A heat pump air conditioner with constant temperature and dehumidification control

Abstract

The present invention relates to a heat pump air conditioner with constant temperature dehumidification control, the system comprises a first refrigerant circulation system, a second refrigerant circulation system, an air duct unit, a temperature and humidity detection unit and a controller, the air duct unit is sequentially provided with a fan, an evaporator of the first refrigerant circulation system and a condenser of the second refrigerant circulation system along the direction from the air outlet to the return air outlet, the controller is electrically and / or communicatively connected with the fan, the first refrigerant circulation system, the second refrigerant circulation system and the temperature and humidity detection unit; the controller adopts a joint control mode combining the temperature fluctuation range and the humidity fluctuation range, and adopts a joint control mode combining the temperature drop rate and the humidity change rate under high temperature and high humidity, can accurately adjust the temperature and humidity and improve the adjustment speed, can provide users with a more comfortable indoor environment, improve the user's temperature control and dehumidification experience, and save energy and reduce consumption at the same time.

Description

Technical Field

[0001] The invention relates to the control field of heat pump air conditioners, and in particular to a heat pump air conditioner with constant temperature dehumidification control. Background Art

[0002] With the development of biopharmaceuticals, high-end food, and electronics industries, people have higher and higher requirements for the refrigeration technology effects in their production links. The traditional constant temperature dehumidification air conditioning unit can no longer meet the high production requirements for the control of clean environment temperature and humidity, and there is an urgent need for air conditioning units with more precise constant temperature dehumidification control.

[0003] Conventional constant temperature dehumidification air conditioners process air and then dehumidify it through an evaporator before reheating it. The reheat source is usually a hot water coil, steam coil, electric heating, etc. with high energy consumption. At the same time, the existing indoor temperature conditions are used as the judgment standard, and three operating modes are set according to the indoor temperature. This solution of independently controlling the indoor absolute humidity value and temperature value during the dehumidification control process, although it solves the user's feeling of coldness in the dehumidification mode, does not consider the mutual influence of temperature and other factors and humidity on the user's body perception, that is, the user's body perception of humidity is not the same as the absolute humidity of the indoor air. Since the temperature compensation in the constant temperature dehumidification mode cannot completely prevent the indoor temperature from changing, the appropriate indoor relative humidity value during the entire constant temperature dehumidification process will also change. Dehumidification control is performed blindly for a set absolute humidity value, which leads to technical problems such as affecting production during the dehumidification process and even too long dehumidification time. Summary of the invention

[0004] Based on this, an object of the present invention is to provide a heat pump air conditioner with constant temperature dehumidification control.

[0005] A heat pump air conditioner with constant temperature dehumidification control, comprising a first refrigerant circulation system, a second refrigerant circulation system, and an air duct unit, wherein the first refrigerant circulation system comprises a first compressor, a first heat exchanger, a first electronic expansion valve, and a second heat exchanger connected in sequence through a refrigerant pipeline, and the second refrigerant circulation system comprises a second compressor, a third heat exchanger, a second electronic expansion valve, and a fourth heat exchanger connected in sequence through a refrigerant pipeline, the air duct unit is sequentially provided with a fan, a second heat exchanger, and a third heat exchanger along the direction from the air outlet to the return air outlet, and further comprises a temperature and humidity detection unit and a controller, wherein the controller is electrically and / or communicatively connected to the fan, the first refrigerant circulation system, the second refrigerant circulation system, and the temperature and humidity detection unit, and is characterized in that the controller performs constant temperature dehumidification control of the heat pump system in the following manner:

[0006] Get the constant temperature dehumidification instruction and start the fan;

[0007] Get the current indoor temperature and indoor relative humidity RHt :

[0008] If the indoor temperature Less than the set lower limit of the temperature fluctuation range And the indoor relative humidity RH t Greater than the set upper limit of the humidity fluctuation range RH target +ΔRH, start the second refrigerant circulation system to make the third heat exchanger operate as a condenser at a low frequency to heat for the first time period t1;

