A control method and control system based on a double-tank variable frequency heat pump water heater

Abstract

The present application relates to heat pump water heater technical field, more particularly, it relates to a kind of control method and system based on double-belly variable frequency heat pump water heater, wherein control method includes the following steps: S1: set target water temperature T0;Respectively collect multiple points to detect current water temperature, wherein, including the current water temperature T1 in the middle of first inner container, the current water temperature T2 in the upper part of first inner container, the current water temperature T3 in the upper part of second inner container;Current environment temperature T4 is detected;S2: utilize the current water temperature of multiple points comprehensive calculation, the first inner container heat energy Q1 and double-belly heat energy total amount Q0 required from current water temperature to target water temperature T0 Heating;S3: according to the proportion K of first inner container heat energy Q1 and double-belly heat energy total amount Q0 Control first distribution valve and second distribution valve, until target water temperature T0 is reached.The control method based on double-belly variable frequency heat pump water heater of the present application can satisfy the balanced heating of water heater in different parts, make the supply amount of hot water keep adequate at any time, improve the experience of user in cold weather.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat pump water heaters, and more particularly to a control method and a control system for a double-tank variable-frequency heat pump water heater. BACKGROUND

[0002] The market commonly used heat pump water heaters are single-tank, and the hot water output rate is basically below 80%. The diameter of the single-tank is large, which is not very friendly for most market customers to install. The double-tank can be made thinner under the same capacity, and the hot water output rate is more than 10% higher than that of the single-tank. The traditional heat pump water heater has a condenser with an outer-wound coil single set of outer-wound heat exchanger. As long as the heat pump water heater is started, the high-temperature refrigerant after compression will preferentially heat the water in the upper part of the single-tank. When the customer actually uses it, after using water for many times, the temperature of the hot water in the upper part of the water tank is higher than the reasonable temperature (85℃), but the temperature of the hot water in the lower part is far from the target temperature. Moreover, the unit will trigger the high-pressure high-exhaust protection of the heat pump system, and cannot meet the balanced heating of the whole tank of hot water, resulting in insufficient hot water and poor experience, especially in cold weather, and the high-pressure ratio is more serious. SUMMARY

[0003] The present application aims to overcome the shortcomings of the prior art, and provides a control method for a double-tank variable-frequency heat pump water heater, which can meet the balanced heating of the water heater at different positions, keep the supply of hot water sufficient at all times, and improve the experience of users in cold weather.

[0004] To solve the above technical problems, the technical solution adopted by the present application is as follows:

[0005] The present application provides a control method for a double-tank variable-frequency heat pump water heater. The control method is applied to a double-tank variable-frequency heat pump water heater. The water heater comprises a first inner tank and a second inner tank arranged side by side. The first inner tank and the second inner tank are connected by a pipeline. A first heat exchange pipe is arranged on the outer side of the upper part of the first inner tank. A second heat exchange pipe is arranged on the outer side of the lower part of the first inner tank. A third heat exchange pipe is arranged on the second inner tank. The water heater further comprises a heat exchange source and a controller. The heat exchange source is in communication with the inlet and outlet of the first heat exchange pipe, the inlet and outlet of the second heat exchange pipe, and the inlet and outlet of the third heat exchange pipe. A first distribution valve is arranged at the communication position of the heat exchange source and the inlet of the first heat exchange pipe. A second distribution valve is arranged at the communication position of the heat exchange source and the inlet of the third heat exchange pipe. The first distribution valve and the second distribution valve are in communication connection with the controller. A cold water inlet is arranged at the lower part of the first inner tank. A hot water outlet is arranged at the upper part of the second inner tank.

[0006] The control method comprises the following steps:

[0007] S1: setting a target water temperature T0;

[0008] Collecting current water temperature at multiple points respectively, including current water temperature T1 of the middle part of the first inner container, current water temperature T2 of the upper part of the first inner container, and current water temperature T3 of the upper part of the second inner container;

[0009] Detecting current environment temperature T4;

[0010] S2: comprehensively calculating the first inner container heat energy Q1 and the total amount of double-container heat energy Q0 required for heating from the current water temperature to the target water temperature T0 by using the current water temperature at multiple points;

[0011] S3: controlling the first distribution valve and the second distribution valve according to the proportion K of the first inner container heat energy Q1 and the total amount of double-container heat energy Q0 until the target water temperature T0 is reached.

