Start control method and device after low-voltage protection, equipment and storage medium

Abstract

The invention discloses a starting control method and device after low-pressure protection, equipment and a storage medium, and is used for a heat pump unit, and the starting control method is characterized in that the method comprises the steps that after the heat pump unit triggers low-pressure protection, the current environment temperature and the low-pressure pressure of a system are detected; when the environment temperature is smaller than a first threshold value, entering a parameter compensation stage, and in the parameter compensation stage, determining a target adjustment parameter according to the environment temperature, the low pressure and a preset contrast relation; and the opening degree of a main valve and the rotating speed of a draught fan are adjusted according to the target adjusting parameters, and after adjustment is completed, a compressor is controlled to run and restart according to the preset running frequency. Most temporary low-pressure problems caused by severe working conditions can be automatically solved, non-reason shutdown is reduced, and continuous heating / cooling is guaranteed.

Description

Technical Field

[0001] This application relates to the technical field of heat pump systems, and in particular to a start-up control method, device, equipment, and storage medium after low-pressure protection. Background Technology

[0002] The stable operation of a heat pump unit relies on the phase change cycle of the refrigerant to transfer heat. The pressure balance and gas-liquid ratio of the refrigerant within the system are crucial prerequisites for ensuring cycle efficiency and unit safety. In practical applications, the unit inevitably faces low-temperature and ultra-low-temperature environments, and there are scenarios involving restarting after long-term shutdowns. In these situations, the system is highly susceptible to abnormal pressure drops, triggering the low-pressure protection mechanism. Specifically, in low-temperature and ultra-low-temperature environments, when the unit has not been started for a long time, the refrigerant temperature in the system decreases as the ambient temperature drops, directly causing a decrease in the initial system pressure. At the same time, low temperatures cause a large amount of refrigerant to liquefy and flow back to the condenser. The liquid refrigerant occupies the effective internal volume of the condenser, resulting in a significant reduction in the amount of gaseous refrigerant participating in the system's circulation, further exacerbating the downward trend in system pressure. On the other hand, low temperatures significantly inhibit the evaporation process of refrigerant in the evaporator, resulting in insufficient gaseous refrigerant supply to the compressor's suction side, making it difficult to maintain normal suction pressure. In addition, low temperatures also cause the viscosity of the compressor oil to increase, and the miscibility between the refrigerant and the lubricating oil to change, resulting in increased compressor starting resistance and an inability to quickly establish a stable suction pressure. The combined effect of these multiple factors will ultimately trigger the system's low-pressure protection action.

[0003] Low-pressure protection is a critical safety mechanism for heat pump systems. Its purpose is to prevent the system from operating under excessively low pressure conditions, avoiding irreversible damage to the compressor due to insufficient refrigerant or lubrication failure, and mitigating the risk of a sharp decline in heating or cooling performance. However, existing low-pressure protection mechanisms are mostly passively triggered. Once triggered, the unit typically requires manual intervention to reset, or must wait for the ambient temperature to rise and the refrigerant to reheat and vaporize naturally before resuming operation. This severely restricts the continuous operation capability and emergency start-up efficiency of heat pump units in low and ultra-low temperature environments, and significantly reduces the user experience. This problem is particularly pronounced in scenarios with rigid requirements for continuous operation, such as low-temperature cold chain storage, ultra-low temperature experimental equipment, and refrigeration units for polar conditions, becoming a key technical bottleneck hindering the widespread application of heat pump systems in low and ultra-low temperature fields. Summary of the Invention

[0004] The purpose of this invention is to provide a startup control method, apparatus, device, and storage medium after low-voltage protection, which can solve the above-mentioned problems existing in the prior art.

[0005] To achieve the above objectives, this application adopts the following technical solution: On the one hand, a startup control method after low-pressure protection is provided for a heat pump unit, the method comprising: after the heat pump unit triggers low-pressure protection, detecting the ambient temperature and the low-pressure of the system; When the ambient temperature is less than the first threshold, the parameter compensation stage is entered, and the target adjustment parameter is determined according to the ambient temperature, the low pressure, and the preset comparison relationship. The main valve opening and fan speed are adjusted according to the target adjustment parameters, and the compressor is restarted according to the preset operating frequency.

[0006] Furthermore, the opening degree of the main valve is adjusted in the following manner: The compensation opening degree is determined based on the ambient temperature and the preset comparison relationship; The target opening degree is determined based on the initial opening degree of the main valve and the compensation opening degree. The main valve opening is adjusted according to the target opening to increase the refrigerant circulation volume.

[0007] Furthermore, it also includes: Before the heat pump unit triggers low-pressure protection, the initial opening degree of the main valve is obtained, and the compensation opening degree is added to the initial opening degree of the main valve to determine the target opening degree of the main valve.

[0008] Furthermore, the fan speed is adjusted in the following manner: The target rotational speed is determined based on the low-pressure and the preset comparison relationship; Adjust the fan speed according to the target speed.

[0009] Furthermore, in the preset comparison relationship, for any two pressure values ​​P1 and P2 corresponding to rotational speeds n1 and n2, when P1 > P2, n1 < n2.

[0010] Furthermore, the preset operating frequency is the minimum operating frequency of the compressor.

[0011] Furthermore, when the ambient temperature is greater than or equal to the first threshold, the compressor is controlled to restart directly, and when the low-pressure protection is triggered continuously for a preset number of times, the compressor is controlled to stop.

[0012] On the other hand, a start-up control device after low-voltage protection is also provided, comprising: The detection module is used to detect the ambient temperature and the low pressure of the system after the heat pump unit triggers the low pressure protection. The target determination module is used to enter the parameter compensation stage when the ambient temperature is less than a first threshold, and to determine the target adjustment parameters based on the ambient temperature, the low pressure, and a preset comparison relationship. The control module is used to adjust the main valve opening and fan speed according to the target adjustment parameters, and to control the compressor to start running and restart according to the preset operating frequency.

