Heat pump unit and control method of heat pump unit

Abstract

The invention relates to a heat pump unit and a control method of the heat pump unit. According to the heat pump unit and the control method of the heat pump unit, when it is detected that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is larger than the preset water temperature allowance Tpc, the compressor capacity of the first compressor and / or the second compressor is adjusted; and when the controller detects that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is smaller than or equal to the preset water temperature allowance Tpc, the controller adjusts the pressure ratio of the second compressor. Therefore, the first compressor and the second compressor in the heat pump unit can be of a design structure of independent decoupling of the rotating speed of the high-pressure stage and the rotating speed of the low-pressure stage, the specific rotating speed of the final stage (the high-pressure stage) is increased, and optimization of the compressor stage efficiency can be achieved.

Description

Technical Field

[0001] The present application relates to a heat pump unit and a control method for the heat pump unit. Background Art

[0002] As heat pump units, there are known single-stage compression systems and multi-stage compression systems. Among them, the single-stage compression system has a simple cycle and mature application, but the temperature rise is limited and it is difficult to meet the temperature rise requirements of industrial high-temperature heat pumps. On the other hand, the multi-stage compression system has a higher pressure ratio, which can achieve a higher temperature rise. However, between the multi-stage compressors, the impeller speed ratio of each stage is difficult to reasonably match, and the last stage impeller has a low speed ratio, a narrow flow channel, and low aerodynamic efficiency.

[0003] For example, in the case of a multi-stage compression system with dual compressors in series, since the suction volume of the compressor is proportional to the impeller speed, there is a strong coupling between the flow rate and the pressure ratio, and there are problems such as clogging and surge that are prone to occur. When dual compressors are connected in series, and multiple parameters such as temperature zone, flow rate, pressure ratio, speed, and air supply are coupled, the difficulty of efficient control of the system is further increased, and efficient coordinated control is difficult. There is still room for improvement in optimizing the efficiency of the compressor level. Summary of the invention

[0004] This application is made in view of the technical problems existing in the above-mentioned prior art. One purpose of this application is to provide a heat pump unit and a control method for the heat pump unit in which the high and low pressure stage speeds are independently decoupled and the final stage (high pressure stage) specific speed is increased, thereby achieving compressor stage efficiency optimization.

[0005] According to one solution of the present application, a heat pump unit is provided, comprising: an evaporator, a first compressor, a second compressor, a condenser, a flasher and a controller, wherein the evaporator, the first compressor, the second compressor and the condenser are connected in series, the first compressor is a compressor closer to the evaporator side than the second compressor, the second compressor is a compressor closer to the condenser side than the first compressor, the flasher is connected between the condenser and the evaporator, and the first compressor or the second compressor is supplemented with air through an air supply pipe. When the controller detects that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is greater than a preset water temperature tolerance Tpc, the controller adjusts the capacity of the first compressor and / or the second compressor, and when the controller detects that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to a preset water temperature tolerance Tpc, the controller adjusts the pressure ratio of the second compressor.

[0006] According to the above-mentioned heat pump unit of the present application, it can also be: the controller has a pipeline matching external closed-loop control mode and an efficiency optimization internal closed-loop control mode. In the pipeline matching external closed-loop control mode, the controller judges whether the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the water temperature tolerance Tpc. When the judgment result is affirmative, it switches to the efficiency optimization internal closed-loop control mode. When the judgment result is negative, the compressor capacity is adjusted. In the efficiency optimization internal closed-loop control mode, the controller adjusts the operating frequency F2 of the second compressor and / or the air supply pressure of the flasher according to the pre-obtained optimal operating frequency Fmap and anti-surge frequency Ffc.

[0007] According to the above-mentioned heat pump unit of the present application, it can also be: in the efficiency optimization internal closed-loop control mode, when the absolute value of the difference between the operating frequency F2 of the second compressor and the optimal operating frequency Fmap is greater than the first specified frequency deviation value, and the operating frequency F2 is less than the optimal operating frequency Fmap, the controller controls the second compressor to perform frequency loading of a predetermined change amount; when the absolute value of the difference between the operating frequency F2 of the second compressor and the optimal operating frequency Fmap is greater than the first specified frequency deviation value, and the operating frequency F2 is greater than the optimal operating frequency Fmap, the controller judges whether the absolute value of the difference between the operating frequency F2 and the anti-surge frequency Ffc is greater than or equal to the second specified frequency deviation value; when the judgment result is affirmative, the controller controls the second compressor to perform frequency unloading of a predetermined change amount; when the judgment result is negative, the controller controls the flasher to adjust the air supply pressure.

[0008] According to the above-mentioned heat pump unit of the present application, it can also be: the controller also has a fast loading control mode. In the fast loading control mode, when the difference between the target hot water temperature Tset and the actual hot water temperature Tout is greater than the fast loading temperature deviation setting value Tkjset, the controller determines whether the hot water temperature change rate is less than the specified change rate. When the judgment result is affirmative, the controller controls the first compressor and / or the second compressor to load at the fastest allowed loading speed. When the judgment result is negative, the controller controls the heat pump unit to adjust the compressor capacity, and in the fast loading control mode, when the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the fast loading temperature deviation setting value Tkjset, the controller controls the heat pump unit to adjust the compressor capacity.

