Control method for achieving intelligent defrosting and reducing energy consumption through PID control for refrigerator

Abstract

According to the control method for achieving intelligent defrosting and reducing energy consumption for the refrigerator through PID control, firstly, a needed defrosting reference temperature is set, a refrigerator computer board collects a defrosting temperature sensor in real time, and then the current instantaneous n temperature is subjected to analog-to-digital conversion (Pn = And); the system accumulates the refrigeration time of the compressor, judges the accumulative time, defrosts when the set accumulative time is reached, calculates the change rate of defrosting temperature rise along with the time, judges the change rate of the temperature rise, and enters a control stage before adjustment when the change rate of the temperature rise is greater than theta k, and a heating pipe is electrified for heating; when the temperature rise change rate is smaller than theta k, entering a regulation stage, and performing SSR relay conduction pulse frequency F regulation by the system according to PID regulation preset control; and the PID control system judges the difference value between the current temperature collection Pn and the initial set temperature Sv in real time, and when the difference value is smaller than or equal to 1 DEG C and can reach Tim0, defrosting is stopped, the accumulated refrigeration time T of the compressor is reset, the refrigeration time of the compressor is accumulated again, and next defrosting is judged.

Description

Technical field:

[0001] The invention relates to a control method for realizing intelligent frost and reducing energy consumption by using PID control in a refrigerator, and belongs to the technical field of refrigerators and freezers. Background technology:

[0002] At present, the refrigeration method of refrigerators is that after the hot air is cooled on the evaporator in the freezer, the moisture in the air frosts on the surface of the evaporator. The cold air is transmitted to each compartment to achieve the purpose of refrigeration. However, after a long period of refrigeration, frost will accumulate on the surface of the evaporator, and the refrigeration effect will gradually deteriorate. At this time, defrosting must be performed to restore the refrigeration effect.

[0003] The current defrosting method is to use a computer board to control the heating tube to power on and heat it through a relay switch to perform defrosting. A temperature sensor is placed at a certain position on the upper side of the evaporator. When the temperature sensor reaches a specific temperature T, such as 8°C, it is indirectly inferred that the defrosting of the evaporator surface is completed. The computer board controls the relay to turn off, the heating tube is powered off, and then the defrosting heating tube stops heating.

[0004] The existing defrost control is relatively simple and crude, and is an empirical manifestation of engineering applications. Through a temperature sensor reaching an empirical temperature value above 0 degrees, it is indirectly inferred that the defrosting of the evaporator surface is completed, and then the defrosting heating is terminated. In this process, it is ignored that the heating of the heating tube and the heat transfer have a certain lag.

[0005] Therefore, it is necessary to improve the existing technology to solve the shortcomings of the existing technology. Summary of the invention:

[0006] The present invention aims to solve the problems existing in the above-mentioned prior art and provides a control method for refrigerators to achieve intelligent defrosting and reduce energy consumption by using PID control. The method uses temperature feedback and continuously variable power to perform intelligent adaptive defrosting, so that the defrosting heating power can be adjusted in real time according to the evaporator temperature, so that the heating heat can better match the cold amount of frosting on the evaporator surface, thereby achieving the purpose of fully utilizing heat and reducing energy consumption.

[0007] The technical solution adopted by the present invention is: a control method for realizing intelligent frost and reducing energy consumption of refrigerators by using PID control, and the specific steps are as follows:

[0008] Step 1: According to different design models, different freezing volumes, and different evaporator frost amounts, set a required defrosting reference temperature Sv = T0°C;

[0009] Step 2: The refrigerator computer board collects the analog value of the defrost temperature sensor in real time, and then converts the current instantaneous temperature n into analog-to-digital value Pn=And, where Pn is the current instantaneous collected defrost sensor temperature value, that is, the analog-to-digital conversion value;

[0010] Step 3: The compressor starts to refrigerate under the refrigeration requirement. The system accumulates the compressor refrigeration time T and judges the accumulated time T. When the set accumulated time THS is reached, defrosting is performed. The temperature acquisition difference of the unit acquisition cycle ΔP=Pn-Pn-1, and the rate of change of defrost temperature rise over time is calculated θ=ΔP / Δt, where T: the accumulated time of the compressor starting to refrigerate, THS: the accumulated time value of the compressor starting to trigger defrost, θ: the rate of change of defrost sensor temperature, ΔP: ΔP=Pn-Pn-1, the difference between the current instantaneous acquisition temperature and the previous acquisition instantaneous temperature, Δt=tn-tn-1: the acquisition time interval;

