Cascade heat pump system and control method

Abstract

The embodiment of the invention provides a cascade heat pump system and a control method, and relates to the technical field of heat pumps. A cascade water module; the cascade water module comprises an evaporative condenser; a compressor; a gas-liquid separator; a control valve; the heat exchanger comprises a low-temperature-level refrigerant area, and the low-temperature-level refrigerant area is used for heating the water inlet temperature of the heat exchanger to the target temperature; the low-temperature-stage refrigerant area is connected with the control valve, the evaporative condenser and the outdoor unit to form a low-temperature-stage refrigerant circulation loop; the high-temperature-stage refrigerant area is used for heating the target temperature to the water outlet temperature; the high-temperature refrigerant area is sequentially connected with the evaporative condenser, the gas-liquid separator and the compressor to form a high-temperature-stage refrigerant circulation loop; a controller; the controller is configured to adjust an opening degree of the control valve to a target opening degree according to the target temperature. According to the scheme, energy waste of the cascade heat pump system can be effectively reduced.

Description

Technical Field

[0001] This application relates to the field of heat pump technology. More specifically, it relates to a cascade heat pump system and its control method. Background Technology

[0002] In scenarios such as high-temperature disinfection and washing, users typically need equipment that can directly heat low-temperature water (e.g., 15°C) to high-temperature hot water of 80~90°C and deliver it to the user immediately to meet the actual needs of high-temperature and continuous water use.

[0003] Currently, solutions for high-temperature hot water demand mainly include traditional heating (such as electric heating, gas heating, etc.), single-stage compression heat pump + electric heating, and cascade heat pump heating. Among these, cascade heat pump heating has become an ideal choice due to its lowest energy consumption.

[0004] However, in existing cascade heat pump heating systems, the temperature difference between the inlet water and the refrigerant is extremely large, resulting in significant energy waste. Summary of the Invention

[0005] This application provides a cascade heat pump system and control method to reduce energy waste in the cascade heat pump system.

[0006] In a first aspect, embodiments of this application provide a cascade heat pump system, including:

[0007] Outdoor unit;

[0008] Cascaded water module; the cascaded water module includes:

[0009] Evaporator-condenser;

[0010] compressor;

[0011] Gas-liquid separator;

[0012] Control valve;

[0013] A heat exchanger, the heat exchanger comprising:

[0014] The low-temperature refrigerant zone is used to heat the inlet water temperature of the heat exchanger to the target temperature; the low-temperature refrigerant zone is connected to the control valve, the evaporator-condenser and the outdoor unit to form a low-temperature refrigerant circulation loop;

[0015] The high-temperature refrigerant zone is used to heat the target temperature to the outlet water temperature; the high-temperature refrigerant zone is connected in sequence to the evaporator-condenser, the gas-liquid separator and the compressor to form a high-temperature refrigerant circulation loop;

[0016] Controller; the controller is configured to:

[0017] According to the target temperature, the opening degree of the control valve is adjusted to the target opening degree so that the low-temperature refrigerant zone heats the inlet water temperature of the heat exchanger to the target temperature.

[0018] In some embodiments, the controller is configured to:

[0019] The target temperature for heat exchange in the low-temperature refrigerant zone is determined based on the outlet water temperature and the inlet water temperature.

[0020] The target opening degree of the control valve is determined based on the target temperature, and the opening degree of the control valve is adjusted to the target opening degree.

[0021] In some embodiments, the controller is configured to:

[0022] Determine the initial intermediate water temperature based on the outlet water temperature and the inlet water temperature;

[0023] The coefficient of performance (COP) of the cascade heat pump system is determined based on the outlet water temperature, the inlet water temperature, and the initial intermediate water temperature.

[0024] The target temperature is determined based on the performance coefficient.

[0025] In some embodiments, the controller is configured to:

[0026] Determine a first amount of heat to heat the outlet water temperature to the initial intermediate water temperature, and a second amount of heat to heat the initial intermediate water temperature to the outlet water temperature;

[0027] Determine the first power of the compressor in the outdoor unit, and the second power of the compressor in the cascade water module;

[0028] The performance coefficient is determined based on the first heat, the second heat, the first power, and the second power.

