Water chiller and throttling control method thereof

Abstract

The application provides a throttling control method of a water chilling unit. The target flow capacity of an electronic expansion valve is calculated according to the real-time current of a compressor and the real-time pressure difference of the electronic expansion valve. The target opening degree corresponding to the target flow capacity of the electronic expansion valve is obtained by inquiring a preset flow capacity-opening degree table. The opening degree of the electronic expansion valve is adjusted by taking the obtained target opening degree as a control target, thereby improving the stability and reliability of the throttling control. Compared with the existing liquid level control mode and the exhaust gas superheat control mode, the liquid level sensor and the temperature sensor are not needed, thereby reducing the cost of the unit. Meanwhile, compared with the unit using only an orifice plate as a throttling element, the problem that the throttling capacity of the orifice plate is not matched with the load at partial load is solved.

Description

Technical Field

[0001] This invention belongs to the field of water chillers, and more specifically, relates to a water chiller and its throttling control method. Background Technology

[0002] Throttling mechanisms are a component of air conditioning systems. Orifice plates are commonly used throttling mechanisms in chiller units. When an orifice plate is used as a throttling element, the throttling characteristics of the system cannot always be maintained at their optimal state because the orifice size cannot be adjusted, especially under partial load, where the throttling capacity of the orifice plate does not match the load well. A liquid bypass circuit is often set between the condenser and evaporator, and an electronic expansion valve is installed on the liquid bypass circuit. Since the orifice diameter of the orifice plate is fixed, the control of the electronic expansion valve is crucial.

[0003] Currently used electronic expansion valve control methods mostly use liquid level or suction / discharge superheat as control targets, automatically adjusting the electronic expansion valve opening to the target value during unit operation. Liquid level control adjusts the electronic expansion valve opening by calculating the difference between the actual evaporator liquid level and the set evaporator liquid level. However, during actual unit operation, the evaporator shell and tubes are in a boiling state, and the liquid level sensor's judgment of the real-time liquid level has a large deviation, resulting in large fluctuations in the liquid level display value and extremely unstable unit operation. Suction / discharge superheat control adjusts the electronic expansion valve opening by calculating the difference between the actual suction / discharge superheat and the target superheat. Due to the system characteristics of centrifugal chillers, the suction superheat is much smaller than the discharge superheat, resulting in no significant change in suction temperature when the electronic expansion valve is adjusted over a large range, creating a serious control blind zone. Therefore, discharge superheat control is generally preferred. All of these control methods require the addition of additional liquid level or temperature sensors, increasing the unit's production cost. Summary of the Invention

[0004] The purpose of this invention is to provide a chiller unit and its throttling control method to solve the problem of high cost caused by the reliance on sensors in existing throttling control methods.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention first provides a throttling control method for a chiller unit, comprising:

[0007] Obtain the real-time current I of the compressor s Real-time differential pressure P of the electronic expansion valve s and the real-time opening degree E of the electronic expansion valve s ;

[0008] According to the real-time current I s The real-time pressure difference P sThe target flow capacity M of the electronic expansion valve is calculated using the preset flow capacity calculation rules. j And according to the target flow capacity M j The target opening E of the electronic expansion valve is obtained by comparing it with a preset flow capacity and opening degree table. j ;

[0009] According to the real-time opening E s and the target opening E j Adjust the opening degree of the electronic expansion valve.

[0010] Furthermore, in the case of the real-time current I s The real-time pressure difference P s The target flow capacity M of the electronic expansion valve is calculated using the preset flow capacity calculation rules. j Previously, it also included:

[0011] Whether to adjust the opening of the electronic expansion valve is determined based on either the first preset opening adjustment strategy or the second preset opening adjustment strategy.

[0012] Furthermore, determining whether to adjust the opening of the electronic expansion valve based on the first preset opening adjustment strategy includes:

[0013] According to the real-time current I s The real-time opening degree E s The target pressure difference P of the electronic expansion valve is obtained by comparing it with a preset table of current, opening degree, and pressure difference. j ;

[0014] Determine the target pressure difference P j With the real-time pressure difference P s Is the difference between them within the preset deviation range?

[0015] If so, maintain the opening of the electronic expansion valve;

[0016] If not, adjust the opening of the electronic expansion valve.

