Intelligent temperature regulating system for industrial water chiller

Abstract

The application relates to the technical field of non-electric variable control, and discloses an industrial water chiller temperature intelligent regulation system, which comprises a refrigeration cycle loop and a control unit. The control unit calculates a steady-state control component based on water outlet temperature deviation, differentiates refrigerant pressure to extract a gradient, and generates a transient compensation component when the gradient exceeds a dynamic noise threshold. The pressure safety margin is calculated in real time, the gain coefficient is determined according to a nonlinear model, the compensation component amplitude is weighted and corrected by using the coefficient, and the final driving instruction is generated. The application solves the thermal lag problem by using the pressure wave transmission speed advantage, prevents the low-pressure shutdown triggered by the aggressive response through the safety margin constraint mechanism, and realizes the dynamic balance between the control response speed and the system physical safety boundary.

Description

TECHNICAL FIELD

[0001] The present application relates to an industrial water chiller temperature intelligent regulation system, belonging to the technical field of non-electric variable control. BACKGROUND

[0002] In current precision manufacturing, laser processing and chemical reaction scenarios, industrial water chillers are responsible for providing constant temperature cooling fluid to non-constant heat loads. Using an outlet water temperature feedback regulation mechanism, the temperature sensor collects the outlet water temperature and compares it with the set target value. The PID algorithm is used to calculate the deviation to drive the compressor frequency conversion or adjust the electronic expansion valve opening to maintain water temperature stability and precision. Based on the temperature deviation closed-loop control logic, the basic temperature control requirements are met under slow load fluctuation or steady-state operation conditions. However, when facing high-frequency on-off of laser generators or pulse heat release transient of reaction kettles, the inherent physical limitations of the temperature feedback mainstream method are exposed. The heat is transferred from the heat source to the cooling water and transported to the outlet sensor of the water chiller through the circulating pipeline, and there is a delay of several seconds to tens of seconds in the fluid transport that cannot be eliminated. Moreover, due to the integral effect of the thermal capacity characteristics of the temperature sensor, when the control system senses a measurable change in the outlet water temperature, the actual disturbance at the load end has already occurred for a period of time. The time and space mismatch of this physical transmission mechanism causes the control system to respond to the load change in a phase-lag state, making it difficult to meet the precision of ±0.1℃ required by the precision process.

[0003] The prior art attempts to optimize the regulation strategy, but mostly focuses on mechanical structure switching or macroscopic regulation based on environmental temperature, rather than on the transient response of the internal state of the refrigeration cycle. For example, a kind of energy-saving industrial water chiller is disclosed in the Chinese patent with the authorization announcement number CN115540373B, which sets up a separate wind-cooled component and an inner telescopic component, uses artificial intelligence to identify environmental temperature changes to adjust the volume of the cavity in the evaporation cabin and switch the wind-cooled / water-cooled mode, and solves the problem of avoiding mode misjudgment to achieve energy saving under different environmental temperatures. This kind of scheme still essentially relies on external environmental temperature or system steady-state parameter monitoring for control logic, which belongs to large time scale mode switching and energy efficiency optimization. In the face of millisecond-level intense pulse heat shock at the load end, based on the complex mechanical structure action or environmental temperature feedback regulation, it is difficult to overcome the response lag caused by thermal inertia and to achieve transient accurate compensation of refrigeration capacity through mechanical part telescoping.

[0004] Therefore, how to overcome the physical lag of temperature feedback and the dynamic mismatch of refrigerant state change to achieve rapid response to transient load under the premise that the compressor does not trigger low-pressure shutdown has become a technical problem to be solved by the present application. SUMMARY

[0005] To solve the problems raised in the background art, the technical solution of the present application is as follows: an industrial water chiller temperature intelligent regulation system, comprising:

[0006] The refrigeration cycle circuit comprises a variable frequency compressor, a condenser, an electronic expansion valve and an evaporator;

[0007] The temperature acquisition unit is configured to acquire the outlet water temperature of the industrial water chiller.

[0008] The pressure acquisition unit is configured to acquire the refrigerant pressure on the suction side of the variable frequency compressor.

[0009] The control unit internally stores a preset low-pressure protection threshold value and a dynamic noise threshold value, and runs the following control rules: based on the deviation of the outlet water temperature from a preset target temperature, a first control component for maintaining steady-state temperature accuracy is calculated; the refrigerant pressure is subjected to time-domain differentiation processing to extract a pressure change gradient value, and the absolute value of the pressure change gradient value is compared with the dynamic noise threshold value; when the absolute value of the pressure change gradient value exceeds the dynamic noise threshold value, an original second control component for transiently compensating the refrigerating capacity of the refrigeration cycle circuit is generated; the difference between the refrigerant pressure and the low-pressure protection threshold value is calculated in real time as a safety margin of the current operation; a gain correction model internally constructed by the control unit is used to correct the gain coefficient of the original second control component, the gain correction model defines a nonlinear mapping rule between the gain coefficient and the safety margin, the nonlinear mapping rule causes the gain coefficient to nonlinearly decay with the decrease of the safety margin when the safety margin is lower than a preset warning value; the amplitude of the original second control component is weighted and corrected by using the gain coefficient to generate a final second control component, and based on the first control component and the final second control component, a final driving instruction for the variable frequency compressor and the electronic expansion valve is generated.

[0010] Preferably, the control unit identifies that the system is in a load surge state when the pressure change gradient value is positive and exceeds the dynamic noise threshold value; the original second control component includes an instruction to increase the opening degree of the electronic expansion valve by a first preset step within a preset time, and an instruction to increase the rotation speed of the variable frequency compressor by a second preset step; the control unit also runs a weight decay rule, after the final driving instruction is generated, the weight of the final second control component in the final driving instruction is gradually reduced to zero according to a preset time constant as the pressure change gradient value falls.

