Control method for low-temperature startup of heat pump system and heat pump system

Abstract

The present invention belongs to the technical field of heat pumps and discloses a control method for low-temperature startup of a heat pump system and a heat pump system. The auxiliary system for low-temperature startup of the heat pump system comprises a preheating bypass circuit, a pressure differential bypass valve, an electromagnetic two-way valve and an injection nozzle. A preheating bypass circuit is provided between the compressor and the gas-liquid separator, so that during low-temperature startup, a portion of the high-temperature refrigerant is directly transported from the compressor to the gas-liquid separator, thereby heating the liquid refrigerant accumulated in the gas-liquid separator. In addition, an injection nozzle for injecting multiple streams of rotating refrigerant into the bottom of the gas-liquid separator is provided at the outlet end of the preheating bypass circuit, thereby not only increasing the contact area, but also significantly improving the heat transfer efficiency by forming turbulence, shortening the preheating time and improving the startup efficiency, but also improving the evaporation rate, reducing the probability of liquid hammer caused by liquid refrigerant directly entering the compressor, and improving the safety protection of the compressor.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pumps, and in particular to a control method for low-temperature startup of a heat pump system and a heat pump system. Background Art

[0002] A heat pump system uses a reverse Carnot cycle, powered by a small amount of electricity, to transfer low-temperature heat to high-temperature heat. Its core functions include efficient and energy-efficient heating, cooling, and hot water supply, and it is widely used in construction, industry, transportation, and other fields. The system primarily consists of core components such as the evaporator, compressor, condenser, and expansion valve.

[0003] When the heat pump system is started in a low-temperature environment, the refrigerant is likely to accumulate at the bottom of the gas-liquid separator. The core function of the gas-liquid separator is to prevent liquid refrigerant from entering the compressor. When starting at low temperatures, the evaporator's heat exchange efficiency is insufficient, resulting in incomplete evaporation of the refrigerant and a high proportion of liquid refrigerant. At this time, there is too much liquid refrigerant accumulated at the bottom of the gas-liquid separator, and the liquid may enter the compressor with the gas, causing liquid hammer and damage to the compressor. In addition, since the liquid refrigerant is not fully vaporized and directly enters the compressor, the compressor suction superheat is insufficient, affecting the heating performance of the heat pump, thereby greatly reducing the starting efficiency.

[0004] Therefore, there is an urgent need for a control method and auxiliary system for low-temperature startup of a heat pump system to solve the above problems. Summary of the Invention

[0005] The object of the present invention is to provide a control method for low-temperature startup of a heat pump system and a heat pump system, which have a short preheating time, high startup efficiency and high safety protection.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In one aspect, an auxiliary system for low-temperature startup of a heat pump system is provided. The auxiliary system for low-temperature startup of a heat pump system is used to preheat liquid refrigerant accumulated at the bottom of a gas-liquid separator in the heat pump system. The heat pump system also includes a compressor for supplying refrigerant. The auxiliary system for low-temperature startup of a heat pump system includes:

[0008] a preheating bypass circuit, the preheating bypass circuit comprising an inlet and an outlet, the inlet being connected to the outlet of the compressor, and the outlet being connected to the bottom of the gas-liquid separator;

[0009] A pressure differential bypass valve, the pressure differential bypass valve being arranged on the preheating bypass circuit;

[0010] an electromagnetic two-way valve, the electromagnetic two-way valve being arranged between the pressure differential bypass valve and the gas-liquid separator;

[0011] An injection nozzle is connected to the outlet end of the preheating bypass circuit, and is used to inject multiple streams of rotating refrigerant into the bottom of the gas-liquid separator.

[0012] Optionally, a filter is provided at the connection between the injection nozzle and the outlet end.

[0013] Optionally, the auxiliary system for low-temperature startup of the heat pump system further includes a one-way valve, which is arranged between the injection nozzle and the electromagnetic two-way valve.

[0014] Optionally, the auxiliary system for low-temperature startup of the heat pump system further includes a capillary tube, which is arranged between the pressure differential bypass valve and the electromagnetic two-way valve.

