Air conditioning system, and method for regulating system load by means of hot gas bypass

Abstract

A method for regulating a system load by means of hot gas bypass. The method comprises the following steps: acquiring a real-time outlet water temperature and a target outlet water temperature; determining a relationship between the magnitudes of the real-time outlet water temperature and the target outlet water temperature and a trend of change in the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature; on the basis of the relationship between the magnitudes of the real-time outlet water temperature and the target outlet water temperature and the trend of change in the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature that are determined in the above step, determining an amount of change in the valve opening of hot gas bypass; and regulating the valve opening of the hot gas bypass, thereby adjusting a system load. On the basis of different fluctuation trends of a water temperature with regard to approaching or deviating from a target value, an independent PID control mode is separately used, i.e., a dual-PID control mode, so that the system controls the water temperature more precisely and stably, the amplitude of fluctuation of the water temperature is smaller, and the system is more energy-saving.

Description

Air conditioning system and method for regulating system load by hot gas bypass Technical Field

[0001] The present application relates to an air-conditioning system and a method for adjusting the system load, and in particular to an air-conditioning system with hot gas bypass and a method for adjusting the system load through the hot gas bypass.

[0002] Background

[0003] Current air conditioning systems typically use refrigeration units powered by centrifugal compressors. To expand the operating range of the air conditioning system, the system is typically deloaded (cooling capacity reduced) using the following methods: variable frequency drive (VSD) and guide vane adjustment (IGV). After these deload capabilities have been fully utilized, if further deload is required on-site, a hot gas bypass is often activated to further reduce the system load and expand the system's cooling capacity range. The hot gas bypass is equipped with a hot gas bypass valve, and different openings of the hot gas bypass valve correspond to different load deload capabilities. By adjusting the opening of the hot gas bypass valve, the load deload capacity of the hot gas bypass is adjusted and controlled accordingly.

[0004] Summary of the Invention

[0005] In industrial process control, the control based on the proportional, integral, and differential error between the real-time data collected by the controlled object and the given value is referred to as PID (Proportional Integral Derivative) control. In the prior art, single PID control is usually used to adjust the opening of the hot gas bypass valve in the air conditioning system. Single PID control means that only one set of control coefficients (proportional coefficient K) is used in the differential equation of PID control. p , integration time constant T i and the differential time constant T d ) to accommodate changes in different variables. However, the aforementioned single PID control method has a lag in adjusting the compressor load and cannot quickly and accurately respond to load-induced changes in system water temperature, resulting in unstable water temperature and large fluctuations. Therefore, a more precise and stable control method for regulating system water temperature is needed.

[0006] To more accurately and stably control water temperature based on changes in on-site loads, minimizing water temperature fluctuations, and taking into account the indirectness and hysteresis of hot gas bypass load regulation, this application provides a method for regulating system load using dual PID control of hot gas bypass. Specifically, different PID control modes are set based on the varying trends of water temperature relative to a setpoint, i.e., whether the water temperature approaches or deviates from the setpoint, thereby more precisely controlling the opening of the hot gas bypass valve. Therefore, compared to a single PID control method, this control method provides smoother, more precise, and relatively energy-efficient water temperature control.

[0007] Therefore, according to the first aspect of the present application, the present application provides a method for regulating system load through hot gas bypass, characterized in that the method includes the following steps: S01, obtaining the real-time water outlet temperature and the target water outlet temperature; S02, judging the relationship between the real-time water outlet temperature and the target water outlet temperature and the changing trend of the absolute value of the difference between the real-time water outlet temperature and the target water outlet temperature; S03, determining the change in the valve opening of the hot gas bypass based on the relationship between the real-time water outlet temperature and the target water outlet temperature and the changing trend of the absolute value of the difference between the real-time water outlet temperature and the target water outlet temperature judged in step S02; S04, adjusting the valve opening of the hot gas bypass based on the change in the valve opening determined in step S03, thereby adjusting the system load.

[0008] According to the first aspect of the present application, it is characterized in that: steps S01 to S04 are cyclically executed in a set water temperature adjustment cycle.

[0009] According to the first aspect of the present application, it is characterized in that: in step S03, if the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature has an increasing trend, the first PID control method is used to determine the change in the valve opening of the hot gas bypass; or if the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature has a decreasing trend, the second PID control method is used to determine the change in the valve opening of the hot gas bypass.