[0012] The application is a control method based on a double-container variable frequency heat pump water heater, wherein a first inner container and a second inner container are arranged in the double-container variable frequency heat pump water heater, the first inner container upper part can be heated by a first heat exchange pipe, the first inner container lower part can be heated by a second heat exchange pipe, and the second inner container can be heated by a third heat exchange pipe; the first inner container and the second inner container are communicated, water is heated in the first inner container and then enters the second inner container, and hot water is obtained from the second inner container when a user uses water; the application can meet the hot water demand of the user, the supply amount of hot water is kept sufficient at all times, and the heating of any part of the double container can be accurately controlled by the heat proportion of the double container during the heating process.

[0013] Further, the specific allocation mode of the first distribution valve and the second distribution valve in the step S3 is as follows:

[0014] If 1 >= K >= a1, the first distribution valve and the second distribution valve are closed;

[0015] If a1 >= K >= a2, the first distribution valve is opened and the second distribution valve is closed;

[0016] If a2 >= K >= a3, the first distribution valve and the second distribution valve are opened;

[0017] Wherein a1, a2, and a3 are all preset values, and 1 >= a1 >= a2 >= a3 >= 0.

[0018] Further, the calculation formula of the first inner container heat energy Q1 is as follows:

[0019] Q1 = C(L1 / 2)*(T4-((T1+T5) / 2+T2) / 2);

[0020] Wherein Q1 is the first inner container heat energy, C is the specific heat capacity of water, L1 is the capacity of the first inner container, T1 is the current water temperature of the middle part of the first inner container, T2 is the current water temperature of the upper part of the first inner container, T4 is the current environment temperature, and T5 is the water inlet temperature.

[0021] Further, the calculation formula of the total heat energy Q0 of the double-tank is as follows:

[0022] Q0=C(L2 / 2)(T4-T3)+Q1;

[0023] Wherein Q0 is the total heat energy of the double-tank, C is the specific heat capacity of water, L2 is the volume of the second inner tank, T3 is the current water temperature of the upper part of the second inner tank, T4 is the current environment temperature, and Q1 is the heat energy of the first inner tank.

[0024] Further, the volume L1 of the first inner tank is equal to the volume L2 of the second inner tank.

[0025] Further, the step S2 and the step S3 further comprise a step Sa: calculating the running time t required for the water heater to reach the target water temperature T0 from the current water temperature, if t≥ preset time t 预设 , then entering the step S3, if t 预设 , then waiting for a certain time t 等待 and then entering the step S3, wherein

[0026] t 等待 =t 预设 -t.

[0027] Further, in the step Sa, the running time t is calculated according to the heating capacity q corresponding to the current environment temperature, and the specific formula is as follows:

[0028] t=Q0 / q.

[0029] Further, the preset time t 预设 is set according to the environment temperature.

[0030] Further, in the step Sa, the running frequency of the water heater is controlled according to the environment temperature T4 and the running time t.

[0031] The application also comprises a control system based on a double-tank variable frequency heat pump water heater, comprising a temperature monitoring module, a calculation module and a control module, wherein the temperature monitoring module is in communication connection with the calculation module, and the calculation module is in communication connection with the control module.

[0032] The temperature monitoring module is used for measuring the temperature of different parts of the first inner container and the second inner container. During the use of hot water, the temperature monitoring module comprises a plurality of water temperature measuring probes. The cross section of the water temperature measuring probe is small and perpendicular to the water flow direction, so the delay inertia of the test temperature is small, the real-time performance is stronger, and the double-tank system can arrange more effective temperature measuring points under the same water temperature probe spacing, and more accurately test the heat storage of the whole machine, and provide effective operation input data for accurate control of the unit. The calculation module is used for calculating the first inner container heat energy Q1 and the total double-tank heat energy Q0 required for heating from the current water temperature to the target water temperature T0. The control module is used for controlling the first distribution valve and the second distribution valve at the communication position of the heat exchange source and the first heat exchange pipe and the third heat exchange pipe, and controlling the proportion of the heat exchange medium supplied by the heat exchange source to the first heat exchange pipe and the second heat exchange pipe, so that the double-tank system can be accurately heated.