[0017] Furthermore, regarding the real-time opening E of the currently described electronic expansion valve... s Equal to the target opening E j At that time, the real-time opening E of the electronic expansion valve will be... s and the real-time pressure difference P s and the real-time current I of the compressor currently described. s Record the current, opening degree and differential pressure in the preset table.

[0018] Furthermore, the real-time opening E of the current electronic expansion valve is... s and the real-time pressure difference P sand the real-time current I of the compressor currently described. s The records in the preset current, opening degree, and differential pressure lookup table include:

[0019] Determine the real-time opening E of the electronic expansion valve. s Whether it has been recorded in the preset current, opening degree and differential pressure lookup table;

[0020] If so, then the current real-time opening degree E will be... s The preset real-time current and preset target pressure difference corresponding to the preset current, opening degree and pressure difference lookup table are replaced with the current real-time current I. s And the current real-time pressure difference P s ;

[0021] If not, then add the current real-time opening degree E to the preset current, opening degree, and differential pressure lookup table. s The current real-time current I s Compared with the current real-time pressure difference P s The correspondence between them.

[0022] Furthermore, determining whether to adjust the opening of the electronic expansion valve based on the second preset opening adjustment strategy includes:

[0023] According to the real-time pressure difference P s The suction superheat T of the compressor is obtained by comparing it with a preset pressure difference and suction superheat table. X ;

[0024] Determine the intake superheat T X Is it within the preset superheat range?

[0025] If so, maintain the opening of the electronic expansion valve;

[0026] If not, adjust the opening of the electronic expansion valve.

[0027] Furthermore, the step of basing the real-time current I s The real-time pressure difference P s The target flow capacity M of the electronic expansion valve is calculated using the preset flow capacity calculation rules. j include:

[0028] Calculate the real-time current I s The current ratio X2 between the current and the set standard current I0, and the real-time pressure difference P s The pressure difference ratio X1 between the set standard pressure difference P0 and the standard pressure difference;

[0029] According to the formula: Y = a0 + a 1* X1+a 2*X2+a 3* X1 2 +a 4* X 1* X2+a 5* X2 2 The flow capacity ratio Y of the electronic expansion valve is calculated, where a0, a1, a2, a3, a4, and a5 are set values.

[0030] The target circulation capacity M is obtained based on the circulation capacity ratio Y and the set standard circulation capacity M0. j .

[0031] Furthermore, it also includes:

[0032] When the chiller unit is started, the opening degree of the electronic expansion valve is controlled to reach the preset initial opening degree E. c ;

[0033] After the chiller unit is running normally, the process continues to acquire the real-time current I of the compressor. s The steps.

[0034] The present invention also provides a water chiller unit, the water chiller unit including a compressor, a condenser and an evaporator, a liquid bypass circuit is provided between the condenser and the evaporator, an electronic expansion valve is provided on the liquid bypass circuit, and the controller of the water chiller unit executes the throttling control method described above.

[0035] Furthermore, the chiller unit is a two-stage centrifugal chiller unit.

[0036] Compared with the prior art, the beneficial effects of the chiller unit and its throttling control method provided by the present invention are as follows: while ensuring the throttling capacity of part load and the matching of load, the structure does not require liquid level sensor and temperature sensor, which improves the stability and reliability of control and saves costs. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the structure of the chiller unit provided by the present invention;

[0039] Figure 2 A flowchart illustrating the throttling control method provided by the present invention;

[0040] Figure 3 Detailed flowchart of the throttling control method provided by the present invention Figure 1 ;

[0041] Figure 4 Detailed flowchart of the throttling control method provided by the present invention Figure 2 ;

[0042] The main markings in the attached figures are as follows:

[0043] 1. Frequency converter; 2. Compressor; 3. Evaporator; 4. Condenser; 5. Flash evaporator;

[0044] 21. Motor; 22. Impeller; 23. Guide vane actuator;

[0045] 61. Primary orifice plate; 62. Secondary orifice plate;

[0046] 70. Liquid bypass circuit; 71. Electronic expansion valve. Detailed Implementation

