A heat pump system with low ambient temperature control mode

Abstract

This invention relates to a heat pump system with a low ambient temperature control mode. When the unit's exhaust temperature is low, the main electronic expansion valve controls the return gas superheat, and the auxiliary electronic expansion valve controls the economizer superheat, ensuring sufficient subcooling of the main refrigerant to improve the evaporator's heat absorption capacity. When the unit's exhaust temperature is high, the system determines whether the flow rate of the auxiliary refrigerant controlled by the auxiliary electronic expansion valve is sufficient, thereby adjusting the main electronic expansion valve to cooperate with the auxiliary electronic expansion valve in lowering the exhaust temperature and improving the unit's reliability. Simultaneously, by determining the adjustment range of the main electronic expansion valve according to different ambient and water temperatures, it prevents the main electronic expansion valve from opening too large or too small during adjustment. This overcomes the problems of incomplete refrigerant evaporation and liquid carryover in the return gas caused by an excessively large opening of the main electronic expansion valve at low ambient temperatures, and the problems of ineffective cooling and overheating of the compressor motor caused by an excessively small opening of the main electronic expansion valve.

Description

Technical Field

[0001] This invention relates to the field of heat pump system control, and more particularly to a heat pump system with a low ambient temperature control mode. Background Technology

[0002] Heat pump systems are a highly efficient and environmentally friendly energy utilization technology. Their core working principle is the reverse Carnot cycle, which uses a small amount of electricity or other energy to transfer heat energy from a low-temperature heat source to a high-temperature environment, achieving heating or cooling. Heat pump systems absorb low-temperature heat energy from the air with minimal electricity, compress it into high-temperature heat energy using a compressor, and then transfer it to the location requiring heating or cooling. They are highly favored by consumers and users and are widely used for cooling and hot water supply in hotels, schools, hospitals, saunas, beauty salons, swimming pools, laundries, and other places.

[0003] With the development of heat pump technology, more and more heat pump heating applications are being used in cold and frigid regions with low ambient temperatures. To ensure system reliability under low ambient temperature conditions, existing heat pump systems employ vapor injection enthalpy enhancement technology, branching off a secondary refrigerant line from the main refrigerant supply line. This secondary refrigerant, after being throttled by an auxiliary electronic expansion valve, enters the economizer and exchanges heat with the main refrigerant line (which leads to the evaporator). After evaporation, it enters the compressor's intermediate-pressure chamber, mixing with the gas inside, thereby reducing the exhaust temperature. Based on this, under low ambient temperature conditions, the main control method for the heat pump system employs a scheme where the main electronic expansion valve opening is fixed, and the auxiliary electronic expansion valve opening is automatically adjusted. The specific control method is as follows:

[0004] When the ambient temperature is ≤-15℃, the fixed opening value of the main electronic expansion valve is set according to the water temperature and ambient temperature segments for system operation:

[0005] When -25℃ < ambient temperature ≤ -15℃, if the water temperature ≤ 30℃, the main electronic expansion valve has a fixed opening value of 190P; if the water temperature > 30℃, the main electronic expansion valve has a fixed opening value of 170P.

[0006] When -35℃≤Ambient Temperature≤-25℃, if the water temperature≤30℃, the main electronic expansion valve has a fixed opening value of 160P; if the water temperature>30℃, the main electronic expansion valve has a fixed opening value of 140P.

[0007] Since the total system circulation volume remains unchanged, the opening degree of the main and auxiliary electronic valve expansion valves affects the flow rate of the refrigerant in both the main and auxiliary paths. Therefore, the above control method has the following problems:

[0008] 1) The opening of the main electronic expansion valve is fixed and cannot be adjusted in real time according to the superheat. This results in the evaporator area not being fully utilized when the superheat is too high, and the risk of liquid slugging in the compressor when the superheat is too low, indicating poor adaptability.

[0009] 2) The opening of the main electronic expansion valve is fixed and cannot make more precise adaptive adjustments according to changes in ambient temperature and water temperature. Even if the opening of the main electronic expansion valve is divided according to different water temperatures within the same ambient temperature range, the division is too coarse. For example, water temperatures of 30 degrees and 55 degrees correspond to the same fixed opening, but the actual opening of the main electronic expansion valve adapted to the two water temperatures is quite different. The main electronic expansion valve determines the fixed opening according to the high water temperature. When the water temperature is low, the opening of the main electronic expansion valve is too small, resulting in excessive overheating of the return gas, excessive pressure ratio, and easy occurrence of high exhaust gas.

[0010] 3) When the opening ratio of the main electronic expansion valve is not appropriate, the auxiliary electronic expansion valve may open to its maximum and there may be no refrigerant in the auxiliary circuit, which will prevent the exhaust temperature from being reduced and result in poor reliability. Summary of the Invention

[0011] Based on this, the purpose of the present invention is to provide a heat pump system with a low ambient temperature control mode. This heat pump system ensures the reliability of the unit at low ambient temperatures by limiting the maximum and minimum opening of the main electronic expansion valve and by using different control methods for the main electronic expansion valve and the auxiliary electronic expansion valve through real-time monitoring of the unit's exhaust temperature.

[0012] A heat pump system with a low ambient temperature control mode includes a compressor, a four-way valve, a water-side heat exchanger, an economizer, a main electronic expansion valve, an auxiliary electronic expansion valve, an air-side heat exchanger, and a temperature detection module, all connected sequentially via a refrigerant circulation pipeline. A controller is electrically and / or communicatively connected to the main electronic expansion valve, the auxiliary electronic expansion valve, and the temperature detection module. The economizer includes a main refrigerant flow path and an auxiliary refrigerant flow path. The main refrigerant flow path is connected to the water-side heat exchanger and the main electronic expansion valve at both ends, while the auxiliary refrigerant flow path is connected to the compressor's intermediate pressure chamber and the auxiliary electronic expansion valve at both ends. The auxiliary electronic expansion valve is located on the refrigerant pipeline connecting the main and auxiliary refrigerant flow paths. The controller performs low ambient temperature control of the heat pump system in the following manner:

[0013] S20 obtains the current exhaust temperature. Determine the exhaust temperature at the current moment. Exhaust temperature range:

[0014] If exhaust temperature First exhaust temperature range Execute step S30;

[0015] If exhaust temperature Second exhaust temperature range Execute step S40;

[0016] If exhaust temperature In the third exhaust temperature range Execute step S50;

[0017] in, The first exhaust temperature threshold, This is the second exhaust temperature threshold, and

[0018] The S30 controls the opening of the main electronic expansion valve to be adjusted according to the return gas superheat, and the opening of the auxiliary electronic expansion valve to be adjusted according to the economizer superheat.

