A compressor refrigeration adaptive control method

Abstract

The application provides a compressor refrigeration adaptive control method, wherein the compressor adopts a position starting and stopping mode; at the beginning, a controller determines a temperature set value SV and a compressor starting protection delay Tys, acquires a controlled temperature measurement value PV, initializes a refrigeration starting offset ZLD, a refrigeration return difference ZLHC, a highest point PV max and a lowest point PV min of the controlled temperature measurement value PV and a compressor starting delay Tn; when the PV is higher than the refrigeration starting point ZLon, the compressor starts refrigeration; when the PV falls back to meet the refrigeration return difference ZLHC, the compressor stops refrigeration, and the compressor is set with the delay Tys protection when starting again; the controller automatically calculates a new refrigeration starting offset ZLD and a refrigeration return difference ZLHC according to the highest point PV max and the lowest point PV min of the PV in each fluctuation period and the compressor starting delay condition, which are used for the next period control, and the cycle is repeated. The method can automatically adapt to the change of various working conditions, makes the controlled temperature finally fluctuate slightly around the set value, and significantly improves the control precision.

Description

Technical Field

[0001] This invention relates to the field of compressors, and more specifically, to a compressor refrigeration adaptive control method. Background Technology

[0002] Compressor refrigeration control is widely used in various automated instruments and meters. Compressors are divided into ordinary compressors (also known as fixed-frequency compressors) and variable-frequency compressors. Variable-frequency compressor control is complex, requiring a device similar to a frequency converter for control. It offers high temperature control accuracy but is also expensive, and is generally used in high-end applications. Ordinary compressors have a time delay protection limitation when stopping and restarting. Ordinary compressor control often uses a normally open refrigeration mode or a positional start-stop mode. The normally open refrigeration mode requires the compressor to remain on, using a heating element for heating and balancing, thus avoiding the compressor start-up delay limitation. Heating can use PID control, offering high temperature control accuracy, but it requires a heating element, resulting in high cost and energy consumption. The positional start-stop mode generally has a fixed refrigeration start point and a fixed hysteresis. When the temperature is higher than the start point, the compressor starts refrigeration; when the temperature drops to meet the hysteresis, the compressor stops refrigeration. The positional start-stop mode has a simple control structure, low cost, and is widely used. However, due to the fixed refrigeration start point and fixed hysteresis, and the limitation of the delay time protection when the compressor stops and restarts, different set temperatures or changes in ambient temperature and other operating conditions will cause the actual refrigeration start point after the delay to deviate, resulting in low control accuracy and often deviating from the set temperature.

[0003] In view of this, the present invention is hereby proposed. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an adaptive control method for a common compressor. This method continuously and automatically calculates the refrigeration start-up point and refrigeration hysteresis, makes reasonable use of the compressor start-up delay time, and automatically adapts to changes in various operating conditions, so that the controlled temperature eventually fluctuates slightly around the set value, significantly improving control accuracy.

[0005] This invention provides a compressor refrigeration adaptive control method, wherein the compressor adopts a positional start-stop mode. Initially, the controller determines the temperature setpoint SV and the compressor start-up protection delay Tys. The controller acquires the controlled temperature measurement value PV through a temperature sensor and initializes the refrigeration start offset ZLD, refrigeration hysteresis ZLHC, and the highest point PV of the controlled temperature measurement value. max and the lowest point PV min And the compressor start-up delay Tn; When the controlled temperature measurement value PV is higher than the cooling start point ZLon, the controller starts the compressor to cool; when the controlled temperature measurement value PV falls back to meet the cooling hysteresis ZLHC, the controller stops the compressor to cool, and the compressor is set with a delay Tys protection limit when it stops and restarts. The controller uses the measured value of the controlled temperature PV to determine the highest point of PV within each fluctuation cycle. max and the lowest point PV min The compressor start-up delay status is used to automatically calculate the new cooling start offset ZLD and cooling hysteresis ZLHC for the next cycle control, and so on. Where the compressor start-up delay Tn = Tys: New cooling start offset ZLD = (PV max -PV min ) / 2-(PV max -ZLon); The new cooling hysteresis ZLHC remains unchanged, or the difference decreases or increases based on the controller's temperature resolution.