[0015] In another aspect, a control method for low-temperature startup of a heat pump system is provided. The control method for low-temperature startup of a heat pump system is used to control the auxiliary system for low-temperature startup of a heat pump system as described in any of the above items. The control method for low-temperature startup of a heat pump system comprises the following steps:

[0016] S1, starting the heat pump system in low power mode;

[0017] S2. Adjust the opening of the pressure differential bypass valve to 50%;

[0018] S3, operating the electromagnetic two-way valve in an intermittent pulse mode to inject the refrigerant into the bottom of the gas-liquid separator for a first time t1;

[0019] S4, after the first time ends, operating the electromagnetic two-way valve in a normally open mode;

[0020] S5. The heat pump system further includes a temperature sensor, which is used to detect the temperature value T of the gas-liquid separator. 气分 , when T is satisfied 气分 When the temperature is ≥25°C, the electromagnetic two-way valve is switched back to the intermittent pulse mode and maintained for a second time t2;

[0021] S6. When the second time ends, the preheating bypass loop is closed, the low-temperature mode is exited, and the heat pump system starts a normal heating cycle.

[0022] Optionally, the heat pump system further comprises a pressure sensor, which is used to detect the pressure value P of the gas-liquid separator. 气分 , according to the formula ; Dynamically adjust the opening of the pressure differential bypass valve, where:

[0023] Q 旁通 is the opening of the pressure differential bypass valve;

[0024] K is the system constant, and its value range satisfies 0.8≤K≤1.2;

[0025] T 环境 is the temperature of the current environment;

[0026] T 基准 is the set ambient temperature reference value, and satisfies T 基准 =-35℃.

[0027] Optionally, in step S3, the intermittent pulse mode is specifically to open the electromagnetic two-way valve for 2 seconds and close the electromagnetic two-way valve for 1 second.

[0028] Optionally, in step S1, the following steps are further included:

[0029] S11, turning on the compressor and running it in a low frequency mode of 10 Hz;

[0030] S12. The heat pump system includes an evaporator, a condenser, and an electronic expansion valve connected between the evaporator and the condenser. The opening of the electronic expansion valve is adjusted to 70%.

[0031] Optionally, in step S3, the first time t1 satisfies 2min≤t1≤3min.

[0032] Optionally, in step S5, the second time t2 satisfies t2=30s.

[0033] Beneficial effects of the present invention:

[0034] The present invention provides an auxiliary system for low-temperature starting of a heat pump system. The auxiliary system for low-temperature starting of a heat pump system is provided with a preheating bypass circuit having a pressure difference bypass valve and an electromagnetic two-way valve between the compressor and the gas-liquid separator, so that during low-temperature starting, a portion of the high-temperature refrigerant is directly transported from the compressor to the gas-liquid separator, thereby heating the liquid refrigerant accumulated in the gas-liquid separator. In addition, an injection nozzle for injecting multiple streams of rotating refrigerant into the bottom of the gas-liquid separator is provided at the outlet end of the preheating bypass circuit, thereby not only increasing the contact area, but also significantly improving the heat transfer efficiency by forming turbulence, shortening the preheating time and improving the starting efficiency, and improving the evaporation rate, reducing the probability of liquid hammer caused by liquid refrigerant directly entering the compressor, and improving the safety protection of the compressor.

[0035] The present invention also provides a control method for controlling the above-mentioned auxiliary system for low-temperature startup of the heat pump system, which controls the electromagnetic two-way valve to inject high-temperature refrigerant through an intermittent pulse mode, so that during injection, the shock wave is used to destroy the surface tension of the liquid refrigerant accumulated at the bottom of the gas-liquid separator, thereby increasing the contact area between the high-temperature refrigerant and the liquid refrigerant accumulated at the bottom of the gas-liquid separator, accelerating the increase in the temperature of the liquid refrigerant accumulated at the bottom of the gas-liquid separator, thereby further shortening the preheating time and improving the startup efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of a heat pump system provided by the present invention and applied to an auxiliary system for low-temperature startup of a heat pump system;

[0037] Figure 2 This is a schematic diagram of the placement of the injection nozzle in the gas-liquid separator in the auxiliary system for low-temperature startup of a heat pump system provided by the present invention;

[0038] Figure 3 It is a flow chart of the steps of the control method for low-temperature startup of a heat pump system provided by the present invention.

