A magnetic levitation centrifugal chiller

Abstract

The present invention provides a magnetic levitation centrifugal chiller, belonging to the field of refrigeration equipment. The magnetic levitation centrifugal chiller of the present invention includes a magnetic levitation compressor, a condenser and an evaporator. The magnetic levitation compressor is connected to the condenser through an exhaust pipeline, and the condenser is connected to the magnetic levitation compressor and the evaporator respectively through a liquid supply pipeline assembly. It further includes a natural process control module, which determines the energy efficiency health index of the chiller, calculates the energy efficiency health index, and is used to dynamically adjust the starting sequence of multiple magnetic levitation compressors in the chiller. The natural process control module is electrically connected to the central controller. By setting the natural process control module, a multi-dimensional energy efficiency health index model is constructed, which comprehensively considers the actual energy efficiency ratio, evaporation efficiency, compressor aging coefficient, pressure fluctuation and environmental humidity correction term to dynamically adjust the compressor starting sequence.

Description

Technical Field

[0001] The present invention relates to the technical field of refrigeration equipment, and more particularly, to a magnetic levitation centrifugal chiller. Background Art

[0002] The magnetic levitation centrifugal chiller has a large cooling capacity range and a high energy efficiency ratio. It is a large-scale chiller. The magnetic levitation centrifugal compressor uses magnetic bearings and can operate without oil, so that no oil film is formed in the heat exchange system of the chiller, avoiding heat resistance loss, further improving the energy efficiency of the chiller system, canceling the oil circuit and simplifying the system configuration, and improving the operation reliability of the system. The magnetic levitation centrifugal chiller mainly consists of a magnetic levitation centrifugal compressor, an evaporator, a condenser, a throttling device, etc. The core of the magnetic levitation centrifugal chiller is the magnetic levitation centrifugal compressor, which mainly consists of components such as an impeller, a motor, magnetic levitation bearings, displacement sensors, bearing controllers, and motor drivers.

[0003] When traditional chillers operate with multiple compressors in coordination, they lack a real-time energy efficiency evaluation and dynamic adjustment mechanism, resulting in some compressors running inefficiently for a long time or uneven load distribution, and the overall energy efficiency decreases. The regulation of traditional electronic expansion valves depends on fixed thresholds or empirical parameters and cannot quickly respond to changes in refrigerant demand caused by sudden changes in compressor frequency, resulting in system subcooling, superheating, or pressure fluctuations. At the same time, under high-temperature or high-load conditions, the refrigerant enthalpy increase in a single-stage compression cycle is insufficient, resulting in too high a compressor discharge temperature or insufficient suction superheat, limited cooling capacity, and decreased compressor reliability. Summary of the Invention

[0004] The purpose of the present invention is to provide a magnetic levitation centrifugal chiller to solve the problems in the prior art mentioned in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A magnetic levitation centrifugal chiller, comprising a magnetic levitation compressor, a condenser, and an evaporator. The magnetic levitation compressor is connected to the condenser through an exhaust pipe, and the condenser is connected to the magnetic levitation compressor and the evaporator respectively through a liquid supply pipe assembly. It further includes a natural process control module. The natural process control module determines the energy efficiency health index of the chiller, calculates the energy efficiency health index, and is used to dynamically adjust the startup sequence of multiple magnetic levitation compressors in the chiller. The natural process control module is electrically connected to the central controller.

[0007] In a preferred technical solution of the present invention, the natural process control module determines the energy efficiency health index of the chiller, calculates the energy efficiency health index, and is used to dynamically adjust the startup sequence of multiple magnetic levitation compressors in the chiller, including:

[0008] Determine the energy efficiency health indicators of the chiller, where the energy efficiency health indicators are determined by the compressor aging indicators and the real-time energy efficiency indicators, and the energy efficiency health indicators are refrigerant flow rate, refrigeration capacity, compressor input power, evaporator inlet and outlet water temperatures, condenser inlet water temperature, compressor mechanical efficiency, and the cumulative operating time of the compressor;

[0009] Construct an energy efficiency health index model, and input the energy efficiency health indicators into the energy efficiency health index model to calculate the energy efficiency health index , (i = 1,......, N) represents the energy efficiency health index of the i-th compressor, which respectively includes an energy efficiency correction term, an evaporation efficiency correction term, and an equipment aging and equal wear correction term, and satisfies the following relationship:

[0010] Among them, is the actual energy efficiency ratio, is the refrigeration capacity, is the compressor input power; is the rated energy efficiency ratio, and N is the number of compressors;

[0011] is the actual evaporation efficiency, is the temperature difference between the inlet and outlet water of the evaporator, that is , is the evaporator inlet water temperature, is the evaporator outlet water temperature;

[0012] is the actual refrigerant flow rate, among which, , is the enthalpy difference of the evaporator, is the rated refrigerant flow rate, is the rated temperature difference; is the rated evaporation efficiency; is the energy efficiency ratio weight, indicating the load rate Dynamically adjust the influence weight of the energy efficiency ratio; is the temperature correction coefficient, characterizing the influence degree of the condensation temperature on the evaporation efficiency, is the condenser inlet water temperature;

[0013] is the compressor aging coefficient, that is, the compressor mechanical efficiency, and the value is , is the pressure fluctuation correction coefficient, is the pressure fluctuation rate, is the cumulative operating time difference, and μ represents the time difference attenuation coefficient;

[0014] Dynamically adjust the compressor startup sequence. Obtain the EHI value of each compressor through real-time calculation. Generate a priority list in descending order according to the EHI values of each compressor. Dynamically adjust the compressor startup sequence according to the energy efficiency priority. The priority is sorted based on historical energy efficiency data and updated every 24 hours.