[0011] Preferably, the dynamic noise threshold value is not a fixed value, but is determined by the control unit in real time based on the current operating frequency of the variable frequency compressor; the control unit internally stores a reference noise map, the reference noise map defines the pressure fluctuation base value caused by the inherent vibration of the variable frequency compressor at different operating frequencies; the control unit queries the reference noise map in real time to update the dynamic noise threshold value.

[0012] Preferably, the control unit continues to monitor the variation trend of the pressure variation gradient during the generation of the final second control component; when detecting an inflection point feature that the pressure variation gradient changes from increasing to decreasing, the control unit identifies the moment as the energy balance point; the control unit performs a state locking operation at the energy balance point, sets the current refrigeration capacity determined by the final second control component as the reference refrigeration capacity for subsequent control, and terminates the further dynamic adjustment of the final second control component, and instead fine-tunes and corrects the reference refrigeration capacity based on the first control component.

[0013] Preferably, the control unit is further configured to calculate a time variation rate of the operating frequency of the variable frequency compressor in real time; when the final second control component drives the variable frequency compressor to accelerate and the time variation rate exceeds a preset acceleration threshold, the control unit generates a third control component for the electronic expansion valve based on the time variation rate; the third control component is used to drive the opening degree of the electronic expansion valve to increase at a rate synchronized with the acceleration of the variable frequency compressor, and the increased amplitude is positively correlated with the time variation rate of the operating frequency of the variable frequency compressor, so as to compensate for the decrease in suction pressure caused by the suction effect of the variable frequency compressor before the evaporation rate of the refrigerant in the evaporator rises.

[0014] Preferably, the system further comprises a second pressure acquisition unit for acquiring the refrigerant pressure on the condensing side; the control unit internally stores a differential pressure gain correction model, which defines a nonlinear mapping relationship between the feedforward adjustment gain and the system operating differential pressure; the control unit calculates the differential pressure between the refrigerant pressure on the condensing side and the refrigerant pressure on the suction side of the variable frequency compressor in real time, and determines the current differential pressure correction coefficient according to the differential pressure gain correction model; when generating the final second control component, the control unit performs weighted scaling on the amplitude of the final second control component by using the differential pressure correction coefficient.

[0015] Preferably, the control unit is configured to monitor the opening degree adjustment instruction sent to the electronic expansion valve in real time, and calculate an estimated value of the suction pressure variation rate caused by the action of the electronic expansion valve based on a preset valve pressure response model; when extracting the pressure variation gradient value, the control unit performs signal decoupling operation, subtracts the estimated value from the measured differential value of the refrigerant pressure, and obtains a net pressure gradient value representing the external thermal load disturbance; when the absolute value of the net pressure gradient value exceeds a dynamic noise threshold, the control unit generates the original second control component.

[0016] Preferably, the control unit is further configured to monitor the suction superheat of the suction side of the variable frequency compressor in real time, and calculate the time rate of change of the suction superheat; in generating the third control component to drive the electronic expansion valve to increase the opening degree, the control unit performs a logical check: when the time rate of change of the suction superheat is detected to be negative and the absolute value exceeds a preset safety threshold, it is identified as a wet compression risk state, and the control unit immediately masks or reverses the third control component, forces to maintain or reduce the current opening degree of the electronic expansion valve, until the time rate of change of the suction superheat returns to a safe range.

[0017] Preferably, the control unit uses a sliding window algorithm to perform time domain differentiation on the refrigerant pressure, and the time length of the sliding window is set to be less than the fluid transport delay time required for the cooling fluid in the refrigeration cycle loop to be transported from the heat source to the temperature acquisition unit.

[0018] Preferably, the gain coefficient defined in the gain correction model and the safety margin satisfies the following relationship: wherein, is a preset warning value, is a low pressure protection threshold, is a preset decay index greater than 1, for setting the decay rate of the gain coefficient when approaching the low pressure protection threshold.

[0019] Compared with the prior art, the beneficial effects of the present application are:

[0020] 1. The time domain variation characteristics of the compressor suction side refrigerant pressure are collected, and the load mutation state is identified and a compensation instruction is generated before the outlet water temperature changes measurably due to load disturbance, based on the physical characteristic that the pressure wave pipeline transmission speed is faster than the fluid heat transport speed. The control blind area caused by heat transfer delay and sensor integral effect in the traditional temperature feedback loop is eliminated based on the phase advance control mechanism of non-electric variable gradient characteristics, so that the refrigeration system can establish a preset cooling capacity for transient heat shock and suppress water temperature dynamic overshoot at the moment of load mutation.

[0021] 2. The dynamic coupling relationship between the compressor operating frequency change rate and the throttling device opening degree adjustment rate is established, and when detecting the load sudden increase driving the compressor acceleration transient process, a synchronous liquid injection instruction of the throttling device is generated based on the compressor acceleration, and the compressor mechanical pumping rate and the evaporator refrigerant supply rate are forced to be synchronized in the time dimension, so as to avoid the physical mismatch that the evaporation of refrigerant in the evaporator lags behind the mechanical action of the compressor, prevent the instantaneous low pressure fault of the suction side or the evaporation of the evaporator caused by the sharp acceleration of the compressor, and ensure the mass flow balance and heat exchange efficiency of the system under the condition of extremely fast response.