[0013] On the other hand, a start-up control device after low-voltage protection is also provided, including: Memory and one or more processors; The memory is used to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors perform the method described above.

[0014] On the other hand, a storage medium for storing computer-executable instructions is also provided, which, when executed by a processor, are used to perform the methods described above.

[0015] The beneficial effects of this application are as follows: After the heat pump unit triggers low-pressure protection, it first detects the current ambient temperature and the system low-pressure. When it determines that the ambient temperature is less than the first threshold, i.e., it is in a low-temperature operating condition, it enters the parameter compensation stage. Based on the ambient temperature, low-pressure and preset comparison relationship, the target adjustment parameters are determined, and the main valve opening and fan speed are adjusted in a targeted manner. This promotes the participation of the liquid refrigerant retained in the condenser in circulation, increases the amount of gaseous refrigerant in the system, enhances the heat exchange efficiency of the evaporator, ensures the supply of gaseous refrigerant on the suction side of the compressor, and alleviates the problem of insufficient low-pressure in the system. Then, the compressor is restarted according to the preset operating frequency to adapt to the operating conditions of high compressor oil viscosity and high starting resistance at low temperatures, avoids secondary triggering of protection or damage to the compressor, and finally realizes the rapid restoration of thermodynamic balance of the system without manual intervention or waiting for the ambient temperature to rise. This effectively improves the continuous operation capability and emergency restart efficiency of the heat pump unit under low-temperature / ultra-low-temperature conditions, and solves the problems of unit operation interruption and low starting efficiency after low-pressure protection in the prior art. Attached Figure Description

[0016] The present application will now be described in further detail with reference to the accompanying drawings and embodiments.

[0017] Figure 1 This is a flowchart of the startup control method after low-voltage protection as described in the embodiments of this application; Figure 2 This is a logical schematic diagram of the startup control method after low-voltage protection as described in the embodiments of this application; Figure 3 This is a schematic diagram of the start-up control device after low-voltage protection as described in the embodiments of this application; Figure 4 This is a schematic diagram of the start-up control device after low-voltage protection as described in the embodiments of this application. Detailed Implementation

[0018] To make the technical problems solved by this application, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of the embodiments of this application are further described in detail below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] In the description of this application, unless otherwise expressly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0020] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0021] like Figure 1 and Figure 2 As shown, this embodiment provides a start-up control method after low-pressure protection, used for heat pump units. The method includes: Step 101: After the heat pump unit triggers low-pressure protection, detect the current ambient temperature and the system's low-pressure. Step 102: When the ambient temperature is less than the first threshold, the parameter compensation stage is entered. In the parameter compensation stage, the target adjustment parameter is determined according to the ambient temperature, the low pressure, and the preset comparison relationship. Step 103: Adjust the main valve opening and fan speed according to the target adjustment parameters. After adjustment, control the compressor to restart according to the preset operating frequency.

[0022] Based on the above solution, a closed-loop control logic of precise operating condition identification, proactive parameter compensation, and orderly restart operation replaces the passive waiting or manual intervention mode of existing technologies. This addresses the system imbalance issue triggered by low-pressure protection in low / ultra-low temperature environments, achieving targeted parameter adjustment and rapid, stable system restart, as detailed below: When the heat pump unit triggers low-pressure protection, the system first initiates a core operating condition detection step, accurately collecting two key parameters: the current ambient temperature and the system low-pressure. This detection step can directly pinpoint the core scenario causing low-pressure protection in the background technology, namely, a low-temperature / ultra-low-temperature environment (determined by comparing the ambient temperature with a first threshold). Simultaneously, the low-pressure feedback clarifies the current pressure imbalance of the system, providing accurate data support for subsequent adjustments and avoiding blind adjustments that could lead to restart failures or secondary protection triggers.

[0023] When the ambient temperature is confirmed to be below the first threshold (i.e., under low / ultra-low temperature operating conditions), the system enters the parameter compensation phase. This phase, based on a pre-defined reference relationship, integrates ambient temperature and low-pressure data to determine the target adjustment parameters. This design enables condition-appropriate matching of the adjustment parameters. Addressing core issues in the background technology, such as excessive refrigerant liquefaction and reflux, insufficient evaporation in the evaporator, and a lack of gaseous refrigerant in the system due to low temperatures, the target adjustment parameters, through targeted optimization of the main valve opening and fan speed, solve the problem of insufficient system pressure recovery from two key dimensions: Firstly, targeted adjustment of the main valve opening alters the refrigerant's flow path and circulation volume, promoting the orderly reflux of liquid refrigerant retained in the condenser and its participation in circulation, increasing the proportion of gaseous refrigerant in the system, and gradually alleviating the insufficient low-pressure state; secondly, adaptive adjustment of the fan speed optimizes the evaporator's heat exchange efficiency, enhances the refrigerant evaporation process under low-temperature conditions, provides sufficient gaseous refrigerant replenishment to the compressor's suction side, and solves the problem of insufficient evaporation at low temperatures, making it difficult to maintain suction pressure.

[0024] Once the main valve opening and fan speed are adjusted to the target parameters, the system restarts the compressor at a preset operating frequency. This preset operating frequency avoids the problems of increased compressor oil viscosity and starting resistance at low temperatures, ensuring the compressor starts with a load suitable for the current operating conditions. This prevents excessive starting load from triggering low-pressure protection again or causing compressor damage. The entire control process actively intervenes in the system's core operating parameters, specifically addressing the core pain points of system parameter imbalance and pressure recovery difficulties after low-pressure protection in low / ultra-low temperature environments. Without manual intervention or prolonged waiting for ambient temperature to rise, the system can quickly restore thermodynamic balance, effectively improving the unit's continuous operation capability and emergency restart efficiency under low / ultra-low temperature conditions. This fundamentally solves the problems of unit operation interruption, low starting efficiency, and poor user experience after low-pressure protection in existing technologies, breaking through the technical bottleneck restricting the widespread application of units in low-temperature fields.

