Double-compressor control system

Abstract

The invention provides a double-compressor control system, which relates to the technical field of compressor control and comprises a start control module, a control module and a control module, the operation monitoring and regulating module is used for monitoring operation parameters, suction pressure, exhaust pressure, oil temperature, rotating speed, refrigerant temperature and refrigerant flow of the double-compressor system in real time; through reasonable starting control sequence and time interval setting, current impact during starting of the double compressors is effectively reduced, compressor motors and a power grid are protected, the service life of the compressors is prolonged, the reliability of system starting is improved, and by monitoring system operation parameters in real time and using an accurate control algorithm for regulation and control, the system starting reliability is improved. The running state of the compressor can be adjusted in time according to the actual working condition, the running efficiency of the system is improved, energy consumption is reduced, and meanwhile the stability and reliability of the refrigerating and heating effects of the system are guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of compressor control, and particularly to a dual-compressor control system. Background Art

[0002] In refrigeration, heating, and gas compression applications, the compressor, as a core component, plays a crucial role in the working effect of the entire system with its performance and operating stability. With the development of technology and the diversification of application requirements, the single-compressor system gradually shows limitations when dealing with complex working conditions and high-efficiency requirements. To overcome the deficiencies of the single-compressor system, the dual-compressor system emerges as the times require. By reasonably configuring two compressors, the dual-compressor system can flexibly adjust the operating mode under different working conditions, thereby improving the overall performance and energy efficiency of the system. When the load demand is low, only one compressor can be operated to reduce energy consumption. When the load demand is high, the two compressors work simultaneously to meet the system's requirements for refrigeration capacity or heating capacity.

[0003] In the existing dual-compressor control systems, on the one hand, the start control of the compressors is not reasonable enough, resulting in a large current impact during the start process, which not only affects the service life of the compressors but also may cause interference to the power grid. When the two compressors start simultaneously, the instantaneous current is too large, which easily damages the motor windings of the compressors. At the same time, it may also cause voltage fluctuations in the power grid, affecting the normal operation of other electrical equipment. On the other hand, during the operation of the compressors, there is a lack of real-time monitoring and precise regulation capabilities for changes in working conditions, and the operating parameters of the compressors cannot be adjusted in a timely manner according to actual needs, resulting in low system operating efficiency. When the ambient temperature or load changes, the compressors cannot make corresponding adjustments quickly, resulting in poor refrigeration or heating effects of the system, while the power consumption remains high. In addition, there are also deficiencies in the cooperative work control of the two compressors in the existing technology. The work coordination between the two compressors is not smooth enough, and it is easy to interfere with each other. During the oil return control process, it may cause one compressor to have too much oil return and the other compressor to have insufficient oil return, affecting the lubrication effect of the compressors. In the control of gas injection and enthalpy increase for the compressors, the gas injection volume cannot be accurately controlled, making it difficult for the operating performance of the compressors to reach the best state.

[0004] In summary, there are many problems in the existing dual-compressor control systems in terms of start control, operation regulation, and cooperative work, which cannot meet the growing application requirements of high efficiency, stability, and energy conservation. Therefore, the present invention provides a dual-compressor control system to solve the problems existing in the start control, operation regulation, and cooperative work of the dual-compressor control system in the prior art, and to achieve efficient and stable control of the dual compressors, improving the overall performance of the system. Summary of the Invention

[0005] To achieve the above object, the present invention provides a dual-compressor control system, including:

[0006] A start control module: used to control the start sequence and time interval of the two compressors to reduce the impact of starting current;

[0007] An operation monitoring and regulation module: real-time monitoring of the operation parameters of the dual-compressor system, including suction pressure, discharge pressure, oil temperature, rotational speed, refrigerant temperature, and refrigerant flow rate of the system;

[0008] An oil return balance control module: both the first compressor and the second compressor in the dual-compressor system are equipped with corresponding oil separators;

[0009] A gas injection and enthalpy increase control module: when the gas injection electronic expansion valve is opened, the controller gradually increases the opening degree of the gas injection electronic expansion valve in sequence;

[0010] An intelligent collaborative control module: coordinating the operation of the two compressors, operating in a coordinated manner, and comprehensively analyzing various operation parameters under different working conditions, refrigeration, heating, dehumidification modes, and different load conditions to reasonably allocate the working tasks of the two compressors.