[0011] Step 4: Determine the temperature rise change rate θ. When the temperature rise change rate is greater than θk, the system output controls the solid-state relay SSR to have a conduction pulse duty cycle of 1, that is, fully conductive, the defrost heating tube Heat = 1, and the heating tube is powered on for heating;

[0012] Step 5: Accumulate the power-on time of the heating tube TimON, take 60 seconds as a heating square wave cycle, 60*F is the power-on time of the heating tube in one cycle, that is, high level, through the TimON time accumulation, when it reaches 60*F, the heating tube is turned off, that is, TimON=0, the defrosting heating tube Heat=0, and the heating is stopped;

[0013] Step 6: Accumulate the heating stop time TimOFF, when TimOFF>60*(1-F), that is, the heating tube power-off cycle in a heating tube square wave cycle is low level;

[0014] Step 7: After a square wave cycle of the heating tube is completed, the high level power is repeatedly turned on for heating, and the low level power is turned off for no heating;

[0015] Step 8: When the heating tube continues to heat, when the temperature rise rate θ is less than θk, the system will adjust the SSR relay conduction pulse frequency F according to the PID adjustment preset control;

[0016] Step 9: Set the parameters Kc, Ts, Ti, Td, and Mcon in advance. The system calculates the system adjustment value Mn at the current moment n according to the preset formula Mn=Mp+Mi+Md+Mcon, and then accumulates the effective time of the adjustment value at each moment. If Mn does not change within 30 seconds, F=Mn, that is, the system adjustment output F is updated every 30 seconds;

[0017] Mp=Kc*(SV-PVn)

[0018] Mi=Ki*(SV-PVn)+MX

[0019] Md=KD*(PVn-1-PVn)

[0020] Mn=Kc*(SV-PVn)+(Ki*(SV-PVn)+MX)+KD*(PVn-1-PVn)+Mcon

[0021] Mn is the calculated output value of the PID loop at the nth sampling moment;

[0022] SV is the set value of the PID loop;

[0023] PVn is the process variable value at the nth sampling moment;

[0024] PVn-1 is the process variable value at the n-1th sampling time;

[0025] MX is the value of the previous term of the integral;

[0026] Mcon is the static output value of the PID loop;

[0027] Kc is the proportional gain of the PID loop;

[0028] KI is the proportional constant of the integral term KI = Kc*Ts / Ti;

[0029] Ts is the sampling time interval during discretization;

[0030] Ti is the integral time parameter;

[0031] KD is the proportional constant of the differential term KD = Kc*Td / Ts;

[0032] Ts is the sampling time interval during discretization;

[0033] Td is the differential time parameter;

[0034] Step 10: The PID control system determines the difference between the current temperature acquisition Pn and the initial setting quality Sv in real time, e=Sv-Pn. When the difference e is less than or equal to 1℃ and the time can reach Tim0, the defrost is exited and the compressor accumulated refrigeration time T is reset to zero. If the system defrost conditions are not met, the defrost is exited and the compressor refrigeration time is accumulated again to determine the next defrost.

[0035] Furthermore, in step 4, the system output controls the solid-state relay SSR conduction pulse to control the heating power of the heating tube, as follows:

[0036] The power output adopts the pulse width modulation method, using the solid-state relay SRR to output continuously variable pulses, thereby forming an output voltage Uout with adjustable pulse width, which is given to the defrost heater;

[0037] When heating output is required, the solid-state relay SSR is triggered and the power supply voltage U AN Add to both ends of the heating tube through the output end of the SSR;

[0038] When the solid-state relay SSR has no trigger signal, the SSR is turned off, and the average voltage across the heating tube is Uout = (t / T) * U AN =K*U AN , where K = t / T, is the ratio of the SSR triggering conduction in a period T, called the load voltage coefficient or duty cycle, and the change rate of K is between 0 and 1;

[0039] It is inconvenient to set the cycle T fixedly. Adjust t. When t changes within the range of 0-T, the voltage of the heating tube is between 0-U AN The heating power changes between , the heating tube power P = Uout2 / R, so that the heating power follows the variable.

[0040] Furthermore, step seven is the front end of the adjustment, the SSR and the heating tube are in a full-load output state, that is, the SSR conduction pulse duty cycle is F=1, and when the temperature rise rate exceeds the control parameter "acceleration rate", the SSR turns off the output.