[0006] As a specific example, initially, the temperature setpoint SV and compressor start protection delay Tys are determined, and the temperature measurement value PV is obtained; the cooling start offset ZLD, cooling hysteresis ZLHC, and the highest temperature fluctuation point PV are initialized. max =SV + Δt, the lowest point of temperature fluctuation PV min =0, compressor start delay Tn=0, and Tn starts timing at the same time; where ZLD≤Δt≤ZLD+2℃.

[0007] As a specific example, when Tn=Tys, the controlled temperature measurement value PV is compared with the cooling start point ZLon, where ZLon=SV+ZLD; If PV≤ZLon, the compressor will not start cooling and will wait for PV to rise. When PV > ZLon, the compressor starts cooling, causing PV to decrease; when cooling starts, if PV > PV max PV max No update if PV≤PV max PV max Update to the PV value when cooling starts.

[0008] As a specific example, when PV drops below the cooling stop point ZLoff, where ZLoff = SV + ZLD - ZLHC, the compressor stops cooling, causing PV to rise again, and the compressor start delay Tn is reset to zero and the timing starts again.

[0009] As a concrete example, when PV decreases and then begins to rise again, the lowest point of temperature fluctuation is reached at PV. min Update to the lowest value of PV, then calculate the new cooling start offset ZLD = (PV). max -PV min ) / 2-(PV max-ZLon) for use in the next control cycle.

[0010] As a specific example, when Tn=Tys, if PV<ZLon, where ZLon=SV+ZLD, the refrigeration hysteresis ZLHC is decreased once by taking the temperature resolution of the controller as the difference, and ZLHC≥0; if PV=ZLon, ZLHC remains unchanged; if PV>ZLon, ZLHC is increased once by taking the temperature resolution of the controller as the difference; the change of ZLHC promotes PV=ZLon when the delay time Tn of the next control cycle is Tys, so as to achieve the minimum PV fluctuation amplitude under the Tys limitation; meanwhile, when PV>ZLon, the compressor is started for refrigeration to promote the decrease of PV.

[0011] As a specific example, when the measured value PV rises and then starts to fall, the highest point of temperature fluctuation PV max is updated to the maximum value of PV; when PV falls to be less than the refrigeration stop point ZLoff, where ZLoff=SV+ZLD-ZLHC, the compressor stops refrigerating to promote PV to rise, and the compressor start delay Tn is cleared and starts timing again.