[0011] In one example, the start control module receives a start command, controls the first compressor to start. When the start duration of the first compressor reaches a first predetermined duration, the operating frequency of the first frequency converter is obtained. The operating frequency of the first frequency converter is greater than the first frequency threshold, and when the start duration of the first compressor reaches a second predetermined duration, the second compressor is controlled to start. At this time, the load and current changes generated by its operation are stable, and the second compressor is started to avoid the instantaneous large current impact caused by the simultaneous start of the two compressors, protecting the compressor motor and the power grid.

[0012] In one example, the operation monitoring and regulation module real-time monitors the operation parameters of the dual-compressor system, and uses a control algorithm according to the real-time parameters to regulate the operation state of the compressor. When the system detects that the suction pressure is too low, it means that the refrigerant is insufficient, and the frequency converter is controlled to reduce the rotational speed of the compressor, reducing the amount of refrigerant compression to maintain the system pressure balance, avoiding failures of the compressor due to too low suction pressure, reducing energy consumption. When it is monitored that the discharge temperature is too high and the compressor load is too large, the system increases the rotational speed of the cooling fan and adjusts the refrigerant flow rate for heat dissipation, reducing the operating power of the compressor to ensure that the discharge temperature is within the normal range.

[0013] In one example, one end of the first controllable valve of the oil return balance control module is connected to the oil discharge end of the first oil separator corresponding to the first compressor, and the other end is connected to the suction end of the second compressor. One end of the second controllable valve is connected to the oil discharge end of the second oil separator corresponding to the second compressor, and the other end is connected to the suction end of the first compressor. When both the first compressor and the second compressor are operating, the current oil temperatures of the two compressors are obtained in real time.

[0014] In one example, when the current oil temperatures of the first compressor and the second compressor are both lower than the corresponding oil temperature thresholds, the current oil demand of the first compressor and the current oil demand of the second compressor are respectively determined based on the current oil temperature and the current operating frequency. The opening degrees of the first controllable valve and the second controllable valve are controlled according to these two oil demands to achieve balanced distribution of the compressor oil volume. If the current oil demand of the first compressor is greater than the current oil demand of the second compressor, the system appropriately increases the opening degree of the first controllable valve, and more oil flows from the first oil separator to the suction end of the second compressor. At the same time, the opening degree of the second controllable valve is appropriately reduced to reduce the oil volume flowing to the suction end of the first compressor, ensuring balanced oil return of the two compressors.

[0015] In one example, when the gas injection and enthalpy increase control module opens the gas injection electronic expansion valve, the controller increases the opening degree of the gas injection electronic expansion valve in sequence. The two-stage compressor is started and runs for a first preset time period. The controller controls the opening degree of the gas injection electronic expansion valve to be a first preset opening degree. When the opening degree of the gas injection electronic expansion valve is the first preset opening degree, it runs for a second preset time period, and the opening degree of the gas injection electronic expansion valve increases to a second preset opening degree. When the opening degree of the gas injection electronic expansion valve is the second preset opening degree, it runs for a third preset time period, and the gas injection electronic expansion valve is fully opened. When the gas injection electronic expansion valve is opened, the detection device collects the gas injection temperature and gas injection pressure of the two-stage compressor, and obtains the saturation temperature corresponding to the gas injection pressure. The difference between the gas injection temperature and the saturation temperature is used as the gas injection superheat degree of the two-stage compressor. Based on this gas injection superheat degree, if the gas injection superheat degree is greater than the preset superheat degree, the two-stage compressor has liquid carry-over in gas injection.

[0016] In one example, the gas injection electronic expansion valve reduces to a preset opening degree, where the preset opening degree is an opening degree preset based on the fully open degree of the gas injection electronic expansion valve, the gas injection superheat degree, and the preset superheat degree. When the two-stage compressor has no liquid carry-over in gas injection, and it is determined twice that the gas injection superheat degree is greater than the preset superheat degree, operations of reducing the current opening degree of the gas injection electronic expansion valve and maintaining the current opening degree of the gas injection electronic expansion valve are respectively executed, and an operation of increasing the current opening degree of the gas injection electronic expansion valve is executed.