[0025] The compensation opening degree is determined based on the ambient temperature and a preset control relationship. The target opening degree is determined based on the initial opening degree of the main valve and the compensation opening degree. The main valve opening is adjusted according to the target opening to increase the refrigerant circulation volume.

[0026] Based on the conventional control logic that the lower the ambient temperature during stable operation of low-temperature heating, the main valve opening is smaller. By using a main valve initial opening compensation strategy that is differentiated according to operating conditions, it can accurately adapt to the special operating conditions required during the start-up phase after low-pressure protection. This avoids low-pressure faults during the start-up phase and does not interfere with the conventional superheat control after stable operation, thus achieving a smooth transition between start-up and stable operation.

[0027] Specifically, the core control objective for stable operation of low-temperature heating is to ensure superheat: when the ambient temperature is extremely low, the evaporator (outdoor heat exchanger) significantly reduces its ability to absorb heat from the air. If the main valve opening is too large, a large amount of liquid refrigerant will flow into the evaporator and cannot evaporate fully, which can easily lead to liquid return, i.e., the liquid refrigerant directly enters the compressor, causing liquid slugging damage to the compressor. Therefore, the conventional control logic will reduce the main valve opening as the ambient temperature decreases, reducing the refrigerant flow to ensure that the refrigerant evaporates completely in the evaporator and reaches the target superheat. For example, in a specific system, when the ambient temperature drops from 10°C to -10°C, the optimal electronic expansion valve opening needs to be reduced from about 62.1% to 47.9%, which is a quantitative manifestation of this control logic.

[0028] This solution addresses the special transitional phase of startup after low-pressure protection: at this time, the system has already triggered low-pressure protection due to low temperature. If the conventional small opening value is used for startup directly, it will lead to insufficient refrigerant circulation, further exacerbating the low-pressure state and failing the startup condition test, thus triggering a low-pressure fault again. Therefore, by compensating for the initial opening, the limitations of conventional small opening startup are overcome. The core logic is: during the startup transition phase (from shutdown to stable operation), the compensation opening is determined based on the current ambient temperature and the preset reference relationship. This compensation opening is coupled with the initial opening of the main valve (the initial opening under conventional control logic) to calculate the target opening. By increasing the initial opening of the main valve, the refrigerant circulation is increased. Sufficient refrigerant circulation can accelerate the return and evaporation of liquid refrigerant in the condenser, quickly replenish the gaseous refrigerant on the compressor suction side, avoid triggering low-pressure protection again during startup, and ensure that the unit can smoothly enter the transitional condition before stable operation.

[0029] Meanwhile, this compensation strategy has clear phased characteristics and compatibility: the initial opening compensation only applies to the start-up transition phase. Once the unit starts up smoothly and reaches a stable operating state, the system will automatically switch to the preset conventional control logic, adjusting the main valve opening to a normal level based on core parameters such as superheat. This means returning to the optimal state where the opening is smaller as the ambient temperature decreases, ensuring compressor safety and system efficiency during stable operation. Furthermore, the compensation opening setting follows the rule that the compensation amount is smaller as the ambient temperature decreases, which aligns with the core requirements of conventional control logic. At lower ambient temperatures, the conventional opening is already at a relatively small level. Excessive compensation to increase the opening may approach the liquid return risk threshold. Therefore, appropriately reducing the compensation amount can solve the low-pressure start-up problem while minimizing the risk of liquid return during the transition phase, achieving the dual goals of "preventing low pressure during start-up" and "preventing liquid return during stability."

[0030] By optimizing and precisely compensating for the conventional control logic in stages, the pain point of difficulty in starting up after low-pressure protection under low-temperature conditions is solved without compromising the core control objectives during stable operation. This achieves seamless adaptation between special transitional conditions and conventional stable conditions, improving the unit's start-up reliability and operational safety in low-temperature environments.

[0031] Specifically, before the heat pump unit triggers low-pressure protection, the initial opening degree of the main valve is obtained, and the compensation opening degree is added to the initial opening degree of the main valve to determine the target opening degree of the main valve. Through the quantitative control logic of pre-stored initial opening degree + step-by-step compensation, the operating condition adaptability optimization of the main valve opening degree is accurately realized. While solving the problem of low pressure after low-pressure protection under low-temperature conditions, the risk of liquid return is strictly avoided, ensuring a smooth transition between start-up and stable operation.

[0032] Specifically, its core logic can be broken down into two key stages: initial opening degree pre-storage and stepped compensation. The first stage is the initial opening degree pre-storage: before the heat pump unit triggers low-pressure protection, the system records the current operating opening degree of the main valve in real time and stores it as the initial opening degree. This initial opening degree is the optimal opening degree for the unit's normal stable operation under the current ambient temperature (the core objective is to ensure superheat). Using this as the compensation benchmark ensures that subsequent opening degree adjustments always revolve around the normal optimal operating conditions, avoiding operational disturbances caused by deviations in the compensation direction.

[0033] Secondly, there is the stepped compensation stage. The system adopts a quantitative compensation method in units of "steps (N)," and sets differentiated compensation step sizes according to the ambient temperature. Specifically, it follows the core rule that the lower the ambient temperature, the smaller the compensation step size: 100N compensation at 10℃, 80N compensation at -2℃, 60N compensation at -15℃, 40N compensation at -22℃, and a fixed compensation of 30N for further decreases in ambient temperature. This stepped compensation rule is deeply adapted to the normal operating logic of low-temperature heating. In low-temperature environments, the evaporator's heat absorption capacity decreases, and the main valve opening needs to be reduced during normal operation to avoid liquid return. If the compensation step size is excessively increased during the start-up phase after low-pressure protection, the main valve opening will exceed the safety threshold, causing a large amount of liquid refrigerant to flow into the evaporator and fail to evaporate fully, leading to the risk of liquid return. Therefore, by gradually reducing the compensation step size as the ambient temperature decreases, a precise balance can be achieved between increasing the refrigerant circulation volume to address low startup pressure and controlling the opening to ensure superheat: at 10℃, the ambient temperature is relatively high, the evaporator has good heat absorption capacity, and a larger compensation step size of 100N can quickly increase the refrigerant circulation volume and accelerate the system pressure recovery; at -2℃ and -15℃, the ambient temperature decreases, and the risk of liquid return increases, so the compensation step size is reduced to 80N and 60N respectively, which reduces the risk of liquid return while ensuring the refrigerant circulation volume; at -22℃ and lower temperatures, the evaporator has extremely weak heat absorption capacity, and the risk of liquid return increases significantly, so the compensation step size is further reduced to 40N and 30N, prioritizing superheat and avoiding excessive compensation that could cause compressor liquid slugging damage.

