Heat storage and defrosting control method for heat pump

Abstract

The invention discloses a heat pump heat storage defrosting control method which comprises the following steps: outdoor temperature acquisition: after starting to heat, performing data acquisition on the surface temperature of an outdoor heat exchanger at regular time; temperature deviation is calculated, specifically, temperature data sampled each time are set to be Tn, the temperature difference Tn = Tn-T0 during sampling each time is calculated, and the sampling frequency is t / time; calculating a temperature change rate: calculating a real-time temperature change rate according to the acquisition evaluation rate; frosting degree judgment, wherein the frosting degree is divided into mild frosting, moderate frosting or severe frosting according to the temperature difference and the temperature change rate; and according to the frosting degree, different strategies are adopted to adjust the opening degree of the main electronic expansion valve and the auxiliary electronic expansion valve, and a refrigerant is called to enter the outdoor heat exchanger for defrosting. The frosting degree is subdivided, and the opening degree of the main electronic expansion valve and the opening degree of the auxiliary electronic expansion valve are adjusted through different strategies, so that the situation that the indoor temperature is greatly reduced during mild frosting or moderate frosting is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of air-conditioning systems, and in particular to a heat pump heat storage and defrosting control method. Background Art

[0002] When a household heat pump is operating in winter, the outdoor heat exchanger frosts due to the low evaporation temperature, which reduces heat exchange capacity and significantly reduces heating effectiveness. Therefore, it needs to be defrosted after a period of operation. Traditional heat pump defrosting typically uses a reverse cycle defrosting method, which changes the flow of refrigerant so that the refrigerant discharged from the compressor is first defrosted through the outdoor heat exchanger, then flows into the indoor heat exchanger, and finally returns to the compressor. During defrosting, due to the low temperature of the indoor unit pipes, to prevent cold air from blowing out and causing discomfort to the user, the indoor fan remains off during the defrost phase. Therefore, no heat is supplied to the indoor unit during the defrost process. In addition, current heat storage defrosting heat pumps cannot accurately determine the frost condition and use the same defrost mode for both thick and thin frost. Not only may the defrost not be completely removed, but it can also easily cause room temperature fluctuations, affecting user comfort. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a heat pump thermal storage defrost control method that can finely control defrost, reduce room temperature fluctuations in defrost mode, and improve user experience.

[0004] A heat pump thermal storage defrost control method according to an embodiment of the present invention includes the following steps: Outdoor temperature collection: After turning on the heating, the surface temperature of the outdoor heat exchanger is collected regularly to obtain a series of temperature values. The defrost temperature of the outdoor heat exchanger surface is set as T0. Calculate temperature deviation: Set the temperature data of each sampling as Tn (n=1, 2, 3...), calculate the temperature difference of each sampling △Tn=Tn-T0, sampling frequency △t / time; Calculate the temperature change rate: For the data collected at two adjacent information collection moments, calculate the real-time temperature change rate based on the collection rate; Frost degree judgment: The frost degree is divided into light frost, moderate frost or heavy frost according to the temperature difference and the temperature change rate; Defrost: According to the degree of frost, different strategies are used to adjust the opening of the main electronic expansion valve and the auxiliary electronic expansion valve, and refrigerant is called into the outdoor heat exchanger for defrosting.

[0005] It has at least the following beneficial effects: by subdividing the degree of frost and adopting different strategies to adjust the opening of the main electronic expansion valve and the auxiliary electronic expansion valve, when there is light or moderate frost, the refrigerant flow to the outdoor heat exchanger is reduced, and the refrigerant flow to the indoor heat exchanger is guaranteed, thereby achieving maximum protection of the indoor temperature and avoiding a large drop in indoor temperature when there is light or moderate frost.

[0006] According to some embodiments of the present invention, in the step of calculating the temperature change rate, the temperature change rate is set to -D, where A and D are constant coefficients.

[0007] According to some embodiments of the present invention, in the frost degree determination step, when ΔTn is within a first temperature difference interval, kn is within a first temperature change rate interval, and both the temperature difference ΔTn and the temperature change rate kn are within this interval during the X1 period, then the frost degree is determined to be light frost; When ΔTn is in the second temperature difference interval, kn is in the second temperature change rate interval, and both the temperature difference ΔTn and the temperature change rate kn are within this interval during the X2 period, the degree of frost is determined to be moderate frost; When ΔTn is in the third temperature difference interval, kn is in the third temperature change rate interval, and the temperature difference ΔTn and the temperature change rate kn remain within this range for more than X3 time, the frosting degree is determined to be severe frosting.