[0033] Compared with the prior art, the beneficial effects of the present application are:

[0034] The present application can realize high hot water output rate of double-tank, accurate heating of any one or upper and lower parts of one inner container of double-tank, confirmation of optimal operation strategy under any working condition, dynamic adjustment of machine start and stop time, avoidance of frequent start and stop of the unit, and realization of super-long service life of the unit. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of the double-tank variable frequency heat pump water heater of the present application.

[0036] Figure 2 It is a flow chart of the control method of the double-tank variable frequency heat pump water heater of the present application.

[0037] Figure 3 It is a structural block diagram of the control system of the double-tank variable frequency heat pump water heater of the present application.

[0038] The illustration marks are explained as follows:

[0039] 1, first inner container; 11, first heat exchange pipe; 12, second heat exchange pipe; 2, second inner container; 21, third heat exchange pipe; 3, pipe; 4, heat exchange source; 5, first distribution valve; 6, second distribution valve; 7, cold water inlet; 8, hot water outlet. DETAILED DESCRIPTION

[0040] The present application will be further described below in combination with specific embodiments. The drawings are only used for exemplary description, and the representation is only a schematic diagram, not a physical diagram, and cannot be understood as a limitation of the present patent; in order to better illustrate the embodiments of the present application, some components in the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some known structures and their descriptions in the drawings may be omitted.

[0041] In the description of the present application, it is to be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0042] In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second", etc. can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise explicitly specified and limited.

[0043] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0044] In the present application, unless otherwise explicitly specified and limited, the first feature "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature can be that the first feature is directly above or obliquely above the second feature, or it can only mean that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "under" and "under" the second feature can be that the first feature is directly below or obliquely below the second feature, or it can only mean that the horizontal height of the first feature is less than that of the second feature.

[0045] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0046] Embodiment 1

[0047] As Figure 2 The first embodiment of the control method of the double-tank variable frequency heat pump water heater based on the present application is shown, the control method is applied to the double-tank variable frequency heat pump water heater, as shown in Figure 1 The water heater includes a first inner tank 1 and a second inner tank 2 arranged side by side, the first inner tank 1 and the second inner tank 2 are communicated through a pipeline 3, a first heat exchange pipe 11 is arranged on the outer side of the upper part of the first inner tank 1, a second heat exchange pipe 12 is arranged on the outer side of the lower part of the first inner tank 1, and a third heat exchange pipe 21 is arranged around the second inner tank 2; The water heater further comprises a heat exchange source 4 and a controller, the heat exchange source 4 is communicated with the inlet and outlet of the first heat exchange pipe 11, the inlet and outlet of the second heat exchange pipe 12, and the inlet and outlet of the third heat exchange pipe 21 respectively, a first distribution valve 5 is arranged at the communication position of the heat exchange source 4 and the inlet of the first heat exchange pipe 11, a second distribution valve 6 is arranged at the communication position of the heat exchange source 4 and the inlet of the third heat exchange pipe 21, and the first distribution valve 5 and the second distribution valve 6 are both connected with the controller in communication; A cold water inlet 7 is arranged at the lower part of the first inner tank 1, and a hot water outlet 8 is arranged at the upper part of the second inner tank 2;

[0048] The control method comprises the following steps:

[0049] S1: setting a target water temperature T0; wherein the target water temperature T0 can be set according to the user's needs, such as 30℃-75℃, or more than 75℃;

[0050] Respectively collecting multiple points to detect the current water temperature, which includes the current water temperature T1 of the middle part of the first inner tank 1, the current water temperature T2 of the upper part of the first inner tank 1, and the current water temperature T3 of the upper part of the second inner tank 2; The temperature of different parts of the first inner tank 1 and the second inner tank 2 is detected by arranging multiple water temperature measuring probes in the first inner tank 1 and the second inner tank 2 respectively;

