A heat pump system with low ambient temperature and high load control

Abstract

The present invention relates to a heat pump system with low ambient temperature and high load control, the system 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 and a pressure detection module, which are sequentially connected through a refrigerant circulation pipeline, and a controller electrically and / or communicatively connected to the compressor, the main electronic expansion valve, the auxiliary electronic expansion valve, the temperature detection module and the pressure detection module. The controller controls the frequency of the compressor and the opening of the auxiliary electronic expansion valve by monitoring the input current, exhaust temperature and exhaust superheat of the system, and reduces the system input current by closing the opening of the auxiliary electronic expansion valve, so that the system can achieve more efficient, more stable and more reliable operation of the unit at low temperature and high load under the dual protection of current control and exhaust control.

Description

Technical Field

[0001] The present invention relates to the field of heat pump system control, and in particular to a heat pump system with low ambient temperature and high load control. Background Art

[0002] A heat pump system is a highly efficient and environmentally friendly energy utilization technology. Its core operating principle is the reverse Carnot cycle. By consuming a small amount of electricity or other energy, it transfers heat energy from a low-temperature heat source to a high-temperature environment, achieving heating or cooling. Using minimal electrical energy, heat pump systems absorb low-temperature heat energy from the air, compress it into high-temperature heat energy through a compressor, and then transfer it to the location requiring heating or cooling. Highly favored by consumers and users, heat pump systems 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 advancement of heat pump technology, heat pump heating systems are increasingly being used in cold and extremely cold regions with relatively low ambient temperatures, requiring an outlet water temperature of 55°C or above to ensure adequate heating. However, most R410A or R32 heat pump heating systems in China are currently designed for a maximum outlet water temperature of 55°C. To ensure system reliability in heating applications with low ambient temperatures and high outlet water temperatures, a secondary refrigerant supply line is created using jet enthalpy injection technology. This secondary refrigerant, after throttling by an auxiliary electronic expansion valve, enters the economizer, where it undergoes heat exchange and evaporation with the main refrigerant flowing to the evaporator. The secondary refrigerant then enters the compressor's intermediate pressure chamber, where it mixes with the gas in the compressor's intermediate pressure chamber, thereby lowering the discharge temperature. Current control of the primary and secondary electronic expansion valves involves maintaining the current opening of the primary and secondary electronic expansion valves during rising discharge temperature and rapidly opening them during high water temperature operation.

[0004] During the exhaust temperature rising process, the above control method cannot determine whether the opening of the system main electronic expansion valve and the auxiliary electronic expansion valve is reasonable. The return air superheat may be too large, the economizer superheat may be too large, the heat exchange area of ​​the evaporator and the economizer may not be fully utilized, and the heating capacity is insufficient; the return air superheat may be too small, the economizer superheat may be too large, and the excessive refrigerant on the evaporation side may cause the compressor to run with liquid compression. At the same time, the economizer superheat is too large and the designed economizer function is lost. It is impossible to increase the heating amount and reduce the exhaust temperature, and the adaptability is poor; this control does not improve the auxiliary line liquid extraction capacity, the exhaust temperature is getting higher and higher, the whole machine input current or the compressor compressor phase current is also getting larger and larger, and it can only continuously reduce the frequency operation, which greatly reduces the heating capacity when running at a high outlet water temperature. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a heat pump system with low ambient temperature and high load control. The heat pump system controls the frequency of the compressor, the opening of the main electronic expansion valve and the auxiliary electronic expansion valve through the relationship between the system's input current and the preset current frequency reduction value and current frequency limit value to ensure the reliability of the unit when operating under low ambient temperature and high load conditions.

[0006] A heat pump system with low ambient temperature and high load control 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 and a pressure detection module connected in sequence through a refrigerant circulation pipeline, and a controller electrically and / or communicatively connected to the compressor, the main electronic expansion valve, the auxiliary electronic expansion valve, the temperature detection module and the pressure detection module. It is characterized in that the economizer includes a first refrigerant flow path and a second refrigerant flow path, wherein the first refrigerant flow path is connected to the main electronic expansion valve, and the second refrigerant flow path is connected to the auxiliary electronic expansion valve and then flows back to the economizer and then connected to the compressor medium-pressure chamber. The controller performs low ambient temperature and high load control of the heat pump system in the following manner:

[0007] Get the system's current input current

[0008] If the current input Greater than or equal to the preset current reduction value Then the compressor is controlled to run at reduced frequency and the auxiliary electronic expansion valve is opened to a smaller degree;

[0009] If the current input Less than the current frequency reduction value Then the stored input current is:

[0010] If the stored input current is less than the current reduction value The compressor frequency, main electronic expansion valve and auxiliary electronic expansion valve are PID controlled according to the current exhaust temperature and exhaust superheat;