[0022] 3. The use of the inflection point of the suction pressure change gradient trend as the anchor point for feedforward control and feedback control logic switching, precise locking of the energy balance physical moment by monitoring the zero crossing characteristics of the second derivative of the pressure, identifying the independence of the hysteresis temperature signal, stopping open-loop compensation and smoothly transferring to closed-loop fine tuning at the moment of load disturbance suppression, avoiding excessive compensation or exiting hysteresis to cause energy surplus and secondary temperature oscillation, realizing seamless transition from transient burst response to stable high-precision maintenance; Introducing decoupling logic based on valve action prediction signal, calculating the theoretical influence component of the throttling device current action on the suction pressure and separating it from the measured total pressure gradient, obtaining the net pressure gradient value representing external heat load change, this endogenous disturbance filtering mechanism decouples the superimposed influence of system regulation action and external load disturbance on the control variable, preventing false feedforward response induced by conventional throttling device regulation action, ensuring the logic purity and stability of the multivariable control system when performing adaptive regulation. BRIEF DESCRIPTION OF DRAWINGS

[0023] Fig. 1 The system control logic and signal processing flowchart of the present application;

[0024] Fig. 2 The pressure signal phase lead characteristic curve of the present application;

[0025] Fig. 3 The four function modules of the intelligent regulation strategy of the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be described in detail below, and the described embodiments are part of the embodiments of the present application, not all embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the present application.

[0027] The present application provides an industrial water chiller temperature intelligent regulation system, comprising a refrigeration cycle circuit, a temperature acquisition unit, a pressure acquisition unit and a control unit. The refrigeration cycle circuit includes a variable frequency compressor, a condenser, an electronic expansion valve and an evaporator, forming a complete refrigerant circulation channel. The temperature acquisition unit is arranged at the outlet of the water chiller, such as a high-precision thermistor or platinum resistance, which acquires the outlet water temperature in real time. The pressure acquisition unit is arranged at the suction line of the variable frequency compressor, such as a pressure sensor, which acquires the refrigerant pressure on the suction side of the compressor in real time , a control unit such as a microcontroller or digital signal processor, maintains signal connection with the temperature acquisition unit, the pressure acquisition unit, and the variable frequency compressor and electronic expansion valve in the refrigeration cycle loop; during steady-state operation, the control unit calculates a first control component for maintaining the steady-state temperature accuracy based on the deviation between the outlet water temperature collected by the temperature acquisition unit and the preset target temperature through a proportional-integral-derivative algorithm, and the first control component is used for fine adjustment of the variable frequency compressor and the electronic expansion valve to cope with small fluctuations in thermal load; based on the physical lag of temperature feedback control, the control unit runs transient compensation logic, and the control unit acquires the original refrigerant pressure sequence from the pressure acquisition unit at a high sampling frequency , such as 20 Hz, and extracts pressure change gradient values through time domain differential processing of the pressure sequence , the time domain differential processing is realized by a sliding window algorithm, and the sliding window time length is set to 500 ms, which is less than the fluid transport delay time required for the cooling fluid in the refrigeration cycle loop to be transported from the heat source to the temperature acquisition unit, such as more than 5 seconds, so that the gradient value is obtained physically before the temperature change; to prevent false responses caused by pressure fluctuations due to compressor vibration, the control unit compares the absolute value of the pressure change gradient value with a dynamic noise threshold , the dynamic noise threshold is not a fixed value, but is determined in real time by the control unit based on the current operating frequency of the variable frequency compressor, and the control unit internally stores a reference noise map obtained through offline calibration experiments to limit the base value of the pressure fluctuation caused by inherent vibration of the variable frequency compressor at different operating frequencies, such as 30 Hz to 90 Hz, and the control unit updates the dynamic noise threshold in real time by querying the reference noise map , only when and the state duration exceeds a confirmation window such as 200 ms, the control unit determines that this signal is a thermal load disturbance, and generates an original second control component for transient compensation of the refrigeration capacity of the refrigeration cycle loop.

[0028] In a preferred implementation, to distinguish between external load disturbance and pressure change caused by system self-adjustment action, the control unit performs signal decoupling operation when extracting the pressure change gradient value, and the control unit monitors the opening adjustment instruction sent to the electronic expansion valve in real time, calculates the estimated value of the suction pressure change rate caused by the action of the electronic expansion valve based on a preset valve pressure response model such as a simplified linear transfer function , the control unit subtracts the estimated value from the measured differential value of the refrigerant pressure to obtain the net pressure gradient value characterizing the external thermal load disturbance , in this case, the control unit only determines that the signal is a thermal load disturbance when the absolute value of the net pressure gradient value When the pressure is lower than the preset low-pressure protection threshold, the control unit generates an original second control component; after generating the original second control component, the control unit performs a safety constraint check to prevent a shutdown caused by an overactive response in a low-pressure working condition, and the control unit internally stores a preset low-pressure protection threshold The control unit calculates the refrigerant pressure in real time, such as 0.2 bar The difference between the low-pressure protection threshold and the current pressure is taken as a current operation safety margin The control unit determines a gain correction coefficient of the original second control component according to an internally constructed gain correction model The gain correction model limits the gain correction coefficient to be positively correlated with the safety margin in a nonlinear mapping rule, and when the safety margin is lower than a preset warning value , such as 2.0 bar, the gain correction coefficient decreases in a nonlinear manner with the safety margin , and in a specific implementation, the nonlinear mapping rule satisfies the following relationship: wherein is the preset warning value, represents a calculation reference slightly higher than a physical shutdown threshold, is a preset attenuation index greater than 1, such as 2, used to set an attenuation rate of the gain correction coefficient when the pressure is close to the low-pressure protection threshold, and the control unit corrects an amplitude of the original second control component by using the gain correction coefficient to generate a final second control component, and the correction limits an acceleration rate of the compressor in the low-pressure working condition.