[0009] If the indoor temperature The allowed fluctuation range of the set temperature And the indoor relative humidity RH t Greater than the set upper limit of the humidity fluctuation range RH target +ΔRH, start the second refrigerant circulation system to make the third heat exchanger work as a condenser and operate at a low frequency to heat for the second time period t2, and continue to obtain the indoor temperature at the next moment If the indoor temperature at the next moment Greater than the upper limit of the allowable temperature fluctuation range Start the first refrigerant circulation system to make the second heat exchanger operate as an evaporator at a low frequency for a third time period t3;

[0010] If the indoor temperature Greater than the upper limit of the set temperature fluctuation range Start the first refrigerant circulation system to make the second heat exchanger operate as an evaporator for cooling, and obtain the real-time indoor temperature And calculate the temperature drop rate ΔT in , according to the temperature drop rate ΔT in Control the frequency of the first compressor until the real-time indoor temperature T i i n Within the allowable temperature fluctuation range If the indoor relative humidity RH t Greater than the set upper limit of the humidity fluctuation range RH target +ΔRH, start the second refrigerant circulation system to make the third heat exchanger operate as a condenser at a low frequency for heating, and obtain the real-time indoor relative humidity RH j And calculate the humidity change rate ΔRH, according to the real-time indoor relative humidity RH j and humidity change rate ΔRH to control the frequency of the second compressor until the real-time indoor relative humidity RH j In the humidity allowable fluctuation range [RH target ±ΔRH];

[0011] in, Indicates the set temperature threshold, ΔT indicates the set temperature allowable fluctuation value; RH targetIt indicates the set humidity threshold, and ΔRH indicates the set allowable humidity fluctuation value.

[0012] Furthermore, if the indoor temperature Less than the set lower limit of the temperature fluctuation range Perform the following control steps:

[0013] S30 obtains the current indoor relative humidity RH t :

[0014] If the current indoor relative humidity RH t Greater than the set upper limit of the humidity fluctuation range RH target +ΔRH, start the second refrigerant circulation system to make the third heat exchanger work as a condenser and operate at a low frequency to heat for the first time period t1, and continue to obtain the indoor temperature at the next moment

[0015] If the current indoor relative humidity RH t Within the set humidity allowable fluctuation range [RH target ±ΔRH], maintain the current operating status of the first refrigerant circulation system and the second refrigerant circulation system, and continuously obtain the indoor temperature at the next moment This control method makes it inappropriate to continue cooling and dehumidifying to reduce the water vapor content in the air when the indoor temperature is low. Instead, it adopts the method of heating the circulating air to reduce the relative humidity of the circulating air, so as to keep the indoor temperature and humidity at a state with better user experience.

[0016] Furthermore, if the indoor temperature The allowed fluctuation range of the set temperature Perform the following control steps:

[0017] S40 obtains the current indoor relative humidity RH t :

[0018] If the current indoor relative humidity RH t Greater than the set upper limit of the humidity fluctuation range RH target +ΔRH, start the second refrigerant circulation system to make the third heat exchanger work as a condenser and operate at a low frequency to heat for the second time period t2, and continue to obtain the indoor temperature at the next moment

[0019] If the indoor temperature at the next moment Greater than the upper limit of the allowable temperature fluctuation range Start the first refrigerant circulation system to make the second heat exchanger operate as an evaporator at a low frequency for the third time period t3, and continue to obtain the indoor temperature at the next time.

[0020] If the indoor temperature at the next moment The allowed fluctuation range of the set temperature Control the second refrigerant circulation system to maintain the current load and continuously obtain the indoor temperature at the next moment

[0021] If the current indoor relative humidity RH t Within the set humidity allowable fluctuation range [RH target ±ΔRH], control the first refrigerant circulation system and the second refrigerant circulation system to maintain the current operating state, and continuously obtain the indoor temperature at the next moment This control method first heats the circulating air to reduce the relative humidity of the circulating air, and then monitors the temperature on this basis. If the temperature rises, it will be cooled to keep the indoor temperature and humidity at a state that provides better user experience.