[0017] In one example, the intelligent collaborative control module is responsible for coordinating the operation of two compressors. In the low-load refrigeration mode, a compressor with a smaller power is started to operate. As the load gradually increases and one compressor cannot meet the demand, the intelligent collaborative control module starts the other compressor according to the current operating state of the system, the suction pressure, the discharge pressure, and the indoor and outdoor temperature parameters, and adjusts the operating frequencies and working durations of the two compressors to make them work collaboratively.

[0018] In one example, in the heating mode, according to the outdoor ambient temperature, the indoor set temperature, and the heating load factor of the system, the intelligent control module coordinates the operation of the two compressors. In the dehumidification mode, according to the changes in the indoor humidity and temperature, the operation of the two compressors is controlled to adjust the refrigerant flow rate and the evaporation temperature.

[0019] The dual-compressor control system proposed by the present invention can bring the following beneficial effects:

[0020] 1. By setting a reasonable starting control sequence and time interval, the present invention effectively reduces the current impact during the startup of the dual compressors, protects the compressor motor and the power grid, extends the service life of the compressors, improves the reliability of system startup. By real-time monitoring of the system operating parameters and using precise control algorithms for regulation, the compressors can adjust their operating states in a timely manner according to the actual working conditions, improving the operating efficiency of the system, reducing energy consumption, and at the same time ensuring the stability and reliability of the refrigeration and heating effects of the system.

[0021] 2. Through a unique oil return balance control mechanism, the present invention accurately controls the oil return according to the oil temperature and operating frequency parameters of the compressors, ensuring the balanced oil return of the two compressors, improving the lubrication effect of the compressors, extending the service life of the compressors, and enhancing the stability of system operation. By gradually opening the gas injection electronic expansion valve and precise regulation based on the superheat of the gas injection, the phenomenon of liquid carry-over during gas injection into the compressor is effectively avoided, ensuring the stable operation of the compressor during the gas injection and enthalpy increase process, and improving the performance of the compressor and the energy efficiency of the system.

[0022] 3. Through the intelligent collaborative control module, the present invention enables the two compressors to operate efficiently and collaboratively according to different working conditions and load requirements, improving the overall operating efficiency and stability of the system, providing users with a more comfortable and energy-saving usage experience, and meeting diverse application requirements. Description of the Drawings

[0023] The drawings described herein are used to provide a further understanding of the present invention and form a part of the present invention. The illustrative embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0024] Figure 1Schematic diagram of the architecture of a dual-compressor control system according to the present invention. Detailed implementation manners

[0025] To more clearly and completely illustrate the technical solution of the present invention, the present invention will be further described below with reference to the accompanying drawings.

[0026] Please refer to Figure 1 , the present invention provides a dual-compressor control system, including:

[0027] Startup control module: used to control the startup sequence and time interval of two compressors to reduce the startup current impact;

[0028] Operation monitoring and regulation module: real-time monitoring of the operation parameters of the dual-compressor system, including suction pressure, discharge pressure, oil temperature, rotational speed, refrigerant temperature and refrigerant flow rate of the system;

[0029] Oil return balance control module: both the first compressor and the second compressor in the dual-compressor system are equipped with corresponding oil separators;

[0030] Gas injection and enthalpy increase control module: when the gas injection electronic expansion valve is opened, the controller gradually increases the opening degree of the gas injection electronic expansion valve according to the time sequence;

[0031] Intelligent collaborative control module: coordinates the work of two compressors, runs in collaboration, and comprehensively analyzes various operation parameters under different working conditions (refrigeration, heating, dehumidification modes) and different load conditions, and reasonably distributes the work tasks of two compressors.

[0032] After receiving the startup instruction, the startup control module first controls the first compressor to start. After starting, the system starts timing. When the startup duration of the first compressor reaches the first predetermined duration , obtain the operating frequency of the first frequency converter , if is greater than the first frequency threshold , and the startup duration of the first compressor further reaches the second predetermined duration , at this time, control the second compressor to start.