[0012] As a specific example, the adaptive refrigeration control method for a compressor comprises the following steps: Step 1, the controller determines a temperature set value SV and a compressor start protection delay Tys=180s, and acquires a temperature measured value PV; initializes the refrigeration start offset ZLD=0.5°C, refrigeration hysteresis ZLHC=0.1°C, the highest point of temperature fluctuation PV max =SV+0.8°C, the lowest point of temperature fluctuation PV min =0, and compressor start delay Tn=0, meanwhile Tn starts timing; Step 2, when the compressor start delay Tn is equal to the compressor start protection delay Tys, the temperature measured value PV is compared with the refrigeration start point ZLon, wherein, ZLon=SV+ZLD; if PV≤ZLon, the compressor does not start refrigeration, and waits for PV to rise; when PV>ZLon, the compressor starts refrigeration to promote PV to decrease; when refrigeration is started, if PV>PV max , PV max is not updated, if PV≤PV max , PV max is updated to the value of PV when refrigeration is started; Step 3: when PV drops below the refrigeration stop point ZLoff, where ZLoff=SV+ZLD-ZLHC, the compressor stops refrigeration to prompt PV to rise, and the compressor start delay Tn is cleared and starts timing again; Step 4: when PV starts to rise again after dropping, the lowest point of temperature fluctuation PV min is updated to the minimum value of PV, then a new refrigeration start offset ZLD is calculated as ZLD=(PV max -PV min ) / 2-(PV max -ZLon) for use in the next control cycle; Step 5: when the compressor start delay Tn equals the compressor start protection delay Tys, if PV<ZLon, where ZLon=SV+ZLD, the refrigeration hysteresis ZLHC is decremented once with 0.1 as the difference, and ZLHC≥0; if PV=ZLon, ZLHC remains unchanged; if PV>ZLon, ZLHC is incremented once with 0.1 as the difference; the change of ZLHC promotes PV=ZLon when the delay time Tn=Tys in the next control cycle, so as to achieve the minimum PV fluctuation amplitude under the constraint of Tys; meanwhile, when PV>ZLon, the compressor is started for refrigeration to prompt PV to drop; Step 6: when the measured value PV starts to drop again after rising, the highest point of temperature fluctuation PV max is updated to the maximum value of PV; when PV drops below the refrigeration stop point ZLoff, where ZLoff=SV+ZLD-ZLHC, the compressor stops refrigeration to prompt PV to rise, and the compressor start delay Tn is cleared and starts timing again; Step 7: repeating steps 4-6 in this way, the control cycle cycles continuously, PV fluctuation converges gradually, and PV finally performs constant-amplitude fluctuation near the set value SV with the minimum fluctuation amplitude.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. In the adaptive control method for compressor refrigeration of the present invention, the controller automatically calculates a new refrigeration start offset and refrigeration hysteresis of the compressor according to the highest point and the lowest point in each fluctuation cycle of the measured temperature value and the compressor start delay condition, which are used for control of the next cycle. Through such circulation, the measured value of the controlled temperature finally fluctuates at a constant amplitude near the set value, and the fluctuation amplitude is minimized under the constraint of the compressor start delay.

[0014] 2. Regardless of the initial state, changes in the set temperature, or changes in the ambient temperature, the compressor refrigeration adaptive control method of the present invention can automatically adjust the refrigeration start offset ZLD and the refrigeration hysteresis ZLHC, control PV to eventually fluctuate at a constant amplitude near the set value SV, and minimize the fluctuation amplitude under the start delay Tys constraint.

[0015] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0016] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of the present invention and do not constitute a limitation on the technical solutions of the present invention.

[0017] Figure 1 This is a schematic flowchart of the compressor refrigeration adaptive control method of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] Example 1 This invention provides a compressor refrigeration adaptive control method, such as... Figure 1 The diagram shows one flow of this control method. The compressor is a non-inverter compressor.

[0020] The controller controls the compressor using a positional start-stop method. The controller obtains the controlled temperature measurement value PV through the temperature sensor. When the controlled temperature measurement value PV is higher than the set start point, the compressor starts cooling. When the controlled temperature measurement value PV falls back to meet the hysteresis, the compressor stops cooling. There is a time delay protection limit when the compressor stops and restarts.

[0021] The temperature setpoint SV and compressor start-up protection delay Tys are set via the controller. SV is typically set so that cooling is only required when the temperature is lower than the ambient temperature. Tys is the limit for compressor restart time, usually set to 180 seconds. Cooling start offset ZLD, cooling hysteresis ZLHC, and the highest temperature fluctuation point PV are also considered. maxand PV at the lowest point of temperature fluctuation min and the values of compressor start delay Tn are initialized when the controller is powered on, wherein ZLD=0.5, ZLHC=0.1, PV max =SV+0.8, PV min =0, Tn=0, and Tn starts timing immediately after power-on.

[0022] When PV>SV+ZLD and Tn=Tys, the controller starts the compressor for refrigeration to promote the decrease of temperature PV; when PV<SV+ZLD-ZLHC, the controller stops the compressor for refrigeration to promote the rise of temperature PV, and Tn is reset to zero and restarts timing. This repeats, and a new PV max and PV min can be obtained in each PV fluctuation cycle.

[0023] The PV fluctuation cycle herein refers to the process from the start of refrigeration of the compressor to the stop of refrigeration and the start of temperature rise.