[0022] Furthermore, if the indoor temperature Greater than the upper limit of the set temperature fluctuation range Perform the following control steps:

[0023] S50 starts the first refrigerant circulation system to make the second heat exchanger operate as an evaporator to cool and obtain the real-time indoor temperature And calculate the temperature drop rate ΔT in :

[0024] If the temperature drop rate ΔT in Greater than or equal to the first temperature change threshold Control the first compressor to reduce the frequency by one gear and continuously monitor the temperature drop rate ΔT in ;

[0025] If the temperature drop rate ΔT in Less than the first temperature change threshold and is greater than the second temperature change threshold Control the first compressor to maintain the current frequency operation, and execute step S60;

[0026] If the temperature drop rate ΔT in Less than or equal to the second temperature change threshold Control the first compressor to run at the first gear and continuously monitor the temperature drop rate ΔT in ;

[0027] S60 obtains the current indoor relative humidity RH t :

[0028] If the current indoor relative humidity RH t Greater than the set upper limit of the humidity fluctuation range RH target +ΔRH, then get the real-time indoor temperature The rate of decrease ΔT in And control the first compressor to follow the temperature drop rate ΔT described in S50 in Adjust the temperature and start the second refrigerant circulation system to make the third heat exchanger operate as a condenser at a low frequency to heat the room and obtain the real-time indoor relative humidity RH j And calculate the humidity change rate ΔRH:

[0029] Such as real-time indoor relative humidity RH j Less than the lower limit of the humidity fluctuation range RH target -ΔRH, control the second compressor to reduce the frequency by one gear and continuously obtain the real-time indoor relative humidity RH j ;

[0030] Such as real-time indoor relative humidity RH j Greater than or equal to the lower limit of the humidity fluctuation range RH target -ΔRH and less than or equal to the set humidity threshold RH target , and the humidity change rate ΔRH is less than or equal to the humidity change threshold ΔRH target , control the second refrigerant circulation system to maintain the current load;

[0031] Such as real-time indoor relative humidity RH j Greater than the set humidity threshold RH target , and the humidity change rate ΔRH is less than or equal to the humidity change threshold ΔRH target , control the second compressor to run at the first gear, and continuously obtain the real-time indoor relative humidity RH j ;

[0032] Such as real-time indoor relative humidity RH j Greater than the set humidity threshold RH target , and the humidity change rate ΔRH is greater than the humidity change threshold ΔRH target , control the second refrigerant circulation system to maintain the current load;

[0033] If the current indoor relative humidity RH t Within the set humidity allowable fluctuation range [RH target ±ΔRH], maintaining the current operating status of the first refrigerant circulation system and the second refrigerant circulation system.

[0034] Compared with the prior art, the heat pump air conditioner with constant temperature dehumidification control of the present invention has the following beneficial technical effects:

[0035] 1) By adopting two sets of independently controlled refrigerant circulation systems, a joint control method of first controlling temperature and then controlling relative humidity is adopted, which can accurately adjust the temperature and humidity and improve the adjustment speed, and can provide users with a more accurate indoor temperature and humidity environment, so that the production environment meets production needs, while saving energy and reducing consumption;

[0036] 1) By adopting the joint control method of temperature fluctuation range and humidity fluctuation range, it can effectively avoid the frequent switching of heat pump air conditioner under critical state caused by separate control, which may accelerate the damage of heat pump air conditioner and extend the service life of heat pump air conditioner;

[0037] 2) By adopting a joint control method that combines the temperature drop rate and the humidity change rate, the system can quickly and accurately adjust the room temperature to the appropriate temperature and humidity under high temperature and high humidity conditions, thereby improving the user's temperature control and dehumidification experience.

[0038] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram of the system structure of an embodiment of the present invention;

[0040] Figure 2 A schematic diagram of a control method flow chart of an embodiment of the present invention;

[0041] Figure 3 Schematic diagram of temperature and humidity control curve of an example of the present invention. DETAILED DESCRIPTION

[0042] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention.

