Air conditioning system and control method and control device thereof

Abstract

The invention provides an air conditioning system and a control method and device thereof. The air conditioning system comprises a first heat exchanger, a second heat exchanger, an electronic expansion valve and at least two compressors, the compressor which is started firstly serves as an advanced compressor, and the compressor which is started later serves as a lagging compressor; the detection device is used for detecting the running state of the advanced compressor; in the control device, an obtaining module is used for obtaining the compression ratio of an advanced compressor under the condition that an inlet guide vane of the advanced compressor reaches a full-open state; the first control module is used for executing load shedding operation on the advanced compressor according to the compression ratio of the advanced compressor and keeping an inlet guide vane in a full-open state; and the second control module is used for starting the lagging compressor when determining that the load shedding of the leading compressor is finished. According to the method, it is ensured that the advanced compressor is in a stable state and is not prone to surging, meanwhile, the lagging compressor can overcome the minimum resistance to be started under the working condition, the cut-in and cut-out reliability of the compressor is guaranteed, and downtime is effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical appliances, and particularly to an air conditioning system, a control method and a control device thereof. Background Art

[0002] In the related art, the existing method only judges the Demand (load) assignment when the booster head is added by the advanced compressor pressure ratio. Under high pressure ratio conditions, the unloading capacity of the compressor is limited. If judged according to P and Pset, the Demand assignment is too low, and the compressor continuously unloads, resulting in the actual speed approaching the surge speed, and the speed cannot continue to decrease. By closing the inlet guide vane to continue unloading, the compressor enters a mechanical control mode with slower control adjustment from the speed control mode, and then the lag machine starts, and the working condition changes sharply, resulting in the advanced machine adjusting the IGV (inlet guide vane, the full English name is Inlet guide vanes) untimely in the mechanical control mode and causing a surge failure.

[0003] Among them, the speed control mode directly adjusts the speed by frequency modulation to control the amount of suction. In this mode, the inlet guide vane IGV is fully opened, without mechanical loss and with fast response; the mechanical control mode adjusts the amount of suction by adjusting the opening of the inlet guide vane. The IGV adjustment is slow, and it is easy to cause surge due to the slow adjustment of the IGV under the condition of sharp change of pressure ratio. Summary of the Invention

[0004] The present invention provides an air conditioning system, a control method and a control device thereof to solve the defects existing in the prior art and achieve the following technical effects: ensuring that the advanced compressor is in a stable state and not easy to surge, while the lag compressor can overcome the minimum resistance start under this working condition, ensuring the reliability of the compressor to cut in and cut out, and effectively avoiding downtime.

[0005] The air conditioning system according to the first aspect embodiment of the present invention includes: A first heat exchanger, a second heat exchanger, an electronic expansion valve and at least two compressors. The suction port and the discharge port of each compressor are respectively connected to the first heat exchanger and the second heat exchanger. Among them, the compressor started first is used as the advanced compressor and the compressor started later is used as the lag compressor; A detection device for detecting the operating state of the advanced compressor; A control device, including an acquisition module, a first control module and a second control module; The acquisition module is used to obtain the compression ratio of the advanced compressor when the inlet guide vane of the advanced compressor reaches the fully open state; the first control module is used to perform a load reduction operation on the advanced compressor according to the compression ratio of the advanced compressor and keep the inlet guide vane in the fully open state; the second control module is used to determine that the load reduction of the advanced compressor is completed, and then start the lag compressor.

[0006] According to an embodiment of the present invention, the first control device is specifically configured to: Calculate the minimum allowable load of the leading compressor according to the compression ratio of the leading compressor, and control the leading compressor to unload to the minimum operable load; Wherein, the minimum operable load is the minimum load at which the leading compressor can operate while keeping the inlet guide vane fully open.

[0007] In this way, through the above process, the embodiment of the present invention ensures a smooth transition during the operation of adding compressors in a multi-compressor system, improves the overall reliability and energy efficiency of the system, and also extends the service life of the compressor.

[0008] According to an embodiment of the present invention, in the step of calculating the minimum allowable load of the leading compressor according to the compression ratio of the leading compressor: If the compression ratio of the leading compressor is P and the minimum allowable load of the leading compressor is D, the calculation relationship between the compression ratio and the minimum allowable load is as follows: .

[0009] In summary, this formula establishes a complex relationship between the compression ratio and the minimum allowable load by considering the quadratic and linear terms of the compression ratio, as well as a constant term, to achieve dynamic and precise load adjustment.

[0010] According to an embodiment of the present invention, in the first control device, the step of controlling the leading compressor to unload to the minimum operable load specifically includes: Calculate the minimum allowable speed of the leading compressor according to the minimum allowable load, and control the speed of the leading compressor to decrease to the minimum operable speed.

[0011] In this way, speed is a key parameter directly affecting the output and working state of the compressor. By adjusting the speed, the suction volume and output power of the compressor can be effectively controlled.

[0012] According to an embodiment of the present invention, a cut-in branch is connected in parallel on both sides of the suction port and the discharge port of each compressor, and a cut-in valve is provided on the cut-in branch.

[0013] In this way, the configuration of the cut-in branch and the cut-in valve enables the system to dynamically adjust the load of each compressor according to the actual operating requirements.

[0014] According to an embodiment of the present invention, the second control device is specifically configured to: Determine that the load reduction of the leading compressor is completed, and control the lagging compressor to enter the startup process; Wherein, when the startup process is started, control the cut-in valve corresponding to the lagging compressor to open; after the startup process ends, control the cut-in valve corresponding to the lagging compressor to close.

[0015] In this way, through the above steps, the second control device effectively coordinates the load reduction of the leading compressor and the startup of the lagging compressor, not only ensuring the smoothness of the startup process, but also maximizing the energy efficiency and reliability of the system.