[0041] Furthermore, step eight is the adjustment stage. In this stage, the PID regulator adjusts the output and calculates the duty cycle (0-100%) according to the deviation value to ensure that the deviation EV (EV=SV-PV) approaches 0. When the time when the deviation EV (EV=SV-PV) is less than 1°C reaches T0, the SSR output is turned off and the heating of the heating tube stops.

[0042] Furthermore, in step nine, the calculation function of the system adjustment amount is: Mn=Mp+Mi+Md+Mcon

[0043] M(t)=Kc*e(t)+Kc∫0e(t)dt+Kc*e(t) / dt+Mcon

[0044] M(t) is the output of the PID loop, which is a function of time; Kc is the proportional gain of the PID loop; e is the deviation EV of the PID loop (EV=SV-PV); and Mcon is the static output value of the PID loop.

[0045] Furthermore, in step ten, according to the actual refrigerator, appropriate coefficient parameters and constant parameters Kc, Ts, Ti, Td, and Mcon are set, and e is set to maintain 1°C for a time at T0, defrosting is deemed to be completed, and the heating tube is powered off.

[0046] The present invention has the following beneficial effects: The present invention uses PID control to realize intelligent defrosting and energy consumption reduction control method for refrigerators. Through the principle of PID control system, a control linkage is established between the heating duty ratio of the heating tube (representing the heating power) and the defrosting temperature deviation EV (EV=SV-PV) on the surface of the evaporator. The defrosting heating heat is effectively controlled to change in real time with the monitoring temperature PV. The heat utilization rate is effectively improved, and the double waste of overheating heat is reduced. Description of the drawings:

[0047] Figure 1 This is a schematic diagram of a control method for realizing intelligent frost and reducing energy consumption by using PID control in a refrigerator of the present invention. Specific implementation method:

[0048] The present invention will be further described below in conjunction with the accompanying drawings.

[0049] The present invention discloses a control method for realizing intelligent frost control to reduce energy consumption of refrigerators by using PID control, and the specific steps are as follows:

[0050] Step 1: According to different design models, different freezing volumes, and different evaporator frost amounts, set a required defrosting reference temperature Sv=T0℃.

[0051] Step 2: The refrigerator computer board collects the analog value of the defrost temperature sensor in real time, and then converts the current instantaneous temperature n into an analog-to-digital value Pn=And.

[0052] Step 3: The compressor starts to refrigerate under the refrigeration requirement. The system accumulates the compressor refrigeration time T and judges the accumulated time T. When the set accumulated time THS is reached, defrosting is performed. The temperature collection difference per unit collection cycle ΔP=Pn-Pn-1 is used to calculate the rate of change of defrosting temperature rise over time, θ=ΔP / Δt.

[0053] Step 4: Determine the temperature rise change rate θ. When the temperature rise change rate is greater than θk, the system output controls the solid-state relay SSR to have a conduction pulse duty cycle of 1, that is, fully conductive, the defrost heating tube Heat = 1, and the heating tube is energized for heating.

[0054] Step 5: Accumulate the power-on time of the heating tube TimON, with 60 seconds as a heating square wave cycle, 60*F is the power-on time of the heating tube in one cycle (high level), and when the TimON time is accumulated and 60*F is reached, the heating tube is turned off, that is, TimON=0, the defrost heating tube Heat=0, and the heating is stopped.

[0055] Step 6: Accumulate the heating stop time TimOFF. When TimOFF>60*(1-F), it is the heating tube power-off cycle (low level) in one heating tube square wave cycle.

[0056] Step 7: After a square wave cycle of the heating tube is completed, the high level power is turned on for heating, and the low level power is turned off for no heating.

[0057] Step 8: When the heating tube continues to heat, when the temperature rise rate θ is less than θk, the system will adjust the SSR relay conduction pulse frequency F according to the PID adjustment preset control.

[0058] Step 9: Set the parameters Kc, Ts, Ti, Td, and Mcon in advance. The system calculates the system adjustment amount Mn=Mp+Mi+Md+Mcon at the current moment n according to the preset formula, and then accumulates the effective time of the adjustment amount at each moment. If Mn does not change within 30 seconds, F=Mn, that is, the system adjustment output F is updated every 30 seconds;

[0059] Step 10: The PID control system will judge the difference between the current temperature acquisition Pn and the initial setting quality Sv in real time, e=Sv-Pn. When the difference e is less than or equal to 1℃ and the time can reach Tim0, the defrost will be exited and the accumulated refrigeration time T of the compressor will be reset. If the system defrost conditions are not met, the defrost will be exited and the compressor refrigeration time will be accumulated again to determine the next defrost.