[0019] S40 obtains the current opening degree of the auxiliary electronic expansion valve. Determine the opening degree of the auxiliary electronic expansion valve at the current moment. Is it less than the preset auxiliary electronic expansion valve opening control threshold?

[0020] If so, control the opening of the main electronic expansion valve. Maintain the current opening degree and adjust the opening degree of the auxiliary electronic expansion valve according to the exhaust temperature;

[0021] If not, then further obtain the duration of this condition:

[0022] If the duration is greater than or equal to one valve control cycle, obtain the exhaust temperature change value for that valve control cycle. And determine the change in exhaust temperature. The changing trend is used to control the opening degree of the main electronic expansion valve and the auxiliary electronic expansion valve according to the changing trend;

[0023] If the duration is less than one valve control cycle, continuously obtain the exhaust temperature;

[0024] The S50 controls the auxiliary electronic expansion valve to its maximum opening and acquires the exhaust temperature after a first time interval t1. Calculate the change in exhaust temperature And based on the change in exhaust temperature Trends in change and exhaust temperature Adjustment of the opening degree of the main electronic expansion valve;

[0025] The opening degree of the main electronic expansion in steps S30 to S50 should be between the maximum and minimum opening degree values ​​determined under the reference opening degree determined by the corresponding ambient temperature and outlet water temperature.

[0026] Furthermore, the method for adjusting the opening degree of the main electronic expansion valve in step S30 according to the return gas superheat is as follows:

[0027] When heating, obtain the current return gas temperature. Coil temperature Calculate the return gas superheat at the current moment. Based on the current superheat of the return gas Previous moment return superheat Target return gas superheat The opening degree of the main electronic expansion valve is controlled to meet the following requirements:

[0028] in

[0029] In the formula, This indicates the current opening degree of the main electronic expansion valve. This indicates the opening degree of the main electronic expansion valve at the previous moment, κ. P-Z κ represents the superheat proportionality coefficient of the main electronic expansion valve. D-Z This represents the differential coefficient of superheat of the main electronic expansion valve;

[0030] During cooling, obtain the current return gas temperature. Throttling temperature Calculate the return gas superheat at the current moment. Based on the current superheat of the return gas Previous moment return superheat Target return gas superheat The opening degree of the main electronic expansion valve is controlled to meet the following requirements:

[0031] in

[0032] Furthermore, the method for adjusting the opening degree of the auxiliary electronic expansion valve in step S30 according to the superheat of the economizer is as follows:

[0033] Get the current inlet temperature of the economizer outlet temperature Calculate the current superheat Based on the current overheat level Overheating at the previous moment Target overheating The opening degree of the auxiliary electronic expansion valve is controlled to meet the following requirements:

[0034] in

[0035] In the formula: This indicates the current opening degree of the auxiliary electronic expansion valve. κ represents the opening degree of the auxiliary electronic expansion valve at the previous moment. P-F κ represents the superheat proportionality coefficient of the auxiliary electronic expansion valve. D-F This represents the differential coefficient of superheat of the auxiliary electronic expansion valve.

[0036] Furthermore, the method by which the opening degree of the auxiliary electronic expansion valve is adjusted according to the exhaust temperature in step S40 is as follows:

[0037] Based on the current exhaust temperature Exhaust temperature at the previous moment Target exhaust temperature Controlling the opening degree of the auxiliary electronic expansion valve satisfy;

[0038]

[0039] In the formula: This indicates the current opening degree of the auxiliary electronic expansion valve. α represents the opening degree of the auxiliary electronic expansion valve at the previous moment. P-F α represents the exhaust proportional coefficient of the auxiliary electronic expansion valve. D-F This indicates the differential value of the exhaust gas from the auxiliary electronic expansion valve.

[0040] Furthermore, the adjustment of the opening degree of the main electronic expansion valve and the auxiliary electronic expansion valve according to the changing trend in step S40 specifically involves:

[0041] If the exhaust temperature changes If the value is greater than 1, it indicates an upward trend. The auxiliary electronic expansion valve is controlled to maintain its current opening, while the main electronic expansion valve is closed by 6P / T.

[0042] If the exhaust temperature changes If the value is less than or equal to 1 and greater than or equal to -1, in order to maintain the trend, the opening degree of the main electronic expansion valve and the opening degree of the auxiliary electronic expansion valve are controlled to maintain the current opening degree.

[0043] If the exhaust temperature changes If the value is less than -1, it indicates a downward trend; therefore, the opening of the auxiliary electronic expansion valve should be controlled accordingly. Adjustments are made to maintain the current opening degree of the main electronic expansion valve;

[0044] Among them, the change value of exhaust temperature The exhaust temperature during the current valve control cycle Average exhaust temperature compared to the previous valve control cycle T-1 The difference, where T is the valve control cycle.

[0045] Furthermore, in step S50, the adjustment of the main electronic expansion valve opening based on the changing trend of the exhaust temperature and the exhaust temperature is specifically as follows:

[0046] If the exhaust temperature changes A value greater than 1 indicates an upward trend, and:

[0047] Such as exhaust temperature Less than the third exhaust temperature threshold The opening of the main electronic expansion valve is reduced to 6P / t1;

[0048] Such as exhaust temperature Greater than or equal to the third exhaust temperature threshold The opening of the main electronic expansion valve is reduced by 10P / t1.