[0029] In some embodiments, the controller is configured to:

[0030] The initial intermediate water temperature is updated to determine the target intermediate water temperature, and the corresponding performance coefficient is determined based on the target intermediate water temperature.

[0031] The process involves iteratively updating the intermediate water temperature and determining the corresponding performance coefficients.

[0032] When the difference between the intermediate water temperature corresponding to the K+1 reel and the intermediate water temperature corresponding to the K reel is less than a preset value, the intermediate water temperature corresponding to the K+1 reel is taken as the target temperature; where K is an integer greater than 1.

[0033] In some embodiments, the controller is configured to:

[0034] Using the target temperature as the heat exchange target of the low-temperature refrigerant zone, the opening adjustment amount of the control valve is determined based on the difference between the current heat exchange temperature of the low-temperature refrigerant zone and the target temperature.

[0035] The target opening is determined based on the opening adjustment amount.

[0036] In some embodiments, the controller is configured to:

[0037] Using the target temperature as the heat exchange target of the low-temperature refrigerant zone, an adjustment model for the control valve is constructed;

[0038] The difference between the current heat exchange temperature of the low-temperature refrigerant region and the target temperature is used as the input of the adjustment model to obtain the opening adjustment amount output by the adjustment model.

[0039] In some embodiments, the type of refrigerant in the low-temperature refrigerant zone is different from that in the high-temperature refrigerant zone.

[0040] Secondly, embodiments of this application provide a control method for a cascade heat pump system, the cascade heat pump system comprising:

[0041] Outdoor unit;

[0042] Cascaded water module; the cascaded water module includes:

[0043] Evaporator-condenser;

[0044] compressor;

[0045] Gas-liquid separator;

[0046] Control valve;

[0047] A heat exchanger, the heat exchanger comprising:

[0048] The low-temperature refrigerant zone is used to heat the inlet water temperature of the heat exchanger to the target temperature; the low-temperature refrigerant zone is connected to the control valve, the evaporator-condenser and the outdoor unit to form a low-temperature refrigerant circulation loop;

[0049] The high-temperature refrigerant zone is used to heat the target temperature to the outlet water temperature; the high-temperature refrigerant zone is connected in sequence to the evaporator-condenser, the gas-liquid separator and the compressor to form a high-temperature refrigerant circulation loop;

[0050] The method includes:

[0051] According to the target temperature, the opening degree of the control valve is adjusted to the target opening degree so that the low-temperature refrigerant zone heats the inlet water temperature of the heat exchanger to the target temperature.

[0052] In some embodiments, adjusting the opening of the control valve to the target opening based on the target temperature includes:

[0053] The target temperature for heat exchange in the low-temperature refrigerant zone is determined based on the outlet water temperature and the inlet water temperature.

[0054] The target opening degree of the control valve is determined based on the target temperature, and the opening degree of the control valve is adjusted to the target opening degree.

[0055] Thirdly, embodiments of this application provide an electrical device, including: a processor, a transceiver, and a memory; the processor is communicatively connected to the transceiver and the memory respectively;

[0056] The memory is used to store computer programs;

[0057] The transceiver is used for communication and interaction with external devices;

[0058] The processor is configured to execute the computer program to implement the second aspect and / or various possible implementations of the second aspect.

[0059] Fourthly, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the second aspect and / or various possible implementations of the second aspect as described above.

[0060] Fifthly, embodiments of this application provide a computer program product, including a computer program that, when executed by a processor, implements the second aspect and / or various possible implementations of the second aspect as described above.

