Control system and control method for data center rack-level cooling terminals

Abstract

This invention relates to a control system and method for a data center rack-level cooling terminal. The system includes: a first temperature sensor for measuring the rack outlet air temperature; a second temperature sensor for measuring the evaporator inlet air temperature; a third temperature sensor for measuring the evaporator outlet refrigerant temperature; a fourth temperature sensor for measuring the evaporator inlet refrigerant temperature; a fifth temperature sensor for measuring the electronic expansion valve inlet refrigerant temperature; a first pressure sensor for measuring the evaporator outlet refrigerant pressure; a second pressure sensor for measuring the electronic expansion valve inlet refrigerant pressure; and a third pressure sensor for measuring the electronic expansion valve outlet refrigerant pressure. This control method, through coordinated control of the electronic expansion valve and the fan, maintains the evaporator outlet refrigerant superheat and rack outlet air temperature within a reasonable range. It precisely adjusts the rack outlet air temperature according to rack load changes and enables rapid adjustment.

Description

Technical Field

[0001] This invention relates to the field of data center cooling technology, and in particular to a control system and control method for cooling terminals at the rack level in data centers. Background Technology

[0002] In recent years, the information economy, represented by big data and cloud computing, has developed rapidly, leading to a year-on-year increase in the construction and power consumption of data centers. Simultaneously, with the advancement of the dual-carbon strategy, the problem of excessive energy consumption in data centers has become increasingly prominent. Data centers house a large number of servers and information storage devices, which are characterized by high heat dissipation density, long cooling times, and stringent requirements for ambient temperature and humidity. To ensure the stable operation of servers and other equipment within data centers, year-round cooling and precise temperature control are necessary.

[0003] Traditional data centers mostly employ room-level cooling, which struggles to cope with load variations within the room, leading to localized hotspots or over-cooling. Rack-level cooling, on the other hand, provides on-demand cooling based on the load of different racks. The control system at the rack-level cooling terminal regulates the rack outlet air temperature via fan speed or electronic expansion valve opening. However, this approach commonly suffers from the following problems: Traditional electronic expansion valve control methods often use the evaporator outlet refrigerant superheat as the sole target value, employing PID control to regulate refrigerant flow. While this method ensures stable compressor operation, it cannot precisely adjust the rack outlet air temperature according to load changes. Furthermore, data center rack temperatures exhibit strong nonlinearity and time lag. The electronic expansion valve control process is coupled with the fan control process, making overshooting a common issue. PID control methods struggle to achieve precise temperature control and rapid adjustment. These problems affect the stable operation of equipment within the data center, necessitating the development of corresponding control systems and methods. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a control system and control method for the cooling terminal of data center racks, which solves the technical problems of the prior art being unable to accurately regulate the rack outlet air temperature according to the rack load changes, and the difficulty in achieving accurate temperature control and rapid adjustment based on the PID control method to regulate the fan.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0008] In a first aspect, the present invention provides a control system for a data center rack-level cooling terminal, comprising a first temperature sensor, a second temperature sensor, a third temperature sensor, a fourth temperature sensor, a fifth temperature sensor, a first pressure sensor, a second pressure sensor, a third pressure sensor, an evaporator heat exchange unit, an electronic expansion valve, and a programmable controller; the evaporator heat exchange unit includes an evaporator and a fan; the first temperature sensor is used to measure the rack outlet air temperature; the second temperature sensor is used to measure the evaporator inlet air temperature; the third temperature sensor is used to measure the evaporator outlet refrigerant temperature; the fourth temperature sensor is used to measure the evaporator inlet refrigerant temperature; and the fifth temperature sensor is used to measure the electronic expansion valve inlet temperature. The system includes: refrigerant temperature; a first pressure sensor to measure the refrigerant pressure at the evaporator outlet; a second pressure sensor to measure the refrigerant pressure at the inlet of the electronic expansion valve; a third pressure sensor to measure the refrigerant pressure at the outlet of the electronic expansion valve; and first, second, third, fourth, and fifth temperature sensors, as well as first, second, and third pressure sensors, all connected to the input terminals of the programmable controller (PLC). The output terminals of the PLC are connected to the electronic expansion valve and the fan. The PLC controls the refrigerant superheat at the evaporator outlet and the cabinet outlet air temperature within a reasonable range by coordinating the valve opening of the electronic expansion valve and the fan speed.

[0009] Optionally, the electronic expansion valve is installed at the evaporator inlet; the first temperature sensor is installed at the evaporator outlet; the second temperature sensor is installed at the evaporator inlet; the third temperature sensor and the first pressure sensor are respectively installed at the evaporator outlet; the fourth temperature sensor is installed at the evaporator inlet; the fifth temperature sensor and the second pressure sensor are respectively installed at the electronic expansion valve inlet; and the third pressure sensor is installed at the electronic expansion valve outlet.

[0010] Secondly, the present invention provides a control method for a data center rack-level cooling terminal, the control method being based on the control system for the data center rack-level cooling terminal, the control method comprising the following steps:

[0011] Step S1: Set and store the initial values ​​of the control system according to the actual needs of the specific application scenario. The initial values ​​include: the initial value of the fan speed V. start Initial values ​​of time-varying coefficients m and n, and the setpoint T for the cabinet outlet air temperature. out,set Temperature control accuracy setpoint T p,set 1. Evaporator outlet refrigerant superheat setpoint SH set 1. Evaporator heat exchange area A and electronic expansion valve channel area S;

[0012] Step S2: Calculate the measured value of refrigerant superheat SH at the evaporator outlet. sensor ;

[0013] Step S3: Based on the electronic expansion valve control model, according to the evaporator outlet refrigerant superheat setpoint SH set SH value of refrigerant superheat at evaporator outlet sensor Calculate the opening degree C of the electronic expansion valve;

[0014] Step S4: Output the opening degree C of the electronic expansion valve to the electronic expansion valve;

[0015] Step S5: Calculate the heat transfer coefficient K of the evaporator heat exchange unit, and store the current heat transfer coefficient K of the evaporator heat exchange unit and the current fan speed;

[0016] Step S6: Determine whether the rack outlet air temperature T1 is within the temperature control range; if yes, proceed to step S7; if no, proceed to step S9.