[0024] If the system has good control performance when the ambient temperature is 20°C, that is, PV oscillates with equal amplitude near SV, that is PV max -SV=SV-PV min , and at the same time the delay time is just appropriate, that is when Tn=Tys, PV=SV+ZLD, and in this state, under the limiting condition of Tys, the PV fluctuation amplitude is also the smallest. When the ambient temperature increases, it is equivalent to the thermal insulation performance of the system deteriorating, the PV min generated by the fixed ZLHC will become higher, and PV will also rise faster, so that when Tn=Tys, PV>SV+ZLD, which results in PV oscillating above the vicinity of SV and the fluctuation amplitude also increases. The improvement measure is to increase ZLHC and adjust ZLD. When the ambient temperature decreases, it is equivalent to the thermal insulation performance of the system improving, the PV min generated by the fixed ZLHC will become lower, and PV will also rise slower, so that when Tn=Tys, PV<SV+ZLD, which results in PV oscillating below the vicinity of SV and the fluctuation amplitude also increases. The improvement measure is to decrease ZLHC and adjust ZLD. If the ambient temperature remains unchanged and the set temperature SV of the system is changed, it is also equivalent to a change in the thermal insulation performance of the system, and the above phenomenon will also occur.

[0025] In the adaptive control method for compressor refrigeration of the present invention, a new PV at the highest point of temperature fluctuation PV max and PV at the lowest point of temperature fluctuation min are obtained in each fluctuation cycle of the temperature measurement value PV, and a new refrigeration start offset ZLD is calculated as ZLD=(PV max -PV min ) / 2-(PV max-SV-ZLD) is applied to the next cycle to prompt PV to oscillate with constant amplitude near the set value SV.

[0026] Meanwhile, when Tn=Tys, a new refrigeration hysteresis ZLHC is adjusted according to the magnitude relationship between PV and SV+ZLD. If PV>SV+ZLD, then ZLHC=ZLHC+0.1; if PV<SV+ZLD, then ZLHC=ZLHC-0.1; otherwise, ZLHC remains unchanged. The new ZLHC is applied to the next cycle, to prompt that when the delay time is exactly Tn=Tys, PV=SV+ZLD. Finally, the fluctuation amplitude of PV is minimized under the restriction of Tys, and the system can automatically adapt to obtain optimal control when the working condition changes.

[0027] As an operation example, the adaptive control method for compressor refrigeration specifically comprises the following steps: Step 1: a controller determines a temperature set value SV (lower than the ambient temperature) and a compressor start protection delay Tys=180s, and acquires a measured value PV of the controlled temperature through a temperature sensor; initialize a refrigeration start offset ZLD=0.5°C, a refrigeration hysteresis ZLHC=0.1°C, the highest point of temperature fluctuation PV max =SV+0.8°C, the lowest point of temperature fluctuation PV min =0, and a compressor start delay Tn=0, and Tn starts timing at the same time; Step 2: when the compressor start delay Tn is equal to the compressor start protection delay Tys, the measured temperature value PV is compared with a refrigeration start point ZLon, wherein ZLon=SV+ZLD; if PV≤ZLon, the compressor does not start refrigeration, and waits for PV to rise; when PV>ZLon, the compressor starts refrigeration to prompt PV to decrease; when refrigeration starts, if PV>PV max , PV max is not updated; if PV≤PV max , PV max is updated to the value of PV when refrigeration starts; Step 3: when PV drops below the refrigeration stop point ZLoff, wherein ZLoff=SV+ZLD-ZLHC, the compressor stops refrigeration to prompt PV to rise again, and the compressor start delay Tn is cleared and starts timing again; Step 4: when PV starts to rise again after dropping, the lowest point of temperature fluctuation PV min is updated to the minimum value of PV, then a new refrigeration start offset ZLD=(PV max -PV min ) / 2-(PV max -ZLon) is calculated for the next control cycle; Step 5: when the compressor start delay Tn=compressor start protection delay Tys, if PV<ZLon, where ZLon=SV+ZLD, the cooling dead zone ZLHC is decremented once, that is ZLHC=ZLHC-0.1 (the minimum limit of ZLHC is 0); If PV=ZLon, ZLHC remains unchanged; If PV>ZLon, ZLHC is incremented once, that is ZLHC=ZLHC+0.1; the change of ZLHC promotes PV=ZLon when the delay time Tn=Tys in the next control cycle, so as to achieve the minimum fluctuation amplitude of PV under the constraint of Tys; meanwhile, when PV>ZLon, the compressor is started for cooling, which promotes the decrease of PV; Step 6: when the measured value PV rises and then starts to decrease, the highest point of temperature fluctuation PV max is updated to the maximum value of PV; when PV decreases to be less than the cooling stop point ZLoff, where ZLoff=SV+ZLD-ZLHC, the compressor stops cooling to promote PV to rise, and the compressor start delay Tn is reset to zero and starts timing again; Step 7: repeat steps 4 to 6 in this way, the control cycle circulates continuously, PV fluctuation gradually converges, and PV finally fluctuates with constant amplitude near the set value SV with the minimum fluctuation amplitude.