[0061] The cascade heat pump system and control method provided in this application divide the refrigerant storage area of ​​the water-fluorine heat exchanger into a low-temperature refrigerant area and a high-temperature refrigerant area. The low-temperature and high-temperature refrigerant areas sequentially exchange heat with the inlet water. When the low-temperature refrigerant area exchanges heat with the inlet water, the temperature difference between the refrigerant and the inlet water is significantly reduced due to the lower temperature of the refrigerant. When the high-temperature refrigerant area exchanges heat with the inlet water, the water temperature has already increased significantly after one heat exchange, and the temperature difference between the inlet water and the high-temperature refrigerant is also significantly reduced. Therefore, through this design, the temperature difference between the water and the refrigerant is significantly reduced, effectively reducing energy waste. Attached Figure Description

[0062] To more clearly illustrate the implementation methods in the embodiments of this application or related technologies, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0063] Figure 1 This is a schematic diagram of a cascade heat pump system;

[0064] Figure 2 A flowchart illustrating a control method for a cascade heat pump system provided in this application. Figure 1 ;

[0065] Figure 3 A schematic diagram of a heat exchange temperature difference provided in this application;

[0066] Figure 4 This application provides a schematic diagram of the structure of a cascade heat pump system;

[0067] Figure 5 A flowchart illustrating a control method for a cascade heat pump system provided in this application. Figure 1 ;

[0068] Figure 6 A flowchart illustrating a control method for a cascade heat pump system provided in this application. Figure 2 ;

[0069] Figure 7 A flowchart illustrating a control method for a cascade heat pump system provided in this application. Figure 3 ;

[0070] Figure 8 This is a schematic diagram of the control device for a cascade heat pump system provided in this application.

[0071] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0072] To make the objectives, implementation methods and advantages of this application clearer, the exemplary implementation methods of this application will be clearly and completely described below with reference to the accompanying drawings of the exemplary embodiments of this application. Obviously, the described exemplary embodiments are only some embodiments of this application, and not all embodiments.

[0073] It should be noted that the brief descriptions of terms in this application are only for the convenience of understanding the embodiments described below, and are not intended to limit the embodiments of this application. Unless otherwise stated, these terms should be understood in their ordinary and common meaning.

[0074] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover but not exclusively include, for example, a product or device that includes a series of components is not necessarily limited to those that are explicitly listed, but may include other components that are not explicitly listed or that are inherent to such product or device.

[0075] The terms "first" and "second" are configured for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0076] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0077] Figure 1 This is a schematic diagram of a cascade heat pump system provided in an embodiment of this application, as shown below. Figure 1 As shown, the cascade heat pump system includes an outdoor unit and a cascade water module.

[0078] The outdoor unit includes an outdoor heat exchanger, a gas-liquid separator (referred to as gas separator), and a compressor. The outdoor unit is also known as a low-temperature circulation system.

[0079] The cascade water module includes an evaporator-condenser, a gas-liquid separator, a compressor, and a water-fluorine heat exchanger. The cascade water module is also known as a high-temperature circulation system.

[0080] In the outdoor unit, the refrigerant absorbs heat from the air and evaporates into refrigerant gas in the outdoor heat exchanger. The refrigerant gas then flows into the gas-liquid separator for gas-liquid separation before flowing into the compressor. The compressor compresses and heats the gas before sending it to the evaporator-condenser in the cascade water module, where it releases heat to the refrigerant in the high-temperature cycle system.

[0081] In the cascade water module, the refrigerant that absorbs heat from the outdoor unit evaporates into a medium-temperature gas. After gas-liquid separation, the medium-temperature refrigerant gas flows from the evaporator to the gas-liquid separator. The compressor then compresses the gas to a higher temperature and sends it to the water-fluorine heat exchanger, where the heat is completely released to the cold water, thereby producing the required high-temperature hot water.

[0082] like Figure 2 As shown, in the water-fluoride heat exchanger, from the inlet to the middle region, the temperature difference between the inlet water and the high-temperature refrigerant is extremely large, resulting in significant energy waste.

[0083] In view of this, this application provides a cascade heat pump system and control method. By designing the refrigerant in the water-fluoride heat exchanger into zones, the low-temperature stage refrigerant from the outdoor unit heats the cold water from the inlet to the middle section, while the high-temperature stage refrigerant heats the water from the middle section to the outlet section, achieving the target water temperature. Through zoned refrigerant heating, the temperature difference in water-fluoride heat exchange from the inlet to the middle area is significantly reduced, effectively reducing the waste of high-grade energy.

