Water chilling unit and throttling control method thereof

Abstract

The invention provides a throttling control method of a water chilling unit, which comprises the following steps of: calculating the target flow capacity of an electronic expansion valve according to the real-time current of a compressor and the real-time pressure difference of the electronic expansion valve, and obtaining the target opening degree corresponding to the target flow capacity of the electronic expansion valve by inquiring a preset flow capacity and opening degree comparison table; and the opening degree of the electronic expansion valve is adjusted by taking the obtained target opening degree as a control target, so that the stability and the reliability of throttling control are improved. Compared with an existing liquid level control mode and an exhaust superheat degree control mode, a liquid level sensor and a temperature sensor are not needed, and the unit cost is reduced. And meanwhile, compared with a unit which only uses the pore plate as the throttling element, the problem that the throttling capacity of the pore plate is not well matched with the load during partial load is solved.

Description

Technical Field

[0001] The invention belongs to the field of water chillers, and more specifically, relates to a water chiller and a throttling control method thereof. Background Art

[0002] The throttling mechanism is one of the components of the air conditioner. The orifice plate is a commonly used throttling mechanism for chillers. When the orifice plate is used as a throttling element, the orifice size cannot be adjusted, and the throttling characteristics of the system cannot always be maintained in the best state, especially when the orifice is partially loaded, the throttling capacity of the orifice plate does not match the load well. A liquid bypass loop is often set between the condenser and the evaporator, and an electronic expansion valve is set on the liquid bypass loop. Since the orifice plate aperture is given and cannot be changed, the control of the electronic expansion valve is the key.

[0003] The electronic expansion valve control methods currently used mostly use the liquid level or suction and exhaust superheat as the control target, so that the electronic expansion valve opening is automatically adjusted to the target value when the unit is running. The liquid level control method adjusts the opening of the electronic expansion valve by calculating the difference between the actual evaporator liquid level and the set evaporator liquid level. When the unit is actually running, the evaporator shell and tube are in a boiling state, and the liquid level sensor has a large deviation in judging the real-time liquid level, resulting in a large fluctuation in the liquid level display value and extremely unstable operation of the unit. The suction and exhaust superheat control method adjusts the opening of the electronic expansion valve by calculating the difference between the actual suction and exhaust superheat and the target superheat. Due to the system characteristics of the centrifugal chiller, the suction superheat is much smaller than the exhaust superheat, resulting in no obvious change in the suction temperature when the electronic expansion valve is adjusted within a large range, resulting in a serious control blind spot. Therefore, the exhaust superheat control method is generally used. The above control methods require additional liquid level sensors or temperature sensors, which increases the production cost of the unit. Summary of the invention

[0004] The object of the present invention is to provide a chiller and a throttling control method thereof, so as to solve the problem that the existing throttling control method relies on sensors and leads to high costs.

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

[0006] The present invention first provides a throttling control method for a chiller, comprising:

[0007] Get the real-time current I of the compressor s , Real-time pressure difference P of 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 by using the preset flow capacity calculation rule. j , and according to the target flow capacity M j The target opening degree E of the electronic expansion valve is obtained by comparing the preset flow capacity and opening degree table. j ;

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

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

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

[0012] Further, judging 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 E s The target pressure difference P of the electronic expansion valve is obtained by comparing the preset current, opening and pressure difference table. j ;

[0014] Determine the target pressure difference P j The real-time pressure difference P s Whether the difference between them is within the preset deviation range;

[0015] If yes, maintaining the opening of the electronic expansion valve;

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

[0017] Further, at the current real-time opening degree E of the electronic expansion valve s Equal to the target opening E j When the real-time opening degree E of the current electronic expansion valve is s and the real-time pressure difference P s , and the current real-time current I of the compressor s Recorded in the preset current, opening and pressure difference comparison table.

[0018] Further, the real-time opening degree E of the current electronic expansion valve is s and the real-time pressure difference P s, and the current real-time current I of the compressor s The records in the preset current, opening and pressure difference comparison table include:

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

[0020] If so, the current real-time opening E s The preset real-time current and the preset target pressure difference corresponding to the preset current, opening and pressure difference comparison table are replaced by the current real-time current I s and the current real-time pressure difference P s ;

[0021] If not, then the current real-time opening E is added to the preset current, opening and pressure difference comparison table. s , the current real-time current I s The real-time pressure difference P s The corresponding relationship between them.