[0034] In actual control, after the low-pressure protection is triggered, the system first retrieves the pre-stored initial opening degree of the main valve, matches it with the corresponding compensation step size based on the current ambient temperature, and determines the target opening degree of the main valve through a simple superposition calculation of the initial opening degree and the compensation step size. The main valve is then controlled to adjust to this target opening degree. This control method requires no complex calculations, has a fast response speed, and can quickly increase the refrigerant circulation volume, promote the evaporation of liquid refrigerant retained in the condenser, replenish the gaseous refrigerant on the compressor suction side, and avoid triggering the low-pressure protection again during startup. After the unit starts up smoothly and reaches a stable operating state, the system automatically exits the compensation mode, and the main valve opening returns to the normal control logic, ensuring the safety and efficiency of long-term operation.

[0035] Furthermore, the target rotational speed is determined based on the low-pressure reading and a preset correlation. The fan speed is adjusted according to the target speed. Through a precise fan speed control strategy based on low-pressure feedback, the evaporator heat exchange efficiency is specifically enhanced, addressing the technical challenge of insufficient refrigerant evaporation in the evaporator under low-temperature conditions, and providing crucial support for the system's low-pressure recovery. Specifically, during the parameter compensation phase, the system uses the currently collected low-pressure as a direct feedback basis for the evaporator's heat exchange status. The magnitude of the low-pressure is positively correlated with the evaporation rate of the liquid refrigerant in the evaporator; the lower the pressure, the less complete the evaporation of the liquid refrigerant in the evaporator, and the more insufficient the gaseous refrigerant supply to the compressor's suction side. The system's built-in preset correlation is a one-to-one mapping model between low-pressure and the target fan speed, calibrated through numerous low-temperature experiments. This model fully considers the heat exchange air volume requirements of the evaporator under different pressure ranges. Its core logic is: the lower the low-pressure value, the higher the corresponding target fan speed. Subsequently, the system adjusts the fan speed according to the determined target speed. Increasing the fan speed significantly increases the airflow through the evaporator heat exchange coils, enhancing the heat exchange between the air and refrigerant sides, accelerating the vaporization of the liquid refrigerant remaining in the evaporator, thereby increasing the supply of gaseous refrigerant to the compressor suction side and gradually raising the system low-pressure to the normal range. Conversely, if the low-pressure is in a relatively high range, a relatively low target fan speed is matched to avoid energy waste caused by ineffective high-load operation of the fan. This technical feature, through the linkage control of low-pressure and fan speed, achieves adaptive optimization of evaporator heat exchange efficiency under various operating conditions. It precisely solves the problem of difficulty in maintaining suction pressure at low temperatures from the refrigerant evaporation stage, providing stable operating support for the subsequent safe restart of the compressor and the rapid restoration of system thermodynamic balance.

[0036] Furthermore, the two detected low-pressure values ​​are P1 and P2, respectively. According to a preset correlation, the rotational speed corresponding to P1 is n1, and the rotational speed corresponding to P2 is n2; where P1 > P2, and n1 < n2. In the control process of determining the target fan speed based on the low-pressure values, the system sets a clear parameter matching logic: using the low-pressure parameters P1 and P2 obtained from the two detections as the control basis, and combining the preset correlation, an inverse relationship between the pressure value and the fan speed is established. When P1 > P2, the corresponding fan speed n1 < n2 is matched.

[0037] The design logic of this inverse mapping rule is highly compatible with the system operating characteristics under low-temperature conditions: the low-pressure value directly reflects the evaporation state of the refrigerant in the evaporator. When P2 is lower than P1, it means that the amount of gaseous refrigerant in the system is more scarce, the evaporation process of liquid refrigerant in the evaporator is more severely hindered, and the gaseous refrigerant supply gap on the compressor suction side is larger. At this time, by matching a higher fan speed n2, the airflow through the evaporator heat exchange coil can be significantly increased, the convective heat transfer intensity between the air side and the refrigerant side can be enhanced, the vaporization rate of the liquid refrigerant remaining in the evaporator can be accelerated, the amount of gaseous refrigerant on the compressor suction side can be quickly replenished, and the low-pressure can be pushed back to the normal range. When P1 is relatively high, the evaporation state of the evaporator is relatively good, and only a lower fan speed n1 is needed to meet the refrigerant evaporation requirements, ensuring the pressure recovery while avoiding ineffective energy consumption caused by high-load fan operation.

[0038] This quantitative inverse control strategy abandons the traditional extensive adjustment mode of fan speed, and achieves precise matching between fan speed and system low-pressure conditions. It ensures that the evaporator can maintain optimal heat exchange efficiency under different pressure imbalances, and provides precise and efficient support for the safe restart of the compressor and the rapid restoration of system thermodynamic balance.