[0049] If the exhaust temperature changes Less than or equal to 1 and greater than or equal to -1, in order to maintain the trend, and:

[0050] Such as exhaust temperature Less than the third exhaust temperature threshold The opening of the main electronic expansion valve is reduced to 6P / T;

[0051] Such as exhaust temperature Greater than or equal to the third exhaust temperature threshold The opening of the main electronic expansion valve is reduced by 10P / T.

[0052] If the exhaust temperature changes If the value is less than -1, it indicates a downward trend, so the main electronic expansion valve is controlled to close slightly at 6P / T.

[0053] Where T is the valve control cycle.

[0054] Furthermore, the maximum and minimum aperture values ​​of the main electron expansion are determined in the following manner:

[0055] Get the current ambient temperature Determine the ambient temperature at the current moment. Ambient temperature range:

[0056] If the ambient temperature First ring temperature range

[0057] When the outlet water temperature Less than or equal to the outlet water temperature threshold The maximum opening value K of the main electronic expansion valve is determined based on the first opening reference value K1 = 190P. 1-max =190P + 80P and minimum opening value K 1-min =190P-30P;

[0058] When the outlet water temperature greater than the outlet water temperature threshold The maximum opening value K of the main electronic expansion valve is determined based on the second opening reference value K2 = 170P. 2-max =170P + 80P and minimum opening value K 2-min =170P - 30P;

[0059] If the ambient temperature Second ring temperature range

[0060] When the outlet water temperature Less than or equal to the outlet water temperature threshold The maximum opening value K of the main electronic expansion valve is determined based on the third opening reference value K3 = 160P. 3-max =160P + 60P and minimum opening value K 3-min =160P-20P;

[0061] When the outlet water temperature greater than the outlet water temperature threshold The maximum opening value K of the main electronic expansion valve is determined based on the fourth opening reference value K4 = 140P. 4-max =140P + 60P and minimum opening value K 4-min =140P - 20P;

[0062] in, The first temperature threshold, This is the second temperature threshold, and

[0063] Furthermore, it also includes step S10:

[0064] Get the current ambient temperature

[0065] If the ambient temperature Greater than the low ambient temperature mode start-up threshold The main electronic expansion valve and auxiliary electronic expansion valve of the control unit are adjusted according to the existing program;

[0066] If the ambient temperature Less than or equal to the low ambient temperature mode start-up threshold And greater than or equal to the unit start-up threshold The control unit starts the low ambient temperature control mode and executes step S20;

[0067] If the ambient temperature Less than the unit start-up threshold Control unit shutdown;

[0068] Low ambient temperature mode start-up threshold The temperature is -15℃; the unit start-up threshold is... The temperature is -35℃.

[0069] Compared with existing technologies, the heat pump system provided by this invention, when the unit's exhaust temperature is low, uses the main electronic expansion valve to control the return gas superheat, ensuring full utilization of the evaporator area and preventing liquid return; the auxiliary electronic expansion valve controls the economizer superheat, ensuring full utilization of the economizer and sufficient subcooling of the main refrigerant to improve the evaporator's heat absorption capacity. When the unit's exhaust temperature is high, the system determines whether the flow rate of the auxiliary refrigerant controlled by the auxiliary electronic expansion valve is sufficient, thereby adjusting the main electronic expansion valve to cooperate with the auxiliary electronic expansion valve to lower the exhaust temperature and improve the unit's reliability. Simultaneously... The adjustment range of the main electronic expansion valve is determined according to different ambient and water temperatures. This prevents the main electronic expansion valve from opening too large or too small during adjustment. It overcomes the problems of incomplete refrigerant evaporation and liquid carryover in the return gas caused by excessive opening of the main electronic expansion valve when the cooling capacity and evaporator evaporation are low at low ambient temperatures. It also overcomes the problems of insufficient cooling and overheating of the compressor motor caused by insufficient refrigerant circulation and insufficient refrigerant cooling the compressor motor when the main electronic expansion valve opening is too small at low ambient temperatures. Furthermore, it addresses the problems of lower evaporation pressure, increased return gas overheating, increased pressure ratio, and increased exhaust temperature.

[0070] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0071] Figure 1 This is a schematic diagram of the system structure and refrigerant flow direction in heating mode according to an embodiment of the present invention;

[0072] Figure 2 This is a flowchart of an electronic expansion valve control method according to an embodiment of the present invention. Detailed Implementation

[0073] 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.

[0074] To address the problems of existing heat pump systems suitable for low ambient temperature conditions, which rely on a fixed main electronic expansion valve opening and automatic adjustment of the auxiliary electronic expansion valve opening, this invention proposes a heat pump system with a low ambient temperature control mode. This system addresses issues such as insufficient evaporator area utilization due to excessive superheat, the risk of liquid slugging in the compressor due to insufficient superheat, and the problem of excessive return gas superheat, excessive pressure ratio, and high discharge pressure when the main electronic expansion valve's opening is determined based on high water temperature. Furthermore, an inappropriate main electronic expansion valve opening ratio can lead to insufficient refrigerant in the auxiliary circuit. After research and testing, this invention proposes a heat pump system with a low ambient temperature control mode. The control method for the low ambient temperature electronic expansion valve in this system includes: determining the maximum and minimum opening of the main electronic expansion valve based on the unit's ambient and water temperatures; real-time monitoring of the unit's discharge temperature; adjusting the main electronic expansion valve based on the unit's return gas superheat when the discharge temperature is low, and adjusting the auxiliary electronic expansion valve based on the economizer's superheat when the discharge temperature is high; and fixing or reducing the opening of the main electronic expansion valve to ensure sufficient refrigerant flow in the auxiliary circuit when the discharge temperature is high.