[0028] Although the embodiments disclosed by the present invention are as above, the described content is only the embodiments adopted for facilitating understanding of the present invention, and is not intended to limit the present invention. Any person skilled in the art to which the present invention pertains can make any modifications and changes in the form and details of implementation without departing from the spirit and scope disclosed by the present invention, but the patent protection scope of the present invention shall still be determined by the scope defined in the appended claims.

Claims

1. A compressor refrigeration adaptive control method, characterized in that, The compressor uses a positional start / stop method. Initially, the controller determines the temperature setpoint SV and the compressor start protection delay Tys. The controller acquires the controlled temperature measurement value PV through the temperature sensor and initializes the cooling start offset ZLD, cooling hysteresis ZLHC, and the highest point PV of the controlled temperature measurement. max and the lowest point PV min And the compressor start-up delay Tn; When the measured controlled temperature PV is higher than the refrigeration startup point ZLon, the controller starts the compressor for refrigeration; When the measured controlled temperature PV drops and meets the refrigeration hysteresis ZLHC, the controller stops the compressor from refrigeration, and the delay Tys protection restriction is set when the compressor is restarted; The controller uses the measured value of the controlled temperature PV to determine the highest point of PV within each fluctuation cycle. max and the lowest point PV min The compressor start-up delay status is used to automatically calculate the new cooling start offset ZLD and cooling hysteresis ZLHC for the next cycle control, and so on. Wherein, when the compressor startup delay Tn=Tys: New cooling start offset ZLD = (PV max -PV min ) / 2-(PV max -ZLon); The new refrigeration hysteresis ZLHC remains unchanged, or decreases or increases by taking the temperature resolution of the controller as the difference; When Tn=Tys, the measured controlled temperature PV is compared with the refrigeration startup point ZLon, wherein ZLon=SV+ZLD; If PV≤ZLon, the compressor will not start refrigeration and wait for PV to rise; When PV > ZLon, the compressor starts cooling, causing PV to decrease; when cooling starts, if PV > PV max PV max No update if PV≤PV max PV max Update to the PV value when cooling starts; When PV drops below the refrigeration stop point ZLoff, wherein ZLoff=SV+ZLD-ZLHC, the compressor stops refrigeration to promote PV to rise, and the compressor startup delay Tn is cleared and starts timing again; When PV decreases and then begins to rise again, the lowest point of temperature fluctuation is reached at PV. min Update to the lowest value of PV, then calculate the new cooling start offset ZLD = (PV). max -PV min ) / 2-(PV max -ZLon) is used for the next control cycle; When Tn=Tys, if PV<ZLon, wherein ZLon=SV+ZLD, the refrigeration hysteresis ZLHC is decreased once by taking the temperature resolution of the controller as the difference, with the restriction that ZLHC≥0; If PV=ZLon, ZLHC remains unchanged; If PV>ZLon, ZLHC is increased once by taking the temperature resolution of the controller as the difference; the change of ZLHC promotes PV to be equal to ZLon when the delay time Tn=Tys in the next control cycle, so as to achieve the minimum fluctuation amplitude of PV under the restriction of Tys; meanwhile, when PV>ZLon, the compressor is started for refrigeration to promote PV to drop.