[0029] To improve the system's adaptability to environmental conditions, the system also includes a second pressure acquisition unit for acquiring refrigerant pressure on the condenser side. The control unit internally stores a differential pressure gain correction model, defining a nonlinear mapping relationship between the feedforward adjustment gain and the system operating differential pressure. The control unit calculates the differential pressure between the condenser-side refrigerant pressure and the variable frequency compressor suction-side refrigerant pressure in real time. Based on the differential pressure gain correction model, it determines the current differential pressure correction coefficient. When generating the final second control component, the control unit uses the differential pressure correction coefficient to reweight and scale the amplitude of the final second control component or the original second control component again to compensate for the drift in refrigerant pressure response characteristics caused by changes in environmental conditions. When the control unit detects a positive pressure change gradient value... When the dynamic noise threshold is exceeded, the identification system is in a state of sudden load increase. At this time, the original second control component includes the following instructions: increase the opening of the electronic expansion valve by a first preset step size within a preset time, such as increasing the opening by 10%; and increase the speed of the variable frequency compressor by a second preset step size, such as an instantaneous increase of 20Hz. The instructions are used to pre-increase the refrigerant flow and enhance the cooling capacity before the water temperature rises, thus neutralizing the impending thermal shock. When the system is in a state of sudden load increase, during the acceleration process of the variable frequency compressor driven by the second control component, there is a dynamic mismatch problem where the compressor suction rate is faster than the evaporator evaporation rate. To solve this problem, the control unit calculates the rate of change of the variable frequency compressor's operating frequency over time in real time. When the rate of change over time When the preset acceleration threshold is exceeded, the control unit determines the acceleration rate based on the time change rate. Generate the third control component for the electronic expansion valve The third control component This is used to drive the electronic expansion valve opening to increase synchronously with the acceleration rate of the variable frequency compressor, and the increase magnitude is related to the rate of change of the variable frequency compressor's operating frequency over time. There is a positive correlation. Before the refrigerant evaporation rate in the evaporator increases, the active compensation for the decrease in suction pressure caused by the suction action of the variable frequency compressor is used. To prevent the risk of wet compression caused by synchronous liquid injection, the control unit monitors the suction superheat of the variable frequency compressor in real time. Calculate the rate of change of intake superheat over time. Generate the third control component During the process of increasing the opening of the electronic expansion valve, the control unit performs a logic check: when the rate of change of intake superheat over time is detected... Negative and with an absolute value exceeding the preset safety threshold At times, such as If the system identifies a wet compression risk condition, the control unit immediately disables or reverses the third control component. The current opening of the electronic expansion valve is forcibly maintained or reduced until the rate of change of intake superheat time returns to a safe range.

[0030] The transient compensation exit mechanism is used to achieve smooth control switching. In the preferred implementation, the control unit continuously monitors the pressure change gradient trend during the generation of the final second control component. When the pressure change gradient is detected... or When the inflection point characteristic changes from increasing to decreasing, this inflection point characteristic corresponds to the zero-crossing point of the second derivative. The control unit identifies this moment as the energy balance point, indicating that the rate of increase in cooling capacity and the thermal shock rate have reached a balance. The control unit performs a state lock operation at the energy balance point, and the current cooling capacity is determined by the final second control component and set as the reference cooling capacity for subsequent control. This cooling capacity is determined by the current compressor frequency and valve opening. The final second control component is dynamically adjusted, and the reference cooling capacity is fine-tuned based on the first control component. In another implementation, the control unit runs a weight decay rule. After generating the final drive command, as the pressure change gradient value falls back, it gradually reduces the weight of the final second control component in the final drive command according to a preset time constant, such as 3 seconds until the weight returns to zero, and smoothly restores the weight of the first control component. Finally, based on the first control component and the final second control component, in the decoupling operation of the pressure change gradient extraction signal, the control unit adopts a recursive correction strategy to maintain temporal causality and calculates the current moment. Estimated rate of change of inspiratory pressure Call the previous sampling period The electronic expansion valve opening command is issued, and the theoretical pressure fluctuation value caused by the valve action at the current moment is calculated based on the preset valve pressure response model; the value obtained from the hysteresis calculation is then used... Based on the current measured total pressure gradient Subtracting this yields the net pressure gradient characterizing the abrupt change in external thermal load. To eliminate the real-time coupling of algebraic loops between closed-loop control variables; when identifying the inflection point of the pressure change gradient from increasing to decreasing to determine the energy balance point, the control unit executes trend confirmation logic to filter out high-frequency noise interference from the sensor, and the judgment condition is set as the continuous first-order difference value of the pressure change gradient. The sampling period remains negative and the cumulative decrease exceeds the preset noise tolerance. Example Choose 3, noise margin Set as The calibration is based on the standard deviation of the measured pressure gradient signal during steady-state operation of the system. When the energy balance point is three times the value of the threshold above, the energy balance point is confirmed to have reached the state of execution and locking operation is performed; for dynamic noise threshold... and noise tolerance On-site calibration: The system runs an initialization self-test program, the compressor maintains its minimum speed and the electronic expansion valve opening is fixed at zero load, and 60 seconds of continuous suction pressure data are collected to calculate the gradient statistical distribution; the distribution... quantiles are... Boundary as reference noise base, write dynamic noise threshold Initial lookup table and noise tolerance Register, as a distinction between real load disturbance and inherent mechanical vibration quantization boundary, through weighted summation or logical arbitration, generates the final drive instruction for variable frequency compressor to adjust its operating frequency and electronic expansion valve to adjust the opening degree.

