Air source heat pump unit refrigeration control method and air source heat pump unit

Abstract

The application provides an air source heat pump unit refrigeration control method and an air source heat pump unit, and belongs to the technical field of air conditioners. The method comprises the following steps: in a low ambient temperature working condition, if the outlet water temperature is greater than the upper limit value of a target outlet water temperature interval, a compressor and a condenser fan are started, the compressor is operated at the highest frequency after a first preset time, and the rotating speed of the condenser fan is adjusted according to the relationship between the real-time compression ratio and the preset compression ratio interval boundary value; when the outlet water temperature decreases to the target outlet water temperature interval, the compressor is operated at a reduced frequency in a PID adjustment mode, and the rotating speed of the condenser fan is adjusted according to the relationship between the compression and the preset compression ratio interval boundary value in the reduced frequency stage. The compressor is operated at the highest frequency for rapid refrigeration in the large temperature difference stage, the compressor is switched to the outlet water temperature PID reduced frequency operation in the small temperature difference return difference interval, and the rotating speed of the condenser fan is adjusted and controlled based on the actual compression ratio, so that the steady-state temperature control precision is improved, and the reliability can be ensured.

Description

Technical Field

[0001] This invention belongs to the field of air conditioning technology, and in particular relates to a cooling control method for an air source heat pump unit and an air source heat pump unit. Background Technology

[0002] When an air source heat pump unit operates under cooling conditions at low ambient temperatures (≤5℃), the outdoor finned condenser is affected by enhanced heat exchange from the low-temperature cold air, and its heat dissipation capacity far exceeds the unit's cooling and condensing requirements, resulting in a rapid and significant drop in condensing pressure. Meanwhile, the unit's evaporator maintains the cooling demand for chilled water, and its evaporation pressure remains relatively stable. Consequently, the ratio of the compressor's discharge pressure to its suction pressure (i.e., the compression ratio) continues to be lower than the minimum allowable compression ratio, and the unit enters an unsafe low compression ratio operating range.

[0003] Existing low ambient temperature refrigeration control technologies typically employ a single-temperature PID variable frequency control mode throughout the entire operation cycle. During this cycle, the compressor frequency is continuously adjusted by the PID based on the water temperature deviation. When the water temperature deviates significantly from the set value and rapid cooling is urgently needed, the PID algorithm is constrained by the adjustment slope and integral limit, resulting in a slow compressor frequency increase, a lag in refrigerant circulation, a slow water cooling rate, and insufficient temperature control response. Simultaneously, the condenser fan is mostly adjusted according to the water temperature or condensing temperature. Under conditions of low ambient temperature and excessive condenser heat dissipation, the condensing pressure continues to decrease, and the compression ratio deviates from the reasonable operating range, easily leading to a deterioration in the stability of the compressor's operating conditions. Summary of the Invention

[0004] The first technical problem solved by this invention is to provide a cooling control method for air source heat pump units, which can improve the working reliability of the compressor under low ambient temperature conditions, while taking into account both rapid cooling and stable temperature control.

[0005] The first technical problem solved by this invention is to provide an air source heat pump unit that can improve the working reliability of the compressor under low ambient temperature conditions, while taking into account both rapid cooling and stable temperature control.

[0006] The first technical problem mentioned above is solved by the following technical solution: A cooling control method for an air source heat pump unit, the unit comprising a compressor, a condenser, and a condenser fan, the method comprising: Obtain ambient temperature T s Real-time outlet water temperature T of the unit cs and the real-time compression ratio A of the compressor s ; When the ambient temperature T s Less than or equal to the preset low ambient temperature threshold T a At that time, determine the real-time outlet water temperature T. csIs it greater than the upper limit T of the target outlet water temperature range? max ; If so, control the compressor and condenser fan to start, and after the first preset running time, control the compressor to run at the highest frequency, and adjust according to the real-time compression ratio A. s The condenser fan speed is adjusted according to the relationship between the real-time compression ratio and the boundary values ​​of the preset compression ratio range, thereby controlling the real-time compression ratio A. s Adjust to within the preset compression ratio range; When the outlet water temperature T cs When the water temperature drops to the target outlet water temperature range, the compressor is controlled to operate in PID control mode with reduced frequency to maintain the outlet water temperature T. cs Approaching the target outlet water temperature T n The target effluent temperature T n Located within the target outlet water temperature range, during the frequency reduction operation phase, based on the real-time compression ratio A s The condenser fan speed is adjusted according to the relationship between the real-time compression ratio and the boundary values ​​of the preset compression ratio range, thereby controlling the real-time compression ratio A. s Adjust to within the preset compression ratio range; When the outlet water temperature T cs The temperature drops to the lower limit T of the target effluent temperature range. min When necessary, control the compressor and condenser fan to stop; If not, keep the compressor and condenser fan off, and return to the previous step to determine the real-time outlet water temperature T. cs Is it greater than the upper limit T of the target outlet water temperature range? max The steps.

[0007] The air source heat pump unit refrigeration control method provided by this invention has the following advantages compared with the prior art: This invention, under low ambient temperature conditions, controls the compressor operating frequency in stages based on the deviation between the outlet water temperature and the target temperature range: when the outlet water temperature exceeds the upper limit of the target temperature range, the compressor operates at a preset maximum frequency, avoiding the PID frequency ramp-up lag problem, significantly increasing cooling capacity, shortening cooling time, and achieving rapid cooling; simultaneously, the condenser fan uses closed-loop speed regulation based on the real-time compression ratio to actively suppress excessive drops in condensing pressure, and maintains the real-time compression ratio A... sThe compressor is adjusted to a preset compression ratio range to improve operational reliability. When the outlet water temperature drops to the target temperature range, the compressor operates at a reduced frequency using PID control mode, bringing the outlet water temperature closer to the target temperature. The compressor frequency decreases linearly and smoothly, without abrupt or drastic frequency reductions. This results in gradual changes in system refrigerant flow, pipeline pressure, and exhaust temperature, reducing the risk of malfunctions such as insufficient oil return, liquid slugging, and abnormal pipeline vibration caused by sudden frequency drops. Simultaneously, the condenser fan uses closed-loop speed regulation based on the real-time compression ratio to actively suppress excessive drops in condensing pressure, maintaining the real-time compression ratio A. s By adjusting the compressor to a preset compression ratio range, the stability and service life of the unit are improved. In summary, this invention employs a two-stage coupled control strategy: during the large temperature difference phase, the compressor cools rapidly at its highest frequency, and the condenser fan adjusts its speed according to the compression ratio; during the small temperature difference hysteresis phase, the compressor operates at a reduced frequency using PID control of the water temperature, and the condenser fan maintains compression ratio regulation. This strategy not only improves the cooling response speed and steady-state temperature control accuracy but also stabilizes the system compression ratio throughout the entire process, thus improving the refrigeration cycle conditions.