[0008] According to some embodiments of the present invention, in the defrosting step, when there is light frost, the openings of the main electronic expansion valve and the auxiliary electronic expansion valve are adjusted so that the flow ratio of the refrigerant flowing to the outdoor heat exchanger and the indoor heat exchanger is a first ratio.

[0009] According to some embodiments of the present invention, during the defrosting step when there is slight frost, the rotation speed of the fan of the indoor heat exchanger is simultaneously reduced.

[0010] According to some embodiments of the present invention, in the defrosting step, when moderate frost occurs, the openings of the main electronic expansion valve and the auxiliary electronic expansion valve are adjusted so that the flow ratio of the refrigerant to the outdoor heat exchanger and the indoor heat exchanger is a second ratio.

[0011] According to some embodiments of the present invention, during the defrosting step at moderate frost conditions, the rotational speed of the fan of the indoor heat exchanger is simultaneously reduced.

[0012] According to some embodiments of the present invention, in the defrosting step, when frosting is severe, the openings of the main electronic expansion valve and the auxiliary electronic expansion valve are adjusted so that the flow ratio of the refrigerant to the outdoor heat exchanger and the indoor heat exchanger is a third ratio.

[0013] According to some embodiments of the present invention, during the defrosting step in the case of heavy frost, fans of the outdoor heat exchanger and the indoor heat exchanger are stopped.

[0014] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which: Figure 1 This is a flow chart of an embodiment of the present invention; Figure 2 This is a system diagram of a heating mode according to an embodiment of the present invention; Figure 3 This is a system diagram of the defrost mode according to an embodiment of the present invention.

[0016] Figure numbers: compressor 1, gas-liquid separator 2, four-way valve 3, three-way valve 4, indoor heat exchanger 5, outdoor heat exchanger 6, double heat exchange tube heat accumulator 7, first solenoid valve 8, second solenoid valve 9, third solenoid valve 10, main electronic expansion valve 11, auxiliary electronic expansion valve 12, fourth solenoid valve 13, fifth solenoid valve 14, sixth solenoid valve 15, temperature sensor 16. DETAILED DESCRIPTION

[0017] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.

[0018] In the description of the present invention, if there is a description of first and second, it is only for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0019] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0020] Reference Figures 2 to 3 The cycle structure of a heat pump thermal storage defrost control system according to an embodiment of the present invention is as follows: Reference Figure 2In the system's heating mode, the orderly flow of refrigerant is achieved through the switching states of specific solenoid valves. Third solenoid valve 10 is open, while first and second solenoid valves 8 and 9 are closed. This allows the refrigerant to sequentially pass through compressor 1, four-way valve 3, indoor heat exchanger 5, auxiliary electronic expansion valve 12, third solenoid valve 10, main electronic expansion valve 11, outdoor heat exchanger 6, and finally return to compressor 1 to complete the cycle. This flow control ensures that during the heating process, the refrigerant can effectively release heat indoors and absorb heat outdoors, achieving efficient heating.

[0021] Reference Figure 2 In the system heating mode, part of the high-temperature refrigerant is output from the compressor 1, passes through the fourth solenoid valve 13, and then enters the double heat exchange tube heat accumulator 7 through two pipelines. Then the refrigerant passes through the sixth solenoid valve 15 and enters the indoor heat exchanger 5, the main electronic expansion valve 11, and the outdoor heat exchanger 6 in sequence, and finally returns to the compressor 1 to complete the cycle, achieving efficient heat storage.

[0022] Reference Figure 3 When defrosting is required, three-way valve 4 switches to open ports b and c, and third solenoid valve 10 closes, forming a diversion branch. A portion of the high-temperature, high-pressure gaseous refrigerant flows into indoor heat exchanger 5 for heating, while the remaining portion flows through the diversion branch to outdoor heat exchanger 6 for defrosting. The medium-temperature, high-pressure liquid refrigerant flowing from indoor and outdoor heat exchangers 5 and 6 is throttled and reduced in pressure by auxiliary electronic expansion valve 12 and main electronic expansion valve 11, respectively, before entering both ends of heat accumulator 7 through first solenoid valve 8 and second solenoid valve 9. This achieves optimal heat distribution and utilization, ensuring both defrosting effectiveness and maintaining basic indoor heating.