[0033] The operation monitoring and regulation module real-time monitors the operation parameters of the dual-compressor system, including suction pressure , discharge pressure , oil temperature , rotational speed , refrigerant temperature of the system and refrigerant flow rate , and regulates the operation state of the compressor by using a control algorithm according to the real-time monitored parameters.

[0034] When the system detects the suction pressure When it is too low, it is judged that the refrigerant is insufficient. At this time, the frequency converter is controlled to reduce the rotational speed of the compressor, reduce the amount of refrigerant compression, and maintain the system pressure balance. When is lower than the set suction pressure threshold , the frequency converter reduces the rotational speed of the compressor from to to reduce the amount of refrigerant compression, avoid failures of the compressor due to too low suction pressure, and at the same time reduce energy consumption.

[0035] When the monitored exhaust temperature is too high, it indicates that the compressor load is too large. The system will increase the rotational speed of the cooling fan, adjust the refrigerant flow rate for heat dissipation, reduce the operating power of the compressor, and ensure that the exhaust temperature is within the normal range. When it is higher than the set exhaust temperature threshold , the rotational speed of the cooling fan increases from to , and at the same time, the refrigerant flow rate is adjusted to reduce the exhaust temperature to within the normal range.

[0036] In the oil return balance control module, one end of the first controllable valve is connected to the oil discharge end of the first oil separator corresponding to the first compressor, and the other end is connected to the suction end of the second compressor; one end of the second controllable valve is connected to the oil discharge end of the second oil separator corresponding to the second compressor, and the other end is connected to the suction end of the first compressor.

[0037] When both the first compressor and the second compressor are running, the current oil temperatures of the two compressors are obtained in real time and . When and are both lower than the corresponding oil temperature thresholds , based on the current oil temperature and the current operating frequency , the current oil demand of the first compressor and the current oil demand of the second compressor are determined respectively.

[0038] According to and , the opening degrees of the first controllable valve and the second controllable valve are controlled. If , the system appropriately increases the opening degree of the first controllable valve to allow more oil to flow from the first oil separator to the suction end of the second compressor, and at the same time appropriately reduces the opening degree of the second controllable valve to reduce the amount of oil flowing to the suction end of the first compressor, ensuring the oil return balance of the two compressors.

[0039] When the air-increasing enthalpy control module opens the air-increasing electronic expansion valve, the controller increases the opening degree of the air-increasing electronic expansion valve in sequence, and the two-stage compressor starts and runs for the first preset time period After that, the controller controls the opening of the gas-infusing electronic expansion valve to be the first preset opening ; When the electronic expansion valve is opened Run the second preset time period After that, its opening increases to the second preset opening ; Run the third preset time period again Finally, all the gas-supply electronic expansion valves are opened.

[0040] After the air supply electronic expansion valve is opened, the detection device collects the air supply temperature of the two-stage compressor and gas pressure , get the air filling pressure The corresponding saturation temperature , the supply air temperature With saturation temperature The difference between .

[0041] like Greater than the preset superheat , it is judged that the air supply of the two-stage compressor is liquid-carrying. At this time, the air supply electronic expansion valve reduces the preset opening , the preset opening The opening is pre-set based on the full opening of the air supply electronic expansion valve. If the air supply superheat is judged twice Greater than the preset superheat , the operations of reducing the current opening of the gas-injecting electronic expansion valve and maintaining the current opening of the gas-injecting electronic expansion valve are respectively performed, and then the operation of increasing the current opening of the gas-injecting electronic expansion valve is performed.

[0042] The intelligent collaborative control module is responsible for coordinating the work of the two compressors. In low-load cooling mode, a smaller compressor is started. As the load gradually increases, when one compressor cannot meet the demand, the intelligent collaborative control module will start the operation according to the current system operation status, including the suction pressure. , Exhaust pressure , indoor and outdoor temperature parameters , , start the other compressor, and adjust the operating frequency and working time of the two compressors to make them work together.

