Control method for heat pump system and heat pump system

Abstract

The invention relates to a heat pump system, in particular to a control method for a heat pump system and the heat pump system, and aims to solve the problem that in the prior art, when the oil level is lacked, the problem of empty oil is generated or an oil film is thinned, a compressor is abraded or an air cylinder cracks, and the compressor is damaged. In order to achieve the purpose, the control method comprises the steps that after a compressor is started, N starting platforms are adopted for frequency raising control, a first heating piece and a second heating piece are controlled to continuously heat, and the second heating piece continuously heats and volatilizes a liquid refrigerant, so that it is guaranteed that the carried liquid refrigerant entering a cavity of the compressor is reduced, and the liquid refrigerant is prevented from being gasified to take away liquid oil; the problems of oil level loss, empty oil generation or oil film thinning are avoided, the first heating piece conducts continuous heating, the viscosity of hydraulic oil can be reduced, the hydraulic oil can return into the compressor more quickly, and therefore the compressor abrasion problem or the compressor damage problem such as air cylinder cracking is avoided.

Description

Technical Field

[0001] The present invention relates to a heat pump system, and in particular provides a control method for a heat pump system and a heat pump system. Background Art

[0002] An air-source heat pump is an energy-saving device that uses high-level energy to transfer heat from a low-level heat source, air, to a higher-level heat source. It's a form of heat pump. As the name suggests, a heat pump, like a pump, converts low-level heat energy that can't be directly utilized (such as heat contained in air, soil, and water) into usable high-level heat energy, thereby saving some high-level energy (such as coal, gas, oil, and electricity). Heat pump systems include heat pump water heaters and heat pump heaters.

[0003] When the heat pump system is started, there is a problem of mutual solubility between the refrigerant and the oil. When the solubility rate of the refrigerant and the oil is high, the refrigerant will cause phase change during the compression process. The phase change causes the oil to enter the pipeline of the heat pump system along with the gaseous refrigerant, resulting in oil level loss, oil air problem or oil film thinning, and ultimately causing compressor wear or cylinder cracking and other damage to the compressor.

[0004] In order to solve the above problems, it is urgent to develop a control method for a heat pump system and a heat pump system that can optimize the oil return of the compressor. Summary of the Invention

[0005] The present invention aims to solve the above technical problems, namely, to avoid the problems of compressor wear or cylinder cracking caused by oil level loss, oil emptying or oil film thinning during startup of existing heat pump systems.

[0006] In a first aspect, the present invention provides a control method for a heat pump system, the heat pump system comprising a compressor, a gas-liquid separator, and a throttle valve, the compressor and the gas-liquid separator being respectively provided with a first heating element and a second heating element, the control method comprising the following steps:

[0007] In response to a power-on instruction of the heat pump system, the compressor is started up and frequency-up control is performed using N starting platforms, where N is greater than or equal to 2, wherein each starting platform is provided with a corresponding operating frequency and maintenance time;

[0008] During the operation of each starting platform, adjusting the opening of the throttle valve, controlling the first heating element and the second heating element to continuously heat, and rising to the previous starting platform after each starting platform meets the entry condition;

[0009] After the exhaust gas superheat of the Nth starting platform reaches a third preset value M, the first heating element and the second heating element are controlled to stop heating, and the compressor is frequency-increased according to the target frequency.

[0010] In the preferred technical solution of the above-mentioned control method for the heat pump system, the step of "adjusting the opening of the throttle valve during the operation of each starting platform" includes: adjusting the opening of the throttle valve according to a first set cycle and a first set number of steps so that the intake superheat reaches a first preset value A.

[0011] In the preferred technical solution of the control method for the heat pump system mentioned above, the step of "rising to the previous starting platform after each starting platform meets the entry conditions" includes: when each starting platform reaches the corresponding operating frequency, the oil temperature superheat is greater than the second preset value Z, or, after running the starting platform for the maintenance time, rising to the previous starting platform.