[0009] According to the above-mentioned heat pump unit of the present application, it can also be: when the compressor capacity is adjusted, the controller controls the first compressor and the second compressor in a manner that the smaller the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout, the smaller the frequency adjustment increment.

[0010] According to the above-mentioned heat pump unit of the present application, the first compressor may also be a two-stage compressor, and the second compressor may be a single-stage compressor.

[0011] According to the above-mentioned heat pump unit of the present application, it can also be that: the air supply pipe of the flasher is connected to the air supply port of the first compressor.

[0012] According to the above-mentioned heat pump unit of the present application, the first compressor and the second compressor may both be two-stage compressors.

[0013] According to the above-mentioned heat pump unit of the present application, it can also be that: the air supply pipe of the flasher is connected to the connecting pipe connected between the first compressor and the second compressor.

[0014] According to the above-mentioned heat pump unit of the present application, a check valve may be provided between the second compressor and the condenser.

[0015] According to another scheme of the present application, a control method for a heat pump unit is provided. The heat pump unit includes: an evaporator, a first compressor, a second compressor, a condenser, and a flasher, wherein the evaporator, the first compressor, the second compressor and the condenser are connected in series, the flasher is connected between the evaporator and the condenser, and the first compressor or the second compressor is supplemented with air through an air supply pipe. The control method includes: when it is detected that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is greater than a preset water temperature tolerance Tpc, the compressor capacity of the first compressor and / or the second compressor is adjusted, and when it is detected that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to a preset water temperature tolerance Tpc, the pressure ratio of the second compressor is adjusted.

[0016] According to the above-mentioned control method of the present application, it can also be: including a pipeline network matching external closed-loop control mode and an efficiency optimization internal closed-loop control mode. In the pipeline network matching external closed-loop control mode, it is judged whether the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the water temperature tolerance Tpc. When the judgment result is affirmative, it is switched to the efficiency optimization internal closed-loop control mode. When the judgment result is negative, the compressor capacity is adjusted. In the efficiency optimization internal closed-loop control mode, according to the pre-obtained optimal operating frequency Fmap and anti-surge frequency Ffc, the operating frequency F2 of the second compressor and the air supply pressure of the flasher are adjusted.

[0017] According to the above-mentioned control method of the present application, it can also be: in the efficiency optimization internal closed-loop control mode, when the absolute value of the difference between the operating frequency F2 of the second compressor and the optimal operating frequency Fmap is greater than the first specified frequency deviation value, and the operating frequency F2 is less than the optimal operating frequency Fmap, the second compressor is subjected to frequency loading of a predetermined change amount; when the absolute value of the difference between the operating frequency F2 of the second compressor and the optimal operating frequency Fmap is greater than the first specified frequency deviation value, and the operating frequency F2 is greater than the optimal operating frequency Fmap, it is judged whether the absolute value of the difference between the operating frequency F2 and the anti-surge frequency Ffc is greater than or equal to the second specified frequency deviation value; when the judgment result is affirmative, the second compressor is subjected to frequency unloading of a predetermined change amount; when the judgment result is negative, the flasher is subjected to air supply pressure adjustment.

[0018] According to the above-mentioned control method of the present application, it can also be: also including a fast loading control mode, in which, when the difference between the target hot water temperature Tset and the actual hot water temperature Tout is greater than the fast loading temperature deviation setting value Tkjset, it is judged whether the hot water temperature change rate is less than the specified change rate, and when the judgment result is affirmative, the first compressor and / or the second compressor are loaded at the fastest allowed loading speed, and when the judgment result is negative, the heat pump unit is made to adjust the compressor capacity, and, in the fast loading control mode, when the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the fast loading temperature deviation setting value Tkjset, the heat pump unit is made to adjust the compressor capacity.

[0019] According to the above-mentioned control method of the present application, it can also be: when performing compressor capacity adjustment, the first compressor and the second compressor are controlled in a manner such that the smaller the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout, the smaller the frequency adjustment increment.

[0020] According to the above control method of the present application, it can also be: when the first compressor is a two-stage compressor and the second compressor is a single-stage compressor, when the flash ignitor is used to adjust the air supply pressure, the flash ignitor is controlled to supply air to the air supply port of the first compressor.

[0021] According to the above control method of the present application, it can also be: when the first compressor and the second compressor are both two-stage compressors, when the flash ignitor is made to adjust the air supply pressure, the flash ignitor is controlled to supply air to the connecting pipe between the first compressor and the second compressor.

[0022] Effects of the Invention

[0023] According to the heat pump unit and control method thereof of the present application, when it is detected that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is greater than the preset water temperature tolerance Tpc, the capacity of the first compressor and / or the second compressor is adjusted, and when it is detected that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the preset water temperature tolerance Tpc, the pressure ratio of the second compressor is adjusted, so that the first compressor and the second compressor in the heat pump unit have a design structure in which the speeds of the high and low pressure stages are independently decoupled, so that the speed ratio of the final stage (high pressure stage) is improved, and the efficiency of the compressor stage can be optimized.

[0024] In addition, by setting up two control modes, namely a pipeline network matching external closed-loop control mode and an efficiency optimization internal closed-loop control mode, the compressor capacity can be adjusted when the absolute value of the difference between the actual hot water temperature Tout and the target hot water temperature Tset is greater than the water temperature tolerance (that is, the difference between the two is large), so as to quickly reduce the difference between the actual hot water temperature Tout and the target hot water temperature Tset; and, when the absolute value of the difference between the actual hot water temperature Tout and the target hot water temperature Tset is less than or equal to the water temperature tolerance (that is, the difference between the two is small), efficiency optimization control is performed to more accurately adjust the load distribution of the two compressors and improve the operating efficiency of the heat pump unit. Thus, the dual-loop control of pipeline network load demand matching and internal optimization of compressor efficiency is realized, and the heat pump unit is effectively operated in the high-efficiency area.

