A heat pump system with defrost control

Abstract

This invention relates to a heat pump system with defrosting control, comprising: determining in real time whether to update the PWM reference value according to a set rule based on the correlation between ambient temperature, the PWM reference value corresponding to the DC fan speed setting, the system frosting rate, and the frosting thickness; and determining whether the system enters defrosting mode based on the relationship between ambient temperature, the difference between the PWM value of the heat pump system's DC fan and the corresponding PWM reference value, and a set difference threshold; thereby achieving more accurate, efficient, and reliable defrosting determination.

Description

Technical Field

[0001] This invention relates to the field of heat pump system control, and more particularly to a heat pump system with defrost control. Background Technology

[0002] Heat pump systems are a highly efficient and environmentally friendly energy utilization technology. Their core working principle is the reverse Carnot cycle, which uses a small amount of electricity or other energy to transfer heat energy from a low-temperature heat source to a high-temperature environment, achieving heating or cooling. Heat pump systems absorb low-temperature heat energy from the air with minimal electricity, compress it into high-temperature heat energy using a compressor, and then transfer it to the location requiring heating or cooling. They are highly favored by consumers and users and are widely used for cooling and hot water supply in hotels, schools, hospitals, saunas, beauty salons, swimming pools, laundries, and other places.

[0003] Current defrosting methods for variable frequency heat pumps are mainly based on timed defrosting or defrosting settings based on the temperature difference between the ambient temperature and the coil temperature of the heat pump system. In areas or seasons with large changes in outdoor ambient temperature, this fixed parameter setting method often cannot meet the actual defrosting needs, leading to frequent defrosting, failure to defrost when frost is present, and defrosting when there is no frost, which reduces the energy consumption of the system and results in a poor heating or cooling experience for users. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide a heat pump system with defrosting control.

[0005] A heat pump system with defrost control includes a compressor, a four-way valve, a water-side heat exchanger, an electronic expansion valve, and an air-side heat exchanger connected sequentially via refrigerant circulation piping, a DC fan disposed on one side of the air-side heat exchanger, a temperature detection module, and a controller electrically and / or communicatively connected to the four-way valve, the temperature detection module, and the DC fan. The controller determines the defrost state of the heat pump system in the following manner:

[0006] S20 obtains the current ambient temperature.

[0007] If the current ambient temperature Less than or equal to the first ambient temperature defrost threshold Or the current ambient temperature Greater than the first ambient temperature defrost threshold And less than or equal to the second ambient temperature defrost threshold If the defrosting judgment in the previous defrosting cycle was a DC fan defrosting judgment, then step S30 is executed;

[0008] S30 obtains the current defrost interval t. t DC fan speed setting F i t and rotational speed External coil temperature

[0009]

[0010] If the defrosting interval is t t Less than the set minimum defrost interval And it exceeds the set DC fan defrosting monitoring time. And the current DC fan speed Wind speed at gear F i t corresponding set speed Within the fluctuation range, or the defrosting interval t t Greater than or equal to the minimum defrost interval And less than the set maximum defrost interval. And the current temperature of the external coil Less than the second tray defrosting threshold Then proceed to step S40;

[0011] S40 performs DC fan defrosting detection and obtains the current PWM value of the DC fan. t According to the current wind speed F i t Find the corresponding PWM reference value Calculate the PWM reference value PWM value at the current moment t The difference is used to obtain the PWM difference ΔPWM at the current time. t Determine the PWM difference ΔPWM at the current moment. t Is the absolute value of ΔPWM greater than the preset PWM difference threshold? TD :

[0012] If so, the control system enters defrosting mode;

[0013] If not, continue monitoring;

[0014] Among them, the first ambient temperature defrosting threshold <Second ambient temperature defrosting threshold DC fan defrosting monitoring time Minimum defrost interval Maximum defrost interval

[0015] Furthermore, in step S40, the wind speed setting F i Corresponding PWM reference value Obtained through the following methods:

[0016] SA1 obtains the system's power-on status:

[0017] If the system is powered on for the first time, proceed to step SA2;

[0018] If this is not the first time the system has been powered on, then obtain the current ambient temperature.