[0047] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0048] Throttling mechanisms are an integral part of air conditioning systems. Orifice plates are commonly used throttling mechanisms in chiller units. When used as throttling elements, the orifice size cannot be adjusted, so the system's throttling characteristics cannot always be maintained at their optimal state, especially under partial load, where the orifice plate's throttling capacity does not match the load well. A liquid bypass circuit is often set between the condenser and evaporator, and an electronic expansion valve is installed on this circuit. Since the orifice diameter is fixed, the control of the electronic expansion valve is crucial. Currently used electronic expansion valve control methods mostly use the liquid level or suction / discharge superheat as the control target, automatically adjusting the electronic expansion valve opening to the target value during unit operation. Liquid level control adjusts the electronic expansion valve opening by calculating the difference between the actual evaporator liquid level and the set evaporator liquid level. However, during actual unit operation, the evaporator shell and tubes are in a boiling state, and the liquid level sensor's judgment of the real-time liquid level has a large deviation, resulting in large fluctuations in the liquid level display value and extremely unstable unit operation. The intake and exhaust superheat control method adjusts the opening of the electronic expansion valve by calculating the difference between the actual intake and exhaust superheat and the target superheat. However, due to the system characteristics of centrifugal chillers, the intake superheat is much smaller than the exhaust superheat, resulting in no significant change in intake temperature when the electronic expansion valve is adjusted over a wide range, creating a serious control blind zone. Therefore, exhaust superheat control is generally preferred. All of the above control methods require the addition of level or temperature sensors, increasing the unit's production cost.

[0049] In response, this invention proposes a new throttling control method for chiller units, which improves the stability and reliability of control while also saving costs.

[0050] like Figure 1 As shown, the throttling control method proposed in this invention is applied to a chiller unit. The chiller unit includes a compressor 2, a condenser 4 and an evaporator 3. A liquid bypass circuit 70 is provided between the condenser 4 and the evaporator 3, and an electronic expansion valve 71 is provided on the liquid bypass circuit 70.

[0051] like Figure 2 As shown, the throttling control method proposed in this invention includes at least the following steps:

[0052] Obtain the real-time current I of the compressor s Real-time differential pressure P of the electronic expansion valve s and the real-time opening degree E of the electronic expansion valve s ;

[0053] Based on real-time current I s Real-time differential pressure P s The target flow capacity M of the electronic expansion valve is calculated using the preset flow capacity calculation rules. j And based on the target circulation capacity M j The target opening E of the electronic expansion valve is obtained by comparing it with the preset flow capacity and opening degree table. j ;

[0054] According to the real-time opening degree E s and target opening E j Adjust the opening degree of the electronic expansion valve.

[0055] The advantage of this design is that it calculates the target flow capacity of the electronic expansion valve based on the real-time current of the compressor and the real-time differential pressure of the electronic expansion valve. By consulting a preset flow capacity-opening table, it obtains the target opening corresponding to the target flow capacity of the electronic expansion valve. The obtained target opening is then used as the control target to adjust the opening of the electronic expansion valve, improving the stability and reliability of the throttling control. Compared to existing liquid level control and exhaust superheat control methods, it eliminates the need for liquid level and temperature sensors, reducing unit costs. Furthermore, compared to units that use only orifice plates as throttling elements, it also solves the problem of poor matching between the orifice plate's throttling capacity and the load under partial load.

[0056] It should be understood that the real-time pressure difference of the electronic expansion valve is equal to the difference between the condensing pressure and the evaporating pressure. A preset flow capacity and opening degree correspondence table records the one-to-one relationship between the flow capacity and opening degree of the electronic expansion valve.

[0057] In some alternative embodiments, based on the real-time current Is Real-time differential pressure P s The target flow capacity M of the electronic expansion valve is calculated using the preset flow capacity calculation rules. j Previously, it also included:

[0058] Whether to adjust the opening of the electronic expansion valve is determined based on either the first preset opening adjustment strategy or the second preset opening adjustment strategy.

[0059] The advantage of this design is that the invention can also determine in advance whether to adjust the opening of the electronic expansion valve, avoiding frequent over-adjustment of the electronic expansion valve and thus improving the accuracy and reliability of throttling control. Furthermore, multiple preset opening adjustment strategies are available, making it suitable for a wider range of applications.

[0060] In further alternative embodiments, such as Figure 3 As shown, determining whether to adjust the opening of the electronic expansion valve based on the first preset opening adjustment strategy includes:

[0061] Based on real-time current I s Real-time opening degree E s The target pressure difference P of the electronic expansion valve is obtained by comparing it with the preset current, opening degree and pressure difference table. j ;

[0062] Determine the target pressure difference P j With real-time pressure difference P s Is the difference between them within the preset deviation range?