[0060] In step 4, the system output controls the solid-state relay SSR to conduct pulses and control the heating power of the heating tube. The details are as follows: the power output adopts the pulse width modulation method, and uses the solid-state relay SRR to output continuously variable pulses, thereby forming an output voltage Uout with adjustable pulse width, which is given to the defrost heater. When heating output is required, the solid-state relay SSR is triggered, and the power supply voltage U AN The voltage is added to both ends of the heating tube through the output end of the SSR. When there is no trigger signal of the solid-state relay SSR, the SSR is turned off. Therefore, the average voltage at both ends of the heating tube is Uout = (t / T) * U AN =K*U AN , where K = t / T, is the ratio of SSR triggering conduction in a period T (usually 60s as a pulse period), called load voltage coefficient or duty cycle, and the change rate of K is between 0 and 1. Generally, it is inconvenient to fix the period T, and adjust t. When t changes in the range of 0-T, the voltage of the heating tube is between 0-U AN The heating tube power P = Uout2 / R, so that the heating power can be followed and changed. That is, in step 4, when the temperature rise rate is greater than θk, the SSR pulse duty cycle is 1, and the heating tube is controlled to achieve full power heating, and the heating speed is faster.

[0061] The temperature control system is a system with large inertia. When the power is turned on for heating, the temperature rises very quickly. When the heating is turned off, the temperature of the temperature zone still rises to a certain extent. In addition, the temperature detection of the thermocouple also has a certain lag effect compared with the actual temperature of the temperature zone. That is to say, when the evaporator surface is frost-prone and needs to be heated, the temperature of the temperature sensor cannot be seen to rise immediately after the heating tube is powered on. Similarly, when the temperature sensor reaches the temperature and the heater is powered off, the temperature of the temperature zone still rises to a certain extent. Therefore, if the output is turned off only when the temperature detection value PV reaches the set value, it may exceed the set value for a long time due to the lag effect of the temperature, resulting in heat waste, and forming a burden for the next refrigeration, resulting in refrigeration waste; if the output is turned off before the temperature detection value PV reaches the set value, it may be difficult to reach the set value due to early shutdown, and the frost cannot be completely melted. In order to reasonably deal with the contradiction between the system response speed (i.e., heating speed) and the system stability, the temperature control is divided into two stages.

[0062] The above step seven is the pre-regulation stage. At this stage, because the temperature of the temperature zone is still far from the set value, in order to speed up the heating speed, the SSR and the heating tube are in full load output state, that is, the SSR conduction pulse duty cycle is F=1. Only when the temperature rise rate exceeds the control parameter "acceleration rate" will the SSR turn off the output. "Acceleration rate" describes the temperature span per unit time, reflecting the speed of temperature rise and fall. Using "acceleration rate" to limit the temperature rise too fast is to reduce the inertia of the temperature entering the PID adjustment zone and avoid excessive overshoot when the temperature set value SV is reached for the first time.

[0063] The above step eight is the adjustment stage. In this stage, the PID regulator adjusts the output and calculates the duty cycle (0-100%) according to the deviation value to ensure that the deviation EV (EV=SV-PV) approaches 0. When the time when the deviation EV (EV=SV-PV) is less than 1°C reaches T0, the SSR output is turned off and the heating of the heating tube stops.

[0064] In the above step nine, the calculation function of the system adjustment amount is: Mn=Mp+Mi+Md+Mcon

[0065] M(t)=Kc*e(t)+Kc∫0e(t)dt+Kc*e(t) / dt+Mcon

[0066] M(t) is the output of the PID loop, which is a function of time; Kc is the proportional gain of the PID loop; e is the deviation EV of the PID loop (EV=SV-PV); and Mcon is the static output value of the PID loop.