[0008] In an optional embodiment, the step of adjusting the real-time compression ratio A... s The condenser fan speed is adjusted according to the relationship between the real-time compression ratio and the boundary values ​​of the preset compression ratio range, thereby controlling the real-time compression ratio A. s Adjusting to a preset compression ratio range, including: Determine the real-time compression ratio A s Is it within the preset compression ratio range? When the real-time compression ratio A s When the compression ratio exceeds the upper limit of the preset compression ratio range, increase the condenser fan speed and return to the previous step to determine the real-time compression ratio A. s The step of determining whether it is within the preset compression ratio range; When the real-time compression ratio A s When the compression ratio is less than the lower limit of the preset compression ratio range, reduce the speed of the condenser fan and return to the execution state to determine the real-time compression ratio A. s The step of determining whether it is within the preset compression ratio range; When the real-time compression ratio A s When the compression ratio is within the preset range, maintain the condenser fan speed and return to the previous step to determine the real-time compression ratio A. s The step of determining whether it is within the preset compression ratio range.

[0009] In an optional embodiment, prior to reducing the speed of the condenser fan, the method further includes: Determine if the condenser fan speed has reached the minimum allowable speed; If so, shut down the condenser fan.

[0010] In an optional embodiment, after the control of the condenser fan to stop, the method further includes: In real-time compression ratio A s When the compression ratio exceeds the upper limit of the preset range, the condenser fan will be activated.

[0011] In an optional embodiment, during the frequency reduction operation phase, after the control of the condenser fan to stop, the following further step is taken: If after the second preset time, the real-time compression ratio A s If the value is still less than the lower limit of the preset compression ratio range, then the compressor is controlled to operate at a preset frequency ramp-up rate to increase the real-time compression ratio A. s It is within the preset compression ratio range.

[0012] In an optional embodiment, after controlling the compressor to operate at a preset frequency ramp-up rate, the following steps are included: If after the third preset time, the real-time compression ratio A s If the value is still less than the lower limit of the preset compression ratio range, the compressor will be shut down.

[0013] In an optional embodiment, the unit further includes a solenoid two-way valve, a capillary assembly, and an oil separator disposed between the compressor's exhaust port and the condenser, wherein the oil separator, the solenoid two-way valve, the capillary assembly, and the compressor's intake port are connected in sequence via pipelines. During the frequency reduction operation phase, the method further includes: When the real-time compression ratio A s When the compressor is within a preset compression ratio range, its operating frequency is obtained. The target oil return cycle is determined based on the operating frequency. When the compressor's cumulative running time reaches the target oil return cycle, the solenoid two-way valve is opened to perform the oil return operation.

[0014] In an optional embodiment, determining the target return oil cycle based on the operating frequency includes: When the operating frequency is less than the preset frequency, the target oil return cycle is determined to be the first oil return cycle; the preset frequency is the upper limit of the compressor's low-frequency operating range. When the operating frequency is greater than or equal to the preset frequency, the target oil return cycle is determined to be the second oil return cycle; The duration of the first oil return cycle is shorter than the duration of the second oil return cycle.

[0015] In an optional embodiment, during the return oil operation, the method further includes: When the operating frequency is less than the preset frequency, the compressor is controlled to increase its frequency until the oil return ends. The preset frequency is the upper limit of the low frequency range.

[0016] The second technical problem mentioned above is solved by the following technical solution: An air source heat pump unit is characterized in that the unit includes a controller and a compressor, a condenser and a condenser fan respectively connected to the controller, the controller being used to execute the air source heat pump unit refrigeration control method as described above.

[0017] The air source heat pump unit provided by this invention has the following advantages compared with the prior art: This invention, under low ambient temperature conditions, controls the compressor operating frequency in stages based on the deviation between the outlet water temperature and the target temperature range: when the outlet water temperature exceeds the upper limit of the target temperature range, the compressor operates at a preset maximum frequency, avoiding the PID frequency ramp-up lag problem, significantly increasing cooling capacity, shortening cooling time, and achieving rapid cooling; simultaneously, the condenser fan uses closed-loop speed regulation based on the real-time compression ratio to actively suppress excessive drops in condensing pressure, and maintains the real-time compression ratio A... s The compressor is adjusted to a preset compression ratio range to improve operational reliability. When the outlet water temperature drops to the target temperature range, the compressor operates at a reduced frequency using PID control mode, bringing the outlet water temperature closer to the target temperature. The compressor frequency decreases linearly and smoothly, without abrupt or drastic frequency reductions. This results in gradual changes in system refrigerant flow, pipeline pressure, and exhaust temperature, reducing the risk of malfunctions such as insufficient oil return, liquid slugging, and abnormal pipeline vibration caused by sudden frequency drops. Simultaneously, the condenser fan uses closed-loop speed regulation based on the real-time compression ratio to actively suppress excessive drops in condensing pressure, maintaining the real-time compression ratio A. s By adjusting the compressor to a preset compression ratio range, the stability and service life of the unit are improved. In summary, this invention employs a two-stage coupled control strategy: during the large temperature difference phase, the compressor cools rapidly at its highest frequency, and the condenser fan adjusts its speed according to the compression ratio; during the small temperature difference hysteresis phase, the compressor operates at a reduced frequency using PID control of the water temperature, and the condenser fan maintains compression ratio regulation. This strategy not only improves the cooling response speed and steady-state temperature control accuracy but also stabilizes the system compression ratio throughout the entire process, thus improving the refrigeration cycle conditions. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of an air source heat pump unit provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a cooling control method for an air source heat pump unit provided in an embodiment of the present invention; Figure 3This is a schematic diagram of a condenser fan adjustment process provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of a high-frequency operation phase provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of a frequency reduction operation phase provided in an embodiment of the present invention. Detailed Implementation

[0020] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the present invention. However, those skilled in the art will recognize that the present application may be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted to avoid unnecessary detail that could obscure the description of the present application.

[0021] The technical solution of the present invention will be illustrated below through specific embodiments.

[0022] This invention provides a schematic diagram of a cooling control method for an air source heat pump unit. This method can be executed by an air source heat pump unit, which can be implemented in hardware and / or software and can be configured in an electronic device.