[0011] If the stored input current includes a current reduction value greater than or equal to the current reduction value The input current at the current moment is further determined. and current frequency limit value Relationship: If the current input current Greater than or equal to the current frequency limit value The compressor frequency and the auxiliary electronic expansion valve opening remain unchanged; if the current input current Less than the current frequency limit value The compressor frequency, main electronic expansion valve and auxiliary electronic expansion valve are PID controlled according to the current exhaust temperature and exhaust superheat;

[0012] Among them, the current frequency reduction value >Current frequency limit value

[0013] Compared with the existing technology, the heat pump system with low ambient temperature and high load control of the present invention has the following beneficial technical effects: when the unit is operating at a high compression ratio and high load, the frequency of the compressor and the opening of the auxiliary electronic expansion valve are controlled by monitoring the input current, exhaust temperature and exhaust superheat of the system, so as to reduce the opening of the auxiliary electronic expansion valve to reduce the input current of the system, so that the system can achieve more efficient, stable and reliable operation of the unit at low temperature and high load under the dual protection of current control and exhaust control.

[0014] Furthermore, the current input current Less than the current frequency reduction value The specific control steps are as follows:

[0015] Ergodic stored input current

[0016] If the stored input current Includes current frequency reduction value greater than or equal to Input current Then compare the current input current K times the current frequency reduction value Is the relationship less than, where i∈(1, t-1), K<1:

[0017] If the current input Less than K times the current frequency reduction value Then the compressor frequency is controlled to remain unchanged, the auxiliary electronic expansion valve opening is unchanged, and the input current is further determined. Is it greater than or equal to the preset current frequency limit value? If yes, the compressor frequency and the auxiliary electronic expansion valve opening remain unchanged; if no, the compressor frequency, main electronic expansion valve and auxiliary electronic expansion valve are controlled according to the exhaust gas temperature and exhaust gas superheat;

[0018] If the current input Greater than or equal to K times the current frequency reduction value The compressor frequency is controlled to remain unchanged, and the auxiliary electronic expansion valve closes the first regulating valve opening at the first regulating valve rate, and continuously monitors the input current I in ;

[0019] If the stored input current Both are less than the current frequency reduction value The compressor frequency, main electronic expansion valve and auxiliary electronic expansion valve are PID controlled according to the current exhaust temperature and exhaust superheat.

[0020] Furthermore, the current input current Greater than or equal to the preset current reduction value The specific control steps are as follows:

[0021] The compressor is controlled to operate at a frequency reduction rate, and the auxiliary electronic expansion valve is closed at the first valve adjustment rate to reduce the first valve opening, and the input current at the next moment is further obtained.

[0022] If the input current Greater than or equal to the preset current shutdown value I off , then the compressor is controlled to stop;

[0023] If the input current Less than the preset current shutdown value I off , the input current I is continuously monitored in ;

[0024] Among them, the current shutdown value I off >Current frequency reduction value

[0025] Furthermore, the current input current Greater than or equal to the preset current reduction value The specific control steps are as follows:

[0026] Determine whether the compressor frequency reduction operation is triggered for the first time:

[0027] If yes, the compressor is controlled to operate at a lower frequency based on the current frequency.

[0028] If not, the compressor is controlled to run at a frequency reduction rate, and the auxiliary electronic expansion valve is closed at the first valve adjustment rate to reduce the first valve opening, and the input current at the next moment is further obtained.

[0029] If the input current Greater than or equal to the preset current shutdown value I off , then the compressor is controlled to stop;

[0030] If the input current Less than the preset current shutdown value I off , the input current I is continuously monitored in ;

[0031] Among them, the current shutdown value I off >Current frequency reduction value

[0032] Furthermore, the compressor frequency, the main electronic expansion valve, and the auxiliary electronic expansion valve are PID-controlled according to the current exhaust temperature and exhaust superheat, specifically including the following steps:

[0033] Get the current exhaust temperature of the compressor and determine the exhaust temperature range:

[0034] (1) If the exhaust gas temperature is within the first exhaust gas temperature range, the compressor is controlled to operate at the current ambient temperature frequency limit value, the main electronic expansion valve is PID-regulated according to the return gas superheat target value, and the auxiliary electronic expansion valve is PI-regulated according to the economizer superheat target value;

[0035] (2) If the exhaust gas temperature is within the second exhaust gas temperature range, the compressor is controlled to operate at the current ambient temperature frequency limit value, the main electronic expansion valve is PID-regulated according to the return gas superheat target value, and the auxiliary electronic expansion valve is PI-regulated according to the exhaust gas temperature target value;

[0036] (3) If the exhaust gas temperature is within the third exhaust gas temperature range, the compressor is controlled to operate at the current frequency, the main electronic expansion valve performs PID adjustment according to the return gas superheat target value, and the auxiliary electronic expansion valve opens the third regulating valve at the third regulating valve rate but does not exceed its maximum limit value;

[0037] (4) If the exhaust gas temperature is within the fourth exhaust gas temperature range, the compressor is controlled to operate at the current frequency, the main electronic expansion valve maintains the current opening, and the auxiliary electronic expansion valve is opened at the third valve regulating rate to increase the third valve regulating opening but not exceed its maximum limit value;