[0010] According to the first aspect of the present application, it is characterized in that: in step S03, if the real-time outlet water temperature is greater than the target outlet water temperature and the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature has an increasing trend, in step S04, the valve opening of the hot gas bypass is reduced; if the real-time outlet water temperature is less than the target outlet water temperature and the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature has an increasing trend, in step S04, the valve opening of the hot gas bypass is increased; if the real-time outlet water temperature is greater than the target outlet water temperature and the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature has a decreasing trend, in step S04, the valve opening of the hot gas bypass is reduced; or if the real-time outlet water temperature is less than the target outlet water temperature and the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature has a decreasing trend, in step S04, the valve opening of the hot gas bypass is increased.

[0011] According to the first aspect of the present application, it is characterized in that: the first PID control method has a first set of control parameters, and the second PID control method has a second set of control parameters, wherein the first set of control parameters is different from the second set of control parameters, and the first set of control parameters and the second set of control parameters are obtained through system debugging.

[0012] According to the first aspect of the present application, it is characterized in that: the first group of control parameters includes a first proportional coefficient, a first integral time constant and a first differential time constant, and the second group of control parameters includes a second proportional coefficient, a second integral time constant and a second differential time constant.

[0013] According to the first aspect of the present application, it is characterized in that: when the changing trend of the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature increases, the changing amplitude of the valve opening change increases, or when the changing trend of the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature decreases, the changing amplitude of the valve opening change decreases.

[0014] According to the first aspect of the present application, it is characterized in that: when the operating pressure ratio of the system increases, the change amplitude of the valve opening change decreases, or when the operating pressure ratio of the system decreases, the change amplitude of the valve opening change increases.

[0015] According to the second aspect of the present application, the present application provides an air-conditioning system, comprising a unit, a sensor and a controller, wherein the sensor obtains real-time water outlet temperature from the unit, and is characterized in that: the air-conditioning system also includes a hot gas bypass path, and a hot gas bypass valve is provided on the hot gas bypass path, wherein the controller adjusts the load of the system according to the method of adjusting the system load by hot gas bypass as described in the first aspect of the present application.

[0016] By considering the following specific embodiments, drawings and claims, other features, advantages and embodiments of the present application can be set forth or become apparent. In addition, it should be understood that the above-mentioned summary of the invention and the following specific embodiments are exemplary and are intended to provide further explanations without limiting the scope of the claimed application. However, the specific embodiments and specific examples only indicate preferred embodiments of the present application. For those skilled in the art, various changes and modifications within the spirit and scope of the present application will become apparent through this specific embodiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] These and other features and advantages of the present application may be better understood by reading the following detailed description with reference to the accompanying drawings, in which:

[0018] FIG1 shows a schematic structural diagram of the air-conditioning system of the present application.

[0019] FIG2 shows a control flow chart for adjusting system load by hot gas bypass.

[0020] FIG3 is a schematic diagram showing the fluctuation of the actual outlet water temperature with the change of valve opening under different PID control methods.

[0021] FIG4 shows a flow characteristic curve diagram of the electric butterfly valve.

[0022] FIG5A shows a curve diagram showing the relationship between the opening variation of the hot gas bypass valve and the system compression ratio.

[0023] FIG5B shows a curve diagram showing the relationship between the opening variation of the hot gas bypass valve and the system load.

[0024] FIG6 is a block diagram of a controller of the air-conditioning system of the present application, showing the specific components and connection relationships of the controller. DETAILED DESCRIPTION

[0025] The specific embodiments of the present application will be described below with reference to the accompanying drawings of this specification. It should be understood that, where possible, the same or similar reference numerals used in this application refer to the same components.

[0026] FIG1 is a schematic structural diagram of the air-conditioning system of the present application, which is used to illustrate the main functional modules of the air-conditioning system of the present application.

[0027] As shown in FIG1 , the air conditioning system 100 of the present application includes a compressor 102, a condenser 104, an expansion valve 106, and an evaporator 108, which are fluidically connected in sequence. The compressor 102 has an intake port 152 and an exhaust port 154. The intake port 152 of the compressor 102 is fluidically connected to the evaporator 108 via an intake duct 162. The exhaust port 154 of the compressor 102 is fluidically connected to the condenser 104 via an exhaust duct 164. The condenser 104 is fluidically connected to the expansion valve 106, and the expansion valve 106 is fluidically connected to the evaporator 108. It will be apparent to those skilled in the art that an economizer and an economizer expansion valve may be further provided in the air conditioning system 100 according to different energy-saving requirements, and these details will not be further described here.