2. The compressor refrigeration adaptive control method according to claim 1, characterized in that, Initially, the temperature setpoint SV and compressor start-up protection delay Tys are determined, and the temperature measurement value PV is acquired; the cooling start offset ZLD, cooling hysteresis ZLHC, and the highest temperature fluctuation point PV are initialized. max =SV + Δt, the lowest point of temperature fluctuation PV min =0, compressor start delay Tn=0, and Tn starts timing at the same time; where ZLD≤Δt≤ZLD+2℃.

3. The adaptive control method for compressor refrigeration according to claim 1, characterized in It lies in, When the measured value PV rises and then begins to fall again, the temperature fluctuation reaches its highest point at PV. max Update to the highest value of PV; when PV drops below the cooling stop point ZLoff, where ZLoff=SV+ZLD-ZLHC, the compressor stops cooling, causing PV to rise again, and the compressor start delay Tn is reset to zero and starts timing again.

4. The compressor refrigeration adaptive control method according to claim 1, characterized in that, it comprises the following steps: Step 1: The controller determines the temperature setpoint SV and the compressor start protection delay Tys = 180 seconds, and acquires the temperature measurement value PV; initializes the cooling start offset ZLD = 0.5℃, cooling hysteresis ZLHC = 0.1℃, and the highest temperature fluctuation point PV. max =SV+0.8℃, the lowest point of temperature fluctuation PV min =0, compressor start delay Tn=0, and Tn starts timing at the same time; Step 2, when the compressor startup delay Tn is equal to the compressor startup protection delay Tys, the measured temperature PV is compared with the refrigeration startup point ZLon, wherein ZLon=SV+ZLD; If PV≤ZLon, the compressor will not start refrigeration and wait for PV to rise; When PV > ZLon, the compressor starts cooling, causing PV to decrease; when cooling starts, if PV > PV max PV max No update if PV≤PV max PV max Update to the PV value when cooling starts; Step 3, when PV drops below the refrigeration stop point ZLoff, wherein ZLoff=SV+ZLD-ZLHC, the compressor stops refrigeration to promote PV to rise, and the compressor startup delay Tn is cleared and starts timing again; Step 4: When PV drops and then starts to rise again, the temperature fluctuation reaches its lowest point (PV). min Update to the lowest value of PV, then calculate the new cooling start offset ZLD = (PV). max -PV min ) / 2-(PV max -ZLon) is used for the next control cycle; Step 5, when the compressor startup delay Tn is equal to the compressor startup protection delay Tys, if PV<ZLon, wherein ZLon=SV+ZLD, the refrigeration hysteresis ZLHC is decreased once by taking 0.1 as the difference, with ZLHC≥0; If PV=ZLon, ZLHC remains unchanged; If PV>ZLon, ZLHC is increased once by taking 0.1 as the difference; the change of ZLHC promotes PV to be equal to ZLon when the delay time Tn=Tys in the next control cycle, so as to achieve the minimum fluctuation amplitude of PV under the restriction of Tys; meanwhile, when PV>ZLon, the compressor is started for refrigeration to promote PV to drop; Step 6: When the measured value PV rises and then begins to fall again, the temperature fluctuation reaches its highest point at PV. max Update to the highest value of PV; when PV drops below the cooling stop point ZLoff, where ZLoff=SV+ZLD-ZLHC, the compressor stops cooling, causing PV to rise again, and the compressor start delay Tn is reset to zero and starts timing again. Step 7, repeating steps 4 to 6 in this way, the control cycle circulates continuously, the fluctuation of PV converges gradually, and PV finally fluctuates with constant amplitude near the set value SV with the minimum fluctuation amplitude.

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