[0039] In the picture:

[0040] 100, compressor; 200, gas-liquid separator; 300, temperature sensor; 400, pressure sensor; 500, evaporator; 600, condenser; 700, electronic expansion valve; 800, liquid receiver; 900, economizer;

[0041] 1. Preheating bypass circuit;

[0042] 2. Differential pressure bypass valve;

[0043] 3. Solenoid two-way valve;

[0044] 4. Injection nozzle;

[0045] 5. Filter element;

[0046] 6. One-way valve. DETAILED DESCRIPTION

[0047] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0048] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0049] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0050] In the description of this embodiment, the terms "upper," "lower," "right," and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meanings.

[0051] Due to insufficient heat exchange efficiency of the evaporator during low-temperature startup, the refrigerant evaporates incompletely and the proportion of liquid refrigerant is high. At this time, there is too much liquid refrigerant accumulated at the bottom of the gas-liquid separator. The liquid may enter the compressor along with the gas, causing liquid hammer and damage to the compressor. In addition, since the liquid refrigerant is not fully vaporized and directly enters the compressor, the compressor suction superheat is insufficient, affecting the heating performance of the heat pump, thereby greatly reducing the startup efficiency.

[0052] Therefore, in order to shorten the preheating time, improve the starting efficiency, and improve the safety protection performance, this embodiment provides an auxiliary system for low-temperature starting of the heat pump system. The auxiliary system for low-temperature starting of the heat pump system is used to preheat the liquid refrigerant accumulated at the bottom of the gas-liquid separator in the heat pump system. The heat pump system also includes a compressor for supplying refrigerant.

[0053] like Figures 1 to 2As shown, the auxiliary system for low-temperature startup of the heat pump system includes a preheating bypass circuit 1, a pressure differential bypass valve 2, an electromagnetic two-way valve 3 and an injection nozzle 4. The preheating bypass circuit 1 includes an inlet end and an outlet end. The inlet end is connected to the outlet of the compressor 100, and the outlet end is connected to the bottom of the gas-liquid separator 200. The pressure differential bypass valve 2 is arranged on the preheating bypass circuit 1, and the electromagnetic two-way valve 3 is arranged between the pressure differential bypass valve 2 and the gas-liquid separator 200. The injection nozzle 4 is connected to the outlet end of the preheating bypass circuit 1. The injection nozzle 4 is used to inject multiple rotating refrigerants into the bottom of the gas-liquid separator 200.

[0054] The auxiliary system for low-temperature startup of the heat pump system is configured by arranging a preheating bypass circuit 1 having a pressure differential bypass valve 2 and an electromagnetic two-way valve 3 between the compressor 100 and the gas-liquid separator 200, so that during low-temperature startup, a portion of the high-temperature refrigerant is directly transported from the compressor 100 to the gas-liquid separator 200, thereby heating the liquid refrigerant accumulated in the gas-liquid separator 200, and arranging an injection nozzle 4 at the outlet end of the preheating bypass circuit 1 for injecting multiple streams of rotating refrigerant into the bottom of the gas-liquid separator 200, thereby not only increasing the contact area but also significantly improving the heat transfer efficiency by forming turbulence, shortening the preheating time and improving the startup efficiency, and also improving the evaporation rate, reducing the probability of liquid hammer caused by liquid refrigerant directly entering the compressor 100, and improving the safety protection of the compressor 100.

[0055] In this embodiment, the injection nozzle 4 is designed based on a self-feeding nozzle, and is provided with a honeycomb porous ceramic layer, which makes it easier to divide the refrigerant into multiple fine streams, thereby increasing the contact area with the liquid refrigerant accumulated at the bottom of the gas-liquid separator 200, wherein the porosity of the honeycomb porous ceramic layer is 30% to 40%, and its pore size is 1mm to 2mm. The self-feeding nozzle is a nozzle with a special structure. Its main feature is that a spiral channel and a water flow rotating part are provided inside the nozzle, so that the sprayed water jet is a rotating water jet, which has the advantages of strong diffusion ability and large impact area. Therefore, the injection nozzle 4 designed based on the self-feeding nozzle, when injecting the refrigerant, makes the refrigerant have a certain rotational force, thereby forming turbulence, which significantly improves the heat transfer efficiency. Since the self-feeding nozzle is a conventional solution in the prior art, it will not be described in detail.