[0023] Figure 1 A schematic diagram of an air source heat pump unit is provided, such as... Figure 1 As shown, the unit includes a compressor 1, a condenser 2, and a condenser fan 3. It also includes an electronic expansion valve 4, a shell-and-tube evaporator 5, and a gas-liquid separator 6. During operation, the compressor 1 compresses the low-temperature, low-pressure gaseous refrigerant into a high-temperature, high-pressure gaseous refrigerant, which is then discharged into the condenser 2. The refrigerant in the condenser 2 condenses into a liquid state under the forced air cooling effect of the condenser fan 3. The liquid refrigerant then enters the shell-and-tube evaporator 5 after being throttled and depressurized by the electronic expansion valve 4. There, it absorbs heat and evaporates into a gaseous state, absorbing heat from the chilled water flowing through the evaporator tubes, thus cooling the chilled water. The evaporated gaseous refrigerant, after being separated from the entrained liquid refrigerant by the gas-liquid separator 6, returns to the compressor 1's suction port, completing the cycle. Through this cycle, the unit achieves continuous cooling of the chilled water.

[0024] In addition, the unit is equipped with multiple temperature and pressure sensors (none of which are located in the...). Figure 1 As shown in the diagram, pressure sensors are installed at both the exhaust and intake ports of compressor 1 to detect the exhaust and intake pressures. A temperature sensor is also installed at the unit's outlet to monitor the outlet water temperature T. cs Temperature sensors are also installed on the exterior of the unit (such as on the shaded side of the outdoor unit casing) to detect the ambient temperature T. sThose skilled in the art will understand that Figure 1 The structure shown is merely an example of the present invention and does not constitute a specific limitation on the unit structure.

[0025] Figure 2 A schematic diagram of a cooling control method for an air source heat pump unit is provided, as shown below. Figure 2 As shown, the method may specifically include the following steps: S201, Obtain ambient temperature T s Real-time outlet water temperature T of the unit cs and the real-time compression ratio A of the compressor s .

[0026] Specifically, ambient temperature T s Outlet water temperature T cs The real-time compression ratio A of the compressor can be obtained through the corresponding temperature sensor. s Calculations show that the exhaust pressure P detected by the pressure sensor at the exhaust port can be collected first. n The inhalation pressure P detected by the pressure sensor at the inhalation port s Based on the exhaust pressure P n and inhalation pressure P s The real-time compression ratio A was calculated. s A s =P n / P s .

[0027] S202, when the ambient temperature T s Less than or equal to the preset low ambient temperature threshold T a At that time, determine the real-time outlet water temperature T. cs Is it greater than the upper limit T of the target outlet water temperature range? max .

[0028] Preset low ambient temperature threshold T a It is a preset temperature value used to determine whether the unit has entered the low ambient temperature cooling condition. Its specific value can be calibrated according to the unit's design operating range, such as 5℃.

[0029] The target outlet water temperature range is from the upper limit T max and lower limit value T min Define, lower limit value T min Target outlet water temperature T n The difference between the first temperature hysteresis ΔT1 and T min =T n -ΔT1; Upper limit value T max The target outlet water temperature T can be determined. n The sum of the second temperature hysteresis ΔT2, i.e., T max =T C+ΔT2. The first and second temperature hysteresis can be the same or different. For example, ΔT1 and ΔT2 are both 2℃. The specific values ​​in this range can be limited according to the actual cooling demand and unit operating parameters.

[0030] When the ambient temperature T s Less than or equal to the preset low ambient temperature threshold T a When the ambient temperature T is high, it indicates that the unit is currently in a low ambient temperature cooling condition and the low ambient temperature cooling control logic of this invention needs to be executed. s Greater than the preset low ambient temperature threshold T a At this time, the unit can operate according to the conventional refrigeration control logic.

[0031] It should be noted that the compressor and condenser fan are off when the unit is first powered on or restarted after a long period of shutdown. When the ambient temperature meets T... s ≤T a And the outlet water temperature T CS Higher than the upper limit of the target outlet water temperature range T max When the unit needs to start cooling, execute S203-S205 to cool down; when the ambient temperature meets T s ≤T a But the outlet water temperature T CS It has not yet exceeded the upper limit value T max If the condition is met, it indicates that cooling is not currently required, and the unit should remain in a stopped state, in which case S206 will be executed.

[0032] S203: Control the compressor and condenser fan to start. After the first preset running time, control the compressor to run at the highest frequency, and adjust the operation according to the real-time compression ratio A. s The condenser fan speed is adjusted according to the relationship between the real-time compression ratio and the boundary values ​​of the preset compression ratio range, thereby controlling the real-time compression ratio A. s Adjust to the preset compression ratio range.

[0033] When the outlet water temperature T CS Higher than the upper limit of the target outlet water temperature range T max This indicates that the current water temperature is too high and the user's cooling demand is too great, requiring the unit to be started for cooling. The controller first controls the compressor and condenser fan to start, thus initiating system operation.

[0034] After the compressor starts, it needs to wait for a first preset time to allow the system to stabilize before controlling the compressor to run at its highest frequency to quickly reduce the outlet water temperature with maximum cooling capacity. The first preset time is the stable operating time after compressor start-up; its specific value can be calibrated according to the compressor type and system characteristics, for example, but not limited to, 1 minute. The highest frequency is the upper limit of the compressor's allowable frequency, corresponding to the outlet water temperature T. CS Higher than the upper limit of the target outlet water temperature range Tmax The temperature range is designed to rapidly cool down the area with maximum cooling capacity.

[0035] During the period when the compressor is operating at its highest frequency, the controller continuously acquires the real-time compression ratio A. s And according to A s The condenser fan speed is adjusted in relation to the preset compression ratio range. The preset compression ratio range is a pre-defined safe compression ratio range, defined by an upper and lower boundary value. Its specific values ​​can be calibrated according to the compressor model characteristics and the low ambient temperature refrigeration operating range (it should be understood that the upper boundary value of the preset compression ratio range is less than the theoretical compression ratio limit of the compressor, and the lower boundary value is greater than the theoretical compression ratio limit of the compressor, to allow for system adjustment margins). When the real-time compression ratio A... s When the compression ratio deviates from this range, the heat dissipation of the condenser is adjusted by regulating the condenser fan speed, thereby restoring the compression ratio to a safe range; when the real-time compression ratio A s When within this range, maintain the current fan speed.