[0017] Step S7: Maintain the current fan speed;

[0018] Step S8: Detect whether a command to end control has been received; if received, end control; if not received, repeat steps S2 to S6.

[0019] Step S9: Determine if this is the first time calculating the fan speed V. cal If yes, proceed to step S91; if no, proceed to step S92.

[0020] Step S91: Based on the fan control model, according to the initial values ​​of the time-varying coefficients m and n, and the cabinet outlet air temperature setpoint T out,set The calculated fan speed V is determined by the following parameters: evaporator heat exchange area A, electronic expansion valve channel area S, current electronic expansion valve opening C, and current system operating parameters. cal Then proceed to step S10;

[0021] Step S92: Correct the time-varying coefficients m and n;

[0022] Step S93: Based on the fan control model, according to the corrected time-varying coefficients m and n, and the cabinet outlet air temperature setpoint T out,set The calculated fan speed V is determined by the following parameters: evaporator heat exchange area A, electronic expansion valve channel area S, current electronic expansion valve opening C, and current system operating parameters. cal Then proceed to step S10;

[0023] Step S10: Calculate the fan speed V cal Output to the fan, then repeat steps S2 to S6.

[0024] Optionally, in steps S5, S91, and S93, the system operating parameters include the evaporator inlet air temperature T2 and the refrigerant evaporation temperature T. r The following parameters are considered: refrigerant pressure at the electronic expansion valve outlet (P1), refrigerant pressure at the electronic expansion valve inlet (P2), refrigerant enthalpy at the evaporator outlet (h1), refrigerant enthalpy at the evaporator inlet (h2), and refrigerant density at the electronic expansion valve inlet (ρ). in Specific volume of refrigerant at the outlet of the electronic expansion valve ν out .

[0025] Optionally, in step S5, the heat transfer coefficient K of the evaporator heat exchange unit is calculated according to formula (5):

[0026]

[0027] In the formula (5), K is the heat transfer coefficient of the evaporator heat exchange unit, T1 is the cabinet outlet air temperature, A is the evaporator heat exchange area, S is the electronic expansion valve channel area, C is the electronic expansion valve opening degree, and the remaining parameters are the system operating parameters.

[0028] Optionally, in steps S91 and S93, the wind turbine control model is represented by formula (8):

[0029]

[0030] In formula (8), V cal Here is the calculated value of the fan speed, m and n are time-varying coefficients, and T is the calculated value of the fan speed. out,set The setpoint for the cabinet outlet air temperature is A, the heat exchange area of ​​the evaporator is S, the channel area of ​​the electronic expansion valve is C, and the opening degree of the electronic expansion valve is C. The remaining parameters are the operating parameters of the system.

[0031] Optionally, in step S92, correcting the time-varying coefficients m and n includes: according to formula (7):

[0032] lnV=lnm+nlnK(7)

[0033] By using multiple sets of stored corresponding fan speeds V and evaporator heat exchanger unit heat transfer coefficients K, the corrected values ​​of m and n are obtained through fitting and solving.

[0034] Optionally, the refrigerant evaporation temperature T r It is determined by the average value measured by the third and fourth temperature sensors, or directly equal to the refrigerant saturation temperature T corresponding to the refrigerant pressure P at the evaporator outlet. s The enthalpy of the refrigerant at the evaporator outlet, h1, is determined by the values ​​measured by the third temperature sensor and the first pressure sensor; the enthalpy of the refrigerant at the evaporator inlet, h2, is determined by the values ​​measured by the fifth temperature sensor and the second pressure sensor; the density of the refrigerant at the electronic expansion valve inlet, ρ...in The specific volume ν of the refrigerant at the outlet of the electronic expansion valve is determined by the values ​​measured by the fifth temperature sensor and the second pressure sensor. out The value is determined by the values ​​measured by the fifth temperature sensor, the second pressure sensor, and the third pressure sensor.

[0035] Optionally, in step S2, the measured value of refrigerant superheat SH at the evaporator outlet is calculated. sensor include:

[0036] Step S21: Calculate the saturation temperature T corresponding to the refrigerant pressure P at the evaporator outlet according to the fitting formula (1). s :

[0037] T s =f(P)(1)

[0038] The fitting formula (1) is obtained based on the physical properties of different refrigerants, where P is the refrigerant pressure at the evaporator outlet, and T is the refrigerant pressure at the outlet. s The refrigerant saturation temperature corresponding to the refrigerant pressure P at the evaporator outlet;

[0039] Step S22: Calculate the measured value of refrigerant superheat SH at the evaporator outlet using formula (2). sensor :

[0040] SH sensor =T3-T s (2)

[0041] In the formula (2), T3 is the refrigerant temperature at the evaporator outlet.

[0042] Optionally, in step S3, the electronic expansion valve control model is represented by formula (3):

[0043]

[0044] In formula (3), K P T represents the proportional coefficient of the control module. i T represents the integral time constant of the control module. D The differential time constant of the control module is represented by e(t), and the measured value of refrigerant superheat SH at the evaporator outlet is represented by e(t). sensor With respect to the refrigerant superheat setpoint SH at the evaporator outlet set The difference between the two values ​​is u(t), which is the output signal, i.e., the opening degree C of the electronic expansion valve.