[0056] Optionally, a filter 5 is provided at the junction of the injection nozzle 4 and the outlet. This arrangement intercepts impurities in the refrigerant. In this embodiment, the filter 5 is a double-layer stainless steel filter with a thickness ranging from 50 μm to 100 μm.

[0057] Optionally, the auxiliary system for low-temperature startup of the heat pump system further includes a one-way valve 6, which is disposed between the injection nozzle 4 and the electromagnetic two-way valve 3. By disposing the one-way valve 6 between the electromagnetic two-way valve 3 and the injection nozzle 4, the high-temperature refrigerant can only flow through the compressor 100 to the gas-liquid separator 200, thereby preventing liquid refrigerant accumulated in the gas-liquid separator 200 from flowing back into the compressor 100, causing liquid hammer and damaging the compressor 100.

[0058] Optionally, the auxiliary system for low-temperature startup of the heat pump system also includes a capillary tube, which is disposed between the pressure differential bypass valve 2 and the electromagnetic two-way valve 3. By placing the capillary tube between the pressure differential bypass valve 2 and the electromagnetic two-way valve 3, the refrigerant flow and pressure are regulated to ensure stable operation of the system. In this embodiment, the inner diameter of the capillary tube is 1.0 mm.

[0059] In this embodiment, if Figures 1 to 3 As shown, a control method for low-temperature startup of a heat pump system is also provided. The control method for low-temperature startup of a heat pump system is used to control the auxiliary system for low-temperature startup of the heat pump system. The control method for low-temperature startup of a heat pump system comprises the following steps:

[0060] S1, start the heat pump system in low power mode;

[0061] S2, adjust the opening of the differential pressure bypass valve 2 to 50%;

[0062] S3, operating the electromagnetic two-way valve 3 in an intermittent pulse mode to inject the refrigerant into the bottom of the gas-liquid separator 200 for a first time t1;

[0063] S4, after the first time is over, operate the electromagnetic two-way valve 3 in the normally open mode;

[0064] S5. The heat pump system further includes a temperature sensor 300, which is used to detect the temperature value T of the gas-liquid separator 200. 气分 , when T is satisfied 气分 When the temperature is ≥25°C, the electromagnetic two-way valve 3 is switched back to the intermittent pulse mode and maintained for the second time t2;

[0065] S6. When the second time ends, the preheating bypass circuit 1 is closed, the low temperature mode is exited, and the heat pump system starts a normal heating cycle.

[0066] The electromagnetic two-way valve 3 is controlled by an intermittent pulse mode to inject high-temperature refrigerant, so that the surface tension of the liquid refrigerant accumulated at the bottom of the gas-liquid separator 200 is destroyed by the shock wave during injection, thereby increasing the contact area between the high-temperature refrigerant and the liquid refrigerant accumulated at the bottom of the gas-liquid separator 200, accelerating the increase in the temperature of the liquid refrigerant accumulated at the bottom of the gas-liquid separator 200, thereby further shortening the preheating time and improving the startup efficiency.

[0067] In this embodiment, in step S3, the electromagnetic two-way valve 3 operates in the pulse mode for the first time, in step S4, the electromagnetic two-way valve 3 is in the normally open mode, and in step S5, the electromagnetic two-way valve 3 switches back to the pulse mode and continues for the second time. The main reason is that, in the initial stage, it is necessary to use the shock wave formed by the pulse mode to destroy the surface tension of the liquid refrigerant accumulated at the bottom of the gas-liquid separator 200, so that the high-temperature refrigerant and the liquid refrigerant accumulated at the bottom of the gas-liquid separator 200 are quickly mixed to increase the temperature. After the first time, the initial temperature increase of the liquid refrigerant is achieved. At this time, there is no need to accelerate the temperature increase by forming a shock wave. Therefore, the pulse mode is switched to the normally open mode, and the liquid refrigerant accumulated at the bottom of the gas-liquid separator 200 is continuously heated by continuously inputting high-temperature refrigerant. As the temperature gradually increases, when the temperature meets T 气分 When the temperature is ≥25℃, the requirements for normal circulation operation of the heat pump system are met and there is no need to increase the temperature. At this time, the electromagnetic two-way valve 3 is switched back to the pulse mode. The pulse mode is mainly used to intermittently cut off the refrigerant flow, so that the total amount of refrigerant entering the gas-liquid separator 200 per unit time is reduced, thereby reducing the heat input rate, maintaining the temperature, and maintaining it for a second time. After determining that the temperature is in a stable state, the low-temperature mode can be exited and the normal working mode of the heat pump system can be performed.

