A modular chiller unit based on an air-suspension compressor and its control method

Abstract

This invention relates to the field of air-suspended chiller technology, and more particularly to a modular chiller based on an air-suspended compressor and its control method. The chiller adopts a modular design, consisting of multiple refrigeration modules integrating core components such as air-suspended variable frequency compressors, dual electronic expansion valves, and evaporators, along with a group control system. Operating data is collected in real time by temperature and flow sensors and speed feedback sensors at the inlet and outlet water manifolds, and the group control system coordinates and regulates the system. The control method focuses on precise load matching and optimal energy efficiency. Based on the collected data, it calculates the terminal cooling load and load rate, and determines the standard operating number of refrigeration modules by combining load rate time-series analysis and fluctuation characteristics. The modules are ranked according to full-condition energy efficiency and real-time energy efficiency. Finally, it monitors the compressor speed and, for cases where the speed deviates from the high-efficiency range, precisely adjusts the system by shutting down inefficient modules, transferring loads, locking safe speeds, and adjusting the opening of the electronic expansion valves, based on the current number of operating modules.

Description

Technical Field

[0001] This invention relates to the field of air-suspension chiller technology, and in particular to a modular chiller based on an air-suspension compressor and its control method. Background Technology

[0002] The refrigeration and air conditioning industry is rapidly developing towards higher efficiency, intelligence, and miniaturization. As the core energy-consuming equipment in central air conditioning systems, the operating efficiency of chillers directly determines the overall energy consumption level of the system. Against this backdrop, oil-free suspension compressor technologies such as magnetic levitation and air suspension have emerged. These technologies, by eliminating mechanical friction and achieving oil-free operation, significantly improve the part-load efficiency ratio of the unit, becoming cutting-edge technologies in the centrifugal chiller field. Compared to traditional screw chillers and fixed-frequency centrifugal chillers, suspension compressor technology enables the unit to maintain efficient operation over a wider load range, significantly reducing the total life-cycle operating cost.

[0003] Chinese Patent Publication No. CN208720551U discloses a modular evaporative condensing magnetic levitation chiller unit. The exhaust port of the magnetic levitation compressor is connected to the inlet of the evaporative condenser via a one-way valve. The outlet of the evaporative condenser is connected via pipes to the inlet of a ball valve, the subcooled liquid inlet of the economizer, and the inlet of the second electronic expansion valve. The outlet of the ball valve is connected via a pipe to the inlet of a dryer filter, and the outlet of the dryer filter is connected via a pipe to the cooling port of the magnetic levitation compressor. A sight glass is installed on the pipe between the outlet of the dryer filter and the cooling port of the magnetic levitation compressor. The subcooled liquid outlet of the economizer is connected via a pipe to the inlet of the first electronic expansion valve, and the outlet of the first electronic expansion valve is connected via a pipe to the working fluid inlet of the evaporator. The working fluid outlet of the evaporator is connected via a pipe to the suction port of the magnetic levitation compressor. This patent provides high efficiency in producing chilled water.

[0004] However, this existing technology still has the following shortcomings in practical applications:

[0005] First, magnetic levitation bearings rely on high-precision electronic control systems and dedicated cooling structures, making maintenance complex and costly. They are also sensitive to impurities in the refrigerant, which can affect bearing stability. In particular, the cost of magnetic levitation systems is too high in small-capacity units, limiting their application in medium and small-scale projects.

[0006] Secondly, the patent mainly focuses on the modular design of the system hardware structure, but it does not adequately address the intelligent control strategy of the unit during actual operation. The disclosed solution cannot dynamically adjust the unit's operating logic according to the real-time load changes at the terminal. In particular, it lacks a fine-grained control mechanism for the start-stop priority of refrigeration modules, load distribution, and compressor operating status when multiple modules are operating in combination. This leads to the unit being prone to mismatches between the number of operating modules and the current cooling load or individual compressors operating in the inefficient zone under actual partial load conditions, resulting in unnecessary energy waste.

[0007] Therefore, how to provide a method that can adapt to the characteristics of air suspension compressors and achieve precise coordinated control of multiple modules according to changes in terminal load, so as to solve the problems of low operating efficiency and poor load adaptability in the existing technology, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] To address this, the present invention provides a modular chiller unit based on an air-suspension compressor and its control method, which solves the technical problems of the lack of effective centralized control and optimized operation strategies in the prior art, the inability to dynamically adapt the unit's operating status according to the terminal cooling load, resulting in poor load matching, single module overload or multiple modules operating at low load, and ultimately causing low efficiency and high energy consumption in chilled water production.

[0009] To achieve the above objectives, in one aspect, the present invention provides a control method for a modular chiller unit based on an air-suspension compressor, comprising:

[0010] The return water temperature, supply water temperature and flow rate of chilled water are collected in real time by a sensor array to calculate the terminal cooling load.

[0011] The load factor is determined based on the ratio of terminal cooling load to the total design cooling capacity of the unit. A time-domain plot of the load factor is drawn, and the current time-domain subplot of the load factor and the corresponding historical time-domain subplot of the load factor are obtained.

[0012] Calculate the standard deviation of the current load and the standard deviation of the historical load, along with the historical load fluctuation, based on the current load rate time-domain subplot and the historical load rate time-domain subplot, respectively, to determine whether to combine the current load rate to determine the standard operating quantity of the current cooling module;

[0013] In response to adjusting the operation of the current refrigeration module, the real-time refrigeration coefficient and comprehensive part load performance coefficient of each refrigeration module are obtained to sort the priority operation order of each refrigeration module;

[0014] The module attributes of each cooling module are determined according to the priority order of operation and the standard number of operations, and each operating cooling module is assigned to the corresponding default load.

[0015] The operating cooling module includes a core cooling module and an auxiliary cooling module, while the non-operating cooling module includes a standby cooling module.