[0043] In order to solve the problem that when dehumidification is performed by temperature superimposed on moisture content control during cooling in the prior art, the dehumidification effect is not significant when the indoor temperature is low, and the user's temperature and humidity control experience is poor; after research and debugging, the present invention proposes a heat pump air conditioner with constant temperature dehumidification control, the heat pump air conditioner has two separately controlled heat exchangers on the air supply channel, one heat exchanger for cooling and the other heat exchanger for heating. Based on this setting, the heat pump air conditioner includes a constant temperature dehumidification control method, which includes: when the indoor temperature is lower than the set temperature fluctuation limit, the circulating air is first heated to reduce the relative humidity, and on this basis Then, by monitoring the temperature, the cooling is turned on to offset the temperature rise caused by heating; when the indoor temperature is higher than the set temperature fluctuation limit, the circulating air is first cooled and condensed and dehumidified to make the temperature of the circulating air reach the set temperature fluctuation limit. On this basis, the relationship between the relative humidity and the set humidity fluctuation limit is used to control whether to turn on the heating to further reduce the relative humidity of the circulating air. On this basis, the real-time temperature changes, real-time relative humidity and real-time relative humidity changes are monitored to control the frequency of the refrigeration compressor and the heating compressor to make the indoor temperature and relative humidity within the range set by the user.

[0044] This control method can accurately adjust the temperature and humidity and improve the adjustment speed, so as to provide users with a more comfortable indoor environment and save energy and reduce consumption; at the same time, by adopting a joint control method combining the temperature fluctuation range and the humidity fluctuation range, it can effectively avoid the frequent switching of the heat pump air conditioner in a critical state due to separate control, thereby accelerating the damage of the heat pump air conditioner and extending the service life of the heat pump air conditioner.

[0045] For specific implementation, please refer to Figure 1 The heat pump air conditioner with constant temperature dehumidification control proposed in the present invention includes a first refrigerant circulation system 10, a second refrigerant circulation system 20, an air duct unit 30, a temperature and humidity detection unit 40 and a controller (not shown in the figure), and the controller is electrically and / or communicatively connected to the first refrigerant circulation system 10, the second refrigerant circulation system 20, the air duct unit 30 and the temperature and humidity detection unit 40.

[0046] The first refrigerant circulation system 10 includes a first compressor 11, a first heat exchanger 12, a first electronic expansion valve 13, a second heat exchanger 14 and a first gas-liquid separator 15 which are sequentially connected through a refrigerant pipeline. In the first refrigerant circulation system 10, the first heat exchanger 12 serves as a condenser and the second heat exchanger 14 serves as an evaporator.

[0047] The second refrigerant circulation system 20 includes a second compressor 21, a third heat exchanger 22, a second electronic expansion valve 23, a fourth heat exchanger 24 and a second gas-liquid separator 25 which are circulated and connected through a refrigerant pipeline. In the second refrigerant circulation system 20, the third heat exchanger 22 serves as a condenser and the fourth heat exchanger 24 serves as an evaporator.

[0048] The air duct unit 30 includes an air duct housing, one end of which has an indoor air outlet A, and the other end opposite to the indoor air supply port has an indoor return air port B. In the air duct housing, on the air flow path from the indoor return air port B to the indoor air outlet A, the third heat exchanger 22, the second heat exchanger 14 and the fan 31 are sequentially arranged, wherein the second heat exchanger 14 and the third heat exchanger 22 are spaced a certain distance apart. The fan 31 is electrically connected and / or communicatively connected to the controller.

[0049] The temperature and humidity detection unit 40 is arranged indoors and is used to obtain indoor temperature signals and humidity signals.

[0050] The controller receives the temperature signal and humidity signal collected by the temperature and humidity detection unit 40 , and controls the fan 31 , the first refrigerant circulation system 10 , and the second refrigerant circulation system 20 according to the stored calculation and judgment program.

[0051] For details, please refer to Figure 2 The control method of the heat pump air conditioner with constant temperature dehumidification control of the present invention includes the following steps.

[0052] S10 obtains the constant temperature dehumidification instruction and starts the air blower;

[0053] S20 obtains the current indoor temperature

[0054] If the indoor temperature Less than the set lower limit of the temperature fluctuation range Right now Then execute step S30;

[0055] If the indoor temperature The allowed fluctuation range of the set temperature Right now Then execute step S40;

[0056] If the indoor temperature Greater than the upper limit of the set temperature fluctuation range Right now Then execute step S50;

[0057] in, It indicates the set temperature threshold, and ΔT indicates the set temperature allowable fluctuation value.