[0036] S204, when the outlet water temperature T cs When the water temperature drops to the target outlet water temperature range, the compressor is controlled to operate in PID control mode at a reduced frequency to maintain the outlet water temperature T. cs Approaching the target outlet water temperature T n Target outlet water temperature T n Within the target outlet water temperature range; during the frequency reduction operation phase, based on the real-time compression ratio A s The condenser fan speed is adjusted according to the relationship between the real-time compression ratio and the boundary values ​​of the preset compression ratio range, thereby controlling the real-time compression ratio A. s Adjust to the preset compression ratio range.

[0037] When the compressor operates at its highest frequency, the refrigerant mass flow rate within the unit increases significantly, thereby enhancing the cooling capacity and increasing the outlet water temperature T. CS Gradually decreasing. When the outlet water temperature T CS Reduced to the target outlet water temperature range (i.e., T) CS When the water temperature is between Tmin and Tmax, it indicates that the water temperature is close to the target outlet water temperature T. C The compressor no longer needs to operate at its highest frequency. At this point, the controller reduces the compressor frequency and uses a PID control mode for closed-loop frequency control.

[0038] The PID control mode dynamically adjusts the compressor's operating frequency based on the deviation between the outlet water temperature and the target outlet water temperature. Specifically, when the outlet water temperature is higher than the target outlet water temperature T... n When the PID output increases, the compressor frequency is moderately increased to increase the cooling capacity; when the outlet water temperature is lower than the target outlet water temperature T...n When the PID output decreases, the compressor frequency is appropriately reduced to decrease the cooling capacity. Through continuous adjustment of the PID, the water output is kept close to the target water temperature T. n This achieves stable temperature control and avoids a sudden and significant drop in compressor frequency, thereby improving the reliability of compressor operation.

[0039] During the frequency reduction operation phase, although the compressor frequency decreases, the unit still needs to maintain the compression ratio within the safe operating range. Therefore, the controller continues to acquire the real-time compression ratio A. s And according to A s The condenser fan speed is adjusted according to the preset compression ratio range. The specific adjustment logic is the same as in S203, and will not be repeated here.

[0040] In this embodiment, the highest frequency and the frequency during reduced-frequency operation represent two different operating states of the same variable frequency compressor, corresponding to different outlet water temperature ranges. The highest frequency is the upper limit of the compressor's allowable frequency, while the frequency during reduced-frequency operation is lower than the highest frequency but higher than the lowest frequency, typically a lower value within the range from the lowest to the highest frequency.

[0041] For example, the compressor operates in a frequency range of 25Hz to 80Hz, with a maximum frequency of 80Hz. During reduced-frequency operation, the frequency is typically within the 25Hz to 80Hz range. When the outlet water temperature T... CS Higher than the upper limit of the target outlet water temperature range T max At this time, the compressor operates at 80Hz to rapidly cool the water at maximum cooling capacity. When the outlet water temperature T... CS After the temperature drops to the target outlet water temperature range, the compressor frequency is controlled in a closed loop using PID regulation mode. The compressor frequency decreases linearly and smoothly without any abrupt or large frequency reduction. The system refrigerant flow, pipeline pressure, and exhaust temperature change gradually, reducing the risk of failures such as insufficient oil return, liquid slugging, and abnormal pipeline vibration and noise caused by sudden frequency drops, thereby improving the unit's operational stability and service life.

[0042] S205, when the outlet water temperature T CS Reduced to the lower limit T of the target outlet water temperature range min When necessary, the compressor and condenser fan will be shut down.

[0043] As the unit continues to operate, when the unit's cooling capacity exceeds the indoor heat dissipation and the compressor frequency cannot be reduced, the outlet water temperature T... CS It decreases further. When the outlet water temperature T CS The lower limit T of the target outlet water temperature range is reached. min When the water temperature reaches a certain level, it indicates that the user's cooling needs have been met, and further cooling is unnecessary. At this point, the controller shuts down the compressor and condenser fan to terminate the cooling process and prevent energy waste caused by over-cooling.

[0044] S206. Control the compressor and condenser fan to remain off.

[0045] In the judgment of S202, if the outlet water temperature T CS Less than or equal to the upper limit T of the target outlet water temperature range max If the current water temperature has not yet reached the conditions for starting the cooling system, then there is no need to start the cooling system. Therefore, the compressor and condenser fan remain off.

[0046] After S206 is completed, return to S202 to continue monitoring the ambient temperature T. s and outlet water temperature T CS The changes can be monitored to ensure a timely response when operating conditions change.

[0047] The air-source heat pump unit cooling control method in this embodiment controls the compressor operating frequency in stages according to the deviation between the outlet water temperature and the target temperature range: when the outlet water temperature is higher than the upper limit of the target temperature range, the compressor operates at a preset maximum frequency, avoiding the PID frequency climb lag problem, significantly improving the cooling capacity, shortening the cooling time, and achieving rapid cooling; at the same time, the condenser fan uses closed-loop speed regulation based on the real-time compression ratio to actively suppress excessive drop in condensing pressure, and keeps the real-time compression ratio A... s The compressor is adjusted to a preset compression ratio range to improve operational reliability. When the outlet water temperature drops to the target temperature range, the compressor operates at a reduced frequency using PID control mode, bringing the outlet water temperature closer to the target temperature. The compressor frequency decreases linearly and smoothly, without abrupt or drastic frequency reductions. This results in gradual changes in system refrigerant flow, pipeline pressure, and exhaust temperature, reducing the risk of malfunctions such as insufficient oil return, liquid slugging, and abnormal pipeline vibration caused by sudden frequency drops. Simultaneously, the condenser fan uses closed-loop speed regulation based on the real-time compression ratio to actively suppress excessive drops in condensing pressure, maintaining the real-time compression ratio A. s By adjusting the compressor to a preset compression ratio range, the stability and service life of the unit are improved. In summary, this invention employs a two-stage coupled control strategy: during the large temperature difference phase, the compressor cools rapidly at its highest frequency, and the condenser fan adjusts its speed according to the compression ratio; during the small temperature difference hysteresis phase, the compressor operates at a reduced frequency using PID control of the water temperature, and the condenser fan maintains compression ratio regulation. This strategy not only improves the cooling response speed and steady-state temperature control accuracy but also stabilizes the system compression ratio throughout the entire process, thus improving the refrigeration cycle conditions.

[0048] In an optional embodiment, such as Figure 3 The diagram shown illustrates the condenser fan adjustment process, based on the real-time compression ratio A. s The condenser fan speed is adjusted according to the relationship between the real-time compression ratio and the boundary values ​​of the preset compression ratio range, thereby controlling the real-time compression ratio A. s Adjusting to a preset compression ratio range, including: S301, Determine the real-time compression ratio A s Whether it is within the preset compression ratio range.