[0038] (5) If the exhaust temperature is within the fifth exhaust temperature range, the compressor is controlled to operate at a frequency reduction rate of 1 gear / 20s, the main electronic expansion valve is closed at the third valve adjustment rate to reduce the third valve opening, and the auxiliary electronic expansion valve is closed at the first valve adjustment rate to reduce the first valve opening, and the minimum value cannot be lower than the minimum limit value;

[0039] (6) If the exhaust gas temperature is within the sixth exhaust gas temperature range, the compressor is controlled to stop;

[0040] The first exhaust temperature range is less than the second exhaust temperature range, less than the third exhaust temperature range, less than the fourth exhaust temperature range, less than the fifth exhaust temperature range, and less than the sixth exhaust temperature range.

[0041] Furthermore, when the exhaust temperature is in the first exhaust temperature range, the specific control steps are as follows:

[0042] The compressor is controlled to operate at the current ambient temperature frequency limit value. The main electronic expansion valve performs PID adjustment based on the return air superheat target value, and the auxiliary electronic expansion valve performs PI adjustment based on the economizer superheat target value. The exhaust gas superheat is further obtained:

[0043] If the exhaust superheat is greater than or equal to 25°C, the exhaust superheat is continuously monitored;

[0044] If the exhaust superheat is less than 25°C and greater than or equal to 22°C, the auxiliary electronic expansion valve is controlled to perform PI adjustment based on the target superheat of the economizer;

[0045] If the exhaust superheat is less than 22°C, the current opening of the auxiliary electronic expansion valve is further obtained:

[0046] If the current opening of the auxiliary electronic expansion valve is greater than its initial opening, the auxiliary electronic expansion valve is controlled to close to its initial opening at the second valve adjustment rate and then maintained for 30 seconds, and the exhaust superheat is continuously monitored;

[0047] If the current opening of the auxiliary electronic expansion valve is less than or equal to its initial opening and greater than its minimum opening, the auxiliary electronic expansion valve is controlled to close to its minimum opening at the third valve regulating rate and hold for 30 seconds, and the exhaust superheat is continuously monitored. The third valve regulating rate is less than the second valve regulating rate.

[0048] If the current opening of the auxiliary electronic expansion valve is equal to its minimum opening, the current opening is maintained until the auxiliary electronic expansion valve reaches the closing condition and then closes.

[0049] By controlling the compressor frequency and the opening of the main and auxiliary electronic expansion valves based on the exhaust gas temperature and exhaust gas superheat, the system ensures that when the unit's exhaust gas temperature is low, the main electronic expansion valve is controlled based on the return gas superheat target value, fully utilizing the evaporator exchange while preventing liquid compression. The auxiliary electronic expansion valve prioritizes ensuring a reasonable exhaust gas superheat and then controls the economizer superheat target value, ensuring maximum utilization of the evaporator and economizer, preventing poor heat exchange due to low exhaust gas superheat, and improving the unit's heat exchange efficiency. When the unit's exhaust gas temperature is too high, the main electronic expansion valve controls the target return gas superheat, and the auxiliary electronic expansion valve controls the target exhaust gas temperature. When the current is too high, the auxiliary electronic expansion valve prioritizes the current as the control object, ensuring relatively stable exhaust gas temperature and current, and preventing current protection caused by opening the auxiliary electronic expansion valve to reduce the exhaust temperature. This significantly improves the unit's operating frequency under high compression ratios and high loads, increases heating capacity, and meets heating needs with higher outlet water temperatures.

[0050] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A schematic diagram of the system structure and refrigerant flow direction in heating mode according to an embodiment of the present invention;

[0052] Figure 2 FIG. 1 is a flow chart of a control method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0053] The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiments of the present invention.

[0054] In order to solve the technical problems that the existing control method of the electronic expansion valve of the heat pump system under low ambient temperature and high load conditions cannot determine whether the opening of the system main electronic expansion valve and the auxiliary electronic expansion valve is reasonable during the exhaust temperature rising process, resulting in excessive return air superheat, excessive economizer superheat, insufficient utilization of the heat exchange area of ​​the evaporator and the economizer, and insufficient heating capacity, or too little return air superheat, too much refrigerant on the evaporation side, and the compressor running with liquid compression; after research and debugging, the present invention proposes a heat pump system with low ambient temperature and high load control, the heat pump system has a low ambient temperature and high load control method, the control method sets the current frequency reduction value and the current frequency limit value, firstly, by monitoring the relationship between the system input current and the current frequency reduction value, according to the input current being greater than or equal to the current frequency reduction value, the pressure is controlled The compressor operates at reduced frequency and the auxiliary electronic expansion valve is closed. If the input current is less than the current frequency reduction value, the stored input current is traversed. If all stored input currents are less than the current frequency reduction value, the compressor frequency, the main electronic expansion valve, and the auxiliary electronic expansion valve are controlled using PID control based on the exhaust gas temperature and exhaust gas superheat. If the stored input current includes an input current greater than or equal to the current frequency reduction value, the relationship between the system input current and the current frequency limit value is further monitored. If the input current is greater than or equal to the current frequency limit value, the compressor frequency and the auxiliary electronic expansion valve opening are controlled to remain unchanged. If the input current is less than the current frequency limit value, the compressor frequency, the main electronic expansion valve, and the auxiliary electronic expansion valve are controlled using PID control based on the exhaust gas temperature and exhaust gas superheat. This control method monitors the input current, exhaust gas temperature, and exhaust gas superheat to achieve more efficient, stable, and reliable operation of the unit under low temperature and high load conditions.