[0019] Such as ambient temperature Less than or equal to the sampling ambient temperature threshold Then obtain the speed F of the DC fan. i and PWM value i , to the PWM value i Set to speed setting F i Corresponding PWM reference value And store;

[0020] SA2 obtains the current external coil temperature of the system. Ambient temperature

[0021] If the external coil temperature Greater than the first plate temperature defrosting threshold T1 target And ambient temperature Less than or equal to the sampling ambient temperature threshold Then obtain the speed F of the DC fan. i and PWM value i , to the PWM value i Set to speed setting F i Corresponding PWM reference value And store;

[0022] If the external coil temperature Less than or equal to the first plate temperature defrosting threshold T1 target If the duration is greater than or equal to 3 minutes, the control system enters defrosting mode. After defrosting ends and the fan restarts, the speed F of the DC fan is obtained. i and PWM value i , to the PWM value i Set to speed setting F i Corresponding PWM reference value And store.

[0023] Further, in step S40, the PWM reference value Update based on operational status. The update method is as follows:

[0024] SC1 obtains the current defrost interval T of the system. t :

[0025] If the defrosting interval T t Less than the set PWM value sampling period threshold Then continue to obtain the next defrost interval T. t+1 ;

[0026] If the defrosting interval T t Greater than or equal to the set PWM acquisition cycle threshold Obtain the speed F of the DC fan. i and DC fan speed

[0027] Such as DC fan speed Wind speed at gear F i corresponding set speed If the fluctuation range is within the specified range, then execute SC2;

[0028] If it is any other case, and it lasts for 4 minutes, the control system will enter defrosting mode. After defrosting is completed and the fan is restarted, it will continue to acquire the DC fan PWM value.

[0029] SC2 collects the PWM values ​​of the DC fan at a certain sampling frequency over a period of time and calculates the average value of the DC fan PWM values.

[0030] If the average Less than or equal to the stored baseline value Then the average value As a new benchmark Perform step SC3;

[0031] If the average Less than the stored baseline value And greater than the stored baseline value Then the average value The value after increasing C1 by 10% will be used as the new baseline value. Execute step SC3, where

[0032]

[0033] If the average Greater than or equal to the stored baseline value Then the stored baseline value will not be updated.

[0034]

[0035] SC3 determines the new benchmark value Is it within the allowed initial baseline value? Within the fluctuation range:

[0036] If the new benchmark value belong Then the new benchmark value As a benchmark value Update and store;

[0037] In other cases, the baseline value will not be updated, and the control system will enter defrosting mode. After defrosting is completed and the fan is restarted, it will continue to acquire the DC fan PWM value.

[0038] Where C1 represents the first constant and C2 represents the second constant.

[0039] Furthermore, the S50 controls the switching of the four-way valve's working port and obtains the defrosting duration t` and the external coil temperature.

[0040] If the defrost duration t' is greater than or equal to the set defrost time Then, the new reference value will be obtained by lowering the DC fan reference value corresponding to all stored fan speed settings by 10% * C1. Store and exit defrost, controlling the four-way valve to switch its working port; among which,

[0041] If the defrost duration t' is less than the set defrost time And the external coil temperature Greater than or equal to the first defrost exit temperature threshold Then defrosting will be discontinued, and the working port of the four-way valve will be switched.

[0042] If the defrost duration t' is less than the set defrost time And the external coil temperature Greater than or equal to the second defrost exit temperature threshold And less than the first defrost exit temperature threshold If the duration exceeds 10 seconds, defrosting will be discontinued, and the four-way valve's operating port will be switched; the first defrosting discontinuation temperature threshold is specified. Greater than the second defrost exit temperature threshold

[0043]

[0044] In other cases, continue defrosting control;

[0045] The C1 satisfies: C1 = α * 50%; where α represents the defrosting coefficient of the DC fan.

[0046] Furthermore, the following logical judgment is included before step S20:

[0047] S10 obtains the system power-on status:

[0048] If it is not the first power-on, proceed to step S20;

[0049] If this is the first power-on, obtain the current external coil temperature of the system.

[0050] Such as the temperature of the external coil Less than or equal to the first tray defrosting threshold The situation persists for the first time period t1, during which the control system enters defrosting mode and updates the DC fan reference value after exiting defrosting mode.

[0051] If the situation is otherwise, determine the current temperature of the external coil. Does the timed defrosting condition meet the requirements?

[0052] If the conditions are met, the control system will enter the timed defrosting phase;

[0053] If the condition is not met, proceed to step S30.