[0015] Further preferably, the compressor aging coefficient satisfies the relationship:

[0016]

[0017] Wherein, is the maximum allowable efficiency loss; represents the cumulative operating time, represents the compressor design life, > 1 indicates that the efficiency decay rate increases with time.

[0018] Further preferably, considering the influence of the environmental humidity index on the energy efficiency health index, an environmental humidity correction term D is added. When calculating the energy efficiency health index, multiply the original energy efficiency health index model by the environmental humidity correction term D, which satisfies the following relationship:

[0019]

[0020] Set the environmental humidity threshold to 60%. The value of the environmental humidity correction coefficient satisfies the following relationship:

[0021]

[0022] Wherein, represents the humidity correction coefficient, represents the normalized value of the environmental relative humidity; when the environmental temperature RH ≤ 60%, the influence of humidity on the heat exchange efficiency of the condenser is small and can be ignored. .

[0023] In the preferred technical solution of the magnetic levitation centrifugal chiller of the present invention, the step of dynamically adjusting the compressor startup sequence further includes determining the optimal number of operating units and load distribution, including:

[0024] Calculate the total refrigeration demand required by the chiller under actual working conditions , which satisfies the relational expression:

[0025]

[0026] Traverse all possible compressor combinations, from 1 unit to all N units, and evaluate the comprehensive energy efficiency score of each combination , select the compressor combination that not only meets the total refrigeration demand but also maximizes the energy efficiency. The comprehensive energy efficiency score satisfies the following relational expression:

[0027]

[0028] Among them, is the maximum refrigerating capacity; is the number of start / stop cycles; is the start / stop loss coefficient; group is the number of compressor combinations;

[0029] According to the screening conditions , determine the total refrigerating capacity coverage requirement of the selected combination; select the combination with the highest comprehensive energy efficiency score that meets the screening conditions as the optimal combination;

[0030] After selecting the optimal combination, distribute the load according to the energy efficiency health index ratio of each compressor, limit the single-machine load rate. To ensure the stability and maximum efficiency of the system, the load distribution satisfies the following relationship:

[0031]

[0032] Among them, is the load of the j-th compressor in the optimal combination, j = 1,..., k; k represents the number of compressors in the optimal combination; the denominator term represents the total energy efficiency potential of all compressors in the optimal combination; the numerator term represents the energy efficiency potential of the j-th compressor in the combination.

[0033] In the preferred technical solution of the magnetic levitation centrifugal chiller of the present invention, the chiller further includes a refrigerant frequency conversion module, the refrigerant frequency conversion module is arranged between the evaporator and the magnetic levitation compressor, one end of the refrigerant frequency conversion module is sequentially connected to the evaporator through a first electronic expansion valve and a ball valve, and the other end is sequentially connected to the magnetic levitation compressor through a solenoid valve and a ball valve; on the pipeline of the first high-pressure refrigerant outlet of the condenser, a ball valve, a dryer filter, a solenoid valve, a ball valve and a sight glass are sequentially arranged, and the pipeline between the refrigerant frequency conversion module and the magnetic levitation compressor is connected to the pipeline of the first high-pressure refrigerant outlet of the condenser;

[0034] The exhaust pipeline is used to connect the exhaust port of the magnetic levitation compressor and the high-pressure refrigerant inlet of the condenser. A check valve is arranged at a position close to the exhaust port on the exhaust pipeline, and a butterfly valve is arranged at a position close to the high-pressure refrigerant inlet of the condenser;

[0035] The liquid supply pipeline assembly includes an economizer which has different first and second circuits. The third high-pressure refrigerant outlet of the condenser is connected to the economizer port of the magnetic levitation compressor through a pipeline with a second electronic expansion valve and via the second circuit of the economizer. The second high-pressure refrigerant outlet of the condenser is connected to the low-pressure refrigerant inlet of the evaporator through the first circuit of the economizer. On the output pipeline of the first circuit, a ball valve, a third electronic expansion valve and a ball valve are sequentially arranged, and then through the low-pressure refrigerant outlet of the evaporator, it is connected to the suction port of the magnetic levitation compressor through a pipeline with a butterfly valve;

[0036] The first electronic expansion valve, the second electronic expansion valve and the third electronic expansion valve are all electrically connected to the central controller, and their opening degrees are controlled by the central controller.

[0037] Further preferably, a bypass inlet is also provided on the evaporator, a bypass outlet is also provided on the condenser, and a load balancing valve is provided on the pipeline between the bypass inlet of the evaporator and the bypass outlet of the condenser.

[0038] Further preferably, on the bypass pipeline of the exhaust port of the magnetic levitation compressor, it is sequentially connected to the pressure relief port of the evaporator through a cut-in valve and a ball valve.