[0039] Specifically, the system's built-in preset matching relationship is a linear quantitative matching model with clearly defined calibration rules: when the low-pressure is 0.1 MPa, the matched actual fan speed is 550 rpm; when the pressure drops to 0.08 MPa (a decrease of 0.02 MPa from 0.1 MPa), the fan speed simultaneously increases to 600 rpm; and so on, for every 0.02 MPa decrease in low-pressure, the fan speed increases by 50 rpm. This quantitative mapping rule is highly compatible with the system's operating characteristics under low-temperature conditions. The change in low-pressure value is a direct quantitative feedback of the refrigerant evaporation state within the evaporator. The lower the pressure, the more severely the evaporation process of the liquid refrigerant in the evaporator is hindered, the larger the gap in gaseous refrigerant supply on the compressor suction side, and the deeper the low-pressure imbalance in the system.

[0040] The control process based on this rule has clear adaptability to operating conditions: Under the relatively high low-pressure condition of 0.1MPa, the refrigerant evaporation state in the evaporator is relatively good, and a fan speed of 550n can provide a suitable heat exchange air volume, meeting the basic evaporation requirements while avoiding energy waste caused by high-load fan operation; when the pressure drops to 0.08MPa, the amount of liquid refrigerant retained in the evaporator increases, and the evaporation efficiency further decreases. At this time, increasing the fan speed to 600n can significantly increase the airflow through the evaporator heat exchange coil, enhance the convective heat transfer intensity between the air side and the refrigerant side, accelerate the vaporization process of the liquid refrigerant, and quickly replenish the gaseous refrigerant charge on the compressor suction side; for more severe operating conditions where the pressure continues to drop, the speed can be gradually increased according to the rule of "increasing by 50n for every 0.02MPa drop", which can achieve a precise match between the heat exchange intensity and the degree of low-pressure imbalance, ensuring that the evaporator always maintains the optimal evaporation efficiency adapted to the current operating conditions.

[0041] This linear quantitative control strategy eliminates the drawbacks of traditional coarse-grained fan speed regulation, and realizes precise closed-loop control from pressure detection to speed regulation. It not only ensures the rapid recovery of system pressure under severe low-pressure conditions, but also takes into account the energy efficiency of the operation process, providing stable and controllable technical support for the safe restart of the compressor and the efficient restoration of the system's thermodynamic balance.

[0042] Generally, the preset operating frequency is the compressor's minimum operating frequency. Under low / ultra-low temperature conditions, the compressor oil viscosity increases significantly, and the changes in the miscibility of the refrigerant and lubricating oil further increase the compressor's starting resistance. If the compressor restarts at the normal operating frequency, the excessive starting load can easily lead to compressor start-up failure, or damage to components due to increased mechanical wear, and may even trigger low-pressure protection again due to system pressure fluctuations at startup. Setting the preset operating frequency as the compressor's minimum operating frequency is designed to reduce the mechanical load during compressor startup, adapting to the high resistance characteristics under low-temperature conditions. The minimum operating frequency keeps the compressor's core motion parameters, such as rotor speed and piston reciprocating frequency, at their lowest thresholds, significantly reducing the starting torque requirement, lowering the frictional resistance of moving parts during startup, ensuring the compressor can start smoothly even in a high-viscosity oil environment, and avoiding damage to unit components from starting shocks.

[0043] Meanwhile, the minimum operating frequency setting takes into account the transitional operating conditions of the system after low-pressure protection: at this time, the system low-pressure has not yet fully recovered, and the supply of gaseous refrigerant is still unstable. Running the compressor at the lowest frequency reduces the instantaneous demand on the gaseous refrigerant on the suction side, avoiding liquid shortage operation or sudden pressure drop due to insufficient suction volume. This allows sufficient time for operating condition optimization for the main valve opening adjustment and fan speed adjustment mentioned earlier, enabling the system to gradually increase the gaseous refrigerant and raise the low-pressure to the normal range based on stable low-load compressor operation. After the system pressure stabilizes, the compressor can then gradually increase the operating frequency according to operating condition requirements, achieving a smooth transition from safe restart to stable operation.

[0044] By adopting a minimum frequency start-up design adapted to operating conditions, the core challenge of restarting after low-pressure protection at low temperatures is solved from the perspective of compressor operating load regulation. This not only ensures the safety and success rate of the restart process, but also provides a stable operating foundation for system parameter compensation and pressure recovery, further improving the reliability and adaptability of the entire start-up control strategy.

[0045] Among them, the low-load precision start-up strategy with fixed frequency and time duration is adapted to the high resistance characteristics of the compressor under low temperature / ultra-low temperature conditions, ensuring the safety and stability of compressor restart after low pressure protection, and reserving sufficient time window for system parameter compensation to take effect.

[0046] Specifically, the compressor starting frequency is set to 20Hz (i.e., the compressor's minimum operating frequency) and maintained at this frequency for 3 minutes. This parameter combination is based on experimental calibration of the system's response characteristics under low-temperature and low-pressure conditions. In low-temperature environments, the compressor oil viscosity increases significantly, and the mutual solubility of the refrigerant and lubricating oil further increases the compressor's mechanical resistance. If started at a conventional frequency, excessive starting load can easily cause compressor start-up failure, accelerated component wear, and even trigger low-pressure protection again due to insufficient instantaneous suction volume. The minimum operating frequency of 20Hz reduces the compressor rotor speed and piston / scroll disc movement frequency to the lowest threshold, significantly reducing the starting torque requirement and ensuring smooth compressor start-up under high-resistance conditions. Simultaneously, the fixed 3-minute running time matches the parameter compensation response cycle of the main valve opening adjustment and fan speed control. During this period, the effects of increased refrigerant circulation after adjusting the main valve opening and enhanced evaporator heat exchange efficiency after optimizing fan speed gradually become apparent. The liquid refrigerant remaining in the evaporator can fully vaporize, the amount of gaseous refrigerant on the compressor suction side steadily increases, and the system low-pressure gradually rises back to a safe range. After the 3-minute transition operation phase, the compressor can gradually increase its operating frequency to a value suitable for the current operating conditions based on real-time system pressure and temperature parameters, achieving a smooth transition from safe restart to stable operation.