[0012] In the preferred technical solution of the above-mentioned control method for the heat pump system, each starting platform is provided with a corresponding operating frequency as follows: the initial operating frequency of the first power-on platform of the compressor is less than 30 Hz, the operating frequency of the remaining starting platforms in the compressor except the first power-on platform is increased by 5 Hz-10 Hz compared with the operating frequency of the previous starting platform, and the operating frequency of the Nth starting platform of the compressor is less than or equal to 50 Hz.

[0013] In the preferred technical solution of the control method for the heat pump system, the first preset value A ranges from 1°C to 2°C, the second preset value Z ranges from 5°C to 8°C, and the third preset value M=Z+10.

[0014] In the preferred technical solution of the control method for the heat pump system, the control method further comprises: performing shutdown control on the compressor, wherein the shutdown of the compressor adopts frequency reduction control using N shutdown platforms, each shutdown platform having a corresponding operating frequency and maintenance time;

[0015] During the operation of each parking platform, the opening of the throttle valve is adjusted, and the flow rate is lowered to the next parking platform after each parking platform meets the entry conditions.

[0016] In the preferred technical solution of the above-mentioned control method for the heat pump system, the step of "adjusting the opening of the throttle valve during the operation of each shutdown platform" specifically includes: adjusting the opening of the throttle valve according to the second set cycle and the second set number of steps.

[0017] In the preferred technical solution of the control method for the heat pump system mentioned above, the step of "dropping to the next stop platform after each stop platform meets the entry conditions" includes: dropping to the next stop platform when each stop platform reaches the corresponding operating frequency, when the oil temperature superheat is less than the fourth preset value Q, or after running the stop platform for the maintenance time.

[0018] In the preferred technical solution of the control method for the heat pump system, the first set period and the second set period are 30 seconds; the first set number of steps and the second set number of steps are 10% of the current throttle valve opening.

[0019] In a second aspect, the present invention further provides a heat pump system, comprising a controller configured to execute the above control method for the heat pump system.

[0020] When adopting the above-mentioned technical solution, the control method and heat pump system for a heat pump system of the present invention adopt N starting platform frequency increase control after the compressor is started. During the operation of each starting platform, the second heating element in the gas-liquid separator is continuously heated to volatilize the liquid refrigerant in the cavity of the gas-liquid separator, thereby ensuring that the liquid refrigerant is reduced from entering the cavity of the compressor, and then preventing the liquid refrigerant from vaporizing and taking away the hydraulic oil, avoiding the problems of oil level loss, oil emptying or thinning of the oil film, avoiding the problems of compressor wear or cylinder cracking and other damage to the compressor. The first heating element of the compressor is continuously heated to increase the oil temperature superheat of the hydraulic oil, thereby increasing the refrigerant exhaust temperature in the heat pump system, reducing the viscosity of the hydraulic oil, and allowing the hydraulic oil to return to the compressor faster, further avoiding the problems of compressor wear or cylinder cracking and other damage to the compressor.

[0021] Furthermore, the control method and heat pump system for a heat pump system of the present invention adopt N shutdown platforms for frequency reduction control when the compressor stops, that is, the compressor is controlled in the opposite direction of frequency increase when it stops, to ensure that the inertia of the compressor is reduced when it stops, and the hydraulic oil in the cavity of the compressor is not thrown out but remains in the cavity of the compressor. When it is restarted, the compressor will not cause a temporary oil shortage, thereby further avoiding problems such as compressor wear or cylinder cracking that damage the compressor. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

[0023] Figure 1 is a schematic structural diagram of a heat pump system according to an embodiment of the present invention;

[0024] Figure 2 is a schematic flow chart of a control method for a heat pump system according to an embodiment of the present invention;

[0025] Figure 3 is a schematic control diagram of a compressor startup process of a heat pump system according to an embodiment of the present invention;

[0026] Figure 4 This is a schematic control diagram of the compressor shutdown process of a heat pump system according to an embodiment of the present invention.