[0016] The compressor speed of the running refrigeration module is acquired in real time to determine whether the corresponding refrigeration module is in a high-efficiency operating state;

[0017] In response to the refrigeration module not operating efficiently, adjustment measures are determined based on the current number of operating modules and compressor speed.

[0018] The adjustment measures include adjusting the opening degree of the first electronic expansion valve and the opening degree of the second electronic expansion valve.

[0019] As a preferred technical solution for the control method of modular chiller units based on air suspension compressors, the load rate time-domain graph of the current moment is determined by tracing back a preset time period to the current load rate time-domain subgraph, and the historical load rate time-domain graph of the same period as the current load rate time-domain subgraph is extracted as the historical load rate time-domain subgraph.

[0020] As a preferred technical solution for the control method of modular chiller units based on air-suspension compressors, a standard deviation parameter is determined according to the historical load standard deviation, and the relationship between the current load standard deviation and the standard deviation parameter, as well as the historical load fluctuation, is used to determine whether to combine the current load rate to determine the number of operating refrigeration modules, including:

[0021] In response to the historical load fluctuation being greater than a preset fluctuation, it is determined that the current number of operating cooling modules will not be adjusted;

[0022] In response to the historical load fluctuation being less than or equal to a preset fluctuation, the system determines whether to combine the current load rate with the relationship between the current load standard deviation and the standard deviation parameter to determine the current number of operating cooling modules.

[0023] Based on the determination result that the current load standard deviation is greater than the standard deviation parameter, it is determined that the number of operating refrigeration modules will not be adjusted.

[0024] Based on the determination result that the current load standard deviation is less than or equal to the standard deviation parameter, the current load is determined to be stable, and the standard operating quantity of the current cooling module is determined in combination with the current load rate.

[0025] As a preferred technical solution for the control method of modular chiller units based on air suspension compressors, the operation of the current refrigeration module is adjusted in response to the difference between the standard operating quantity and the actual operating quantity, and the real-time refrigeration coefficient and comprehensive part load performance coefficient of each refrigeration module are obtained to sort the priority operation order of each refrigeration module.

[0026] As a preferred technical solution for the control method of a modular chiller unit based on an air-suspension compressor, the priority order of operation of each refrigeration module specifically includes:

[0027] The modules are sorted in descending order based on their combined part load performance coefficients to obtain a preliminary ranking result.

[0028] Determine the performance coefficient difference between any two adjacent refrigeration modules in the preliminary sorting results, and determine whether to adjust the sorting based on the performance coefficient difference and the real-time refrigeration coefficient.

[0029] In response to the performance coefficient difference being less than a preset difference, the system determines and adjusts the ranking of the two corresponding refrigeration modules based on the real-time refrigeration coefficient, and then adjusts and sorts the refrigeration coefficients of the two refrigeration modules in descending order.

[0030] As a preferred technical solution for the control method of a modular chiller unit based on an air-suspension compressor, the process of determining the module attributes of each refrigeration module and allocating each operating refrigeration module to its corresponding default load includes:

[0031] Based on the priority order of operation, the refrigeration module ranked first is determined to be the core refrigeration module;

[0032] The presence or absence of an auxiliary cooling module is determined based on the standard operating quantity, wherein:

[0033] If the standard operating quantity is greater than 1, then there is an auxiliary cooling module, and the cooling modules ranked 2 to n are identified as auxiliary cooling modules. 70% of the terminal cooling load is allocated to the core cooling module and 30% of the terminal cooling load is equally allocated to each auxiliary cooling module.

[0034] If the standard operating quantity is 1, then there is no auxiliary cooling module, and 100% of the terminal cooling load is allocated to the core cooling module;

[0035] The refrigeration modules other than the core refrigeration module and the auxiliary refrigeration module are designated as backup modules;

[0036] The module attributes include a core refrigeration module, an auxiliary refrigeration module, and a backup refrigeration module.

[0037] As a preferred technical solution for the control method of a modular chiller unit based on an air-suspension compressor, real-time acquisition of the compressor speed of the operating refrigeration module is used to determine whether the corresponding refrigeration module is in a high-efficiency operating state, including:

[0038] If the compressor speed is not in the high-efficiency speed range, then the corresponding refrigeration module is determined to be not in a high-efficiency operating state.

[0039] If the compressor speed is in the high-efficiency speed range, then the corresponding refrigeration module is determined to be in a high-efficiency operating state;

[0040] The high-efficiency speed range is determined based on the rated speed of the corresponding compressor.

[0041] As a preferred technical solution for the control method of modular chiller units based on air-suspended compressors, adjustment measures are determined based on the current number of operating units and compressor speed, including:

[0042] In response to the compressor speed being lower than the high-efficiency speed range, adjustment measures are determined based on the current number of operating units, wherein:

[0043] If the current number of running modules is not 1, the adjustment measure is to shut down the auxiliary cooling module that is ranked last and transfer its load proportionally to the core cooling module and the remaining auxiliary cooling modules.

[0044] If the current number of operations is 1, the adjustment measures are determined to be to maintain the operation of the core refrigeration module and lock its speed at 30% of the rated speed, and to adjust the opening of the first electronic expansion valve of the core refrigeration module to reduce the liquid supply to the evaporator.

[0045] As a preferred technical solution for the control method of modular chiller units based on air-suspended compressors, the adjustment measures, determined in conjunction with the current number of operating units and compressor speed, also include:

[0046] In response to the compressor speed being greater than the high-efficiency speed range, adjustment measures are determined based on the current number of operating units, wherein:

[0047] If a backup refrigeration module exists, the adjustment measure is to start the backup refrigeration module that is ranked first and share the load with the operating refrigeration module so that the speed of each compressor is reduced to less than or equal to the rated speed;

[0048] If there is no backup refrigeration module, the adjustment measures are to limit the maximum compressor speed of each operating refrigeration module to no more than 105% of the rated speed, and to adjust the opening of the second electronic expansion valve of each operating refrigeration module to increase the subcooling of the economizer.