[0047] The minimum operating frequency and transition operating time for different types of compressors to adapt to low-temperature conditions need to be specifically calibrated based on their own structural characteristics and application scenarios. The specific parameters are as follows: The minimum operating frequency for rotary compressors to adapt to low-temperature conditions is 10-15Hz, and the corresponding transition operating time is 1-2min. This type of parameter matching scheme is suitable for small household heat pump units. The minimum operating frequency for scroll compressors adapted to low-temperature conditions is 15-20Hz, with a corresponding transition time of 2-3 minutes. This type of parameter matching scheme is suitable for medium-sized commercial heat pump units. The minimum operating frequency for screw compressors adapted to low-temperature conditions is 8-12Hz, with a corresponding transition time of 3-5 minutes. This type of parameter matching scheme is suitable for large industrial heat pump units. The minimum operating frequency for centrifugal compressors adapted to low-temperature conditions is 5-10Hz, with a corresponding transition operating time of 5-8 minutes. This type of parameter matching scheme is suitable for ultra-large central air conditioning heat pump systems.

[0048] The parameter settings for all the above-mentioned compressors follow the core principles of low-load start-up and adapting to the system parameter compensation cycle. This ensures the start-up safety of the compressor under low-temperature and high-resistance conditions, and allows sufficient time for the compensation effects of main valve opening adjustment and fan speed control to take effect, thus avoiding secondary triggering of low-pressure protection in the system.

[0049] It is worth mentioning that when the ambient temperature is greater than or equal to the first threshold, the compressor restarts directly, and after N consecutive low-pressure protection cycles, the compressor shuts down. When the heat pump unit triggers low-pressure protection, if the current ambient temperature is detected to be greater than or equal to the first threshold, i.e., the system is in a non-low / ultra-low temperature operating condition, the triggering cause of low-pressure protection is usually not the core issues such as refrigerant liquefaction and retention, increased oil viscosity, or insufficient evaporator evaporation caused by low temperature, but rather stems from temporary disturbances during system operation, such as instantaneous refrigerant flow fluctuations, brief sensor signal drift, or occasional control deviations of the fan or main valve. Such temporary disturbances do not cause continuous damage to the thermodynamic balance of the system, so there is no need to perform complex parameter compensation procedures. Directly controlling the compressor to restart can quickly eliminate the impact of the disturbance and restore the system to normal operation. This design significantly shortens the recovery time of low-pressure protection under non-low temperature conditions and improves the unit's operating response efficiency.

[0050] The rule of shutting down the compressor after N consecutive low-pressure protection triggers is a fault safety judgment mechanism for non-low-temperature operating conditions. If the compressor triggers low-pressure protection N times consecutively within a short period after a direct restart, it indicates that the low-pressure anomaly is not caused by a temporary disturbance, but rather by a persistent fault, such as refrigerant leakage, main valve sticking failure, damage to compressor suction-side components, or sensor failure. In this case, forcibly restarting the compressor will not only fail to resolve the low-pressure anomaly, but will also cause frequent impact wear on moving parts due to repeated start-stop cycles under low-pressure conditions, exacerbating the risk of lubrication failure and ultimately leading to compressor damage or further system failure. Therefore, executing a shutdown operation after triggering N consecutive low-pressure protection triggers can promptly cut off the unit's operation under fault conditions, forming a safety safety net to prevent further spread of the fault. It also provides a clear fault judgment basis for subsequent manual maintenance, ensuring the long-term safety and reliability of the system.

[0051] Specifically, the first threshold is set to 10℃. If the compressor fails to restart after three consecutive restarts, and then stops restarting, it indicates that the low-pressure problem is caused by other reasons, and a fault report is sent for on-site repair. The first threshold for determining the operating condition is quantitatively set to 10℃, a value calibrated based on experimental results from heat pump unit operation characteristics. When the ambient temperature is ≥10℃, core problems such as excessive refrigerant liquefaction and retention, increased compressor oil viscosity, and insufficient evaporation caused by low temperatures will not occur. In this case, the triggering factors for low-pressure protection are mostly temporary disturbances during system operation, such as instantaneous refrigerant flow fluctuations, brief sensor signal drift, and occasional control deviations of the fan or main valve. These temporary disturbances do not cause sustained damage to the system's thermodynamic balance; therefore, there is no need to perform complex parameter compensation procedures. Directly restarting the compressor can quickly eliminate the disturbance's impact and restore the system to normal operation. This design significantly shortens the recovery time of low-pressure protection under non-low-temperature conditions and improves the unit's operational response efficiency.

[0052] Meanwhile, a rule is established to shut down and report a fault after three consecutive unsuccessful compressor restarts, thus constructing a safety judgment and protection mechanism for fault conditions. If the compressor triggers low-pressure protection three times in a short period of time after a direct restart, it indicates that the system's low-pressure anomaly is not caused by a temporary disturbance, but rather by a persistent fault, such as refrigerant leakage, main valve jamming failure, damage to compressor suction-side components, or pressure sensor failure. If the compressor is forcibly restarted again in this situation, it will cause repeated start-stop cycles under low-pressure conditions, resulting in frequent impact wear on moving parts, exacerbating the risk of lubrication failure, and ultimately leading to compressor damage or an expansion of the system fault range. Therefore, after three consecutive failed restarts, the system immediately controls the compressor to stop restarting and outputs a fault signal, guiding personnel to conduct on-site repairs. This not only prevents further spread of the fault but also provides repair personnel with clear fault judgment criteria, significantly improving the efficiency and accuracy of fault diagnosis.