[0027] The symbols in the figure mean the following:

[0028] 100 heat pump systems,

[0029] 1 first sensor, 2 second sensor, 3 third sensor, 4 fourth sensor, 5 fifth sensor, 6 sixth sensor, 7 seventh sensor, 8 eighth sensor, 9 ninth sensor, 10 tenth sensor, 11 eleventh sensor, 12 low voltage switch, 13 high voltage switch,

[0030] 20 compressor, 21 first heating element, 30 gas-liquid separator, 31 second heating element, 40 condenser, 50 four-way reversing valve, 60 economizer, 61 low-pressure part, 62 high-pressure part, 70 throttle valve, 71 first throttle valve, 72 second throttle valve, 80 distributor, 90 evaporator. DETAILED DESCRIPTION

[0031] The preferred embodiments of the present application are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are merely used to explain the technical principles of the present application and are not intended to limit the scope of protection of the present application. For example, in the following embodiments, although the various steps are described in a sequential order, it will be understood by those skilled in the art that in order to achieve the effect of the present embodiment, the different steps do not need to be performed in such an order, and they can be performed simultaneously (in parallel) or in a reversed order, and these simple variations are all within the scope of protection of the present application.

[0032] Figure 1 Schematic diagram of a heat pump system according to an embodiment of the present invention. Figure 2 is a schematic flow chart of a control method for a heat pump system according to an embodiment of the present invention. Figure 3 This is a schematic control diagram of the compressor startup process of a heat pump system according to an embodiment of the present invention. Figure 4 This is a schematic control diagram of the compressor shutdown process of a heat pump system according to an embodiment of the present invention.

[0033] In order to avoid the problems of oil level loss, oil dryness or oil film thinning during startup of existing heat pump systems, which may cause compressor wear or cylinder cracking and damage the compressor. Figure 1 See also Figure 2-Figure 4 , an embodiment of the present invention provides a control method for a heat pump system, such as Figure 1As shown, the heat pump system 100 can generally include a refrigerant circulation loop formed by a compressor 20, a four-way reversing valve 50, a condenser 40, a throttle valve 70, a distributor 80, an evaporator 90, and a gas-liquid separator 30. The compressor 20 is provided with a first heating element 21, and the gas-liquid separator 30 is provided with a second heating element 31. In a specific implementation, the first heating element 21 and the second heating element 31 can be heating belts or heating wires. Furthermore, the heat pump system 100 can also include an economizer 60, which includes a low-pressure part 61 and a high-pressure part 62 of the economizer 60. The throttle valve 70 includes a first throttle valve 71 and a second throttle valve 72. The first throttle valve 71 plays a primary throttling role, and the second throttle valve 72 plays an auxiliary throttling role. The exhaust port of compressor 20 is connected to condenser 40 via four-way reversing valve 50. Condenser 40 is connected to high-pressure section 62 of economizer 60. High-pressure section 62 of economizer 60 is connected to low-pressure section 61 of economizer 60 via second throttle valve 72. Low-pressure section 61 of economizer 60 is connected to the intake port of compressor 20. High-pressure section 62 of economizer 60 is also connected to first throttle valve 71. First throttle valve 71 is connected to evaporator 90 via distributor 80. Evaporator 90 is connected to the intake port of compressor 20 via four-way reversing valve 50 and gas-liquid separator 30. Furthermore, heat pump system 100 also includes first to eleventh sensors 1 through 11, each of which is a temperature sensor. First sensor 1 is installed at the air inlet of gas-liquid separator 30 to detect the intake air temperature. Second sensor 2 is installed at the exhaust port of compressor 20 to detect the exhaust air temperature. The third sensor 3 is installed at the air inlet of the low-pressure section 61 of the economizer 60 to detect the air inlet temperature of the economizer 60. The fourth sensor 4 is installed at the air outlet of the low-pressure section 61 of the economizer 60 to detect the air outlet temperature of the economizer 60. The fifth sensor 5 is installed at a location in the evaporator 90 prone to frost formation to detect the frost temperature. The sixth sensor 6 is installed at the evaporator 90 to detect the evaporation temperature. The seventh sensor 7 is installed at the condenser 40 to detect the condensation temperature. The eighth sensor 8 is installed at the water outlet of the condenser 40 to detect the water outlet temperature. The ninth sensor 9 is installed at the water inlet of the condenser 40 to detect the water inlet temperature. The tenth sensor 10 is installed at the evaporator 90 to detect the ambient temperature. The eleventh sensor 11 is installed in the compressor 20 to detect the oil temperature. Furthermore, the heat pump system 100 also includes a high-pressure switch 13 and a low-pressure switch 12. The high-pressure switch 13 is installed between the exhaust port of the compressor 20 and the four-way reversing valve 50 to open and close the high-pressure section of the refrigerant circulation circuit. The low-pressure switch 12 is installed between the air inlet of the gas-liquid separator 30 and the four-way reversing valve 50, and is used to open and close the low-pressure section of the refrigerant circulation loop.