[0045] (III) Beneficial Effects

[0046] The present invention has the following beneficial effects:

[0047] (1) The control system for data center rack-level cooling terminals proposed in this invention uses the refrigerant superheat at the evaporator outlet and the rack outlet air temperature as target values. By coordinating the control of the electronic expansion valve and the fan, the system controls the refrigerant superheat at the evaporator outlet and the rack outlet air temperature within a reasonable range. This ensures both the rack outlet air temperature and the refrigerant superheat at the evaporator outlet, thereby achieving both stable compressor operation and precise control of the rack outlet air temperature based on rack load changes. In addition, the fan speed can be adjusted according to cooling demand to avoid excessive cooling and waste of cooling capacity, thus balancing system reliability and energy efficiency.

[0048] (2) The control method for data center rack-level cooling terminals proposed in this invention constructs an electronic expansion valve control model based on the PID control principle. The valve opening of the electronic expansion valve is adjusted with the refrigerant superheat at the evaporator outlet as the target value. The opening of the electronic expansion valve directly affects the refrigerant superheat at the evaporator outlet, thereby controlling the refrigerant superheat at the evaporator outlet within a reasonable range, preventing the refrigerant superheat at the evaporator outlet from being too low, causing compressor liquid slugging, and improving the stability of the system.

[0049] (3) The control method proposed in this invention is based on the principle of heat balance between the refrigerant side and the air side and the fitting model between the fan speed and the heat transfer coefficient of the evaporator heat exchange unit to construct a control model for the fan speed. The fan speed is controlled according to the opening of the electronic expansion valve, the set value of the cabinet outlet air temperature, the system operating parameters and the time-varying coefficient. The cabinet outlet air temperature can be accurately regulated according to the cabinet load change, and the adjustment speed can be improved to achieve rapid regulation.

[0050] (4) The control method proposed in this invention takes the refrigerant superheat at the evaporator outlet and the air temperature at the cabinet outlet as target values. By coordinating the opening of the electronic expansion valve and the fan speed, the refrigerant superheat at the evaporator outlet and the air temperature at the cabinet outlet are controlled within a reasonable range. It has the characteristics of good anti-interference, avoids mutual coupling between the fan and the electronic expansion valve during the adjustment process, is suitable for controlled processes with large lag, can improve the adjustment accuracy and speed, and improve the temperature control effect of the system. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the control system for a data center rack-level cooling terminal according to the present invention;

[0052] Figure 2 This is a schematic diagram of the electronic expansion valve control model in this invention;

[0053] Figure 3 This is a schematic diagram of the wind turbine control model in this invention;

[0054] Figure 4This is a flowchart of the control method for a data center rack-level cooling terminal according to the present invention.

[0055] [Explanation of Labels in the Attached Image]

[0056] 1: First temperature sensor; 2: Second temperature sensor; 3: Third temperature sensor; 4: Fourth temperature sensor; 5: Fifth temperature sensor; 6: First pressure sensor; 7: Second pressure sensor; 8: Third pressure sensor; 9: Evaporator; 10: Fan; 11: Programmable controller; 12: Electronic expansion valve. Detailed Implementation

[0057] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and that the scope of the present invention can be fully conveyed to those skilled in the art.

[0058] Reference Figure 1 This embodiment proposes a control system for a data center rack-level cooling terminal. The control system includes a first temperature sensor 1, a second temperature sensor 2, a third temperature sensor 3, a fourth temperature sensor 4, a fifth temperature sensor 5, a first pressure sensor 6, a second pressure sensor 7, a third pressure sensor 8, an evaporator heat exchange unit, an electronic expansion valve 12, and a programmable controller 11. The evaporator heat exchange unit provides one-to-one heat dissipation for the rack and includes an evaporator 9 and a fan 10. The electronic expansion valve 12 is installed at the inlet of the evaporator 9. The valve body of the electronic expansion valve 12 is equipped with a coil, which is connected to the programmable controller 11 to receive the opening degree of the electronic expansion valve output by the programmable controller 11. The refrigerant flows through the electronic expansion valve 12, undergoing throttling and pressure reduction, before flowing into the evaporator 9. The fan 10 provides pressure to allow hot air to flow through the evaporator 9, thereby cooling it.

[0059] This invention does not limit the specific types of evaporator 9 and fan 10. Evaporator 9 can be a microchannel heat exchanger or a finned tube heat exchanger to achieve heat exchange function, and fan 10 can be an axial flow fan, a centrifugal fan, or a mixed flow fan. Furthermore, this invention does not limit the specific installation positions of evaporator 9 and fan 10. Typically, both evaporator 9 and fan 10 are installed on the rear door of the cabinet, with fan 10 installed near the outer side of evaporator 9. However, depending on the actual application requirements, both evaporator 9 and fan 10 can be installed on the front door of the cabinet, or one can be located on the front door and the other on the rear door.

[0060] The first temperature sensor 1 is installed at the air outlet of the evaporator 9, preferably close to the air outlet of the evaporator 9, and is used to measure the air outlet temperature of the evaporator, i.e., the air outlet temperature T1 of the cabinet.

[0061] The second temperature sensor 2 is installed at the air inlet of the evaporator 9 to measure the air inlet temperature T2 of the evaporator.

[0062] The third temperature sensor 3 and the first pressure sensor 6 are respectively installed at the outlet of the evaporator 9. The third temperature sensor 3 is used to measure the refrigerant temperature T3 at the outlet of the evaporator, and the first pressure sensor 6 is used to measure the refrigerant pressure P at the outlet of the evaporator.

[0063] The fourth temperature sensor 4 is installed at the inlet of the evaporator 9 to measure the refrigerant temperature at the evaporator inlet.

[0064] The fifth temperature sensor 5 and the second pressure sensor 7 are respectively installed at the inlet of the electronic expansion valve 12. The fifth temperature sensor 5 is used to measure the refrigerant temperature at the inlet of the electronic expansion valve, and the second pressure sensor 7 is used to measure the refrigerant pressure P2 at the inlet of the electronic expansion valve.