[0049] On the other hand, the present invention also provides a modular chiller unit based on an air suspension compressor, comprising multiple refrigeration modules arranged in sequence and a group control system;

[0050] Each of the aforementioned refrigeration modules includes a first electronic expansion valve, an air-suspension variable frequency compressor, a frequency converter, a speed feedback sensor, an economizer, a one-way valve, a sight glass, a dryer filter, a ball valve, an evaporative condenser, an inlet manifold, an outlet manifold, an evaporator, and a second electronic expansion valve;

[0051] The inlet manifolds of adjacent refrigeration modules are connected by pipe clamps, and the outlet manifolds of adjacent refrigeration modules are connected by pipe clamps. The ends of the end inlet manifolds and the end outlet manifolds are respectively equipped with blind plates.

[0052] The group control system establishes communication connections with the frequency converter, speed feedback sensor, first electronic expansion valve, and second electronic expansion valve of each refrigeration module, respectively.

[0053] In addition, the group control system is signal-connected to a temperature sensor and a flow sensor installed in the inlet manifold, and is also signal-connected to a temperature sensor installed in the outlet manifold.

[0054] Compared with the prior art, the beneficial effects of the present invention are as follows: The modular chiller unit based on the air-suspension compressor provided by the embodiments of the present invention achieves flexible combination and expansion of unit capacity through the sequential arrangement of multiple refrigeration modules and the pipe clamp connection and blind flange sealing design of the manifold, adapting to the cooling capacity requirements of different scenarios, and has a compact structure and convenient installation; each refrigeration module integrates an air-suspension variable frequency compressor, dual electronic expansion valves and various functional components, and with the group control system and the comprehensive communication connection with the frequency converter, speed feedback sensor and temperature and flow sensors at the inlet and outlet water manifolds, it can collect unit operating data in real time and monitor the status of core components, providing reliable support for dynamic control; the group control system can make targeted adjustments to the compressor speed and electronic expansion valve opening based on the collected data, which not only ensures the stability and efficiency of unit operation, but also reduces energy consumption. At the same time, the modular design makes each module relatively independent, which facilitates later maintenance and repair, and extends the overall service life of the unit;

[0055] Furthermore, the control method provided in this embodiment of the invention calculates the terminal cooling load by collecting chilled water return temperature, supply water temperature and flow data, and combines the time domain analysis of load rate and load fluctuation characteristics to optimize the priority operation sequence and module attribute allocation of the refrigeration modules based on full-condition energy efficiency and real-time energy efficiency. At the same time, it monitors the compressor speed of the running refrigeration modules in real time to determine its high-efficiency operation status. For non-efficient operation scenarios, it adjusts the opening degree of the first electronic expansion valve and the second electronic expansion valve to adapt to the load demand, realizing dynamic and precise adaptation between load status and unit operation. This avoids frequent start-stop or inefficient operation of the refrigeration modules, improves the overall stability and energy efficiency of the unit, reduces energy consumption, and protects the core components of the equipment to extend the service life of the unit.

[0056] Furthermore, by dividing the day into time periods, selecting specific duration sub-plots of the current load rate, and matching multiple sets of historical load rate sub-plots from the same period, the consistency and reference validity of the load comparison scenarios are ensured. This allows the current load status to be accurately aligned with the stable patterns of the same period in history, providing reliable data support for subsequent stability assessments. At the same time, by setting a reasonable data collection frequency to draw continuous time-domain plots, the continuity and integrity of load data are ensured, avoiding judgment biases caused by missing data.

[0057] Furthermore, by calculating load-related statistical parameters and filtering out stable periods with adjustment basis based on historical load fluctuations, the current load standard deviation is compared with a reasonable tolerance range set based on historical data to accurately distinguish the degree of current load fluctuation. This avoids the problems of extra energy consumption, damage to bearing air film stability, and shortened equipment life caused by frequent start-stop of air-suspended compressors. Only when both the current and historical loads are stable are the standard operating quantities determined in combination with the load rate. This not only prevents operational disorder caused by adjusting the number of modules when the load fluctuates drastically, but also ensures accurate matching of load and number of modules under stable operating conditions. It maximizes energy saving while avoiding inefficient operating scenarios such as multiple modules under low load or single module overload, laying a solid foundation for subsequent module scheduling and parameter adjustment, and ultimately achieving synergistic optimization of unit operation stability, energy efficiency, and equipment protection.

[0058] Furthermore, by recalculating and updating this coefficient through real-time data collection, it is ensured that it accurately reflects the current energy-saving potential of the modules under all operating conditions. Based on this, a preliminary ranking is conducted to guarantee the overall energy efficiency of long-term operation. At the same time, by judging the difference of this coefficient between adjacent modules, modules with similar energy efficiency are adjusted a second time by introducing real-time cooling coefficients. This avoids the limitation of single-index ranking being unable to adapt to real-time operating conditions, and accurately selects the modules with better energy efficiency under the current operating conditions, improving the scientific nature and adaptability of the ranking. Based on the ranking results and standard operating quantities, the attributes of the three types of modules—core, auxiliary, and standby—are clarified. The modules with the best energy efficiency undertake the core load, the auxiliary modules cooperate, and the standby modules serve as backup. At the same time, reasonable load allocation is carried out to ensure that the operating modules can fully utilize their own energy efficiency advantages. This avoids energy loss caused by prioritizing the operation of inefficient modules, and through clear module role division and load allocation, each module performs its own function and cooperates to adapt to the terminal cooling load demand. This effectively prevents problems such as single module overload or multiple modules operating at low load caused by uneven load distribution, and provides solid scheduling support for the efficient and stable operation of subsequent units.