[0053] In summary, this application, by constructing parameter compensation and adaptive restart control logic under low-temperature conditions, can automatically handle temporary low-pressure problems caused by harsh conditions such as low and ultra-low temperatures. The system can self-recover without manual intervention or waiting for the environment to warm up, significantly reducing the number of unexplained unit shutdowns and effectively ensuring the continuous heating or cooling capacity of the heat pump unit in low-temperature scenarios, thus significantly optimizing the user experience. Furthermore, the low-load soft-start recovery strategy, which restarts the compressor by matching its minimum operating frequency and combining precise control of the main valve opening and fan speed, avoids the mechanical shock caused by high-load hard starts of the compressor under adverse conditions. Simultaneously, the shutdown protection mechanism after consecutive restart failures prevents the accumulation of electrical and mechanical stress caused by frequent compressor starts and stops, reducing component wear and failure risks, effectively protecting the core components of the unit, and extending the overall service life of the equipment.

[0054] In addition, this solution requires no new hardware equipment; all functions can be achieved simply by optimizing the unit's startup control logic, giving it the advantage of zero hardware cost. At the same time, the control logic is compatible with heat pump units of various types of compressors, such as rotary, scroll, and screw compressors, and is suitable for heat pump systems in all scenarios, including small residential, medium commercial, and large industrial applications. It features strong versatility, low retrofit cost, and high implementation efficiency.

[0055] On the other hand, such as Figure 3 As shown, a start-up control device after low-voltage protection is also provided, comprising: The detection module 11 is used to detect the current ambient temperature and the low pressure of the system after the heat pump unit triggers low pressure protection. The target determination module 12 is used to enter the parameter compensation stage when the ambient temperature is less than the first threshold, and to determine the target adjustment parameter according to the ambient temperature, the low pressure and the preset comparison relationship during the parameter compensation stage. Control module 13 is used to adjust the main valve opening and fan speed according to the target adjustment parameters. After the adjustment is completed, the compressor is controlled to start running and restart according to the preset operating frequency.

[0056] In the above scheme, the detection module 11 is the core of the entire device's operating condition perception. Its working logic is deeply integrated with the triggering state of low-pressure protection: the moment the heat pump unit triggers low-pressure protection, this module immediately starts the data acquisition process to accurately capture two key parameters: the current ambient temperature and the system low-pressure. The ambient temperature parameter is used to determine whether the unit is in a low-temperature / ultra-low-temperature operating condition, and the system low-pressure parameter is used to quantify the degree of current system pressure imbalance. The real-time detection results of these two parameters together constitute the basic data source for subsequent parameter compensation and control decisions, ensuring that the entire control process is based on evidence and avoiding blind adjustments.

[0057] The target determination module 12 is the core decision-making unit of the device, and its operation is subject to specific triggering conditions. The module only enters the parameter compensation stage when the ambient temperature collected by the detection module 11 is lower than a first threshold. During this stage, the module incorporates a pre-calibrated reference relationship model, calibrated through numerous low-temperature operating condition experiments. This model integrates the mapping relationships between different ambient temperature ranges, different low-pressure values, and the target opening degree of the main valve and the target speed of the fan. The module retrieves the ambient temperature and low-pressure data transmitted by the detection module 11, substitutes them into the reference relationship model for matching calculations, and ultimately outputs target adjustment parameters that are precisely adapted to the current operating conditions. This provides clear and quantifiable control commands for subsequent execution stages, achieving differentiated matching of adjustment parameters based on operating conditions.

[0058] The control module 13 is the instruction execution terminal of the device, undertaking the core functions of parameter adjustment and compressor restart. Its operation is divided into two stages: The first stage is parameter adjustment execution. The module determines the target adjustment parameters output by module 12 based on the target, and precisely controls the main valve opening and fan speed. By adjusting the main valve opening, the refrigerant circulation volume in the system is increased, promoting the participation of liquid refrigerant retained in the condenser in the circulation and increasing the proportion of gaseous refrigerant. By adjusting the fan speed, the heat exchange efficiency of the evaporator is enhanced, accelerating the vaporization process of the liquid refrigerant and ensuring the supply of gaseous refrigerant on the compressor suction side, thereby improving the system's low-pressure insufficiency from two dimensions. The second stage is compressor restart control. After the main valve opening and fan speed are adjusted to the appropriate levels, the module controls the compressor to start operating according to a preset operating frequency (usually the compressor's minimum operating frequency). This adapts to the high viscosity of compressor oil and high starting resistance under low-temperature conditions, avoiding triggering low-pressure protection again due to excessive starting load or causing damage to compressor components.

[0059] The three modules form a collaborative operation mechanism for data exchange and command transmission. The detection module 11 provides a basis for decision-making, the target determination module 12 provides a standard for execution, and the control module 13 provides a guarantee for system recovery. The three work together to realize the full-process automated control from operating condition identification to parameter adjustment and unit restart after low-pressure protection. This effectively solves the technical problem of the heat pump unit's low-pressure protection being difficult to self-recover under low-temperature conditions, and improves the stability and intelligence level of the unit's operation.

[0060] On the other hand, such as Figure 4 As shown, a start-up control device after low-voltage protection is also provided, comprising: The device includes a processor 21, a memory 22, a communication module 23, an input device 24, and an output device 25. The number of processors 21 and the number of memories 22 in this low-voltage protection startup control device can be one or more. The processor 21, memory 22, communication module 23, input device 24, and output device 25 of this low-voltage protection startup control device can be connected via a bus or other means.

[0061] The memory 22, as a computer-readable storage medium, can be used to store software programs, computer-executable programs, and modules, such as the program instructions / modules corresponding to the low-voltage protection startup control method described in any embodiment of this application (e.g., the detection module 11, target determination module 12, and control module 13 in the low-voltage protection startup control device). The memory 22 may mainly include a program storage area and a data storage area, wherein the program storage area may store the operating system and at least one application program required for a function; the data storage area may store data created according to the use of the device, etc. In addition, the memory 22 may include a high-speed random access memory 22, and may also include non-volatile memory 22, such as at least one disk storage device 22, a flash memory device, or other non-volatile solid-state memory 22.

[0062] In some instances, memory 22 may further include memory 22 remotely located relative to processor 21, and these remote memories 22 may be connected to the device via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0063] The communication module 23 is used for data transmission.