[0065] The third pressure sensor 8 is installed at the outlet of the electronic expansion valve 12 to measure the refrigerant pressure P1 at the outlet of the electronic expansion valve. In an optional embodiment, for a control system with low evaporator resistance, the third pressure sensor 8 may not be installed, and the outlet pressure P1 of the electronic expansion valve may be directly set to be equal to the refrigerant pressure P at the outlet of the evaporator.

[0066] Temperature sensors 1, 2, 3, 4, 5, 6, 7, and 8 are connected to the input terminals of programmable controller 11 via signal lines, inputting the measured parameter values ​​into the programmable controller 11. The output terminals of the programmable controller 11 are connected to the electronic expansion valve 12 and the fan 10, respectively, to transmit output signals to these devices, thereby controlling the opening degree of the electronic expansion valve and the fan speed. The programmable controller 11 controls the refrigerant superheat at the evaporator outlet within a reasonable range by changing the valve opening degree of the electronic expansion valve 12, and uses the valve opening degree of the electronic expansion valve 12 as an intermediate variable to regulate the fan speed, thus controlling the cabinet outlet air temperature within a reasonable range.

[0067] The control system proposed in this invention for data center rack-level cooling terminals uses the refrigerant superheat at the evaporator outlet and the rack outlet air temperature as target values. Through coordinated control of the electronic expansion valve and the fan, it maintains these two values ​​within a reasonable range. This ensures both stable compressor operation and precise temperature control based on rack load variations. Furthermore, the fan speed can be adjusted according to cooling demand to avoid over-cooling and energy waste, balancing system reliability and energy efficiency.

[0068] In this embodiment, the control model of the electronic expansion valve 12 involves four types of variables: input, measured, intermediate, and output. The input includes the evaporator outlet refrigerant superheat setpoint SH. set The measured quantities include the refrigerant pressure P at the evaporator outlet and the refrigerant temperature T3 at the evaporator outlet. The intermediate quantities include the refrigerant saturation temperature T corresponding to the refrigerant pressure P at the evaporator outlet. s SH value of refrigerant superheat at evaporator outlet sensor The output includes the opening degree C of the electronic expansion valve.

[0069] Figure 2 The schematic diagram of the control model of the electronic expansion valve 12 in an embodiment of the present invention is shown.

[0070] The programmable controller 11 calculates the saturation temperature T corresponding to the refrigerant pressure P at the evaporator outlet using formula (1). s .

[0071] T s =f(P)(1)

[0072] Formula (1) above is a fitting formula, which is obtained based on the physical properties of different refrigerants. Wherein, P is the refrigerant pressure at the evaporator outlet detected by the first pressure sensor 6, and T... s The refrigerant saturation temperature is the refrigerant pressure P at the evaporator outlet.

[0073] Then, the programmable controller 11 calculates the measured value of refrigerant superheat SH at the evaporator outlet using formula (2). sensor .

[0074] SH sensor =T3-T s (2)

[0075] In the above formula (2), T3 is the refrigerant temperature at the evaporator outlet detected by the third temperature sensor 3, T s The refrigerant saturation temperature is the refrigerant pressure P at the evaporator outlet.

[0076] The control model of the electronic expansion valve 12 is based on the PID control principle and can be expressed by formula (3).

[0077] The programmable controller 11 calculates the opening degree C of the electronic expansion valve using formula (3).

[0078]

[0079] In the above formula (3), K P T represents the proportional coefficient of the control module. i T represents the integral time constant of the control module. D The differential time constant of the control module is represented by e(t), and the measured value of refrigerant superheat SH at the evaporator outlet is represented by e(t). sensor With respect to the refrigerant superheat setpoint SH at the evaporator outlet set The difference between the two values ​​is u(t), which is the output signal, i.e., the opening degree C of the electronic expansion valve.

[0080] It should be noted that the control module parameters of the electronic expansion valve 12 can be tuned using traditional parameter tuning methods such as the attenuation curve method, the critical proportional gain method, or the self-tuning module within the control module. Parameter tuning refers to determining the specific values ​​of the proportional coefficient, integral time constant, and derivative time constant in the controller based on the characteristics of the controlled process, in order to achieve the best control effect. Specifically, in this embodiment, the control module parameter K in the above formula (3) is tuned. P T i and T D Perform parameter tuning.

[0081] The programmable controller 11 sends the electronic expansion valve opening degree C obtained according to formula (3) to the electronic expansion valve 12 to control the valve opening degree of the electronic expansion valve 12. The valve opening degree of the electronic expansion valve 12 directly affects the refrigerant superheat measurement value SH at the outlet of the evaporator 9. sensor This allows the superheat of the refrigerant at the evaporator outlet to be controlled within a reasonable range by changing the opening degree of the electronic expansion valve.

[0082] Figure 3 The schematic diagram of the wind turbine control model in this embodiment is shown. The derivation process of the wind turbine control model will be explained below.

[0083] Based on the principle of thermal balance between the refrigerant side and the air side, formula (4) is obtained. Among them, the left side of the equation is the formula for calculating the cooling capacity of the electronic expansion valve, and the right side of the equation is the formula for calculating the cooling capacity of the evaporator heat exchange unit. This equation holds true in the same cooling system.

[0084]

[0085] In the above formula (4), T2 is the evaporator inlet air temperature detected by the second temperature sensor 2; T1 is the cabinet outlet air temperature detected by the first temperature sensor 1, i.e., the evaporator outlet air temperature; T r The refrigerant evaporation temperature is determined by the average value measured by the third temperature sensor 3 and the fourth temperature sensor 4, or it can be directly equal to the refrigerant saturation temperature T corresponding to the refrigerant pressure P at the evaporator outlet. s P2 is the refrigerant pressure at the inlet of the electronic expansion valve detected by the second pressure sensor 7; P1 is the refrigerant pressure at the outlet of the electronic expansion valve detected by the third pressure sensor 8; h1 is the refrigerant enthalpy at the evaporator outlet, determined by the values ​​measured by the third temperature sensor 3 and the first pressure sensor 6; h2 is the refrigerant enthalpy at the evaporator inlet, determined by the values ​​measured by the fifth temperature sensor 5 and the second pressure sensor 7; ρ in The refrigerant density at the inlet of the electronic expansion valve is determined by the values ​​measured by the fifth temperature sensor 5 and the second pressure sensor 7; v out The refrigerant specific volume at the outlet of the electronic expansion valve is determined by the values ​​measured by the fifth temperature sensor 5, the second pressure sensor 7, and the third pressure sensor 8; K is the heat transfer coefficient of the evaporator heat exchange unit; A is the heat transfer area of ​​the evaporator; S is the channel area of ​​the electronic expansion valve; and C is the opening degree of the electronic expansion valve.