[0075] 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 water-side heat exchanger 30, a liquid receiver 40, an economizer 50, a main electronic expansion valve 61, an auxiliary electronic expansion valve 62, an air-side heat exchanger 70, a temperature detection module 80, a controller (not shown), and other auxiliary pipe fittings, all connected via refrigerant piping. The controller is electrically or communicatively connected to the compressor 10, the main electronic expansion valve 61, the auxiliary electronic expansion valve 62, and the temperature detection module 80.

[0076] The economizer 50 includes a main refrigerant flow path 51 and an auxiliary refrigerant flow path 52. The main refrigerant flow path 51 is connected to the liquid receiver 40 and the main electronic expansion valve 61 at both ends, respectively. The auxiliary refrigerant flow path 52 is connected to the intermediate pressure chamber of the compressor 10 and the auxiliary electronic expansion valve 62 at both ends, respectively. Furthermore, a filter is also provided on the refrigerant pipeline connecting the main refrigerant flow path 51 to the liquid receiver 40.

[0077] The main electronic expansion valve 61 is installed on the refrigerant pipeline from the main refrigerant flow path 51 of the economizer 50 to the air-side heat exchanger 70, and is used to throttle the refrigerant entering the main pipeline.

[0078] The auxiliary electronic expansion valve 62 is installed on the refrigerant pipeline connecting the main refrigerant flow path 51 and the auxiliary refrigerant flow path 52 of the economizer 50, and is used to throttle the refrigerant flowing from the main refrigerant flow path 51 into the auxiliary refrigerant flow path 52.

[0079] The temperature detection module 80 includes a first temperature sensor 81, a second temperature sensor 82, a third temperature sensor 83, a fourth temperature sensor 84, a fifth temperature sensor 85, a sixth temperature sensor 86, a seventh temperature sensor 87, an eighth temperature sensor 88, and a ninth temperature sensor 89. The first temperature sensor 81 is located at the discharge end of the compressor 10 and is used to collect the actual discharge temperature T of the compressor 10. PQ and the actual exhaust temperature T PQ The data is transmitted to the controller. The second temperature sensor 82 is located at the return gas end of the compressor 10 and is used to collect the actual return gas temperature T of the compressor 10. HQ and the actual return gas temperature T HQ The data is transmitted to the controller. A third temperature sensor 83 is located at the inlet of the water-side heat exchanger 30 to collect the inlet water temperature T. in-w and the inlet water temperature T w-in The data is transmitted to the controller. The fourth temperature sensor 84 is located at the outlet of the water-side heat exchanger 30 and is used to collect the outlet water temperature T. w-out and set the outlet water temperature T out-w The data is transmitted to the controller. The fifth temperature sensor 85 is located at the inlet of the economizer 50 and is used to collect the intake air temperature T. JQ And the intake air temperature T JQ The data is transmitted to the controller. The sixth temperature sensor 86 is located at the outlet of the economizer 50 and is used to collect the outlet gas temperature T. CQ and the outlet temperature T CQ The data is transmitted to the controller. The seventh temperature sensor, 87, is used to collect the ambient temperature T. H and the ambient temperature T H The data is transmitted to the controller. The seventh temperature sensor 87 can be located on the outside of the air-side heat exchanger 70 or on the heat pump system casing; this application makes no limitation on this. The eighth temperature sensor 88 is located on the coil of the air-side heat exchanger 70 and is used to collect the coil temperature T of the air-side heat exchanger 70. 盘管 and the coil temperature T 盘管 The data is transmitted to the controller. The ninth temperature sensor 89 is located upstream of the main expansion valve 61 and is used to measure the throttling temperature T. 节流 and the throttling temperature T 节流 Transmitted to the controller.

[0080] The controller receives the temperature signal collected by the temperature detection module 80 and controls the opening degree of the main electronic expansion valve and the auxiliary electronic expansion valve according to the stored calculation and judgment program.

[0081] For details, please refer to Figure 2 The controller of the heat pump system of the present invention controls the main electronic expansion valve and the auxiliary electronic expansion valve by means of the following method.

[0082] S10 obtains the current ambient temperature.

[0083] If the ambient temperature Greater than the low ambient temperature mode start-up threshold The main electronic expansion valve and auxiliary electronic expansion valve of the control unit are adjusted according to the existing program;

[0084] If the ambient temperature Less than or equal to the low ambient temperature mode start-up threshold And greater than or equal to the unit start-up threshold The control unit starts the low ambient temperature control mode and executes step S20;

[0085] If the ambient temperature Less than the unit start-up threshold Control unit to shut down.

[0086] In one embodiment, the low ambient temperature mode activation threshold The temperature is -15℃; the unit start-up threshold is... The temperature is -35℃.

[0087] S20 obtains the current exhaust temperature. Determine the exhaust temperature at the current moment. Exhaust temperature range:

[0088] If exhaust temperature First exhaust temperature range That is, exhaust temperature Less than the first exhaust temperature threshold Execute step S30;

[0089] If exhaust temperature Second exhaust temperature range That is, exhaust temperature Greater than or equal to the first exhaust temperature threshold And less than or equal to the second exhaust temperature threshold Execute step S40;

[0090] If exhaust temperature In the third exhaust temperature range That is, exhaust temperature Greater than the second exhaust temperature threshold Perform step S50.

[0091] In one embodiment, the first exhaust temperature threshold The second exhaust temperature threshold is 95°C. If the temperature is 100℃, then the first exhaust temperature range is (, 95℃), the second exhaust temperature range is [95℃, 100℃], and the third exhaust temperature range is (100℃, ).

[0092] The S30 controls the opening of the main electronic expansion valve to be adjusted according to the return gas superheat, and the opening of the auxiliary electronic expansion valve to be adjusted according to the economizer superheat. The opening of the main electronic expansion valve is between the maximum and minimum opening values ​​determined by the corresponding ambient temperature range and the corresponding outlet water temperature.

[0093] The maximum and minimum opening values ​​of the main electronic expansion valve are determined by step S10.