[0039] The preferred technical solution of the magnetic levitation centrifugal chiller of the present invention for the opening degree control of the first electronic expansion valve and the second electronic expansion valve and the economizer enthalpy increase includes:

[0040] Establish a refrigerant demand prediction model, and determine the input parameters: compressor real-time efficiency , the change rate of real-time efficiency , the superheat SH at the evaporator outlet, the condensation pressure and the evaporation pressure , calculate the predicted refrigerant flow rate, satisfying the relationship:

[0041]

[0042] Wherein, is the current steady-state flow rate; is the flow-frequency correction coefficient, with the unit of kg / ( ); is the superheat correction coefficient, with the unit of kg / ( );

[0043] Dynamically control the opening degree of the electronic expansion valve, and set the initial opening degree K 初 =K b + , is the opening degree response gain coefficient, K b is the current opening degree, is the current refrigerant flow rate, is the designed refrigerant flow rate;

[0044] Perform closed-loop correction on the superheat degree. When the measured superheat degree SH deviates from the target value, fine-tune the opening degree through the PID algorithm;

[0045] Set the condition for starting the enthalpy increase. When the condensation pressure threshold is greater than or equal to 15%-20% of the designed condensation pressure value and the compressor frequency threshold is greater than or equal to 80% of the rated compressor frequency start the economizer gas injection;

[0046] When the compressor exhaust temperature threshold is greater than or equal to the temperature resistance warning threshold of the magnetic levitation compressor , and the superheat degree threshold is less than or equal to the critical protection value of the superheat degree target value , forcibly enable the enthalpy increase;

[0047] Calculate the opening degree of the second electronic expansion valve in the economizer branch :

[0048]

[0049] where, is the condensation pressure; is the intermediate pressure of the economizer, that is, the gas injection point pressure; is the rated design pressure; is the compressor exhaust temperature, is the reference temperature, is the adjustment coefficient;

[0050] Compensate and adjust the first electronic expansion valve in the main circuit:

[0051] where, is the opening degree of the second electronic expansion valve in the economizer branch, in %; is the adjustment amount of the opening degree of the first electronic expansion valve in the main circuit, in %;

[0052] Adjust the frequencies of the high-pressure and low-pressure stage compressors through the economizer gas injection pressure to satisfy the following relationship:

[0053]

[0054] where, is the frequency of the high-pressure stage compressor, in Hz; is the frequency of the low-pressure stage compressor, in Hz; is the target value of the intermediate pressure, in kPa; is the frequency adjustment coefficient, with the unit of Hz / kPa.

[0055] In summary, the beneficial effects of the present invention are as follows:

[0056] The chiller of the present invention is provided with a natural process control module, constructs a dynamic energy efficiency health index EHI model, dynamically optimizes the compressor startup sequence and load distribution by real-time evaluating multi-dimensional parameters such as real-time energy efficiency ratio, compressor aging, evaporation efficiency, environmental humidity, and pressure fluctuation, and avoids the long-term operation of inefficient compressors; combined with the optimal compressor combination strategy, through the start-stop loss coefficient and energy efficiency potential ratio distribution, on the premise of meeting the load demand, the high-efficiency compressor combination is preferentially called, and the overall energy efficiency is significantly improved compared with the traditional equal-load strategy; finally, combined with the refrigerant demand prediction and the coordinated control of the electronic expansion valve, through the flow-frequency correction coefficient and the superheat correction coefficient, the feedforward and feedback composite control of the refrigerant flow is realized, the response speed is improved, and the energy loss caused by refrigerant subcooling or superheating is reduced. By combining dynamic energy efficiency optimization, precise refrigerant control and equipment protection mechanism, the present invention realizes the comprehensive improvement of the magnetic levitation centrifugal chiller in terms of energy efficiency, reliability, environmental adaptability and intelligence, and provides an efficient, stable and sustainable solution for the industrial refrigeration field. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 is the system schematic diagram of the magnetic levitation centrifugal chiller of the present invention;

[0058] Figure 2 is the system control diagram of the magnetic levitation centrifugal chiller of the present invention;

[0059] Markings in the figure: 1 - magnetic levitation compressor, 10 - exhaust port, 101 - right branch, 102 - left branch, 11 - suction port, 12 - economizer port, 2 - condenser, 20 - high-pressure refrigerant inlet, 21 - first high-pressure refrigerant outlet, 22 - second high-pressure refrigerant outlet, 23 - third high-pressure refrigerant outlet, 24 - bypass outlet, 3 - evaporator, 30 - low-pressure refrigerant inlet, 31 - low-pressure refrigerant outlet, 32 - pressure relief port, 33 - bypass inlet, 4 - economizer port, 41 - liquid inlet, 42 - liquid outlet, 43 - coolant inlet, 44 - cooling gas outlet, 5 - refrigerant frequency conversion module, 6.1 - first electronic expansion valve, 6.2 - second electronic expansion valve, 6.3 - third electronic expansion valve, 7 - check valve, 8 - butterfly valve, 9 - cut-in valve, 13 - ball valve, 14 - dryer filter, 15 - solenoid valve, 16 - sight glass, 17 - load balance valve. DETAILED DESCRIPTION OF THE INVENTION

[0060] The specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments given here are only for explaining and interpreting the present invention and cannot be used to limit the present invention.

[0061] It should be noted that many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention may have other embodiments and variations, and therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0062] As Figures 1 to 2 shown, a magnetic levitation centrifugal chiller includes a magnetic levitation compressor 1, a condenser 2 and an evaporator 3. The magnetic levitation compressor 1 is connected to the condenser 2 through an exhaust pipeline, and the condenser 2 is connected to the magnetic levitation compressor 1 and the evaporator 3 respectively through a liquid supply pipeline assembly; it further includes a natural process control module. The natural process control module determines the energy efficiency health index of the chiller, calculates the energy efficiency health index, and is used to dynamically adjust the starting sequence of multiple magnetic levitation compressors in the chiller. The natural process control module is electrically connected to the central controller. Multiple magnetic levitation compressors 1 of the chiller operate in parallel, and cluster energy efficiency management is realized through the central controller, which is applicable to large-scale industrial refrigeration scenarios.