[0055] In the specific implementation, please refer to Figure 1The heat pump system with low ambient temperature and high load control proposed by the present invention includes a compressor 10, a four-way valve 20, a water-side heat exchanger 30, an economizer 40, a liquid reservoir 50, a main electronic expansion valve 61, an auxiliary electronic expansion valve 62, an air-side heat exchanger 70, a gas-liquid separator 80, a temperature detection module 90, a pressure detection module 00, a controller (not shown), and other auxiliary pipes, all connected in a refrigerant pipeline loop. The controller is electrically or communicatively connected to the compressor 10, the main electronic expansion valve 61, the auxiliary electronic expansion valve 62, the temperature detection module 90, and the pressure detection module 00. During heating, the high-temperature and high-pressure refrigerant discharged from the exhaust port of the compressor 10 flows through the four-way valve 20 to the water-side heat exchanger 30 for heat exchange with the water medium and then flows to the economizer 40; after passing through the economizer 40, it is divided into two refrigerant flow paths, one of which flows through the liquid storage tank 50 to the main electronic expansion valve 61 for throttling and then flows to the air-side heat exchanger 70 for heat exchange with the air and then flows through the four-way valve 20 and the gas-liquid separator 80 to return to the return air port of the compressor 10, and the other refrigerant flow path flows through the auxiliary electronic expansion valve 62 for throttling and then flows back to the economizer 40 and then back to the medium-pressure chamber of the compressor 10.

[0056] The economizer 40 includes a first refrigerant flow path 41 and a second refrigerant flow path 42, wherein the first refrigerant flow path 41 is connected to the main electronic expansion valve 61 through the liquid storage tank 50, and the second refrigerant flow path 42 flows back to the economizer 40 through the auxiliary electronic expansion valve 62 and is connected to the medium-pressure chamber of the compressor 10.

[0057] The temperature detection module 90 includes a first temperature sensor 91 , a second temperature sensor 92 , a third temperature sensor 93 , a fourth temperature sensor 94 , a fifth temperature sensor 95 , an eighth temperature sensor 88 , and a ninth temperature sensor 89 .

[0058] The first temperature sensor 91 is provided at the exhaust end of the compressor 10 and is used to collect the actual exhaust temperature T of the compressor 10. PQ and the actual exhaust temperature T PQ Transmitted to the controller.

[0059] The second temperature sensor 92 is provided at the return air end of the compressor 10 and is used to collect the actual return air temperature T of the compressor 10. HQ and the actual return air temperature T HQ Transmitted to the controller.

[0060] The third temperature sensor 93 is provided at the inlet end of the connection between the auxiliary electronic expansion valve 62 and the economizer 40, and is used to collect the intake air temperature T JQ and the intake air temperature T JQ Transmitted to the controller.

[0061] The fourth temperature sensor 94 is provided at the outlet of the economizer 40 connected to the compressor 10 and is used to collect the outlet temperature T CQand the outlet temperature T CQ Transmitted to the controller.

[0062] The fifth temperature sensor 95 is used to collect the ambient temperature T H and the ambient temperature T H The fifth temperature sensor 95 can be arranged on the outside of the air-side heat exchanger 70 or on the casing of the heat pump system, which is not limited in this application.

[0063] The pressure detection module 00 includes a first pressure sensor 01 and a second pressure sensor 02. The first pressure sensor 01 is provided at the exhaust end of the compressor 10 and is used to collect the actual exhaust pressure F of the compressor 10. PQ and the actual exhaust pressure F PQ The second pressure sensor 02 is set at the return air end of the compressor 10, and is used to collect the actual return air pressure F of the compressor 10. HQ and the actual return air pressure F HQ Transmitted to the controller.

[0064] The controller receives the temperature signal collected by the above-mentioned temperature detection module 90, the pressure signal collected by the pressure detection module 00, the current of the whole machine, the compressor phase current, and the compressor frequency, and controls the opening of the main electronic expansion valve 61 and the auxiliary electronic expansion valve 62 and the frequency of the compressor according to the stored calculation and judgment program.

[0065] For details, please refer to Figure 2 The control method of the heat pump system with low ambient temperature and high load control of the present invention includes the following steps.

[0066] S10 obtains the current input current of the system

[0067] If the current input Greater than or equal to the current frequency reduction value Then the frequency reduction operation control specified in step S20 is executed;

[0068] If the current input Less than the current frequency reduction value Then execute step S30.