[0063] If so, maintain the opening of the electronic expansion valve;

[0064] If not, adjust the opening of the electronic expansion valve.

[0065] The advantage of this design is that the present invention first deduces the target differential pressure of the electronic expansion valve based on the real-time current of the compressor and the real-time opening degree of the electronic expansion valve, and then determines whether to adjust the opening degree of the electronic expansion valve based on the target differential pressure and the real-time differential pressure. This opening degree adjustment strategy is simple and easy to implement, and is suitable for various operating conditions of the unit.

[0066] Specifically, the preset deviation range is [P] 0min ,P 0max 】

[0067] If P 0min ≤P j -P s ≤P 0max Then the opening of the electronic expansion valve will be maintained;

[0068] If P j -P s <P 0min If so, increase the opening of the electronic expansion valve;

[0069] If P j -P s >P 0min This reduces the opening of the electronic expansion valve.

[0070] The increase and decrease values ​​of the electronic expansion valve are based on the real-time opening degree E of the electronic expansion valve. s With target opening E j Calculated.

[0071] In a further alternative embodiment, the real-time opening E of the current electronic expansion valve s Equal to target opening E j At that time, the real-time opening degree E of the current electronic expansion valve will be... s and real-time pressure difference P s and the current real-time current I of the compressor. s Record it in the preset current, opening degree and differential pressure comparison table.

[0072] The advantage of this design is that it continuously records the correspondence between the compressor current, the opening degree of the electronic expansion valve, and the differential pressure of the electronic expansion valve when a high-efficiency throttling effect can be achieved. The controller then adjusts the opening degree of the electronic expansion valve in a timely manner, so that the unit always performs throttling control in the high-efficiency zone.

[0073] In a further optional embodiment, the real-time opening degree E of the current electronic expansion valve is... s and real-time pressure difference P s and the current real-time current I of the compressor. s The data recorded in the preset current, opening degree, and differential pressure lookup table includes:

[0074] Determine the real-time opening degree E of the current electronic expansion valve s Has it been recorded in the preset current, opening degree and differential pressure comparison table?

[0075] If so, then set the current real-time opening degree E. s Replace the preset real-time current and preset target pressure difference in the preset current, opening degree and pressure difference lookup table with the current real-time current I. s and the current real-time pressure difference P s ;

[0076] If not, add the current real-time opening degree E to the preset current, opening degree, and differential pressure lookup table. s Current real-time current I s With the current real-time pressure difference P s The correspondence between them.

[0077] The advantage of this design is that, in the process of recording the correspondence between compressor current, electronic expansion valve opening degree, and electronic expansion valve differential pressure, it also determines whether the newly added data conflicts with or duplicates the data already stored in the preset current, opening degree, and differential pressure comparison table, thereby improving the accuracy of control.

[0078] In further alternative embodiments, such as Figure 4 As shown, determining whether to adjust the opening of the electronic expansion valve based on the second preset opening adjustment strategy includes:

[0079] According to the real-time pressure difference P s The compressor's suction superheat T is obtained by comparing it with the preset pressure difference and suction superheat table. X ;

[0080] Determining the intake superheat T X Is it within the preset superheat range?

[0081] If so, maintain the opening of the electronic expansion valve;

[0082] If not, adjust the opening of the electronic expansion valve.

[0083] The advantage of this design is that the present invention obtains the compressor's suction superheat corresponding to the real-time pressure difference of the electronic expansion valve by querying a preset pressure difference and suction superheat comparison table, and determines whether to adjust the opening of the electronic expansion valve based on the compressor's suction superheat. This opening adjustment strategy is simple and easy to implement, and adaptable to specific operating conditions of the unit, such as when the compressor suction superheat is too low or the evaporation pressure is too low during unit operation. It achieves optimal adjustment of suction superheat and partial load performance, improving the reliability and energy efficiency of the unit.

[0084] Specifically, this invention pre-stores a pressure difference and suction superheat comparison table, eliminating the need to install a temperature sensor at the compressor suction port. The preset superheat range is [T]. 0min ,T 0max 】

[0085] If T 0min ≤T X ≤T 0max Then the opening of the electronic expansion valve will be maintained;

[0086] If T X <T 0min If so, increase the opening of the electronic expansion valve;

[0087] If T X >T 0max This reduces the opening of the electronic expansion valve.

[0088] The increase and decrease values ​​of the electronic expansion valve are based on the real-time opening degree E of the electronic expansion valve.s With target opening E j Calculated.