[0034] Working principle of refrigerant circulation circuit:

[0035] The refrigerant enters the compressor 20 through the air intake of the compressor 20. The compressor 20 compresses the refrigerant to form a high-temperature and high-pressure refrigerant. The high-temperature and high-pressure refrigerant is discharged from the exhaust port of the compressor 20, and is reversed through the four-way reversing valve 50 to enter the condenser 40 for heat exchange and condensation when it is cold to form a high-pressure refrigerant, and the cold water passing through the condenser 40 is heated to hot water. The high-pressure refrigerant passes through the economizer 60, and a part of the high-pressure refrigerant is reduced in pressure by the second throttle valve 72 and enters the compressor 20. The other part of the high-pressure refrigerant is reduced in pressure by the first throttle valve 71 and enters the distributor 80 to the evaporator 90 for heat exchange, evaporation and heat dissipation to form a low-pressure refrigerant. The low-pressure refrigerant is reversed through the four-way reversing valve 50 and enters the compressor 20 through the gas-liquid separator 30 and the air intake of the compressor 20 to start the next cycle.

[0036] like Figure 2 As shown, the control method for the heat pump system includes S100 compressor start control, which specifically includes:

[0037] S101, in response to the start-up instruction of the heat pump system, the compressor is started and frequency-increasing control is performed using N starting platforms, N ≥ 2, wherein each starting platform has a corresponding operating frequency and maintenance time. Figure 3 As shown, for example, N=4, meaning that after the compressor is started, four starting platforms are used for frequency increase control. The four starting platforms are, in descending order, the first power-on platform, the first platform, the second platform, and the third platform. Of course, in other embodiments, N can also be two starting platforms, three starting platforms, five starting platforms, or other starting platforms ≥ 2, depending on the operating conditions of the heat pump system.

[0038] S102, during the operation of each starting platform, adjust the opening of the throttle valve, control the first heating element and the second heating element to continue heating, and rise to the previous starting platform after each starting platform meets the entry conditions. Among them, the second heating element is continuously heated, which can slowly volatilize the liquid refrigerant in the gas-liquid separator and volatilize the liquid refrigerant in the cavity of the gas-liquid separator, thereby ensuring that the refrigerant carrying liquid refrigerant into the compressor cavity is reduced, and then prevent the refrigerant from vaporizing and taking away the hydraulic oil (referred to as oil). The first heating element is continuously heated, which can increase the exhaust temperature of the refrigerant in the compressor, reduce the oil viscosity, and enable the oil to return to the compressor faster.

[0039] S103, after the exhaust superheat of the Nth starting platform reaches the third preset value M, the first heating element and the second heating element are controlled to stop heating, and the compressor is quickly increased in frequency according to the target frequency, that is, compared with the aforementioned method of increasing the frequency by N starting platforms, rapid frequency increase is achieved. That is to say, after the Nth starting platform is stabilized, the frequency of the compressor is brought close to the target frequency. The target frequency usually refers to the operating frequency when the compressor is working normally. The target frequency depends on the indoor temperature and the set temperature. For example, the indoor temperature is 10°C and the set temperature is 25°C, and the highest frequency operation is required at this time. For another example, the indoor temperature is 20°C and the set temperature is 21°C or 22°C, and a suitable frequency operation is required at this time. It can be seen that the difference between the indoor temperature and the set temperature determines whether the target frequency is quickly increased, slowly increased, or reduced in frequency. Among them,

