A heat pump system and a control method for an electronic expansion valve thereof

Abstract

The present application relates to a heat pump system, in particular to a control method of an electronic expansion valve in the heat pump system, a target initial opening degree matched with a target frequency is obtained through a compressor target frequency, a return water temperature and an ambient temperature, and the electronic expansion valve is controlled to keep a certain time without valve adjustment at the target initial opening degree, after the frequency reaches a target operation frequency, a target exhaust superheat degree is calculated and a target return gas superheat degree is determined in combination with the exhaust superheat degree, and then a fine adjustment opening degree of the electronic expansion valve is obtained in combination with the obtained return gas superheat degree and a historical return gas superheat degree. The target initial opening degree can quickly match the actual operation opening degree of the electronic expansion valve and the system compressor frequency in a reasonable range; the fine adjustment opening degree can make the opening degree control of the electronic expansion valve reach an optimal state with a very high matching degree with the target frequency. The method can quickly respond to the frequency change of the compressor, prevent the problem of compressor liquid knock, and avoid the generation of high pressure protection.

Description

Technical Field

[0001] This invention relates to the field of heat pumps, and more particularly to a heat pump system and a method for controlling the electronic expansion valve in the heat pump system. Background Technology

[0002] Due to significant fluctuations in the operating environment and / or user demands of heat pumps, the frequency and pressure of heat pump systems fluctuate frequently, often resulting in the unit frequency switching from high frequency to low frequency or from low frequency to high frequency.

[0003] In existing technologies, air conditioning systems and air-source heat pump systems that use electronic expansion valves for throttling often calculate the valve opening based on target exhaust superheat and / or return superheat. Several different ranges are set according to the superheat level, and the valve opening is adjusted with a fixed adjustment waiting period, which typically remains constant. This leads to a lag in the electronic expansion valve opening adjustment compared to frequency changes. For example, when the frequency changes from low to high, the electronic expansion valve adjusts its opening based on the return superheat calculation. However, since system stabilization requires time, the calculated opening at the frequency change does not match the opening at the current operating frequency or the target frequency. Therefore, it is necessary to adjust the calculated opening at frequency changes to avoid compressor liquid slugging and high-pressure protection issues. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a heat pump system. By designing a control method for the electronic expansion valve in the heat pump system, the system can quickly and accurately control the opening of the electronic expansion valve to match the current compressor frequency when the compressor frequency fluctuates. This allows for precise control of the refrigerant flow to meet the compressor's operating frequency requirements, thus avoiding problems such as liquid slugging and high-pressure protection in the compressor.

[0005] A heat pump system includes a compressor, a four-way valve, a condenser, an electronic expansion valve, and an evaporator connected sequentially via a refrigerant circulation pipeline; a water circulation device connected to the condenser via a water pipeline; and a control device electrically and / or communicatively connected to the compressor and the electronic expansion valve. The control device includes a temperature measuring component, a pressure measuring component, and a controller. The controller is characterized by comprising a target initial opening degree calculation module, a first opening degree control module, a fine-tuning opening degree calculation module, and a second opening degree control module.

[0006] The target initial opening calculation module is used to calculate the target initial opening of the electronic expansion valve at the current moment based on the acquired compressor target frequency, the return water temperature measured by the temperature measuring component, and the ambient temperature.

[0007] The first opening control module is used to control the opening of the electronic expansion valve to remain unchanged for a first time period under the target initial opening, so that the compressor frequency reaches the target operating frequency;

[0008] The fine-tuning opening calculation module is used to calculate the fine-tuning opening of the electronic expansion valve at the current moment based on the target operating frequency obtained, the exhaust superheat at the current moment, the return superheat at the previous moment, and the return superheat at the moment before that, calculated by the temperature measuring component and the pressure measuring component.

[0009] The second opening control module is used to control the opening of the electronic expansion valve to remain unchanged for a second time period under the actual operating opening, wherein the actual operating opening of the electronic expansion valve is the sum of the target initial opening and the fine-tuning opening.

[0010] Furthermore, the target initial opening calculation module calculates the target initial opening of the electronic expansion valve at the current moment using the following formula:

[0011] K0=αF0+βT RW +γT E +η

[0012] In the formula, K0 represents the target initial opening degree of the electronic expansion valve at the current moment, F0 represents the target frequency of the compressor, and T... RW Indicates the return water temperature, T E The ambient temperature is represented by α, β, γ, and η, which are the linear coefficients of the linear equation fitted to the electronic expansion valve opening values ​​measured at different frequencies under different return water temperatures and ambient temperatures.

[0013] Furthermore, the fine-tuning opening calculation module includes a target exhaust superheat calculation unit, a target return gas superheat calculation unit, and a fine-tuning opening calculation unit, wherein,

[0014] The target exhaust superheat calculation unit is used to calculate the target exhaust superheat at the current moment based on the target operating frequency.

[0015] The target return gas superheat calculation unit is used to determine the calculation formula of the target return gas superheat at the current moment based on the relationship between the target exhaust superheat at the current moment and the exhaust superheat at the current moment, and calculate the target return gas superheat at the current moment accordingly.