[0068] Optionally, the heat pump system further includes a pressure sensor 400, which is used to detect the pressure value P of the gas-liquid separator 200. 气分 , according to the formula ; Dynamically adjust the opening of the pressure differential bypass valve 2, where:

[0069] Q 旁通 is the opening of the differential pressure bypass valve 2;

[0070] K is the system constant, and its value range satisfies 0.8≤K≤1.2;

[0071] T 环境 is the temperature of the current environment;

[0072] T 基准 is the set ambient temperature reference value, and satisfies T 基准 =-35℃.

[0073] By detecting the pressure of the gas-liquid separator 200 and using the detected pressure value P 气分 , according to the formula , to dynamically adjust the opening of the pressure differential bypass valve 2, thereby performing pressure protection on the gas-liquid separator 200 to avoid excessive pressure values and damage to the gas-liquid separator 200.

[0074] It should be noted that when Q 旁通 When ≥1, the default pressure differential bypass valve 2 is fully open.

[0075] Optionally, in step S3, the intermittent pulse mode is specifically to open the electromagnetic two-way valve for 2 seconds and close it for 1 second. The 2-second opening allows refrigerant injection, and the 1-second closing cuts off the flow by interrupting the flow, thereby causing the high-temperature refrigerant to form a "pulsed" transport mode, forming a shock wave, destroying the surface tension of the liquid refrigerant accumulated at the bottom of the gas-liquid separator 200, thereby improving heat transfer efficiency. In addition, the 2-second opening and 1-second closing cycle ensures that the high-temperature refrigerant is injected at a high frequency, thereby ensuring a shock effect.

[0076] Optionally, in step S1, the following steps are further included:

[0077] S11, turning on the compressor 100 and running it in a low frequency mode of 10 Hz;

[0078] S12. The heat pump system includes an evaporator 500, a condenser 600, and an electronic expansion valve 700 connected between the evaporator 500 and the condenser 600. The opening of the electronic expansion valve 700 is adjusted to 70%.

[0079] By starting the compressor 100 at a low frequency of 10 Hz at low temperature, the initial load of the compressor 100 is reduced, and overload or overheating of the compressor 100 caused by a high compression ratio in a low temperature environment is avoided, thereby extending the life of the equipment. In addition, by opening the electronic expansion valve 700 at an opening of 70%, on the one hand, it is avoided that the evaporation pressure is too low at low temperature, resulting in insufficient heat absorption of the evaporator 500 or liquid refrigerant enters the compressor 100, causing liquid hammer and damage to the compressor 100. On the other hand, by moderate throttling, the superheat of the refrigerant in the evaporator 500 is increased, ensuring sufficient evaporation and heat absorption, thereby enhancing the heat exchange effect in a low temperature environment.

[0080] In this embodiment, the heat pump system further includes a liquid reservoir 800 and an economizer 900. The liquid reservoir 800 is connected between the economizer 900 and the evaporator 500, and the economizer 900 is connected between the liquid reservoir 800 and the condenser 600. The liquid reservoir 800 is provided to store excess liquid in the refrigerant after condensation in the condenser 600, thereby preventing liquid hammer and damage to the compressor 100. The economizer 900 is provided in the heat pump circuit. The economizer 900 includes two circuits that divide the refrigerant into two paths. One of the circuits is provided with an electronic expansion valve 700. The refrigerant absorbs heat through self-throttling and evaporation, thereby cooling the refrigerant in the other circuit. The cooled refrigerant in the other circuit enters the evaporator 500, improving the heat absorption efficiency of the evaporator 500. The refrigerant that has undergone self-throttling and evaporation through the electronic expansion valve 700 flows directly back into the compressor 100, replenishing the compressor 100.

[0081] Optionally, in step S3, the first time t1 satisfies 2 min ≤ t1 ≤ 3 min. By limiting the first time of the intermittent pulse mode of the electromagnetic two-way valve 3, the valve is operated for a sufficient time to ensure that the evaporation rate of the liquid refrigerant accumulated in the gas-liquid separator 200 reaches more than 95%.