[0025] In addition, by frequency loading or frequency unloading the second compressor according to the relationship between the operating frequency F2 of the second compressor and the optimal operating frequency Fmap, and by frequency unloading the second compressor or adjusting the air supply pressure of the flasher according to the relationship between the operating frequency F2 of the second compressor and the optimal operating frequency Fmap and the anti-surge frequency Ffc, the second compressor can be operated in a stable and efficient area, thereby enabling the heat pump unit to operate stably in the high-efficiency area.

[0026] In addition, by providing a fast loading control mode, the loading speed of the first compressor and the second compressor can be increased when the heat pump unit is started, and the unit can quickly enter a high-efficiency operation area.

[0027] Furthermore, when adjusting the compressor capacity, the first compressor and the second compressor are controlled so that the frequency adjustment increment becomes smaller as the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout becomes smaller, thereby enabling capacity adjustment to be performed efficiently and accurately.

[0028] In addition, since the temperature rise of the two-stage compressor is higher (for example, about 40°C) and the temperature rise of the single-stage compressor is lower (for example, about 20°C), however, the single-stage compressor is easier to match the pipeline load demand than the two-stage compressor. Therefore, when the temperature rise required by the heat pump unit is relatively low (for example, 50-70°C), by making the first compressor a two-stage compressor and the second compressor a single-stage compressor, it is possible to meet the temperature rise required by the heat pump unit while taking into account the ease of matching the pipeline load demand.

[0029] In addition, when the first compressor is a two-stage compressor and the second compressor is a single-stage compressor, by connecting the air supply pipe of the flash generator to the air supply port of the first compressor, the flash generator can supply air to the air supply port, thereby achieving a larger air supply volume for the first compressor as a two-stage compressor and improving the air supply efficiency.

[0030] In addition, as mentioned above, the temperature rise of the two-stage compressor is relatively high (for example, about 40°C). Therefore, when the temperature rise required by the heat pump unit is relatively high (for example, 70-100°C), by making both the first compressor and the second compressor two-stage compressors, the temperature rise can be increased to meet the temperature rise required by the heat pump unit.

[0031] In addition, when the first compressor and the second compressor are both two-stage compressors, the pressures of the first compressor and the second compressor can be more balanced by connecting the air supply pipe of the flash generator to the connecting pipe connected between the first compressor and the second compressor so that the flash generator can supply air to the connecting pipe between the first compressor and the second compressor.

[0032] In addition, by providing a check valve between the second compressor and the condenser, it is possible to prevent the compressor from reversing due to the backflow of high-pressure gas in the condenser when the heat pump unit is shut down. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a structural schematic diagram of an implementation mode of the heat pump unit of the present application.

[0034] Figure 2 It is a structural schematic diagram of another embodiment of the heat pump unit of the present application.

[0035] Figure 3 This is a quick loading control flow chart of the heat pump unit of the present application.

[0036] Figure 4 This is a flow chart of external closed-loop control of the pipe network matching of the heat pump unit of the present application.

[0037] Figure 5 This is an internal closed-loop control flow chart for optimizing the efficiency of the heat pump unit of the present application.

[0038] Description of reference numerals:

[0039] 1First compressor

[0040] 2. 2′ Second compressor

[0041] 3. Evaporator

[0042] 4 Condenser

[0043] 5 Flasher

[0044] 6First throttle valve

[0045] 7 Second throttle valve

[0046] 8 Check valve

[0047] 9. Gas supply electric valve

[0048] 10 Air supply pipe

[0049] 31Heat source entrance

[0050] 31a Heat source water inlet temperature detection device

[0051] 32 heat source outlet

[0052] 32a Heat source water outlet temperature detection device

[0053] 41 Hot water inlet

[0054] 41a Hot water inlet temperature detection device

[0055] 42 hot water outlet

[0056] 42a Hot water outlet temperature detection device

[0057] 100 heat pump units DETAILED DESCRIPTION

[0058] The present disclosure is described in detail below. In the following paragraphs, different aspects of the embodiments are defined in more detail. Each aspect so defined can be combined with any other aspect or aspects, unless explicitly stated not to be combined. In particular, any feature that is considered to be preferred or advantageous can be combined with one or more other features that are considered to be preferred or advantageous.

[0059] The terms "first", "second", etc. that appear in the present disclosure are only for the convenience of description to distinguish different components with the same name, and do not indicate a sequence or a primary and secondary relationship.

[0060] Furthermore, when a component is referred to as being “on” another component, the component may be directly on the other component, or may be indirectly on the other component with one or more intermediate components interposed therebetween. Additionally, when a component is referred to as being “connected to” another component, the component may be directly connected to the other component, or may be indirectly connected to the other component with one or more intermediate components interposed therebetween. Hereinafter, the same reference numerals denote the same components.

[0061] The descriptions of directions or positional relationships indicated by “upper”, “lower”, “top”, “bottom”, “front”, “back”, “inside” and “outside” in the present disclosure are only for the convenience of describing the present disclosure, and do not indicate or imply that the device referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as limiting the scope of protection of the present application.