[0028] The refrigerant piping of air conditioning system 100 exchanges heat with the water flowing in water pipe 166 at evaporator 108. However, the refrigerant in evaporator 108 and the water flowing in water pipe 166 are located in separate pipes and are not in fluid communication with each other. Water pipe 166 includes an inlet pipe 122 and an outlet pipe 124. A normal-temperature water source can flow through inlet pipe 122 to the vicinity of evaporator 108, where it exchanges heat with the refrigerant in evaporator 108. The refrigerant in evaporator 108 removes heat from the normal-temperature water source in inlet pipe 122, resulting in low-temperature water flowing out of outlet pipe 124.

[0029] Continuing with FIG1 , the air conditioning system 100 further includes an evaporator pressure sensor (system suction pressure sensor) 132, a condenser pressure sensor (system exhaust pressure sensor) 134, and a water outlet temperature sensor 116. The evaporator pressure sensor 132 is disposed on the suction pipe 162 between the suction port 152 of the compressor 102 and the evaporator 108, and is used to detect the pressure of the evaporator 108 (the suction pressure of the air conditioning system); the condenser pressure sensor 134 is disposed on the exhaust pipe 164 between the exhaust port 154 of the compressor 102 and the condenser 104, and is used to detect the pressure of the condenser 104 (the exhaust pressure of the air conditioning system); and the water outlet temperature sensor 116 is disposed on the water outlet pipe 124, and is used to detect the actual outlet temperature of the chilled water.

[0030] Continuing with Figure 1, the high-temperature, high-pressure gaseous refrigerant discharged from the exhaust port 154 of the compressor 102 enters the condenser 104, releasing heat and condensing into a medium-temperature liquid refrigerant. The medium-temperature liquid refrigerant flows to the main expansion valve 106. After throttling and reducing the pressure of the main expansion valve 106, it forms a low-temperature gas-liquid two-phase refrigerant and enters the evaporator 108. In the evaporator 108, the low-temperature gas-liquid two-phase refrigerant exchanges heat with the room-temperature water from the water inlet pipe 122, absorbing the water's heat and evaporating into a gaseous refrigerant. Finally, it returns to the compressor 102 through the air intake port 152 of the compressor 102, completing the refrigerant circulation. In the evaporator 108, the room-temperature water in the water inlet pipe 122 exchanges heat with the low-temperature gas-liquid two-phase refrigerant, releasing heat and forming low-temperature chilled water, which flows out of the water outlet pipe 124, completing the heat exchange between the water and the refrigerant.

[0031] As shown in FIG1 , air conditioning system 100 further includes a hot gas bypass path 170 , which fluidically connects condenser 104 and evaporator 108 . This hot gas bypass path 170 is used to bypass the high-temperature gaseous refrigerant in condenser 104 to evaporator 108 , thereby affecting heat exchange between water and the refrigerant in evaporator 108 and regulating system load. A hot gas bypass valve 110 is provided on hot gas bypass path 170 to regulate the flow of refrigerant in hot gas bypass path 170 .

[0032] Continuing with FIG1 , the air-conditioning system 100 further includes a controller 112, which is respectively communicated with the evaporator pressure sensor 132, the condenser pressure sensor 134, the outlet water temperature sensor 116 and the hot gas bypass valve 110, and is used to respectively receive the pressure parameters of the evaporator 108, the pressure parameters of the condenser 104 and the actual outlet water temperature parameters of the chilled water, and calculate the valve opening change of the hot gas bypass valve 110 according to the received parameters and the target outlet water temperature set in advance, and adjust the valve opening of the hot gas bypass valve 110 according to the calculated valve opening change, thereby controlling the actual outlet water temperature of the chilled water.

[0033] FIG2 shows a control flow chart for adjusting system load by hot gas bypass.

[0034] As shown in FIG. 2 , in step 202 , when the air conditioning system enters the water temperature adjustment process in the hot gas bypass phase, the process goes to step 206 .

[0035] In step 206 , the controller 112 collects the actual chilled water outlet temperature parameter collected by the outlet water temperature sensor 116 in real time within the preset water temperature adjustment period, and simultaneously obtains the pre-set target outlet water temperature parameter. After step 206 is completed, the process proceeds to step 208 .