[0022] Further, judging 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 the preset pressure difference and suction superheat table. X ;

[0024] Determine the suction superheat T X Whether it is within the preset superheat range;

[0025] If yes, maintaining the opening of the electronic expansion valve;

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

[0027] Further, 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 by using the preset flow capacity calculation rule. j include:

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

[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 , calculate the flow capacity ratio Y of the electronic expansion valve, where a0, a1, a2, a3, a4, and a5 are set values;

[0030] The target flow capacity M is obtained according to the flow capacity ratio Y and the set standard flow capacity M0. j .

[0031] Furthermore, it also includes:

[0032] When the chiller is turned on, the opening of the electronic expansion valve is controlled to reach a preset initial opening E. c ;

[0033] When the chiller is operating normally, the real-time current I of the compressor is obtained. s steps.

[0034] The present invention also provides a chiller, which includes a compressor, a condenser and an evaporator. A liquid bypass circuit is arranged between the condenser and the evaporator. An electronic expansion valve is arranged on the liquid bypass circuit. The controller of the chiller executes the throttling control method as described above.

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

[0036] Compared with the prior art, the beneficial effect of the chiller and throttling control method thereof provided by the present invention is that while ensuring the throttling capacity of partial load and the matching problem of load, no liquid level sensor and temperature sensor are required in structure, which not only improves the stability and reliability of control, but also saves costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0038] Figure 1 A schematic diagram of the structure of a water chiller provided by the present invention;

[0039] Figure 2 A schematic flow chart of the throttling control method provided by the present invention;

[0040] Figure 3 A detailed flow diagram of the throttling control method provided by the present invention Figure 1 ;

[0041] Figure 4 A detailed flow diagram of the throttling control method provided by the present invention Figure 2 ;

[0042] Among them, the main marks of the drawings in the figure are:

[0043] 1. Inverter; 2. Compressor; 3. Evaporator; 4. Condenser; 5. Flasher;

[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 DESCRIPTION

[0047] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0048] The throttling mechanism is one of the components of the air conditioner. The orifice plate is a commonly used throttling mechanism for chillers. When the orifice plate is used as a throttling element, the throttling characteristics of the system cannot always be maintained in the best state because the orifice size cannot be adjusted. Especially at partial load, the throttling capacity of the orifice plate does not match the load well. A liquid bypass circuit is often set between the condenser and the evaporator, and an electronic expansion valve is set on the liquid bypass circuit. Since the orifice plate aperture is given and cannot be changed, the control of the electronic expansion valve is the key. The current electronic expansion valve control method mostly uses the liquid level or the suction and exhaust superheat as the control target, so that the electronic expansion valve opening is automatically adjusted to the target value when the unit is running. The liquid level control method is to adjust the opening of the electronic expansion valve by calculating the difference between the actual evaporator liquid level and the set evaporator liquid level. When the unit is actually running, the evaporator shell and tube are in a boiling state, and the liquid level sensor has a large deviation in judging the real-time liquid level, resulting in a large fluctuation in the liquid level display value, and the unit operation is extremely unstable. The suction and exhaust superheat control method is to adjust the opening of the electronic expansion valve by calculating the difference between the actual suction and exhaust superheat and the target superheat. Due to the system characteristics of the centrifugal chiller, the suction superheat is much smaller than the exhaust superheat, resulting in no obvious change in the suction temperature when the electronic expansion valve is adjusted within a large range, causing a serious control blind spot. Therefore, the exhaust superheat control method is generally used. The above control methods require additional liquid level sensors or temperature sensors, which increases the production cost of the unit.

[0049] In this regard, the present invention proposes a new throttling control method for a chiller, which not only improves the stability and reliability of control, but also saves costs.

[0050] like Figure 1 As shown, the throttling control method proposed in the present invention is applied to a chiller, which 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 the present invention at least includes the following steps:

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

[0053] According to the real-time current I s , real-time pressure difference P s Calculate the target flow capacity M of the electronic expansion valve using the preset flow capacity calculation rules j , and according to the target flow capacity M j The target opening degree E of the electronic expansion valve is obtained by comparing the preset flow capacity and opening degree table. j ;

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

[0055] The advantage of such a design is that the present invention calculates the target flow capacity of the electronic expansion valve according to the real-time current of the compressor and the real-time pressure difference of the electronic expansion valve, obtains the target opening corresponding to the target flow capacity of the electronic expansion valve by querying the preset flow capacity and opening comparison table, and adjusts the opening of the electronic expansion valve with the obtained target opening as the control target, thereby improving the stability and reliability of throttling control. Compared with the existing liquid level control method and exhaust superheat control method, liquid level sensor and temperature sensor are not required, which reduces the cost of the unit. At the same time, compared with the unit that only uses the orifice plate as the throttling element, it also solves the problem that the throttling capacity of the orifice plate is not well matched with the load at 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. The preset flow capacity and opening comparison table records the one-to-one correspondence between the flow capacity of the electronic expansion valve and the opening of the electronic expansion valve.