[0059] Furthermore, based on the speed characteristics and operating constraints of the air-suspension compressor, and combined with the current number of modules in operation, the problem of speed deviation from the high-efficiency range is specifically addressed to avoid energy loss and equipment damage caused by inefficient operation, ensuring that the unit dynamically adapts to the terminal cooling load demand:

[0060] When the compressor speed is below the high-efficiency range, the auxiliary refrigeration module at the bottom of the sequence is shut down first when multiple modules are running. The load rate of the remaining modules is increased by concentrating the load transfer, which pushes the speed back to the high-efficiency range. This reduces energy waste from low-load and inefficient operation, and ensures overall operating efficiency because the module with relatively poor energy efficiency is shut down. When a single module is running, the minimum high-efficiency speed is locked and the opening of the first electronic expansion valve is reduced. This avoids damage to the stability of the air suspension bearing film at low speeds, and achieves matching between cooling capacity and cooling load by precisely adjusting the evaporator liquid supply, thus maintaining stable and efficient operation of the module.

[0061] When the compressor speed is higher than the high-efficiency range, if a backup module is available, the highest-ranking high-efficiency backup module is started to distribute the load, allowing the speed of each module to drop back to a reasonable range. This solves the overload problem while continuing the high-efficiency module priority operation logic. When there is no backup module, the maximum speed is limited to avoid the risk of equipment wear and power consumption surges. At the same time, the opening of the second electronic expansion valve is increased to improve the subcooling of the economizer, supplementing the cooling capacity without increasing the speed and relieving the module load pressure.

[0062] The entire adjustment process is based on the operating characteristics of the air-suspension compressor, taking into account load adaptation, energy efficiency maintenance and equipment protection, effectively making up for possible load distribution deviations in the early module scheduling, and ensuring that the unit always operates in a highly efficient and stable state. Attached Figure Description

[0063] Figure 1 This is a schematic diagram of the modular chiller unit based on an air-suspension compressor according to an embodiment of the present invention;

[0064] Figure 2 This is a flowchart illustrating the control method of a modular chiller unit based on an air-suspension compressor according to an embodiment of the present invention.

[0065] Figure 3 A flowchart for determining adjustment measures in an embodiment of the present invention. Detailed Implementation

[0066] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0067] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0068] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0069] Please see Figure 1 As shown, it is a structural schematic diagram of a modular chiller unit based on an air-suspension compressor according to an embodiment of the present invention.

[0070] Understandably, existing technologies have proposed a modular evaporative condensing magnetic levitation chiller unit. However, magnetic levitation bearings rely on high-precision electronic control systems and dedicated cooling structures, resulting in complex and costly maintenance processes. Furthermore, they are sensitive to impurities in the refrigerant, which can easily affect bearing stability. In contrast, air-suspended compressors utilize oil-free air-floating bearings, eliminating mechanical friction, simplifying maintenance, and reducing costs. The oil-free design avoids refrigerant contamination and enhances stability. They also offer a wider frequency conversion range, superior energy efficiency under partial load, and better suitability for the dynamic load matching requirements of modular group control. Moreover, air-suspended compressors have fast start-stop response, low energy consumption, and adaptability to load fluctuation scenarios. Their more compact structure further optimizes the integration of modular units, reducing footprint and lifecycle costs. Therefore, this invention also provides a modular chiller unit based on an air-suspended compressor, comprising at least three sequentially arranged refrigeration modules and a group control system.

[0071] Each of the aforementioned refrigeration modules includes a first electronic expansion valve, an air-suspension variable frequency compressor, a frequency converter, a speed feedback sensor, an economizer, a one-way valve, a sight glass, a dryer filter, a ball valve, an evaporative condenser, an inlet manifold, an outlet manifold, an evaporator, and a second electronic expansion valve;

[0072] The exhaust port of the air-suspension variable frequency compressor is connected to the inlet of a one-way valve via a pipe. The outlet of the one-way valve is connected to the inlet of the evaporative condenser via a pipe. The outlet of the evaporative condenser is connected to the inlet of a ball valve, the subcooled liquid inlet of the economizer, and the inlet of the second electronic expansion valve via pipes. The outlet of the ball valve is connected to the inlet of the dryer filter via a pipe. The outlet of the dryer filter is connected to the cooling port of the air-suspension variable frequency compressor via a pipe through a sight glass. The outlet of the second electronic expansion valve is connected to the liquid inlet of the economizer via a pipe. The return gas port of the economizer is connected to the air supply port of the air-suspension variable frequency compressor via a pipe. The subcooled liquid outlet of the economizer is connected to the inlet of the first electronic expansion valve via a pipe. The outlet of the first electronic expansion valve is connected to the working fluid inlet of the evaporator via a pipe. The working fluid outlet of the evaporator is connected to the suction port of the air-suspension variable frequency compressor via a pipe. The chilled water inlet of the evaporator is connected to the inlet manifold via a pipe. The chilled water outlet of the evaporator is connected to the outlet manifold via a pipe.

[0073] The inlet manifolds of adjacent refrigeration modules are connected by pipe clamps, and the outlet manifolds of adjacent refrigeration modules are connected by pipe clamps. The ends of the end inlet manifolds and the end outlet manifolds are respectively equipped with blind plates.

[0074] The group control system establishes communication connections with the frequency converter, speed feedback sensor, first electronic expansion valve, and second electronic expansion valve of each refrigeration module, respectively.

[0075] Furthermore, the group control system is signal-connected to a temperature sensor and a flow sensor installed in the inlet manifold, and also to a temperature sensor installed in the outlet manifold. It can be understood that the temperature sensor in the inlet manifold monitors the return water temperature (the temperature of the chilled water returning to the unit after use at the end, which is higher), and the temperature sensor in the outlet manifold monitors the supply water temperature (the temperature of the chilled water supplied to the end after cooling by the unit, which is lower). In practice, the flow path of the chilled water is: end return water → inlet manifold → evaporator (cooling) → outlet manifold → end supply water.