[0016] According to an embodiment of the present invention, in the second control device, the step of controlling the lagging compressor to enter the startup process specifically includes: During the startup process, control the inlet guide vane of the lagging compressor to reach the fully open state, and adjust the load of the lagging compressor to the minimum operable load.

[0017] In this way, through the above control strategy, the lagging compressor can operate under very favorable working conditions at the initial stage of startup. The fully open inlet guide vane plus the carefully calculated minimum load not only helps the compressor to quickly and stably reach the designed working state, but also helps the entire unit to achieve smooth energy transfer during the process of adding compressor heads, avoiding system disturbances caused by sudden load changes.

[0018] According to an embodiment of the present invention, the control device further includes a third control module, and the third control module is used to open the inlet guide vane of the leading compressor to the fully open state when the inlet guide vane of the leading compressor does not reach the fully open state.

[0019] In this way, the fully open inlet guide vane can ensure that the compressor starts to work with the highest efficiency and response speed, while avoiding delays and unstable factors caused by guide vane adjustment at the initial stage of startup.

[0020] According to the control method of the air-conditioning system according to the second aspect embodiment of the present invention, the air-conditioning system includes at least two compressors, wherein the compressor started first is used as the leading compressor and the compressor started later is used as the lagging compressor; the method includes: Detect the operating state of the leading compressor; When the inlet guide vane of the leading compressor reaches the fully open state, obtain the compression ratio of the leading compressor; According to the compression ratio of the leading compressor, perform a load reduction operation on the leading compressor and keep the inlet guide vane in the fully open state; Determine that the load reduction of the leading compressor is completed, and then start the lagging compressor.

[0021] A control device for an air conditioning system according to an embodiment of the third aspect of the present invention, the air conditioning system includes at least two compressors, wherein the compressor started first is used as the leading compressor and the compressor started later is used as the lagging compressor; the device includes: An acquisition module, configured to acquire the compression ratio of the leading compressor when the inlet guide vane of the leading compressor reaches the fully open state; A first control module, configured to perform a load reduction operation on the leading compressor according to the compression ratio of the leading compressor and keep the inlet guide vane in the fully open state; A second control module, configured to start the lagging compressor when it is determined that the load reduction of the leading compressor is completed.

[0022] The present invention provides an air conditioning system. By obtaining the opening state of the inlet guide vane of the leading compressor and performing different load reduction operations on the leading compressor according to different current compression ratios, it ensures that the leading compressor is in a stable state and is not prone to surge. At the same time, the lagging compressor can start by overcoming the minimum resistance under this working condition, ensuring the reliability of the compressor's cut-in and cut-out, and effectively avoiding downtime. Further, the present invention has at least the following advantages compared with the related art.

[0023] (1) Enhanced surge prevention ability: By monitoring the opening of the inlet guide vane of the leading compressor and ensuring that it is fully open before starting the additional compressor, the present invention effectively avoids the situation where the leading compressor starts the lagging compressor in the mechanical control mode, greatly reducing the surge risk caused by the closing of the inlet guide vane. This strategy ensures the system stability during the process of starting the additional compressor and extends the service life of the compressor.

[0024] (2) Dynamic load reduction control: The acquisition module dynamically adjusts the working load (Demand value) of the leading compressor according to the real-time compression ratio of the leading compressor. This approach is more precise and flexible than the traditional method that only relies on a fixed pressure ratio threshold to determine the load reduction. This dynamic adjustment not only ensures the stable operation of the leading compressor during the process of starting the additional compressor but also ensures that it operates in an efficient speed control mode, reducing the risk of approaching the surge speed due to excessive load reduction.

[0025] (3) Optimized starting strategy for the lagging compressor: The second control module ensures that the lagging compressor is started only when the leading compressor successfully completes the load reduction and remains in the most stable state. This enables the lagging compressor to start under the minimum backpressure condition, reducing the starting resistance and the starting difficulty, and further avoiding the unstable phenomenon during the process of starting the additional compressor.

[0026] (4) Improve the overall efficiency and reliability of the system: The present invention achieves a smooth transition of the compressor head increase process through the above-mentioned refined control strategy, which not only improves the operating efficiency of the entire system, but also significantly enhances the reliability and stability of the system. This intelligent control method reduces system shutdown or performance degradation caused by improper operation, and ensures the efficient operation of the system under various working conditions.

[0027] (5) Strong adaptability: Due to the use of more flexible and intelligent control logic, the present invention can better adapt to different working conditions and load changes. Regardless of high pressure ratio or low pressure ratio conditions, it can ensure the smooth operation of the compressor when the head is increased, thereby improving the versatility and adaptability of the system.

[0028] In summary, the present invention significantly improves the operating efficiency and stability of multi-compressor air-conditioning systems through precise monitoring, dynamic load reduction strategies and optimized compressor start-up sequence, effectively solves the surge problem existing in the prior art, and provides a more advanced and reliable solution for large-scale air-conditioning systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 It is a structural schematic diagram of the air conditioning system provided by the present invention.

[0031] Figure 2 It is a flow chart of the control method of the air conditioning system provided by the present invention.

[0032] Figure 3 It is a structural schematic diagram of a control device and a detection device of an air conditioning system provided by the present invention.

[0033] Figure 4 It is a structural schematic diagram of the electronic device provided by the present invention.

[0034] Description of reference numerals: 1. First heat exchanger; 2. Second heat exchanger; 3. Electronic expansion valve; 4. Lead compressor; 5. Lag compressor; 6. Cut-in branch; 7. Cut-in valve; 110. Acquisition module; 120. First control module; 130. Second control module; 200. Detection device. DETAILED DESCRIPTION

[0035] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the embodiments of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and should not be construed as indicating or implying relative importance.