[0040] Exhaust superheat = exhaust temperature - high pressure saturated refrigerant temperature

[0041] Under the condition of adopting the above-mentioned technical scheme, the control method for the heat pump system of this embodiment adopts N starting platform frequency increase control after the compressor is started. During the operation of each starting platform, the second heating element in the gas-liquid separator is continuously heated to volatilize the liquid refrigerant in the cavity of the gas-liquid separator, thereby ensuring that the liquid refrigerant is reduced from entering the cavity of the compressor, and then preventing the liquid refrigerant from vaporizing and taking away the liquid oil, avoiding the occurrence of oil level loss, oil emptying problems or oil film thinning, avoiding the problems of compressor wear or cylinder cracking and other damage to the compressor. The first heating element of the compressor is continuously heated to increase the oil temperature superheat of the hydraulic oil, thereby increasing the refrigerant exhaust temperature in the heat pump system, reducing the viscosity of the hydraulic oil, and allowing the hydraulic oil to return to the compressor faster, thereby further avoiding the problems of compressor wear or cylinder cracking and other damage to the compressor.

[0042] In a preferred embodiment of the control method for a heat pump system, the step of "adjusting the throttle valve opening during each startup platform operation" in S102 includes adjusting the throttle valve opening according to a first predetermined period and a first predetermined number of steps to bring the intake air superheat to a first predetermined value A. Specifically, the first predetermined period may be 30 seconds, and the first predetermined number of steps may be 10% of the current throttle valve opening. In practice, the throttle valve opening is adjusted every 30 seconds, and the number of steps is a 10% increase in the current throttle valve opening.

[0043] In a preferred embodiment of the above control method for a heat pump system, the first preset value A is in the range of 1°C to 2°C.

[0044] like Figure 3As shown, in this embodiment, when the compressor is powered on for the first time, the throttle valve opening is set to an initial opening of 20%-30% of the total opening, ensuring that the suction superheat is within the first preset value A of 1°C-2°C. The adjustment cycle is 30 seconds, and the adjustment step is to increase the current throttle valve opening by 10%.

[0045] Suction superheat = suction temperature - evaporating temperature.

[0046] In a preferred embodiment of the above-mentioned control method for a heat pump system, the step of "rising to the previous starting platform after each starting platform meets the entry conditions" in S102 includes: when each starting platform reaches the corresponding operating frequency, the oil temperature superheat is greater than the second preset value Z, or, after the maintenance time of the running starting platform, rising to the previous starting platform.

[0047] In a preferred embodiment of the above-mentioned control method for a heat pump system, the initial operating frequency of the first power-on platform of the compressor is less than 30 Hz, the operating frequencies of the remaining starting platforms in the compressor except the first power-on platform are increased by 5 Hz-10 Hz compared with the operating frequency of the previous starting platform, and the operating frequency of the Nth starting platform of the compressor is less than or equal to 50 Hz.

[0048] like Figure 3 As shown, in a specific implementation, for example, the operating frequency of the platform when powered on for the first time is 20 Hz, the operating frequency of the first platform is 30 Hz, the operating frequency of the second platform is 40 Hz, and the operating frequency of the third platform is 45 Hz. For another example, the operating frequency of the platform when powered on for the first time is 15 Hz, the operating frequency of the first platform is 25 Hz, the operating frequency of the second platform is 35 Hz, and the operating frequency of the third platform is 50 Hz. For another example, the operating frequency of the platform when powered on for the first time is 30 Hz, the operating frequency of the first platform is 35 Hz, the operating frequency of the second platform is 40 Hz, and the operating frequency of the third platform is 45 Hz. The maintenance time of the platform when powered on for the first time, the first platform, the second platform, and the third platform can be the same or different. For example: the maintenance time of the platform when powered on for the first time, the first platform, the second platform, and the third platform are all 40S-60S.