[0069] S20 controls the compressor to run at a frequency reduction rate, and the auxiliary electronic expansion valve closes the first regulating valve opening at the first regulating valve rate to further obtain the input current at the next moment.

[0070] If the input current Greater than or equal to the preset current shutdown value I off , then the compressor is controlled to stop;

[0071] If the input current Less than the preset current shutdown value I off , the input current I is continuously monitored in ;

[0072] Among them, the current shutdown value I off >Current frequency reduction value

[0073] In a specific implementation, the frequency reduction rate is 1 frequency / 20s, and the frequency is reduced to the minimum gear corresponding to the compressor, and an exemplary minimum gear is 30 Hz.

[0074] The first valve regulation rate of the auxiliary electronic expansion valve is 3P / 5s.

[0075] The first regulating valve opening of the auxiliary electronic expansion valve is 3P.

[0076] In one embodiment, before performing frequency reduction control on the compressor, it is further included to determine whether the triggering of the frequency reduction operation of the compressor is the first triggering, and step S20 is adjusted to S'20.

[0077] S'20 determines whether the compressor frequency reduction operation is triggered for the first time:

[0078] If yes, the compressor is controlled to operate at a lower frequency based on the current frequency.

[0079] If not, the compressor is controlled to run at a frequency reduction rate, and the auxiliary electronic expansion valve is closed at the first valve adjustment rate to reduce the first valve opening, and the input current at the next moment is further obtained.

[0080] If the input current Greater than or equal to the preset current shutdown value I off , the input current I is continuously monitored in ;

[0081] If the input current Less than the preset current shutdown value I off , then the compressor is controlled to stop;

[0082] Among them, the current shutdown value I off >Current frequency reduction value

[0083] In specific implementation, for the first time the compressor is triggered to reduce frequency, if the current frequency is the minimum gear frequency, it will be operated at the minimum gear frequency. If the current frequency is not the minimum gear frequency, it will be operated at a frequency one gear lower than the current frequency.

[0084] S30 traverses the stored input current

[0085] If the stored input current Includes current frequency reduction value greater than or equal to Input current Then judge the current input current Is it less than K times the current frequency reduction value? Where i∈(1, t-1) and K<1:

[0086] If yes, execute step S40;

[0087] If not, the compressor frequency is controlled to remain unchanged, the auxiliary electronic expansion valve is closed at the first regulating valve rate to reduce the first regulating valve opening, and the input current I is continuously monitored. in ;

[0088] If the stored input current Both are less than the current frequency reduction value The compressor frequency, main electronic expansion valve and auxiliary electronic expansion valve are PID controlled according to the current exhaust temperature and exhaust superheat.

[0089] In a specific implementation, the factor K∈(0.95, 0.98).

[0090] The method for performing PID control on the compressor frequency, the main electronic expansion valve, and the auxiliary electronic expansion valve according to the exhaust gas temperature and the exhaust gas superheat specifically includes the following steps.

[0091] SA1 obtains the current exhaust temperature of the compressor and determines the exhaust temperature range in which the exhaust temperature falls:

[0092] If the exhaust temperature is within the first exhaust temperature range, i.e. <90°C, execute SA2;

[0093] If the exhaust temperature is in the second exhaust temperature range, that is, ≥90°C and less than 93°C, execute SA3;

[0094] If the exhaust temperature is within the third exhaust temperature range, i.e., ≥93°C and less than 98°C, execute SA4;

[0095] If the exhaust temperature is in the fourth exhaust temperature range, that is, ≥98°C and less than 105°C, execute SA5;

[0096] If the exhaust temperature is in the fifth exhaust temperature range, that is, ≥105°C and less than 110°C, execute SA6;

[0097] If the exhaust temperature is in the sixth exhaust temperature range, i.e. ≥110°C, the compressor is controlled to shut down.

[0098] SA2 (<90℃) controls the compressor to operate at the current ambient temperature frequency limit value. The main electronic expansion valve performs PID adjustment according to the return air superheat target value, and the auxiliary electronic expansion valve performs PI adjustment according to the economizer superheat target value. The exhaust gas superheat is further obtained:

[0099] If the exhaust superheat is greater than or equal to 25°C, the exhaust superheat is continuously monitored;

[0100] If the exhaust superheat is less than 25°C and greater than or equal to 22°C, the auxiliary electronic expansion valve is controlled to perform PI adjustment based on the target superheat of the economizer;

[0101] If the exhaust superheat is less than 22°C, the current opening of the auxiliary electronic expansion valve is further obtained:

[0102] If the current opening of the auxiliary electronic expansion valve is greater than its initial opening, the auxiliary electronic expansion valve is controlled to close to its initial opening at the second valve adjustment rate and then maintained for 30 seconds, and the exhaust superheat is continuously monitored;

[0103] If the current opening of the auxiliary electronic expansion valve is less than or equal to its initial opening and greater than its minimum opening, the auxiliary electronic expansion valve is controlled to close to its minimum opening at the third valve regulating rate and hold for 30 seconds, and the exhaust superheat is continuously monitored. The third valve regulating rate is less than the second valve regulating rate.