[0054] Compared with existing technologies, the heat pump system provided by this invention uses the correlation between ambient temperature, the PWM reference value corresponding to the DC fan speed setting, and the system's frosting rate and frosting thickness to determine in real time whether the PWM reference value is updated according to the set rules based on the defrosting interval and DC fan speed; and based on the relationship between ambient temperature, the difference between the PWM value of the heat pump system's DC fan and the corresponding PWM reference value and the set difference threshold, it determines whether the system has entered defrosting mode; thus achieving more accurate, efficient, and reliable defrosting judgment.

[0055] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the system structure according to an embodiment of the present invention;

[0057] Figure 2 This is a flowchart of a control method according to an embodiment of the present invention;

[0058] Figure 3 for Figure 2 The defrosting judgment flowchart. Detailed Implementation

[0059] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings of the embodiments of the present invention.

[0060] To address the shortcomings of existing heat pump systems that rely on fixed parameters such as fixed defrosting intervals and a fixed temperature difference between ambient and coil temperatures, which fail to provide adequate defrosting for applications with significant outdoor temperature variations, this invention proposes a heat pump system with defrost control. This system addresses the issues of frequent defrosting, failure to defrost when frost is present, and defrosting when no frost is present, leading to reduced energy consumption and a poor user experience. Based on research and testing, this invention utilizes the correlation between the DC fan's PWM value and the system's frost rate and thickness. By real-time monitoring of the DC fan's PWM value and timely updates to the PWM baseline, along with comprehensive monitoring of indoor and outdoor temperature and humidity changes, it achieves more precise, efficient, and reliable defrost control.

[0061] For specific implementation details, please refer to [link / reference]. Figure 1 The heat pump system with defrost control proposed in this invention includes a compressor 10, a four-way valve 20, a water-side heat exchanger 30, an electronic expansion valve 40, an air-side heat exchanger 50, and a DC fan 60 disposed on the air-side heat exchanger 50, all connected via refrigerant piping. It also includes a temperature detection module 70, a controller (not shown), and other auxiliary components. The controller is electrically or communicatively connected to the compressor 10, the electronic expansion valve 40, the DC fan 60, and the temperature detection module 70.

[0062] The temperature detection module 70 includes a first temperature sensor 71 and a second temperature sensor 72. The first temperature sensor 71 is installed on the outer coil of the air-side heat exchanger 50 to collect the temperature signal of the outer coil and display the temperature of the outer coil. The data is transmitted to the controller. The second temperature sensor 72 is used to collect ambient temperature data. and ambient temperature The second temperature sensor 72 can be located on the outside of the air-side heat exchanger 50 or on the heat pump system casing, and this application does not impose any restrictions.

[0063] The controller receives the PWM value of the DC fan 60 and the temperature signal collected by the temperature detection module 70, and judges the defrosting of the system according to the stored calculation and judgment program, and controls the four-way valve to switch to defrosting control.

[0064] For details, please refer to Figure 2 The controller of the heat pump system of the present invention performs defrosting judgment and defrosting control of the system through the following method.

[0065] S10 obtains the system power-on status:

[0066] If it is not the first power-on, proceed to step S20;

[0067] If this is the first power-on, obtain the current external coil temperature of the system.

[0068] Such as the temperature of the external coil Less than or equal to the first tray defrosting threshold The situation persists for the first time period t1, during which the control system enters defrosting mode and updates the DC fan reference value after exiting defrosting mode.

[0069] If the situation is otherwise, determine the current temperature of the external coil. Does the timed defrosting condition meet the requirements?

[0070] If the conditions are met, the control system will enter the timed defrosting phase;

[0071] If the condition is not met, proceed to step S30.

[0072] In specific implementation, the first plate temperature defrosting threshold The setting range is -8℃ to -6℃, with -7℃ being preferred.

[0073] The first time period t1 is set to a range of 2 min to 4 min, preferably 3 min.

[0074] The timed defrosting conditions are as follows:

[0075] Current external coil temperature Greater than the first tray defrosting threshold And less than the second tray defrosting threshold. Furthermore, the defrosting interval t at the current moment t Greater than or equal to the set minimum defrost interval

[0076] The second plate temperature defrosting threshold The setting range is -4 to -2℃, with -3℃ being preferred.

[0077] The minimum defrost interval Set to 45 minutes.

[0078] S20 obtains the current ambient temperature.