[0049] In a preferred embodiment of the control method for a heat pump system, the second preset value Z is in the range of 5°C to 8°C, and the value of Z can be 5°C, 6°C, 7°C, or 8°C. The third preset value M=Z+10, and the value of M can be 15°C, 16°C, 17°C, or 18°C.

[0050] like Figure 3 As shown, in specific implementation, when each starting platform reaches the corresponding operating frequency, the oil temperature superheat is greater than the second preset value Z = 5°C to 8°C, or after the maintenance time of the running starting platform, it rises to the previous starting platform.

[0051] Oil superheat = current oil temperature - high pressure saturated refrigerant temperature

[0052] For example, the frequency ramp-up rate for the first power-on platform of the compressor is 1 Hz / 3s. When the frequency reaches 30 Hz, the first throttle valve opening is adjusted to a suction superheat of 1°C, and one of the following two conditions is met, the frequency is ramped up to the first platform: if the hold time is 40 seconds or the oil superheat exceeds 5°C. The frequency ramp-up rate for the first platform of the compressor is 1 Hz / 3s. When the frequency reaches 35 Hz, the first throttle valve opening is adjusted to a suction superheat of 1°C, and one of the following two conditions is met, the frequency is ramped up to the second platform: if the hold time is 40 seconds or the oil superheat exceeds 5°C. The compressor's second frequency ramp-up rate is 1 Hz / 3 seconds. When the second frequency ramp reaches 40 Hz, the first throttle valve opening is adjusted to a suction superheat of 1°C. If either of the following two conditions is met, the compressor ramps up to the second frequency ramp: if the hold time is 40 seconds, or if the oil superheat exceeds 5°C, the compressor ramps up to the third frequency ramp. The compressor's third frequency ramp-up rate is 1 Hz / 3 seconds. When the third frequency ramp reaches 45 Hz, the first throttle valve opening is adjusted to a suction superheat of 1°C. The exhaust superheat is maintained at a third preset value, M, of 18°C. The first and second heating elements are then controlled to stop heating, and the compressor rapidly ramps up to the target frequency.

[0053] like Figure 2 As shown, in the preferred embodiment of the control method for the heat pump system, the control method further includes: S200 performing shutdown control on the compressor, and the shutdown control step of the compressor in S200 specifically includes:

[0054] The shutdown of the S201 compressor adopts N shutdown platforms to reduce the frequency, and each shutdown platform has a corresponding operating frequency and maintenance time. Figure 4 As shown, when the compressor stops, it is controlled in the opposite direction of the frequency increase to ensure that the inertia is reduced during shutdown, and the oil in the compression chamber of the compressor is not thrown out but remains in the compression chamber. When it is restarted, the compressor will not suffer from a temporary oil shortage. The frequency reduction rate of each shutdown platform is 1hz / 3s. For example, if four startup platforms are used when the compressor starts, then four frequency reduction shutdown platforms are used when the compressor stops. In specific implementation, Figure 4 As shown, the four parking platforms are in the order from top to bottom: parking platform four, parking platform three, parking platform two and parking platform one.

[0055] S202 adjusts the opening of the throttle valve during the operation of each parking platform, and descends to the next parking platform after each parking platform meets the entry conditions.

[0056] Furthermore, the control method for a heat pump system of the present invention adopts N shutdown platforms for frequency reduction control when the compressor stops, that is, the compressor is controlled in the opposite direction of frequency increase when it stops, ensuring that the inertia of the compressor is reduced when it stops, and the hydraulic oil in the cavity of the compressor is not thrown out but remains in the cavity of the compressor. When it is started again, the compressor will not cause a temporary oil shortage, thereby further avoiding problems such as compressor wear or cylinder cracking that damage the compressor.

[0057] In the preferred embodiment of the control method for the heat pump system described above, the step of "adjusting the throttle valve opening during the operation of each shutdown platform" in S202 specifically includes adjusting the throttle valve opening according to a second set period and a second set number of steps. Specifically, the second set period may be 30 seconds, and the second set number of steps may be 10% of the current throttle valve opening. In practice, the throttle valve opening is adjusted once every 30 seconds, and the number of steps is a 10% decrease in the current throttle valve opening.