[0076] Please see Figures 2-3 The figures shown are, respectively, a step diagram of the control method for a modular chiller unit based on an air-suspension compressor according to an embodiment of the present invention and a flowchart of determining adjustment measures according to an embodiment of the present invention. This embodiment provides a control method for a modular chiller unit based on an air-suspension compressor, including:

[0077] Step S1: Collect the return water temperature, supply water temperature and flow rate data of chilled water in real time through the sensor group to calculate the terminal cooling load;

[0078] In implementation, the terminal cooling load = chilled water density × chilled water specific heat capacity at constant pressure × chilled water volumetric flow rate × chilled water supply and return temperature difference; it can be understood that the chilled water density is usually approximated as 1000 kg / m³, the chilled water specific heat capacity at constant pressure is usually approximated as 4.18 kJ / (kg·℃), the chilled water volumetric flow rate is obtained by a flow sensor, the unit is m³ / h, and the chilled water supply and return temperature difference (unit: ℃) = return water temperature - supply water temperature;

[0079] Step S2: Determine the load factor based on the ratio of terminal cooling load to the total design cooling capacity of the unit, draw the load factor time domain diagram, and obtain the current load factor time domain sub-diagram and the corresponding historical load factor time domain sub-diagram;

[0080] In step S2, the load rate time domain graph for a preset duration (usually 30 minutes to 1 hour, preferably 30 minutes to reduce the number of calculations) is determined as the current load rate time domain subgraph, and the historical load rate time domain graph for the same period as the current load rate time domain subgraph is extracted as the historical load rate time domain subgraph. It can be understood that the time period is divided according to 0:00 to 24:00 of the day. In an implementation, if the current time is 13:45, then the horizontal axis of the corresponding current load rate time domain subgraph is 13:15 to 13:45 of the day. In an implementation, a current load rate time domain subgraph should correspond to 10 to 15 historical load rate time domain subgraphs (usually 10 historical load rate time domain subgraphs are selected), that is, the load rate time domain graphs corresponding to the time period of 13:15 to 13:45 in the past 10 days are all recorded as historical load rate time domain subgraphs.

[0081] Understandably, the load factor time-domain plot is plotted with time as the horizontal axis (unit: min) and load factor as the vertical axis (unit: %), and a continuous load factor time-domain plot is drawn at a data collection frequency of 0.5 minutes / data point to 1 minute / data point.

[0082] Step S3: Calculate the current load standard deviation based on the current load rate time domain subgraph, and calculate the historical load average, historical load average deviation and historical load standard deviation based on the historical load rate time domain subgraph respectively. Determine the historical load fluctuation based on the ratio of the historical load average deviation to the historical load average to determine whether to combine the current load rate to determine the standard operating quantity of the current cooling module.

[0083] In step S3, a standard deviation parameter is determined based on the historical load standard deviation, and a determination is made based on the relationship between the current load standard deviation and the standard deviation parameter, and the historical load fluctuation, to determine whether to combine the current load rate to determine the current number of operating cooling modules, including:

[0084] In response to the historical load fluctuation being greater than the preset fluctuation, it is determined that the number of operating refrigeration modules will not be adjusted. It is understood that the preset fluctuation is usually ≤0.1, preferably 0.1. The smaller the historical load fluctuation, the more stable the long-term operation of the cooling load at the end of the corresponding period, which provides a basis for adjusting the number of refrigeration modules according to the load rate. The larger the historical load fluctuation, the more likely the load is to fluctuate during that period, and the number of modules should not be adjusted for the time being.

[0085] In response to the historical load fluctuation being less than or equal to a preset fluctuation, the system determines whether to combine the current load rate with the relationship between the current load standard deviation and the standard deviation parameter to determine the current number of operating cooling modules.

[0086] Based on the determination result that the current load standard deviation is greater than the standard deviation parameter, it is determined that the number of operating refrigeration modules will not be adjusted.

[0087] Based on the determination result that the current load standard deviation is less than or equal to the standard deviation parameter, the current load is determined to be stable, and the standard operating quantity of the current cooling module is determined in combination with the current load rate.

[0088] Understandably, by comparing the current load standard deviation with the standard deviation parameter, the stability of the current load is judged. If the current load standard deviation is greater than the standard deviation parameter, it indicates that the current load fluctuation is more drastic than the historical load fluctuation, and the number of operating cooling modules should not be adjusted. If the current load standard deviation is less than or equal to the standard deviation parameter, it means that the current load is as stable as the historical load. The standard number of operating cooling modules can be determined by combining the load rate to avoid frequent start-stop and achieve precise load matching and energy saving.

[0089] It is understandable that when an air-suspension compressor starts up, it needs to establish an air film (i.e., suspend the rotor with high-pressure gas to avoid friction). This process generates no-load power consumption (approximately 15% to 20% of full-load power consumption), and frequent start-stop cycles can lead to decreased air film stability and shortened bearing life.

[0090] In practice, the standard deviation parameter is typically 1.05 to 1.1 times the historical load standard deviation. This ensures load matching during adjustments while also acknowledging the energy-saving potential arising from minor fluctuations. Understandably, if the current load standard deviation is less than the standard deviation parameter, it indicates that the current load fluctuation is only slightly higher than the historical stable level, which is still a controllable minor fluctuation and allows for the adjustment of the number of modules. If the current standard deviation exceeds the standard deviation parameter, it indicates that the fluctuation exceeds the normal range of the historical stable period. In this case, adjustments should be temporarily suspended to avoid frequent start-stop cycles.

[0091] In practice, when the current load rate is ≤30%, only one cooling module is started (i.e., standard operating quantity = 1). When the current load rate is between 30% and 70%, 2 to n cooling modules are started (in this embodiment, 2 cooling modules are started, n = maximum standard operating quantity = total number of cooling modules - 1 = 2). When the current load rate is >70%, all cooling modules are started (in this embodiment, standard operating quantity = 3).

[0092] Step S4: In response to the difference between the standard operating quantity and the actual operating quantity, adjust the operation of the current refrigeration module, and obtain the real-time refrigeration coefficient and comprehensive part load performance coefficient of each refrigeration module to sort the priority operation order of each refrigeration module.