[0063] In a preferred embodiment of this embodiment, the natural process control module determines the energy efficiency health index of the chiller, calculates the energy efficiency health index, and is used to dynamically adjust the starting sequence of multiple magnetic levitation compressors in the chiller, including:

[0064] Determine the energy efficiency health index of the chiller. The energy efficiency health index is determined by the compressor aging index and the real-time energy efficiency index. The energy efficiency health index is refrigerant flow rate, refrigeration capacity, compressor input power, evaporator inlet and outlet water temperature, condenser inlet water temperature, compressor mechanical efficiency, and the cumulative operating time of the compressor;

[0065] Construct an energy efficiency health index model, and input the energy efficiency health index into the energy efficiency health index model to calculate the energy efficiency health index , (i = 1,......, N) represents the energy efficiency health index of the i-th compressor, which respectively includes an energy efficiency correction term, an evaporation efficiency correction term, and an equipment aging and balanced wear correction term, and satisfies the following relationship:

[0066]

[0067] Among them, is the actual energy efficiency ratio, is the refrigeration capacity, is the compressor input power; is the rated energy efficiency ratio, that is, the design value under standard working conditions; N is the number of compressors;

[0068] is the actual evaporation efficiency, is the temperature difference between the inlet and outlet water of the evaporator, that is , is the inlet water temperature of the evaporator, is the outlet water temperature of the evaporator;

[0069] is the actual refrigerant flow rate, where , is the enthalpy difference of the evaporator; is the rated refrigerant flow rate, is the rated temperature difference; is the rated evaporation efficiency; is the energy efficiency ratio weight, indicating the load rate dynamically adjusts the influence weight of the energy efficiency ratio; is the temperature correction coefficient, characterizing the influence degree of the condensation temperature on the evaporation efficiency, is the inlet water temperature of the condenser;

[0070] is the compressor aging coefficient, i.e., the mechanical efficiency of the compressor, with a value , is the pressure fluctuation correction coefficient, is the pressure fluctuation rate, suppressing the influence of pressure fluctuation on the energy efficiency. The greater the fluctuation, the smaller the coefficient; is the cumulative operating time difference, and μ represents the time difference decay coefficient.

[0071] Regarding the temperature correction coefficient The relational expression is , and the relational expression shows exponential decay: at the initial stage of temperature rise, β increases rapidly; the growth rate slows down in the high-temperature range, fitting the decay trend of the actual heat transfer efficiency; when the condensation inlet water temperature ≥25°C, the temperature correction coefficient is enabled, indicating that the higher the inlet water temperature of the condenser, the more significant the influence of the evaporation efficiency on the EHI. Among them, the reference temperature of 25°C is the inlet water temperature of the condenser under typical design conditions, and at this time, the evaporation efficiency is in the best state and no correction is required. When =25°C, takes a value of 0; when >25°C, correction is triggered to avoid excessive intervention under low-temperature conditions, and at the same time, a safety boundary is determined. The maximum correction intensity is 0.15, restricting the maximum correction amplitude to prevent overshoot from causing system oscillation.

[0072] Regarding the pressure fluctuation correction coefficient The relational expression is , is dimensionless, indicating the suppression of the influence of pressure fluctuation on the energy efficiency health index (EHI), The larger it is, the more significantly the EHI value decays, reducing the priority of this compressor. The smaller it is, the EHI value is not affected; where represents the standard condensation pressure under the design conditions; is the pressure volatility rate, representing the standard deviation of the exhaust pressure within 10 minutes; 0.5 is an empirical constant, serving as the volatility sensitivity coefficient, dimensionless, obtained through experimental calibration; can eliminate the influence of dimensions, adapt to different units. Through experimental calibration, when = 0.2, = 0.91, indicating a 9% decay; when = 0.4, = 0.83, indicating a 17% decay.

[0073] Regarding the cumulative operation time difference is the difference between the operation time of the i-th compressor and the average operation time. The specific relationship is:

[0074]

[0075] In the above equal wear correction term, the value of the time difference decay coefficient is μ = 0.001. The higher the cumulative operation time of the compressor is above the average value ( > 0), the lower its EHI value, and it is preferentially reduced in use; avoid long-term high-load operation of a single compressor to extend the overall life.

[0076] Dynamically adjust the starting order of the compressors, calculate the EHI values of each compressor in real time. According to the EHI values of each compressor, generate a priority list in descending order, and dynamically adjust the starting order of the compressors according to the energy efficiency priority. The priority is sorted based on historical energy efficiency data and updated every 24 hours. Among them, the higher the EHI value, the higher the priority, and it is preferentially started or kept running.

[0077] Furthermore, in a preferred implementation, the compressor aging coefficient satisfies the relationship:

[0078] [[ID=4">

[0079] where is the maximum allowable efficiency loss; represents the cumulative operation time, represents the design life of the compressor, > 1 indicates that the efficiency decay rate increases with time.

[0080] Under standard maintenance conditions, the decay range of the mechanical efficiency of the compressor within the life cycle is 15% - 25%. Take 0.2 as the design value to limit the maximum efficiency loss and ensure that the compressor can still maintain its basic performance at the end of its life; according to the historical test data of the compressor, the wear rate of the compressor shows an accelerating trend with the running time, and the exponent Taking a value of 1.5 is more in line with the actual aging curve compared to the linear model.

[0081] In a further preferred embodiment, considering the influence of the environmental humidity index on the energy efficiency health index, an environmental humidity correction term D is added. When calculating the energy efficiency health index, multiply the original energy efficiency health index model by the environmental humidity correction term D, satisfying the following relationship:

[0082]

[0083] Set the environmental humidity threshold to 60%, and the value of the environmental humidity correction coefficient satisfies the following relationship:

[0084]

[0085] Among them, represents the humidity correction coefficient, represents the normalized value of the environmental relative humidity; when the environmental temperature RH ≤ 60%, the heat exchange efficiency of the condenser 2 is less affected by humidity and can be ignored. .