[0064] The processor 21 executes various functional applications and data processing of the device by running software programs, instructions and modules stored in the memory 22, thereby realizing the startup control method after the low voltage protection mentioned above.

[0065] Input device 24 can be used to receive input digital or character information, and to generate key signal inputs related to user settings and function control of the device. Output device 25 may include display devices such as a display screen.

[0066] The startup control device after low-voltage protection provided above can be used to execute the startup control method after low-voltage protection provided in the above embodiments, and has corresponding functions and beneficial effects.

[0067] This application embodiment also provides a storage medium for storing computer-executable instructions. When executed by a computer processor 21, the computer-executable instructions are used to perform a startup control method after low-pressure protection. The startup control method after low-pressure protection includes: after the heat pump unit triggers low-pressure protection, detecting the current ambient temperature and the system's low-pressure; when the ambient temperature is less than a first threshold, entering a parameter compensation stage; in the parameter compensation stage, determining target adjustment parameters based on the ambient temperature, the low-pressure, and a preset comparison relationship; adjusting the main valve opening and the fan speed according to the target adjustment parameters; and after adjustment, controlling the compressor to restart according to a preset operating frequency.

[0068] The storage medium is any type of memory device 22 or storage device. The term "storage medium" is intended to include: mounting media, such as CD-ROM, floppy disk, or magnetic tape devices; computer system memory 22 or random access memory 22, such as DRAM, DDRRAM, SRAM, EDORAM, Rambus RAM, etc.; non-volatile memory 22, such as flash memory, magnetic media (e.g., hard disk or optical storage); registers or other similar types of memory elements 22, etc. The storage medium may also include other types of memory 22 or combinations thereof. Furthermore, the storage medium may reside in a first computer system in which the program is executed, or it may reside in a different second computer system connected to the first computer system via a network (such as the Internet). The second computer system can provide program instructions to the first computer for execution. The term "storage medium" may include two or more storage media residing in different locations (e.g., in different computer systems connected via a network). The storage medium may store program instructions (e.g., specifically implemented as a computer program) executable by one or more processors 21.

[0069] Of course, the computer-executable instructions stored in the storage medium provided in the embodiments of this application are not limited to the startup control method after low-voltage protection as described above, but can also execute related operations in the startup control method after low-voltage protection provided in any embodiment of this application.

[0070] The low-voltage protection start-up control device, equipment, and storage medium provided in the above embodiments can execute the low-voltage protection start-up control method provided in any embodiment of this application. For technical details not described in detail in the above embodiments, please refer to the low-voltage protection start-up control method provided in any embodiment of this application.

[0071] In the description herein, it should be understood that the terms "upper," "lower," "left," "right," and other orientations or positional relationships are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used merely for descriptive distinction and have no special meaning.

[0072] In the description of this specification, references to terms such as "an embodiment," "example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0073] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0074] The technical principles of this application have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of this application without inventive effort, and these embodiments will all fall within the scope of protection of this application.

Claims

1. A start-up control method after low-pressure protection, used in a heat pump unit, characterized in that, The method includes: After the heat pump unit triggers low-pressure protection, the ambient temperature and the system's low-pressure are detected. When the ambient temperature is less than the first threshold, the parameter compensation stage is entered, and the target adjustment parameter is determined according to the ambient temperature, the low pressure, and the preset comparison relationship. The main valve opening and fan speed are adjusted according to the target adjustment parameters, and the compressor is restarted according to the preset operating frequency.

2. The start-up control method after low-voltage protection according to claim 1, characterized in that, The opening degree of the main valve is adjusted in the following manner: The compensation opening degree is determined based on the ambient temperature and the preset comparison relationship; The target opening degree is determined based on the initial opening degree of the main valve and the compensation opening degree. The main valve opening is adjusted according to the target opening to increase the refrigerant circulation volume.

3. The start-up control method after low-voltage protection according to claim 2, characterized in that, Also includes: Before the heat pump unit triggers low-pressure protection, the initial opening degree of the main valve is obtained, and the compensation opening degree is added to the initial opening degree of the main valve to determine the target opening degree of the main valve.

4. The start-up control method after low-voltage protection according to any one of claims 1-3, characterized in that, The fan speed is adjusted in the following way: The target rotational speed is determined based on the low-pressure and the preset comparison relationship; Adjust the fan speed according to the target speed.

5. The start-up control method after low-voltage protection according to claim 4, characterized in that, In the preset comparison relationship, for any two pressure values ​​P1 and P2, corresponding to rotational speeds n1 and n2, if P1 > P2, then n1 < n2.

6. The start-up control method after low-voltage protection according to any one of claims 1-3, characterized in that, The preset operating frequency is the minimum operating frequency of the compressor.

7. The start-up control method after low-voltage protection according to any one of claims 1-3, characterized in that, After the heat pump unit triggers low-pressure protection, and after detecting the ambient temperature and the system's low-pressure, the following steps are also included: When the ambient temperature is greater than or equal to the first threshold, the compressor is controlled to restart directly, and when the low-pressure protection is triggered continuously for a preset number of times, the compressor is controlled to stop.

8. A start-up control device after low-voltage protection, characterized in that, include: The detection module is used to detect the ambient temperature and the low pressure of the system after the heat pump unit triggers the low pressure protection. The target determination module is used to enter the parameter compensation stage when the ambient temperature is less than a first threshold, and to determine the target adjustment parameters based on the ambient temperature, the low pressure, and a preset comparison relationship. The control module is used to adjust the main valve opening and fan speed according to the target adjustment parameters, and to control the compressor to start running and restart according to the preset operating frequency.

9. A start-up control device after low-voltage protection, characterized in that, include: Memory and one or more processors; The memory is used to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method as described in any one of claims 1-7.

10. A storage medium for storing computer-executable instructions, characterized in that, The computer-executable instructions, when executed by a processor, are used to perform the method as described in any one of claims 1-7.

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