[0086] It should be noted that the enthalpy of the refrigerant at the evaporator inlet (h2), the enthalpy of the refrigerant at the evaporator outlet (h1), and the density of the refrigerant at the inlet of the electronic expansion valve (ρ) are... in Specific volume of refrigerant at the outlet of the electronic expansion valve v out The calculation formulas are all existing technologies, and this article does not impose specific limitations on them.

[0087] After simplification, we get formula (5):

[0088]

[0089] The meanings of the parameters in formula (5) are the same as those of the corresponding parameters in formula (4), and will not be repeated here.

[0090] There is a functional relationship between the fan speed V and the heat transfer coefficient K of the evaporator heat exchange unit. This functional relationship can be represented by a fitting model:

[0091] V = mK n (6)

[0092] Taking the logarithm of both sides of the fitting formula (6), we get formula (7):

[0093] lnV=lnm+nlnK(7)

[0094] In the above formulas (6) and (7), V is the fan speed; K is the heat transfer coefficient of the evaporator heat exchange unit; m and n are time-varying coefficients that change with the operating performance of the evaporator 9.

[0095] Substitute the values ​​of V and K from multiple sets into formula (7), and use the least squares method to fit the values ​​of m and n.

[0096] The wind turbine control model can be constructed based on the above formulas (4)-(7):

[0097]

[0098] In the above formula (8), V cal T is the calculated value of the fan speed. out,set This is the setpoint for the cabinet outlet air temperature. m and n are time-varying coefficients, which change with the operating performance of evaporator 9. The meanings of the remaining parameters are consistent with the meanings of the corresponding parameters in formula (4), and will not be repeated here. For ease of description, the evaporator inlet air temperature T2 and the refrigerant evaporation temperature T3 will be referred to as the evaporator inlet air temperature T2 and the refrigerant evaporation temperature T3 in the following text. r The following parameters are considered: refrigerant pressure at the electronic expansion valve outlet (P1), refrigerant pressure at the electronic expansion valve inlet (P2), refrigerant enthalpy at the evaporator outlet (h1), refrigerant enthalpy at the evaporator inlet (h2), and refrigerant density at the electronic expansion valve inlet (ρ). in Specific volume of refrigerant at the outlet of the electronic expansion valve ν out These are collectively referred to as system operating parameters.

[0099] Figure 4 A flowchart of the control method for a data center rack-level cooling terminal proposed in this embodiment is shown. This control method, based on the control system for a data center rack-level cooling terminal of the present invention, regulates the rack outlet air temperature by coordinating the control of the electronic expansion valve 12 and the fan 10. Specifically, it includes the following steps:

[0100] Step S1: Set and store the initial values ​​of the control system according to the actual needs of the specific application scenario. The initial values ​​include: the initial value of the fan speed V. start Initial values ​​of time-varying coefficients m and n, and the setpoint T for the cabinet outlet air temperature. out,set Temperature control accuracy setpoint T p,set 1. Evaporator outlet refrigerant superheat setpoint SH set 1. Evaporator heat exchange area A and electronic expansion valve channel area S;

[0101] Step S2: Calculate the measured value of refrigerant superheat SH at the evaporator outlet. sensor ;

[0102] Step S3: Based on the electronic expansion valve control model, according to the evaporator outlet refrigerant superheat setpoint SH set SH value of refrigerant superheat at evaporator outletsensor Calculate the opening degree C of the electronic expansion valve;

[0103] Step S4: Output the opening degree C of the electronic expansion valve to the electronic expansion valve 12;

[0104] Step S5: Calculate the heat transfer coefficient K of the evaporator heat exchange unit, and store the current heat transfer coefficient K of the evaporator heat exchange unit and the current fan speed;

[0105] Step S6: Determine whether the rack outlet air temperature T1 is within the temperature control range, that is, whether the rack outlet air temperature T1 is within the set value T of the rack outlet air temperature. out,set Is the absolute value of the difference less than or equal to the temperature control accuracy setting value T? p,set If yes, proceed to step S7; otherwise, proceed to step S9.

[0106] Step S7: Maintain the current fan speed;

[0107] Step S8: Detect whether a command to end control has been received; if received, end control; if not received, repeat steps S2 to S6.

[0108] Step S9: Determine if this is the first time calculating the fan speed V. cal If yes, proceed to step S91; if no, proceed to step S92.

[0109] Step S91: Based on the fan control model, according to the initial values ​​of the time-varying coefficients m and n, and the cabinet outlet air temperature setpoint T out,set The calculated fan speed V is determined by the following parameters: evaporator heat exchange area A, electronic expansion valve channel area S, current electronic expansion valve opening C, and current system operating parameters. cal Then proceed to step S10;

[0110] Step S92: Correct the time-varying coefficients m and n;

[0111] Step S93: Based on the fan control model, according to the corrected values ​​of m and n, and the cabinet outlet air temperature setpoint T out,set The calculated fan speed V is determined by the following parameters: evaporator heat exchange area A, electronic expansion valve channel area S, current electronic expansion valve opening C, and current system operating parameters. cal Then proceed to step S10;

[0112] Step S10: Calculate the fan speed V cal Output to fan 10, then repeat steps S2 to S6.