[0079] If the current ambient temperature Less than or equal to the first ambient temperature defrost threshold Then proceed to step S30;

[0080] If the current ambient temperature Greater than the first ambient temperature defrost threshold And less than or equal to the second ambient temperature defrost threshold Then retrieve the defrost determination from the previous defrost cycle:

[0081] If the defrosting judgment in the previous defrosting cycle was a DC fan defrosting judgment, then proceed to step S30;

[0082] The defrosting judgment for the previous defrosting cycle was based on the external coil temperature. The determination is based on the current temperature of the external coil. Determine whether the conditions for timed defrosting are met. If they are met, the control system enters the timed defrosting phase.

[0083] If the current ambient temperature Greater than the second ambient temperature defrosting threshold Then we will continue to monitor it.

[0084] In specific implementation, the first ambient temperature defrosting threshold Set to 10℃; the second ambient temperature defrost threshold. Set to 14℃.

[0085] Furthermore, in the case of several DC fans, if any one of the DC fans is malfunctioning or has a fault, the current external coil temperature will be used as the basis for the adjustment. Determine if the system has entered the scheduled defrosting phase.

[0086] S30 obtains the current defrost interval t. t DC fan speed setting F i t and rotational speed External coil temperature

[0087]

[0088] If the defrosting interval is t t Less than the set minimum defrost interval And longer than the DC fan defrosting monitoring time Right now Then, the current DC fan speed is further determined. Is the current gear and wind speed F? i t corresponding set speed Within the fluctuation range, i.e., whether it meets the requirements.

[0089] If so, that is Then proceed to step S40;

[0090] If not, that is If the duration is greater than or equal to 4 minutes, the control system enters defrosting execution S50; if the defrosting interval time t t Greater than or equal to the minimum defrost interval And less than the set maximum defrost interval. And the current temperature of the external coil Less than the second tray defrosting threshold Right now and Then proceed to step S40;

[0091] If the defrosting interval is t t Greater than the maximum defrost interval Right now The control system then enters defrosting execution S50;

[0092] In other cases, we will continue to monitor them.

[0093] In specific implementation, the defrosting interval t t This refers to the time period from the current running time after the system enters working mode until the end of the previous defrosting cycle.

[0094] The maximum defrost interval The setting range is 5.5h to 6.5h, with 6.0h being preferred.

[0095] The minimum defrost interval The setting range is 40min to 50min, with 45min being the preferred setting.

[0096] The DC fan defrosting monitoring time The setting range is 9 min to 11 min, with 10 min being the preferred setting.

[0097] S40 performs DC fan defrosting detection and obtains the current PWM value of the DC fan. t According to the current wind speed F i t Find the corresponding PWM reference value Where the PWM reference value Update based on operational status; calculate PWM baseline value. PWM value at the current moment t The difference is used to obtain the PWM difference ΔPWM at the current time. t Determine the PWM difference ΔPWM at the current moment. t Is the absolute value of ΔPWM greater than the preset PWM difference threshold? TD :

[0098] If so, the control system enters defrosting execution S50;

[0099] If not, continue monitoring.

[0100] In practical implementation, the sampling of the DC fan PWM value satisfies the following:

[0101] (1) During sampling, the wind speed F of the DC fan is at the set speed F i Within the allowable fluctuation range, i.e., F∈(F i ±10RPM); Example: The sampling range for a wind speed setting of 720RPM is between 710RPM and 730RPM.

[0102] (2) The sampling period is 1 minute;

[0103] (3) The sampling frequency is 60 times / min.

[0104] The PWM difference threshold ΔPWM TD The setting range is 490 to 510, with 500 being preferred.

[0105] The speed range F of the DC fan i Including (F1, F2, ..., F9), i.e., F1 to F9, corresponding to different PWM reference values. Right now Furthermore, the baseline values ​​can be updated in real time based on operating conditions and operating environment.

[0106] The gear speed F i Corresponding PWM reference value Obtained through the following methods:

[0107] SA1 obtains the system's power-on status:

[0108] If the system is powered on for the first time, proceed to step SA2;

[0109] If this is not the first time the system has been powered on, then obtain the current ambient temperature.

[0110] Such as ambient temperature Greater than the set sampling ambient temperature threshold Then continuously obtain the ambient temperature at the next moment.

[0111] Such as ambient temperature Less than or equal to the sampling ambient temperature threshold Then obtain the speed F of the DC fan. i and PWM value i , to the PWM value i Set to speed setting F i Corresponding PWM reference value And store.