[0016] The fine-tuning opening calculation unit is used to calculate the fine-tuning opening of the electronic expansion valve at the current moment based on the target return gas superheat at the current moment, the return gas superheat at the previous moment, and the return gas superheat at the moment before that.

[0017] Furthermore, the fine-tuning opening calculation module includes a target exhaust superheat calculation unit, a target return gas superheat calculation unit, and a fine-tuning opening calculation unit, wherein,

[0018] The target exhaust superheat calculation unit is used to calculate the target exhaust superheat at the current moment based on the target operating frequency.

[0019] The target return gas superheat calculation unit is used to determine the calculation formula of the target return gas superheat at the current moment based on the relationship between the target exhaust superheat at the current moment and the exhaust superheat at the current moment, and calculate the target return gas superheat at the current moment accordingly.

[0020] The fine-tuning opening calculation unit is used to calculate the fine-tuning opening of the electronic expansion valve at the current moment based on the target return gas superheat at the current moment, the return gas superheat at the previous moment, and the return gas superheat at the moment before that.

[0021] Furthermore, the target return gas superheat calculation unit is configured with the following calculation steps to calculate the target return gas superheat at the current moment:

[0022] S321 Compare the current exhaust superheat with the target exhaust superheat at the current moment:

[0023] If the exhaust superheat at the current moment is less than the target exhaust superheat at the current moment, then proceed to step S322;

[0024] If the current exhaust superheat is greater than or equal to the current target exhaust superheat and less than 40°C, then proceed to step S323.

[0025] If the current exhaust superheat is greater than or equal to 40°C and less than 45°C, then proceed to step S324.

[0026] If the exhaust superheat is greater than 45°C at the current moment, then proceed to step S325;

[0027] S322 further compares the target exhaust superheat at the current moment, the difference between the current exhaust superheat and the system set parameter, and calculates the target return gas superheat at the current moment accordingly; where the system set parameter is represented by L, and its value is greater than 2:

[0028] If the difference between the target exhaust superheat at the current moment and the exhaust superheat at the current moment is greater than 3*L, then the target return gas superheat at the current moment... Satisfying equation (3),

[0029]

[0030] (1) In the formula, P represents the target return superheat at the current moment. IO This indicates the return gas superheat parameter;

[0031] If the difference between the target exhaust superheat at the current moment and the exhaust superheat at the current moment is less than or equal to 3*L and greater than 2*L, then the target return gas superheat at the current moment satisfies equation (4).

[0032]

[0033] (2) In the formula, Indicates the target exhaust superheat at the current moment, EO t Indicates the current exhaust superheat;

[0034] If the difference between the target exhaust superheat and the current exhaust superheat is less than or equal to 2*L and greater than L, then the target return gas superheat at the current moment satisfies equation (5).

[0035]

[0036] If the difference between the target exhaust superheat and the exhaust superheat at the current moment is less than or equal to L, then the target return gas superheat at the current moment satisfies equation (6).

[0037]

[0038] S323 further compares the difference between the current exhaust superheat and the target exhaust superheat with the system setting parameter, and calculates the target return gas superheat based on this; where the system setting parameter is represented by L, and its value is greater than 2.

[0039] If the difference between the current exhaust superheat and the target exhaust superheat is greater than 3*L, then the target return gas superheat at the current moment satisfies equation (7).

[0040]

[0041] In equation (7), P represents the target return superheat at the current moment. IO This indicates the return gas superheat parameter;

[0042] If the difference between the current exhaust superheat and the target exhaust superheat is less than or equal to 3*L and greater than 2*L, then the target return gas superheat at the current moment satisfies equation (8).

[0043]

[0044] (8) In the formula, EO t This indicates the current exhaust superheat. Indicates the target exhaust superheat at the current moment;

[0045] If the difference between the current exhaust superheat and the target exhaust superheat is less than or equal to 2*L and greater than L, then the target return gas superheat at the current moment satisfies equation (9).

[0046]

[0047] If the difference between the current exhaust superheat and the target exhaust superheat is less than or equal to L, then the target return gas superheat at the current moment satisfies equation (10).

[0048]

[0049] S324 describes the target return gas superheat at the current moment. Calculate according to equation (11);

[0050]

[0051] S325 describes the target return gas superheat IO at the current moment. t G Satisfying equation (12),

[0052]

[0053] Furthermore, the fine-tuning opening calculation unit calculates the fine-tuning opening using the following formula:

[0054]

[0055] In the formula, ΔK represents the fine-tuning opening of the electronic expansion valve at the current moment, and IO t The table shows the current superheat of the return gas, IO. t-1 Indicates the superheat of the return gas at the previous moment, IO t-2 This represents the return gas superheat at the previous time step. P, I, and D are coefficients determined by the electronic expansion valve adjustment curve in the system.

[0056] Compared with existing technologies, the heat pump system of this invention, by designing the electronic expansion valve opening to add a fine-tuning degree based on the target initial opening degree corresponding to the compressor's target frequency, controls the actual operating opening of the electronic expansion valve to achieve an optimal state with a very high degree of matching with the target frequency. The fine-tuning degree is calculated based on the current exhaust superheat, the current return gas superheat, and historical return gas superheat. This control method enables the electronic expansion valve opening to respond quickly to changes in the compressor's frequency, allowing the compressor to achieve real-time and efficient output, effectively improving the overall energy efficiency of the unit; simultaneously, it effectively prevents compressor liquid slugging and avoids high-pressure protection situations.