[0036] In step 208, the controller 112 compares the actual chilled water outlet temperature parameters collected in step 206 with the set target water outlet temperature parameters to determine the changing trend of the actual water outlet temperature relative to the target water outlet temperature, that is, the changing trend of the absolute value of the difference between the actual water outlet temperature and the target water outlet temperature.

[0037] If the absolute value of the difference between the actual outlet water temperature and the target outlet water temperature has an increasing trend, the process goes to step 210; if the absolute value of the difference between the actual outlet water temperature and the target outlet water temperature has a decreasing trend, the process goes to step 230; if the absolute value of the difference between the actual outlet water temperature and the target outlet water temperature remains unchanged, the process goes to step 260.

[0038] In steps 210 and 212, the valve opening change A of the hot gas bypass valve 110 is calculated using the PID control method based on the collected actual chilled water outlet temperature parameters and the set target water outlet temperature parameters. The function formula of the PID control method is as follows:

[0039] rc=error×A×T i +B×rate×K p ,

[0040] Where rc represents the change in valve opening, error represents the absolute value of the difference between the current water temperature and the target water temperature, rate represents the actual water temperature difference between the current cycle and the previous cycle, and A and B are constants. Through the unit debugging of the air conditioning system, several groups of K are obtained under different working conditions. p 、T i and T d The value of K p =5, T i =80, T d =0, or K p =50, T i =10, T d =0.

[0041] After the operations of steps 210 and 212 are completed, the process goes to step 214 .

[0042] In step 214 , the controller 112 compares the collected actual chilled water outlet temperature parameters with the set target water outlet temperature parameters to determine the relationship between the actual water outlet temperature and the target water outlet temperature.

[0043] If the actual outlet water temperature is greater than the target outlet water temperature, the process goes to step 216, and the valve opening is reduced by the change A; if the actual outlet water temperature is less than the target outlet water temperature, the process goes to step 220, and the valve opening is increased by the change A; if the actual outlet water temperature is equal to the target outlet water temperature, the process goes to step 218, and the valve opening remains unchanged.

[0044] In steps 230 and 232, the valve opening change B of the hot gas bypass valve 110 is calculated using the close PID control method based on the collected actual chilled water outlet temperature parameters and the set target water outlet temperature parameters. The function formula of the close PID control method is basically the same as the function formula of the far PID control method. The difference is that the several groups of K p 、T i and T d The values ​​of K are different, for example, p =5, T i =60, T d =0.

[0045] After the operations of steps 230 and 232 are completed, the process goes to step 234.

[0046] In step 234 , the controller 112 compares the collected actual chilled water outlet temperature parameters with the set target water outlet temperature parameters to determine the relationship between the actual water outlet temperature and the target water outlet temperature.

[0047] If the actual outlet water temperature is greater than the target outlet water temperature, the process goes to step 236, and the valve opening is reduced by the change amount B; if the actual outlet water temperature is less than the target outlet water temperature, the process goes to step 240, and the valve opening is increased by the change amount B; if the actual outlet water temperature is equal to the target outlet water temperature, the process goes to step 238, and the valve opening remains unchanged.

[0048] In step 260, since the actual outlet water temperature remains constant relative to the target outlet water temperature, the change in valve opening remains the same as in the previous adjustment cycle. If the valve opening was adjusted using the Far PID control method in the previous adjustment cycle, the valve opening will also be adjusted using the Far PID control method in this cycle. Similarly, if the valve opening was adjusted using the Close PID control method in the previous adjustment cycle, the valve opening will also be adjusted using the Close PID control method in this cycle.

[0049] After the operations of steps 216 , 218 , 220 , 236 , 238 , 240 and 260 are completed, the process goes to step 252 .

[0050] In step 252, after the current adjustment cycle, the controller 112 determines whether a shutdown is required (e.g., the air conditioning system needs to be shut down for maintenance). If a shutdown is required, the process proceeds to step 254 to perform the shutdown operation. If a shutdown is not required, the process proceeds to step 256 to perform the next water temperature fluctuation adjustment cycle, and the control process of steps 206 to 252 is repeated.

[0051] FIG3 is a schematic diagram showing the fluctuation of the actual outlet water temperature with the change of valve opening under different PID control methods.