[0089] From the perspective of intake superheat regulation, when T X >T 0max If the superheat of the gaseous refrigerant at the evaporator outlet is too high, it indicates that the gaseous refrigerant is absorbing too much heat from the liquid line at the top of the evaporator, increasing the compressor's power consumption. In this case, it is necessary to reduce the opening of the electronic expansion valve to decrease the flow rate in the liquid line, thereby reducing T. X When T X <T 0min If, at this point, the gaseous refrigerant at the evaporator outlet shows no superheat, it indicates that the compressor is carrying liquid in the suction, which will severely affect the compressor's safe operation. In this situation, it is necessary to increase the opening of the electronic expansion valve to increase the liquid flow rate and thus improve T. X When T 0min ≤T X ≤T 0max When the temperature is within a suitable range, it indicates that the suction superheat is within the appropriate range and there is no need to adjust the liquid pipe flow rate; the electronic expansion valve will maintain its current opening.

[0090] From a load regulation perspective, when the chiller unit is running under unloaded conditions, the amount of refrigerant evaporating in the evaporator decreases, the amount of gaseous refrigerant decreases, and T X It will increase, when T X Increase to greater than T 0max When the controller is in operation, it will reduce the opening of the electronic expansion valve, thus reducing the liquid flow rate; conversely, when the chiller unit is running under load, the amount of refrigerant evaporating in the evaporator increases, the amount of gaseous refrigerant increases, and T... X It will decrease when T X Reduce to less than T 0min At this time, the controller will increase the opening of the electronic expansion valve, thereby increasing the flow rate in the liquid line.

[0091] In a further alternative embodiment, based on the real-time current I s Real-time differential pressure P s The target flow capacity M of the electronic expansion valve is calculated using the preset flow capacity calculation rules. j include:

[0092] Calculate the real-time current I s The current ratio X2 between the current and the set standard current I0, and the real-time voltage difference P s The pressure difference ratio X1 between the set standard pressure difference P0 and the standard pressure difference;

[0093] According to the formula: Y = a0 + a 1* X1+a 2* X2+a 3* X1 2 +a 4* X1* X2+a 5* X2 2 The flow capacity ratio Y of the electronic expansion valve is calculated, where a0, a1, a2, a3, a4, and a5 are set values.

[0094] The target circulation capacity M is obtained by comparing the circulation capacity ratio Y with the set standard circulation capacity M0. j .

[0095] The advantage of this design is that the present invention fits the formula for calculating the flow capacity ratio Y by pre-testing multiple sets of data, and it is closely related to the compressor current and the pressure difference of the electronic expansion valve, which makes it easy to calculate the target flow capacity of the electronic expansion valve and is simple and easy to implement.

[0096] Specifically, X1 = P s / P0;X2=I s / I0;

[0097] Y = a0 + a 1* X1+a 2* X2+a 3* X1 2 +a 4* X 1* X2+a 5* X2 2 , a0=3.0, a1=-4.25, a2=6.15, a3=7.05, a4=-11.50, a5=8.25.

[0098] In a further optional embodiment, the throttling control method further includes:

[0099] When the chiller unit is started, the opening degree of the electronic expansion valve reaches the preset initial opening degree E. c ;

[0100] After the chiller unit is running normally, it continues to obtain the real-time current I of the compressor. s The steps.

[0101] The advantage of this design is that after the unit receives the start-up command, the electronic expansion valve is directly adjusted to the initial opening degree E. c This ensures that the unit has a good throttling effect before entering normal operation.

[0102] In practical applications, the initial opening is usually set to 50% during factory testing. After all operating conditions are tested, the initial opening is set to the minimum opening of the electronic expansion valve that can meet the reliability requirements of the test. Subsequent models of the same type are set using the same set of parameters. The initial opening is an empirical parameter.

[0103] In addition, after the controller receives the command that the compressor has been shut down, it controls the opening of the electronic expansion valve to close to 0 within a preset time T2.

[0104] like Figure 1 As shown, the chiller unit proposed in this invention includes at least a compressor 2, a condenser 4, and an evaporator 3. A liquid bypass circuit 70 is provided between the condenser 4 and the evaporator 3, and an electronic expansion valve 71 is provided on the liquid bypass circuit 70. At the same time, the controller of the chiller unit executes the throttling control method described above.