[0057] Furthermore, this invention also proposes a control method for the electronic expansion valve based on this heat pump system, comprising the following control steps:

[0058] S10 calculates the target initial opening degree of the electronic expansion valve at the current moment based on the obtained compressor target frequency, return water temperature and ambient temperature;

[0059] S20 controls the electronic expansion valve to maintain its opening at the target initial opening for a first time period without adjusting the valve, so that the compressor frequency reaches the target operating frequency;

[0060] Based on the target operating frequency, the exhaust superheat at the current moment, the return superheat at the current moment, the return superheat at the previous moment, and the return superheat at the moment before that, S30 calculates the fine-tuning opening of the electronic expansion valve at the current moment.

[0061] S40 controls the electronic expansion valve to maintain its opening at the actual operating opening for a second time period without valve adjustment, wherein the actual operating opening of the electronic expansion valve is the sum of the target initial opening and the fine-tuning opening.

[0062] The calculation details and technical effects of this control method are similar to those of the heat pump system described above, and will not be repeated here.

[0063] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0064] Figure 1 This is a schematic diagram of a heat pump system according to an embodiment of the present invention;

[0065] Figure 2 This is a flowchart of a control method for an electronic expansion valve in a heat pump system according to an embodiment of the present invention. Detailed Implementation

[0066] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings of the embodiments of the present invention.

[0067] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that, unless otherwise stated, “a plurality” means two or more; and the term “and / or” as used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0068] In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. In the description of this application, it should be understood that the terms "first," "second," "third," etc., are used only for distinction and not to describe a specific order or sequence, nor should they be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0069] To address the issue of lag in electronic expansion valve opening adjustment when the compressor operating frequency fluctuates in a heat pump system, this invention, after research and debugging, designs a novel control method for adjusting the electronic expansion valve opening. This method determines the target return gas superheat at the current moment by comparing the current exhaust superheat (calculated after the compressor has been running at the target initial opening of the electronic expansion valve for a period of time) with the calculated target exhaust superheat. Furthermore, based on the current target return gas superheat, the current return gas superheat, and historical return gas superheat, the fine-tuning opening of the electronic expansion valve and the adjustment waiting time are obtained. This allows the target initial opening and the fine-tuning opening to jointly control the opening of the electronic expansion valve. This method effectively solves the problem of electronic expansion valve opening adjustment lagging behind frequency changes, ensuring that the electronic expansion valve opening matches the compressor frequency.

[0070] For specific implementation details, please refer to [link / reference]. Figure 1 The heat pump system proposed in this invention includes a compressor 10, a four-way valve 20, a condenser 30, an electronic expansion valve 40, an evaporator 50, a water circulation device 60, and a control device 70. The compressor 10, four-way valve 20, condenser 30, electronic expansion valve 40, and evaporator 50 are sequentially connected via refrigerant piping; the water circulation device 60 is connected to the condenser 30 via a water piping; and the control device 70 is electrically connected to the compressor 10 and the expansion valve 40.

[0071] Specifically, the exhaust port 11 of the compressor 10, the oil inlet 21 of the four-way valve 20, the first working oil port 22 of the four-way valve 20, the condenser 30, the expansion valve 40, the evaporator 50, the second working oil port 23 of the four-way valve 20, and the oil return port 24 of the four-way valve 20 are sequentially connected to the gas return port 12 of the compressor 10 to form a refrigerant circulation pipeline. The water source provided by the water tank 61 of the water circulation device 60 enters the water inlet pipeline 62 and passes through the condenser 30 to absorb the heat released during the condensation of the high-temperature refrigerant. After releasing heat, the water enters the water pipe 63 and then returns to the water tank 61 through the return water pipe 64, forming a water circulation pipeline.

[0072] The control device 70 includes a temperature measuring component 71, a pressure measuring component 72, and a controller 73. The temperature measuring component 71, the pressure measuring component 72, the compressor 10, and the electronic expansion valve 40 are electrically or communicatively connected to the controller 73. The temperature measuring component 71 includes a first temperature sensor 711, a second temperature sensor 712, a third temperature sensor 713, and a fourth temperature sensor 714. The first temperature sensor 711 is located at the port of the return water pipe 64 entering the water tank 61, and it transmits the detected return water temperature signal to the controller 73. The second temperature sensor 712 transmits the ambient temperature signal to the controller 73. The third temperature sensor 713 is located at the exhaust port 11 of the compressor 10, and it transmits the compressor 10 exhaust port temperature signal to the controller 73. The fourth temperature sensor 714 is located at the return air port 12 of the compressor 10, and it transmits the compressor 10 return air pipe temperature signal to the controller 73. The pressure measuring component 72 includes a first pressure sensor 721 and a second pressure sensor 722. The first pressure sensor 721 is located at the exhaust port 11 of the compressor 10, transmitting the compressor 10 exhaust port pressure signal to the controller 73. The second pressure sensor 722 is located at the return port 12 of the compressor 10, transmitting the compressor 10 return port pressure signal to the controller 73. The controller 73 receives measurement signals from the temperature measuring component 71, the pressure measuring component 72, and the frequency signal of the compressor 10. It also sends an adjustment signal to the electronic expansion valve 40 via an opening control program stored on the controller 73, controlling the opening adjustment of the electronic expansion valve 40. The controller 73 also includes a storage unit for storing historical measurement information.