[0084] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0085] Figure 3 A schematic diagram of a cascade heat pump system provided in this application Figure 2 ,like Figure 3 As shown, the cascade heat pump system includes an outdoor unit and a cascade water module.

[0086] The outdoor unit includes an outdoor heat exchanger, a gas-liquid separator (referred to as gas separator), and a compressor. The outdoor unit is also known as a low-temperature circulation system.

[0087] The cascade water module includes an evaporator-condenser, a gas-liquid separator, a compressor, control valves, and a water-fluorine heat exchanger. The cascade water module is also known as a high-temperature circulation system.

[0088] refer to Figure 3 and Figure 4 As shown, the water-fluoride heat exchanger includes an inlet / outlet side and a refrigerant side. The refrigerant side includes a low-temperature refrigerant zone and a high-temperature refrigerant zone. The low-temperature and high-temperature refrigerant zones are separated.

[0089] In some embodiments, the types of refrigerant flowing through the low-temperature refrigerant zone and the high-temperature refrigerant zone are different. For example, the refrigerant flowing through the low-temperature refrigerant zone can be low-temperature refrigerant such as R410A or R32. The refrigerant flowing through the high-temperature refrigerant zone can be high-temperature refrigerant such as R134A, R513A, R515B, or R290.

[0090] like Figure 3 As shown, in the low-temperature circulation system, when the low-temperature refrigerant, after being processed multiple times by the outdoor heat exchanger, gas-liquid separator and compressor, flows into the cascade water module, it is divided into loop 1 and loop 2.

[0091] In loop 1, the low-temperature refrigerant flows into the inlet of the low-temperature refrigerant zone, passes through the outlet of the low-temperature refrigerant zone, and then flows back to the outdoor heat exchanger after passing through a control valve (such as EVW1).

[0092] In loop 2, the low-temperature refrigerant flows into the evaporator-condenser and then flows back to the outdoor heat exchanger after passing through the control valve.

[0093] like Figure 2 As shown, in the high-temperature cycle system, the refrigerant flows through loop 3. After flowing out of the evaporator and condenser, the refrigerant in loop 3 passes through the gas-liquid separator and the compressor before flowing into the high-temperature refrigerant zone. The refrigerant flowing out of the high-temperature refrigerant zone flows back to the evaporator and condenser.

[0094] In some embodiments, after the refrigerant in loop 1 flows into the low-temperature refrigerant region, it exchanges heat with the water in the water-fluoride heat exchanger from the inlet to the middle region.

[0095] The refrigerant in loop 2 flows into the evaporator-condenser to exchange heat with the refrigerant in loop 3, raising the temperature of the refrigerant in loop 3.

[0096] After heat exchange in loop 3, the refrigerant is heated a second time by the compressor to a high temperature. The high-temperature refrigerant flows into the high-temperature stage refrigerant zone and exchanges heat with the water in the middle area of ​​the water-fluoride heat exchanger to the outlet area.

[0097] In some embodiments, in a water-fluoride heat exchanger, the refrigerant in the low-temperature refrigerant zone exchanges heat with the water from the inlet to the middle zone to raise the inlet water temperature. When the water that has undergone heat exchange in the low-temperature refrigerant zone flows through the high-temperature refrigerant zone, the refrigerant in the high-temperature refrigerant zone undergoes secondary heat exchange to heat the outlet water to the target water temperature.

[0098] The above-described water-fluorine heat exchanger divides the refrigerant storage area into a low-temperature refrigerant zone and a high-temperature refrigerant zone. These two zones sequentially exchange heat with the inlet water. In the low-temperature refrigerant zone, the temperature difference between the refrigerant and the inlet water is significantly reduced due to the lower refrigerant temperature. Conversely, in the high-temperature refrigerant zone, the water temperature has already increased significantly after the first heat exchange, further reducing the temperature difference between the refrigerant and the high-temperature refrigerant. Therefore, this design significantly reduces the temperature difference between the water and the refrigerant, effectively minimizing energy waste.