[0036] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or simply means that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or simply means that the first feature has a lower horizontal height than the second feature.

[0037] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0038] The following introduces an air-conditioning system, its control method and control device according to the present invention with reference to the accompanying drawings.

[0039] As Figure 1As shown in the figure, the air-conditioning system according to the embodiment of the first aspect of the present invention includes a first heat exchanger 1, a second heat exchanger 2, an electronic expansion valve 3, at least two compressors, a detection device 200, and a control device.

[0040] The suction port and the discharge port of each compressor are respectively connected to the first heat exchanger 1 and the second heat exchanger 2. Among them, the compressor started first is used as the leading compressor 4, and the compressor started later is used as the lagging compressor 5.

[0041] The detection device 200 is used to detect the operating state of the leading compressor 4; The control device includes an acquisition module, a first control module, and a second control module.

[0042] The acquisition module is used to obtain the compression ratio of the leading compressor 4 when the inlet guide vane of the leading compressor 4 reaches the fully open state; the first control module is used to perform a load reduction operation on the leading compressor 4 according to the compression ratio of the leading compressor 4 and keep the inlet guide vane in the fully open state; the second control module is used to determine that the load reduction of the leading compressor 4 is completed, and then start the lagging compressor 5.

[0043] It can be understood that in the above air-conditioning system, the first heat exchanger 1 and the second heat exchanger 2 are respectively used for the evaporation (heat absorption) and condensation (heat release) of the refrigerant. The suction port of the compressor is connected to the first heat exchanger 1, and the discharge port is connected to the second heat exchanger 2 to form a closed refrigeration cycle. The electronic expansion valve 3 is located in front of the first heat exchanger 1 (evaporator) and is used to adjust the refrigerant flow rate entering the evaporator, thereby controlling the evaporation temperature and pressure.

[0044] The air-conditioning system is designed with at least two compressors, one as the leading compressor 4 (starting and running first), and the other as the lagging compressor 5 (starting when needed). For example, the system includes two compressors. There are two first connection ports on the first heat exchanger 1 and two second connection ports on the second heat exchanger 2. The suction port and the discharge port of each compressor are respectively connected to the first connection port and the second connection port.

[0045] The detection device 200 is used to monitor the operating state of the leading compressor 4, especially the opening degree of the inlet guide vane. The control device includes an acquisition module, a first control module, and a second control module, which are responsible for coordinating the operation logic of the compressors.

[0046] The specific working principle and process of the air-conditioning system according to the embodiment of the present invention are introduced as follows.

[0047] First of all, the detection device 200 monitors the operating state of the leading compressor 4 in real time, with a focus on checking whether the inlet guide vane is in the fully open state. The fully open inlet guide vane means that the compressor is operating in the speed control mode. At this time, the compressor has high efficiency, fast response, and no mechanical loss.

[0048] When the detection device 200 confirms that the inlet guide vane of the leading compressor 4 reaches the fully open condition, the acquisition module starts to work. It will read the instantaneous compression ratio of the leading compressor 4 (i.e., the ratio of the compressor outlet pressure to the inlet pressure). The compression ratio is an important indicator for evaluating the working load of the compressor.

[0049] The first control module calculates the degree of load reduction required for the leading compressor 4 based on the acquired compression ratio value. Here, a specific function (such as ) is used to determine the degree of load reduction to ensure that the leading compressor 4 remains in the speed control mode after load reduction and does not close the inlet guide vane. The purpose of load reduction is to create favorable working conditions for the upcoming lagging compressor 5 to start and avoid surging.

[0050] Once the leading compressor 4 is load-reduced to the predetermined state, the second control module receives a signal to confirm that the leading compressor 4 is ready to accept new load adjustment. At this time, the second control module is responsible for starting the preparation work of the lagging compressor 5.

[0051] While ensuring the successful load reduction of the leading compressor 4 and keeping the inlet guide vane fully open, the second control module sends an instruction to start the lagging compressor 5. When starting the lagging compressor 5, gas is usually supplied to the lagging compressor 5 through a specific control valve (such as the cut-in valve 7), and at the same time, the same Demand value as that of the leading compressor 4 is set for the lagging compressor 5 to ensure that the two compressors can work together to jointly handle the system load.

[0052] After the lagging compressor 5 starts and operates stably, the system will automatically close the cut-in valve 7. At this time, the leading compressor 4 and the lagging compressor 5 jointly participate in the energy regulation of the system, dynamically adjusting their respective working loads according to the actual load demand to ensure the efficient and stable operation of the entire system, avoid surging phenomena, and at the same time extend the service life of the compressor and improve the overall reliability of the unit.

[0053] In summary, the entire adjustment process of the air-conditioning system is a highly automated and refined control process, aiming to achieve a smooth transition and efficient operation when adding a compressor head to a multi-compressor chiller through precise compressor state monitoring and intelligent load adjustment strategies.

[0054] In the related art, the existing method only judges the Demand (load) assignment during the booster compressor startup by the pressure ratio of the booster compressor 4. Under high pressure ratio conditions, the unloading capacity of the compressor is limited. If judged according to P and Pset, the Demand assignment is too low, and the compressor continuously unloads, resulting in the actual speed approaching the surge speed. The speed cannot continue to decrease. By closing the inlet guide vane to continue unloading, the compressor enters the mechanical control mode with slower control adjustment from the speed control mode, and then the lag compressor starts. The working condition changes sharply, resulting in the surge failure of the booster compressor due to the untimely adjustment of the IGV (inlet guide vane, the full English name is Inlet guide vanes) in the mechanical control mode.