[0052] As shown in FIG3 , curve 302 shows the temporal fluctuation of the valve opening of the hot gas bypass valve 110 under the single PID control mode; curve 304 shows the temporal fluctuation of the actual outlet water temperature under the single PID control mode; curve 312 shows the temporal fluctuation of the valve opening of the hot gas bypass valve 110 under the dual PID control mode of the present application (separate control of the far PID and the near PID); and curve 314 shows the temporal fluctuation of the actual outlet water temperature under the dual PID control mode of the present application (separate control of the far PID and the near PID). Dashed line 310 represents the setpoint of the target outlet water temperature.

[0053] As can be seen, within a water temperature fluctuation regulation cycle, the process of increasing valve opening represents the air conditioning system unit's load reduction, while the process of decreasing valve opening represents the air conditioning system unit's load reduction. When the actual outlet water temperature is lower than the target outlet water temperature, the unit needs to be unloaded to raise the actual outlet water temperature to the target water temperature; when the actual outlet water temperature is higher than the target outlet water temperature, the unit needs to be loaded to lower the actual outlet water temperature to the target water temperature.

[0054] Due to the principle of hot gas bypass regulating unit load, the actual outlet water temperature response during the air conditioning system's load reduction and loading processes exhibits a certain lag, meaning that the actual outlet water temperature change lags behind the valve opening change. For example, when the valve opening increases (unit load reduction), the water temperature does not immediately rise. Instead, it continues to fall for a while, following the previous downward trend, and then rises in response to the increased valve opening. When the valve opening decreases (unit load), the water temperature does not immediately fall. Instead, it continues to rise for a while, following the previous upward trend, and then falls in response to the decreased valve opening.

[0055] Continuing with Figure 3, for ease of understanding, the process in which the actual outlet water temperature moves away from the target outlet water temperature during the load reduction process is defined as the load reduction moving away process, the process in which the actual outlet water temperature approaches the target outlet water temperature during the load reduction process is defined as the load reduction moving away process, and the process in which the actual outlet water temperature approaches the target outlet water temperature during the load reduction process is defined as the load reduction moving away process. The load reduction moving away process corresponds to step 220 in Figure 2, the load reduction moving away process corresponds to step 240 in Figure 2, the load reduction moving away process corresponds to step 216 in Figure 2, and the load reduction moving away process corresponds to step 236 in Figure 2. Due to the hysteresis of the hot gas bypass load regulation, during the load reduction and load reduction phases, the moving away PID control method requires a larger action amplitude (i.e., a larger valve opening adjustment) to respond to the change in water temperature away from the target value. However, during the load reduction and load reduction phases, the moving away PID control method requires a smaller action amplitude (i.e., a smaller valve opening adjustment) to release the energy generated by the previous large action amplitude.

[0056] As can be seen from Figure 3, the actual outlet water temperature curve 314 under the dual PID control mode of the present application (control of the far PID and the close PID separately) has a smaller fluctuation amplitude than the actual outlet water temperature curve 304 under the single PID control mode. In the embodiment of the present application, when the dual PID control mode is adopted, the fluctuation amplitude of the actual outlet water temperature can be controlled within the range of ±0.2°C. If the dual PID control mode is not adopted and only the single PID control mode is adopted, the fluctuation amplitude of the actual outlet water temperature will reach ±0.5°C, which is much higher than the water temperature fluctuation amplitude when the dual PID control mode is adopted. Therefore, the dual PID control mode of the present application has a more accurate control over the water temperature. Similarly, the valve opening curve 312 under the dual PID control mode of the present application has a smaller fluctuation amplitude than the valve opening curve 302 under the single PID control mode. From the perspective of system control, the smaller adjustment of the valve opening of the present application is more energy-efficient than the valve opening adjustment in the prior art.

[0057] Figure 4 shows a flow characteristic curve of an electric butterfly valve. The hot gas bypass valve 110 of the present application uses an electric butterfly valve. According to the flow characteristics of the electric butterfly valve, the change in the opening of the electric butterfly valve and the change in the refrigerant flow through the electric butterfly valve are not linearly related, but rather follow a curve relationship as shown in Figure 4.

[0058] As shown in Figure 4, when the opening of the electric butterfly valve is small, the refrigerant flow rate does not change significantly with the opening. As the opening of the electric butterfly valve increases, the change amplitude of the refrigerant flow rate with the opening gradually increases. That is, the larger the opening of the electric butterfly valve, the greater the rate of change of the refrigerant flow rate with the valve opening, and the smaller the opening of the electric butterfly valve, the smaller the rate of change of the refrigerant flow rate with the valve opening.