[0112] SA2 obtains the current external coil temperature of the system.

[0113] If the external coil temperature Greater than the first plate temperature defrosting threshold T1 target Then, the current ambient temperature is obtained.

[0114] Such as ambient temperature greater than the sampling ambient temperature threshold Then continuously obtain the external coil temperature at the next moment.

[0115] Such as ambient temperature Less than or equal to the sampling ambient temperature threshold Then obtain the speed F of the DC fan. i and PWM value i , to the PWM value i Set to speed setting F i Corresponding PWM reference value And store;

[0116] If the external coil temperature Less than or equal to the first plate temperature defrosting threshold T1 target If the defrosting duration is greater than or equal to 3 minutes, the control system will immediately enter defrosting mode. After defrosting is completed and the DC fan is restarted, the speed F of the DC fan will be obtained. i and PWM value i , to the PWM value i Set to speed setting F i Corresponding PWM reference value And store.

[0117] This method is used to ensure that the PWM reference value of the DC fan is obtained in a frost-free state.

[0118] In specific implementation, the sampling ambient temperature threshold The setting range is 7 to 9°C, with 8°C being preferred.

[0119] The PWM reference value Update based on operational status. The specific update method is as follows:

[0120] SC1 obtains the current defrost interval T of the system. t :

[0121] If the defrosting interval T t Less than the set PWM value sampling period threshold Then continue to obtain the next defrost interval T. t+1 ;

[0122] If the defrosting interval T t Greater than or equal to the set PWM acquisition cycle threshold Obtain the speed F of the DC fan. i and DC fan speed R t :

[0123] For example, the speed R of a DC fan t Wind speed at gear F i corresponding set speed Within the fluctuation range, i.e. Then execute SC2;

[0124] In other cases, and if the defrosting lasts for 4 minutes, the control system will enter defrosting mode. After defrosting is completed and the fan is restarted, it will continue to acquire the DC fan PWM value.

[0125] SC2 collects the PWM values ​​of the DC fan at a certain sampling frequency for a period of time, and calculates the average value of the collected DC fan PWM values.

[0126] If the average Less than or equal to the stored baseline value Then the average value As a new benchmark Perform step SC3;

[0127] If the average Less than the stored baseline value And greater than the stored baseline value Then the average value The value after increasing C1 by 10% will be used as the new baseline value. Execute step SC3, where

[0128]

[0129] If the average Greater than or equal to the stored baseline value Then the stored baseline value will not be updated.

[0130]

[0131] In specific implementation, the first constant C1 = α * 50%, where α represents the defrosting coefficient of the DC fan.

[0132] SC3 determines the new benchmark value Is it within the allowed initial baseline value? Within the fluctuation range:

[0133] If the new benchmark value belong Then the new benchmark value As a benchmark value Update and store;

[0134] In other cases, the baseline value will not be updated, and the control system will enter defrosting mode. After defrosting is completed and the fan is restarted, it will continue to acquire the DC fan PWM value.

[0135] In practice, the second constant C2 = α * 150%.

[0136] The PWM reference value corresponding to the DC fan speed setting can be updated once after N defrosting cycles.

[0137] The S50 controls the switching of the four-way valve's working port and obtains the defrosting duration t` and the external coil temperature.

[0138] If the defrost duration t' is greater than the set defrost time Then proceed to step S60;

[0139] If the defrost duration t' is less than the set defrost time And the external coil temperature Greater than or equal to the first defrost exit temperature threshold Then defrosting is stopped, the working port of the four-way valve is switched and step S20 is executed;

[0140] If the defrost duration t' is less than the set defrost time And the external coil temperature Greater than or equal to the second defrost exit temperature threshold And less than the first defrost exit temperature threshold If the duration is greater than 10 seconds, defrosting will be stopped, the working port of the four-way valve will be switched, and step S20 will be executed.

[0141] In other cases, continue defrosting control.

[0142] In specific implementation, the defrosting time The setting range is 8 minutes to 10 minutes.

[0143] The first defrost exit temperature threshold The setting range is 24–26℃, preferably 25℃. This is the second defrost exit temperature threshold. The setting range is 14–16℃, with 15℃ being preferred.