[0031] Embodiment 1: This embodiment is an application example of an industrial water chiller temperature intelligent regulation system in a specific industrial scene. In the application of precision laser processing, the industrial water chiller system provides constant temperature cooling fluid for the high-frequency on-off laser generator. The working condition requires the cooling fluid temperature to be constant at 20.0 , the fluctuation range is not more than ±0.1 , at t0 time, the system is in stable operation, the laser generator is on standby, the thermal load is extremely low, the control unit maintains the variable frequency compressor at 35Hz low frequency operation based on the first control component, and the outlet water temperature is stable at 20.0 , at this time, the suction side refrigerant pressure is stable at 0.5bar, and this pressure value corresponds to a safety margin of 0.3bar, which is lower than the preset warning value , at t1 time, the laser generator is started instantaneously and enters the full power pulse working mode, the thermal shock is applied to the evaporator, causing the refrigerant in the evaporator to boil, and the pressure acquisition unit monitors that the suction side refrigerant pressure starts to rise rapidly, the control unit extracts the pressure change gradient value through time domain differentiation processing , and the absolute value exceeds the dynamic noise threshold determined based on the current 35Hz frequency at t1+200ms , the system identifies as a load surge state, and due to the fluid transport delay and the temperature sensor thermal capacity, the outlet water temperature reading of the temperature acquisition unit is still 20.0 ; the control unit generates the original second control component, which contains the drive compressor acceleration and electronic expansion valve opening instruction, and before generating the final second control component, the control unit performs safety margin check, and in view of the current safety margin of only 0.3bar, which is lower than the warning value , the control unit calculates the low gain coefficient according to the internal gain correction model , the control unit uses the gain coefficient to weight and correct the amplitude of the compressor acceleration instruction in the original second control component, and the final second control component is corrected as follows: increase the opening degree of the electronic expansion valve to introduce refrigerant, and slightly increase the speed of the variable frequency compressor to avoid triggering low pressure shutdown due to instantaneous low suction in the low pressure area. With the opening of the electronic expansion valve and the influx of refrigerant, the suction side refrigerant pressure returns to the safety interval, and the safety margin followed by an increase and exceeding the warning value , the gain factor is restored to 1, at which time the control unit removes the compressor acceleration limit, and the final second control component containing the full amplitude command drives the variable frequency compressor to rapidly increase in frequency, to cope with the sustained heat load shock, and the control unit calculates the time rate of change of the variable frequency compressor operating frequency At this time, it is monitored that the value exceeds the preset acceleration threshold.

[0032] To prevent the risk of low pressure caused by the mismatch between the high speed suction of the variable frequency compressor and the evaporation rate of the evaporator, the control unit generates a third control component based on the time rate of change , which drives the electronic expansion valve opening to continuously increase at a synchronous rate with the compressor acceleration, at t1+2s, the control unit performs a logical check to monitor the time rate of change of the suction superheat , which appears to be negative, and the absolute value exceeds the preset safety threshold , the control unit determines that there is a risk of wet compression, and immediately temporarily shields the third control component , forcing the current opening of the electronic expansion valve to be maintained, until t1+2.5s, when the time rate of change of the suction superheat returns to the safe range, the third control component is restored to be executed, to ensure mass flow balance while avoiding compressor liquid knock, at t1+4s, the control unit continuously monitors the pressure change gradient trend, detects that the inflection point feature changes from increasing to decreasing, the control unit identifies this time as the energy balance point, immediately performs a state locking operation, sets the current refrigeration capacity as the subsequent control reference refrigeration capacity, and terminates the dynamic adjustment of the final second control component, and smoothly transfers control back to the first control component, during the entire t0 to t4s dynamic response process, the maximum fluctuation of the outlet water temperature collected by the temperature collection unit is 20.08 , which is maintained within the accuracy requirement of ±0.1 , the system suppresses transient heat shock before low pressure shutdown or wet compression risk occurs.

[0033] Embodiment 2: This embodiment verifies the actual control effect, system safety and stability of the temperature intelligent adjustment system of the industrial water chiller of the application in response to transient heat load shock, and compares the performance indicators of experimental groups using different control strategies under the same working conditions by building a standardized experimental verification platform; the experimental platform is built in an environmental temperature controllable enthalpy difference laboratory, and the test object is a 5kW variable frequency industrial water chiller, the water chiller is equipped with a variable frequency compressor, an electronic expansion valve, a plate heat exchanger and an air-cooled condenser, a PT100 platinum resistance is used as the temperature collection unit and is installed at the outlet of the evaporator, the sampling frequency is set to 1Hz, and the measurement accuracy is ±0.05 ​, the pressure acquisition unit adopts a piezoresistive pressure sensor, is installed at the suction port of the compressor, the sampling frequency is set to 20Hz, the measurement accuracy is ±0.5%F.S., the control unit adopts an ARM Cortex-M4 core microcontroller, runs the control logic of the application, the load simulation device is a programmable electric heater, and a controlled step heat load is generated; three kinds of comparison control strategies are set in the experiment, and three experimental groups are correspondingly set: the control group 1 is a traditional PID control: based on the temperature acquisition unit, the outlet water temperature deviation is acquired, the first control component is calculated to drive the compressor and the electronic expansion valve, the pressure gradient feedforward logic is not enabled, the control group 2 is a non-constrained feedforward control: based on the control group 1, the pressure change gradient value feedforward control is enabled to generate the original second control component, but the strategy does not introduce a safety margin gain correction model, and the suction superheat time change rate is not introduced wet compression blocking mechanism, the application group is a complete control scheme: the pressure gradient feature extraction, the safety margin nonlinear gain correction, the compressor acceleration throttling valve synchronous compensation, the wet compression blocking mechanism, the second derivative zero-crossing state locking and smooth switching complete control logic are enabled; the experimental condition is set: the environmental temperature is constant 35 , the initial state is that the load simulation device outputs power 1kW, the system is in steady-state operation, and the outlet water temperature is stable 20.0 , at the moment T=0, the load simulation device outputs power step to 5kW, simulates the instantaneous start of the laser generator, and records the data after 10 minutes of continuous operation, and table 1 shows the comparison data of key performance indicators of the three experimental groups under the above working conditions.

[0034] Table 1: Comparison table of dynamic response performance and safety indicators

[0035]

[0036] Technical analysis of the data in table 1 is as follows: the control group 1 relies on a temperature signal with thermal hysteresis, when the temperature rise is detected, the water temperature deviates greatly from the target value due to thermal shock, the maximum temperature deviation reaches +2.5 , and the recovery time is as long as 180 seconds, which cannot meet the ±0.1 temperature control requirement, and it is proved that only feedback control cannot solve the problem of physical space-time dislocation; the control group 2 introduces pressure gradient feedforward, and the compressor is sharply accelerated and the electronic expansion valve is greatly opened through the original second control component in advance before the temperature changes, although the temperature control response is extremely fast in theory, in the experiment, the suction pressure drops to 0.1bar in a short time due to the extremely fast suction of the compressor, which is lower than the preset low-pressure protection threshold 0.2bar, triggering the low-pressure alarm shutdown, and the uncontrolled opening of the electronic expansion valve causes a large amount of refrigerant liquid to rush in, and the suction superheat instantaneously decreases to 0.0 C.