[0086] When RH > 60%, the moisture content in the air increases significantly, resulting in the following problems: condensation occurs on the surface of the condenser 2, forming a water film that hinders the heat exchange between air and refrigerant; the density of humid air increases, reducing the heat dissipation efficiency of the fan. The relationship is shown as a linear relationship. For every 1% increase in humidity, the EHI decreases by 0.12 / 40 = 0.003. Among them, 0.12 represents the maximum derating coefficient, indicating that when RH = 100%, the EHI value decreases by 12%, that is, the upper limit of energy efficiency loss; 40 represents the humidity range span (60% - 100%), and the correction coefficient is allocated proportionally.

[0087] The above value of δ(RH) is designed through threshold segmentation, linear slope, and maximum derating, balancing the model accuracy and calculation complexity. According to the ASHRAE standard and the design specifications of industrial refrigeration equipment, 60% humidity is the critical point for a significant drop in energy efficiency. In addition, in areas with frequent humidity fluctuations, such as tropical climates, an exponential smoothing algorithm can be introduced to perform short-term average filtering on δ(RH) to avoid frequent adjustment and achieve dynamic adjustment.

[0088] In the preferred embodiment of the magnetic levitation centrifugal chiller in this embodiment, the step of dynamically adjusting the compressor startup sequence further includes determining the optimal number of operating units and load distribution, including:

[0089] Calculate the total refrigeration demand required by the chiller under actual working conditions , satisfying the relation:

[0090]

[0091] Traverse all possible compressor combinations, from 1 unit to all N units, and evaluate the comprehensive energy efficiency score of each combination , select the compressor combination that not only meets the total refrigeration demand but also maximizes the energy efficiency. The comprehensive energy efficiency score satisfies the following relation:

[0092]

[0093] where, is the maximum refrigerating capacity; is the start-stop times; is the start-stop loss coefficient, representing the energy efficiency loss of the single start-stop of the i th compressor. The value is calibrated through experiments and ranges from 0.05 to 0.1; group is the number of compressor combinations;

[0094] According to the screening condition , determine the total refrigeration capacity coverage demand of the selected combination; select the combination that meets the screening condition and has the highest comprehensive energy efficiency score as the optimal combination;

[0095] After selecting the optimal combination, distribute the load according to the energy efficiency health index ratio of each compressor, and limit the single-machine load rate. To ensure system stability and maximum efficiency, the load distribution satisfies the following relation:

[0096]

[0097] where, is the load of the jth compressor in the optimal combination, j = 1,..., k; k represents the number of compressors in the optimal combination; the denominator term represents the total energy efficiency potential of all compressors in the optimal combination; the numerator term represents the energy efficiency potential of the jth compressor in the combination.

[0098] Through the above evaluation of energy efficiency potential and trade-off of start-stop loss, select the compressor combination that covers the demand and has the highest comprehensive energy efficiency, and then distribute the load according to the energy efficiency ratio to achieve the optimal operation of the system. This design balances energy efficiency, equipment life and stability, and is especially suitable for industrial scenarios with frequent load fluctuations.

[0099] Preferred embodiment of the magnetic levitation centrifugal chiller in this embodiment. The chiller further includes a refrigerant frequency conversion module 5, which is arranged between the evaporator 3 and the magnetic levitation compressor 1. One end of the refrigerant frequency conversion module 5 is connected to the evaporator 3 through a first electronic expansion valve 6.1 and a ball valve 13 in sequence, and the other end is connected to the magnetic levitation compressor 1 through a solenoid valve 15 and a ball valve 13 in sequence; on the pipeline of the high-pressure refrigerant first outlet 21 of the condenser 2, a ball valve 13, a dryer filter 14, a solenoid valve 15, a ball valve 13 and a sight glass 16 are arranged in sequence, and the pipeline between the refrigerant frequency conversion module 5 and the magnetic levitation compressor 1 is connected to the pipeline of the high-pressure refrigerant first outlet 21 of the condenser 2;

[0100] The exhaust pipeline is used to connect the exhaust port 10 of the magnetic levitation compressor 1 and the high-pressure refrigerant inlet 20 of the condenser 2. A check valve 7 is arranged at a position close to the exhaust port 10 on the exhaust pipeline, and a butterfly valve 8 is arranged at a position close to the high-pressure refrigerant inlet 20 of the condenser 2; Refer to Figure 1 , the exhaust pipeline is the right branch 101 arranged on one side of the exhaust port 10;

[0101] The liquid supply pipeline assembly includes an economizer. The economizer has different first and second circuits. The high-pressure refrigerant third outlet 23 of the condenser 2 is connected to the economizer port 4 of the magnetic levitation compressor 1 through a pipeline with a second electronic expansion valve 6.2 and through the second circuit of the economizer. The high-pressure refrigerant second outlet 22 of the condenser 2 is connected to the low-pressure refrigerant inlet 30 of the evaporator 3 through the first circuit of the economizer. On the output pipeline of the first circuit, a ball valve 13, a third electronic expansion valve 6.3 and a ball valve 13 are arranged in sequence, and then through the low-pressure refrigerant outlet 31 of the evaporator 3, it is connected to the suction port 11 of the magnetic levitation compressor 1 through a pipeline with a butterfly valve 8;

[0102] The economizer has a liquid inlet 41, a liquid outlet 42, a coolant inlet 43 and a cooling gas outlet 44. The pipeline passing through the liquid inlet 41 and the liquid outlet 42 is the second circuit, and the pipeline passing through the coolant inlet 43 and the cooling gas outlet 44 is the first circuit;

[0103] The first electronic expansion valve 6.1, the second electronic expansion valve 6.2 and the third electronic expansion valve 6.3 are all electrically connected to the central controller, and their opening degrees are controlled by the central controller. The first electronic expansion valve 6.1, the second electronic expansion valve 6.2 and the third electronic expansion valve 6.3 form an electronic expansion valve group, which is electrically connected to the central controller, and its opening degree is controlled by the central controller. The refrigerant frequency conversion module 5 is electrically connected to the central controller.