[0062] Hereinafter, embodiments of the present application will be described in detail with reference to the accompanying drawings.

[0063] First, refer to Figure 1 , the overall structure of a heat pump unit according to an embodiment of the present application is described.

[0064] like Figure 1 As shown, for example, a heat pump unit 100 according to an embodiment of the present application is a dual compressor series heat pump unit. The heat pump unit 100 mainly includes an evaporator 3, a first compressor 1, a second compressor 2, and a condenser 4 connected in series through a connecting pipe so that the refrigerant can flow between these components, and a flasher 5 is provided between the condenser 4 and the evaporator 3, which is connected to the condenser 4 and the evaporator 3 through a connecting pipe. In addition, as Figure 1 As shown, the first compressor 1 is arranged closer to the evaporator 3 side than the second compressor 2 , and the second compressor 2 is arranged closer to the condenser 4 side than the first compressor 1 .

[0065] like Figure 1As shown, for example, the evaporator 3 may be equipped with a heat source inlet 31 and a heat source outlet 32, a heat source water inlet temperature detection device 31a may be provided at the heat source inlet 31, and a heat source water outlet temperature detection device 32a may be provided at the heat source outlet 32. Also, for example, the condenser 4 may be equipped with a hot water inlet 41 and a hot water outlet 42, a hot water inlet temperature detection device 41a may be provided at the hot water inlet, and a hot water outlet temperature detection device 42a may be provided at the hot water outlet 42.

[0066] In addition, if Figure 1 As shown, for example, a first throttle valve 6 may be provided in the connecting pipe between the condenser 4 and the evaporator 5. The first throttle valve 6 performs primary throttling on the refrigerant circulating in the heat pump unit 100, and plays a role in regulating the circulation flow of the refrigerant circulating in the heat pump unit 100. And, for example, a second throttle valve 7 may be provided in the connecting pipe between the flasher 5 and the evaporator 3. Similarly, the second throttle valve 7 performs secondary throttling on the refrigerant circulating in the heat pump unit 100, and plays a role in regulating the circulation flow of the refrigerant circulating in the heat pump unit 100. The first throttle valve 6 and the second throttle valve 7, for example, may be an electric butterfly valve, a fixed orifice plate or any other type of throttle valve suitable for regulating the circulation flow of the refrigerant.

[0067] In addition, if Figure 1 As shown, for example, a check valve 8 may be provided in the connecting pipe between the second compressor 2 and the condenser 4. By providing the check valve 8 in the connecting pipe between the second compressor 2 and the condenser 4, when the heat pump unit 100 is shut down, it is possible to prevent the high-pressure gas in the condenser 4 from flowing back to the second compressor 2 and causing the compressor to reverse, thereby avoiding damage to the compressor caused thereby.

[0068] exist Figure 1 In the example of the heat pump unit 100 shown, the first compressor 1 is a two-stage compressor, and the second compressor 2 is a single-stage compressor. Generally, a two-stage compressor can achieve a higher temperature rise, for example, about 40°C, while a single-stage compressor can achieve a lower temperature rise, for example, about 20°C. On the other hand, compared with a two-stage compressor, a single-stage compressor is easier to achieve a good match with the load demand of the pipeline network, while a two-stage compressor is more difficult to achieve a match with the load demand of the pipeline network. Therefore, when the heat pump unit needs to achieve a relatively low temperature rise (for example, 50 to 70°C), for example, a combination of a two-stage compressor and a single-stage compressor can be considered. Specifically, if Figure 1 As shown, the first compressor 1 is a two-stage compressor, and the second compressor 2 is a single-stage compressor, so that the required temperature rise of the heat pump unit 100 can be achieved while taking into account the ease of matching the pipe network load demand.

[0069] exist Figure 1 In the example of the heat pump unit 100 shown, as described above, it is easier to match the load demand of the second compressor 2 as a single-stage compressor, and it is easier to achieve pressure balance between the first compressor 1 and the second compressor 2. Therefore, when the first compressor 1 adopts a two-stage compressor and the second compressor 2 adopts a single-stage compressor, the air supply pipe 10 of the flash generator 5 is connected to the air supply port of the first compressor 1, and the flash generator 5 is used to directly supply air to the air supply port of the first compressor 1. In this way, the compressor can be supplied with a larger air supply amount, thereby improving the air supply efficiency. In addition, an air supply electric valve 9 can be provided in the air supply pipe 10 of the flash generator 5, so as to be able to adjust the air supply amount from the flash generator 5 to the air supply port of the first compressor 1. The air supply electric valve 9, for example, can be an electric butterfly valve, an electric ball valve or any other electric valve suitable for adjusting the air supply amount.

[0070] In addition, the heat pump unit of the present application is not limited to Figure 1 The first compressor 1 shown is a two-stage compressor, and the second compressor 2 is an example of a single compressor, but they can be combined arbitrarily according to actual needs. Figure 2 In the example of the heat pump unit 100 shown, both the first compressor 1 and the second compressor 2' are two-stage compressors. As described above, since the two-stage compressor can achieve a higher temperature rise, for example, about 40°C, while the temperature rise that a single-stage compressor can achieve is lower, therefore, when the heat pump unit needs to achieve a relatively high temperature rise (for example, 70-100°C), the first compressor 1 and the second compressor 2' are both two-stage compressors, so that the heat pump unit 100 can achieve a higher temperature rise.