[0093] In practice, the manufacturer will calibrate the Integrated Part Load Performance (IPLV) through operating condition testing and provide parameters (which can be directly referred to in the product manual). However, these are theoretical calibration values. In actual operation, the IPLV will change dynamically due to environmental factors, equipment wear and tear, and load fluctuations. The COP under each load can be collected in real time and recalculated. That is, the group control system collects the module cooling capacity and power consumption under different load rates, calculates the corresponding COP, and then updates the IPLV in real time according to the weighted formula to adapt to the actual operating status.

[0094] In step S4, sorting the priority operation order of each of the refrigeration modules specifically includes:

[0095] Step S41: Sort the refrigeration modules in descending order according to their Integrated Part Load Performance Factor (IPLV) to obtain a preliminary sorting result. It can be understood that the Integrated Part Load Performance Factor is the average energy efficiency of the module under all operating conditions, which directly determines the energy-saving potential of the corresponding refrigeration module in the long-term operation. Therefore, sorting in descending order according to IPLV is prioritized to ensure the lowest total energy consumption over the entire cycle.

[0096] Step S42: Determine the performance coefficient difference of the comprehensive part load performance coefficient of any two adjacent refrigeration modules in the preliminary sorting result, and determine whether to adjust the sorting based on the performance coefficient difference and the real-time refrigeration coefficient. It can be understood that if the IPLV difference between adjacent modules is large, it means that the energy efficiency of the two modules under the whole operating conditions is significantly different, and the module with higher IPLV has a clear advantage and does not need to be adjusted. If the difference is small, it means that the energy efficiency under the whole operating conditions is similar. At this time, IPLV can no longer accurately distinguish the instantaneous energy efficiency under the current operating conditions, and it is necessary to make a second judgment based on the instantaneous energy efficiency (COP) under the current load operating conditions.

[0097] Step S43: In response to the performance coefficient difference being less than a preset difference, the module is sorted and adjusted based on the real-time cooling coefficient, and the cooling coefficients of the two corresponding cooling modules are sorted in descending order. It can be understood that COP can accurately reflect the actual energy-saving effect of the module under the current operating conditions. When the IPLV difference is small, adjusting the sorting by COP can avoid prioritizing the operation of modules with slightly higher IPLV but significantly lower COP under the current operating conditions, ensuring that the sorting takes into account both the whole cycle and the real-time load requirements, thus improving the control accuracy.

[0098] In practice, the actual operating value of the IPLV of the air-suspended chiller unit is usually 4.0 to 6.0. In the comparison of energy efficiency indicators of chiller units, the IPLV difference of 0.1 to 0.3 is usually used as the judgment standard for similar energy efficiency levels. When the preset difference is set to 0.2, it can effectively filter out the small fluctuations of IPLV to avoid ineffective adjustments, and accurately capture the scenarios where IPLV is close but COP is significantly different. It is the preferred balance value between full-condition energy efficiency and real-time energy efficiency, and is suitable for the load fluctuation characteristics of most industrial and commercial scenarios.

[0099] Step S5: Determine the module attributes of each cooling module according to the priority operation order and the standard operation quantity, and assign each running cooling module to the corresponding default load;

[0100] The module attributes include a core cooling module, an auxiliary cooling module, and a standby cooling module. The core cooling module and the auxiliary cooling module are both operating cooling modules, while the standby cooling module is a non-operating cooling module.

[0101] In step S5, the process of determining the module attributes of each cooling module and assigning each operating cooling module to its corresponding default load includes:

[0102] Step S51: Determine the refrigeration module ranked first as the core refrigeration module according to the priority operation order;

[0103] Step S52: Determine whether an auxiliary cooling module exists based on the standard operating quantity, wherein:

[0104] If the standard operating quantity is greater than 1, then there is an auxiliary cooling module, and the cooling modules ranked 2 to n are identified as auxiliary cooling modules. 70% of the terminal cooling load is allocated to the core cooling module and 30% of the terminal cooling load is equally allocated to each auxiliary cooling module.

[0105] If the standard operating quantity is 1, then there is no auxiliary cooling module, and 100% of the terminal cooling load is allocated to the core cooling module;

[0106] Step S53: Identify the refrigeration modules other than the core refrigeration module and the auxiliary refrigeration module as backup modules.

[0107] Step S6, obtaining the compressor speed of the operating refrigeration module in real time through a speed feedback sensor to determine whether the corresponding refrigeration module is in a high-efficiency operating state, including:

[0108] If the compressor speed is not in the high-efficiency speed range, then the corresponding refrigeration module is determined to be not in a high-efficiency operating state.

[0109] If the compressor speed is in the high-efficiency speed range, then the corresponding refrigeration module is determined to be in a high-efficiency operating state;

[0110] The high-efficiency speed range is determined based on the rated speed of the corresponding compressor; in practice, the high-efficiency speed range is 0.3 times the rated speed to the rated speed.

[0111] Step S7: In response to the refrigeration module not operating efficiently, determine adjustment measures based on the current number of operating modules and compressor speed, including:

[0112] In response to the compressor speed being lower than the high-efficiency speed range (when the compressor speed is below 30% of the rated speed, it indicates that the current refrigeration module load is insufficient, causing the speed to be forced to decrease; in this case, it is necessary to force the operating module back to the high-efficiency range by redistributing the load or locking the lowest high-efficiency speed to avoid a sudden drop in energy efficiency and equipment risk caused by low speed), adjustment measures are determined based on the current number of operating units, including:

[0113] If the current number of operating modules is not 1, the adjustment measure is to shut down the last-ranked auxiliary refrigeration module and transfer its load proportionally to the core refrigeration module and the remaining auxiliary refrigeration modules. It is understandable that when multiple modules are running in parallel, the load of a single refrigeration module is distributed too small, resulting in the speed being lower than the high-efficiency range. In this case, the last-ranked auxiliary refrigeration module should be shut down first, as shutting it down will have the least impact on the overall energy efficiency. At the same time, its load can be concentrated and transferred to the core refrigeration module and the remaining auxiliary refrigeration modules. By reducing the number of modules and concentrating the load, the load rate of the remaining operating refrigeration modules can be increased, driving the compressor speed back to the high-efficiency speed range and avoiding low-load and inefficient operation of multiple modules.