[0104] Further preferred embodiments are as follows. A bypass inlet 33 is also provided on the evaporator 3, and a bypass outlet 24 is also provided on the condenser 2. A load balancing valve 17 is provided on the pipeline between the bypass inlet 33 of the evaporator 3 and the bypass outlet 24 of the condenser 2.

[0105] Further preferred embodiments are as follows. A bypass pipeline of the exhaust port 10 of the magnetic levitation centrifuge is sequentially connected to the pressure relief port 32 of the evaporator 3 through a cut-in valve 9 and a ball valve 13. The bypass pipeline mentioned here is the left branch 102 provided on one side of the exhaust port 10.

[0106] Preferred embodiments of the magnetic levitation centrifugal chiller in this embodiment include the opening control and economizer enthalpy increase of the first electronic expansion valve 6.1 and the second electronic expansion valve 6.2:

[0107] Establish a refrigerant demand prediction model and determine the input parameters: real-time efficiency of the compressor , rate of change of real-time efficiency , superheat SH at the outlet of the evaporator 3, condensing pressure and evaporation pressure , and calculate the predicted refrigerant flow rate, satisfying the relationship:

[0108]

[0109] where is the current steady-state flow rate; is the flow-frequency correction coefficient, with the unit of kg / ( ), takes values from 0.05 to 0.1 kg / ( ); is the superheat correction coefficient, with the unit of kg / ( ), takes values from 0.02 to 0.05 kg / ( );

[0110] Dynamically control the opening of the electronic expansion valve. The initial opening is set as K 初 = K b + ; is the opening response gain coefficient, K b is the current opening, is the current refrigerant flow rate, is the designed refrigerant flow rate;

[0111] where the opening response gain coefficient , as the response intensity of the control of the opening adjustment of the electronic expansion valve to the flow prediction deviation, takes values from 0.5 to 1.0;

[0112] Perform closed-loop correction on superheat. When the measured superheat SH deviates from the target value, the opening is fine-tuned through the PID algorithm.

[0113] Set the enthalpy increase starting condition, when the condensation pressure threshold Greater than or equal to the condensing pressure design value 15%-20% of ≥15%-20% , and the compressor frequency threshold Greater than or equal to 80% of the rated frequency of the compressor When ≥80% , start the economizer to replenish gas;

[0114] When the compressor exhaust temperature threshold Greater than or equal to the magnetic levitation compressor temperature warning threshold , and the overheat threshold Critical protection value less than or equal to the superheat target value ;

[0115] Calculate the 6.2 degree opening of the second electronic expansion valve of the economizer branch :

[0116]

[0117] in, is the condensation pressure; is the middle pressure of the economizer, i.e. the pressure at the gas filling point; is the rated design pressure; is the compressor exhaust temperature, is the reference temperature, is the adjustment factor;

[0118] The above is driven by pressure difference to replenish gas. Indicates condensing pressure Between the economizer and the intermediate pressure The greater the pressure difference, the stronger the demand for air supply, and the need to increase the opening of the electronic expansion valve to increase the air supply flow. Standardize the pressure difference and perform normalization to avoid dimension effects; correct by temperature difference: Indicates the compressor exhaust temperature With reference temperature The higher the exhaust temperature, the greater the risk of system overheating. Air injection is needed to lower the temperature, thus increasing the electronic expansion valve opening. The denominator 10 normalizes the temperature difference. For example, a temperature difference of 10°C corresponds to a coefficient adjustment step of 1.

[0119] The above adjustment coefficient They are the influence weights for balancing the pressure difference and temperature difference respectively, obtained through historical data or experimental calibration: As the weight of the pressure difference term, it reflects the dominant influence of the pressure difference on the gas replenishment volume; The weight of the temperature difference term, a secondary correction term to prevent overheating risks.

[0120] Compensation adjustment for the first electronic expansion valve 6.1 of the main circuit:

[0121]

[0122] Among them, is the opening degree of the second electronic expansion valve 6.2 of the economizer branch, in %; it determines the size of the gas replenishment flow rate; is the adjustment amount of the opening degree of the first electronic expansion valve 6.1 of the main circuit, in %; the coefficient -0.1 indicates that the reduction amount of the opening degree of the main circuit electronic expansion valve accounts for 10% of the opening degree of the gas replenishment circuit electronic expansion valve. Gas replenishment in the economizer will increase the total refrigerant flow rate of the system, which may cause over - flow in the evaporator ③. By reducing the opening degree of the main circuit electronic expansion valve, the gas replenishment flow rate is offset to maintain the stable flow rate of the evaporator ③.

[0123] The above drives the adjustment of the gas replenishment flow rate through the pressure difference and temperature difference, and the main circuit is synchronously compensated to achieve the dynamic balance of the refrigerant flow rate.