[0104] If the current opening of the auxiliary electronic expansion valve is equal to its minimum opening, the current opening is maintained until the auxiliary electronic expansion valve reaches the closing condition and then closes.

[0105] In specific implementation, the current ambient temperature frequency limit value is a reasonable operating frequency determined by the current ambient temperature, unit capacity or compressor protection setting. This value is a preset value determined based on experimental data.

[0106] The second valve adjustment rate is 30P / 10s.

[0107] The third valve adjustment rate is 10P / 10s.

[0108] SA3 (≥90℃ and less than 93℃) controls the compressor to operate at the current ambient temperature frequency limit value. The main electronic expansion valve performs PID adjustment based on the return air superheat target value, and the auxiliary electronic expansion valve performs PI adjustment based on the exhaust gas temperature target value (90℃). After one valve adjustment cycle, the exhaust gas temperature is further obtained:

[0109] If the exhaust temperature is greater than or equal to 87°C, continue the above adjustment;

[0110] If the exhaust temperature is less than 87°C, execute SA2.

[0111] SA4 (≥93℃ and less than 98℃) controls the compressor to operate at the current frequency, the main electronic expansion valve performs PID adjustment according to the return air superheat target value, the auxiliary electronic expansion valve opens the third valve opening at the third valve adjustment rate but does not exceed its maximum limit value, and further obtains the exhaust gas temperature.

[0112] The opening of the third regulating valve is 10P.

[0113] SA5 (≥98℃ and less than 105℃) controls the compressor to run at the current frequency, the main electronic expansion valve maintains the current opening, the auxiliary electronic expansion valve opens the third regulating valve opening at the third regulating valve rate but does not exceed its maximum limit, and further obtains the exhaust temperature.

[0114] SA6 (≥105℃ and less than 110℃) controls the compressor to run at a frequency reduction rate of 1 gear / 20s, and the main electronic expansion valve closes the third regulating valve opening at the third regulating valve rate, and the auxiliary electronic expansion valve closes the first regulating valve opening at the first regulating valve rate. The minimum cannot be lower than the minimum limit value, and the exhaust temperature is further obtained. Among them, the compressor is reduced to the minimum gear of 30Hz.

[0115] Furthermore, when the auxiliary electronic expansion valve does not meet the opening condition, the auxiliary electronic expansion valve is closed, and the main electronic expansion valve is opened at the third valve regulating rate to increase the third valve regulating opening but not exceed its maximum limit value, and the exhaust gas temperature is further obtained.

[0116] S40 controls the compressor frequency to remain unchanged, the auxiliary electronic expansion valve opening to remain unchanged, and further determines the input current Is it greater than or equal to the preset current frequency limit value?

[0117] If yes, the input current Greater than or equal to the current frequency limit value Then keep the compressor frequency unchanged and the auxiliary electronic expansion valve opening unchanged;

[0118] If no, the input current Less than the current frequency limit value The compressor frequency, main electronic expansion valve and auxiliary electronic expansion valve are controlled according to the exhaust gas temperature and exhaust gas superheat;

[0119] Among them, the current frequency limit value <Current frequency reduction value

[0120] In one embodiment, the input current I in is the input current of the whole machine I tol-in , then the corresponding current frequency reduction value The frequency reduction value of the whole machine current The whole machine current frequency reduction value According to the variable frequency drive selection test setting, its range is generally set to: variable frequency drive input current frequency reduction value -1A; its corresponding current frequency limit value The current frequency limit value of the whole machine The whole machine current frequency limit value According to the variable frequency drive selection test settings, the range is generally set to: variable frequency drive input current limit value -1A.

[0121] In one embodiment, the input current I in is the compressor phase current I phase , then the corresponding current frequency reduction value The frequency reduction value of the compressor phase current The compressor phase current frequency reduction value According to the variable frequency drive selection test setting, its range is generally set to: variable frequency drive phase current frequency reduction value -1A; its corresponding current frequency limit value is the compressor phase current frequency limit value The phase current frequency limit value According to the variable frequency drive selection test settings, the range is generally set to: variable frequency drive phase current limit value -1A.

[0122] Compared with the prior art, the heat pump system with low ambient temperature and high load control of the present invention has the following beneficial technical effects.

[0123] 1) When the unit is running at a high compression ratio and high load, the system's input current, exhaust temperature, and exhaust superheat are monitored to jointly control the compressor frequency and the opening of the auxiliary electronic expansion valve. The opening of the auxiliary electronic expansion valve is closed to reduce the system input current. Under the dual protection of current control and exhaust control, the system can achieve more efficient, stable, and reliable operation at low temperatures and high loads.