[0114] If the current number of operating modules is 1, the adjustment measures are determined to be to maintain the operation of the core refrigeration module and lock its speed at 30% of the rated speed, and to reduce the opening of the first electronic expansion valve of the core refrigeration module to reduce the liquid supply to the evaporator. It is understood that when only one refrigeration module is running, it is impossible to concentrate the load by shutting down the module. Locking the speed at 30% of the rated speed (i.e., the lower limit of the high-efficiency speed range) avoids further speed reduction, which would cause instability of the air film of the air suspension bearing (low speed is prone to air film rupture and damage to the bearing), and maintains the minimum high efficiency. After locking the speed, it is necessary to reduce the liquid supply to the evaporator by reducing the opening of the first electronic expansion valve, so that the module's cooling capacity is precisely matched with the terminal cooling load. This avoids the compressor running with liquid due to a fixed speed but excessive liquid supply, or insufficient liquid supply leading to a cooling capacity gap, ensuring that a single refrigeration module can operate stably and efficiently at the minimum high efficiency speed.

[0115] In response to the compressor speed exceeding the high-efficiency speed range (compressor speed exceeding the rated speed indicates insufficient total cooling capacity of the currently operating modules, resulting in overload of the operating refrigeration modules. In this case, it is necessary to add high-efficiency modules to share the load or limit the safe speed and energy efficiency compensation to avoid overload damage to the equipment while maintaining stable unit operation), adjustment measures are determined based on the current number of operating modules, including:

[0116] If there are standby refrigeration modules (i.e., the current number of operating modules is less than the total number of refrigeration modules), the adjustment measure is to start the standby refrigeration module with the highest priority (i.e., adjust it to an auxiliary refrigeration module) and share the load with the operating refrigeration modules so that the speed of each compressor drops to less than or equal to the rated speed. It can be understood that after adding a module, part of the load of the overloaded module is transferred, so that the load rate of all operating modules decreases and the compressor speed naturally drops back to within the rated speed, which solves the problem of single module overload and maintains the high energy efficiency level of the entire system.

[0117] If there are no spare refrigeration modules (i.e., the current number of operating modules equals the total number of refrigeration modules), the adjustment measures are to limit the maximum compressor speed of each operating refrigeration module to no more than 105% of its rated speed, and to increase the opening of the second electronic expansion valve of each operating refrigeration module to improve the subcooling of the economizer. It is understandable that no new modules are available at this time, but in order to meet the cooling load and protect the equipment from compressor damage due to overload, the maximum speed must be locked within 105% of the rated speed. This reserves a small amount of load redundancy to cover the cooling load demand, while controlling the extent of exceeding the rated speed (when the air-suspended compressor runs above the rated speed, the motor power consumption will increase by the cube of the speed, and the excessive air film pressure of the bearing will easily lead to wear. The 105% limit can effectively avoid these risks). Adjusting the opening of the second electronic expansion valve can improve the subcooling of the economizer, that is, increase the cooling capacity of a unit of refrigerant without increasing the speed. The higher the subcooling, the higher the heat exchange efficiency of the refrigerant in the evaporator, and the greater the total cooling capacity of the unit at the same speed, thereby relieving the load pressure of a single module and keeping the speed stable within the safe threshold.

[0118] In practice, the process of adjusting the opening of the first electronic expansion valve and the second electronic expansion valve includes:

[0119] Step A1: Establish a database of the mapping relationship between compressor speed and electronic expansion valve opening. The database stores the optimal opening values ​​of the first and second electronic expansion valves corresponding to different speed ranges. The optimal opening values ​​are calibrated through operating condition tests before the unit leaves the factory.

[0120] Step A2: The group control system matches the corresponding optimal opening value from the database based on the current real-time compressor speed, and adjusts the valve opening in an adjustment step of 5% per cycle.

[0121] Step A3: After adjustment, continuously collect the compressor speed and evaporator supply and return liquid status. If the speed does not return to the high-efficiency range within 30 seconds, repeatedly adjust the valve opening until the high-efficiency operation requirements are met.

[0122] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention; various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A control method for a modular chiller unit based on an air-suspension compressor, characterized in that, include: The return water temperature, supply water temperature and flow rate of chilled water are collected in real time by a sensor array to calculate the terminal cooling load. The load factor is determined based on the ratio of terminal cooling load to the total designed cooling capacity of the unit. A load factor time-domain diagram is plotted, and the load factor time-domain diagram that traces back a preset time period from the current moment is determined as the current load factor time-domain sub-diagram. The historical load factor time-domain diagrams of the same period as the current load factor time-domain sub-diagram are extracted as the historical load factor time-domain sub-diagrams. Calculate the current load standard deviation and historical load standard deviation and historical load fluctuation based on the current load rate time-domain subplot and the historical load rate time-domain subplot, respectively. Determine the standard deviation parameter based on the historical load standard deviation. Then, determine whether to combine the current load rate with the current load rate to determine the number of operating cooling modules based on the relationship between the current load standard deviation and the standard deviation parameter, and the historical load fluctuation. In response to the historical load fluctuation being greater than a preset fluctuation, it is determined that the current number of operating cooling modules will not be adjusted; In response to the historical load fluctuation being less than or equal to a preset fluctuation, the system determines whether to combine the current load rate with the relationship between the current load standard deviation and the standard deviation parameter to determine the current number of operating cooling modules. Based on the determination result that the current load standard deviation is greater than the standard deviation parameter, it is determined that the number of operating refrigeration modules will not be adjusted. Based on the determination result that the current load standard deviation is less than or equal to the standard deviation parameter, the current load is determined to be stable, and the standard operating quantity of the current cooling module is determined in combination with the current load rate. In response to adjusting the operation of the current refrigeration module, the real-time refrigeration coefficient and comprehensive part load performance coefficient of each refrigeration module are obtained to sort the priority operation order of each refrigeration module; The module attributes of each cooling module are determined according to the priority order of operation and the standard number of operations, and each operating cooling module is assigned to the corresponding default load. The operating cooling module includes a core cooling module and an auxiliary cooling module, while the non-operating cooling module includes a standby cooling module. The compressor speed of the running refrigeration module is acquired in real time to determine whether the corresponding refrigeration module is in a high-efficiency operating state; In response to the refrigeration module not operating efficiently, adjustment measures are determined based on the current number of operating modules and compressor speed. The adjustment measures include adjusting the opening degree of the first electronic expansion valve and the opening degree of the second electronic expansion valve.