[0105] The advantage of this design is that the chiller unit proposed in this invention does not require additional liquid level and temperature sensors for throttling control, thus reducing the unit cost.

[0106] In a further optional embodiment, the chiller unit is a two-stage centrifugal chiller unit, which has advantages such as good energy-saving effect and high reliability.

[0107] To better understand this invention, the design principles of this invention will be described in detail below:

[0108] like Figure 1 As shown, the chiller unit includes a frequency converter 1, a compressor 2, an evaporator 3, a condenser 4, and a flash evaporator 5. The compressor 2 includes a motor 21, an impeller 22, and a guide vane actuator 23, etc.

[0109] Evaporator 3, condenser 4, and flash evaporator 5 are connected to compressor 2 via piping. A primary orifice plate 61 is installed on the piping between condenser 4 and flash evaporator 5, and a secondary orifice plate 62 is installed on the piping between flash evaporator 5 and evaporator 3. The compressor 2, condenser 4, primary orifice plate 61, flash evaporator 5, secondary orifice plate 62, and evaporator 3 are sequentially connected via piping to form the main refrigerant circulation loop. Simultaneously, a liquid bypass loop 70 is provided between condenser 4 and evaporator 3, and two electronic expansion valves 71 are installed on the liquid bypass loop 70.

[0110] In practical applications, the high-temperature, high-pressure refrigerant is discharged into the condenser 4 by the compressor 2. After cooling and condensation, the refrigerant is divided into two paths: one path passes through the first-stage orifice plate 61, the flash evaporator 5, and the second-stage orifice plate 62 before entering the evaporator 3. At the same time, the gaseous refrigerant in the flash evaporator 5 is directly supplied to the compressor 2's gas supply port through the gas supply line, increasing the compressor 2's discharge volume; the other path enters the liquid bypass circuit 70, where it is throttled by the electronic expansion valve 71.

[0111] According to the orifice plate flow calculation formula Where q m ρ is the refrigerant flow rate, ε is the expansion coefficient, C is the discharge coefficient, ρ1 is the refrigerant density, β is the aperture ratio, Δp is the pressure difference before and after, and d is the aperture.

[0112] From the above formulas, we can see that the refrigerant flow rate is positively correlated with the orifice plate diameter and the pressure difference. The compressor current is positively correlated with the refrigerant flow rate; conversely, we can deduce that the orifice plate diameter is positively correlated with the compressor current and inversely correlated with the pressure difference. The electronic expansion valve can be considered as an orifice plate with a variable cross-sectional area, thus we can see that the electronic expansion valve opening is positively correlated with the compressor current and inversely correlated with the electronic expansion valve pressure difference.

[0113] Based on this, the throttling control method proposed in this invention calculates the opening value of the electronic expansion valve using real-time compressor current and electronic expansion valve differential pressure. The calculated target opening is then used as the control objective to adjust the electronic expansion valve, improving the stability and reliability of throttling control. Simultaneously, the electronic expansion valve opening, electronic expansion valve differential pressure, and compressor current under stable conditions are recorded in the mainboard. This data is continuously recorded during subsequent after-sales operation, and real-time corrections are made through the controller, ensuring the unit consistently performs high-efficiency throttling control. Compared to existing liquid level control and exhaust superheat control methods, this method eliminates the need for liquid level and temperature sensors, reducing unit costs. Furthermore, compared to units using only orifice plates as throttling elements, it also solves the problem of poor load matching between the orifice plate's throttling capacity and the load under partial load conditions.

[0114] In addition, the electronic expansion valve control has two modes: manual and automatic. In automatic mode, after each target cycle T1, the target opening degree of the electronic expansion valve is calculated based on the real-time compressor current value and the pressure difference of the electronic expansion valve. The calculated target opening degree is used as the control target to adjust the electronic expansion valve. T1 is the time obtained from the actual measured data of the chiller unit, and the controller can set T1. In manual mode, the target opening degree of the electronic expansion valve can be manually set.

[0115] In summary, the beneficial effects of the chiller unit and its throttling control method provided by this invention are as follows: while ensuring the throttling capacity of the partial load matches the load, the structure does not require a liquid level sensor and a temperature sensor, which improves the stability and reliability of the control and saves costs.