[0037] The group detects the pressure change gradient value Exceeds the dynamic noise threshold After starting the feedforward response, the control unit calculates the safety margin in real time , the gain correction model is used to attenuate the compressor acceleration instruction, the data shows that the minimum value of the suction pressure of the group is 1.8bar, which is in the safety area, when the control unit monitors the time change rate of the suction superheat When the characteristic of negative sharp change is presented, the logic verification mechanism limits the driving amplitude of the electronic expansion valve by the third control component, so that the minimum value of the suction superheat is maintained at 3.5 , avoid wet compression, finally, the temperature maximum deviation is suppressed within +0.15 , within 35 seconds, the system does not fail; the experimental results show that the invention uses the physical characteristics that the transmission speed of the refrigerant pressure wave is faster than the heat transport speed of the fluid, and combines the safety margin and the trend dynamic constraint mechanism based on the superheat, to realize the advance response to the transient heat load and strictly comply with the physical safety boundary of the system in a single control architecture, solve the inherent contradiction between response speed and running stability of the traditional control scheme.

[0038] Embodiment 3: This embodiment combines Figs. 1 to 3 , a kind of industrial water chiller temperature intelligent regulation system is described, as shown in Fig. 1 , the suction pressure acquired by pressure acquisition unit in real time is subjected to time domain differentiation and signal decoupling processing by pressure gradient extraction module, to generate pressure gradient , the signal is used for determining the dynamic noise threshold value of the reference noise atlas on one hand , when exceeding the threshold value, the second control component is triggered to generate, on the other hand, it is used for safety margin gain correction module, the gain coefficient K is calculated based on safety margin M to correct the second control component, in addition, the outlet water temperature collected by temperature acquisition unit is sent to steady state control logic module, to calculate the first control component based on temperature deviation, in addition, the system also monitors frequency change rate , the third control component is generated by synchronous liquid supplementing module, finally, the first control component, the second control component after correction and the third control component are sent to drive instruction generation and arbitration unit, the unit generates frequency instruction to drive variable frequency compressor to execute frequency regulation, and generates opening degree instruction to drive electronic expansion valve to execute opening degree regulation.

[0039] As shown in Fig. 2 , in the figure, the horizontal coordinate is time second, the left vertical coordinate is pressure gradient bar / s, and the right vertical coordinate is temperature deviation ( The figure clearly shows that this represents the pressure gradient. It responds quickly and rises after a load disturbance, crossing the dynamic noise threshold between 1.0 and 1.5 seconds. It reaches its peak at 3.0 seconds, representing the deviation in outlet water temperature. Due to the thermal hysteresis effect, the response is significantly delayed, reaching its peak at 3.5 seconds. This timing difference confirms the pressure gradient. Relative to temperature deviation It has phase lead characteristics, providing valuable early warning time for the control system; such as Fig. 3 As shown, the system is designed around the central goal of intelligent temperature regulation of industrial chillers. It includes a sensing and feedforward module, which includes functions such as time-domain differential of suction pressure, dynamic noise threshold determination, and decoupling of valve action signals; a safety boundary bundle module, which includes functions such as low-pressure protection threshold, safety margin calculation, and nonlinear gain correction; a transient response coordination module, which includes functions such as synchronous liquid injection of pressure valves, frequency change rate monitoring, and wet compression blocking mechanism; and a steady-state smooth switching module, which includes functions such as energy balance point locking, second derivative zero-crossing recognition, and control weight attenuation.

[0040] Example 4: This example provides a dynamic noise threshold for calibrating pressure gradient feature extraction. Standardized engineering procedures eliminate uncertainties in parameter setting. These procedures apply to the initial configuration or periodic calibration phases of the intelligent temperature control system for industrial chillers of this invention. The initial input definition for the calibration process is: an industrial chiller equipped with the control unit and pressure acquisition unit of this invention, with the chiller in a state of no external heat load connection or connected to a constant zero-load simulator, and the ambient temperature maintained at [temperature value missing]. Under standard operating conditions, the sampling frequency of the pressure acquisition unit is set to 20Hz, and the signal is filtered by a low-pass filter to remove high-frequency electromagnetic interference above 50Hz. The core of the calibration process lies in constructing a reference noise spectrum, which establishes a quantitative mapping relationship between the operating frequency of the variable frequency compressor and the baseline value of the suction pressure fluctuation. The specific execution steps are as follows: Start the variable frequency compressor and set the operating frequency to the lowest operating frequency. For example, at 30Hz, after the system has stabilized, such as after running for 5 minutes, the control unit will begin collecting data for a duration of [duration missing]. For example, 60-second inspiratory pressure time series data The control unit collects data. Performing sliding window differentiation operations that are completely consistent with real-time control logic, the pressure change gradient sequence at this frequency is calculated. Control unit calculation The statistical characteristic value of a sequence is specifically calculated by determining the maximum absolute value or the 99.7th percentile of the sequence. Principle, the statistical characteristic value is defined as the inherent noise base value at the current frequency To ensure control robustness, the base value is multiplied by a safety factor The dynamic noise threshold at the current frequency is obtained The control unit gradually increases the compressor operating frequency in preset frequency steps, such as 5 Hz, until the highest operating frequency is reached such as 90 Hz, for each discrete frequency point, the first to third steps are repeated to obtain a series of corresponding dynamic noise threshold data points; the control unit uses linear interpolation or polynomial fitting method to fit the discrete data points into a continuous frequency threshold curve, and stores the curve data table in the non-volatile memory as a reference noise spectrum, during real-time operation, the control unit determines the current dynamic noise threshold according to the current measured compressor operating frequency