[0073] The controller 73 is further provided with a target initial opening calculation module 100, a first opening control module 200, a fine-tuning opening calculation module 300, and a second opening control module 400. The controller 73 controls the operation of the electronic expansion valve through the following steps.

[0074] The S10 target initial opening calculation module 100 calculates the compressor target frequency F0 and the return water temperature T measured by the first temperature sensor 711 based on the obtained compressor target frequency F0. RW The ambient temperature T measured by the second temperature sensor 712 E The target initial opening degree K0 of the electronic expansion valve at the current moment is calculated.

[0075] In practical implementation, the controller 73 receives the target operating temperature information of the heat pump system set by the user, and determines the target frequency F0 of the compressor 10 corresponding to the target operating temperature according to the stored frequency increase program; at the same time, the controller 73 receives the current return water temperature T measured by the first temperature sensor 711. RW The current ambient temperature T measured by the second temperature sensor 712 EThe target initial opening calculation module 100 calculates the target frequency F0 and return water temperature T based on the obtained target frequency F0 and return water temperature T. RW and ambient temperature T E The target initial opening degree K0 of the electronic expansion valve 40 is calculated according to equation (1):

[0076] K0=αF0+βT RW +γT E +η (1)

[0077] (1) In the formula, α, β, γ, and η are the linear coefficients of the linear equation fitting the electronic expansion valve opening values ​​at different frequencies measured under different return water temperatures and ambient temperatures. Among them, the value range of α is ∈ [-20, 20], the value range of β is ∈ [-500, 500], the value range of γ is ∈ [-10, 10], and the value range of η is ∈ [-20, 10].

[0078] When the value of the target initial opening degree K0 of the electronic expansion valve 40 calculated according to formula (1) is greater than 440p, the target initial opening degree K0 of the electronic expansion valve 40 is determined to be 440p.

[0079] The S20 first opening control module 200 controls the opening of the electronic expansion valve 40 to remain unchanged for a first time period t0 under the target initial opening K0, so that the compressor frequency reaches the target operating frequency F0′.

[0080] In practical implementation, the first opening control module 200 sends a valve adjustment command to the electronic expansion valve 40 based on the target initial opening K0 calculated by the target initial opening calculation module 100 and the set valve adjustment rate, causing the electronic expansion valve 40 to adjust its opening to the target initial opening K0 according to the set valve adjustment rate. The valve adjustment rate is preferably set to 1P / s. When the first opening control module 200 receives information that the current opening of the electronic expansion valve 40 has reached the target initial opening K0, it sends a command to the electronic expansion valve 40 to maintain the current opening for a period of time t0, causing the compressor to run continuously at the target initial opening K0 for a period of time t0 until its frequency reaches the target operating frequency F′. Theoretically, the target operating frequency F′ should be equal to the target frequency F0, but in actual operation, there is a very small deviation δ between the target operating frequency F′ and the target frequency F0.

[0081] Furthermore, if the compressor target frequency F0 changes, the target initial opening K0 is recalculated, and the opening of the electronic expansion valve 40 is adjusted accordingly. This ensures that the compressor 10 operates continuously for a period t0 at the recalculated target initial opening K0′, while the electronic expansion valve 40 remains unchanged for the same period t0. If the return water temperature T... RW and / or ambient temperature T EIf a change occurs, but the compressor target frequency F0 remains unchanged, then the original calculated target initial opening degree K0 is maintained, and the opening degree of the electronic expansion valve is not adjusted.

[0082] Furthermore, if the compressor frequency is limited and cannot reach the target frequency F0, the target initial opening degree K0′ of the electronic expansion valve 40 is recalculated according to formula (1) based on the actual operating frequency F′ that the compressor 10 can reach, and the compressor 10 is continuously operated at the target initial opening degree K0′ for a period of time t0, while the electronic expansion valve 40 remains unadjusted within t0.

[0083] The preferred range for t0 is [3min, 5min].

[0084] The S30 fine-tuning opening calculation module 300 calculates the current exhaust superheat EO based on the acquired target operating frequency F0′. t Current moment, overheating IO t The previous moment's return to overheating IO t-1 And the previous moment's overheating IO t-2 The fine-tuning opening ΔK of the electronic expansion valve is calculated.

[0085] In practical implementation, the fine-tuning opening calculation module 300 includes a target exhaust superheat calculation unit 310, a target return gas superheat calculation unit 320, and a fine-tuning opening calculation unit 330.

[0086] Once the compressor frequency reaches the target operating frequency F0′, the target exhaust superheat calculation unit 310 calculates the target exhaust superheat at the current moment based on the target operating frequency F0′. The target exhaust superheat at the current moment Satisfying equation (2):

[0087]

[0088] (2) In the formula, E is a parameter set according to the average exhaust superheat during system testing.