[0055] Among them, the speed control mode controls the amount of suction air by directly adjusting the speed through frequency modulation. In this mode, the inlet guide vane IGV is fully opened, without mechanical loss, and the response is fast; the mechanical control mode adjusts the amount of suction air by adjusting the opening degree of the inlet guide vane. The IGV adjustment is slow, and it is easy to cause surge due to the slow IGV adjustment in the case of sharp changes in the pressure ratio.

[0056] Therefore, in order to solve the technical defects existing in the above related art, the present invention provides an air-conditioning system. The system obtains the opening state of the inlet guide vane of the booster compressor 4, and then performs different unloading operations on the booster compressor 4 according to different current compression ratios, ensuring that the booster compressor 4 is in a stable state and not prone to surge. At the same time, the lag compressor 5 can start by overcoming the minimum resistance under this working condition, ensuring the reliability of the compressor's cut-in and cut-out, and effectively avoiding downtime.

[0057] Furthermore, the present invention has at least the following advantages compared with the related art.

[0058] (1) Enhanced surge prevention ability: By monitoring the opening degree of the inlet guide vane of the booster compressor 4 and ensuring that it is fully opened before performing the machine addition operation, the present invention effectively avoids the situation where the booster compressor 4 starts after the lag compressor 5 in the mechanical control mode, greatly reducing the surge risk caused by the closing of the inlet guide vane. This strategy ensures the system stability during the machine addition process and extends the compressor life.

[0059] (2) Dynamic unloading control: The acquisition module dynamically adjusts its working load (Demand value) according to the real-time compression ratio of the booster compressor 4. This approach is more precise and flexible than the traditional method that only relies on a fixed pressure ratio threshold to determine unloading. This dynamic adjustment not only ensures the stable operation of the booster compressor 4 during the machine addition stage but also ensures that it operates in the efficient speed control mode, reducing the risk of approaching the surge speed due to excessive unloading.

[0060] (3)Optimized starting strategy for the lag compressor 5: The second control module ensures that the lag compressor 5 is started only when the lead compressor 4 has successfully unloaded and maintained the most stable state. This enables the lag compressor 5 to start under the minimum backpressure condition, reducing the starting resistance, lowering the starting difficulty, and further avoiding the instability of the system during the process of adding a compressor head.

[0061] (4)Improving the overall efficiency and reliability of the system: Through the above-mentioned refined control strategy, the present invention realizes a smooth transition during the process of adding a compressor head to the compressor, not only improving the operating efficiency of the entire system, but also significantly enhancing the reliability and stability of the system. This intelligent control method reduces system shutdowns or performance degradation caused by improper operation, ensuring the efficient operation of the system under various working conditions.

[0062] (5)Strong adaptability: Due to the adoption of a more flexible and intelligent control logic, the present invention can better adapt to different working conditions and load changes. Whether it is a high-pressure ratio or a low-pressure ratio working condition, it can ensure the smooth operation of the compressor when adding a compressor head, improving the versatility and adaptability of the system.

[0063] In summary, through precise monitoring, dynamic unloading strategies, and optimized compressor starting sequences, the present invention significantly improves the operating efficiency and stability of the multi-compressor air-conditioning system, effectively solves the surging problem existing in the prior art, and provides a more advanced and reliable solution for large-scale air-conditioning systems.

[0064] According to some embodiments of the present invention, the first control device is specifically configured to: calculate the minimum allowable load of the lead compressor 4 according to the compression ratio of the lead compressor 4, and control the lead compressor 4 to unload to the minimum operable load.

[0065] Wherein, the minimum operable load is the minimum load that the lead compressor 4 can operate while keeping the inlet guide vane fully open.

[0066] It can be understood that this embodiment describes how to dynamically adjust the load of the lead compressor 4 through the first control device in the present invention to ensure the avoidance of surging phenomena during the process of adding a compressor head.

[0067] Furthermore, the specific working process of the unloading operation is as follows: First, the system monitors the real-time operating pressure ratio of the lead compressor 4, that is, the ratio of the compressor outlet pressure to the inlet pressure. This pressure ratio reflects the working state and load level of the compressor. Based on the current compression ratio of the lead compressor 4, the first control device uses a specific algorithm to calculate the minimum load that the compressor can operate under the condition of not closing the inlet guide vane (i.e., keeping it fully open and maintaining a more efficient speed control mode). This minimum load value is the critical point to ensure that the compressor does not enter the mechanical control mode and avoid the risk of surging caused by slow adjustment speed.

[0068] Once the minimum operable load is calculated, the first control device actively adjusts the lead compressor 4 to unload it to the calculated minimum load. During the unloading process, the output power or suction volume of the compressor will decrease accordingly, but at the same time, it is ensured that the inlet guide vane remains fully open and operates in an efficient speed control mode.

[0069] For example, assume that in a multi-compressor chiller, the lead compressor 4 is currently operating at full load, and its compression ratio P is 3.5. At this time, the system detects that an additional compressor needs to be added to meet higher refrigeration demand. The control device calculates, according to a preset algorithm, that at the current compression ratio P = 3.5, the minimum operable load of the lead compressor 4 is a specific value X (the unit may be percentage load or actual power value).

[0070] Next, the first control device reduces the load of the lead compressor 4 to the value X by adjusting the rotational speed of the lead compressor 4 or by means of hot gas bypass, etc., while ensuring that the inlet guide vane remains fully open. The purpose of this is to create the most favorable conditions for the start-up of the lag compressor 5 while ensuring the stable operation of the lead compressor 4, that is, the minimum backpressure environment, thereby avoiding the surge problem caused by the sudden change in operating conditions due to the addition of a compressor.

[0071] In this way, through the above process, the embodiments of the present invention ensure a smooth transition during the operation of adding a compressor in a multi-compressor system, improve the overall reliability and energy efficiency of the system, and also extend the service life of the compressor.