[0124] Adjust the frequencies of the high - pressure and low - pressure compressors through the economizer gas replenishment pressure to meet the following relationship:

[0125]

[0126] Among them, is the frequency of the high - pressure compressor, in Hz; is the frequency of the low - pressure compressor, in Hz; is the intermediate pressure target value, in kPa, usually the optimal gas replenishment pressure of the economizer under the design conditions; is the frequency adjustment coefficient, in Hz / kPa, reflecting the frequency adjustment amount corresponding to the unit pressure deviation;

[0127] When the intermediate pressure is higher than the target value , it indicates that the gas replenishment volume is too large or the load of the low - pressure compressor is insufficient, and it is necessary to increase the frequency of the high - pressure compressor to increase the compression capacity of the high - pressure compressor and reduce the intermediate pressure.

[0128] When the intermediate pressure is lower than the target value, it is necessary to reduce the frequency of the high - pressure compressor to reduce the load of the high - pressure compressor and avoid insufficient gas replenishment caused by too low intermediate pressure.

[0129] The design logic of adjusting the frequencies of the high- and low-pressure stage compressors by the economizer supplementary air pressure is to maintain the intermediate pressure of the economizer by adjusting the frequency of the high-pressure stage compressor. The stability is optimized, and the energy efficiency of the two-stage compression cycle is improved. Specifically, the pressure deviation drives the frequency adjustment through is the real-time deviation of the intermediate pressure, which directly reflects the system state; the coefficient controls the sensitivity of the frequency adjustment, and its value range is 0.5~1.0Hz / kPa. It is calibrated through experiments to balance the response speed and stability. The frequencies of the high- and low-pressure stage compressors are linked to ensure a reasonable distribution of the compression ratio under the total load demand, avoid single-machine overload, and achieve coordinated control.

[0130] It should be understood that the above embodiments are one or more embodiments of the present invention. Based on the present invention, there are many other embodiments and their variations; when ordinary technicians in this industry do not make pioneering innovations, the variations and modifications made through the present invention all fall within the protection scope of the present invention.

Claims

1. A magnetic levitation centrifugal chiller, comprising a magnetic levitation compressor, a condenser and an evaporator. The magnetic levitation compressor is connected to the condenser through an exhaust pipeline, and the condenser is connected to the magnetic levitation compressor and the evaporator respectively through a liquid supply pipeline assembly; characterized in that: It also includes a natural process control module. The natural process control module calculates an energy efficiency health index by determining the energy efficiency health indicators of the chiller, and is used to dynamically adjust the startup sequence of multiple magnetic levitation compressors in the chiller. The natural process control module is electrically connected to the central controller; It also includes a refrigerant frequency conversion module. The refrigerant frequency conversion module is arranged between the evaporator and the magnetic levitation compressor. One end of the refrigerant frequency conversion module is connected to the evaporator through a first electronic expansion valve and a ball valve in sequence, and the other end is connected to the magnetic levitation compressor through a solenoid valve and a ball valve in sequence; on the pipeline of the first high-pressure refrigerant outlet of the condenser, a ball valve, a drying filter, a solenoid valve, a ball valve and a sight glass are arranged in sequence, and the pipeline between the refrigerant frequency conversion module and the magnetic levitation compressor is connected to the pipeline of the first high-pressure refrigerant outlet of the condenser; The exhaust pipeline is used to connect the exhaust port of the magnetic levitation compressor and the high-pressure refrigerant inlet of the condenser. A check valve is arranged at a position close to the exhaust port on the exhaust pipeline, and a butterfly valve is arranged at a position close to the high-pressure refrigerant inlet of the condenser; The liquid supply pipeline assembly includes an economizer. The economizer has different first and second circuits. The third high-pressure refrigerant outlet of the condenser is connected to the economizer port of the magnetic levitation compressor through a pipeline with a second electronic expansion valve and through the second circuit of the economizer. The second high-pressure refrigerant outlet of the condenser is connected to the low-pressure refrigerant inlet of the evaporator through the first circuit of the economizer. On the output pipeline of the first circuit, a ball valve, a third electronic expansion valve and a ball valve are arranged in sequence, and then through the low-pressure refrigerant outlet of the evaporator, it is connected to the suction port of the magnetic levitation compressor through a pipeline with a butterfly valve; The first electronic expansion valve, the second electronic expansion valve and the third electronic expansion valve are all electrically connected to the central controller, and their opening degrees are all controlled by the central controller; The evaporator is also provided with a bypass inlet, and the condenser is also provided with a bypass outlet. A load balance valve is arranged on the pipeline between the bypass inlet of the evaporator and the bypass outlet of the condenser.

2. The magnetic levitation centrifugal chiller according to claim 1, wherein: The natural process control module calculates an energy efficiency health index by determining the energy efficiency health indicators of the chiller, and is used to dynamically adjust the startup sequence of multiple magnetic levitation compressors in the chiller, including: Determine the energy efficiency health indicators of the chiller. The energy efficiency health indicators are determined by the compressor aging index and the real-time energy efficiency index. The energy efficiency health indicators are refrigerant flow rate, refrigeration capacity, compressor input power, evaporator inlet and outlet water temperature, condenser inlet water temperature, compressor mechanical efficiency, and the cumulative operation time of the compressor; Construct an energy efficiency health index model, and input the energy efficiency health indicators into the energy efficiency health index model to calculate the energy efficiency health index , The energy efficiency health index of the i-th compressor (i = 1,......, N) respectively includes an energy efficiency correction term, an evaporation efficiency correction term, and an equipment aging and balanced wear correction term, and satisfies the following relationship: Among them, is the actual energy efficiency ratio, is the refrigerating capacity, is the compressor input power; is the rated energy efficiency ratio, and N is the number of compressors; is the actual evaporation efficiency, is the temperature difference between the inlet and outlet water of the evaporator, that is , is the inlet water temperature of the evaporator, is the outlet water temperature of the evaporator; is the actual refrigerant flow rate, where , is the enthalpy difference of the evaporator, is the rated refrigerant flow rate, is the rated temperature difference; is the rated evaporation efficiency; is the energy efficiency ratio weight, representing the load rate dynamically adjusts the influence weight of the energy efficiency ratio; is the temperature correction coefficient, characterizing the influence degree of the condensation temperature on the evaporation efficiency; is the inlet water temperature of the condenser; is the compressor aging coefficient, i.e., the mechanical efficiency of the compressor, and the value is , is the pressure fluctuation correction coefficient, is the pressure fluctuation rate, is the cumulative operation time difference, and μ is the time difference attenuation coefficient; Dynamically adjust the compressor startup sequence. According to the EHI values of each compressor obtained by real-time calculation, generate a priority list in descending order according to the EHI values of each compressor, and dynamically adjust the compressor startup sequence according to the energy efficiency priority. The priority is sorted based on historical energy efficiency data and updated every 24 hours.