[0023] It should be noted that during the heating phase, heat accumulator 7 absorbs heat from the refrigerant and stores it. When the air conditioner enters defrost mode, the condensed refrigerant is passed into heat accumulator 7, where it evaporates the refrigerant. In other words, heat accumulator 7 acts as an evaporator, replacing indoor heat exchanger 5. This eliminates the need for evaporative cooling in indoor heat exchanger 5 and does not affect the temperature balance of indoor heat exchanger 5.

[0024] Reference Figure 1 The present invention discloses a heat pump heat storage defrosting control method, comprising the following steps: Outdoor temperature collection: After turning on the heating, the surface temperature of the outdoor heat exchanger 6 is collected regularly to obtain a series of temperature values, and the defrost temperature of the outdoor heat exchanger surface is set as T0; Calculate temperature deviation: Set the temperature data of each sampling as Tn (n=1, 2, 3...), calculate the temperature difference of each sampling △Tn=Tn-T0, sampling frequency △t / time; Calculate the temperature change rate: For the data collected at two adjacent information collection moments, calculate the real-time temperature change rate based on the collection rate; Frost degree judgment: The frost degree is divided into light frost, moderate frost or heavy frost according to the temperature difference and the temperature change rate; Defrost: According to the degree of frost, different strategies are adopted to adjust the opening of the main electronic expansion valve 11 and the auxiliary electronic expansion valve 12, and refrigerant is called into the outdoor heat exchanger 6 for defrosting.

[0025] By subdividing the degree of frost and adopting different strategies to adjust the opening of the main electronic expansion valve 11 and the auxiliary electronic expansion valve 12, when there is light or moderate frost, the refrigerant flow to the outdoor heat exchanger 6 is reduced to ensure the refrigerant flow to the indoor heat exchanger 5, thereby achieving maximum protection of the indoor temperature and avoiding a large drop in indoor temperature when there is light or moderate frost.

[0026] Furthermore, in the step of calculating the temperature change rate, set: Temperature change rate -D, where A and D are constant coefficients.

[0027] It is worth noting that the values ​​of A and D are set by those skilled in the art according to design requirements. In the embodiment of the present invention, A=0.5 and D=0.3.

[0028] Furthermore, in the frost degree determination step, when ΔTn is in the first temperature difference interval, kn is in the first temperature change rate interval, and both the temperature difference ΔTn and the temperature change rate kn are within this interval during the X1 period, the frost degree is determined to be light frost; When ΔTn is in the second temperature difference interval, kn is in the second temperature change rate interval, and both the temperature difference ΔTn and the temperature change rate kn are within this interval during the X2 period, the degree of frost is determined to be moderate frost; When ΔTn is in the third temperature difference interval, kn is in the third temperature change rate interval, and the temperature difference ΔTn and the temperature change rate kn remain within this range for more than X3 time, the frosting degree is determined to be severe frosting.

[0029] It should be noted that the durations of X1, X2 and X3 are set by those skilled in the art according to design requirements. In an embodiment of the present invention, the duration of X1 is 3-5 minutes, the duration of X2 is 5-10 minutes and the duration of X3 is 10 minutes.

[0030] It should be noted that the values ​​of the first temperature difference interval, the second temperature difference interval, the third temperature difference interval, the first temperature change rate interval, the second temperature change rate interval, and the third temperature change rate interval can be set by those skilled in the art according to design requirements; In an embodiment of the present invention, the first temperature difference range is -3°C ≤ ΔTn < -1°C; the second temperature difference range is -6°C ≤ ΔTn < -3°C; and the third temperature difference range is ΔTn < -6°C.

[0031] In an embodiment of the present invention, the first temperature change rate interval is -0.5°C / s≤kn<-0.2°C / s; the second temperature change rate interval is -1°C / s≤kn<-0.5°C / s; and the third temperature change rate interval is kn<-1°C / s.

[0032] It is worth noting that the temperature information is collected regularly by the temperature sensor 16 on the outdoor heat exchanger 6, and the calculation of the temperature difference △Tn and the temperature change rate kn can determine the thickness of the frost layer on the outdoor heat exchanger 6 and the corresponding degree of frost, and the degree of frost can be divided into light frost, moderate frost or heavy frost, so as to facilitate the adoption of different defrosting strategies.