[0113] The present invention provides a collaborative control method for a rack-level cooling terminal system in a data center. Using the refrigerant superheat at the evaporator outlet and the rack outlet air temperature as target values, it collaboratively controls the electronic expansion valve and fan to maintain these values ​​within a reasonable range. This ensures both stable compressor operation and precise temperature control based on rack load variations. Furthermore, the fan speed can be adjusted according to cooling demand to avoid over-cooling and energy waste, thus balancing system reliability and energy efficiency.

[0114] More specifically, in step S2 above, the measured value of refrigerant superheat at the evaporator outlet, SH, is calculated. sensor include:

[0115] Step S21: Calculate the saturation temperature T corresponding to the refrigerant pressure P at the evaporator outlet according to the fitting formula (1). s :

[0116] T s =f(P)(1)

[0117] The above fitting formula (1) is obtained based on the physical properties of different refrigerants, where P represents the measured value of the refrigerant pressure at the evaporator outlet detected by the first pressure sensor 6, and T s This represents the refrigerant saturation temperature corresponding to the refrigerant pressure P at the evaporator outlet.

[0118] Step S22: Calculate the measured value of refrigerant superheat SH at the evaporator outlet using formula (2). sensor :

[0119] SH sensor =T3-T s (2)

[0120] In the above formula (2), T3 represents the measured value of the refrigerant temperature at the evaporator outlet detected by the third temperature sensor 3, T s This represents the refrigerant saturation temperature corresponding to the refrigerant pressure P at the evaporator outlet.

[0121] More specifically, in step S3 above, the electronic expansion valve control model is represented by formula (3):

[0122]

[0123] In the above formula (3), K P T represents the proportional coefficient of the control module. i T represents the integral time constant of the control module. D The differential time constant of the control module is represented by e(t), and the measured value of refrigerant superheat SH at the evaporator outlet is represented by e(t).sensor With respect to the refrigerant superheat setpoint SH at the evaporator outlet set The difference between the two values ​​is u(t), which is the output signal, i.e., the opening degree C of the electronic expansion valve.

[0124] The control method for data center rack-level cooling terminals proposed in this invention constructs an electronic expansion valve control model based on the PID control principle. The valve opening of the electronic expansion valve is adjusted with the refrigerant superheat at the evaporator outlet as the target value. The opening of the electronic expansion valve directly affects the refrigerant superheat at the evaporator outlet, thereby controlling the refrigerant superheat at the evaporator outlet within a reasonable range, preventing excessively low refrigerant superheat at the evaporator outlet from causing compressor liquid slugging, and improving system stability.

[0125] More specifically, in steps S5, S91, and S93 above, the system operating parameters include the evaporator inlet air temperature T2 and the refrigerant evaporation temperature T. r The following parameters are considered: refrigerant pressure at the electronic expansion valve outlet (P1), refrigerant pressure at the electronic expansion valve inlet (P2), refrigerant enthalpy at the evaporator outlet (h1), refrigerant enthalpy at the evaporator inlet (h2), and refrigerant density at the electronic expansion valve inlet (ρ). in Specific volume of refrigerant at the outlet of the electronic expansion valve ν out Among them, the refrigerant evaporation temperature T r The value is determined by the average of the values ​​measured by the third temperature sensor 3 and the fourth temperature sensor 4, or directly equal to the refrigerant saturation temperature T corresponding to the refrigerant pressure P at the evaporator outlet. s The enthalpy of the refrigerant at the evaporator outlet, h1, is determined by the values ​​measured by the third temperature sensor 3 and the first pressure sensor 6; the enthalpy of the refrigerant at the evaporator inlet, h2, is determined by the values ​​measured by the fifth temperature sensor 5 and the second pressure sensor 7; the density of the refrigerant at the electronic expansion valve inlet, ρ... in The specific volume ν of the refrigerant at the outlet of the electronic expansion valve is determined by the values ​​measured by the fifth temperature sensor 5 and the second pressure sensor 7. out The value is determined by the values ​​measured by the fifth temperature sensor 5, the second pressure sensor 7, and the third pressure sensor 8.

[0126] More specifically, in step S5 above, the heat transfer coefficient K of the evaporator heat exchange unit is calculated according to formula (5):

[0127]

[0128] In the above formula (5), K is the heat transfer coefficient of the evaporator heat exchange unit, T1 is the cabinet outlet air temperature detected by the first temperature sensor 1, A is the heat exchange area of ​​the evaporator, S is the channel area of ​​the electronic expansion valve, C is the opening degree of the electronic expansion valve, and the remaining parameters are system operating parameters.

[0129] More specifically, in step S5 above, the maximum number of data points that can be stored for the heat transfer coefficient K of the evaporator heat exchange unit and the fan speed can be set. When the maximum number of stored data points is reached, the latest data is used to overwrite the oldest data in sequence to optimize data and control computation, thereby further improving the system's adjustment speed.

[0130] More specifically, in steps S91 and S93 above, the wind turbine control model is represented by formula (8):

[0131]

[0132] In the above formula (8), V cal Here is the calculated value of the fan speed, m and n are time-varying coefficients, and T is the calculated value of the fan speed. out,set The setpoint for the cabinet outlet air temperature is A, where A is the evaporator heat exchange area, S is the electronic expansion valve channel area, C is the electronic expansion valve opening, and the remaining parameters are system operating parameters.

[0133] More specifically, in step S92 above, correcting the time-varying coefficients m and n includes: according to formula (7):

[0134] lnV=lnm+nlnK(7)

[0135] By using multiple sets of stored corresponding fan speeds V and evaporator heat exchanger unit heat transfer coefficients K, the corrected values ​​of m and n are obtained through fitting and solving.