[0049] The preset compression ratio range is defined by the upper limit value A. max and boundary lower limit value A min Define the upper limit value A of the boundary. max The lower boundary limit A corresponds to the critical value where the compression ratio is too high. min This corresponds to the critical value when the compression ratio is relatively low. If A s >A max Then execute S302, if A s <A max Then execute S303, if A min ≤A s ≤A max If so, then S304 will be executed.

[0050] S302. Increase the speed of the condenser fan.

[0051] When A s >A max If the current condenser pressure is relatively high and the compression ratio is too high, the controller will increase the condenser fan speed to enhance the condenser's heat dissipation capacity, thereby reducing the condenser pressure and causing the compression ratio to fall back to the preset range. After the fan speed is increased, the controller will return to step S301 to continue monitoring changes in the compression ratio.

[0052] In this embodiment, the specific step size for increasing and decreasing the fan speed is set according to the specifications of the condenser fan. For example, the step size for both increasing and decreasing the speed can be 50 r / min.

[0053] S303. Reduce the speed of the condenser fan.

[0054] When A s <A max If the current condensing pressure is relatively low and the compression ratio is too small, the controller will reduce the speed of the condenser fan to weaken the condenser's heat dissipation capacity, causing the condensing pressure to rise and thus increasing the compression ratio to the preset range. After the fan speed decreases, the controller will return to step S301 to continue monitoring changes in the compression ratio.

[0055] The specific step size for reducing the fan speed is set according to the specifications of the condenser fan. For example, the step size for speed reduction can be 50 r / min.

[0056] S304. Maintain the condenser fan speed.

[0057] When A min ≤A s ≤A max(Real-time compression ratio A) s When the compression ratio is within the preset range, it indicates that the current compression ratio is within the safe operating range and there is no need to adjust the heat dissipation of the condenser. At this time, the controller controls the condenser fan to maintain the current speed and returns to execute S301 to continue monitoring the compression ratio.

[0058] Through the aforementioned cyclical judgment and adjustment process, the condenser fan speed is continuously adjusted based on real-time compression ratio feedback, thereby maintaining the compression ratio within the preset safe range. Since the compression ratio adjustment and compressor frequency control are independent, fan speed adjustment will not interfere with the compressor's current frequency state. Regardless of whether the compressor is operating at its highest frequency or at a reduced frequency, the fan independently adjusts the condenser's heat dissipation based on compression ratio feedback. Once the compression ratio stabilizes, the compressor frequency does not need to change frequently due to compression ratio fluctuations; it can focus on maintaining the current operating frequency based on the outlet water temperature, thus ensuring the unit maintains a stable operating state while meeting cooling requirements.

[0059] In an optional embodiment, before reducing the speed of the condenser fan, the method further includes: Determine if the condenser fan speed has reached the minimum allowable speed; if so, stop the condenser fan; if not, execute the steps to reduce the condenser fan speed.

[0060] When the real-time compression ratio A s When the condensing pressure is below the lower limit of the preset compression ratio range, it indicates that the current condensing pressure is too low and the compression ratio is too small. It is necessary to reduce the condenser fan speed to decrease the condenser's heat dissipation, thereby increasing the condensing pressure and compression ratio A. s Increase. However, the condenser fan speed cannot be reduced indefinitely; there is a preset minimum allowable speed (e.g., 100 r / min). Below this speed, the fan essentially loses its forced air cooling effect, and further reducing the speed is meaningless and may even cause the fan to stall or the motor to be damaged. Therefore, before each attempt to reduce the fan speed, it is necessary to determine whether the current speed of the condenser fan has reached the minimum allowable speed.

[0061] If the current speed has not reached the minimum allowable speed, the speed of the condenser fan is reduced. Specifically, the fan speed can be reduced by a preset step (e.g., but not limited to 50 r / min), and after a preset adjustment period (e.g., but not limited to 30 s), the real-time compression ratio A is retrieved again. s Continue to determine whether the compression ratio has returned to the preset compression ratio range. If the compression ratio is still below the lower limit, repeat the above determination and deceleration process until the compression ratio returns to the preset compression ratio range, or the fan speed drops to the minimum allowable speed.

[0062] If the current speed has reached the minimum allowable speed, it means that the fan speed reduction measures have been exhausted, and the compression ratio cannot be further increased by continuing to reduce the fan speed. At this time, the controller stops the condenser fan, completely cutting off the forced air cooling of the condenser, allowing the condensing pressure to rise naturally under natural convection conditions, thereby attempting to bring the compression ratio back to the safe range.

[0063] It should be noted that stopping the fan is the boundary treatment method of this invention after the fan adjustment means have been exhausted. Its purpose is to increase the condensing pressure by completely suppressing the heat dissipation of the condenser, thereby restoring the compression ratio. It belongs to the end protection measure of the fan speed regulation logic.

[0064] This embodiment introduces a boundary check mechanism during the cyclic deceleration process, which effectively prevents the fan from continuing to execute the deceleration command when it has already reached the minimum speed, thereby improving the reliability of the control.

[0065] In an optional embodiment, after controlling the condenser fan to stop while the compressor is running at its highest frequency, the following further steps are included: If after the second preset time, the real-time compression ratio A s If the value is still less than the lower limit of the preset compression ratio range, the compressor will be shut down.

[0066] When the condenser fan has stopped (i.e., all fan adjustment methods have been exhausted) and the compressor is operating at its highest frequency (i.e., all frequency adjustment methods have been exhausted), the unit has no other available means to increase the compression ratio. At this point, if after a second preset time (a preset adjustment cycle), the real-time compression ratio A... s If the compression ratio is still below the lower limit of the preset range, it indicates that under the current low ambient temperature refrigeration conditions, the unit cannot restore the compression ratio to the safe range through conventional adjustment methods. The controller shuts down the compressor to protect it from the risks of oil shortage wear and mechanical damage caused by prolonged low compression ratio operation.

[0067] In an optional embodiment, after controlling the condenser fan to stop, the method further includes: In real-time compression ratio A s When the compression ratio exceeds the upper limit of the preset range, the condenser fan will be activated.

[0068] After the condenser fan stops, the forced air cooling of the condenser is cut off, the heat dissipation decreases significantly, the condensing pressure rises accordingly, and the compression ratio gradually increases. When the real-time compression ratio A... s Rise back to the upper limit T of the preset compression ratio range max When this occurs, it indicates that the compression ratio has changed from an excessively low state to an excessively high state. At this point, the controller restarts the condenser fan to restore forced air cooling to the condenser, and the compression ratio A... sIt will return to the preset compression ratio range to prevent the compression ratio from continuing to rise. When the condenser fan restarts, it can resume operation at a preset initial speed of 300 r / min.