[0041] Embodiment 5: This embodiment provides a standardization engineering calibration procedure for constructing a differential pressure gain correction model and a valve pressure response model, which ensures the control accuracy and stability of the intelligent temperature regulation system of the industrial water chiller under different environmental conditions and different regulation actions; the differential pressure gain correction model construction procedure is as follows: place the industrial water chiller system in an environmental temperature controllable test chamber, and connect a stable heat load simulation load source; set the environmental temperature to a low temperature working condition value, such as 10 After the system is stably operated at the target water temperature, record the system operating pressure difference at this time Under this condition, apply a preset step heat shock to the simulation load source, such as instantaneously increasing 1 kW, and record the peak value of the suction pressure change gradient value measured by the pressure collection unit Set the environmental temperature to a high temperature working condition value, such as 45 Repeat the above operation to record the corresponding high pressure difference The pressure change gradient peak value caused by the same step heat shock under this working condition Through comparison and difference, a nonlinear mapping relationship between pressure gradient response sensitivity and system operating pressure difference is established, which is solidified into a pressure gradient gain correction model stored in the control unit, which is used to weight and scale the final second control component amplitude in real-time operation.

[0042] ​​The valve pressure response model construction procedure is as follows: the industrial water chiller system is operated at a constant heat load, such as 2 kW, and a constant variable frequency compressor frequency, such as 50 Hz, and the outlet water temperature and suction pressure reach a steady state; under this stable working condition, the control unit temporarily suspends all closed-loop regulation logic, actively sends a preset opening degree regulation instruction to the electronic expansion valve at time t0, such as increasing 5 step units; the control unit acquires the suction pressure sequence at a high frequency within a preset time window, such as 2 seconds, after time t0, and calculates the pressure change gradient value of the sequence, since the pressure change is caused by the action of the electronic expansion valve, the gradient value is calibrated as the suction pressure change rate estimation value under the corresponding working condition ; by repeating the injection test at different steady state working points, one or more lookup tables or function models describing the relationship between the valve action and are constructed and stored in the control unit for performing signal decoupling operation in real-time operation.

[0043] Embodiment 6: This embodiment provides a standardization engineering procedure for on-site adaptive setting and optimization of control unit core control parameters under different installed environments and load characteristics, by performing a controlled excitation test after initial deployment or major component replacement of the system, obtaining the real-time response characteristics of the system, and calibrating the decay index and the safety threshold in the wet compression blocking logic in the gain correction model ; the initial input of the setting process is defined as: an industrial water chiller system that has completed physical installation, pipeline connection and meets the nominal value of refrigerant charge, connected to an actual terminal heat load device, before starting the setting, ensure that the environmental temperature is in the effective working range of to , the cooling water circulation system is started and stably operated; the first stage of the setting process is the identification of the open-loop response characteristics of the system, the control unit temporarily freezes the PID closed-loop regulation, sets the variable frequency compressor to a constant reference frequency, such as 40 Hz, and locks the electronic expansion valve at a constant opening degree, after the suction pressure and the outlet water temperature are stable, the control unit sends a step opening degree instruction with an amplitude of to the electronic expansion valve, continuously records the suction pressure step response curve, and extracts the process gain and time constant of the refrigeration system under the current working condition by fitting the response curve.

[0044] The second stage of the setting process is the adaptive calibration of the decay index , based on the process gain identified in the first stage, the control unit calculates the initial decay index The control unit performs a set of closed-loop load disturbance simulation tests: under the premise of keeping the target water temperature constant, a series of virtual load signals with increasing amplitude are artificially introduced or equivalent pressure disturbances are generated by controlling the electronic expansion valve to act quickly, and in each disturbance, the system records the suction pressure undershoot amplitude and recovery time If exceeds the preset safety margin limit, indicating that the response is too aggressive, the control unit increases the value; if exceeds the upper limit of the preset response time, indicating that the response is too slow, the control unit decreases the value, and through iterative optimization, the setting value that makes and be in the optimal balance interval is determined ; the third stage of the setting process is the wet compression safety threshold Field calibration, when the system is in steady-state operation and the suction superheat is in the normal range, such as to , the control unit performs a rapid liquid exploration operation: the electronic expansion valve is driven to open at a preset high speed until the suction superheat starts to decrease significantly or the exhaust temperature starts to drop sharply, and the peak value of the time rate of change of the suction superheat is recorded, and the absolute value of the peak value multiplied by a safety factor such as 0.8 is set as the current system-specific wet compression safety threshold , which ensures that the threshold setting matches the actual state of the current pipeline length, heat exchanger efficiency and refrigerant charge; finally, the parameters and obtained through field calibration are written into the non-volatile configuration area of the control unit as the reference for the operation of the device in the current application environment.

[0045] It is obvious to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application.

[0046] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting, and although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application.

Claims

1. An industrial water chiller temperature intelligent regulating system, characterized in that, The application relates to a control method for a refrigeration cycle circuit of an industrial water chiller. The refrigeration cycle circuit comprises a variable frequency compressor, a condenser, an electronic expansion valve and an evaporator. A temperature acquisition unit is arranged to acquire the outlet water temperature of the industrial water chiller. A pressure acquisition unit is arranged to acquire the refrigerant pressure at the suction side of the variable frequency compressor. A control unit is internally stored with a preset low-pressure protection threshold value and a dynamic noise threshold value, and is provided with the following control rules: based on the deviation between the outlet water temperature and a preset target temperature, a first control component for maintaining the steady-state temperature accuracy is calculated; the refrigerant pressure is subjected to time-domain differential processing to extract a pressure change gradient value, and the absolute value of the pressure change gradient value is compared with the dynamic noise threshold value; when the absolute value of the pressure change gradient value exceeds the dynamic noise threshold value, an original second control component for transiently compensating the refrigerating capacity of the refrigeration cycle circuit is generated; the difference between the refrigerant pressure and the low-pressure protection threshold value is calculated in real time as a safety margin of the current operation; A gain correction model internally constructed by the control unit is used to correct the gain coefficient of the original second control component, the gain correction model defines a nonlinear mapping rule between the gain coefficient and the safety margin, and the nonlinear mapping rule causes the gain coefficient to be nonlinearly attenuated with the decrease of the safety margin when the safety margin is lower than a preset warning value; The gain coefficient is used to weight and correct the amplitude of the original second control component to generate a final second control component, and based on the first control component and the final second control component, a final driving instruction for the variable frequency compressor and the electronic expansion valve is generated.