[0058] When implementing it specifically, Figure 4 As described above, the shutdown platform 4 is the state of the compressor before shutdown. At this time, the operating frequency of the compressor is the operating frequency before shutdown, for example, 60 Hz, and the opening of the first throttle valve is fully open.

[0059] In a preferred embodiment of the control method for a heat pump system, the step of "descending to the next parking platform after each parking platform meets the entry condition" in S202 includes descending to the next parking platform when each parking platform reaches the corresponding operating frequency, when the oil temperature superheat is less than a fourth preset value Q, or after the maintenance time of the operating parking platform has expired. Q is -10°C, and the maintenance time of the parking platform is 5-10 seconds. The next parking platform is entered when either of these two conditions is met. Specifically, the next parking platform is entered when the oil temperature drops by 10°C, or when the maintenance time of the parking platform is 5-10 seconds.

[0060] like Figure 4 As shown, in a specific implementation, the operating frequency of stop platform 4 is 60 Hz, the operating frequency of stop platform 3 is 40 Hz, the operating frequency of stop platform 2 is 20 Hz, and the operating frequency of stop platform 1 is 0 Hz. When the oil temperature drops by 10°C, or the stop platform is maintained for 5-10 seconds, the next stop platform is entered.

[0061] Stop platform four adjusts the opening of the first throttle valve, with an adjustment cycle of 30 seconds and an adjustment step of reducing the current opening by 10%. When the oil temperature drops by 10°C, or the shutdown platform is maintained for 5 seconds, it enters stop platform three. Stop platform three drops to a frequency of 40 Hz. When the oil temperature drops by 10°C, or the shutdown platform is maintained for 5 seconds, it enters stop platform two. Stop platform two drops to a frequency of 20 Hz. When the oil temperature drops by 10°C, or the shutdown platform is maintained for 5 seconds, it enters stop platform one. When stop platform one drops to a frequency of 0 Hz, the compressor stops. After the compressor stops for 30 seconds or a certain period of time, all parts and components (such as fans, throttle valves, etc.) reset and automatically shut down.

[0062] See also Figure 1 The heat pump system 100 according to the embodiment of the present invention further includes a controller (not shown) configured to execute the above-described control method for a heat pump system. The controller receives temperature values ​​from the first sensor 1 to the eleventh sensor and controls the compressor 20, the first heating element 21, the second heating element 31, and the like based on the temperature values.

[0063] When adopting the above technical solution, the controller of the heat pump system of the present invention can execute the above control method for the heat pump system, that is, after the compressor is started, N starting platforms are used for frequency increase control. During the operation of each starting platform, the second heating element in the gas-liquid separator is continuously heated to volatilize the liquid refrigerant in the cavity of the gas-liquid separator, thereby ensuring that the liquid refrigerant is reduced from entering the cavity of the compressor, and then preventing the liquid refrigerant from vaporizing and taking away the liquid oil, avoiding the occurrence of oil level loss, empty oil problems or oil film thinning, avoiding compressor wear problems or cylinder cracking and other problems that damage the compressor. The first heating element of the compressor is continuously heated, which can increase the oil temperature superheat of the hydraulic oil, thereby increasing the refrigerant exhaust temperature in the heat pump system, reducing the viscosity of the hydraulic oil, and allowing the hydraulic oil to return to the compressor faster, thereby further avoiding the occurrence of compressor wear problems or cylinder cracking and other problems that damage the compressor.

[0064] Furthermore, the controller of the heat pump system of the present invention can execute the above-mentioned control method for the heat pump system, that is, when the compressor is shut down, N shutdown platforms are used for frequency reduction control, that is, when the compressor is shut down, it is controlled in the opposite direction of frequency increase to ensure that the inertia of the compressor is reduced when it is shut down, and the hydraulic oil in the compressor cavity is not thrown out but remains in the compressor cavity. When it is started again, the compressor will not cause a temporary lack of oil, thereby further avoiding problems such as compressor wear or cylinder cracking that damage the compressor.