[0072] In some specific embodiments of the present invention, in the step of calculating the minimum allowable load of the lead compressor 4 according to the compression ratio of the lead compressor 4: the compression ratio of the lead compressor 4 is P, and the minimum allowable load of the lead compressor 4 is D, then the calculation relationship between the compression ratio and the minimum allowable load is as follows: .

[0073] In this embodiment, the above calculation formula is used to determine the minimum allowable load (D) of the lead compressor 4 at a specific compression ratio (P). This calculation method is a core strategy of the present invention in controlling the process of adding a compressor head in a multi-compressor chiller, aiming to ensure a smooth transition of the system when increasing the load by precisely controlling the load of the lead compressor 4 and avoiding the surge phenomenon.

[0074] The parameter explanations in the above formula are as follows: Compression ratio (P): represents the ratio of the compressor outlet pressure to the inlet pressure, and is an important parameter for measuring the working state of the compressor. In the refrigeration cycle, the change of the compression ratio directly affects the efficiency and operating stability of the compressor.

[0075] Minimum allowable load (D): It refers to the lowest load level that the leading compressor 4 can unload to on the premise of ensuring the stable operation of the compressor and avoiding surging. This value is crucial for the operation of adding a compressor head because it ensures that when starting the lagging compressor 5, the leading compressor 4 can maintain a safe and efficient operating state.

[0076] It can be understood that the term in the formula represents the square of the compression ratio P multiplied by 2.5. This term increases significantly with the increase of P, reflecting the non-linear influence of the compression ratio on the minimum allowable load, that is, the higher the compression ratio, the greater the unloading amplitude required for the leading compressor 4. The 7.5P term is the first-order term of the compression ratio P multiplied by 7.5, indicating that the compression ratio linearly affects the minimum allowable load. As the compression ratio increases, the required unloading amount also increases linearly. Adding the constant term 40, this constant is a reference value or to ensure that there is a basic unloading requirement for the formula under all working conditions.

[0077] In summary, this formula establishes a complex relationship between the compression ratio and the minimum allowable load by considering the quadratic and first-order terms of the compression ratio, as well as a constant term, to achieve dynamic and precise load adjustment. In actual operation, based on the calculated D value, the control system will correspondingly adjust the working state of the leading compressor 4, such as by adjusting the opening of the inlet guide vane, changing the motor speed, etc., to ensure that the compressor can effectively unload during the compressor head addition stage without entering an unstable state that may cause surging. This dynamic adjustment strategy improves the operating efficiency and stability of the entire refrigeration system.

[0078] According to some embodiments of the present invention, for the unloading operation performed by the control device on the leading compressor 4, the unloading of the leading compressor 4 can be achieved in various ways.

[0079] For example, frequency modulation unloading: By adjusting the frequency of the drive motor of the leading compressor 4, reducing its speed, thereby reducing the suction volume and output power of the compressor. This method is applicable to compressors with variable frequency control, can respond quickly, and the adjustment is smooth.

[0080] Another example is hot gas bypass: A bypass pipeline is set inside or outside the compressor to allow a part of the high-pressure hot gas to directly bypass the compression process and enter the subsequent cooling link directly. This can reduce the actual working load of the compressor without having to significantly adjust the inlet guide vane or speed, especially applicable to scenarios where rapid unloading is required.

[0081] Another example is fine-tuning of the inlet guide vane: Although the present invention emphasizes keeping the inlet guide vane fully open to maintain the speed control mode, in some cases, slightly adjusting the opening of the inlet guide vane (not fully closing) can also be used as an auxiliary unloading means, but it needs to be used with caution to avoid entering the mechanical control mode.

[0082] For another example, the electronic expansion valve 3 adjusts: By controlling the refrigerant amount entering the evaporator through the electronic expansion valve 3, the suction pressure of the compressor is indirectly affected, thereby achieving the purpose of load reduction. This method requires precise system control logic to maintain the balance of the entire refrigeration cycle.

[0083] In this way, through these diversified load reduction means, the control device can flexibly select the most suitable load reduction strategy according to the actual operating state of the leading compressor 4 and the system requirements, ensuring that during the operation of adding a compressor head, the leading compressor 4 can safely and efficiently transition to the state of working in cooperation with the lagging compressor 5.

[0084] In a specific embodiment of the present invention, in the first control device, the step of controlling the leading compressor 4 to unload to the minimum operable load specifically includes: calculating the minimum allowable speed of the leading compressor 4 according to the minimum allowable load, and controlling the speed of the leading compressor 4 to decrease to the minimum operable speed.

[0085] In this embodiment, first, based on the previously calculated minimum allowable load (D), the control device uses the characteristic curve of the compressor or a preset mapping relationship to calculate the minimum allowable speed corresponding to this minimum load. Speed is a key parameter directly affecting the output and working state of the compressor. By adjusting the speed, the suction volume and output power of the compressor can be effectively controlled.

[0086] Next, the control device issues an instruction to the drive system (such as a variable frequency drive) of the leading compressor 4 to precisely reduce the speed of the leading compressor 4 to the just calculated minimum allowable speed. This process may involve variable frequency drive technology, by adjusting the power supply frequency of the motor to change the compressor speed to achieve the purpose of precise load reduction.

[0087] During the entire load reduction process, the control system ensures that the inlet guide vane of the leading compressor 4 remains fully open. This is to avoid the compressor switching from the speed control mode to the mechanical control mode, because in the mechanical control mode, the response speed of controlling the suction volume by adjusting the inlet guide vane is slow, which is not conducive to surge control.

[0088] During the process of unloading the leading compressor 4 to the minimum allowable speed, the control system continuously monitors the operating state of the compressor, including but not limited to key parameters such as compression ratio, suction pressure, and discharge pressure, to ensure that the load reduction process is smooth and meets the expected goals, and at the same time creates the best conditions for the smooth start of the lagging compressor 5.