[0058] The setting range of the allowable temperature fluctuation value ΔT is 0.5°C to 1.0°C.

[0059] S30 obtains the current indoor relative humidity RH t :

[0060] If the current indoor relative humidity RH t Greater than the set upper limit of the humidity fluctuation range RH target +ΔRH, RH t >RH target +ΔRH, start the second refrigerant circulation system to make the third heat exchanger work as a condenser and operate at a low frequency to heat for the first time period t1, and continue to obtain the indoor temperature at the next moment Execute step S20;

[0061] If the current indoor relative humidity RH t Within the set humidity allowable fluctuation range [RH target ±ΔRH], i.e. RH t ∈[RH target ±ΔRH], maintain the current operating status of the first refrigerant circulation system and the second refrigerant circulation system, and continuously obtain the indoor temperature at the next moment Execute step S20;

[0062] Among them, RH target It indicates the set humidity threshold, and ΔRH indicates the set allowable humidity fluctuation value.

[0063] The first time period t1 is set in a range of 4 minutes to 5 minutes.

[0064] The setting range of the humidity allowable fluctuation value ΔRH is 1-2.

[0065] S40 obtains the current indoor relative humidity RH t :

[0066] If the current indoor relative humidity RH t Greater than the set upper limit of the humidity fluctuation range RH target +ΔRH, RH t >RH target +ΔRH, start the second refrigerant circulation system to make the third heat exchanger work as a condenser and operate at a low frequency to heat for the second time period t2, and continue to obtain the indoor temperature at the next moment

[0067] If the indoor temperature at the next moment Greater than the upper limit of the allowable temperature fluctuation range Right now Start the first refrigerant circulation system to make the second heat exchanger operate as an evaporator at a low frequency for the third time period t3, and continue to obtain the indoor temperature at the next time. Execute step S20;

[0068] If the indoor temperature at the next moment The allowed fluctuation range of the set temperature Control the second refrigerant circulation system to maintain the current load and continuously obtain the indoor temperature at the next moment Execute step S20;

[0069] If the current indoor relative humidity RH t Within the set humidity allowable fluctuation range [RH target ±ΔRH], i.e. RH t ∈[RH target ±ΔRH], control the first refrigerant circulation system and the second refrigerant circulation system to maintain the current operating state, and continuously obtain the indoor temperature at the next moment Execute step S20;

[0070] The second time period t2 is set in a range of 4 minutes to 5 minutes.

[0071] The third time period t3 is set in the range of 4 minutes to 5 minutes.

[0072] S50 starts the first refrigerant circulation system to make the second heat exchanger operate as an evaporator to cool the room and obtain the indoor temperature in real time And calculate the temperature drop rate ΔT in :

[0073] If the temperature drop rate ΔT in Greater than or equal to the first temperature change threshold Control the first compressor to reduce the frequency by one gear and continuously monitor the temperature drop rate ΔT in ;

[0074] If the temperature drop rate ΔT in Less than the first temperature change threshold and is greater than the second temperature change threshold Control the first compressor to maintain the current frequency operation, and execute step S60;

[0075] If the temperature drop rate ΔT in Less than or equal to the second temperature change threshold Control the first compressor to run at the first gear and continuously monitor the temperature drop rate ΔT in ;

[0076] Among them, the temperature drop rate ΔT in satisfy:

[0077]

[0078] Where: is the indoor temperature data recorded for the i-th time.

[0079] The first temperature change threshold Set to 2°C / min.

[0080] The second temperature change threshold Set to 0℃ / min.

[0081] S60 obtains the current indoor relative humidity RH t :

[0082] If the current indoor relative humidity RH t Greater than the set upper limit of the humidity fluctuation range RH target +ΔRH, RH t >RH target +ΔRH, then get the indoor temperature in real time The rate of decrease ΔT in And control the first compressor to follow the temperature drop rate ΔT described in S50 in Adjust the temperature and start the second refrigerant circulation system to make the third heat exchanger operate as a condenser at a low frequency to heat the room and obtain the real-time indoor relative humidity RH j And calculate the humidity change rate ΔRH:

[0083] Such as real-time indoor relative humidity RH j Less than the lower limit of the humidity fluctuation range RH target -ΔRH, control the second compressor to reduce the frequency by one gear and continuously obtain the real-time indoor relative humidity RH j ;

[0084] Such as real-time indoor relative humidity RH j Greater than or equal to the lower limit of the humidity fluctuation range RH target -ΔRH and less than or equal to the set humidity threshold RH target , and the humidity change rate ΔRH is less than or equal to the humidity change threshold ΔRH target , control the second refrigerant circulation system to maintain the current load;

[0085] Such as real-time indoor relative humidity RH j Greater than the set humidity threshold RH target , and the humidity change rate ΔRH is less than or equal to the humidity change threshold ΔRH target , control the second compressor to run at the first gear, and continuously obtain the real-time indoor relative humidity RH j ;

[0086] Such as real-time indoor relative humidity RH j Greater than the set humidity threshold RH target , and the humidity change rate ΔRH is greater than the humidity change threshold ΔRH target , control the second refrigerant circulation system to maintain the current load;

[0087] If the current indoor relative humidity RH tWithin the set humidity allowable fluctuation range [RH target ±ΔRH], maintaining the current operating status of the first refrigerant circulation system and the second refrigerant circulation system;

[0088] The humidity change rate ΔRH satisfies:

[0089] ΔRH=RH j+1 -RH j

[0090] In the formula, RH j is the indoor relative humidity data recorded for the jth time.

[0091] The humidity change threshold ΔRH target is 0 / min.

[0092] Application Examples

[0093] Example 1

[0094] A manufacturer of medicinal hard capsules encountered a problem in which the moisture content of the capsules encapsulating the drugs was higher than 15% due to high air humidity and poor dehumidification effect during the rainy weather. This caused moisture to enter the drugs and affect the quality and efficacy of the drugs.

[0095] Based on the original equipment, the constant temperature dehumidification control method of the present application was adopted to upgrade and transform the equipment, so that the humidity control accuracy of the production workshop of the manufacturer was improved from 2% to 0.5%, and the number of products with a moisture content of more than 15% in the same season was reduced by 80%, as shown in Table 1 and Figure 3 .

[0096] Table 1

[0097]

[0098] Example 2

[0099] For a certain plant soft capsule skin manufacturer, if the humidity in the production workshop is too high, it will cause problems such as capsule skin adhesion and leakage.

[0100] After upgrading and renovating the temperature and humidity control equipment of the manufacturer and adopting the constant temperature dehumidification control method of the present application, the humidity control accuracy was stabilized at 1%, the response time was 2 minutes, the product stability was improved, and the defective products were reduced by 78%.

[0101] According to the above application examples, the heat pump air conditioner with constant temperature and dehumidification control of the present invention:

[0102] 1) By adopting two sets of independently controlled refrigerant circulation systems, a joint control method of first controlling temperature and then controlling relative humidity is adopted, which can accurately adjust the temperature and humidity and improve the adjustment speed, and can provide users with a more accurate indoor temperature and humidity environment, so that the production environment meets production needs, while saving energy and reducing consumption;

[0103] 2) By adopting the joint control method of temperature fluctuation range and humidity fluctuation range, it can effectively avoid the frequent switching of heat pump air conditioner under critical state caused by separate control, which may accelerate the damage of heat pump air conditioner and extend the service life of heat pump air conditioner;

[0104] 3) By adopting a joint control method that combines the temperature drop rate and the humidity change rate, the system can quickly and accurately adjust the room temperature to the appropriate temperature and humidity under high temperature and high humidity conditions, thereby improving the user's temperature control and dehumidification experience.

[0105] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the embodiments of the present application. The singular forms of "a", "said" and "the" used in the embodiments of the present application and the claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that, unless otherwise specified, "multiple" 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 only used to distinguish, rather than to describe a specific order or sequence, and cannot be understood as indicating or implying relative importance. When the above description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. In the description of the present application, for those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0106] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and the present invention is also intended to include these modifications and modifications.