[0069] Through the above processing, the condenser fan stops when the compression ratio is too low to suppress heat dissipation and increase the compression ratio, and restarts when the compression ratio recovers to above the safe upper limit to restore heat dissipation and prevent the compression ratio from becoming too high, thus forming a complete hysteresis control. Furthermore, the compression ratio range difference provides a buffer for the unit, avoiding frequent start-stop cycles of the fan near the critical point and improving control stability.

[0070] In an optional embodiment, during the frequency reduction operation phase, after controlling the condenser fan to stop, the following further steps are taken: If after the second preset time, the real-time compression ratio A s If the value is still less than the lower limit of the preset compression ratio range, then the compressor is controlled to operate at a preset frequency ramp-up rate to increase the real-time compression ratio A. s It is within the preset compression ratio range.

[0071] When the condenser fan has stopped (i.e., all fan adjustment methods have been exhausted) and the compressor is in the frequency reduction operation phase (i.e., the compressor frequency has not reached its upper limit and there is still room for adjustment), if the real-time compression ratio A is after the second preset time... s If the value is still below the lower limit of the preset compression ratio range, it indicates that simply stopping the fan is insufficient to restore the compression ratio to the safe range. At this point, the controller controls the compressor to operate at a preset frequency ramp-up rate (e.g., but not limited to 1Hz / s), increasing the compressor speed to raise the exhaust pressure and thus the compression ratio, attempting to bring the real-time compression ratio A to within the safe range. s It returns to the preset compression ratio range.

[0072] In this embodiment, after the fan adjustment means are exhausted, the frequency adjustment space when the compressor is still in the frequency reduction stage is utilized to further increase the exhaust pressure by increasing the frequency, providing a supplementary means for the compression ratio recovery. This works in synergy with the heat dissipation suppression effect of the fan shutdown, minimizing the risk of the system triggering shutdown when there is still adjustment margin, and improving the operational reliability under low ambient temperature refrigeration conditions.

[0073] In an optional embodiment, after controlling the compressor to operate at a preset frequency ramp-up rate, the following steps are included: If after the third preset time, the real-time compression ratio A s If the value is still less than the lower limit of the preset compression ratio range, the compressor will be shut down.

[0074] After the compressor's frequency is increased, the discharge pressure and compression ratio will not rise instantly; a certain amount of time is needed for the unit to establish a new pressure balance. If, after the third preset time, the real-time compression ratio A... sIf the compression ratio is still below the lower limit of the preset range, it means that even if the compressor frequency has been increased, it is still unable to bring the compression ratio back to the safe range. At this point, the compressor frequency has been increased, the fan has been stopped, and all available adjustment methods in the system have been exhausted. The controller then shuts down the compressor to prevent it from running continuously at a low compression ratio, which could damage the equipment.

[0075] It should be noted that the first preset time, the second preset time, and the third preset time in this invention are respectively applied to the start-up phase (of the compressor and the fan), the fan shutdown phase, and the compressor frequency increase phase. The specific values ​​can be independently calibrated according to different unit types and operating conditions, and this invention does not impose specific limitations on them.

[0076] In an optional embodiment, such as Figure 1 As shown, the unit also includes a solenoid two-way valve 7, a capillary assembly 8, and an oil separator 9 disposed between the discharge port of the compressor 1 and the condenser 2. The oil separator 9 (including its oil return port), the solenoid two-way valve 7, the capillary assembly 8, and the suction port of the compressor 1 are connected in sequence via pipelines. The oil separator 9 is used to separate the lubricating oil carried in the discharge of the compressor 1 and collect it at its bottom. The solenoid two-way valve 7 is used to control the opening and closing of the oil return pipeline. The capillary assembly 8 is used to throttle and reduce the pressure of the lubricating oil in the oil return pipeline, so that it can smoothly enter the suction side of the compressor 1.

[0077] During the frequency reduction operation phase, the control methods also include: When the real-time compression ratio A s When the compressor is in the preset compression ratio range, the operating frequency of the compressor is obtained; the target oil return cycle is determined based on the operating frequency; when the cumulative operating time of the compressor reaches the target oil return cycle, the solenoid two-way valve is opened to perform the oil return operation.

[0078] The process of determining the target oil return cycle based on the operating frequency includes: when the operating frequency is less than the preset frequency, the target oil return cycle is determined as the first oil return cycle; when the operating frequency is greater than or equal to the preset frequency, the target oil return cycle is determined as the second oil return cycle; the duration of the first oil return cycle is less than the duration of the second oil return cycle.

[0079] The preset frequency is the upper limit of the compressor's low-frequency operating range, serving as the boundary between low-frequency and medium-to-high-frequency operation. When the operating frequency is lower than this preset frequency, the compressor operates in the low-frequency range, resulting in a shorter oil return cycle. When the operating frequency is greater than or equal to this preset frequency, the compressor operates in the non-low-frequency range. The preset frequency can be set according to actual needs; optionally, it is 40Hz to 50Hz, preferably 40Hz.

[0080] The operating frequency of the compressor directly affects the refrigerant flow rate. When the compressor is in the low-frequency operating range, the refrigerant flow rate is slow, the lubricating oil circulation power is insufficient, and the oil return is more difficult. Therefore, the target oil return cycle is set to a shorter first oil return cycle (e.g., 60 minutes) to perform the oil return operation more frequently. When the compressor is in the non-low-frequency operating range, the refrigerant flow rate is faster, the lubricating oil itself has a strong oil-carrying capacity, and the oil return is less difficult. Therefore, the target oil return cycle is set to a longer second oil return cycle (e.g., 120 minutes).

[0081] like Figure 1 As shown, when the cumulative running time of compressor 1 reaches the target oil return cycle, the solenoid two-way valve 7 is opened to perform the oil return operation. Specifically, the cumulative running time of compressor 1 is reset to zero and restarted after the last oil return operation. When the cumulative time reaches the target oil return cycle, the solenoid two-way valve 7 is opened, and the lubricating oil accumulated at the bottom of the oil separator 9 flows back to the suction port of compressor 1 through the solenoid two-way valve 7 and the capillary tube assembly 8 under the pressure difference between the discharge pressure and the suction pressure, thus completing the oil return operation. After the oil return operation is completed, the solenoid two-way valve 7 is closed, the cumulative running time of compressor 1 is reset to zero, and the timing restarts to enter the next oil return cycle. By periodically performing the above oil return operation, the circulation of lubricating oil in compressor 1 during the frequency reduction operation phase is ensured, avoiding oil shortage in compressor 1 due to insufficient oil return.