[0033] It should be noted that, in the embodiment of the present invention, when -3℃≤△Tn<-1℃, it means that the surface temperature of the outdoor heat exchanger 6 begins to approach the frost formation temperature, but has not yet dropped significantly. At this time, if -0.5℃ / s≤kn<-0.2℃ / s, it indicates that the temperature drop rate is relatively slow, and frost begins to form, but the speed is not fast; the above-mentioned temperature deviation and temperature change rate conditions are met for a certain period of time, and the temperature difference △Tn and the temperature change rate kn are both within this range within the X2 period. This is to eliminate the influence of accidental temperature fluctuations and ensure that frosting is a continuous process. When the above three conditions are met, the degree of frosting is determined to be light frosting.

[0034] In an embodiment of the present invention, when the temperature difference ΔTn further increases and reaches -6°C ≤ ΔTn < -3°C, the surface temperature of the outdoor heat exchanger is lower and the frosting condition is aggravated. If the temperature change rate kn is in the range of -0.5°C / s ≤ kn < -0.2°C / s and is maintained for the X2 period, the degree of frosting is judged to be moderate.

[0035] In this embodiment of the present invention, when the temperature deviation ΔTn is less than -6°C, it indicates a significant temperature deviation, indicating that the surface temperature of the outdoor heat exchanger 6 is extremely low and frosting is very severe. At this time, if kn is less than -1°C / s, it indicates a rapid temperature drop and extremely rapid frosting. If the above temperature difference and temperature change rate conditions persist for more than 10 minutes, the frosting is considered severe.

[0036] Furthermore, in the defrosting step, when there is slight frost, the openings of the main electronic expansion valve 11 and the auxiliary electronic expansion valve 12 are adjusted so that the flow ratio of the refrigerant flowing to the outdoor heat exchanger 6 and the indoor heat exchanger 5 is a first ratio.

[0037] Specifically, in an embodiment of the present invention, in the case of mild frosting, the opening of the main electronic expansion valve 11 can be maintained at a relatively small value. This is because only a portion of the refrigerant is needed for defrosting the outdoor heat exchanger 6, and a large amount of refrigerant is not required to quickly flow into the outdoor heat exchanger 6. The opening of the auxiliary electronic expansion valve 12 can be appropriately larger than the opening of the main electronic expansion valve 11. This is because it is still necessary to ensure that the indoor heat exchanger has sufficient refrigerant to maintain a certain heating effect.

[0038] Specifically, assuming a typical residential heat pump air conditioning system, the maximum opening of the main electronic expansion valve 11 and the auxiliary electronic expansion valve 12 is 400 steps. During normal heating operation (no frost), to ensure proper distribution of refrigerant and efficient heat exchange, the initial full opening of the main electronic expansion valve 11 is set to approximately 200-240 steps (herein, the initial full opening is set to 200 steps), and the initial full opening of the auxiliary electronic expansion valve 12 is set to approximately 240-280 steps (herein, the initial full opening is set to 240 steps). This configuration allows the refrigerant to be distributed between the indoor heat exchanger 5 and the outdoor heat exchanger 6 in a certain ratio, meeting the indoor heating demand and ensuring normal heat exchange in the outdoor heat exchanger 6. Therefore, when light frost forms, the main electronic expansion valve 11 is set to an opening between 30% and 50% of its initial full opening, which means the opening can be adjusted between 60 and 100 steps, and the auxiliary electronic expansion valve 12 is set to a opening between 50% and 70% of its initial full opening, which means the opening can be adjusted between 120 and 168 steps. This allows the outdoor heat exchanger 6 to be defrosted while maintaining the indoor temperature.

[0039] Furthermore, in the defrosting step when there is slight frost, the rotation speed of the fan of the indoor heat exchanger 5 is simultaneously reduced.

[0040] In an embodiment of the present invention, the maximum operating speed of the fan of the indoor heat exchanger 5 is first obtained, and the speed of the fan of the indoor heat exchanger 5 is reduced to 80%-90% of the maximum operating speed.

[0041] It is worth noting that in some embodiments of the present invention, when light frost occurs, the fan speed of the outdoor heat exchanger 6 is appropriately reduced to reduce the convective heat exchange between the outdoor cold air and the heat exchanger, thereby preventing the heat exchanger surface temperature from being too low and facilitating the slow melting of the frost layer. Therefore, the fan speed of the outdoor heat exchanger 6 is reduced from 1000 rpm to 600-800 rpm. At the same time, to maintain a comfortable indoor temperature environment, the fan speed of the indoor heat exchanger 5 can also be maintained at approximately 80%-90% of the maximum operating speed. For example, if the maximum operating speed is 1200 rpm, it can be maintained at 960-1080 rpm.