Claims

1. A heat pump air conditioner with constant temperature dehumidification control, comprising a first refrigerant circulation system, a second refrigerant circulation system, and an air duct unit, wherein the first refrigerant circulation system comprises a first compressor, a first heat exchanger, a first electronic expansion valve, and a second heat exchanger connected in sequence through a refrigerant pipeline, and the second refrigerant circulation system comprises a second compressor, a third heat exchanger, a second electronic expansion valve, and a fourth heat exchanger connected in sequence through a refrigerant pipeline, and the air duct unit is provided with a fan, a second heat exchanger, and a third heat exchanger in sequence from an air outlet to a return air outlet, and further comprises a temperature and humidity detection unit and a controller, wherein the controller is electrically and / or communicatively connected to the fan, the first refrigerant circulation system, the second refrigerant circulation system, and the temperature and humidity detection unit, and is characterized in that: The controller performs constant temperature dehumidification control of the heat pump system in the following manner: Get the constant temperature dehumidification instruction and start the fan; Get the current indoor temperature and indoor relative humidity RH t : If the indoor temperature Less than the set lower limit of the temperature fluctuation range And the indoor relative humidity RH t Greater than the upper limit of the humidity fluctuation range RH target +ΔRH, start the second refrigerant circulation system to make the third heat exchanger operate as a condenser at a low frequency to heat for the first time period t1; If the indoor temperature The allowed fluctuation range of the set temperature And the indoor relative humidity RH t Greater than the upper limit of the humidity fluctuation range RH target +ΔRH, start the second refrigerant circulation system to make the third heat exchanger work as a condenser and operate at a low frequency to heat for the second time period t2, and continue to obtain the indoor temperature at the next moment If the indoor temperature at the next moment Greater than the upper limit of the allowable temperature fluctuation range Start the first refrigerant circulation system to make the second heat exchanger operate as an evaporator at a low frequency for a third time period t3; If the indoor temperature Greater than the upper limit of the set temperature fluctuation range Start the first refrigerant circulation system to make the second heat exchanger operate as an evaporator for cooling, and obtain the real-time indoor temperature And calculate the temperature drop rate ΔT in , according to the temperature drop rate ΔT in Control the frequency of the first compressor until the real-time indoor temperature Within the allowable temperature fluctuation range If the indoor relative humidity RH t Greater than the upper limit of the humidity fluctuation range RH target +ΔRH, start the second refrigerant circulation system to make the third heat exchanger operate as a condenser at a low frequency for heating, and obtain the real-time indoor relative humidity RH j And calculate the humidity change rate ΔRH, according to the real-time indoor relative humidity RH j and humidity change rate ΔRH to control the frequency of the second compressor until the real-time indoor relative humidity RH j In the humidity allowable fluctuation range [RH target ±ΔRH]; in, Indicates the set temperature threshold, ΔT indicates the set temperature allowable fluctuation value; RH target It indicates the set humidity threshold, and ΔRH indicates the set allowable humidity fluctuation value.