[0071] In addition, Figure 2 In the example of the heat pump unit 100 shown, that is, when both the first compressor 1 and the second compressor 2' are two-stage compressors, in order to balance the pressure between the two two-stage compressors (that is, the first compressor 1 and the second compressor 2'), the air supply pipe 10 of the flash generator 5 can be connected to the connecting pipe connected between the first compressor 1 and the second compressor 2', and the flash generator 5 can be used to supply air to the position between the first compressor 1 and the second compressor 2'. Figure 1 In the example shown, a gas supply electric valve 9 may be provided in the gas supply pipe 10 of the flasher 5 so as to adjust the gas supply amount from the flasher 5 .

[0072] In addition, in the heat pump unit 100 of the present application, the first compressor and the second compressor can be fixed-frequency centrifugal compressors, variable-frequency centrifugal compressors, or a combination of fixed-frequency centrifugal compressors and variable-frequency centrifugal compressors, or any type of compressor that can be suitable for a heat pump unit.

[0073] Below, refer to Figures 3 to 5 , describing the control method of the heat pump unit 100 according to the present application.

[0074] The control method of the heat pump unit 100 of the present application includes a pipe network matching external closed-loop control mode, an efficiency optimization internal closed-loop control mode, and further, a fast loading control mode.

[0075] First, refer to Figure 3 , illustrating the fast loading control mode of the control method of the heat pump unit 100.

[0076] When the heat pump unit 100 is started, in order to make the heat pump unit enter the working state as soon as possible, it is hoped that the load can be performed at the fastest loading speed allowed by the compressor. In the fast loading control mode of the heat pump unit 100 of the present application, first, a controller (not shown in the drawings) is used to compare the preset target hot water temperature Tset with the actual hot water temperature Tout detected by the hot water outlet temperature detection device 42a set at the hot water outlet 42 of the condenser 4, and it is determined whether the difference between the target hot water temperature Tset and the actual hot water temperature Tout is greater than the fast loading temperature deviation setting value Tkjset. The fast loading temperature deviation setting value Tkjest is a value preset according to the actual needs of the heat pump unit 100, which can usually be set to a value within the range of 1 to 3°C, and can be adjusted according to the actual situation of the heat pump unit 100. When it is determined that the difference between the target hot water temperature Tset and the actual hot water temperature Tout is not greater than the fast loading temperature deviation setting value Tkjset (that is, the judgment result is negative), the controller controls the heat pump unit 100 to adjust the compressor capacity. When it is determined that the difference between the target hot water temperature Tset and the actual hot water temperature Tout is greater than the fast loading temperature deviation setting value Tkjset (i.e., the judgment result is positive), the controller determines whether the temperature change rate of the hot water is less than the specified change rate. When it is determined that the temperature change rate is less than the specified change rate (i.e., the judgment result is positive), the controller controls the heat pump unit 100 to perform fast loading, that is, the first compressor 1 and / or the second compressor 2, 2' are fast loaded, and then returns to the step of determining whether the difference between the target hot water temperature Tset and the actual hot water temperature Tout is greater than the fast loading temperature deviation setting value Tkjset. So-called fast loading means that the compressor is loaded at the fastest allowed loading speed. When the judgment result is negative, the controller controls the heat pump unit 100 to adjust the compressor capacity. The specified change rate can be set to 1°C / min, for example, but is not limited to this, and the specified change rate can be set to any value as needed.

[0077] After the fast loading control mode ends, the heat pump unit 100 enters the capacity loading adjustment stage. At this time, the controller controls the heat pump unit 100 in the pipe network matching external closed-loop control mode so that the capacity loading of the heat pump unit 100 matches the load demand of the entire pipe network system. Figure 3 , the external closed-loop control mode of the pipeline network matching is explained.

[0078] like Figure 3 As shown, in the pipe network matching external closed-loop control mode, the controller determines whether the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the water temperature tolerance Tpc. The water temperature tolerance Tpc refers to the maximum value of the allowable range of the water supply temperature deviation of the heat pump unit 100, which can be determined according to actual needs.