[0043] In heating mode, according to the outdoor ambient temperature , Indoor set temperature As well as the heating load factor of the system, the coordinated operation of the two compressors is intelligently controlled. When the outdoor ambient temperature is low, the operating power of the two compressors is appropriately increased to meet the indoor heating needs.

[0044] In dehumidification mode, according to the indoor humidity and temperature According to the changes of [parameters] and temperature, control the operation of two compressors, adjust the refrigerant flow rate and evaporation temperature. When the indoor humidity is high, increase the operating power of the compressors, increase the refrigerant flow rate, lower the evaporation temperature, and improve the dehumidification effect.

[0045] In the air-conditioning system of a hotel, in the low-load refrigeration mode, first start the compressor with a smaller power. When the number of indoor occupants increases and the load increases, and it is detected that the suction pressure drops and the indoor temperature rises, start the other compressor, and adjust the operating frequency and working duration of the two compressors according to the real-time parameters. In the heating mode, if the outdoor temperature is , and the indoor set temperature is , the system will increase the operating power of the two compressors to ensure that the indoor temperature reaches the set value. In the dehumidification mode, when the indoor humidity reaches , increase the operating power of the compressors, adjust the refrigerant flow rate and evaporation temperature, and lower the indoor humidity.

[0046] In the dual-compressor control system of this embodiment, when the system receives a start signal, the start control module first controls the first compressor to start. A first preset duration is set. After the first compressor starts for 5 seconds, the system obtains the operating frequency of the first frequency converter. The first frequency threshold is set to 30 Hz. When the operating frequency of the first frequency converter is greater than 30 Hz and the start duration of the first compressor reaches the second preset duration of 10 seconds, the start control module controls the second compressor to start. In actual operation, through this start control method, the current impact caused by the simultaneous start of the two compressors is successfully avoided. During the start process, the current rises steadily without abnormal fluctuations, effectively protecting the compressor motor and the power grid. At the same time, the start time is also shortened, and the response speed of the system is improved.

[0047] In an industrial refrigeration system, the operation monitoring and regulation module monitors the operating parameters of the compressor in real time. When the system detects that the suction pressure is 0.2 MPa, which is lower than the normal range of 0.3 - 0.5 MPa, the operation monitoring and regulation module controls the frequency converter to reduce the speed of the compressor from 50 Hz to 30 Hz according to the preset algorithm. After running for a period of time, the suction pressure gradually rises to 0.35 MPa and stabilizes within the normal range. At the same time, when the system detects that the exhaust temperature reaches 100 °C, which is higher than the normal range of 80 - 95 °C, the operation monitoring and regulation module immediately controls the speed of the cooling fan to increase from 1000 revolutions per minute to 1500 revolutions per minute and adjusts the refrigerant flow rate to gradually reduce the exhaust temperature to 90 °C within 10 minutes and return to the normal level. Through such real-time monitoring and precise regulation, the system can maintain stable operation under different working conditions, with good refrigeration effect and effective control of energy consumption.

[0048] In a dual-compressor heat pump system, the oil return balance control module comes into play. During the operation of the first compressor and the second compressor, real-time oil temperature monitoring shows that the current oil temperature of the first compressor is 50°C and that of the second compressor is 48°C, both not exceeding the oil temperature threshold of 60°C. At this time, the system calculates the current oil demand of the first compressor to be 0.8 L / min and that of the second compressor to be 0.6 L / min based on the operating frequency of the compressors and the current oil temperature. The oil return balance control module controls the opening degree of the first controllable valve to 60% and that of the second controllable valve to 40% according to these two oil demands. After running for a period of time, the oil temperatures and oil levels of the two compressors are detected again, and it is found that the oil temperature is stable within a reasonable range and the oil levels of the two compressors are basically the same, indicating that the oil return balance control effect is good, effectively ensuring the lubrication and stable operation of the compressors.