[0136] The proposed control method for data center rack-level cooling terminals constructs a fan speed control model based on the refrigerant-air heat balance principle and a fitting model between fan speed and evaporator heat exchange unit heat transfer coefficient. The fan speed is controlled according to the electronic expansion valve opening, rack outlet air temperature setpoint, system operating parameters, and time-varying coefficients. This allows for precise regulation of rack outlet air temperature based on rack load changes, and improves adjustment speed for rapid control. Furthermore, the fan speed can be adjusted according to cooling demand, avoiding over-cooling and wasting cooling capacity, thus balancing system reliability and energy efficiency.

[0137] The control method for data center rack-level cooling terminals of the present invention uses the refrigerant superheat at the evaporator outlet and the rack outlet air temperature as target values. By coordinating the control of the opening of the electronic expansion valve and the fan speed, the superheat of the refrigerant at the evaporator outlet and the rack outlet air temperature are controlled within a reasonable range. It has the characteristics of good anti-interference, avoids mutual coupling between the fan and the electronic expansion valve during the adjustment process, is suitable for controlled processes with large lag, can improve the adjustment accuracy and speed, and improve the temperature control effect of the system.

[0138] Although the control system and control method of the rack-level cooling terminal proposed in this embodiment are applied to data centers for illustrative purposes, those skilled in the art will recognize that the control system and control method of the rack-level cooling terminal of the present invention can also be used in rack-level air conditioning systems in other non-data center application scenarios.

[0139] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0140] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0141] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that they are in indirect contact through an intermediate medium. Furthermore, "above," "over," or "on top" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," or "beneath" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0142] In the description of this specification, the terms "one embodiment," "some embodiments," "embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0143] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A control method for a data center rack-level cooling terminal, the control method being based on a control system for a data center rack-level cooling terminal, characterized in that, The control method includes the following steps: Step S1: Set and store the initial values ​​of the control system according to the actual needs of the specific application scenario. The initial values ​​include: the initial value of the fan speed V. start Initial values ​​of time-varying coefficients m and n, and the setpoint T for the cabinet outlet air temperature. out,set Temperature control accuracy setpoint T p,set 1. Evaporator outlet refrigerant superheat setpoint SH set 1. Evaporator heat exchange area A and electronic expansion valve channel area S; Step S2: Calculate the measured value of refrigerant superheat SH at the evaporator outlet. sensor ; Step S3: Based on the electronic expansion valve control model, according to the evaporator outlet refrigerant superheat setpoint SH set SH value of refrigerant superheat at evaporator outlet sensor Calculate the opening degree C of the electronic expansion valve; Step S4: Output the opening degree C of the electronic expansion valve to the electronic expansion valve (12); Step S5: Calculate the heat transfer coefficient K of the evaporator heat exchange unit, and store the current heat transfer coefficient K of the evaporator heat exchange unit and the current fan speed; Step S6: Determine whether the rack outlet air temperature T1 is within the temperature control range; if yes, proceed to step S7; if no, proceed to step S9. Step S7: Maintain the current fan speed; Step S8: Detect whether a command to end control has been received; if received, end control; if not received, repeat steps S2 to S6. Step S9: Determine if this is the first time calculating the fan speed V. cal If yes, proceed to step S91; if no, proceed to step S92. Step S91: Based on the fan control model, according to the initial values ​​of the time-varying coefficients m and n, and the cabinet outlet air temperature setpoint T out,set The calculated fan speed V is determined by the following parameters: evaporator heat exchange area A, electronic expansion valve channel area S, current electronic expansion valve opening C, and current system operating parameters. cal Then proceed to step S10; Step S92: Correct the time-varying coefficients m and n; Step S93: Based on the fan control model, according to the corrected time-varying coefficients m and n, and the cabinet outlet air temperature setpoint T out,set The calculated fan speed V is determined by the following parameters: evaporator heat exchange area A, electronic expansion valve channel area S, current electronic expansion valve opening C, and current system operating parameters. cal Then proceed to step S10; Step S10: Calculate the fan speed V cal Output to the fan (10), and then repeat steps S2 to S6.

2. The control method for a data center rack-level cooling terminal as described in claim 1, characterized in that: In steps S91 and S93, the system operating parameters include the evaporator inlet air temperature T2 and the refrigerant evaporation temperature T. r Electronic expansion valve outlet refrigerant pressure P1, electronic expansion valve inlet refrigerant pressure P2, evaporator outlet refrigerant enthalpy h1, evaporator inlet refrigerant enthalpy h2, electronic expansion valve inlet refrigerant density. Specific volume of refrigerant at the outlet of the electronic expansion valve .

3. The control method for a data center rack-level cooling terminal as described in claim 2, characterized in that: In step S5, the heat transfer coefficient K of the evaporator heat exchange unit is calculated according to formula (5): （5） In the formula (5), K is the heat transfer coefficient of the evaporator heat exchange unit, T1 is the cabinet outlet air temperature, A is the evaporator heat exchange area, S is the electronic expansion valve channel area, C is the electronic expansion valve opening degree, and the remaining parameters are the system operating parameters.

4. The control method for a data center rack-level cooling terminal as described in claim 2, characterized in that: In steps S91 and S93, the wind turbine control model is represented by formula (8): （8） In formula (8), V cal Here is the calculated value of the fan speed, m and n are time-varying coefficients, and T is the calculated value of the fan speed. out,set The setpoint for the cabinet outlet air temperature is A, the heat exchange area of ​​the evaporator is S, the channel area of ​​the electronic expansion valve is C, and the opening degree of the electronic expansion valve is C. The remaining parameters are the operating parameters of the system.

5. The control method for a data center rack-level cooling terminal as described in claim 2, characterized in that: In step S92, correcting the time-varying coefficients m and n includes: according to formula (7): （7） By using multiple sets of stored corresponding fan speeds V and evaporator heat exchanger unit heat transfer coefficients K, the corrected values ​​of m and n are obtained through fitting and solving.