[0082] In an optional embodiment, during the return oil operation, the method further includes: When the operating frequency is lower than the preset frequency, the compressor is controlled to increase its frequency until the oil return ends. The preset frequency is the upper limit of the low frequency range.

[0083] When the compressor's current operating frequency is lower than the preset frequency, it indicates that the compressor is operating at a low frequency. The refrigerant flow rate within the unit is slow, and simply opening the solenoid two-way valve to allow the lubricating oil to flow back under pressure differential may not be sufficient to fully remove the lubricating oil deposited on the inner walls of the pipes. In this case, while performing the oil return operation, the controller simultaneously controls the compressor to operate at a higher frequency, increasing the refrigerant flow rate. This high-speed refrigerant flow flushes away the lubricating oil deposited on the inner walls of the pipes, carrying the lubricating oil back to the compressor, thus enhancing the oil return effect. After the oil return operation is completed, the solenoid two-way valve closes, and the compressor returns to its operating frequency before the oil return (or is re-determined by PID control). Through this process, the oil return effect of the compressor under low-frequency operation is significantly improved, avoiding the problem of poor oil return caused by excessively low refrigerant flow rate.

[0084] Optionally, a temperature sensor is also installed in the compressor's crankcase to detect the crankcase oil temperature T. γ s, such as Figure 1As shown, a crankcase electric heating module 10 is also provided on the outer wall of the compressor housing 1 for heating the lubricating oil in the crankcase. When the crankcase oil temperature T... γ s preset safe oil temperature threshold T γ At that time, the crankcase electric heating module 12 is activated to heat the oil temperature to T. γ +10℃ to T γ Within a temperature range of +15℃, the viscosity of the lubricating oil is reduced and its fluidity is restored through heat treatment, ensuring that it can circulate normally within the system and avoiding the risk of compressor oil shortage caused by lubricating oil deposition due to low temperature.

[0085] To clearly illustrate the air source heat pump unit cooling control method of the present invention, this control method can be specifically divided into a high-frequency operation stage and a low-frequency operation stage. (Refer to...) Figure 4 The diagram illustrates a high-frequency operation phase provided by an embodiment of the present invention, specifically including the following steps: A0. Power on.

[0086] A1. Determine the ambient temperature T s Is it less than the preset low ambient temperature threshold T? a .

[0087] If not, execute A2; if yes, execute A3.

[0088] A2. Conventional refrigeration control.

[0089] A3. Determine the outlet water temperature T cs Is it greater than the upper limit T of the target outlet water temperature range? max .

[0090] If yes, execute A5; otherwise, execute A4.

[0091] A4. Keep the compressor and condenser fan off.

[0092] That is, to maintain the original state.

[0093] A5. Cooling start, the compressor runs at the highest frequency.

[0094] The cooling start-up includes starting the compressor and fan to enter the high-frequency operation phase (A6-A12).

[0095] A6. Determine T min <T cs <T max Whether it is valid or not.

[0096] T min T max These are the lower and upper limits of the target outlet water temperature range, respectively.

[0097] If not, execute A7; if yes, end the high-frequency operation phase and execute B0 to enter the low-frequency operation phase.

[0098] A7. Determine T cs >T max Whether it is valid or not.

[0099] If not, execute A8; if yes, execute A9.

[0100] A8. Control the compressor to stop.

[0101] A9. Calculate the compression ratio A s .

[0102] If A s >A max Execute A10, if A min ≤A s ≤A max Execute A11, if A s <A min Execute A12.

[0103] A10, increase the fan speed, then return to A6.

[0104] A11. Maintain the fan speed, then return to A6.

[0105] A12. Determine if the fan speed is at its minimum speed.

[0106] If not, execute A13; if yes, execute A14.

[0107] A13. Reduce the fan speed, then return to A6.

[0108] A14, the fan stops, then return to A6.

[0109] It should be noted that the compression ratio A will still be acquired in real time after the fan has been shut down for a period of time. s If the compression ratio A s Still less than A min Then the compressor will be stopped; if the compression ratio A s Greater than A max If so, the fan will restart.

[0110] Reference Figure 5 The diagram illustrates a frequency reduction operation phase provided by an embodiment of the present invention, specifically including the following steps: B0. The compressor has entered the frequency reduction operation stage.

[0111] B1. Determine T cs <T min Whether it is valid or not.

[0112] If not, execute B3; if yes, end the frequency reduction phase and execute B2.

[0113] B2. Control the compressor to stop.

[0114] B3. Calculate the compression ratio A s .

[0115] If A s >A max Execute B4, if A min ≤A s ≤A max Execute B5, if A s <A min Execute B6.

[0116] B4. Increase the fan speed, then return to B1.

[0117] B5. Maintain the fan speed, then return to B1.

[0118] While maintaining the fan speed, the oil return cycle can also be determined and oil return control can be performed based on the operating frequency.

[0119] B6. Determine if the fan speed is at its minimum speed.

[0120] If not, proceed to B7; if yes, proceed to B8.

[0121] B7. Reduce the fan speed, then return to B1.

[0122] B8. The fan stops, then return to B1.

[0123] It should be noted that the compression ratio A is obtained in real time after the fan has been shut down for a period of time. s If the compression ratio A s <A min Then, the compressor is controlled to increase its frequency at a preset rate, and the compression ratio A is obtained again after the unit is running stably. s ; If the compression ratio A s >A max If so, the fan will be restarted; If the compression ratio A s <A min If so, the compressor will be shut down.

[0124] As can be seen from the above steps, this scheme divides the compressor operation into a high-frequency operation stage and a low-frequency operation stage based on the deviation between the outlet water temperature and the target temperature range. In the high-frequency stage, the compressor rapidly cools down at the highest frequency. In the low-frequency operation stage, a PID control mode is used to reduce the frequency and stabilize the outlet water temperature close to the target temperature. In each stage, the fan speed is dynamically adjusted based on the boundary relationship between the real-time compression ratio and the preset range to maintain the compression ratio within a safe range. When the fan speed drops to the minimum and still cannot restore the compression ratio, the fan is stopped as a final adjustment measure. The fan is restarted when the compression ratio rises above the safe upper limit, forming a complete hysteresis control system. This avoids frequent start-stop cycles of the fan near the critical point and improves the reliability of the unit operation.