[0057] In some optional embodiments, according to the real-time current Is , real-time pressure difference P s Calculate the target flow capacity M of the electronic expansion valve 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 the first preset opening adjustment strategy or the second preset opening adjustment strategy.

[0059] The advantage of this design is that the present invention also determines in advance whether to adjust the opening of the electronic expansion valve, avoids frequent over-adjustment of the electronic expansion valve, and better improves the accuracy and reliability of throttling control. At the same time, there are multiple preset opening adjustment strategies, and the application scenarios are more extensive.

[0060] In a further alternative embodiment, if Figure 3 As shown, judging whether to adjust the opening of the electronic expansion valve based on the first preset opening adjustment strategy includes:

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

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

[0063] If yes, keep 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 infers the target pressure difference of the electronic expansion valve according to the real-time current of the compressor and the real-time opening of the electronic expansion valve, and then determines whether to adjust the opening of the electronic expansion valve according to the target pressure difference and the real-time pressure difference of the electronic expansion valve. This opening adjustment strategy is simple and easy to implement, and is suitable for various working 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 keep the opening of the electronic expansion valve;

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

[0069] If P j -P s >P 0min , then reduce the opening of the electronic expansion valve.

[0070] Among them, 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 Calculate it.

[0071] In a further optional embodiment, at the current real-time opening degree E of the electronic expansion valve s Equal to the target opening E j When the current electronic expansion valve real-time opening E s and real-time pressure difference P s , and the current compressor real-time current I s Recorded in the preset current, opening and pressure difference comparison table.

[0072] The advantage of this design is that the corresponding relationship among the compressor current, the opening of the electronic expansion valve and the pressure difference of the electronic expansion valve is continuously recorded when a high-efficiency throttling effect can be achieved, and the opening of the electronic expansion valve is timely corrected through the controller, so that the unit always performs throttling control in the high-efficiency zone.

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

[0074] Determine the real-time opening degree E of the current electronic expansion valve s Whether it has been recorded in the preset current, opening and pressure difference comparison table;

[0075] If so, the current real-time opening E s The preset real-time current and preset target pressure difference corresponding to the preset current, opening and pressure difference comparison table are replaced with the current real-time current I s and the current real-time pressure difference P s ;

[0076] If not, then add the current real-time opening E to the preset current, opening and pressure difference comparison table. s 、The current real-time current I s The current real-time pressure difference P s The corresponding relationship between them.

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

[0078] In a further alternative embodiment, if Figure 4 As shown, judging 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 suction superheat T is obtained by comparing the preset pressure difference and suction superheat table. X ;

[0080] Determine the suction superheat T X Whether it is within the preset superheat range;

[0081] If yes, keep 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 suction superheat of the compressor corresponding to the real-time pressure difference of the electronic expansion valve by querying the preset pressure difference and suction superheat comparison table, and determines whether to adjust the opening of the electronic expansion valve according to the suction superheat of the compressor. This opening adjustment strategy is simple and easy to implement, and is suitable for the specific working conditions of the unit. For example, when the compressor suction superheat is too low or the evaporation pressure is too low during the operation of the unit, the optimal adjustment of the suction superheat and part load performance is achieved, and the reliability and energy saving of the unit are improved.

[0084] Specifically, the present invention pre-stores a table comparing pressure difference and suction superheat, which can save the installation of 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 keep the opening of the electronic expansion valve;

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

[0087] If T X >T 0max , then reduce the opening of the electronic expansion valve.

[0088] Among them, 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 Calculate it.

[0089] From the perspective of suction superheat regulation, when T X >T 0max When the temperature is too high, it is determined that the superheat of the gaseous refrigerant at the evaporator outlet is too high, indicating that the gaseous refrigerant absorbs too much heat from the liquid pipe at the top of the evaporator, increasing the power consumption of the compressor. At this time, it is necessary to reduce the opening of the electronic expansion valve to reduce the flow of the liquid pipe, thereby reducing T X When T X <T 0min When the evaporator outlet gas refrigerant is judged to have no superheat, it means that the compressor suction contains liquid at this time, which will seriously affect the safe operation of the compressor. At this time, it is necessary to increase the opening of the electronic expansion valve to increase the liquid pipe flow, thereby increasing T X When T 0min ≤T X ≤T 0max It indicates that the suction superheat is within the appropriate range and there is no need to adjust the liquid pipe flow. The electronic expansion valve maintains the current opening.