[0124] 2) By controlling the frequency of the compressor and the opening of the main electronic expansion valve and the auxiliary electronic expansion valve through the exhaust gas temperature and the exhaust gas superheat, when the exhaust gas temperature of the unit is low, the main electronic expansion valve is controlled by the return gas superheat target value, so that the evaporator can be fully utilized under the premise of preventing liquid compression; the auxiliary electronic expansion valve gives priority to ensuring a reasonable exhaust gas superheat, and then takes the economizer superheat target value as the control object, ensuring the maximum utilization of the evaporator and the economizer, preventing poor heat exchange due to low exhaust gas superheat, and improving the heat exchange efficiency of the unit operation; when the exhaust gas temperature of the unit is too high, the main electronic expansion valve controls the target return gas superheat, and the auxiliary electronic expansion valve controls the target exhaust gas temperature. When the current is too large, the auxiliary electronic expansion valve gives priority to the current as the control object, ensuring that the exhaust temperature and current are relatively stable, and the current protection is not caused by opening the auxiliary electronic expansion valve due to lowering the exhaust temperature. The operating frequency of the unit under high compression ratio and high load is greatly improved, the heating capacity is increased, and the heating demand with higher outlet water temperature is met.

[0125] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the embodiments of the present application. The singular forms of "a", "said" and "the" used in the embodiments of the present application and the claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that, unless otherwise specified, "multiple" 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" and the like are only used to distinguish, and are not used to describe a specific order or sequence, nor can they be understood as indicating or implying relative importance. When the above description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. In the description of the present application, for those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0126] The above-described embodiments merely represent several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, and the present invention is intended to encompass such modifications and variations.

Claims

1. A heat pump system with low ambient temperature and high load control, 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 and a pressure detection module connected in sequence through a refrigerant circulation pipeline, and a controller electrically and / or communicatively connected to the compressor, the main electronic expansion valve, the auxiliary electronic expansion valve, the temperature detection module, and the pressure detection module, characterized in that: The economizer includes a first refrigerant flow path and a second refrigerant flow path, wherein the first refrigerant flow path is connected to the main electronic expansion valve, and the second refrigerant flow path is connected to the auxiliary electronic expansion valve, then flows back to the economizer and is connected to the compressor medium-pressure chamber. The controller performs low ambient temperature and high load control of the heat pump system in the following manner: Get the system's current input current If the current input Greater than or equal to the preset current reduction value Then the compressor is controlled to run at reduced frequency and the auxiliary electronic expansion valve is opened to a smaller degree; If the current input Less than the current reduction value Then the stored input current is: If the stored input current is less than the current reduction value The compressor frequency, main electronic expansion valve and auxiliary electronic expansion valve are PID controlled according to the current exhaust temperature and exhaust superheat; If the stored input current includes a current reduction value greater than or equal to the current reduction value The input current at the current moment is further determined. and current frequency limit value Relationship: If the current input current Greater than or equal to the current frequency limit value The compressor frequency and the auxiliary electronic expansion valve opening remain unchanged; if the current input current Less than the current frequency limit value The compressor frequency, main electronic expansion valve and auxiliary electronic expansion valve are PID controlled according to the current exhaust temperature and exhaust superheat; in, 2. The heat pump system according to claim 1, characterized in that Current input current Less than the current reduction value The specific control steps are as follows: Ergodic stored input current If the stored input current Includes current frequency reduction value greater than or equal to Input current Then compare the current input current K times the current frequency reduction value Is the relationship less than, where i∈(1, t-1), K<1: If the current input Less than K times the current frequency reduction value Then the compressor frequency is controlled to remain unchanged, the auxiliary electronic expansion valve opening is unchanged, and the input current is further determined. Is it greater than or equal to the preset current frequency limit value? If yes, the compressor frequency and the auxiliary electronic expansion valve opening remain unchanged; if no, the compressor frequency, main electronic expansion valve and auxiliary electronic expansion valve are controlled according to the exhaust gas temperature and exhaust gas superheat; If the current input Greater than or equal to K times the current frequency reduction value K* The compressor frequency is controlled to remain unchanged, and the auxiliary electronic expansion valve closes the first regulating valve opening at the first regulating valve rate, and continuously monitors the input current I in ; If the stored input current Both are less than the current frequency reduction value The compressor frequency, main electronic expansion valve and auxiliary electronic expansion valve are PID controlled according to the current exhaust temperature and exhaust superheat.