[0079] When it is determined that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is greater than the water temperature tolerance Tpc (the judgment result is negative), the controller controls the heat pump unit 100 to adjust the compressor capacity. In the case of adjusting the compressor capacity, the controller can control in such a way that the smaller the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is, the smaller the frequency adjustment increment of the first compressor 1 and / or the second compressor 2, 2' is. Specifically, for example, a first temperature deviation judgment value Tpc1 and a second temperature deviation judgment value Tpc2 may be pre-set, and when it is judged that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the first temperature deviation judgment value Tpc1, the first compressor 1 and / or the second compressor 2, 2' are controlled to perform frequency adjustment at a first frequency adjustment increment for each action cycle; when it is judged that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is greater than the first temperature deviation judgment value Tpc1 and less than the second temperature deviation judgment value Tpc2, the first compressor 1 and / or the second compressor 2, 2' are controlled to perform frequency adjustment at a second frequency adjustment increment for each action cycle; when it is judged that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is greater than or equal to the second temperature deviation judgment value Tpc2, the first compressor 1 and / or the second compressor 2, 2' are controlled to perform frequency adjustment at a third frequency adjustment increment for each action cycle. Among them, the water temperature tolerance Tpc, the first temperature deviation judgment value Tpc1 and the second temperature deviation judgment value Tpc2 satisfy the relationship of Tpc≤Tpc1≤Tpc2, and the values ​​of the water temperature tolerance Tpc, the first temperature deviation judgment value Tpc1 and the second temperature deviation judgment value Tpc2 can be set within an appropriate range according to actual needs. For example, Tpc can be set to a value within the range of 0.1 to 0.5°C, Tpc1 can be set to a value within the range of 0.5 to 1°C, and Tpc2 can be set to a value within the range of 1 to 3°C. Of course, it should be understood that the present application is not limited to the above range, and those skilled in the art can set it appropriately according to actual needs. In addition, the first frequency adjustment increment, the second frequency adjustment increment and the third frequency adjustment increment satisfy the relationship of the first frequency adjustment increment < the second frequency adjustment increment < the third frequency adjustment increment, and those skilled in the art can set their values ​​appropriately according to actual needs.As a specific example, for example, the first frequency adjustment increment can be set to 1 Hz, the second frequency adjustment increment can be set to 2 Hz, and the third frequency adjustment increment can be set to 3 Hz. In this case, when it is determined that |Tset-Tout|≤Tpc1, the controller controls the compressor (the first compressor 1 and / or the second compressor 2, 2′) to adjust the frequency in increments of 1 Hz per action cycle; when it is determined that Tpc1<|Tset-Tout|<Tpc2, the compressor (the first compressor 1 and / or the second compressor 2, 2′) adjusts the frequency in increments of 2 Hz per action cycle; when |Tset-Tout|≥Tpc2, the compressor (the first compressor 1 and / or the second compressor 2, 2′) adjusts the frequency in increments of 3 Hz per action cycle; the above process is repeated until the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the water temperature tolerance Tpc.

[0080] When it is determined that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the water temperature tolerance Tpc (the judgment result is positive), the controller switches the control mode from the pipe network matching external closed-loop control mode to the efficiency optimization inner-loop control mode. For the efficiency optimization inner-loop control mode, refer to Figure 4 Explain in detail.

[0081] like Figure 4 As shown, the efficiency optimization inner loop control mode is a control mode that mainly adjusts the pressure ratio of the second compressors 2 and 2' in the heat pump unit 100. In the efficiency optimization inner loop control mode, first, the controller calculates the absolute value of the difference between the operating frequency F2 of the second compressors 2 and 2' and the optimal operating frequency Fmap as the operating frequency deviation value of the second compressors 2 and 2', and determines whether the operating frequency deviation value is less than or equal to the first specified frequency deviation value. Among them, the optimal operating frequency Fmap is determined based on the MAP diagram (mapping diagram) of the compressor established in advance. The MAP diagram of the compressor is established based on the compressor's high-efficiency operating area, surge area, blockage area, etc. calculated from parameters such as the compressor's frequency, suction pressure, exhaust pressure, and compressor characteristic curve.

[0082] The first specified frequency deviation value is a judgment value for determining whether the compressor is operating in the high-efficiency region. Thus, when the absolute value of the difference between the operating frequency F2 of the second compressor and the optimal operating frequency Fmap, that is, the operating frequency deviation value of the second compressor 2, 2' is less than or equal to the first specified frequency deviation value, it can be determined that the second compressor 2, 2' is operating in the high-efficiency region. The specific value of the first frequency deviation value can be determined according to the parameters such as the frequency, suction pressure, exhaust pressure and compressor characteristic curve of the compressor, as well as actual needs. As an example, it can be set to 5 Hz, or it can also be set to 3 Hz, 6 Hz or other specific values. The smaller the first specified frequency deviation value is set, the closer the operating frequency of the compressor will be to the optimal operating frequency Fmap. The larger the first specified frequency deviation value is set, the wider the operating frequency of the compressor will be controlled relative to the optimal operating frequency Fmap.

[0083] Thus, when it is judged that the operating frequency deviation value of the second compressor 2, 2' (the absolute value of the difference between the operating frequency F2 of the second compressor 2, 2' and the optimal operating frequency Fmap) is less than or equal to the first specified frequency deviation value (the judgment result is affirmative), it indicates that the second compressor 2, 2' is operating in the high-efficiency area. Therefore, the controller controls the second compressor 2, 2' to maintain the current state unchanged.

[0084] When it is determined that the operating frequency deviation value of the second compressor 2, 2' (the absolute value of the difference between the operating frequency F2 of the second compressor 2, 2' and the optimal operating frequency Fmap) is greater than the first specified frequency deviation value (the judgment result is negative), it means that the operating frequency of the second compressor 2, 2' deviates from the high-efficiency area. Therefore, the controller further determines whether the operating frequency F2 of the second compressor 2, 2' is greater than or less than the optimal operating frequency Fmap.

[0085] When the operating frequency F2 of the second compressor 2, 2' is less than the optimal operating frequency Fmap, it means that the second compressor 2, 2' deviates downward from the high-efficiency area. Therefore, the controller controls the second compressor 2, 2' to load the frequency of the second compressor 2, 2' with a predetermined change amount. For the predetermined change amount, those skilled in the art can appropriately select it according to actual needs. As an example, for example, the second compressor 2, 2' can be loaded with a change amount of 1 Hz. After the second compressor 2, 2' is loaded with a predetermined change amount, the controller determines whether the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the water temperature tolerance Tpc. When it is determined that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the water temperature tolerance Tpc (the judgment result is affirmative), repeat the above steps in the efficiency optimization internal closed-loop control mode; when it is determined that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is greater than the water temperature tolerance Tpc (the judgment result is negative), exit the efficiency optimization internal closed-loop control mode and adjust the compressor capacity of the first compressor 1 and / or the second compressor 2, 2'.