[0067] In order for a digital computer to process this formula, the continuous formula must be discretized into a periodic sampling deviation formula before it can be used to calculate the output value. The formula processed by the digital computer is as follows:

[0068] Mn=Kc*(SV-PVn)+(Ki*(SV-PVn)+MX)+KD*(PVn-1-PVn)+Mcon

[0069] Mn is the calculated output value of the PID loop at the nth sampling moment;

[0070] SV is the set value of the PID loop;

[0071] PVn is the process variable value at the nth sampling moment;

[0072] PVn-1 is the process variable value at the n-1th sampling time;

[0073] MX is the value of the previous term of the integral;

[0074] Mcon is the static output value of the PID loop;

[0075] Kc is the proportional gain of the PID loop;

[0076] KI is the proportional constant of the integral term KI = Kc*Ts / Ti;

[0077] Ts is the sampling time interval during discretization;

[0078] Ti is the integral time parameter;

[0079] KD is the proportional constant of the differential term KD = Kc*Td / Ts;

[0080] Ts is the sampling time interval during discretization;

[0081] Td is the differential time parameter;

[0082] According to the real-time Mn, that is, the duty cycle (0-100%), the average voltage across the heating tube is Uout = (t / T) * U AN =K*U AN ;

[0083] The heating tube power P=Uout2 / R, and the power changes with the system adjustment.

[0084] In the above step 10, according to the actual refrigerator, set the appropriate coefficient parameters and constant parameters Kc, Ts, Ti, Td, Mcon, and after multiple adjustments, the e deviation tends to be small. In order to meet the time requirements of actual applications, e can be set to maintain 1°C for T0, and the defrosting is considered to be completed, and the heating tube is powered off.

[0085] The present invention uses PID control to realize intelligent defrosting and energy consumption reduction control method for refrigerators. Through the principle of PID control system, a control linkage is established between the heating duty ratio (representing heating power) of the heating tube and the defrosting temperature deviation EV (EV=SV-PV) on the surface of the evaporator. The defrosting heating heat is effectively controlled to change in real time with the monitoring temperature PV. The heat utilization rate is effectively improved, and the double waste of overheating heat is reduced.

[0086] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements without departing from the principle of the present invention, and these improvements should also be regarded as within the protection scope of the present invention.

Claims

1. A control method for realizing intelligent frost control and reducing energy consumption of refrigerators by using PID control, characterized in that: The specific steps are as follows: Step 1: According to different design models, different freezing volumes, and different evaporator frost amounts, set a required defrosting reference temperature Sv = T0°C; Step 2: The refrigerator computer board collects the analog value of the defrost temperature sensor in real time, and then converts the current instantaneous temperature n into analog-to-digital value Pn=And, where Pn is the current instantaneous collected defrost sensor temperature value, that is, the analog-to-digital conversion value; Step 3: The compressor starts to refrigerate under the refrigeration requirement. The system accumulates the compressor refrigeration time T and judges the accumulated time T. When the set accumulated time THS is reached, defrosting is performed. The temperature acquisition difference of the unit acquisition cycle ΔP=Pn-Pn-1, and the rate of change of defrost temperature rise over time is calculated θ=ΔP / Δt, where T: the accumulated time of the compressor starting to refrigerate, THS: the accumulated time value of the compressor starting to trigger defrost, θ: the rate of change of defrost sensor temperature, ΔP: ΔP=Pn-Pn-1, the difference between the current instantaneous acquisition temperature and the previous acquisition instantaneous temperature, Δt=tn-tn-1: the acquisition time interval; Step 4: Determine the temperature rise change rate θ. When the temperature rise change rate is greater than θk, the system output controls the solid-state relay SSR to have a conduction pulse duty cycle of 1, that is, fully conductive, the defrost heating tube Heat = 1, and the heating tube is powered on for heating; Step 5: Accumulate the power-on time of the heating tube TimON, take 60 seconds as a heating square wave cycle, 60*F is the power-on time of the heating tube in one cycle, that is, high level, through the TimON time accumulation, when it reaches 60*F, the heating tube is turned off, that is, TimON=0, the defrosting heating tube Heat=0, and the heating is stopped; Step 6: Accumulate the stop heating time TimOFF, when TimOFF>60*(1-F), that is, the heating tube power-off cycle in a heating tube square wave cycle is low level; Step 7: After a square wave cycle of the heating tube is completed, the high level power is repeatedly turned on for heating, and the low level power is turned off for no heating; Step 8: When the heating tube continues to heat, when the temperature rise rate θ is less than θk, the system will adjust the SSR relay conduction pulse frequency F according to the PID adjustment preset control; Step 9: Set the parameters Kc, Ts, Ti, Td, and Mcon in advance. The system calculates the system adjustment value Mn at the current moment n according to the preset formula Mn=Mp+Mi+Md+Mcon, and then accumulates the effective time of the adjustment value at each moment. If Mn does not change within 30 seconds, F=Mn, that is, the system adjustment output F is updated every 30 seconds; Mp=Kc*(SV-PVn) Mi=Ki*(SV-PVn)+MX Md=KD*(PVn-1-PVn) Mn=Kc*(SV-PVn)+(Ki*(SV-PVn)+MX)+KD*(PVn-1-PVn)+Mcon Mn is the calculated output value of the PID loop at the nth sampling moment; SV is the set value of the PID loop; PVn is the process variable value at the nth sampling moment; PVn-1 is the process variable value at the n-1th sampling time; MX is the value of the previous term of the integral; Mcon is the static output value of the PID loop; Kc is the proportional gain of the PID loop; KI is the proportional constant of the integral term KI = Kc*Ts / Ti; Ts is the sampling time interval during discretization; Ti is the integral time parameter; KD is the proportional constant of the differential term KD = Kc*Td / Ts; Ts is the sampling time interval during discretization; Td is the differential time parameter; Step 10: The PID control system determines the difference between the current temperature acquisition Pn and the initial setting quality Sv in real time, e=Sv-Pn. When the difference e is less than or equal to 1℃ and the time can reach Tim0, the defrost is exited and the compressor accumulated refrigeration time T is reset to zero. If the system defrost conditions are not met, the defrost is exited and the compressor refrigeration time is accumulated again to determine the next defrost.