[0089] According to some embodiments of the present invention, a cut-in branch 6 is connected in parallel on both sides of the suction port and the discharge port of each compressor, and a cut-in valve 7 is provided on the cut-in branch 6.

[0090] In this embodiment, the configuration of the bypass branch 6 and the bypass valve 7 enables the system to dynamically adjust the load of each compressor according to the actual operating requirements. When it is necessary to adjust the refrigerating capacity of the system, the opening and closing of the bypass valve 7 can be controlled to quickly increase or decrease the suction or discharge volume of the compressor without changing the configuration of the main cycle, which greatly increases the flexibility and response speed of the system operation.

[0091] During the process of adding a compressor head, when it is necessary to start the lagging compressor 5, the bypass valve 7 on the discharge side of the leading compressor 4 can be opened first to directly bypass part of the discharge to the condenser, thereby quickly unloading the leading compressor 4 and keeping it in a stable state to avoid surge. At the same time, the lagging compressor 5 obtains appropriate starting conditions through the bypass valve 7 on its suction side, ensuring a moderate pressure difference during startup and a smoother startup process.

[0092] During maintenance or when a certain compressor fails and needs to be temporarily taken out of operation, the configuration of the bypass branch 6 and the bypass valve 7 allows the system to be quickly adjusted. By opening or closing the corresponding valves, the faulty compressor can be isolated, and at the same time, the load of the remaining compressors can be adjusted to ensure that the entire chiller can still maintain operation, improving the reliability and availability of the system.

[0093] The flexible control of the bypass valve 7 can also help the system achieve a higher energy efficiency ratio when operating at part load by precisely adjusting the operating conditions of each compressor. During low-load periods, by appropriately reducing the suction volume of a single compressor, it is possible to avoid a single compressor operating in a low-efficiency range, thereby improving the overall energy efficiency of the system.

[0094] In summary, this design, by introducing the parallel bypass branch 6 and the controllable bypass valve 7, not only enhances the smoothness of the multi-compressor chiller in the control of adding a compressor head, but also improves the overall adaptability, reliability and energy efficiency of the system, which is an important technological innovation for optimizing the operation strategy of large refrigeration systems.

[0095] According to some embodiments of the present invention, the second control device is specifically configured to: determine that the leading compressor 4 has been unloaded completely, and control the lagging compressor 5 to enter the startup process.

[0096] Wherein, when the startup process is started, the bypass valve 7 corresponding to the lagging compressor 5 is controlled to open; after the startup process ends, the bypass valve 7 corresponding to the lagging compressor 5 is controlled to close.

[0097] In this embodiment, the second control device first monitors the unloading process of the leading compressor 4 and confirms that it has been successfully unloaded to the pre-set minimum operable load. This process ensures that the leading compressor 4 is in a stable state, creating a suitable system operating condition for the addition of the lagging compressor 5, avoiding pressure fluctuations caused by sudden changes in operating conditions, and thus reducing the risk of surge.

[0098] Once the load reduction of the leading compressor 4 is completed, the second control device starts the pre-start sequence of the lagging compressor 5. This step includes, but is not limited to, turning on the power supply of the lagging compressor 5, pre-lubricating, and preparing for the initialization of the control system.

[0099] At the initial stage of the starting process of the lagging compressor 5, the second control device issues an instruction to open the cut-in valve 7 corresponding to the lagging compressor 5. The function of the cut-in valve 7 is to connect or isolate the air flow channel between the lagging compressor 5 and the system cycle. Opening the cut-in valve 7 can provide an initial suction path for the lagging compressor 5, and at the same time help maintain the total pressure ratio of the system within a safe range, facilitating the smooth start of the lagging compressor 5.

[0100] With the opening of the cut-in valve 7, the lagging compressor 5 starts to start officially, and its inlet guide vane or related control elements will be adjusted to a suitable position according to the instructions of the control device to adapt to the current pressure ratio conditions and load requirements of the system.

[0101] During the starting process, the second control device continuously monitors the operating parameters of the lagging compressor 5, such as rotational speed, suction and discharge pressures, current, etc., to ensure that the starting process meets expectations and no abnormal conditions occur. When the lagging compressor 5 starts and operates stably, the second control device will control its corresponding cut-in valve 7 to close. This means that the lagging compressor 5 has been fully integrated into the system cycle and works together with the leading compressor 4 to jointly bear the refrigeration or heating load of the system.

[0102] Through the above steps, the second control device effectively coordinates the load reduction of the leading compressor 4 and the start of the lagging compressor 5, not only ensuring the smoothness of the starting process, but also maximizing the energy efficiency and reliability of the system, which is one of the core mechanisms for the present invention to achieve efficient compressor head addition control.

[0103] According to some embodiments of the present invention, in the second control device, the steps of controlling the lagging compressor 5 to enter the starting process specifically include: During the starting process, control the inlet guide vane of the lagging compressor 5 to reach the fully open state, and adjust the load of the lagging compressor 5 to the minimum operable load.

[0104] It can be understood that when deciding to start the lagging compressor 5, the second control device first ensures that the inlet guide vane (IGV) of the lagging compressor 5 reaches the fully open state. This is a very crucial step because the fully open inlet guide vane can ensure that the compressor starts working with the highest efficiency and response speed, while avoiding the delay and instability factors caused by guide vane adjustment at the initial stage of starting.

[0105] Subsequently, the second control device adjusts the load of the lag compressor 5 to the previously calculated minimum operable load. This load value is usually calculated through a specific algorithm based on the operating state of the lead compressor 4 at that time and the system requirements, aiming to ensure that the back pressure faced by the lag compressor 5 during the startup phase is as small as possible, thereby reducing the startup difficulty and preventing surge phenomena.