[0049] In a two-stage compression refrigeration system, when the gas injection and enthalpy increase function needs to be turned on, the gas injection and enthalpy increase control module starts to work. The first preset time period is set to 3 minutes. After the two-stage compressor has been running for 3 minutes, the controller adjusts the opening degree of the gas injection electronic expansion valve to the first preset opening degree, 20% full opening. After running for the second preset time period of 2 minutes at this opening degree, the opening degree of the gas injection electronic expansion valve is increased to the second preset opening degree, 50% full opening. After running for the third preset time period of 2 minutes, the gas injection electronic expansion valve is fully opened. During the gas injection process, the system collects the gas injection temperature of 30°C and the gas injection pressure of 0.6 MPa through the detection device. After calculation, the saturation temperature corresponding to the gas injection pressure is 25°C, so the gas injection superheat is 5°C, not greater than the preset superheat of 6°C. It is judged that the gas injection is liquid-free. At this time, the current opening degree of the gas injection electronic expansion valve is kept unchanged. During subsequent operation, the system continuously monitors the gas injection superheat. When the gas injection superheat occasionally exceeds the preset superheat, the system timely adjusts the opening degree of the gas injection electronic expansion valve, ensuring the stable operation of the compressor during the gas injection and enthalpy increase process and improving the refrigeration efficiency of the system.

[0050] The intelligent collaborative control module reasonably controls the collaborative operation of the two compressors according to different working conditions and load demands. During the peak cooling period in summer days, when the indoor load is large, the intelligent collaborative control module starts the two compressors simultaneously and adjusts the operating frequencies of the two compressors according to the indoor temperature, humidity, and outdoor ambient temperature parameters, enabling them to work collaboratively to meet the cooling demand. When night falls and the indoor load decreases, the intelligent collaborative control module shuts down one compressor according to the real-time monitored parameters and only allows the other compressor to operate at a lower frequency to maintain a comfortable indoor environment. In the winter heating mode, according to the changes in the outdoor temperature and the indoor set temperature, the intelligent collaborative control module precisely controls the collaborative operation of the two compressors, minimizing energy consumption while ensuring the heating effect. Through intelligent collaborative control, the operating efficiency of this commercial air-conditioning system has been significantly improved, with energy consumption reduced by approximately 20%, saving a large amount of energy costs for users and at the same time improving the comfort of the indoor environment. The above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0051] Certainly, the present invention can also have many other implementation manners. Based on this implementation manner, other implementation manners obtained by ordinary technicians in the art without any creative work belong to the protection scope of the present invention.

Claims

1. A dual-compressor control system, characterized in that, Including: Startup control module: used to control the startup sequence and time interval of two compressors to reduce the startup current impact; Operation monitoring and regulation module: to monitor in real time the operation parameters of the dual-compressor system, including suction pressure, discharge pressure, oil temperature, rotational speed, refrigerant temperature and refrigerant flow rate of the system; Oil return balance control module: in the dual-compressor system, the first compressor and the second compressor are both equipped with corresponding oil separators; Gas injection and enthalpy increase control module: when the gas injection and enthalpy increase control module opens the gas injection electronic expansion valve, the controller gradually increases the opening degree of the gas injection electronic expansion valve according to the time sequence; Intelligent collaborative control module: coordinates the work of the two compressors to operate collaboratively, and under different working conditions such as refrigeration, heating, and dehumidification modes, as well as different load conditions, conducts comprehensive analysis of various operation parameters and reasonably distributes the work tasks of the two compressors.

2. The dual compressor control system according to claim 1, wherein, The startup control module receives a startup instruction, controls the first compressor to start. When the startup duration of the first compressor reaches the first preset duration, the operating frequency of the first frequency converter is obtained. The operating frequency of the first frequency converter is greater than the first frequency threshold, and when the startup duration of the first compressor reaches the second preset duration, the second compressor is controlled to start. At this time, the load and current changes generated by its operation are stable, and the second compressor is started to avoid the instantaneous large current impact caused by the simultaneous startup of the two compressors, protecting the compressor motor and the power grid.

3. A dual-compressor control system according to claim 1, characterized in that, The operation monitoring and regulation module monitors in real time the operation parameters of the dual-compressor system, and uses a control algorithm based on the real-time parameters to regulate the operation state of the compressor. When the system detects that the suction pressure is too low, it means that the refrigerant is insufficient, and the frequency converter is controlled to reduce the rotational speed of the compressor, reduce the amount of refrigerant compression, maintain the system pressure balance, avoid faults of the compressor due to too low suction pressure, and reduce energy consumption. When it is detected that the discharge temperature is too high and the compressor load is too large, the system increases the rotational speed of the cooling fan and adjusts the refrigerant flow rate for heat dissipation, reduces the operating power of the compressor, and ensures that the discharge temperature is within the normal range.