[0042] Furthermore, in the defrosting step, when the frost is moderate, the openings of the main electronic expansion valve 11 and the auxiliary electronic expansion valve 12 are adjusted so that the flow ratio of the refrigerant to the outdoor heat exchanger 6 and the indoor heat exchanger 5 is the second ratio.

[0043] Similarly, in some embodiments of the present invention, when there is moderate frost, the opening of the main electronic expansion valve 11 should be larger than when there is light frost, because the frost layer is thicker at this time, and more refrigerant is required to flow through the outdoor heat exchanger 6 for effective defrosting; the opening of the auxiliary electronic expansion valve 12 should be reduced accordingly, because it is necessary to adjust the diversion ratio of the refrigerant to reduce the refrigerant flowing to the indoor heat exchanger 5, thereby increasing the refrigerant flow to the outdoor heat exchanger 6 for defrosting.

[0044] Furthermore, in some embodiments of the present invention, during normal heating operation (no frost), the initial full opening of the main electronic expansion valve 11 is also set to 200 steps, and the initial full opening of the auxiliary electronic expansion valve 12 is also set to 240 steps.

[0045] Therefore, when frosting is moderate, the opening of the main electronic expansion valve 11 is set to between 50% and 70% of the initial full opening, that is, the opening can be adjusted to between 100 and 140 steps, and the auxiliary electronic expansion valve 12 is set to between 30% and 50% of the initial full opening, that is, the opening can be adjusted to between 72 and 120 steps.

[0046] Furthermore, in the defrosting step when the frost is moderate, the rotation speed of the fan of the indoor heat exchanger 5 is simultaneously reduced.

[0047] In an embodiment of the present invention, the maximum operating speed of the fan of the indoor heat exchanger 5 is first obtained, and the speed of the fan of the indoor heat exchanger 5 is reduced to 60%-70% of the maximum operating speed.

[0048] It is worth noting that in some embodiments of the present invention, when moderate frost occurs, the fan speed of the outdoor heat exchanger 6 should be further reduced. This is because as the frost layer thickens, the heat exchange capacity of the outdoor heat exchanger 6 decreases significantly. Reducing the fan speed can reduce the cooling effect of the cold air on the frost layer and prevent the frost layer from falling off due to strong fan blowing, which affects the heat exchanger performance. At this time, the fan speed of the outdoor heat exchanger 6 may be reduced to about 400-600 rpm. Due to the reduction in refrigerant flowing to the indoor heat exchanger 5, the heating capacity of the indoor heat exchanger 5 is reduced. In order to prevent the indoor temperature from dropping too quickly, the fan speed of the indoor heat exchanger 5 can be appropriately reduced to reduce indoor heat loss. The fan speed of the indoor heat exchanger 5 is reduced to 60%-70% of the maximum operating speed. For example, if the maximum operating speed is 1200 rpm, it can be adjusted to 720-840 rpm.

[0049] Furthermore, in the defrosting step, when frosting is severe, the openings of the main electronic expansion valve 11 and the auxiliary electronic expansion valve 12 are adjusted so that the flow ratio of the refrigerant to the outdoor heat exchanger 6 and the indoor heat exchanger 5 is a third ratio.

[0050] It should be noted that the specific values ​​of the first ratio, the second ratio and the third ratio can be set by technical personnel in this field according to design requirements. In an embodiment of the present invention, the first ratio is that the flow ratio of the refrigerant flowing to the outdoor heat exchanger 6 and the indoor heat exchanger 5 is 3:7, the second ratio is that the flow ratio of the refrigerant flowing to the outdoor heat exchanger 6 and the indoor heat exchanger 5 is 7:3, and the third ratio is that the flow ratio of the refrigerant flowing to the outdoor heat exchanger 6 and the indoor heat exchanger 5 is 9:1.

[0051] Furthermore, in the defrosting step when there is heavy frost, the fans of the indoor heat exchanger 5 and the outdoor heat exchanger 6 are stopped.

[0052] Similarly, in some embodiments of the present invention, when frosting is severe, the opening of the main electronic expansion valve 11 will be opened to a greater extent, and the opening of the auxiliary electronic expansion valve 12 will be reduced accordingly.

[0053] In some embodiments, the maximum opening of the main electronic expansion valve 11 and the auxiliary electronic expansion valve 12 is 400 steps. In this case, the opening of the main electronic expansion valve 11 is adjusted to between 280 and 320 steps, and the opening of the auxiliary electronic expansion valve 12 is adjusted to between 50 and 80 steps. This is because the frost layer is already very serious and requires a large amount of refrigerant heat to melt the frost layer, maximizing the use of the high-temperature refrigerant discharged by the compressor 1 for defrosting.