2. The temperature intelligent regulating system of an industrial water chiller according to claim 1, wherein, When the control unit detects that the pressure change gradient value is positive and exceeds the dynamic noise threshold value, it is identified that the system is in a load surge state; the original second control component comprises an instruction for increasing the opening degree of the electronic expansion valve by a first preset step within a preset time, and an instruction for increasing the rotating speed of the variable frequency compressor by a second preset step; the control unit is also provided with a weight attenuation rule, after the final driving instruction is generated, with the falling of the pressure change gradient value, the weight of the final second control component in the final driving instruction is gradually reduced by a preset time constant until it is zero.

3. The temperature intelligent regulating system of an industrial water chiller according to claim 1, wherein, The dynamic noise threshold value is not a fixed value, but is determined in real time by the control unit based on the current operating frequency of the variable frequency compressor; the control unit is internally stored with a reference noise spectrum, and the reference noise spectrum defines the pressure fluctuation base value caused by the inherent vibration of the variable frequency compressor at different operating frequencies; the control unit queries the reference noise spectrum in real time to update the dynamic noise threshold value.

4. The temperature intelligent regulating system of an industrial water chiller according to claim 1, wherein, During the generation of the final second control component, the control unit continuously monitors the change trend of the pressure change gradient; when the inflection point feature that the pressure change gradient changes from increasing to decreasing is detected, the control unit identifies the time point of the inflection point feature as an energy balance point; the control unit performs a state locking operation at the energy balance point, sets the current refrigerating capacity determined by the final second control component as a reference refrigerating capacity for subsequent control, and terminates the further dynamic adjustment of the final second control component, and instead adjusts the reference refrigerating capacity based on the first control component.

5. The temperature intelligent regulating system of an industrial water chiller according to claim 2, wherein, The control unit is further configured to calculate a time variation rate of the operating frequency of the variable frequency compressor in real time; when the final second control component drives the variable frequency compressor to accelerate and the time variation rate exceeds a preset acceleration threshold, the control unit generates a third control component for the electronic expansion valve based on the time variation rate; The third control component is configured to drive the opening degree of the electronic expansion valve to increase at a rate synchronized with the acceleration of the variable frequency compressor, and the increasing amplitude is positively correlated with the time variation rate of the operating frequency of the variable frequency compressor, so as to compensate for the decrease in suction pressure caused by the suction effect of the variable frequency compressor before the evaporation rate of the refrigerant in the evaporator increases.

6. The temperature intelligent regulating system of an industrial water chiller according to claim 1, wherein, The system further comprises a second pressure acquisition unit configured to acquire the refrigerant pressure on the condensation side; the control unit internally stores a differential pressure gain correction model, which defines a nonlinear mapping relationship between the feedforward regulation gain and the system operating differential pressure; the control unit calculates the differential pressure between the refrigerant pressure on the condensation side and the refrigerant pressure on the suction side of the variable frequency compressor in real time, and determines a current differential pressure correction coefficient according to the differential pressure gain correction model. When the final second control component is generated, the control unit performs weighted scaling on the amplitude of the final second control component by using the differential pressure correction coefficient.

7. The temperature intelligent regulating system of an industrial water chiller according to claim 1, wherein, The control unit is configured to monitor the opening degree regulation instruction sent to the electronic expansion valve in real time, and calculate an estimated value of the suction pressure variation rate caused by the action of the electronic expansion valve based on a preset valve pressure response model; When the pressure variation gradient value is extracted, the control unit performs signal decoupling operation, subtracts the estimated value from the measured differential value of the refrigerant pressure, and obtains a net pressure gradient value representing the external heat load disturbance; when the absolute value of the net pressure gradient value exceeds a dynamic noise threshold, the control unit generates the original second control component.

8. The temperature intelligent regulating system of an industrial water chiller according to claim 5, wherein, The control unit is further configured to monitor the suction superheat degree on the suction side of the variable frequency compressor in real time, and calculate a time variation rate of the suction superheat degree; during the generation of the third control component for driving the opening degree of the electronic expansion valve to increase, the control unit performs logical verification: when it is detected that the time variation rate of the suction superheat degree is negative and the absolute value exceeds a preset safety threshold, a wet compression risk state is identified, and the control unit immediately shields or reverses the third control component, forces to maintain or reduce the current opening degree of the electronic expansion valve, until the time variation rate of the suction superheat degree returns to a safe range.

9. The temperature intelligent regulating system of an industrial water chiller according to claim 1, wherein, The control unit performs time domain differentiation processing on the refrigerant pressure by using a sliding window algorithm, and the time length of the sliding window is set to be less than the fluid transport delay time required for the cooling fluid in the refrigeration cycle loop to be transported from the heat source to the temperature acquisition unit.

10. The temperature intelligent regulating system of an industrial water chiller according to claim 1, wherein, Gain coefficient defined in the gain correction model with a safety margin satisfies the following relationship: wherein, is a preset warning value, is a low-voltage protection threshold, is a preset attenuation index greater than 1, is used to set the attenuation rate of the gain coefficient when approaching the low-voltage protection threshold.

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