2. The control method for a modular chiller unit based on an air-suspension compressor according to claim 1, characterized in that, In response to the difference between the standard operating quantity and the actual operating quantity, the operation of the current refrigeration module is adjusted, and the real-time refrigeration coefficient and comprehensive part load performance coefficient of each refrigeration module are obtained to sort the priority operation order of each refrigeration module.

3. The control method for a modular chiller unit based on an air-suspension compressor according to claim 2, characterized in that, The specific steps for prioritizing the operation of each of the aforementioned refrigeration modules include: The modules are sorted in descending order based on their combined part load performance coefficients to obtain a preliminary ranking result. Determine the performance coefficient difference between any two adjacent refrigeration modules in the preliminary sorting results, and determine whether to adjust the sorting based on the performance coefficient difference and the real-time refrigeration coefficient. In response to the performance coefficient difference being less than a preset difference, the system determines and adjusts the ranking of the two corresponding refrigeration modules based on the real-time refrigeration coefficient, and then adjusts and sorts the refrigeration coefficients of the two refrigeration modules in descending order.

4. The control method for a modular chiller unit based on an air-suspension compressor according to claim 1, characterized in that, The process of determining the module attributes of each cooling module and assigning each operating cooling module to its corresponding default load includes: Based on the priority order of operation, the refrigeration module ranked first is determined to be the core refrigeration module; The presence or absence of an auxiliary cooling module is determined based on the standard operating quantity, wherein: If the standard operating quantity is greater than 1, then there is an auxiliary cooling module, and the cooling modules ranked 2 to n are identified as auxiliary cooling modules, and 70% of the terminal cooling load is allocated to the core cooling module and 30% of the terminal cooling load is equally allocated to each auxiliary cooling module. If the standard operating quantity is 1, then there is no auxiliary cooling module, and 100% of the terminal cooling load is allocated to the core cooling module; The refrigeration modules other than the core refrigeration module and the auxiliary refrigeration module are designated as backup modules; The module attributes include a core refrigeration module, an auxiliary refrigeration module, and a backup refrigeration module.

5. The control method for a modular chiller unit based on an air-suspension compressor according to claim 1, characterized in that, Real-time acquisition of the compressor speed of the operating refrigeration module to determine whether the corresponding refrigeration module is operating in a high-efficiency state includes: If the compressor speed is not in the high-efficiency speed range, then the corresponding refrigeration module is determined to be not in a high-efficiency operating state. If the compressor speed is in the high-efficiency speed range, then the corresponding refrigeration module is determined to be in a high-efficiency operating state; The high-efficiency speed range is determined based on the rated speed of the corresponding compressor.

6. The control method for a modular chiller unit based on an air-suspension compressor according to claim 1, characterized in that, Adjustment measures will be determined based on the current number of operating units and compressor speed, including: In response to the compressor speed being lower than the high-efficiency speed range, adjustment measures are determined based on the current number of operating units, wherein: If the current number of running modules is not 1, the adjustment measure is to shut down the auxiliary cooling module that is ranked last and transfer its load proportionally to the core cooling module and the remaining auxiliary cooling modules. If the current number of operations is 1, the adjustment measures are determined to be to maintain the operation of the core refrigeration module and lock its speed at 30% of the rated speed, and to adjust the opening of the first electronic expansion valve of the core refrigeration module to reduce the liquid supply to the evaporator.

7. The control method for a modular chiller unit based on an air-suspension compressor according to claim 1, characterized in that, The adjustment measures, determined based on the current number of operating units and compressor speed, also include: In response to the compressor speed being greater than the high-efficiency speed range, adjustment measures are determined based on the current number of operating units, wherein: If a backup refrigeration module exists, the adjustment measure is to start the backup refrigeration module that is ranked first and share the load with the operating refrigeration module so that the speed of each compressor is reduced to less than or equal to the rated speed; If there is no backup refrigeration module, the adjustment measures are to limit the maximum compressor speed of each operating refrigeration module to no more than 105% of the rated speed, and to adjust the opening of the second electronic expansion valve of each operating refrigeration module to increase the subcooling of the economizer.

8. A modular chiller unit based on an air-suspension compressor, characterized in that, The control method of the modular chiller unit based on the air suspension compressor according to any one of claims 1-7, wherein the modular chiller unit based on the air suspension compressor includes a plurality of refrigeration modules arranged in sequence and a group control system. Each of the aforementioned refrigeration modules includes a first electronic expansion valve, an air-suspension variable frequency compressor, a frequency converter, a speed feedback sensor, an economizer, a one-way valve, a sight glass, a dryer filter, a ball valve, an evaporative condenser, an inlet manifold, an outlet manifold, an evaporator, and a second electronic expansion valve; The inlet manifolds of adjacent refrigeration modules are connected by pipe clamps, and the outlet manifolds of adjacent refrigeration modules are connected by pipe clamps. The ends of the end inlet manifolds and the end outlet manifolds are respectively equipped with blind plates. The group control system establishes communication connections with the frequency converter, speed feedback sensor, first electronic expansion valve, and second electronic expansion valve of each refrigeration module. In addition, the group control system is signal-connected to a temperature sensor and a flow sensor installed in the inlet manifold, and is also signal-connected to a temperature sensor installed in the outlet manifold.

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