2. The control method for realizing intelligent frost and reducing energy consumption of refrigerators by using PID control as claimed in claim 1, characterized in that: In step 4, the system output controls the solid-state relay SSR conduction pulse to control the heating power of the heating tube, as follows: The power output adopts the pulse width modulation method, using the solid-state relay SRR to output continuously variable pulses, thereby forming an output voltage Uout with adjustable pulse width, which is given to the defrost heater; When heating output is required, the solid-state relay SSR is triggered and the power supply voltage U AN Add to both ends of the heating tube through the output end of the SSR; When the solid-state relay SSR has no trigger signal, the SSR is turned off, and the average voltage across the heating tube is Uout = (t / T) * U AN =K*U AN , where K = t / T, is the ratio of the SSR triggering conduction in a period T, called the load voltage coefficient or duty cycle, and the change rate of K is between 0 and 1; It is inconvenient to set the cycle T fixedly. Adjust t. When t changes within the range of 0-T, the voltage of the heating tube is between 0-U AN The heating power changes between , the heating tube power P = Uout2 / R, so that the heating power follows the variable.

3. The control method for realizing intelligent frost and reducing energy consumption of refrigerators by using PID control as claimed in claim 2, characterized in that: Step seven is the front end of the adjustment. The SSR and the heating tube are in full-load output state, that is, the SSR conduction pulse duty cycle is F=1. When the temperature rise rate exceeds the control parameter "acceleration rate", the SSR turns off the output.

4. The control method for realizing intelligent frost and reducing energy consumption by using PID control of a refrigerator as claimed in claim 3, characterized in that: Step eight is the adjustment stage. In this stage, the PID regulator adjusts the output and calculates the duty cycle (0-100%) according to the deviation value to ensure that the deviation EV (EV=SV-PV) approaches 0. When the time when the deviation EV (EV=SV-PV) is less than 1°C reaches T0, the SSR output is turned off and the heating of the heating tube stops.

5. The control method for realizing intelligent frost and reducing energy consumption by using PID control of a refrigerator as claimed in claim 4, characterized in that: In step nine, the calculation function of the system adjustment amount is: Mn=Mp+Mi+Md+Mcon M(t)=Kc*e(t)+Kc∫0e(t)dt+Kc*e(t) / dt+Mcon M(t) is the output of the PID loop, which is a function of time; Kc is the proportional gain of the PID loop; e is the deviation EV of the PID loop (EV=SV-PV); and Mcon is the static output value of the PID loop.

6. The control method for realizing intelligent frost and reducing energy consumption of refrigerators by using PID control as claimed in claim 5, characterized in that: In step ten, according to the actual refrigerator, set appropriate coefficient parameters and constant parameters Kc, Ts, Ti, Td, Mcon, set e to maintain 1°C time at T0, determine that defrosting is completed, and end the power supply of the heating tube.

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