3. The heat pump system according to claim 2, characterized in that Current input current Greater than or equal to the preset current reduction value The specific control steps are as follows: The compressor is controlled to operate at a frequency reduction rate, and the auxiliary electronic expansion valve is closed at the first valve adjustment rate to reduce the first valve opening, and the input current at the next moment is further obtained. If the input current Greater than or equal to the preset current shutdown value I off , then the compressor is controlled to stop; If the input current Less than the preset current shutdown value I off , then continuously monitor the input current I in ; Among them, the current shutdown value I off >Current frequency reduction value 4. The heat pump system according to claim 2, characterized in that Current input current Greater than or equal to the preset current reduction value The specific control steps are as follows: Determine whether the compressor frequency reduction operation is triggered for the first time: If yes, the compressor is controlled to operate at a lower frequency based on the current frequency. If not, the compressor is controlled to run at a frequency reduction rate, and the auxiliary electronic expansion valve is closed at the first valve adjustment rate to reduce the first valve opening, and the input current at the next moment is further obtained. If the input current Greater than or equal to the preset current shutdown value I off , then the compressor is controlled to stop; If the input current Less than the preset current shutdown value I off , then continuously monitor the input current I in ; Among them, the current shutdown value I off >Current frequency reduction value 5. The heat pump system according to any one of claims 1 to 4, characterized in that: The compressor frequency, main electronic expansion valve, and auxiliary electronic expansion valve are PID controlled according to the current exhaust temperature and exhaust superheat, specifically including the following steps: Get the current exhaust temperature of the compressor and determine the exhaust temperature range: (1) If the exhaust gas temperature is within the first exhaust gas temperature range, the compressor is controlled to operate at the current ambient temperature frequency limit value, the main electronic expansion valve is PID-regulated according to the return gas superheat target value, and the auxiliary electronic expansion valve is PI-regulated according to the economizer superheat target value; (2) If the exhaust gas temperature is within the second exhaust gas temperature range, the compressor is controlled to operate at the current ambient temperature frequency limit value, the main electronic expansion valve is PID-regulated according to the return gas superheat target value, and the auxiliary electronic expansion valve is PI-regulated according to the exhaust gas temperature target value; (3) If the exhaust gas temperature is within the third exhaust gas temperature range, the compressor is controlled to operate at the current frequency, the main electronic expansion valve performs PID adjustment according to the return gas superheat target value, and the auxiliary electronic expansion valve opens the third regulating valve at the third regulating valve rate but does not exceed its maximum limit value; (4) If the exhaust gas temperature is within the fourth exhaust gas temperature range, the compressor is controlled to operate at the current frequency, the main electronic expansion valve maintains the current opening, and the auxiliary electronic expansion valve is opened at the third valve regulating rate to increase the third valve regulating opening but not exceed its maximum limit value; (5) If the exhaust temperature is within the fifth exhaust temperature range, the compressor is controlled to operate at a frequency reduction rate of 1 gear / 20s, the main electronic expansion valve is closed at the third valve adjustment rate to reduce the third valve opening, and the auxiliary electronic expansion valve is closed at the first valve adjustment rate to reduce the first valve opening, and the minimum value cannot be lower than the minimum limit value; (6) If the exhaust gas temperature is within the sixth exhaust gas temperature range, the compressor is controlled to stop; The first exhaust temperature range is less than the second exhaust temperature range, less than the third exhaust temperature range, less than the fourth exhaust temperature range, less than the fifth exhaust temperature range, and less than the sixth exhaust temperature range.

6. The heat pump system according to claim 5, characterized in that When the exhaust temperature is in the first exhaust temperature range, the specific control steps are as follows: The compressor is controlled to operate at the current ambient temperature frequency limit value. The main electronic expansion valve performs PID adjustment based on the return air superheat target value, and the auxiliary electronic expansion valve performs PI adjustment based on the economizer superheat target value. The exhaust gas superheat is further obtained: If the exhaust superheat is greater than or equal to 25°C, the exhaust superheat is continuously monitored; If the exhaust superheat is less than 25°C and greater than or equal to 22°C, the auxiliary electronic expansion valve is controlled to perform PI adjustment based on the target superheat of the economizer; If the exhaust superheat is less than 22°C, the current opening of the auxiliary electronic expansion valve is further obtained: If the current opening of the auxiliary electronic expansion valve is greater than its initial opening, the auxiliary electronic expansion valve is controlled to close to its initial opening at the second valve adjustment rate and then maintained for 30 seconds, and the exhaust superheat is continuously monitored; If the current opening of the auxiliary electronic expansion valve is less than or equal to its initial opening and greater than its minimum opening, the auxiliary electronic expansion valve is controlled to close to its minimum opening at the third valve regulating rate and hold for 30 seconds, and the exhaust superheat is continuously monitored. The third valve regulating rate is less than the second valve regulating rate. If the current opening of the auxiliary electronic expansion valve is equal to its minimum opening, the current opening is maintained until the auxiliary electronic expansion valve reaches the closing condition and then closes.

7. The heat pump system according to claim 6, characterized in that: The first exhaust temperature range is (,90°C); The second exhaust temperature range is [90°C, 93°C); The third exhaust temperature range is [93°C, 98°C); The fourth exhaust temperature range is [98°C, 105°C); The fifth exhaust temperature range is [105°C, 110°C); The sixth exhaust gas temperature range is [110°C,).

8. The heat pump system according to claim 2, characterized in that The value range of K is [0.95, 0.98].

9. The heat pump system according to claim 1, characterized in that The input current of the system is the whole machine input current, or the compressor phase current.

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