[0059] 5A-5B show the relationship between the opening variation of the hot gas bypass valve and the system compression ratio and the unit load.

[0060] 5A-5B are schematic diagrams showing how the opening adjustment range of the hot gas bypass valve changes with changes in the system compression ratio and system load during the process of the air conditioning system unit entering the hot gas bypass load reduction stage.

[0061] As shown in Figure 5A , based on the flow characteristics of the hot gas bypass valve and the system compression ratio, a higher system compression ratio (i.e., a higher ratio of the pressure at condenser 104 to the pressure at evaporator 108) indicates a higher pressure at condenser 104, which translates to a higher refrigerant vapor temperature. At this point, at the same opening of the hot gas bypass valve 110, the refrigerant vapor energy flowing through the hot gas bypass path 170 increases. In other words, during loading or unloading, the same opening away from the PID calculation has a greater impact on the load. Therefore, the action amplitude of the hot gas bypass valve close to the PID needs to be reduced to better cope with the load impact caused by the bypass of higher-energy gas. Similarly, during loading or unloading, if the position close to the PID is fixed, the higher the system compression ratio, the smaller the action amplitude of the hot gas bypass valve calculated away from the PID needs to be reduced to offset the greater load impact of the valve opening in the previous cycle. In short, the higher the system compression ratio, the smaller the adjustment (variation) of the hot gas bypass valve 110's valve opening; the higher the system compression ratio, the larger the adjustment (variation) of the hot gas bypass valve 110's valve opening.

[0062] The size of the system load can be partially reflected in the difference between the inlet and outlet water temperatures or the difference between the actual outlet water temperature and the target outlet water temperature. As shown in Figure 5B, when the other operating environments of the system are the same, the greater the temperature difference, the greater the system load; the smaller the temperature difference, the smaller the system load. Furthermore, the lower the system load is, the greater the opening of the hot gas bypass valve; the greater the system load is, the smaller the opening of the hot gas bypass valve. Combined with the flow characteristic curve of the electric butterfly valve shown in Figure 4, when the valve opening is relatively large, the same valve action amplitude will bring about a greater flow change, and the impact on the system load will be greater. Based on the above valve characteristics, when the system load is relatively low, reducing the valve opening adjustment (variation) amplitude is more conducive to the stability of the water temperature.

[0063] Figure 6 is a controller block diagram of the air conditioning system of the present application, illustrating the specific components and connections of the controller 112. The controller 112 can store and execute the program of the control flow shown in Figure 2, and store and call various parameters required for the control flow.

[0064] As shown in FIG6 , the system controller 112 includes a bus 602, a processor 604, a memory 606, an input interface 608, and an output interface 610. The processor 604, the memory 606, the input interface 608, and the output interface 610 are connected to the bus 602. The processor 604 can read a program (or instruction) from the memory 606 and execute the program (or instruction) to process data; the processor 604 can also write data or a program (or instruction) into the memory 606. The memory 606 can store programs (instructions) or data. By executing the instructions in the memory 606, the processor 604 can control the memory 606, the input interface 608, and the output interface 610. In the present application, the memory 606 can store the program for executing the process shown in FIG2 and the operating parameters required to execute the program.

[0065] The input interface 608 is configured to measure or collect the actual outlet water temperature parameters of the chilled water, detect the pressure parameters of the evaporator 108 and the pressure parameters of the condenser 104 through the connecting lines 142, 144, and 146 respectively through the outlet water temperature sensor 116, the evaporator pressure sensor 132 and the condenser pressure sensor 134, and convert these parameter data into signals recognizable by the processor 604 and store them in the memory 606.

[0066] The processor 604 is configured to calculate the change in the hot gas bypass valve opening according to a program stored in the memory 606 and to send a valve opening change adjustment signal to the output interface 610. The output interface 610 is configured to receive the valve opening change adjustment signal from the processor 604, convert the valve opening change adjustment signal into a valve control signal suitable for the hot gas bypass valve 110, and transmit the valve control signal to the hot gas bypass valve 110 via the connection line 151 to adjust the valve opening.

[0067] The method of regulating system load by hot gas bypass in this application has the following advantages over the control methods in the prior art:

[0068] First, compared with the single PID control method in the prior art, this application adopts an independent PID control method, namely, a dual PID control method, according to the different fluctuation trends of the water temperature approaching or far away from the target value, so that the system's control over the water temperature is more precise and stable, and the fluctuation amplitude of the water temperature is smaller.