[0094] In one embodiment, the opening degree of the main electronic expansion valve is adjusted according to the return gas superheat as follows:

[0095] Get the current return air temperature Coil temperature (Obtaining throttling temperature during cooling) ), calculate the return gas superheat at the current moment. Based on the current superheat of the return gas Target return gas superheat The opening degree of the main electronic expansion valve is controlled to meet the following requirements:

[0096]

[0097] The current moment's return superheat satisfy:

[0098]

[0099] or

[0100] In the formula: This indicates the current opening degree of the main electronic expansion valve. This indicates the opening degree of the main electronic expansion valve at the previous moment, κ. P-Z κ represents the superheat proportionality coefficient of the main electronic expansion valve. D-Z This represents the differential coefficient of superheat of the main electronic expansion valve. This indicates the superheat of the return gas at the previous moment.

[0101] The method for adjusting the opening degree of the auxiliary electronic expansion valve according to the superheat of the economizer is as follows:

[0102] Get the current inlet temperature of the economizer outlet temperature Calculate the current superheat Based on the current overheat level Target overheating The opening degree of the auxiliary electronic expansion valve is controlled to meet the following requirements:

[0103]

[0104] Among them, the current moment overheating satisfy:

[0105]

[0106] In the formula: This indicates the current opening degree of the auxiliary electronic expansion valve. κ represents the opening degree of the auxiliary electronic expansion valve at the previous moment. P-F κ represents the superheat proportionality coefficient of the auxiliary electronic expansion valve. D-F This represents the differential coefficient of superheat of the auxiliary electronic expansion valve. This indicates the overheating level at the previous moment.

[0107] This step is used when the unit's exhaust temperature is low. The main electronic expansion valve controls the return gas superheat to ensure full utilization of the evaporator area and prevent liquid return. The auxiliary electronic expansion valve controls the economizer superheat to ensure full utilization of the economizer and sufficient subcooling to improve the evaporator's heat absorption capacity.

[0108] S40 obtains the current opening degree of the auxiliary electronic expansion valve. Determine the opening degree of the auxiliary electronic expansion valve at the current moment. Is it less than the preset auxiliary electronic expansion valve opening control threshold?

[0109] If so, it means the current opening degree of the auxiliary electronic expansion valve. Less than the auxiliary electronic expansion valve opening control threshold Control the opening degree of the main electronic expansion valve Maintain the current opening degree and adjust the opening degree of the auxiliary electronic expansion valve according to the exhaust temperature;

[0110] If no, that is, the current opening degree of the auxiliary electronic expansion valve. Greater than or equal to the auxiliary electronic expansion valve opening control threshold Then, the duration of this situation can be obtained:

[0111] If the duration is greater than or equal to one valve control cycle, obtain the exhaust temperature change value for that valve control cycle. And determine the change in exhaust temperature. The changing trend is used to control the opening degree of the main electronic expansion valve and the auxiliary electronic expansion valve according to the changing trend;

[0112] If the duration is less than one valve adjustment cycle, the exhaust temperature is continuously acquired.

[0113] In one embodiment, the opening threshold of the auxiliary electronic expansion valve is... It is 450P.

[0114] The opening degree of the auxiliary electronic expansion valve is adjusted according to the exhaust temperature in the following way:

[0115] Controlling the opening degree of the auxiliary electronic expansion valve satisfy;

[0116]

[0117] In the formula: This indicates the current opening degree of the auxiliary electronic expansion valve. This indicates the opening degree of the auxiliary electronic expansion valve at the previous moment. This indicates the current exhaust temperature. Indicates the target exhaust temperature, α P-F α represents the exhaust proportional coefficient of the auxiliary electronic expansion valve. D-F This represents the differential coefficient of the exhaust gas from the auxiliary electronic expansion valve. This indicates the exhaust temperature at the previous moment.

[0118] The target exhaust temperature The temperature is 95℃.

[0119] The adjustment of the opening degree of the main electronic expansion valve and the auxiliary electronic expansion valve according to the changing trend is specifically as follows:

[0120] If the exhaust temperature changes If the value is greater than 1, it indicates an upward trend. The auxiliary electronic expansion valve is controlled to maintain its current opening, while the main electronic expansion valve is closed by 6P / T.

[0121] If the exhaust temperature changes If the value is less than or equal to 1 and greater than or equal to -1, in order to maintain the trend, the opening degree of the main electronic expansion valve and the opening degree of the auxiliary electronic expansion valve are controlled to maintain the current opening degree.

[0122] If the exhaust temperature changes If the value is less than -1, it indicates a downward trend; therefore, the opening of the auxiliary electronic expansion valve should be controlled accordingly. Adjustments are made to maintain the current opening degree of the main electronic expansion valve;

[0123] Among them, the change value of exhaust temperature The exhaust temperature during the current valve control cycle Average exhaust temperature compared to the previous valve control cycle T-1 The difference, where T is the valve control cycle.

[0124] This step is used to address the issue of high exhaust temperature in the generator set. To ensure normal operation, the auxiliary electronic expansion valve is prioritized for controlling the exhaust temperature, while the main electronic expansion valve is either set to a fixed opening or closed slightly to cooperate with the auxiliary electronic expansion valve in controlling the exhaust.

[0125] The S50 controls the auxiliary electronic expansion valve to its maximum opening and acquires the exhaust temperature after a first time interval t1. Calculate the change in exhaust temperature And based on the change in exhaust temperature Trends in change and exhaust temperature Adjustment of the opening degree of the main electronic expansion valve.

[0126] In one embodiment, the maximum opening degree of the auxiliary electronic expansion valve is 500P.

[0127] The first time period t1 is the valve control cycle T-5s.