[0051] Detecting the current environment temperature T4; the current environment temperature T4 is detected by using an environment temperature sensing head;

[0052] S2: comprehensive calculation of the current water temperature by using multiple points, the first inner tank heat energy Q1 and the total amount of double tank heat energy Q0 required for heating from the current water temperature to the target water temperature T0;

[0053] The calculation formula of the first inner tank heat energy Q1 is as follows:

[0054] Q1=C(L1 / 2)*(T4-((T1+T5) / 2+T2) / 2);

[0055] Wherein, Q1 is the first inner tank heat energy, C is the specific heat capacity of water, L1 is the capacity of the first inner tank, T1 is the current water temperature in the middle of the first inner tank, T2 is the current water temperature in the upper part of the first inner tank, T4 is the current environment temperature, and T5 is the water inlet temperature; the specific heat capacity of water C is a constant, generally taken as 1.163 w·h / kg·℃; the water inlet temperature at different ambient temperatures is shown in Table 1;

[0056] Table 1

[0057] [T4 (°C)] (－∞，0] (0，5] (5，10] (10，15] (12，20] (20，25] (25，30] (30，35] (35，40] (40，∞] [T5 (°C)] 4 5 8 10 14 17 20 22 25 30

[0058] The calculation formula of the total amount of double tank heat energy Q0 is as follows:

[0059] Q0=C(L2 / 2)(T4-T3)+Q1;

[0060] Wherein, Q0 is the total amount of double tank heat energy, C is the specific heat capacity of water, L2 is the capacity of the second inner tank, T3 is the current water temperature in the upper part of the second inner tank, T4 is the current environment temperature, and Q1 is the first inner tank heat energy;

[0061] The water tank capacity will be different according to the different models of water heaters, such as 200\250\300\400\500\600 kg.

[0062] Sa: calculate the running time t required for the water heater to reach the target water temperature T0 from the current water temperature, if t≥preset time t 预设 , then enter step S3, if t 预设 , wait for a certain time t 等待 , and then enter step S3, wherein

[0063] t 等待 =t 预设 -t;

[0064] In step Sa, the running frequency of the water heater is controlled according to the environment temperature T4 and the running time t;

[0065] The optimal unit frequency control under different running time t and current environment temperature T4 is shown in Table 2;

[0066] Table 2

[0067]

[0068] The purpose of this step is to control the operating frequency of the water heater. While ensuring that the user's hot water demand is met, the start-stop interval of the water heater is dynamically adjusted so that the water heater does not need to be turned on frequently, which can extend the service life of the water heater to a certain extent.

[0069] In step Sa, the running time t is calculated based on the heating capacity q corresponding to the current ambient temperature T4, using the following formula:

[0070] t = Q0 / q;

[0071] Generally, the lower the current ambient temperature T4, the lower the heating capacity q;

[0072] Furthermore, the preset duration t in step Sa 预设 The preset duration t is set based on the current ambient temperature T4; the lower the current ambient temperature T4, the longer the preset duration t. 预设 The shorter the time. Current ambient temperature T4, heating capacity q, and preset duration t 预设 The values ​​are shown in Table 3;

[0073] Table 3

[0074]

[0075] The heating capacity has different values ​​at different ambient temperatures T4, and it gradually increases with increasing ambient temperature. 预设 The current ambient temperature T4 has different values, which are divided into t... 预设1 t 预设2 t 预设3 , t 预设 The value ranges from 3 to 15 minutes, following a gradually increasing pattern. Preferably, t... 预设1 For 5, t 预设2 For 10, t 预设3 It is 15.

[0076] S3: Control the first distribution valve and the second distribution valve according to the ratio K of the heat energy Q1 of the first inner tank and the total heat energy Q0 of the two tanks until the target water temperature T0 is reached;

[0077] The specific adjustment method of the first distribution valve 5 and the second distribution valve 6 is as follows:

[0078] If 1≥K≥a1, then close the first distribution valve 5 and the second distribution valve 6;

[0079] If a1≥K≥a2, then open the first distribution valve 5 and close the second distribution valve 6;

[0080] If a2≥K≥a3, then open the first distribution valve 5 and the second distribution valve 6;

[0081] wherein a1, a2, a3 are all preset values, and 1≥a1≥a2≥a3≥0, preferably, a1 is 0.8, a2 is 0.5, and a3 is 0.3.