[0090] From the perspective of load regulation, when the chiller is unloaded, the amount of refrigerant evaporation in the evaporator decreases, the amount of gaseous refrigerant decreases, and T X Will increase when T X Increase to greater than T 0max , the controller will reduce the opening of the electronic expansion valve to reduce the liquid pipe flow; conversely, when the chiller is loaded and running, the evaporation amount of the refrigerant in the evaporator increases, the amount of gaseous refrigerant increases, and T X will decrease when T X Reduce to less than T 0min When the pressure is too high, the controller will increase the opening of the electronic expansion valve to increase the liquid pipe flow.

[0091] In a further optional embodiment, according to the real-time current I s , real-time pressure difference P s Calculate the target flow capacity M of the electronic expansion valve using the preset flow capacity calculation rules j include:

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

[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 , calculate the flow capacity ratio Y of the electronic expansion valve, where a0, a1, a2, a3, a4, and a5 are set values;

[0094] The target flow capacity M is obtained based on the flow capacity ratio Y and the set standard flow capacity M0 j .

[0095] The advantage of such a design is that the present invention fits the calculation formula of the flow capacity ratio Y after pre-testing multiple groups of data, and it is closely related to the compressor current and the pressure difference of the electronic expansion valve, so it is 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 is turned on, the opening of the electronic expansion valve is controlled to reach the preset initial opening E c ;

[0100] When the chiller is operating normally, continue to obtain the real-time current I of the compressor s 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 E c , ensuring that the unit has a good throttling effect before entering normal operation.

[0102] In practical applications, the initial opening is usually set at 50% during factory testing. After testing all operating conditions, the initial opening is set according to the minimum opening of the electronic expansion valve that can meet the test reliability. The same set of parameters is used for subsequent settings of the same model, and the initial opening is an empirical value parameter.

[0103] In addition, after the controller receives the command that the compressor has been turned off, it controls the opening of the electronic expansion valve to be closed to 0 within the preset time T2.

[0104] like Figure 1 As shown, the chiller proposed in the present invention comprises 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 executes the throttling control method as described above.

[0105] The advantage of such a design is that the water chiller proposed by the present invention does not need to be equipped with additional liquid level sensors and temperature sensors for throttling control, thereby reducing the cost of the unit.

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

[0107] In order to better understand the present invention, the design principle of the present invention is described in detail below:

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

[0109] The evaporator 3, the condenser 4 and the flasher 5 are respectively connected to the compressor 2 through pipelines, and a primary orifice plate 61 is provided on the pipeline between the condenser 4 and the flasher 5, and a secondary orifice plate 62 is provided on the pipeline between the flasher 5 and the evaporator 3. The compressor 2, the condenser 4, the primary orifice plate 61, the flasher 5, the secondary orifice plate 62 and the evaporator 3 are connected in sequence through pipelines to form a main refrigerant circulation loop. At the same time, a liquid bypass loop 70 is also provided between the condenser 4 and the evaporator 3, and two electronic expansion valves 71 are provided on the liquid bypass loop 70.

[0110] In actual application, the high-temperature and high-pressure refrigerant is discharged to the condenser 4 through the compressor 2. After cooling and condensation, the refrigerant is divided into two paths; one path passes through the primary orifice plate 61, the flash evaporator 5 and the secondary orifice plate 62 in sequence and then enters the evaporator 3. At the same time, the gaseous refrigerant in the flash evaporator 5 is directly replenished to the air supply port of the compressor 2 through the air supply pipeline to increase the exhaust volume of the compressor 2; the other path enters the liquid bypass circuit 70, and is throttled by the electronic expansion valve 71 at this time.

[0111] According to the orifice flow calculation formula where q m is the refrigerant flow rate, ε is the expansion coefficient, C is the outflow coefficient, ρ1 is the refrigerant density, β is the aperture ratio, Δp is the front and back pressure difference, and d is the aperture.

[0112] From the above formula, we can get that the refrigerant flow is positively correlated to the orifice plate diameter and the pressure difference. The compressor current is positively correlated to the refrigerant flow, and the orifice plate diameter is positively correlated to the compressor current and inversely correlated to the pressure difference. The electronic expansion valve can be regarded as an orifice plate with a variable cross-sectional area, and the opening of the electronic expansion valve is positively correlated to the compressor current and inversely correlated to the pressure difference of the electronic expansion valve.