3. The magnetic levitation centrifugal chiller according to claim 2, wherein: The compressor aging coefficient satisfies the relationship: Among them, is the maximum allowable efficiency loss; is the cumulative running time, is the design life of the compressor, > 1 indicates that the efficiency decay rate increases with time.

4. A magnetic levitation centrifugal chiller according to claim 2, characterized in that: Considering the impact of ambient humidity on the energy efficiency health index, an ambient humidity correction term D is added. When calculating the energy efficiency health index, the original energy efficiency health index model is multiplied by the ambient humidity correction term D to satisfy the following relationship: Set the environmental humidity threshold to 60%, and the environmental humidity correction coefficient satisfies the following relationship: Among them, represents the humidity correction coefficient, represents the normalized value of the ambient relative humidity.

5. The magnetic levitation centrifugal chiller according to claim 2, wherein: The step of dynamically adjusting the compressor startup sequence also includes determining the optimal number of operating units and load distribution, including: Calculate the total refrigeration demand required by the chiller under actual working conditions , satisfying the relation: Traverse all possible compressor combinations, from 1 unit to all N units, and evaluate the comprehensive energy efficiency score of each combination , select the compressor combination that not only meets the total refrigeration demand but also maximizes the energy efficiency. The comprehensive energy efficiency score satisfies the following relationship: Among them, is the maximum refrigerating capacity; is the number of start-stop cycles; is the start-stop loss coefficient; group is the number of compressor combinations; According to the screening criteria , determine the total cooling capacity coverage requirement of the selected combination; select the combination that meets the screening criteria and has the highest comprehensive energy efficiency score as the optimal combination; After selecting the optimal combination, the load is distributed according to the energy efficiency health index ratio of each compressor, limiting the load rate of each unit. To ensure system stability and maximize efficiency, the load distribution satisfies the following relationship: Among them, is the load of the j-th compressor in the optimal combination, where j = 1, ..., k; k represents the number of compressors in the optimal combination; the denominator represents the total energy efficiency potential of all compressors in the optimal combination; the numerator represents the energy efficiency potential of the j-th compressor in the combination.

6. The magnetic levitation centrifugal chiller according to claim 1, characterized in that: The bypass pipeline of the exhaust port of the magnetic levitation compressor is connected to the pressure relief port of the evaporator through a cut-in valve and a ball valve in sequence.

7. A magnetic levitation centrifugal chiller according to claim 1, characterized in that: The opening control of the first electronic expansion valve and the second electronic expansion valve and the enthalpy increase of the economizer include: Build a refrigerant demand prediction model and determine the input parameters, including the real-time efficiency of the compressor , the change rate of the real-time efficiency , the superheat SH at the evaporator outlet, the condensation pressure and the evaporation pressure , calculate the predicted refrigerant flow rate , satisfying the relationship: Among them, is the current steady-state flow rate; is the flow rate-frequency correction coefficient, with the unit of kg / ( ); is the superheat correction coefficient, with the unit of kg / ( ); Dynamically control the opening degree of the electronic expansion valve, and set the initial opening degree to K 初 =K b + , is the opening response gain coefficient, K b is the current opening degree, is the current refrigerant flow rate, is the designed refrigerant flow rate; Perform closed-loop correction on superheat. When the measured superheat SH deviates from the target value, the opening is fine-tuned through the PID algorithm. Set the enthalpy-increasing starting condition. When the condensation pressure threshold is greater than or equal to 15% - 20% of the designed condensation pressure value , and the compressor frequency threshold is greater than or equal to 80% of the rated compressor frequency , start the economizer air injection; When the compressor exhaust temperature threshold is greater than or equal to the temperature tolerance warning threshold of the magnetic levitation compressor , and the superheat threshold is less than or equal to the critical protection value of the superheat target value , the enthalpy increase is forcibly enabled; Calculate the opening degree of the second electronic expansion valve of the economizer branch : Among them, is the condensation pressure; is the economizer intermediate pressure, i.e., the gas injection point pressure; is the rated design pressure; is the compressor exhaust temperature, is the reference temperature, is the adjustment coefficient; Compensation adjustment for the first electronic expansion valve of the main circuit: Among them, is the opening of the second electronic expansion valve of the economizer branch, with the unit of %; is the opening adjustment amount of the first electronic expansion valve of the main circuit, with the unit of %; The frequencies of high and low pressure compressors are adjusted by the economizer air supply pressure to meet the following relationship: Among them, is the frequency of the high-pressure stage compressor, with the unit of Hz; is the frequency of the low-pressure stage compressor, with the unit of Hz; is the target value of the intermediate pressure, with the unit of kPa; is the frequency adjustment coefficient, with the unit of Hz / kPa.

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