[0089] The target return gas superheat calculation unit 320 calculates the target exhaust gas superheat based on the current time target exhaust gas superheat. And the current exhaust superheat EO t Determine the target return gas superheat at the current moment. The calculation formula is used to calculate the target return gas superheat at the current moment. Wherein, the current exhaust superheat EO t The saturation temperature is calculated from the exhaust temperature measured by the third temperature sensor 713 and the exhaust pressure measured by the first pressure sensor 721. Specifically, the target return gas superheat calculation unit 320 includes the following calculation steps.

[0090] S321 compares the current exhaust superheat EO. t With the target exhaust superheat at the current moment Size:

[0091] 1) If the current exhaust superheat is EO t Less than the target exhaust superheat at the current moment Then proceed to step S322;

[0092] 2) If the current exhaust superheat is EO t Greater than or equal to the target exhaust superheat at the current moment If the temperature is less than 40°C, then proceed to step S323;

[0093] 3) If the current exhaust superheat is EO t If the temperature is greater than or equal to 40℃ and less than 45℃, then proceed to step S324;

[0094] 4) If the current exhaust superheat is EO t If the temperature is greater than 45°C, proceed to step S325.

[0095] S322 further compares the target exhaust superheat at the current moment. Current exhaust superheat (EO) t The difference between the values ​​and the system settings parameters is used to determine the target return gas superheat at the current moment. The system setting parameter is represented by L, and its value is greater than 2:

[0096] ①. If the target exhaust superheat is at the current moment Exhaust superheat EO at the current moment t If the difference is greater than 3*L, then the target return gas superheat at the current moment... Satisfying equation (3),

[0097]

[0098] (1) In the formula, P IO This indicates the return gas superheat parameter;

[0099] ②. If the target exhaust superheat is at the current moment Exhaust superheat EO at the current moment t If the difference is less than or equal to 3*L and greater than 2*L, then the target return gas superheat at the current moment... Satisfy equation (4);

[0100]

[0101] ③. If the target exhaust superheat Exhaust superheat EO at the current moment t If the difference is less than or equal to 2*L and greater than L, then the target return gas superheat at the current moment... Satisfy equation (5);

[0102]

[0103] ④. If the target exhaust superheat Exhaust superheat EO at the current moment t If the difference is less than or equal to L, then the target return gas superheat at the current moment... Satisfy equation (6);

[0104]

[0105] S323 further compares the current exhaust superheat EO. t Current target exhaust superheat The difference between the values ​​and the system settings parameters is used to determine the target return gas superheat at the current moment. The system setting parameter is represented by L, and its value is greater than 2:

[0106] ⑤. If the current exhaust superheat is EO t With target exhaust superheat If the difference is greater than 3*L, then the target return gas superheat at the current moment... Satisfy equation (7);

[0107]

[0108] ⑥. If the current exhaust superheat is EO t With target exhaust superheat If the difference is less than or equal to 3*L and greater than 2*L, then the target return gas superheat at the current moment... Satisfy equation (8);

[0109]

[0110] ⑦. If the current exhaust superheat is EO t With target exhaust superheat If the difference is less than or equal to 2*L and greater than L, then the target return gas superheat at the current moment... Satisfy equation (9);

[0111]

[0112] ⑧. If the current exhaust superheat is EO t With target exhaust superheat If the difference is less than or equal to L, then the target return gas superheat at the current moment... Satisfy equation (10);

[0113]

[0114] S324 describes the target return gas superheat at the current moment. Calculate according to equation (11);

[0115]

[0116] S325 describes the target return gas superheat at the current moment. It satisfies equation (12).

[0117]

[0118] The fine-tuning opening calculation unit 330 calculates the target return gas superheat at the current moment based on the stated target return gas superheat. Current moment of overheating IO t The previous moment's return to overheating IO t-1 And the previous moment's overheating IO t-2 The fine-tuning opening ΔK of the electronic expansion valve is calculated. Wherein, the current return gas superheat IO... t The saturation temperature is calculated from the return gas temperature measured by the fourth temperature sensor 714 and the return gas pressure measured by the second pressure sensor 722; the return gas superheat IO at the previous moment is... t-1 And the previous moment's overheating IO t-2 The measurement information stored in its storage unit is obtained by the controller 73. Specifically, the fine-tuning opening calculation unit 330 includes the following calculation steps.

[0119] S331 determines the current superheat of the return gas based on IO. t Compared to the previous moment, the temperature of the IO return was higher. t-1 The current time increment of return gas superheat is calculated. Based on the current increase in return gas superheat Increase in superheat of return gas compared to the previous moment The growth rate R of the return gas superheat increment at the current moment is calculated. IOt Among them, the increase in superheat of the return gas at the previous moment. Based on the previous moment's return superheat IO t-1 Compared to the previous moment, the temperature of the IO (overheating) t-2 Calculated.

[0120] Specifically, the current moment's return gas superheat increment Satisfy equation (13);

[0121]

[0122] The current rate of increase in return gas superheat It satisfies equation (14).

[0123]

[0124] S332 based on the current return gas superheat IO t and the target return gas superheat at the current moment The target difference in return gas superheat Δ is calculated at the current moment. G The target difference Δ of the return gas superheat at the current moment G It satisfies equation (15).