[0116] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A throttling control method for a chiller unit, characterized in that, include: Obtain the real-time current I of the compressor s Real-time differential pressure P of the electronic expansion valve s and the real-time opening degree E of the electronic expansion valve s ; According to the real-time current I s The real-time pressure difference P s The target flow capacity M of the electronic expansion valve is calculated using the preset flow capacity calculation rules. j And according to the target flow capacity M j The target opening E of the electronic expansion valve is obtained by comparing it with a preset flow capacity and opening degree table. j ; According to the real-time opening E s and the target opening E j Adjust the opening degree of the electronic expansion valve; The step of calculating the target flow capacity Mj of the electronic expansion valve based on the real-time current Is, the real-time pressure difference Ps, and the preset flow capacity calculation rules includes: Calculate the current ratio X2 between the real-time current Is and the set standard current I0, and the pressure ratio X1 between the real-time pressure difference Ps and the set standard pressure difference P0; The flow capacity ratio Y of the electronic expansion valve is calculated according to the formula: Y=a0+a1*X1+a2*X2+a3*X12+a4*X1*X2+a5*X22, where a0, a1, a2, a3, a4, and a5 are set values. The target circulation capacity Mj is obtained based on the circulation capacity ratio Y and the set standard circulation capacity M0.

2. The throttling control method for a chiller unit as described in claim 1, characterized in that, According to the real-time current I s The real-time pressure difference P s The target flow capacity M of the electronic expansion valve is calculated using the preset flow capacity calculation rules. j Previously, it also included: Whether to adjust the opening of the electronic expansion valve is determined based on either the first preset opening adjustment strategy or the second preset opening adjustment strategy.

3. The throttling control method for a chiller unit as described in claim 2, characterized in that, Determining whether to adjust the opening of the electronic expansion valve based on the first preset opening adjustment strategy includes: According to the real-time current I s The real-time opening degree E s The target pressure difference P of the electronic expansion valve is obtained by comparing it with a preset table of current, opening degree, and pressure difference. j ; Determine the target pressure difference P j With the real-time pressure difference P s Is the difference between them within the preset deviation range? If so, maintain the opening of the electronic expansion valve; If not, adjust the opening of the electronic expansion valve.

4. The throttling control method for a chiller unit as described in claim 3, characterized in that, The real-time opening E of the currently described electronic expansion valve s Equal to the target opening E j At that time, the real-time opening E of the electronic expansion valve will be... s and the real-time pressure difference P s and the real-time current I of the compressor currently described. s Record the current, opening degree and differential pressure in the preset table.

5. The throttling control method for a chiller unit as described in claim 4, characterized in that, The real-time opening E of the current electronic expansion valve is... s and the real-time pressure difference P s and the real-time current I of the compressor currently described. s The records in the preset current, opening degree, and differential pressure lookup table include: Determine the real-time opening E of the electronic expansion valve. s Whether it has been recorded in the preset current, opening degree and differential pressure lookup table; If so, then the current real-time opening degree E will be... s The preset real-time current and preset target pressure difference corresponding to the preset current, opening degree and pressure difference lookup table are replaced with the current real-time current I. s And the current real-time pressure difference P s ; If not, then add the current real-time opening degree E to the preset current, opening degree, and differential pressure lookup table. s The current real-time current I s Compared with the current real-time pressure difference P s The correspondence between them.

6. The throttling control method for a chiller unit as described in claim 2, characterized in that, Determining whether to adjust the opening of the electronic expansion valve based on the second preset opening adjustment strategy includes: According to the real-time pressure difference P s The suction superheat T of the compressor is obtained by comparing it with a preset pressure difference and suction superheat table. X ; Determine the intake superheat T X Is it within the preset superheat range? If so, maintain the opening of the electronic expansion valve; If not, adjust the opening of the electronic expansion valve.

7. The throttling control method for a chiller unit as described in claim 1, characterized in that, Also includes: When the chiller unit is started, the opening degree of the electronic expansion valve is controlled to reach the preset initial opening degree E. c ; After the chiller unit is running normally, the process continues to acquire the real-time current I of the compressor. s The steps.

8. A water chiller unit, comprising a compressor, a condenser, and an evaporator, wherein a liquid bypass circuit is provided between the condenser and the evaporator, and an electronic expansion valve is provided on the liquid bypass circuit, characterized in that, The controller of the chiller unit performs the throttling control method as described in any one of claims 1-7.

9. The chiller unit as described in claim 8, characterized in that, The chiller unit is a two-stage centrifugal chiller unit.

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