[0128] The value based on exhaust temperature change Trends in change and exhaust temperature The adjustment of the opening degree of the main electronic expansion valve is specifically as follows:

[0129] If the exhaust temperature changes A value greater than 1 indicates an upward trend, and:

[0130] Such as exhaust temperature Less than the third exhaust temperature threshold The opening of the main electronic expansion valve is reduced to 6P / t1;

[0131] Such as exhaust temperature Greater than or equal to the third exhaust temperature threshold The opening of the main electronic expansion valve is reduced by 10P / t1.

[0132] If the exhaust temperature changes Less than or equal to 1 and greater than or equal to -1, in order to maintain the trend, and:

[0133] Such as exhaust temperature Less than the third exhaust temperature threshold The opening of the main electronic expansion valve is reduced to 6P / T;

[0134] Such as exhaust temperature Greater than or equal to the third exhaust temperature threshold The opening of the main electronic expansion valve is reduced by 10P / T.

[0135] If the exhaust temperature changes If the value is less than -1, it indicates a downward trend, so the main electronic expansion valve is controlled to close slightly at 6P / T.

[0136] Where T is the valve control cycle.

[0137] The third exhaust temperature threshold The temperature is 105℃.

[0138] This step is used to determine if the auxiliary electronic expansion valve is not drawing sufficient liquid, and to reduce the opening of the main electronic expansion valve based on the liquid drawing situation to ensure the exhaust superheat meets the requirements. If the auxiliary electronic expansion valve supplies sufficient liquid, the exhaust temperature will decrease; if the auxiliary electronic expansion valve reaches its maximum opening of 500P, but the exhaust temperature is still above 95℃, both parameters indicate insufficient liquid drawing by the auxiliary electronic expansion valve. Since the total flow rate of the main and auxiliary electronic expansion valves is constant, the opening of the main electronic expansion valve needs to be reduced to ensure the flow rate of the auxiliary electronic expansion valve, thus meeting the purpose of reducing exhaust temperature by drawing liquid from the auxiliary electronic expansion valve. Once a decrease in exhaust temperature is detected, the main electronic expansion valve maintains its opening, and the auxiliary electronic expansion valve resumes priority control of the exhaust temperature.

[0139] In steps S30 to S50 above, the opening degree of the main electronic expansion valve is adjusted between the maximum and minimum opening values ​​determined for the corresponding ambient temperature range and the corresponding outlet water temperature. The maximum and minimum opening values ​​are determined in the following manner:

[0140] SA1 obtains the current ambient temperature. Determine the ambient temperature at the current moment. Ambient temperature range:

[0141] If the ambient temperature First ring temperature range Ambient temperature greater than the first temperature threshold And less than or equal to the low ambient temperature mode start-up threshold Then proceed to step SA2;

[0142] If the ambient temperature Second ring temperature range Ambient temperature Greater than or equal to the second temperature threshold And less than or equal to the first temperature threshold Then proceed to step SA3.

[0143] In one embodiment, the first temperature threshold The second temperature threshold is -25℃. If the temperature is -35℃, then the first ambient temperature range is (-25℃, -15℃) and the second ambient temperature range is [-35℃, -25℃].

[0144] SA2 obtains the current outlet water temperature. Determine the water temperature Is it less than or equal to the outlet water temperature threshold?

[0145] If yes, that means the outlet water temperature Less than or equal to the outlet water temperature threshold The main electronic expansion valve is adjusted to its first opening reference value K1 at a first valve adjustment rate, and the maximum opening value K of the main electronic expansion valve is determined based on the first opening reference value K1. 1-max and minimum opening value K 1-min ;

[0146] If no, that is, the outlet water temperature greater than the outlet water temperature threshold The main electronic expansion valve is adjusted to the second opening reference value K2 at the first valve adjustment rate, and the maximum opening value K of the main electronic expansion valve is determined based on the second opening reference value K2. 2-max and minimum opening value K 2-min .

[0147] SA3 obtains the current outlet water temperature. Determine the water temperature Is it less than or equal to the outlet water temperature threshold?

[0148] If yes, that means the outlet water temperature Less than or equal to the outlet water temperature threshold The main electronic expansion valve is adjusted to the third opening reference value K3 at the first valve adjustment rate, and the maximum opening value K of the main electronic expansion valve is determined based on the third opening reference value K3. 3-max and minimum opening value K 3-min ;

[0149] If no, that is, the outlet water temperature greater than the outlet water temperature threshold The main electronic expansion valve is adjusted to the fourth opening reference value K4 at the first valve adjustment rate, and the maximum opening value K of the main electronic expansion valve is determined based on the fourth opening reference value K4. 4-max and minimum opening value K 4-min .

[0150] In one embodiment, the outlet water temperature threshold The temperature is 30℃.

[0151] The first regulating valve has a rate of 10P / 10s.

[0152] The first opening reference value K1 is 190P, and its corresponding maximum opening value K 1-max 190P+80P, minimum opening value K 1-min It is 190P-30P.

[0153] The second opening reference value K2 is 170P, and its corresponding maximum opening value K 2-max 170P+80P, minimum opening value K 2-min It is 170P-30P.

[0154] The third opening reference value K3 is 160P, and its corresponding maximum opening value K 3-max 160P+60P, minimum opening value K 3-min It is 160P-20P.

[0155] The fourth opening reference value K4 is 140P, and its corresponding maximum opening value K 4-max 140P+60P, minimum opening value K 4-min It is 140P-20P.

[0156] It should be noted that when starting up for the first time or re-entering the heating mode after each defrost, the main electronic expansion valve first enters the adjustment of the reference opening, and then adjusts based on the subsequent unit conditions according to the reference opening, ensuring that the adjustment of the main electronic expansion valve does not exceed the maximum and minimum opening corresponding to its reference opening.

[0157] At low ambient temperatures, the adjustment range of the main electronic expansion valve is limited according to different ambient and outlet water temperatures to prevent the valve opening from being too large or too small during adjustment. This overcomes the problems of incomplete refrigerant evaporation and liquid carryover in the return gas caused by excessively large opening of the main electronic expansion valve under low ambient temperature conditions, and the problem of insufficient cooling of the compressor motor due to insufficient opening of the main electronic expansion valve, leading to overheating of the compressor motor, lower evaporation pressure, increased return gas overheating, increased pressure ratio, and exacerbated exhaust temperature rise. Since the reference opening is determined through extensive experiments, it is a suitable opening for the current ambient and outlet water temperatures. It does not need to be closed too small or opened too large, thus avoiding incomplete evaporation and liquid carryover.