6. The control method for a data center rack-level cooling terminal as described in claim 2, characterized in that: Refrigerant evaporation temperature T r The value is determined by the average of the values ​​measured by the third temperature sensor (3) and the fourth temperature sensor (4), or directly equal to the refrigerant saturation temperature T corresponding to the refrigerant pressure P at the evaporator outlet. s The refrigerant enthalpy h1 at the evaporator outlet is determined by the values ​​measured by the third temperature sensor (3) and the first pressure sensor (6); the refrigerant enthalpy h2 at the evaporator inlet is determined by the values ​​measured by the fifth temperature sensor (5) and the second pressure sensor (7); the refrigerant density at the electronic expansion valve inlet... The specific volume of the refrigerant at the outlet of the electronic expansion valve is determined by the values ​​measured by the fifth temperature sensor (5) and the second pressure sensor (7). The values ​​measured by the fifth temperature sensor (5), the second pressure sensor (7), and the third pressure sensor (8) are used to determine the value.

7. The control method for a data center rack-level cooling terminal as described in claim 1, characterized in that: In step S2, the measured value of refrigerant superheat SH at the evaporator outlet is calculated. sensor include: Step S21: Calculate the saturation temperature T corresponding to the refrigerant pressure P at the evaporator outlet according to the fitting formula (1). s : （1） The fitting formula (1) is obtained based on the physical properties of different refrigerants, where P is the refrigerant pressure at the evaporator outlet, and T is the refrigerant pressure at the outlet. s The refrigerant saturation temperature corresponding to the refrigerant pressure P at the evaporator outlet; Step S22: Calculate the measured value of refrigerant superheat SH at the evaporator outlet using formula (2). sensor : （2） In the formula (2), T3 is the refrigerant temperature at the evaporator outlet.

8. The control method for a data center rack-level cooling terminal as described in claim 7, characterized in that: In step S3, the electronic expansion valve control model is represented by formula (3): （3） In formula (3), K P T represents the proportional coefficient of the control module. i T represents the integral time constant of the control module. D The differential time constant of the control module is represented by e(t), and the measured value of refrigerant superheat SH at the evaporator outlet is represented by e(t). sensor With respect to the refrigerant superheat setpoint SH at the evaporator outlet set The difference between the two values ​​is u(t), which is the output signal, i.e., the opening degree C of the electronic expansion valve.

9. A control system for a data center rack-level cooling terminal, comprising the control method for a data center rack-level cooling terminal as described in any one of claims 1-8, characterized in that, The control system includes a first temperature sensor (1), a second temperature sensor (2), a third temperature sensor (3), a fourth temperature sensor (4), a fifth temperature sensor (5), a first pressure sensor (6), a second pressure sensor (7), a third pressure sensor (8), an evaporator heat exchange unit, an electronic expansion valve (12), and a programmable controller (11); the evaporator heat exchange unit includes an evaporator (9) and a fan (10); the first temperature sensor (1) is used to measure the cabinet outlet air temperature; the second temperature sensor (2) is used to measure the evaporator inlet air temperature; the third temperature sensor (3) is used to measure the evaporator outlet refrigerant temperature; the fourth temperature sensor (4) is used to measure the evaporator inlet refrigerant temperature; the fifth temperature sensor (5) is used to measure the electronic expansion valve inlet refrigerant temperature; the first pressure sensor (6) is used to measure the evaporator outlet refrigerant temperature; the second temperature sensor (7) is used to measure the evaporator outlet refrigerant temperature; the third pressure sensor (8) is used to measure the evaporator outlet refrigerant temperature; the fourth temperature sensor (4) is used to measure the evaporator inlet refrigerant temperature; the fifth temperature sensor (5) is used to measure the electronic expansion valve inlet refrigerant temperature; the first pressure sensor (9) is used to measure the evaporator outlet refrigerant temperature; the second temperature sensor (9) is used to measure the evaporator outlet refrigerant temperature; the third pressure sensor (9) is used to measure the evaporator outlet refrigerant temperature; the fourth pressure sensor (9) is used to measure the evaporator outlet refrigerant temperature; the fifth pressure sensor (9) is used to measure the electronic expansion valve inlet refrigerant temperature; the fifth pressure sensor (9) is used to measure the evaporator outlet refrigerant temperature; the fifth pressure sensor (9) is used to measure the evaporator outlet refrigerant temperature; the fifth pressure sensor (9) is used to measure the evapor 6) Used to measure the refrigerant pressure at the evaporator outlet; the second pressure sensor (7) is used to measure the refrigerant pressure at the inlet of the electronic expansion valve; the third pressure sensor (8) is used to measure the refrigerant pressure at the outlet of the electronic expansion valve; the first temperature sensor (1), the second temperature sensor (2), the third temperature sensor (3), the fourth temperature sensor (4), the fifth temperature sensor (5), the first pressure sensor (6), the second pressure sensor (7), and the third pressure sensor (8) are respectively connected to the input terminal of the programmable controller (11); the output terminal of the programmable controller (11) is respectively connected to the electronic expansion valve (12) and the fan (10); the programmable controller (11) controls the refrigerant superheat at the evaporator outlet and the air temperature at the cabinet outlet within a reasonable range by coordinating the valve opening of the electronic expansion valve (12) and the fan speed.

10. The control system for a data center rack-level cooling terminal as described in claim 9, characterized in that: The electronic expansion valve (12) is installed at the inlet of the evaporator (9); the first temperature sensor (1) is installed at the air outlet of the evaporator (9); the second temperature sensor (2) is installed at the air inlet of the evaporator (9); the third temperature sensor (3) and the first pressure sensor (6) are respectively installed at the outlet of the evaporator (9); the fourth temperature sensor (4) is installed at the inlet of the evaporator (9); the fifth temperature sensor (5) and the second pressure sensor (7) are respectively installed at the inlet of the electronic expansion valve (12); and the third pressure sensor (8) is installed at the outlet of the electronic expansion valve (12).

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