[0125]

[0126] S333 is based on the current time-time return gas superheat increment. Current moment return gas superheat increment growth rate The difference Δ between the current time and the target superheat of the return gas G The fine-tuning opening ΔK of the electronic expansion valve is calculated, and the fine-tuning opening ΔK satisfies equation (16).

[0127]

[0128] (16) In the formula, P, I and D are coefficients determined based on the change curve of the electronic expansion valve of each system during adjustment.

[0129] The second opening control module 400 of S40 controls the opening of the electronic expansion valve 40 to remain unchanged for a second time period t at the operating opening K, wherein the operating opening K of the electronic expansion valve 40 is the sum of the target initial opening K0 and the fine-tuning opening ΔK.

[0130] In practice, the holding time t is determined as follows:

[0131] 1) Calculate the target return gas superheat at the current moment according to formulas (3) and (7). The holding time corresponding to its operating opening degree K is t = 4T;

[0132] 2) Calculate the target return gas superheat at the current moment according to formulas (4) and (8). The holding time corresponding to its operating opening degree K is t = 3T;

[0133] 3) Calculate the target return gas superheat at the current moment according to formulas (5) and (9). The holding time corresponding to its operating opening degree K is t = 2T;

[0134] 4) Calculate the target return gas superheat at the current moment according to formulas (6), (10), (11), and (12). The holding time corresponding to its operating opening degree K is t = T.

[0135] Where T represents the adjustment waiting period of the electronic expansion valve 40, which is determined based on the average time of the system adjusting the electronic expansion valve during the test.

[0136] The heat pump system proposed in this invention, when the compressor frequency fluctuates, can obtain a target initial opening degree of the electronic expansion valve that matches the target frequency by using the compressor's target frequency, the system's return water temperature, and the ambient temperature. It then quickly matches the actual operating electronic expansion valve opening degree with the compressor frequency within a reasonable range. Furthermore, it fine-tunes the electronic expansion valve opening degree by comparing the current exhaust superheat, return gas superheat, and historical return gas superheat. This ensures the electronic expansion valve opening degree achieves an optimal state with a very high degree of matching to the target frequency, enabling the compressor to achieve real-time, high-efficiency output and effectively improving the overall energy efficiency of the unit. The control method of the electronic expansion valve in this heat pump system allows the electronic expansion valve opening degree to respond quickly to changes in the compressor's frequency; simultaneously, it effectively prevents compressor liquid slugging and avoids high-pressure protection situations.

[0137] This invention provides a method for controlling the electronic expansion valve in a heat pump system, which is not limited to heat pump systems and can be applied to main units involved in frequency conversion systems.

[0138] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and the present invention also intends to include these modifications and variations.

Claims

1. A heat pump system, comprising a compressor, a four-way valve, a condenser, an electronic expansion valve, and an evaporator connected sequentially via a refrigerant circulation pipeline, a water circulation device connected to the condenser via a water pipeline, and a control device electrically and / or communicatively connected to the compressor and the electronic expansion valve, wherein the control device comprises a temperature measuring component, a pressure measuring component, and a controller, characterized in that, The controller includes a target initial opening calculation module, a first opening control module, a fine-tuning opening calculation module, and a second opening control module; wherein... The target initial opening calculation module is used to calculate the target initial opening of the electronic expansion valve at the current moment based on the acquired compressor target frequency, the return water temperature measured by the temperature measuring component, and the ambient temperature. The target initial opening K0 satisfies: In the formula, This indicates the target initial opening degree of the electronic expansion valve at the current moment. Indicates the target frequency of the compressor. Indicates the return water temperature. Indicates ambient temperature. The linear coefficients are the linear equations fitted to the electronic expansion valve opening values ​​at different frequencies measured under different return water temperatures and ambient temperatures. The first opening control module is used to control the opening of the electronic expansion valve to remain unchanged for a first time period under the target initial opening, so that the compressor frequency reaches the target operating frequency; The fine-tuning opening calculation module is used to calculate the fine-tuning opening of the electronic expansion valve at the current moment based on the target operating frequency, the exhaust superheat at the current moment, the return gas superheat at the previous moment, and the return gas superheat at the moment before that, calculated using the measurement results from the temperature and pressure measuring components. The fine-tuning opening ΔK satisfies the following: In the formula, This indicates the current fine-tuning opening of the electronic expansion valve. The table shows the current temperature of the return gas superheat. This indicates the superheat of the return gas at the previous moment. This indicates the superheat of the return gas at the time two moments prior. This indicates the current target superheat level. The coefficients determined by the adjustment curve of the electronic expansion valve in the system; Among them, the target return gas superheat at the current moment is calculated based on the target exhaust superheat at the current moment and the exhaust superheat, and the target exhaust superheat at the current moment is calculated based on the target operating frequency of the compressor; The second opening control module is used to control the opening of the electronic expansion valve to remain unchanged for a second time period under the actual operating opening, wherein the actual operating opening of the electronic expansion valve is the sum of the target initial opening and the fine-tuning opening.