[0099] In some embodiments, the low-temperature refrigerant enters the evaporator-condenser (loop 2) to exchange heat with the high-temperature refrigerant, and simultaneously enters the low-temperature refrigerant zone (loop 1) of the water-refrigerant heat exchanger to exchange heat with the inlet water. Therefore, the flow distribution of the low-temperature refrigerant in loops 1 and 2 becomes a determining factor in the energy efficiency of the cascade heat pump system. For example, a larger refrigerant flow rate in loop 1 results in higher heat exchange efficiency in the low-temperature refrigerant zone. Conversely, a smaller refrigerant flow rate in loop 2 leads to a decrease in the temperature of the high-temperature refrigerant, thereby reducing the heat exchange efficiency in the high-temperature refrigerant zone.

[0100] Based on this, this application embodiment also provides a control method for a cascade heat pump system, which can effectively improve the energy efficiency of the cascade heat pump system by distributing the flow of refrigerant in loop 1 and loop 2.

[0101] Figure 5 A flowchart illustrating a control method for a cascade heat pump system provided in this application embodiment is shown below. Figure 5 As shown, it includes:

[0102] S501. Adjust the opening of the control valve to the target opening according to the target temperature, so that the low-temperature refrigerant zone heats the inlet water temperature of the heat exchanger to the target temperature.

[0103] In some embodiments, the target temperature is the temperature reached by the inlet water after heat exchange between the low-temperature refrigerant zone and the inlet water under the optimal energy efficiency of the cascade heat pump system.

[0104] In some embodiments, the opening degree of the control valve is used to adjust the refrigerant distribution flow rate. For example, such as Figure 3 As shown, when the control valve is EVW1, the larger the opening degree of the control valve, the greater the flow rate of refrigerant in circuit 1. For ease of understanding, the control valve referred to thereafter will be EVW1.

[0105] In some embodiments, the target temperature can be determined based on the inlet water temperature and the outlet water temperature.

[0106] For example, an initial intermediate temperature is assumed based on the inlet and outlet water temperatures, and the coefficient of performance (COP) of the cascade heat pump system is calculated based on this intermediate temperature. A related iterative algorithm is used to iteratively correct the initial intermediate temperature, and the COP of the cascade heat pump system corresponding to each corrected intermediate temperature is calculated. The multiple COPs are compared, and the intermediate temperature corresponding to the optimal COP is taken as the target temperature.

[0107] After determining the target temperature, based on the target temperature and the inlet water temperature after heat exchange in the current low-temperature refrigerant zone, the opening degree of the control valve is adjusted to the target opening degree using fuzzy logic control or error control, so as to allocate a matching flow rate of refrigerant to the low-temperature refrigerant zone, so that the low-temperature refrigerant zone heats the inlet water temperature of the heat exchanger to the target temperature.

[0108] The above solution, by adjusting the opening of the control valve to control the flow rate of refrigerant flowing through the low-temperature refrigerant zone, can achieve the best energy efficiency of the cascade heat pump system while heating the inlet water temperature to the preset outlet water temperature.

[0109] The following is combined with Figure 6 The process of determining the target temperature in the embodiments of this application will be described.

[0110] Figure 6 A flowchart illustrating a control method for a cascade heat pump system provided in this application embodiment. Figure 2 ,like Figure 6 As shown, it includes:

[0111] S601. Determine the initial intermediate water temperature based on the outlet water temperature and the inlet water temperature.

[0112] In some embodiments, the initial intermediate water temperature can be assumed to be the average of the outlet water temperature and the inlet water temperature.

[0113] For example, the inlet water temperature is denoted as Twi, the outlet water temperature as Two, and the initial intermediate water temperature as Twm. Twm = (Twi + Two) / 2.

[0114] In some embodiments, the initial intermediate water temperature may be assumed in other ways, such as 0.5x the outlet water temperature, 1.5x the inlet water temperature, etc., and this application embodiment does not limit this.