[0082] The market commonly used heat pump water heater is single tank, and the hot water output rate is basically below 80%. The diameter of the single tank is large, and it is not very friendly for most market customers to install. The double tank can be made thinner under the condition of the same capacity, and the hot water output rate is more than 10% higher than that of the single tank. Meanwhile, in the process of using hot water, the water temperature measuring probe has a smaller cross section perpendicular to the water flow direction, and the delay inertia of testing temperature is small, and the real-time performance is stronger. In addition, the double tank system can arrange more effective temperature measuring points under the condition of the same water temperature probe spacing, and test the heat storage of the whole machine more accurately, so as to provide effective operation input data for accurate control of the heating part of the water heater.

[0083] The traditional heat pump water heater condenses the outer winding coil of the single group of outer winding heat exchangers (copper pipe or microchannel), and the high-temperature refrigerant after compression is preferentially heated to the upper water temperature of the single tank. In actual use, after multiple small water uses, the upper hot water temperature of the tank is higher than the reasonable temperature (85 DEG C), but the lower part is far from the target temperature, and the heat pump system protection of high pressure and high exhaust is triggered, so that the whole tank cannot be heated evenly, the hot water is not enough, and the experience is poor, especially in cold weather, and the high pressure ratio is more serious. The present application can accurately control the heating of any part of the double tank through the heat proportion of the double tank.

[0084] In the start-stop scheme of the traditional heat pump system control, due to the delay of single tank temperature measurement and the temperature difference control, the unit starts and stops, and the stability of the unit is poor, and there are many after-sales problems. The present application calculates the heat storage of the double tank respectively, and calculates the required heating time through the heating capacity q under the current environment temperature, and dynamically adjusts the start-stop interval of the unit through frequency control, and ensures that the double tank water tank is in full hot water state.

[0085] Embodiment 2

[0086] The following is a second embodiment of a control method of a double-tank variable frequency heat pump water heater.

[0087] The capacity of the first inner tank and the second inner tank is equal, which can optimize the occupied area.

[0088] Embodiment 3

[0089] As Figure 3The embodiment of the control system of the double-tank variable frequency heat pump water heater is shown, which comprises a temperature monitoring module, a calculation module and a control module.

[0090] The temperature monitoring module is used for measuring different parts of the first inner tank 1 and the second inner tank 2. In the process of using hot water, the temperature monitoring module comprises a plurality of water temperature measuring probes. The cross section of the water temperature measuring probe is small and perpendicular to the water flow direction, so the delay inertia of the test temperature is small, the real-time performance is stronger, and the double-tank system can arrange more effective temperature measuring points under the same water temperature probe spacing, and more accurately test the heat storage capacity of the whole machine, and provide effective operation input data for accurate control of the unit. The calculation module is used for calculating the first inner tank heat energy Q1 and the total double-tank heat energy Q0 required for heating from the current water temperature to the target water temperature T0. The control module is used for controlling the first distribution valve 5 and the second distribution valve 6 at the communication position of the heat exchange source 4 and the first heat exchange pipe 11 and the third heat exchange pipe 21, so that the double-tank system can be accurately heated by controlling the proportion of the heat exchange medium supplied by the heat exchange source 4 to the first heat exchange pipe 11 and the third heat exchange pipe 21.