[0158] Compared with the prior art, the heat pump system with low ambient temperature control mode of the present invention has the following beneficial technical effects.

[0159] 1) When the unit exhaust temperature is low, the main electronic expansion valve controls the return gas superheat to ensure full utilization of the evaporator area and prevent liquid return; the auxiliary electronic expansion valve controls the economizer superheat to ensure full utilization of the economizer and sufficient subcooling of the main refrigerant to improve the evaporator's heat absorption capacity.

[0160] 2) When the unit's exhaust temperature is high, the main electronic expansion valve is adjusted to cooperate with the auxiliary electronic expansion valve to reduce the exhaust temperature and improve the unit's reliability by judging whether the flow of the auxiliary refrigerant controlled by the auxiliary electronic expansion valve is sufficient.

[0161] 3) Determining the adjustment range of the main electronic expansion valve according to different ambient and water temperatures can prevent the main electronic expansion valve from opening too large or too small during the adjustment process. This overcomes the problems of incomplete refrigerant evaporation and liquid carryover in the return gas caused by excessive opening of the main electronic expansion valve when the cooling capacity and evaporator evaporation are low at low ambient temperatures. It also overcomes the problems of insufficient cooling and overheating of the compressor motor caused by insufficient refrigerant circulation and insufficient refrigerant cooling the compressor motor when the main electronic expansion valve opening is too small at low ambient temperatures. Additionally, it addresses the problems of lower evaporation pressure, increased return gas overheating, increased pressure ratio, and increased exhaust temperature.

[0162] 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 and claims of this application 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” and “several” refer to two or more; “and / or” refers to and includes any or all possible combinations of one or more associated listed items; “first,” “second,” “third,” etc., are used only to distinguish and not to describe a particular order or sequence, nor should they be construed as indicating or implying relative importance. When the above description relates to drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. In the description of this application, those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0163] 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 with a low ambient temperature control mode, comprising a compressor, a four-way valve, a water-side heat exchanger, an economizer, a main electronic expansion valve, an auxiliary electronic expansion valve, an air-side heat exchanger, and a temperature detection module, connected sequentially via refrigerant circulation piping, and a controller electrically and / or communicatively connected to the main electronic expansion valve, the auxiliary electronic expansion valve, and the temperature detection module, wherein the economizer includes a main refrigerant flow path and an auxiliary refrigerant flow path, wherein... The main refrigerant flow path is connected to a water-side heat exchanger and a main electronic expansion valve at both ends, and the auxiliary refrigerant flow path is connected to the compressor intermediate pressure chamber and an auxiliary electronic expansion valve at both ends. The auxiliary electronic expansion valve is installed on the refrigerant pipeline connecting the main refrigerant flow path and the auxiliary refrigerant flow path. The system is characterized by the controller controlling the low ambient temperature of the heat pump system in the following manner: S20 Obtains the current exhaust temperature Determine the exhaust temperature at the current moment. Exhaust temperature range: If exhaust temperature In the first exhaust temperature range, i.e. < Execute step S30; If exhaust temperature In the second exhaust temperature range, i.e. ∈[ , ], proceed to step S40; If exhaust temperature In the third exhaust temperature range, i.e. > Execute step S50; in, The first exhaust temperature threshold, This is the second exhaust temperature threshold, and < ; S30 controls the opening of the main electronic expansion valve to be adjusted according to the return gas superheat, and the opening of the auxiliary electronic expansion valve to be adjusted according to the economizer superheat. S40 Obtain the current opening degree of the auxiliary electronic expansion valve Determine the opening degree of the auxiliary electronic expansion valve at the current moment. Is it less than the preset auxiliary electronic expansion valve opening control threshold? : If so, control the opening of the main electronic expansion valve. Maintain the current opening degree and adjust the opening degree of the auxiliary electronic expansion valve according to the exhaust temperature; If not, then further obtain the duration of this condition: If the duration is greater than or equal to one valve control cycle, obtain the exhaust temperature change value for that valve control cycle. And determine the change in exhaust temperature. The changing trend is used to control the opening degree of the main electronic expansion valve and the auxiliary electronic expansion valve according to the changing trend; If the duration is less than one valve control cycle, continuously obtain the exhaust temperature; S50 controls the auxiliary electronic expansion valve to its maximum opening, and obtains the exhaust temperature after a first time interval t1. Calculate the change in exhaust temperature. And based on the change in exhaust temperature Trends in change and exhaust temperature Adjustment of the opening degree of the main electronic expansion valve; The opening degree of the main electronic expansion in steps S30 to S50 should be between the maximum and minimum opening degree values ​​determined under the reference opening degree determined by the corresponding ambient temperature and outlet water temperature.

2. The heat pump system according to claim 1, characterized in that, The method for adjusting the opening degree of the main electronic expansion valve according to the return gas superheat in step S30 is as follows: When heating, obtain the current return gas temperature. Coil temperature Calculate the current superheat of the return gas. Based on the current superheat of the return gas The previous moment's return superheat Target return gas superheat The opening degree of the main electronic expansion valve is controlled to meet the following requirements: ,in , In the formula, This indicates the current opening degree of the main electronic expansion valve. This indicates the opening degree of the main electronic expansion valve at the previous moment. This indicates the superheat proportional coefficient of the main electronic expansion valve. This represents the differential coefficient of superheat of the main electronic expansion valve; During cooling, obtain the current return gas temperature. Throttling temperature Calculate the current superheat of the return gas. Based on the current superheat of the return gas The previous moment's return superheat Target return gas superheat The opening degree of the main electronic expansion valve is controlled to meet the following requirements: ,in .