2. The heat pump air conditioner according to claim 1, characterized in that: If the indoor temperature Less than the set lower limit of the temperature fluctuation range Perform the following control steps: S30 obtains the current indoor relative humidity RH t : If the current indoor relative humidity RH t Greater than the upper limit of the humidity fluctuation range RH target +ΔRH, start the second refrigerant circulation system to make the third heat exchanger work as a condenser and operate at a low frequency to heat for the first time period t1, and continue to obtain the indoor temperature at the next moment If the current indoor relative humidity RH t Within the set humidity allowable fluctuation range [RH target ±ΔRH], maintain the current operating status of the first refrigerant circulation system and the second refrigerant circulation system, and continuously obtain the indoor temperature at the next moment 3. The heat pump air conditioner according to claim 2, characterized in that: If the indoor temperature The allowed fluctuation range of the set temperature Perform the following control steps: S40 obtains the current indoor relative humidity RH t : If the current indoor relative humidity RH t Greater than the upper limit of the humidity fluctuation range RH target +ΔRH, start the second refrigerant circulation system to make the third heat exchanger work as a condenser and operate at a low frequency to heat for the second time period t2, and continue to obtain the indoor temperature at the next moment If the indoor temperature at the next moment Greater than the upper limit of the allowable temperature fluctuation range Start the first refrigerant circulation system to make the second heat exchanger operate as an evaporator at a low frequency for the third time period t3, and continue to obtain the indoor temperature at the next time. If the indoor temperature at the next moment The allowed fluctuation range of the set temperature Control the second refrigerant circulation system to maintain the current load and continuously obtain the indoor temperature at the next moment If the current indoor relative humidity RH t Within the set humidity allowable fluctuation range [RH target ±ΔRH], control the first refrigerant circulation system and the second refrigerant circulation system to maintain the current operating state, and continuously obtain the indoor temperature at the next moment 4. The heat pump air conditioner according to any one of claims 1 to 3, characterized in that: If the indoor temperature Greater than the upper limit of the set temperature fluctuation range Perform the following control steps: S50 starts the first refrigerant circulation system to make the second heat exchanger operate as an evaporator to cool and obtain the real-time indoor temperature And calculate the temperature drop rate ΔT in : If the temperature drop rate ΔT in Greater than or equal to the first temperature change threshold ΔT1 target , control the first compressor to reduce the frequency by one gear and continuously monitor the temperature drop rate ΔT in ; If the temperature drop rate ΔT in Less than the first temperature change threshold ΔT1 target and is greater than the second temperature change threshold ΔT2 target , control the first compressor to maintain the current frequency operation, and execute step S60; If the temperature drop rate ΔT in Less than or equal to the second temperature change threshold ΔT2 target , control the first compressor to run at the first gear and continuously monitor the temperature drop rate ΔT in ; S60 obtains the current indoor relative humidity RH t : If the current indoor relative humidity RH t Greater than the upper limit of the humidity fluctuation range RH target +ΔRH, then get the real-time indoor temperature T i i n The rate of decrease ΔT in And control the first compressor to follow the temperature drop rate ΔT described in S50 in Adjust the temperature and start the second refrigerant circulation system to make the third heat exchanger operate as a condenser at a low frequency to heat the room and obtain the real-time indoor relative humidity RH j And calculate the humidity change rate ΔRH: Such as real-time indoor relative humidity RH j Less than the lower limit of the humidity fluctuation range RH target -ΔRH, control the second compressor to reduce the frequency by one gear and continuously obtain the real-time indoor relative humidity RH j ; Such as real-time indoor relative humidity RH j Greater than or equal to the lower limit of the humidity fluctuation range RH target -ΔRH and less than or equal to the set humidity threshold RH target , and the humidity change rate ΔRH is less than or equal to the humidity change threshold ΔRH target , control the second refrigerant circulation system to maintain the current load; Such as real-time indoor relative humidity RH j Greater than the set humidity threshold RH target , and the humidity change rate ΔRH is less than or equal to the humidity change threshold ΔRH target , control the second compressor to run at the first gear, and continuously obtain the real-time indoor relative humidity RH j ; Such as real-time indoor relative humidity RH j Greater than the set humidity threshold RH target , and the humidity change rate ΔRH is greater than the humidity change threshold ΔRH target , control the second refrigerant circulation system to maintain the current load; If the current indoor relative humidity RH t Within the set humidity allowable fluctuation range [RH target ±ΔRH], maintaining the current operating status of the first refrigerant circulation system and the second refrigerant circulation system.

5. The heat pump air conditioner according to claim 4, characterized in that: The temperature drop rate ΔT in satisfy: Where: is the real-time indoor temperature data recorded for the i-th time; The humidity change rate ΔRH satisfies: ΔRH=RH j+1 -RH j In the formula, RH j is the real-time indoor relative humidity data recorded for the jth time.

6. The heat pump air conditioner according to claim 5, characterized in that: The first temperature change threshold ΔT1 target Set to 2°C / min; the second temperature change threshold ΔT2 target Set to 0℃ / min.

7. The heat pump air conditioner according to any one of claims 1 to 3, characterized in that: The setting range of the allowable temperature fluctuation value ΔT is 0.5°C to 1.0°C; the setting range of the allowable humidity fluctuation value ΔRH is 1 to 2.

8. The heat pump air conditioner according to claim 7, characterized in that: The first time period t1 is set in a range of 4 minutes to 5 minutes; the second time period t2 is set in a range of 4 minutes to 5 minutes; and the third time period t3 is set in a range of 4 minutes to 5 minutes.

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