[0106] Through the above control strategy, the lag compressor 5 can operate under very favorable working conditions at the initial stage of startup. The fully open inlet guide vane plus the carefully calculated minimum load not only facilitate the compressor to quickly and stably reach the designed operating state, but also help the entire unit achieve smooth energy transfer during the process of adding a compressor head, avoiding system disturbances caused by sudden load changes.

[0107] In summary, the control strategies in these embodiments effectively improve the control accuracy and stability of the system during the operation of adding a compressor head by precisely controlling the startup conditions and load distribution of the lag compressor 5, which is an important innovation point of the present invention in avoiding surge and improving system efficiency.

[0108] According to some embodiments of the present invention, the control device further includes a third control module, and the third control module is used to open the inlet guide vane of the lead compressor 4 to the fully open state when the inlet guide vane of the lead compressor 4 has not reached the fully open state.

[0109] Next, the control method, control device, and air-conditioning system proposed by the present invention will be described with reference to the accompanying drawings. Among them, before elaborating on the embodiments of the present invention in detail, the entire application scenario will be described first. The control method, control device, electronic device, and computer-readable storage medium of the air-conditioning system according to the embodiments of the present invention can be applied not only to the local air-conditioning system, but also to the cloud platform in the Internet field, or the cloud platform in other types of Internet fields, or can also be applied to third-party devices. Among them, the third-party devices may include various different types such as mobile phones, tablets, notebooks, in-vehicle computers, and other intelligent terminals.

[0110] Hereinafter, only the control method applicable to the air-conditioning system will be used as an example for illustration. It should be understood that the control method of the embodiments of the present invention can also be applicable to the cloud platform and third-party devices.

[0111] As Figure 2 shown, according to the control method of the air-conditioning system in the second aspect embodiment of the present invention, the air-conditioning system includes at least two compressors, wherein the compressor started first is used as the lead compressor 4 and the compressor started later is used as the lag compressor 5; the method includes: Step S1, detecting the operating state of the lead compressor 4; Step S2, when the inlet guide vane of the leading compressor 4 reaches the fully open state, obtain the compression ratio of the leading compressor 4; Step S3, according to the compression ratio of the leading compressor 4, perform a load reduction operation on the leading compressor 4 and keep the inlet guide vane in the fully open state; Step S4, determine that the load reduction of the leading compressor 4 is completed, and then start the lagging compressor 5.

[0112] According to the control method of the air-conditioning system according to the embodiment of the present invention, its specific working process is as follows: The system first operates, and one of the compressors is first started as the leading compressor 4. At this time, the built-in detection device 200 (such as a sensor or monitoring software) in the system starts to monitor the working state of the leading compressor 4 in real time, especially paying attention to the opening degree of its inlet guide vane.

[0113] When it is detected that the inlet guide vane of the leading compressor 4 is fully open, it indicates that the compressor is in a speed control mode with high efficiency and rapid response. At this time, the system further obtains the operating pressure ratio of the leading compressor 4 (that is, the ratio of the compressor outlet pressure to the inlet pressure), which is an important basis for judging the load state of the compressor.

[0114] According to the obtained compression ratio, the control device (such as a PLC or a microprocessor) uses a preset algorithm (such as the formula mentioned above) to calculate the minimum demand (Demand value) to which the leading compressor 4 should be unloaded, and then performs the load reduction operation. In this process, by adjusting the output of the leading compressor 4 (such as adjusting the speed through variable frequency drive), ensure that it is unloaded to the calculated minimum state without closing the inlet guide vane (keeping it fully open), so as to maintain the high-efficiency operation mode of the compressor and avoid having to switch to the mechanical control mode due to too high a compression ratio, which has a slower adjustment and is prone to surge.

[0115] Once the leading compressor 4 is successfully unloaded to a safe level and the system confirms that the load reduction process is completed, the control device will issue an instruction to start the lagging compressor 5. At this critical moment, the system may briefly open the cut-in valve 7 connecting the lagging compressor 5 to ensure that the system pressure it faces during startup is moderate and avoid excessive startup resistance.

[0116] After the lagging compressor 5 starts, it participates in the system refrigeration cycle together with the leading compressor 4. Through fine energy regulation, the two compressors work together to ensure the efficient and stable operation of the entire air-conditioning system, while avoiding the risk of surge caused by improper operation.

[0117] As Figure 3 shown, for the control device of the air-conditioning system according to the third aspect embodiment of the present invention, the air-conditioning system includes at least two compressors, wherein the first started compressor is used as the leading compressor 4 and the later started compressor is used as the lagging compressor 5; the device includes: An acquisition module 110, configured to acquire the compression ratio of the leading compressor 4 when the inlet guide vane of the leading compressor 4 reaches the fully open state; A first control module 120, configured to perform a load reduction operation on the leading compressor 4 according to the compression ratio of the leading compressor 4 and keep the inlet guide vane in the fully open state; A second control module 130, configured to start the lagging compressor 5 when it is determined that the load reduction of the leading compressor 4 is completed.

[0118] Figure 4 The schematic physical structure diagram of an electronic device is illustrated. As Figure 4 shown, the electronic device may include: a processor 810, a communications interface 820, a memory 830, and a communication bus 840. Among them, the processor 810, the communications interface 820, and the memory 830 communicate with each other through the communication bus 840. The processor 810 may call the logic instructions in the memory 830 to execute the control method of the air conditioning system, including: detecting the operating state of the leading compressor 4; acquiring the compression ratio of the leading compressor 4 when the inlet guide vane of the leading compressor 4 reaches the fully open state; performing a load reduction operation on the leading compressor 4 according to the compression ratio of the leading compressor 4 and keeping the inlet guide vane in the fully open state; starting the lagging compressor 5 when it is determined that the load reduction of the leading compressor 4 is completed.