[0069] Second, compared with the single PID control method in the prior art, the water temperature fluctuation in the dual PID control method of the present application is more stable, so that the valve opening adjustment range of the hot gas bypass valve can be smaller, so the air-conditioning system is more energy-efficient than the single PID control method.

[0070] Although the present application has been described in conjunction with the examples of the embodiments outlined above, it is likely that various alternatives, modifications, variations, improvements and / or substantial equivalents, whether known or currently or soon foreseeable, will be apparent to those skilled in the art. In addition, the technical effects and / or technical problems described in this specification are exemplary and not restrictive; so the disclosures in this specification may be used to solve other technical problems and have other technical effects and / or may solve other technical problems. Therefore, the examples of the embodiments of the present application as stated above are intended to be illustrative and not restrictive. Various changes may be made without departing from the spirit or scope of the present application. Therefore, the present application is intended to include all known or earlier developed alternatives, modifications, variations, improvements and / or substantial equivalents.

Claims

1. A method for regulating system load by hot gas bypass, characterized in that The method comprises the following steps: S01, obtaining the real-time outlet water temperature and the target outlet water temperature; S02, determining the magnitude relationship between the real-time outlet water temperature and the target outlet water temperature and the change trend of the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature; S03, determining the change in the valve opening of the hot gas bypass according to the relationship between the real-time outlet water temperature and the target outlet water temperature determined in step S02 and the change trend of the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature; S04, adjusting the valve opening of the hot gas bypass according to the valve opening variation determined in step S03, thereby adjusting the system load.

2. The method for regulating system load by hot gas bypass according to claim 1, characterized in that: Steps S01 to S04 are cyclically executed in a set water temperature adjustment cycle.

3. The method for regulating system load by hot gas bypass according to claim 1, characterized in that: In step S03, if the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature has an increasing trend, the first PID control method is used to determine the change in the valve opening of the hot gas bypass; or If the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature has a decreasing trend, the second PID control method is used to determine the change in the valve opening of the hot gas bypass.

4. The method for regulating system load by hot gas bypass according to claim 1, characterized in that: In step S03, if the real-time outlet water temperature is greater than the target outlet water temperature and the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature has an increasing trend, in step S04, the valve opening of the hot gas bypass is reduced; If the real-time outlet water temperature is lower than the target outlet water temperature and the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature has an increasing trend, in step S04, the valve opening of the hot gas bypass is increased; If the real-time outlet water temperature is greater than the target outlet water temperature and the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature has a decreasing trend, in step S04, the valve opening of the hot gas bypass is reduced; or If the real-time outlet water temperature is lower than the target outlet water temperature and the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature has a decreasing trend, the valve opening of the hot gas bypass is increased in step S04.

5. The method for regulating system load by hot gas bypass according to claim 3, characterized in that: The first PID control method has a first set of control parameters, The second PID control method has a second set of control parameters, The first group of control parameters is different from the second group of control parameters, and the first group of control parameters and the second group of control parameters are obtained through system debugging.

6. The method for regulating system load by hot gas bypass according to claim 5, characterized in that: The first set of control parameters includes a first proportional coefficient, a first integral time constant and a first differential time constant, The second set of control parameters includes a second proportional coefficient, a second integral time constant, and a second differential time constant.

7. The method for regulating system load by hot gas bypass according to claim 1, characterized in that: When the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature increases, the amplitude of the change in the valve opening increases, or When the variation trend of the absolute value of the difference between the real-time outlet water temperature and the target outlet water temperature decreases, the variation amplitude of the valve opening variation decreases.

8. The method for regulating system load by hot gas bypass according to claim 1, characterized in that: When the operating pressure ratio of the system increases, the amplitude of the change in the valve opening decreases, or When the operating pressure ratio of the system decreases, the amplitude of the change in the valve opening increases.

9. An air conditioning system, comprising a unit, a sensor and a controller, wherein the sensor obtains the real-time outlet water temperature from the unit, characterized in that: The air conditioning system further comprises a hot gas bypass path, on which a hot gas bypass valve is arranged, wherein The controller adjusts the load of the system according to the method for adjusting the load of the system by hot gas bypass according to any one of claims 1 to 8.

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