2. The heat pump system according to claim 1, characterized in that, The fine-tuning opening calculation module includes a target exhaust superheat calculation unit, a target return superheat calculation unit, and a fine-tuning opening calculation unit, wherein... The target exhaust superheat calculation unit is used to calculate the target exhaust superheat at the current moment based on the target operating frequency. The target return gas superheat calculation unit is used to determine the calculation formula of the target return gas superheat at the current moment based on the relationship between the target exhaust superheat at the current moment and the exhaust superheat at the current moment, and calculate the target return gas superheat at the current moment accordingly. The fine-tuning opening calculation unit is used to calculate the fine-tuning opening of the electronic expansion valve at the current moment based on the target return gas superheat at the current moment, the return gas superheat at the previous moment, and the return gas superheat at the moment before that.

3. The heat pump system according to claim 2, characterized in that, The target exhaust superheat calculation unit calculates the target exhaust superheat at the current moment using the following formula: In the formula, This indicates the target exhaust superheat at the current moment. Indicates the target operating frequency of the compressor. These are parameters set based on the average exhaust superheat during system testing.

4. The heat pump system according to claim 3, characterized in that, The target return gas superheat calculation unit is configured with the following calculation steps to calculate the target return gas superheat at the current moment: S321: Compare the current exhaust superheat with the target exhaust superheat at the current moment: If the exhaust superheat at the current moment is less than the target exhaust superheat at the current moment, then proceed to step S322; If the current exhaust superheat is greater than or equal to the current target exhaust superheat and less than 40°C, then proceed to step S323. If the current exhaust superheat is greater than or equal to 40°C and less than 45°C, then proceed to step S324. If the exhaust superheat is greater than 45°C at the current moment, then proceed to step S325; S322: Further compare the target exhaust superheat at the current moment, the difference between the current exhaust superheat and the system set parameter, and calculate the target return gas superheat at the current moment accordingly; where the system set parameter is represented by L, and its value is greater than 2. If the difference between the target exhaust superheat and the exhaust superheat at the current moment is greater than The target return gas superheat at the current moment Satisfying equation (3), (1) In the formula, This indicates the current target superheat level. This indicates the return gas superheat parameter; If the difference between the target exhaust superheat and the exhaust superheat at the current moment is less than or equal to And greater than Then the target return gas superheat at the current moment satisfies equation (4). (2) In the formula, This indicates the target exhaust superheat at the current moment. Indicates the current exhaust superheat; If the difference between the target exhaust superheat and the current exhaust superheat is less than or equal to And greater than Then the target return gas superheat at the current moment satisfies equation (5). If the difference between the target exhaust superheat and the current exhaust superheat is less than or equal to Then the target return gas superheat at the current moment satisfies equation (6); S323: Further compare the difference between the current exhaust superheat and the target exhaust superheat with the system setting parameter, and calculate the target return gas superheat based on this; where the system setting parameter is represented by L, and its value is greater than 2. If the difference between the current exhaust superheat and the target exhaust superheat is greater than Then the target return gas superheat at the current moment satisfies equation (7). In equation (7), This indicates the current target superheat level. This indicates the return gas superheat parameter; If the difference between the current exhaust superheat and the target exhaust superheat is less than or equal to And greater than Then the target return gas superheat at the current moment satisfies equation (8). (8) In the formula, This indicates the current exhaust superheat. Indicates the target exhaust superheat at the current moment; If the difference between the current exhaust superheat and the target exhaust superheat is less than or equal to And greater than Then the target return gas superheat at the current moment satisfies equation (9). If the difference between the current exhaust superheat and the target exhaust superheat is less than or equal to Then the target return gas superheat at the current moment satisfies equation (10); S324: The target return gas superheat at the current moment Calculate according to equation (11); S325: The target return gas superheat at the current moment Satisfying equation (12), 5. The heat pump system according to claim 4, characterized in that, The second time period is determined in the following way: The holding time corresponding to the actual operating opening is calculated based on the target return gas superheat at the current moment according to formulas (3) and (7). ; The holding time corresponding to the actual operating opening is calculated based on the target return gas superheat at the current moment according to formulas (4) and (8). ; The holding time corresponding to the actual operating opening is calculated based on the target return gas superheat at the current moment according to formulas (5) and (9). ; The target return gas superheat is calculated based on formulas (6), (10), (11), and (12), and the holding time corresponding to its actual operating opening is determined. ; in, This indicates the adjustment waiting period for the electronic expansion valve.

6. A method for controlling an electronic expansion valve in a heat pump system, the heat pump system comprising a compressor, a four-way valve, a condenser, an electronic expansion valve, and an evaporator connected sequentially via a refrigerant circulation pipeline, a water circulation device connected to the condenser via a water pipeline, and a control device electrically or communicatively connected to the compressor and the electronic expansion valve, the control device comprising a temperature measuring component, a pressure measuring component, and a controller, characterized in that... Controlling the electronic expansion valve of the heat pump system includes the following steps: S10 calculates the target initial opening degree of the electronic expansion valve at the current moment based on the obtained compressor target frequency, return water temperature, and ambient temperature. The target initial opening degree K0 satisfies: In the formula, This indicates the target initial opening degree of the electronic expansion valve at the current moment. Indicates the target frequency of the compressor. Indicates the return water temperature. Indicates ambient temperature. The linear coefficients are the linear equations fitted to the electronic expansion valve opening values ​​at different frequencies measured under different return water temperatures and ambient temperatures. S20 controls the electronic expansion valve to maintain its opening at the target initial opening for a first time period without adjusting the valve, so that the compressor frequency reaches the target operating frequency; S30 calculates the fine-tuning opening of the electronic expansion valve at the current moment based on the acquired target operating frequency, the current exhaust superheat, the current return superheat, the previous return superheat, and the return superheat of the moment before that. The fine-tuning opening ΔK satisfies: In the formula, This indicates the current fine-tuning opening of the electronic expansion valve. The table shows the current temperature of the return gas superheat. This indicates the superheat of the return gas at the previous moment. This indicates the superheat of the return gas at the time two moments prior. This indicates the current target superheat level. The coefficients determined by the adjustment curve of the electronic expansion valve in the system; Among them, the target return gas superheat at the current moment is calculated based on the target exhaust superheat at the current moment and the exhaust superheat, and the target exhaust superheat at the current moment is calculated based on the target operating frequency of the compressor; S40 controls the electronic expansion valve to maintain its opening at the actual operating opening for a second time period without valve adjustment, wherein the actual operating opening of the electronic expansion valve is the sum of the target initial opening and the fine-tuning opening.