[0115] S602. Determine the coefficient of performance of the cascade heat pump system based on the outlet water temperature, the inlet water temperature, and the initial target intermediate water temperature.

[0116] In some embodiments, after determining the initial intermediate water temperature, the coefficient of performance of the cascade heat pump system can be determined in the manner shown below.

[0117] For example, a first amount of heat required to heat the inlet water temperature to the initial intermediate water temperature, and a second amount of heat required to heat the initial intermediate water temperature to the outlet water temperature are determined; a first power of the compressor in the outdoor unit and a second power of the compressor in the cascade water module are determined; and the coefficient of performance is determined based on the first amount of heat, the second amount of heat, the first power, and the second power.

[0118] For example, the performance coefficients satisfy the following formula:

[0119]

[0120] in, For the water side to absorb heat, by Heat to The heat at the location;

[0121] For the water side to absorb heat, by Heat to The heat at the location;

[0122] The heat released by high-temperature refrigerant; the heat released by high-temperature refrigerant when heating water.

[0123] The heat released by the low-temperature refrigerant; the heat released by the low-temperature refrigerant when heating water.

[0124] The total work done by the cryogenic stage compressor;

[0125] The low-temperature stage is used for the compressor to perform work in the water supply heat exchange stage;

[0126] The low-temperature stage is used to perform work on the compressor for heat exchange of the refrigerant;

[0127] The high-temperature compressor performs the work;

[0128] The low-temperature refrigerant circulation flow rate is 1, and this portion of the refrigerant is used to heat low-temperature water.

[0129] The low-temperature refrigerant circulation flow rate is 2, and this part of the refrigerant is used to heat the high-temperature refrigerant.

[0130] The circulation of water;

[0131] High-temperature refrigerant circulation flow rate;

[0132] Specific heat capacity of water;

[0133] The enthalpy value at the discharge point of the cryogenic compressor;

[0134] Enthalpy at the outlet of a low-temperature refrigerant condenser used for heating water;

[0135] The enthalpy value at the suction point of the cryogenic compressor;

[0136] Enthalpy at the suction port of the high-temperature compressor;

[0137] Enthalpy at the outlet of the high-temperature stage condenser;

[0138] Enthalpy value at the exhaust port of the high-temperature compressor.

[0139] S603. Determine the target temperature based on the performance coefficient.

[0140] In some embodiments, the performance coefficient corresponding to the initial intermediate water temperature can be determined by iteratively updating the initial intermediate water temperature to obtain the performance coefficients corresponding to multiple target intermediate water temperatures, and the target temperature can be determined based on the multiple performance coefficients.

[0141] For example, the initial intermediate water temperature is updated to determine the target intermediate water temperature, and the corresponding performance coefficient is determined based on the target intermediate water temperature; the process of updating the intermediate water temperature and determining the corresponding performance coefficient is iteratively executed; when the difference between the intermediate water temperature corresponding to round K+1 and the intermediate water temperature corresponding to round K is less than a preset value, the intermediate water temperature corresponding to round K+1 is taken as the target temperature; where K is an integer greater than 1.

[0142] For example, if the initial intermediate water temperature is Twm_k, COP_k is determined based on the above formula.

[0143] Give Twm_k a small increment Δ, and let Twm_plus = Twm_k + Δ. Calculate COP_plus in the same way. Then calculate its first derivative: f_k = (COP_plus - COP_k) / Δ.

[0144] Given a small increment Δ to Twm_k, let Twm_minus = Twm_k - Δ, calculate COP_minus. Also calculate its second derivative f'_k = (COP_plus - 2Δ). COP_k+COP_minus) / (Δ^2).

[0145] Update the intermediate water temperature:

[0146] Twm_{k+1}=Twm_k-f_k / f'_k.

[0147] If |Twm_{k+1}-Twm_k|<ε (ε is the set threshold), or the maximum number of iterations is reached, then stop the iteration and output the target temperature Twmo=Twm_{k+1}. Otherwise, let k=k+1 and continue the iteration.