[0086] On the other hand, when the operating frequency F2 of the second compressor 2, 2' is greater than the optimal operating frequency Fmap, it means that the second compressor 2, 2' deviates upward from the high-efficiency area. In this case, the controller further determines whether the difference between the operating frequency F2 of the second compressor and the anti-surge frequency Ffc is greater than or equal to the second specified frequency deviation value. The anti-surge frequency Ffc is predetermined according to the surge characteristics of the compressor. The second specified frequency deviation value can be appropriately set to any value according to actual needs. However, if the second specified frequency deviation value is set too small, the operation of the compressor will be close to the anti-surge line, and the operating state is prone to instability; on the other hand, if the second specified frequency deviation value is set too large, the adjustable range of the compressor will become narrower and easily deviate from the pipeline network load demand. As an example, for example, the second specified frequency deviation value can be set to 3Hz. When it is judged that the difference between the operating frequency F2 of the second compressor and the anti-surge frequency Ffc is less than the second specified frequency deviation value (the judgment result is negative), it means that the operation of the second compressor 2, 2' has left the stable area, and therefore, surge is prone to occur. In this case, the controller controls the air supply electric valve 9 provided in the air supply pipe 10 of the flasher 5 to adjust the air supply pressure of the flasher 5 to the air supply port of the first compressor 1, or between the first compressor 1 and the second compressor 2, 2', so that the compressor can operate in a stable area to avoid surge of the compressor. When it is determined that the difference between the operating frequency F2 of the second compressor and the anti-surge frequency Ffc is greater than or equal to the second specified frequency deviation value (the judgment result is positive), it means that the second compressor 2, 2' is operating in a stable area. In this case, the controller controls the second compressor 2, 2' to make the second compressor 2, 2' perform frequency unloading with a predetermined change amount. For the predetermined change amount, those skilled in the art can appropriately select it according to actual needs. As an example, for example, the second compressor 2, 2' can be made to perform frequency unloading with a change amount of 1 Hz. After making the second compressor 2, 2' perform frequency unloading with a predetermined change amount, the controller determines whether the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the water temperature tolerance Tpc. When it is determined that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the water temperature tolerance Tpc (the judgment result is affirmative), repeat the above steps in the efficiency optimization internal closed-loop control mode; when it is determined that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is greater than the water temperature tolerance Tpc (the judgment result is negative), exit the efficiency optimization internal closed-loop control mode and adjust the compressor capacity of the first compressor 1 and / or the second compressor 2, 2'.

[0087] The heat pump unit 100 of the present application is controlled in two modes: an external closed-loop control mode for network matching and an internal closed-loop control mode for efficiency optimization. It can achieve dual-loop control of network load demand matching and internal optimization of compressor efficiency, thereby effectively enabling the heat pump unit to operate in a high-efficiency and stable area.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A heat pump unit, comprising: An evaporator, a first compressor, a second compressor, a condenser, a flasher and a controller, wherein the evaporator, the first compressor, the second compressor and the condenser are connected in series, the first compressor is a compressor closer to the evaporator than the second compressor, the second compressor is a compressor closer to the condenser than the first compressor, the flasher is connected between the condenser and the evaporator, and the first compressor or the second compressor is supplemented with air through an air supplement pipe, characterized in that: When the controller detects that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is greater than the preset water temperature tolerance Tpc, the controller adjusts the compressor capacity of the first compressor and / or the second compressor. When the controller detects that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to a preset water temperature tolerance Tpc, the controller adjusts the pressure ratio of the second compressor.

2. The heat pump unit according to claim 1, characterized in that: The controller has an external closed-loop control mode for pipe network matching and an internal closed-loop control mode for efficiency optimization. In the pipe network matching external closed-loop control mode, the controller determines whether the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the water temperature tolerance Tpc. When the judgment result is positive, the controller switches to the efficiency optimization internal closed-loop control mode. When the judgment result is negative, the compressor capacity is adjusted. In the efficiency-optimizing internal closed-loop control mode, the controller adjusts the operating frequency F2 of the second compressor and / or the supplementary air pressure of the flash generator according to the pre-obtained optimal operating frequency Fmap and anti-surge frequency Ffc.

3. The heat pump unit according to claim 2, characterized in that: In the efficiency optimization internal closed-loop control mode, When the absolute value of the difference between the operating frequency F2 of the second compressor and the optimal operating frequency Fmap is greater than a first specified frequency deviation value, and the operating frequency F2 is less than the optimal operating frequency Fmap, the controller controls the second compressor to perform frequency loading of a predetermined variation. When the absolute value of the difference between the operating frequency F2 of the second compressor and the optimal operating frequency Fmap is greater than a first specified frequency deviation value, and the operating frequency F2 is greater than the optimal operating frequency Fmap, the controller determines whether the absolute value of the difference between the operating frequency F2 and the anti-surge frequency Ffc is greater than or equal to a second specified frequency deviation value. When the judgment result is affirmative, the controller controls the second compressor to perform frequency unloading of a predetermined change amount. When the judgment result is negative, the controller controls the flasher to adjust the air supply pressure.