[0091] Obviously, the above embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the embodiments of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. It is not necessary or possible to exhaust all the embodiments. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A control method for a dual-tank variable frequency heat pump water heater, characterized in that, The control method is applied to a double-tank variable frequency heat pump water heater. The water heater comprises a first inner tank and a second inner tank arranged side by side. The first inner tank and the second inner tank are communicated through a pipeline. A first heat exchange pipe is arranged around the upper outer side of the first inner tank. A second heat exchange pipe is arranged around the lower outer side of the first inner tank. A third heat exchange pipe is arranged around the second inner tank. The water heater further comprises a heat exchange source and a controller. The heat exchange source is communicated with the inlet and outlet of the first heat exchange pipe, the inlet and outlet of the second heat exchange pipe, and the inlet and outlet of the third heat exchange pipe, respectively. A first distribution valve is arranged at the communication position of the heat exchange source and the inlet of the first heat exchange pipe. A second distribution valve is arranged at the communication position of the heat exchange source and the inlet of the third heat exchange pipe. The first distribution valve and the second distribution valve are both communicated with the controller. A cold water inlet is arranged at the lower part of the first inner tank. A hot water outlet is arranged at the upper part of the second inner tank. The control method comprises the following steps: S1: setting a target water temperature T0; S2: collecting the current water temperatures of multiple points, including the current water temperature T1 of the middle part of the first inner tank, the current water temperature T2 of the upper part of the first inner tank, and the current water temperature T3 of the upper part of the second inner tank; S3: detecting the current environmental temperature T4; S4: comprehensively calculating the first inner tank heat energy Q1 and the total double-tank heat energy Q0 required for heating from the current water temperature to the target water temperature T0 by using the current water temperatures of multiple points; The calculation formula of the first inner tank heat energy Q1 is as follows: Q1=C(L1 / 2)*(T4-((T1+T5) / 2+T2) / 2) Wherein Q1 is the first inner tank heat energy, C is the specific heat capacity of water, L1 is the capacity of the first inner tank, T1 is the current water temperature T1 of the middle part of the first inner tank, T2 is the current water temperature of the upper part of the first inner tank, T4 is the current environmental temperature, and T5 is the water inlet temperature. The calculation formula of the total double-tank heat energy Q0 is as follows: Q0=C(L2 / 2)(T4-T3)+Q1 Wherein Q0 is the total double-tank heat energy, C is the specific heat capacity of water, L2 is the capacity of the second inner tank, T3 is the current water temperature of the upper part of the second inner tank, T4 is the current environmental temperature, and Q1 is the first inner tank heat energy. S5: controlling the first distribution valve and the second distribution valve according to the proportion K of the first inner tank heat energy Q1 and the total double-tank heat energy Q0 until the target water temperature T0 is reached. The specific allocation mode is as follows: If 1≥K≥a1, then close the first distribution valve and the second distribution valve. If a1≥K≥a2, then open the first distribution valve and close the second distribution valve. If a2≥K≥a3, then open the first distribution valve and the second distribution valve. Wherein a1, a2, and a3 are all preset values, and 1≥a1≥a2≥a3≥0.

2. The control method of the dual-evaporator variable-frequency heat pump water heater according to claim 1, characterized in that, The capacity L1 of the first inner tank is equal to the capacity L2 of the second inner tank.

3. The control method of the dual-evaporator variable-frequency heat pump water heater according to claim 1 or 2, characterized in that, Between step S2 and step S3, there is also step Sa: calculating the running time t required for the water heater to reach the target water temperature T0 from the current water temperature; if t ≥ preset time t 预设 Then proceed to step S3. If t < preset duration t 预设 Then wait for a certain time t 等待 Then proceed to step S3, in which... t 等待 = t 预设 - t.

4. The control method of the dual-evaporator variable-frequency heat pump water heater according to claim 3, characterized in that, In step Sa, the running time t is calculated according to the heating capacity q corresponding to the current environmental temperature, and the specific formula is as follows: t=Q0 / q.

5. The control method of the dual-evaporator variable-frequency heat pump water heater according to claim 3, characterized in that, The preset time length t in the step Sa 预设 Segmentation is set according to ambient temperature.

6. The control method of the dual-evaporator variable-frequency heat pump water heater according to claim 3, wherein, In step Sa, the running frequency of the water heater is controlled according to the environmental temperature T4 and the running time t.

7. A control system based on a dual-tank variable frequency heat pump water heater, characterized in that, The control system comprises a temperature monitoring module, a calculation module and a control module, the temperature monitoring module is in communication connection with the calculation module, and the calculation module is in communication connection with the control module.

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