[0119] In addition, when the logic instructions in the above-mentioned memory 830 are implemented in the form of a software functional unit and sold or used as an independent product, they may be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of this technical solution, may be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods in various embodiments of the present invention. The foregoing storage medium includes: various media such as a USB flash drive, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk, or an optical disc that can store program codes.

[0120] On the other hand, the present invention also provides a computer program product. The computer program product includes a computer program, which can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the control method of the air-conditioning system provided by each of the above methods, including: detecting the operating state of the leading compressor 4; obtaining the compression ratio of the leading compressor 4 when the inlet guide vane of the leading compressor 4 reaches the fully open state; performing a load reduction operation on the leading compressor 4 according to the compression ratio of the leading compressor 4 and keeping the inlet guide vane in the fully open state; determining that the load reduction of the leading compressor 4 is completed, and then starting the lagging compressor 5.

[0121] In another aspect, the present invention also provides a non-transitory computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it is implemented to execute the control method of the air-conditioning system provided by each of the above methods, including: detecting the operating state of the leading compressor 4; obtaining the compression ratio of the leading compressor 4 when the inlet guide vane of the leading compressor 4 reaches the fully open state; performing a load reduction operation on the leading compressor 4 according to the compression ratio of the leading compressor 4 and keeping the inlet guide vane in the fully open state; determining that the load reduction of the leading compressor 4 is completed, and then starting the lagging compressor 5.

[0122] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. A person of ordinary skill in the art can understand and implement it without creative labor.

[0123] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution, in essence, or the part that contributes to the prior art can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods of each embodiment or some parts of the embodiments.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements 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 the present invention.

Claims

1. An air conditioning system, characterized in that, Including: A first heat exchanger, a second heat exchanger, an electronic expansion valve, and at least two compressors. The suction port and the discharge port of each compressor are respectively connected to the first heat exchanger and the second heat exchanger. Among them, the compressor started first is used as the leading compressor, and the compressor started later is used as the lagging compressor; A detection device for detecting the operating state of the leading compressor; A control device, including an acquisition module, a first control module, and a second control module; The acquisition module is used to obtain the compression ratio of the leading compressor when the inlet guide vane of the leading compressor reaches the fully open state; the first control module is used to perform a load reduction operation on the leading compressor according to the compression ratio of the leading compressor and keep the inlet guide vane in the fully open state; the second control module is used to determine that the load reduction of the leading compressor is completed, and then start the lagging compressor.

2. The air-conditioning system according to claim 1, wherein, The first control device is specifically used for: Calculating the minimum allowable load of the leading compressor according to the compression ratio of the leading compressor, and controlling the leading compressor to unload to the minimum operable load; Wherein, the minimum operable load is the minimum load that the leading compressor can operate while keeping the inlet guide vane in the fully open state.

3. The air-conditioning system according to claim 2, characterized in that, In the step of calculating the minimum allowable load of the leading compressor according to the compression ratio of the leading compressor: If the compression ratio of the leading compressor is P and the minimum allowable load of the leading compressor is D, the calculation relationship between the compression ratio and the minimum allowable load is as follows: 。 4. The air conditioning system according to claim 2, characterized in that, In the first control device, the step of controlling the leading compressor to unload to the minimum operable load specifically includes: Calculating the minimum allowable speed of the leading compressor according to the minimum allowable load, and controlling the speed of the leading compressor to decrease to the minimum operable speed.

5. The air-conditioning system according to any one of claims 2 to 4, characterized in that, A cut-in branch is connected in parallel on both sides of the suction port and the discharge port of each compressor, and a cut-in valve is arranged on the cut-in branch.

6. The air conditioning system according to claim 5, characterized in that The second control device is specifically used for: Determining that the load reduction of the leading compressor is completed, and controlling the lagging compressor to enter the starting process; Among them, when the starting process starts, controlling the cut-in valve corresponding to the lagging compressor to open; after the starting process ends, controlling the cut-in valve corresponding to the lagging compressor to close.

7. The air conditioning system according to claim 6, characterized in that, In the second control device, the step of controlling the lagging compressor to enter the starting process specifically includes: During the starting process, controlling the inlet guide vane of the lagging compressor to reach the fully open state, and adjusting the load of the lagging compressor to the minimum operable load.

8. The air-conditioning system according to any one of claims 1 to 4, characterized in that, The control device further includes a third control module, and the third control module is used to open the inlet guide vane of the leading compressor to the fully open state when the inlet guide vane of the leading compressor does not reach the fully open state.

9. A control method for an air conditioning system, characterized in that, The air-conditioning system includes at least two compressors, wherein the compressor started first is used as the leading compressor, and the compressor started later is used as the lagging compressor; the method includes: Detecting the operating state of the leading compressor; When the inlet guide vane of the leading compressor reaches the fully open state, obtain the compression ratio of the leading compressor; According to the compression ratio of the leading compressor, perform a load reduction operation on the leading compressor and keep the inlet guide vane in the fully open state; When it is determined that the load reduction of the leading compressor is completed, start the lagging compressor.

10. A control device for an air conditioning system, characterized in that, The air conditioning system includes at least two compressors, where the compressor started first is used as the leading compressor and the compressor started later is used as the lagging compressor; the device includes: An acquisition module, configured to obtain the compression ratio of the leading compressor when the inlet guide vane of the leading compressor reaches the fully open state; A first control module, configured to perform a load reduction operation on the leading compressor according to the compression ratio of the leading compressor and keep the inlet guide vane in the fully open state; A second control module, configured to start the lagging compressor when it is determined that the load reduction of the leading compressor is completed.

Images