4. The heat pump unit according to claim 3, characterized in that: The controller also has a fast loading control mode, In the fast loading control mode, when the difference between the target hot water temperature Tset and the actual hot water temperature Tout is greater than the fast loading temperature deviation set value Tkjset, the controller determines whether the hot water temperature change rate is less than the specified change rate. If the judgment result is affirmative, the controller controls the first compressor and / or the second compressor to load at the fastest allowed loading speed. If the judgment result is negative, the controller controls the heat pump unit to adjust the compressor capacity. Furthermore, in the rapid loading control mode, when the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the rapid loading temperature deviation setting value Tkjset, the controller controls the heat pump unit to adjust the compressor capacity.

5. The heat pump unit according to claim 3, characterized in that: When adjusting the compressor capacity, the controller controls the first compressor and the second compressor in such a manner that the frequency adjustment increment is reduced as the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is reduced.

6. The heat pump unit according to any one of claims 1 to 5, characterized in that: The first compressor is a two-stage compressor, and the second compressor is a single-stage compressor.

7. The heat pump unit according to claim 6, characterized in that: The air supply pipe of the flasher is connected to the air supply port of the first compressor.

8. The heat pump unit according to any one of claims 1 to 5, characterized in that: The first compressor and the second compressor are both two-stage compressors.

9. The heat pump unit according to claim 8, characterized in that: The air supply pipe of the flasher is connected to a connecting pipe connected between the first compressor and the second compressor.

10. The heat pump unit according to any one of claims 1 to 5, characterized in that: A check valve is provided between the second compressor and the condenser.

11. A control method for a heat pump unit, the heat pump unit comprising: An evaporator, a first compressor, a second compressor, a condenser, and a flasher, wherein the evaporator, the first compressor, the second compressor, and the condenser are connected in series, the flasher is connected between the evaporator and the condenser, and the first compressor or the second compressor is supplemented with air through an air supplement pipe, characterized in that the control method includes: When it is detected that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is greater than the preset water temperature tolerance Tpc, the capacity of the first compressor and / or the second compressor is adjusted. When it is detected that the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the preset water temperature tolerance Tpc, the pressure ratio of the second compressor is adjusted.

12. The control method according to claim 11, characterized in that: Including external closed-loop control mode for pipe network matching and internal closed-loop control mode for efficiency optimization. In the pipe network matching external closed-loop control mode, it is judged whether the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the water temperature tolerance Tpc. When the judgment result is positive, it is switched to the efficiency optimization internal closed-loop control mode. When the judgment result is negative, the compressor capacity is adjusted. In the efficiency optimization internal closed-loop control mode, the operating frequency F2 of the second compressor and the air supply pressure of the flash generator are adjusted according to the pre-obtained optimal operating frequency Fmap and anti-surge frequency Ffc.

13. The control method according to claim 12, characterized in that: In the efficiency optimization internal closed-loop control mode, When the absolute value of the difference between the operating frequency F2 of the second compressor and the optimal operating frequency Fmap is greater than a first specified frequency deviation value, and the operating frequency F2 is less than the optimal operating frequency Fmap, the second compressor is subjected to frequency loading of a predetermined variation. When the absolute value of the difference between the operating frequency F2 of the second compressor and the optimal operating frequency Fmap is greater than the first specified frequency deviation value, and the operating frequency F2 is greater than the optimal operating frequency Fmap, it is judged whether the absolute value of the difference between the operating frequency F2 and the anti-surge frequency Ffc is greater than or equal to the second specified frequency deviation value. When the judgment result is affirmative, the second compressor is made to perform frequency unloading of a predetermined change amount. When the judgment result is negative, the flasher is made to adjust the air supply pressure.

14. The control method according to claim 13, characterized in that: Also includes a fast loading control mode, In the fast loading control mode, when the difference between the target hot water temperature Tset and the actual hot water temperature Tout is greater than the fast loading temperature deviation set value Tkjset, it is determined whether the hot water temperature change rate is less than the specified change rate. If the determination result is positive, the first compressor and / or the second compressor are loaded at the fastest allowed loading speed. If the determination result is negative, the heat pump unit is caused to adjust the compressor capacity. Furthermore, in the rapid loading control mode, when the difference between the target hot water temperature Tset and the actual hot water temperature Tout is less than or equal to the rapid loading temperature deviation setting value Tkjset, the heat pump unit is caused to adjust the compressor capacity.

15. The control method according to claim 13, characterized in that: When the compressor capacity is adjusted, the first compressor and the second compressor are controlled so that the frequency adjustment increment is reduced as the absolute value of the difference between the target hot water temperature Tset and the actual hot water temperature Tout is reduced.

16. The control method according to any one of claims 11 to 15, characterized in that: When the first compressor is a two-stage compressor and the second compressor is a single-stage compressor, when the flash ignitor is caused to adjust the inflated air pressure, the flash ignitor is controlled to inflat air to the inflated air port of the first compressor.

17. The heat pump unit according to any one of claims 11 to 15, characterized in that: When both the first compressor and the second compressor are two-stage compressors, when the flash ignitor is caused to adjust the air supply pressure, the flash ignitor is controlled to supply air to the communication pipe between the first compressor and the second compressor.

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