[0113] Based on this, the throttling control method proposed in the present invention is to calculate the opening value of the electronic expansion valve through the real-time compressor current value and the electronic expansion valve pressure difference, and adjust the electronic expansion valve with the calculated target opening as the control target, thereby improving the stability and reliability of the throttling control. At the same time, the opening of the electronic expansion valve, the electronic expansion valve pressure difference and the compressor current under stable conditions are recorded in the main board, and the operation records are continuously performed during the subsequent after-sales process. The controller controls the real-time correction, so that the unit always performs high-efficiency throttling control. Compared with the existing liquid level control method and the exhaust superheat control method, the liquid level sensor and the temperature sensor are not required, which reduces the cost of the unit. At the same time, compared with the unit that only uses the orifice plate as the throttling element, it also solves the problem that the throttling capacity of the orifice plate is not well matched with the load at partial load.

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

[0115] In summary, the beneficial effects of the chiller and throttling control method thereof provided by the present invention are that while ensuring the throttling capacity of partial load and the matching problem of load, no liquid level sensor and temperature sensor are required in structure, which not only improves the stability and reliability of control, but also 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 in the protection scope of the present invention.

Claims

1. A throttling control method for a chiller, characterized in that: include: Get the real-time current I of the compressor s , Real-time pressure difference P of 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 by using the preset flow capacity calculation rule. j , and according to the target flow capacity M j The target opening degree E of the electronic expansion valve is obtained by comparing the preset flow capacity and opening degree table. j ; According to the real-time opening E s and the target opening E j The opening degree of the electronic expansion valve is adjusted.

2. The throttling control method for a chiller according to 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 by using the preset flow capacity calculation rule. j Previously, it also included: Whether to adjust the opening of the electronic expansion valve is determined based on the first preset opening adjustment strategy or the second preset opening adjustment strategy.

3. The throttling control method for a chiller according to 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 E s The target pressure difference P of the electronic expansion valve is obtained by comparing the preset current, opening and pressure difference table. j ; Determine the target pressure difference P j The real-time pressure difference P s Whether the difference between them is within the preset deviation range; If yes, maintaining the opening of the electronic expansion valve; If not, the opening of the electronic expansion valve is adjusted.

4. The throttling control method for a chiller according to claim 3, characterized in that: At the current real-time opening degree E of the electronic expansion valve s Equal to the target opening E j When the real-time opening degree E of the current electronic expansion valve is s and the real-time pressure difference P s , and the current real-time current I of the compressor s Recorded in the preset current, opening and pressure difference comparison table.

5. The throttling control method for a chiller according to claim 4, characterized in that: The real-time opening degree E of the current electronic expansion valve s and the real-time pressure difference P s , and the current real-time current I of the compressor s The records in the preset current, opening and pressure difference comparison table include: Determine the real-time opening degree E of the current electronic expansion valve s Whether it has been recorded in the preset current, opening and pressure difference comparison table; If so, the current real-time opening E s The preset real-time current and the preset target pressure difference corresponding to the preset current, opening and pressure difference comparison table are replaced by the current real-time current I s and the current real-time pressure difference P s ; If not, then the current real-time opening E is added to the preset current, opening and pressure difference comparison table. s , the current real-time current I s The real-time pressure difference P s The corresponding relationship between them.

6. The throttling control method for a chiller according to 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 the preset pressure difference and suction superheat table. X ; Determine the suction superheat T X Whether it is within the preset superheat range; If yes, maintaining the opening of the electronic expansion valve; If not, the opening of the electronic expansion valve is adjusted.

7. The throttling control method for a chiller according to 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 by using the preset flow capacity calculation rule. j include: Calculate the real-time current I s The current ratio X2 between the set standard current I0 and the real-time pressure difference P s The pressure difference ratio X1 with the set standard pressure difference P0; 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 , calculate the flow capacity ratio Y of the electronic expansion valve, where a0, a1, a2, a3, a4, and a5 are set values; The target flow capacity M is obtained according to the flow capacity ratio Y and the set standard flow capacity M0. j .

8. The throttling control method for a chiller according to claim 1, characterized in that: Also includes: When the chiller is turned on, the opening of the electronic expansion valve is controlled to reach a preset initial opening E. c ; When the chiller is operating normally, the real-time current I of the compressor is obtained. s steps.

9. A water chiller, 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 executes the throttling control method as described in any one of claims 1-8.

10. The water chiller according to claim 9, characterized in that: The chiller is a two-stage centrifugal chiller.

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