[0054] Furthermore, when there is heavy frost, the fan of the outdoor heat exchanger 6 stops running because all the refrigerant is used to defrost the outdoor heat exchanger 6, and the frost layer is very thick. The rotation of the fan may interfere with the defrosting process or cause the frost layer to fall and damage the heat exchanger and other components. Turning off the fan of the outdoor heat exchanger 6 allows the high-temperature refrigerant to better concentrate heat to melt the frost layer. Due to the action of the double heat exchange tube heat accumulator 7, the defrosting process can be completed quickly. The indoor temperature has not had time to drop significantly before the defrosting is over. The change in indoor temperature is relatively small, so the fan of the indoor heat exchanger 5 can be turned off.

[0055] After the final defrost is completed, the heating operation mode is restored.

[0056] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0057] Of course, the present invention is not limited to the above-mentioned embodiments. Those skilled in the art may make equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A heat pump thermal storage defrost control method, characterized in that: The following steps are involved: Outdoor temperature collection: After turning on the heating, the surface temperature of the outdoor heat exchanger is collected regularly to obtain a series of temperature values. The defrost temperature of the outdoor heat exchanger surface is set as T0. Calculate temperature deviation: Set the temperature data of each sampling as Tn (n=1, 2, 3...), calculate the temperature difference of each sampling △Tn=Tn-T0, sampling frequency △t / time; Calculate the temperature change rate: For the data collected at two adjacent information collection moments, calculate the real-time temperature change rate based on the collection rate; Frost degree judgment: The frost degree is divided into light frost, moderate frost or heavy frost according to the temperature difference and the temperature change rate; Defrost: According to the degree of frost, different strategies are used to adjust the opening of the main electronic expansion valve and the auxiliary electronic expansion valve, and refrigerant is called into the outdoor heat exchanger for defrosting.

2. A heat pump thermal storage defrosting control method according to claim 1, characterized in that: In the step of calculating the temperature change rate, set the temperature change rate -D, where A and D are constant coefficients.

3. A heat pump thermal storage defrosting control method according to claim 2, characterized in that: In the frost degree determination step, when ΔTn is within the first temperature difference interval, kn is within the first temperature change rate interval, and both the temperature difference ΔTn and the temperature change rate kn are within this interval during the X1 period, the frost degree is determined to be light frost; When ΔTn is in the second temperature difference interval, kn is in the second temperature change rate interval, and both the temperature difference ΔTn and the temperature change rate kn are within this interval during the X2 period, the degree of frost is determined to be moderate frost; When ΔTn is in the third temperature difference interval, kn is in the third temperature change rate interval, and the temperature difference ΔTn and the temperature change rate kn remain within this range for more than X3 time, the frosting degree is determined to be severe frosting.

4. A heat pump thermal storage defrosting control method according to claim 3, characterized in that: In the defrosting step, when there is light frost, the openings of the main electronic expansion valve and the auxiliary electronic expansion valve are adjusted so that the flow ratio of the refrigerant to the outdoor heat exchanger and the indoor heat exchanger is a first ratio.

5. A heat pump thermal storage defrosting control method according to claim 4, characterized in that: During the defrost step when there is light frost, the speed of the fan of the indoor heat exchanger is simultaneously reduced.

6. A heat pump thermal storage defrosting control method according to claim 3, characterized in that: In the defrosting step, when the frost is moderate, the openings of the main electronic expansion valve and the auxiliary electronic expansion valve are adjusted so that the flow ratio of the refrigerant to the outdoor heat exchanger and the indoor heat exchanger is a second ratio.

7. A heat pump thermal storage defrosting control method according to claim 6, characterized in that: During the defrost step at moderate frost, the speed of the indoor heat exchanger fan is simultaneously reduced.

8. The heat pump thermal storage defrosting control method according to claim 3, characterized in that: In the defrosting step, when frosting is severe, the openings of the main electronic expansion valve and the auxiliary electronic expansion valve are adjusted so that the flow ratio of the refrigerant to the outdoor heat exchanger and the indoor heat exchanger is a third ratio.

9. A heat pump thermal storage defrosting control method according to claim 8, characterized in that: During the defrost step in case of heavy frost, the fans of the outdoor heat exchanger and the indoor heat exchanger are stopped.

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