[0082] Optionally, in step S5, the second time t2 satisfies t2=30s. By limiting the second time t2 of the intermittent pulse mode of the electromagnetic two-way valve 3 in step S5 to t2=30s, the temperature in the gas-liquid separator 200 is ensured to be stably maintained above 25°C, so that the heat pump system can be normally started. When the heat pump system is normally started, the operating frequency of the compressor 100 is increased to 45Hz.

[0083] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. A person skilled in the art would be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A control method for low-temperature startup of a heat pump system, characterized in that: A heat pump system comprises a compressor (100) for supplying refrigerant, a gas-liquid separator (200) and an auxiliary system for low-temperature startup of the heat pump system, wherein the auxiliary system comprises a preheating bypass circuit (1), a pressure differential bypass valve (2) and an electromagnetic two-way valve (3), wherein the preheating bypass circuit (1) comprises an inlet end and an outlet end, wherein the inlet end is connected to the outlet of the compressor (100), and the outlet end is connected to the bottom of the gas-liquid separator (200), wherein the pressure differential bypass valve (2) is arranged on the preheating bypass circuit (1), and the electromagnetic two-way valve (3) is arranged between the pressure differential bypass valve (2) and the gas-liquid separator (200); The control method for low-temperature startup of a heat pump system comprises the following steps: S1, starting the heat pump system in low power mode; S2, adjusting the opening of the pressure differential bypass valve (2) to 50%; S3, operating the electromagnetic two-way valve (3) in an intermittent pulse mode to inject the refrigerant into the bottom of the gas-liquid separator (200) for a first time t1; S4, after the first time ends, operating the electromagnetic two-way valve (3) in a normally open mode; S5. The heat pump system further comprises a temperature sensor (300), wherein the temperature sensor (300) is used to detect the temperature value T of the gas-liquid separator (200). 气分 , when T is satisfied 气分 When the temperature is ≥25°C, the electromagnetic two-way valve (3) is switched back to the intermittent pulse mode and maintained for a second time t2; S6. When the second time ends, the preheating bypass circuit (1) is closed, the low-temperature mode is exited, and the heat pump system starts a normal heating cycle.

2. The control method for low-temperature startup of a heat pump system according to claim 1, characterized in that: In step S3, the intermittent pulse mode specifically opens the electromagnetic two-way valve (3) for 2 seconds and closes the electromagnetic two-way valve (3) for 1 second.

3. The control method for low-temperature startup of a heat pump system according to claim 1, characterized in that: In step S1, the following steps are also included: S11, turning on the compressor (100) and operating it in a low frequency mode of 10 Hz; S12. The heat pump system includes an evaporator (500), a condenser (600), and an electronic expansion valve (700) connected between the evaporator (500) and the condenser (600), and the opening of the electronic expansion valve (700) is adjusted to 70%.

4. The control method for low-temperature startup of a heat pump system according to claim 1, characterized in that: In step S3, the first time t1 satisfies 2min≤t1≤3min.

5. The control method for low-temperature startup of a heat pump system according to claim 1, characterized in that: In step S5, the second time t2 satisfies t2=30s.

6. A heat pump system, characterized in that The heat pump system is controlled by adopting the control method according to any one of claims 1 to 5 when starting at a low temperature.

7. The heat pump system according to claim 6, characterized in that The heat pump system further comprises an injection nozzle (4), the injection nozzle (4) being connected to the outlet end of the preheating bypass circuit (1), and the injection nozzle (4) being used for injecting multiple streams of rotating refrigerant into the bottom of the gas-liquid separator (200).

8. The heat pump system according to claim 7, characterized in that A filter element (5) is provided at the connection between the injection nozzle (4) and the outlet end.

9. The heat pump system according to claim 7, characterized in that The auxiliary system for low-temperature startup of a heat pump system further comprises a one-way valve (6), wherein the one-way valve (6) is arranged between the injection nozzle (4) and the electromagnetic two-way valve (3).

10. The heat pump system according to claim 6, characterized in that The auxiliary system for low-temperature startup of a heat pump system further comprises a capillary tube, which is arranged between the pressure differential bypass valve (2) and the electromagnetic two-way valve (3).

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