[0148] Alternatively, the target water temperature can be solved iteratively using various iterative calculation methods such as the bisection method, the secant method, and the genetic algorithm. This application does not limit the specific iterative algorithm.

[0149] The following is combined with Figure 7 The process of determining the target opening degree of the control valve in the embodiments of this application will be described.

[0150] Figure 7 A flowchart illustrating a control method for a cascade heat pump system provided in this application embodiment. Figure 3 ,like Figure 7 As shown, it includes:

[0151] S701. Using the target temperature as the heat exchange target of the low-temperature refrigerant zone, determine the opening adjustment amount of the control valve based on the difference between the current heat exchange temperature of the low-temperature refrigerant zone and the target temperature.

[0152] For example, the target temperature is used as the heat exchange target of the low-temperature refrigerant region to construct an adjustment model for the control valve; the difference between the current heat exchange temperature of the low-temperature refrigerant region and the target temperature is used as the input of the adjustment model to obtain the opening adjustment amount output by the adjustment model.

[0153] For example, the adjustment model of the control valve can be as follows:

[0154]

[0155]

[0156] Where △EVW1 is the control amount for adjusting the opening of the control valve each time. kp and ki are the proportional and integral coefficients, respectively, and T is the control period.

[0157] Alternatively, fuzzy control logic, fuzzy PID, or other methods can be used to determine the opening adjustment amount.

[0158] S702. Determine the target opening based on the opening adjustment amount.

[0159] In some embodiments, the opening of the control valve can be gradually adjusted based on the opening adjustment amount until the opening of the control valve is adjusted to the target opening.

[0160] In summary, the cascade heat pump system and control method provided in this application significantly reduce the heat exchange temperature difference in the water-fluorine heat exchange process and optimize the refrigerant quantity distribution through heat exchanger refrigerant zoning design and superimposed dual refrigerant zoning control algorithm, thereby effectively utilizing the heat of high-temperature and low-temperature refrigerants and significantly improving the energy efficiency of product operation.

[0161] Based on the above embodiments, this application also provides a control device for a cascade heat pump system.

[0162] Figure 8 This is a schematic diagram of the structure of the control device 80 of the cascade heat pump system provided in the embodiments of this application, as shown below. Figure 8 As shown, it includes:

[0163] The processing module 801 is used to determine the target temperature of the heat exchange in the low-temperature refrigerant zone based on the outlet water temperature and the inlet water temperature, and to determine the target opening degree of the control valve based on the target temperature.

[0164] The control module 802 is used to adjust the opening degree of the control valve to the target opening degree.

[0165] In some embodiments, the processing module 801 is configured to determine an initial intermediate water temperature based on the outlet water temperature and the inlet water temperature; determine the coefficient of performance (COP) of the cascade heat pump system based on the outlet water temperature, the inlet water temperature, and the initial intermediate water temperature; and determine the target temperature based on the COP.

[0166] In some embodiments, the processing module 801 is configured to determine a first amount of heat required to heat the outlet water temperature to the initial intermediate water temperature, and a second amount of heat required to heat the initial intermediate water temperature to the outlet water temperature; determine a first power of the compressor in the outdoor unit, and a second power of the compressor in the cascade water module; and determine the coefficient of performance based on the first amount of heat, the second amount of heat, the first power, and the second power.

[0167] In some embodiments, the processing module 801 is used to update the initial intermediate water temperature, determine a target intermediate water temperature, and determine the corresponding performance coefficient based on the target intermediate water temperature; iteratively execute the process of updating the intermediate water temperature and determining the corresponding performance coefficient; when the difference between the intermediate water temperature corresponding to round K+1 and the intermediate water temperature corresponding to round K is less than a preset value, the intermediate water temperature corresponding to round K+1 is taken as the target temperature; where K is an integer greater than 1.

[0168] In some embodiments, the processing module 801 is configured to take the target temperature as the heat exchange target of the low-temperature refrigerant region, determine the opening adjustment amount of the control valve based on the difference between the current heat exchange temperature of the low-temperature refrigerant region and the target temperature, and determine the target opening amount based on the opening adjustment amount.