[0125] It should be noted that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0126] Corresponding to the air source heat pump unit control method in this invention, this invention also provides an air source heat pump unit. Figure 1 A schematic diagram of an air source heat pump unit, such as Figure 1 As shown, the unit includes a controller ( Figure 1 (Not shown) and a compressor 1, a condenser 2 and a condenser fan 3 connected to a respective controller, the controller being used to execute the refrigeration control method of each air source heat pump unit as described in the embodiments of the present invention.

[0127] The present invention provides an air source heat pump unit, which can realize the various steps in the aforementioned air source heat pump unit refrigeration control method embodiments.

[0128] It should be noted that the module division in the various air source heat pump units provided in the above embodiments is illustrative and only represents a logical functional division. In actual implementation, other division methods may also be used. Furthermore, the functional modules in the various embodiments of this invention can be integrated into a single processor, exist as separate physical entities, or be integrated into a single module. The integrated modules described above can be implemented in hardware or as software functional modules.

[0129] If the integrated module is implemented as a software functional module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the technical solution of the embodiments of the present invention can be embodied in the form of a computer program product, which is stored in a computer storage medium and includes several instructions to cause an electronic device or processor to execute all or part of the steps of the methods in the various embodiments of the present invention. The aforementioned computer storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0130] Furthermore, the air source heat pump unit and the air source heat pump unit cooling control method embodiment provided in the above embodiments belong to the same concept, and their specific implementation process can be found in the method embodiment, which will not be repeated here.

[0131] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A cooling control method for an air source heat pump unit, characterized in that, The unit includes a compressor, a condenser, and a condenser fan; the method includes: Obtain ambient temperature T s Real-time outlet water temperature T of the unit cs and the real-time compression ratio A of the compressor s ; When the ambient temperature T s Less than or equal to the preset low ambient temperature threshold T a At that time, determine the real-time outlet water temperature T. cs Is it greater than the upper limit T of the target outlet water temperature range? max ; If so, control the compressor and condenser fan to start, and after the first preset running time, control the compressor to run at the highest frequency, and adjust according to the real-time compression ratio A. s The condenser fan speed is adjusted according to the relationship between the real-time compression ratio and the boundary values ​​of the preset compression ratio range, thereby controlling the real-time compression ratio A. s Adjust to within the preset compression ratio range; When the outlet water temperature T cs When the water temperature drops to the target outlet water temperature range, the compressor is controlled to operate in PID control mode with reduced frequency to maintain the outlet water temperature T. cs Approaching the target outlet water temperature T n The target effluent temperature T n Located within the target outlet water temperature range, during the frequency reduction operation phase, based on the real-time compression ratio A s The condenser fan speed is adjusted according to the relationship between the real-time compression ratio and the boundary values ​​of the preset compression ratio range, thereby controlling the real-time compression ratio A. s Adjust to within the preset compression ratio range; When the outlet water temperature T cs The temperature drops to the lower limit T of the target effluent temperature range. min When necessary, control the compressor and condenser fan to stop; If not, keep the compressor and condenser fan off, and return to the previous step to determine the real-time outlet water temperature T. cs Is it greater than the upper limit T of the target outlet water temperature range? max The steps.

2. The method according to claim 1, characterized in that, The real-time compression ratio A is mentioned s The condenser fan speed is adjusted according to the relationship between the real-time compression ratio and the boundary values ​​of the preset compression ratio range, thereby controlling the real-time compression ratio A. s Adjusting to a preset compression ratio range, including: Determine the real-time compression ratio A s Is it within the preset compression ratio range? When the real-time compression ratio A s When the compression ratio exceeds the upper limit of the preset compression ratio range, increase the condenser fan speed and return to the previous step to determine the real-time compression ratio A. s The step of determining whether it is within the preset compression ratio range; When the real-time compression ratio A s When the compression ratio is less than the lower limit of the preset compression ratio range, reduce the speed of the condenser fan and return to the execution state to determine the real-time compression ratio A. s The step of determining whether it is within the preset compression ratio range; When the real-time compression ratio A s When the compression ratio is within the preset range, maintain the condenser fan speed and return to the previous step to determine the real-time compression ratio A. s The step of determining whether it is within the preset compression ratio range.

3. The method according to claim 2, characterized in that, Before reducing the speed of the condenser fan, the method further includes: Determine if the condenser fan speed has reached the minimum allowable speed; If so, shut down the condenser fan; If not, proceed with the step of reducing the speed of the condenser fan.

4. The method according to claim 3, characterized in that, After the condenser fan is stopped, the following is also included: In real-time compression ratio A s When the compression ratio exceeds the upper limit of the preset range, the condenser fan will be activated.

5. The method according to claim 3, characterized in that, During the frequency reduction operation phase, after the control condenser fan is stopped, the following is also included: If after the second preset time, the real-time compression ratio A s If the value is still less than the lower limit of the preset compression ratio range, then the compressor is controlled to operate at a preset frequency ramp-up rate to increase the real-time compression ratio A. s It is within the preset compression ratio range.

6. The method according to claim 5, characterized in that, After controlling the compressor to operate at a preset frequency ramp-up rate, the following steps are included: If after the third preset time, the real-time compression ratio A s If the value is still less than the lower limit of the preset compression ratio range, the compressor will be shut down.

7. The method according to claim 1, characterized in that, The unit also includes a solenoid two-way valve, a capillary assembly, and an oil separator located between the compressor's exhaust port and the condenser. The oil separator, solenoid two-way valve, capillary assembly, and compressor's intake port are connected in sequence via pipelines. During the frequency reduction operation phase, the method further includes: When the real-time compression ratio A s When the compressor is within a preset compression ratio range, its operating frequency is obtained. The target oil return cycle is determined based on the operating frequency. When the compressor's cumulative running time reaches the target oil return cycle, the solenoid two-way valve is opened to perform the oil return operation.

8. The method according to claim 7, characterized in that, Determining the target oil return cycle based on the operating frequency includes: When the operating frequency is less than the preset frequency, the target oil return cycle is determined to be the first oil return cycle; the preset frequency is the upper limit of the compressor's low-frequency operating range. When the operating frequency is greater than or equal to the preset frequency, the target oil return cycle is determined to be the second oil return cycle; The duration of the first oil return cycle is shorter than the duration of the second oil return cycle.

9. The method according to claim 7, characterized in that, When performing the return oil operation, it also includes: When the operating frequency is less than the preset frequency, the compressor is controlled to increase its frequency until the oil return ends. The preset frequency is the upper limit of the low frequency range.

10. An air source heat pump unit, characterized in that, The unit includes a controller and a compressor, a condenser, and a condenser fan connected to the controller, the controller being used to perform the air source heat pump unit refrigeration control method as described in any one of claims 1-9.

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