[0065] Those skilled in the art will appreciate that although some embodiments described herein include certain features included in other embodiments but not other features, combinations of features from different embodiments are intended to be within the scope of this application and to form different embodiments. For example, in the claims of this application, any of the claimed embodiments may be used in any combination.

[0066] It should be noted that although the detailed steps of the method of the present application are described in detail above, without departing from the basic principles of the present application, technical personnel in this field can combine, split and change the order of the above steps. The modified technical solution does not change the basic concept of the present application and therefore falls within the scope of protection of the present application.

[0067] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

Claims

1. A control method for a heat pump system, characterized in that: The heat pump system includes a compressor, a gas-liquid separator and a throttle valve, wherein the compressor and the gas-liquid separator are respectively provided with a first heating element and a second heating element, and the control method includes the following steps: In response to a power-on instruction of the heat pump system, the compressor is started up and frequency-up control is performed using N starting platforms, where N is greater than or equal to 2, wherein each starting platform is provided with a corresponding operating frequency and maintenance time; During the operation of each starting platform, adjusting the opening of the throttle valve, controlling the first heating element and the second heating element to continuously heat, and rising to the previous starting platform after each starting platform meets the entry condition; After the exhaust gas superheat of the Nth starting platform reaches a third preset value M, the first heating element and the second heating element are controlled to stop heating, and the compressor is frequency-increased according to the target frequency.

2. The control method for a heat pump system according to claim 1, characterized in that: The step of "adjusting the opening of the throttle valve during the operation of each starting platform" includes: adjusting the opening of the throttle valve according to a first set period and a first set number of steps so that the intake superheat reaches a first preset value A.

3. The control method for a heat pump system according to claim 2, characterized in that: The step of "rising to the previous starting platform after each starting platform meets the entry conditions" includes: when each starting platform reaches the corresponding operating frequency, the oil temperature superheat is greater than the second preset value Z, or after running the starting platform for the maintenance time, rising to the previous starting platform.

4. The control method for a heat pump system according to claim 3, characterized in that: Each starting platform is provided with a corresponding operating frequency, specifically: the initial operating frequency of the first power-on platform of the compressor is less than 30 Hz, the operating frequency of the remaining starting platforms in the compressor except the first power-on platform is increased by 5 Hz-10 Hz compared with the operating frequency of the previous starting platform, and the operating frequency of the Nth starting platform of the compressor is less than or equal to 50 Hz.

5. The control method for a heat pump system according to claim 4, characterized in that: The first preset value A has a value range of 1°C-2°C, the second preset value Z has a value range of 5°C-8°C, and the third preset value M=Z+10.

6. The control method for a heat pump system according to claim 1, characterized in that: The control method further includes: performing shutdown control on the compressor, wherein the shutdown of the compressor adopts frequency reduction control of N shutdown platforms, and each shutdown platform is provided with a corresponding operating frequency and maintenance time; During the operation of each parking platform, the opening of the throttle valve is adjusted, and the flow rate is lowered to the next parking platform after each parking platform meets the entry conditions.

7. The control method for a heat pump system according to claim 6, characterized in that: The step of "adjusting the opening of the throttle valve during the operation of each shutdown platform" specifically includes: adjusting the opening of the throttle valve according to a second set cycle and a second set number of steps.

8. The control method for a heat pump system according to claim 7, characterized in that: The step of "dropping to the next parking platform after each parking platform meets the entry conditions" includes: dropping to the next parking platform when each parking platform reaches the corresponding operating frequency, when the oil temperature superheat is less than the fourth preset value Q, or after running the parking platform for the maintenance time.

9. The control method for a heat pump system according to claim 2 or 7, characterized in that: The first setting period and the second setting period are 30 seconds; the first setting number of steps and the second setting number of steps are 10% of the current throttle valve opening.

10. A heat pump system, characterized in that: The heat pump system includes a controller configured to execute the control method for a heat pump system according to any one of claims 1 to 9.

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