[0144] S60 uses the new reference value obtained by lowering the DC fan reference value corresponding to all stored fan speed levels by 10% * C1. Store and exit defrosting, control the four-way valve to switch its working port and execute step S20; wherein,

[0145] Compared to existing technologies, the heat pump system with defrost control mode of the present invention uses the correlation between ambient temperature, the PWM reference value corresponding to the DC fan speed setting, and the system's frosting rate and frosting thickness to determine in real time whether to update the PWM reference value according to the set rules based on the defrost interval and DC fan speed; and based on the relationship between the ambient temperature, the difference between the PWM value of the heat pump system's DC fan and the corresponding PWM reference value and the set difference threshold, it determines whether the system has entered defrost mode; thus achieving more accurate, efficient and reliable defrost determination.

[0146] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. The singular forms “a,” “the,” and “the” used in the embodiments and claims of this application are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that, unless otherwise stated, “a plurality” and “several” refer to two or more; “and / or” refers to and includes any or all possible combinations of one or more associated listed items; “first,” “second,” “third,” etc., are used only to distinguish and not to describe a particular order or sequence, nor should they be construed as indicating or implying relative importance. When the above description relates to drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. In the description of this application, those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0147] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and the present invention also intends to include these modifications and variations.

Claims

1. A heat pump system with defrost control, comprising a compressor, a four-way valve, a water-side heat exchanger, an electronic expansion valve, and an air-side heat exchanger connected sequentially via refrigerant circulation piping, a DC fan disposed on one side of the air-side heat exchanger, a temperature detection module, and a controller electrically and / or communicatively connected to the four-way valve, the temperature detection module, and the DC fan, characterized in that, The controller determines whether the heat pump system is to defrost using the following method: S20 obtains the current ambient temperature. If the current ambient temperature Less than or equal to the first ambient temperature defrost threshold Or the current ambient temperature Greater than the first ambient temperature defrost threshold And less than or equal to the second ambient temperature defrost threshold If the defrosting judgment in the previous defrosting cycle was a DC fan defrosting judgment, then step S30 is executed; S30 obtains the current defrost interval t. t DC fan speed setting F i t and rotational speed External coil temperature If the defrosting interval is t t Less than the set minimum defrost interval And it exceeds the set DC fan defrosting monitoring time. And the current DC fan speed Wind speed at gear F i t corresponding set speed Within the fluctuation range, or the defrosting interval t t Greater than or equal to the minimum defrost interval And less than the set maximum defrost interval. And the current temperature of the external coil Less than the second plate temperature defrosting threshold Then proceed to step S40; S40 performs DC fan defrosting detection and obtains the current PWM value of the DC fan. t ; Based on the current gear and wind speed F i t Find the corresponding PWM reference value Calculate the PWM reference value PWM value at the current moment t The difference is used to obtain the PWM difference ΔPWM at the current time. t Determine the PWM difference ΔPWM at the current moment. t Is the absolute value of ΔPWM greater than the preset PWM difference threshold? TD : If so, the control system enters defrosting mode; If not, continue monitoring; Among them, the first ambient temperature defrosting threshold <Second ambient temperature defrosting threshold DC fan defrosting monitoring time Minimum defrost interval Maximum defrost interval Among them, the gear speed F i Corresponding PWM reference value Obtained through the following methods: SA1 obtains the system's power-on status: If the system is powered on for the first time, proceed to step SA2; If this is not the first time the system has been powered on, then obtain the current ambient temperature. Such as ambient temperature Less than or equal to the sampling ambient temperature threshold Then obtain the speed F of the DC fan. i and PWM value i , to the PWM value i Set to speed setting F i Corresponding PWM reference value And store; SA2 obtains the current external coil temperature of the system. Ambient temperature If the external coil temperature Greater than the first plate temperature defrosting threshold T1 target And ambient temperature Less than or equal to the sampling ambient temperature threshold Then obtain the speed F of the DC fan. i and PWM value i , to the PWM value i Set to speed setting F i Corresponding PWM reference value And store; If the external coil temperature Less than or equal to the first plate temperature defrosting threshold T1 target If the duration is greater than or equal to 3 minutes, the control system enters defrosting mode. After defrosting ends and the fan restarts, the speed F of the DC fan is obtained. i and PWM value i , to the PWM value i Set to speed setting F i Corresponding PWM reference value And store.

