range, the solenoid valve conduction duration is 0, and the system does not make any adjustments, achieving the best stability effect, thereby ensuring that the exhaust pressure of the helium screw compressor unit remains stable for a long time; 3. The target value is changed from the traditional upper and lower limit intervals to a set point. Once the control target is achieved, the system can be guaranteed to operate in the best state without positive and negative deviation problems; 4. The operating parameters can be modified according to the control system of the unit to match different system requirements.

[0090] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention's description and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A progressive control method for a helium screw compressor unit, characterized in that: The following steps are involved: S1: Preset the target pressure value and pressure adjustment range of the helium screw compressor unit, and calculate the adjustment ratio range based on the pressure adjustment range, where: The pressure adjustment range is (K2, K1); K1 is the upper limit of pressure, K2 is the lower limit of pressure; S2: Get the control variable of the helium screw compressor unit pressure; S3: Determine whether the control variable is within the pressure adjustment range, and confirm the solenoid valve conduction duration and solenoid valve power-on time based on the judgment result, as follows: If the controlled variable is not within the pressure regulation range, the solenoid valve conduction duration is set to the preset maximum power-on time, and the solenoid valve conduction interval is set to the preset minimum interval time; If the controlled variable is not within the pressure adjustment range, calculate the absolute value Q of the difference between the controlled variable and the pressure target value, set the solenoid valve conduction duration to decrease as the Q value decreases, and set the solenoid valve conduction interval time to increase as the Q value decreases.

2. A progressive control method for a helium screw compressor unit according to claim 1, characterized in that: Step S1 further includes: The interval setting value is preset as K, and the pressure adjustment interval is calculated based on the interval setting value and the pressure target value, where: K1=SK, K2=S+K, S is the target pressure value.

3. A progressive control method for a helium screw compressor unit according to claim 2, characterized in that: Step S1 further includes: The pressure adjustment range includes a dead zone adjustment range, and the pressure target value is within the dead zone adjustment range; The dead zone adjustment range is (K2', K1'), as follows: K2'=S-K', K1'=S+K'; Dead zone corresponding to the adjustment ratio area When the controlled variable is within the deadband adjustment interval, the solenoid valve conduction duration is set to a preset minimum power-on time.

4. A progressive control method for a helium screw compressor unit according to claim 3, characterized in that: Step S1 further includes: The calculated regulation proportion area is divided into a plurality of proportion regulation intervals, and a corresponding solenoid valve conduction duration and solenoid valve conduction interval are set for each proportion regulation interval.

5. A progressive control method for a helium screw compressor unit according to claim 4, characterized in that: Step S1 further includes: The calculated adjustment ratio area is divided into three ratio adjustment intervals, and the ranges of the three ratio adjustment intervals are: The first proportional adjustment range is or The second proportional adjustment range is or The third proportional adjustment range is or When the control variable is within the first proportional adjustment interval, When the control variable is within the second proportional adjustment range, When the control variable is within the third proportional adjustment range, Wherein, T1 is the duration of the solenoid valve conduction, T2 is the interval time of the solenoid valve conduction, t1 is the preset maximum power-on time, and t2 is the preset maximum interval time.

6. A progressive control method for a helium screw compressor unit according to claim 5, characterized in that: The preset maximum power-on time is 1s, and the preset maximum interval time is 10s.

7. The progressive control method for a helium screw compressor unit according to claim 1, characterized in that: Step S2 further includes: The control variable of the helium screw compressor unit pressure is obtained every other cycle, wherein the cycle period is set to 3s.

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