4. A dual-compressor control system according to claim 1, characterized in that, One end of the first controllable valve of the oil return balance control module is connected to the oil discharge end of the first oil separator corresponding to the first compressor, and the other end is connected to the suction end of the second compressor. One end of the second controllable valve is connected to the oil discharge end of the second oil separator corresponding to the second compressor, and the other end is connected to the suction end of the first compressor. When both the first compressor and the second compressor are operating, the current oil temperatures of the two compressors are obtained in real time.

5. The dual-compressor control system according to claim 4, characterized in that When the current oil temperatures of the first compressor and the second compressor are both lower than the corresponding oil temperature thresholds, the current oil demand of the first compressor and the current oil demand of the second compressor are respectively determined based on the current oil temperature and the current operating frequency. According to these two oil demands, the opening degrees of the first controllable valve and the second controllable valve are controlled to achieve the balanced distribution of the compressor oil. When the current oil demand of the first compressor is greater than the current oil demand of the second compressor, the system appropriately increases the opening degree of the first controllable valve, and more oil flows from the first oil separator to the suction end of the second compressor. At the same time, the opening degree of the second controllable valve is appropriately reduced to reduce the amount of oil flowing to the suction end of the first compressor, ensuring the balanced oil return of the two compressors.

6. The dual-compressor control system according to claim 1, wherein, When the air-inflation enthalpy-increasing control module turns on the air-inflation electronic expansion valve, the controller increases the opening of the air-inflation electronic expansion valve in a time sequence, the two-stage compressor starts and runs for a first preset time period, and the controller controls the opening of the air-inflation electronic expansion valve to be the first preset opening; the opening of the air-inflation electronic expansion valve is the first preset opening, and runs for a second preset time period, and the opening of the air-inflation electronic expansion valve increases to the second preset opening; The opening of the air-supply electronic expansion valve is the second preset opening, and the third preset time period is run. The air-supply electronic expansion valves are all opened, and the air-supply electronic expansion valves are turned on. The detection device collects the air-supply temperature and air-supply pressure of the two-stage compressor, and obtains the saturation temperature corresponding to the air-supply pressure. The difference between the air-supply temperature and the saturation temperature is used as the air-supply superheat of the two-stage compressor. Based on this air-supply superheat, if the air-supply superheat is greater than the preset superheat, the air of the two-stage compressor is liquid-containing.

7. A dual-compressor control system according to claim 6, characterized in that, The air-inflation electronic expansion valve reduces the preset opening, the preset opening is the opening pre-set based on the full opening of the air-inflation electronic expansion valve, the air-inflation superheat and the preset superheat, the air-inflation of the two-stage compressor is liquid-free, and it is judged twice that the air-inflation superheat is greater than the preset superheat, and the operations of reducing the current opening of the air-inflation electronic expansion valve and maintaining the current opening of the air-inflation electronic expansion valve are respectively executed, and the operation of increasing the current opening of the air-inflation electronic expansion valve is executed.

8. A dual-compressor control system according to claim 1, wherein, The intelligent collaborative control module is responsible for coordinating the work of the two compressors. In low-load cooling mode, a smaller-power compressor is started. When the load gradually increases and one compressor cannot meet the demand, the intelligent collaborative control module starts another compressor based on the current system operating status, suction pressure, exhaust pressure, and indoor and outdoor temperature parameters, and adjusts the operating frequency and working time of the two compressors to make them work together.

9. A dual-compressor control system according to claim 8, wherein, In the heating mode, the coordinated operation of the two compressors is intelligently controlled according to the outdoor ambient temperature, the indoor set temperature and the heating load factor of the system. In the dehumidification mode, the operation of the two compressors is controlled according to the changes in indoor humidity and temperature to adjust the refrigerant flow and evaporation temperature.

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