2. The heat pump system according to claim 1, characterized in that, The PWM reference value in step S40 Update based on operational status. The update method is as follows: SC1 obtains the current defrost interval T of the system. t : If the defrosting interval T t Less than the set PWM value sampling period threshold Then continue to obtain the next defrost interval T. t+1 ; If the defrosting interval T t Greater than or equal to the set PWM acquisition cycle threshold Obtain the speed F of the DC fan. i and DC fan speed Such as DC fan speed Wind speed at gear F i corresponding set speed If the fluctuation range is within the specified range, then execute SC2; If it is any other case, and it lasts for 4 minutes, the control system will enter defrosting mode. After defrosting is completed and the fan is restarted, it will continue to acquire the DC fan PWM value. SC2 collects the PWM values ​​of the DC fan at a certain sampling frequency over a period of time and calculates the average value of the DC fan PWM values. If the average Less than or equal to the stored baseline value Then the average value As a new benchmark Perform step SC3; If the average Less than the stored baseline value And greater than the stored baseline value Then the average value The value after increasing C1 by 10% will be used as the new baseline value. Execute step SC3, where If the average Greater than or equal to the stored baseline value Then the stored baseline value will not be updated. SC3 determines the new benchmark value Is it within the allowed initial baseline value? Within the fluctuation range: If the new benchmark value belong Then the new benchmark value As a benchmark value Update and store; In other cases, the baseline value will not be updated, and the control system will enter defrosting mode. After defrosting is completed and the fan is restarted, it will continue to acquire the DC fan PWM value. Where C1 represents the first constant and C2 represents the second constant.

3. The heat pump system according to claim 2, characterized in that, The first constant C1 satisfies: C1＝α*50％； The second constant C2 satisfies: C2＝α*150％； Where α represents the defrosting coefficient of the DC fan.

4. The heat pump system according to claim 3, characterized in that, The sampling of the DC fan PWM value satisfies: During sampling, the DC fan speed F is at the set speed F i Within the allowable fluctuation range, that is, F is within (F i ±10RPM); The sampling period is 1 minute; The sampling frequency is 60 times / min.

5. The heat pump system according to any one of claims 1, 2, 3, and 4, characterized in that, The DC fan defrosting monitoring time The setting range is 9 minutes to 11 minutes; the minimum defrosting interval duration is... The setting range is 40 min to 50 min; the maximum defrosting interval duration is... The setting range is 5.5h to 6.5h.

6. The heat pump system according to claim 5, characterized in that, First ambient temperature defrosting threshold Set to 10℃; the second ambient temperature defrost threshold. Set to 14℃.

7. The heat pump system according to claim 6, characterized in that, The DC fan has speed settings (F1, F2, ..., F9), and the PWM reference value for each speed setting is...

8. The heat pump system according to claim 1, characterized in that, The defrosting process includes the following logic control: The S50 controls the switching of the four-way valve's working port and obtains the defrosting duration t` and the external coil temperature. If the defrost duration t' is greater than or equal to the set defrost time Then, the new reference value will be obtained by lowering the DC fan reference value corresponding to all stored fan speed settings by 10% * C1. Store and exit defrost, controlling the four-way valve to switch its working port; among which, If the defrost duration t' is less than the set defrost time And the external coil temperature Greater than or equal to the first defrost exit temperature threshold Then defrosting will be discontinued, and the working port of the four-way valve will be switched. If the defrost duration t' is less than the set defrost time And the external coil temperature Greater than or equal to the second defrost exit temperature threshold And less than the first defrost exit temperature threshold If the duration exceeds 10 seconds, defrosting will be discontinued, and the four-way valve's operating port will be switched; the first defrosting discontinuation temperature threshold is specified. Greater than the second defrost exit temperature threshold In other cases, continue defrosting control; The C1 satisfies: C1 = α * 50%; where α represents the defrosting coefficient of the DC fan.

9. The heat pump system according to claim 1, characterized in that, The following logical judgment is also included before step S20: S10 obtains the system power-on status: If it is not the first power-on, proceed to step S20; If this is the first power-on, obtain the current external coil temperature of the system. Such as the temperature of the external coil Less than or equal to the first tray defrost threshold The situation persists for the first time period t1, during which the control system enters defrosting mode and updates the DC fan reference value after exiting defrosting mode. If the situation is otherwise, determine the current temperature of the external coil. Does the timed defrosting condition meet the requirements? If the conditions are met, the control system will enter the timed defrosting phase; If the condition is not met, proceed to step S30.

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