7. The control method according to claim 6, characterized in that, Step S30 includes the following sub-steps: S31 Calculates the target exhaust superheat at the current moment based on the target operating frequency; S32 Determines the calculation formula for the target return gas superheat at the current moment based on the relationship between the target exhaust superheat at the current moment and the exhaust superheat at the current moment, and calculates the target return gas superheat at the current moment accordingly. S33 calculates the fine-tuning opening of the electronic expansion valve at the current moment based on the target return gas superheat at the current moment, the return gas superheat at the previous moment, and the return gas superheat at the moment before that.

8. The control method according to claim 7, characterized in that, The target exhaust superheat at the current moment, as described in step S31, satisfies the following formula: In the formula, This indicates the target exhaust superheat at the current moment. Indicates the target operating frequency of the compressor. These are parameters set based on the average exhaust superheat during system testing.

9. The control method according to claim 8, characterized in that, Step S32 includes the following sub-steps: S321: Compare the current exhaust superheat with the target exhaust superheat at the current moment: If the exhaust superheat at the current moment is less than the target exhaust superheat at the current moment, then proceed to step S322; If the current exhaust superheat is greater than or equal to the current target exhaust superheat and less than 40°C, then proceed to step S323. If the current exhaust superheat is greater than or equal to 40°C and less than 45°C, then proceed to step S324. If the exhaust superheat is greater than 45°C at the current moment, then proceed to step S325; S322: Further compare the target exhaust superheat at the current moment, the difference between the current exhaust superheat and the system set parameter, and calculate the target return gas superheat at the current moment accordingly; where the system set parameter is represented by L, and its value is greater than 2. If the difference between the target exhaust superheat and the exhaust superheat at the current moment is greater than The target return gas superheat at the current moment Satisfying equation (3), (1) In the formula, This indicates the current target superheat level. This indicates the return gas superheat parameter; If the difference between the target exhaust superheat and the exhaust superheat at the current moment is less than or equal to And greater than Then the target return gas superheat at the current moment satisfies equation (4). (2) In the formula, This indicates the target exhaust superheat at the current moment. Indicates the current exhaust superheat; If the difference between the target exhaust superheat and the current exhaust superheat is less than or equal to And greater than Then the target return gas superheat at the current moment satisfies equation (5). If the difference between the target exhaust superheat and the current exhaust superheat is less than or equal to Then the target return gas superheat at the current moment satisfies equation (6); S323: Further compare the difference between the current exhaust superheat and the target exhaust superheat with the system setting parameter, and calculate the target return gas superheat based on this; where the system setting parameter is represented by L, and its value is greater than 2. If the difference between the current exhaust superheat and the target exhaust superheat is greater than Then the target return gas superheat at the current moment satisfies equation (7). In equation (7), This indicates the current target superheat level. This indicates the return gas superheat parameter; If the difference between the current exhaust superheat and the target exhaust superheat is less than or equal to And greater than Then the target return gas superheat at the current moment satisfies equation (8). (8) In the formula, This indicates the current exhaust superheat. Indicates the target exhaust superheat at the current moment; If the difference between the current exhaust superheat and the target exhaust superheat is less than or equal to And greater than Then the target return gas superheat at the current moment satisfies equation (9). If the difference between the current exhaust superheat and the target exhaust superheat is less than or equal to Then the target return gas superheat at the current moment satisfies equation (10); S324: The target return gas superheat at the current moment Calculate according to equation (11); S325: The target return gas superheat at the current moment Satisfying equation (12), 10. The control method according to claim 9, characterized in that, Step S40: The second time period is determined in the following manner: The holding time corresponding to the actual operating opening is calculated based on the target return gas superheat at the current moment according to formulas (3) and (7). ; The holding time corresponding to the actual operating opening is calculated based on the target return gas superheat at the current moment according to formulas (4) and (8). ; The holding time corresponding to the actual operating opening is calculated based on the target return gas superheat at the current moment according to formulas (5) and (9). ; The target return gas superheat is calculated based on formulas (6), (10), (11), and (12), and the holding time corresponding to its actual operating opening is determined. ; in, This indicates the adjustment waiting period for the electronic expansion valve.

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