3. The heat pump system according to claim 2, characterized in that, The method for adjusting the opening degree of the auxiliary electronic expansion valve in step S30 according to the superheat of the economizer is as follows: Get the current inlet temperature of the economizer outlet temperature Calculate the superheat at the current moment. Based on the current overheating level Overheating at the previous moment Target overheating The opening degree of the auxiliary electronic expansion valve is controlled to meet the following requirements: ,in , In the formula: This indicates the current opening degree of the auxiliary electronic expansion valve. This indicates the opening degree of the auxiliary electronic expansion valve at the previous moment. This indicates the superheat proportionality coefficient of the auxiliary electronic expansion valve. This represents the differential coefficient of superheat of the auxiliary electronic expansion valve.

4. The heat pump system according to any one of claims 1-3, characterized in that, In step S40, the opening degree of the auxiliary electronic expansion valve is adjusted according to the exhaust temperature as follows: Based on the current exhaust temperature Exhaust temperature at the previous moment Target exhaust temperature Controlling the opening degree of the auxiliary electronic expansion valve satisfy; In the formula: This indicates the current opening degree of the auxiliary electronic expansion valve. This indicates the opening degree of the auxiliary electronic expansion valve at the previous moment. This indicates the exhaust proportional coefficient of the auxiliary electronic expansion valve. This represents the differential coefficient of the exhaust gas from the auxiliary electronic expansion valve.

5. The heat pump system according to claim 4, characterized in that, The adjustment of the opening degree of the main electronic expansion valve and the auxiliary electronic expansion valve according to the changing trend in step S40 is specifically as follows: If the exhaust temperature changes If the value is greater than 1, it indicates an upward trend. The auxiliary electronic expansion valve is controlled to maintain its current opening, while the main electronic expansion valve is closed by 6P / T. If the exhaust temperature changes If the value is less than or equal to 1 and greater than or equal to -1, in order to maintain the trend, the opening degree of the main electronic expansion valve and the opening degree of the auxiliary electronic expansion valve are controlled to maintain the current opening degree. If the exhaust temperature changes If the value is less than -1, it indicates a downward trend; therefore, the opening of the auxiliary electronic expansion valve should be controlled accordingly. Adjustments are made to maintain the current opening degree of the main electronic expansion valve; Among them, the change value of exhaust temperature The exhaust temperature during the current valve control cycle Average exhaust temperature compared to the previous valve control cycle T-1 The difference, where T is the valve control cycle.

6. The heat pump system according to any one of claims 1, 2, 3, and 5, characterized in that, In step S50, the adjustment of the main electronic expansion valve opening based on the trend of exhaust temperature change and the exhaust temperature control is specifically as follows: If the exhaust temperature changes A value greater than 1 indicates an upward trend, and: Such as exhaust temperature Less than the third exhaust temperature threshold The opening of the main electronic expansion valve is reduced to 6P / t1. Such as exhaust temperature Greater than or equal to the third exhaust temperature threshold The opening of the main electronic expansion valve is reduced by 10P / t1. If the exhaust temperature changes Less than or equal to 1 and greater than or equal to -1, in order to maintain the trend, and: Such as exhaust temperature Less than the third exhaust temperature threshold The main electronic expansion valve opening is reduced to 6P / T. Such as exhaust temperature Greater than or equal to the third exhaust temperature threshold The main electronic expansion valve opening is reduced to 10P / T. If the exhaust temperature changes If the value is less than -1, it indicates a downward trend, so the main electronic expansion valve is controlled to close slightly at 6P / T. Where T is the valve control cycle.

7. The heat pump system according to claim 6, characterized in that, The first time period t1 is T-5s, where T is the valve control cycle.

8. The heat pump system according to claim 7, characterized in that, First exhaust temperature threshold The second exhaust temperature threshold is 95°C. The third exhaust temperature threshold is 100°C. The temperature is 105℃.

9. The heat pump system according to any one of claims 1, 2, 3, 5, 7, and 8, characterized in that, The maximum and minimum aperture values ​​of the main electron expansion are determined in the following manner: Get the current ambient temperature Determine the current ambient temperature Ambient temperature range: If the ambient temperature First ring temperature range ( , ]: When the outlet water temperature Less than or equal to the outlet water temperature threshold Based on the first opening reference value of the main electronic expansion valve =190P determines the maximum opening value of the main electronic expansion valve. =190P + 80P and minimum opening value =190P-30P; When the outlet water temperature greater than the outlet water temperature threshold Based on the second opening reference value of the main electronic expansion valve =170P determines the maximum opening value of the main electronic expansion valve. =170P + 80P and minimum opening value =170P-30P; If the ambient temperature Second ambient temperature range [ , ]: When the outlet water temperature Less than or equal to the outlet water temperature threshold Based on the third opening reference value of the main electronic expansion valve =160P determines the maximum opening value of the main electronic expansion valve. =160P + 60P and minimum opening value =160P-20P; When the outlet water temperature greater than the outlet water temperature threshold Based on the fourth opening reference value of the main electronic expansion valve =140P determines the maximum opening value of the main electronic expansion valve. =140P + 60P and minimum opening value =140P-20P; in, The first temperature threshold, This is the second temperature threshold, and < .

10. The heat pump system according to claim 9, characterized in that, It also includes step S10: Get the current ambient temperature : If the ambient temperature Greater than the low ambient temperature mode start-up threshold The main electronic expansion valve and auxiliary electronic expansion valve of the control unit are adjusted to adjust their opening degree according to the existing program; If the ambient temperature Less than or equal to the low ambient temperature mode start-up threshold And greater than or equal to the unit start-up threshold The control unit starts the low ambient temperature control mode and executes step S20; If the ambient temperature Less than the unit start-up threshold Control unit shutdown; Low ambient temperature mode start-up threshold The temperature is -15℃; the unit start-up threshold is... The temperature is -35℃.

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