[0169] In some embodiments, the processing module 801 is used to construct an adjustment model for the control valve with the target temperature as the heat exchange target of the low-temperature refrigerant region; and to obtain the opening adjustment amount output by the adjustment model by using the difference between the current heat exchange temperature of the low-temperature refrigerant region and the target temperature as the input of the adjustment model.

[0170] The control device for a cascade heat pump system provided in this application embodiment can execute the control method for the cascade heat pump system shown in any of the above embodiments. Its principle and technical effect are similar, and will not be described again here.

[0171] This application also provides an electronic device, which may include a transceiver, a processor, and a memory. This electronic device may be a controller as described in any of the above embodiments.

[0172] The processor executes computer execution instructions stored in memory, causing the processor to perform the schemes in the above embodiments. The processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0173] The memory is connected to the processor via the system bus and communicates with it. The memory is used to store computer program instructions.

[0174] A transceiver can perform the functions of receiving and sending data and instructions.

[0175] Optionally, the electronic device may also include a communication interface to communicate and interact with external or internal devices, such as client devices (e.g., mobile phones, tablets). In specific implementations, if the communication interface, memory, and processor are implemented independently, they can be interconnected via a bus to complete communication with each other.

[0176] The system bus can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. The system bus can be divided into address bus, data bus, control bus, etc. For ease of representation, only one thick line is used in the diagram, but this does not indicate that there is only one bus or one type of bus. Transceivers are used to enable communication between database access devices and other computers (e.g., clients, read-write libraries, and read-only libraries). Memory may include random access memory (RAM) and may also include non-volatile memory.

[0177] Optionally, in a specific implementation, if the communication interface, memory, and processor are integrated on a single chip, then the communication interface, memory, and processor can communicate through an internal interface.

[0178] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0179] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described method.

[0180] The aforementioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0181] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an Application Specific Integrated Circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components in the device.

[0182] The division of units is merely a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0183] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0184] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0185] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0186] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0187] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A cascade heat pump system, characterized in that, include: Outdoor unit; Cascade water modules; The superimposed water module includes: Evaporator-condenser; compressor; Gas-liquid separator; Control valve; A heat exchanger, the heat exchanger comprising: The low-temperature refrigerant zone is used to heat the inlet water temperature of the heat exchanger to the target temperature; the low-temperature refrigerant zone is connected to the control valve, the evaporator-condenser and the outdoor unit to form a low-temperature refrigerant circulation loop; The high-temperature refrigerant zone is used to heat the target temperature to the outlet water temperature; the high-temperature refrigerant zone is connected in sequence to the evaporator-condenser, the gas-liquid separator and the compressor to form a high-temperature refrigerant circulation loop; Controller; the controller is configured to: According to the target temperature, the opening degree of the control valve is adjusted to the target opening degree so that the low-temperature refrigerant zone heats the inlet water temperature of the heat exchanger to the target temperature.

2. The cascade heat pump system according to claim 1, characterized in that, The controller is configured to: The target temperature for heat exchange in the low-temperature refrigerant zone is determined based on the outlet water temperature and the inlet water temperature. The target opening degree of the control valve is determined based on the target temperature, and the opening degree of the control valve is adjusted to the target opening degree.

3. The cascade heat pump system according to claim 2, characterized in that, The controller is configured to: Determine the initial intermediate water temperature based on the outlet water temperature and the inlet water temperature; The coefficient of performance (COP) of the cascade heat pump system is determined based on the outlet water temperature, the inlet water temperature, and the initial intermediate water temperature. The target temperature is determined based on the performance coefficient.

4. The cascade heat pump system according to claim 3, characterized in that, The controller is configured to: Determine a first amount of heat to heat the outlet water temperature to the initial intermediate water temperature, and a second amount of heat to heat the initial intermediate water temperature to the outlet water temperature; Determine the first power of the compressor in the outdoor unit, and the second power of the compressor in the cascade water module; The performance coefficient is determined based on the first heat, the second heat, the first power, and the second power.

5. The cascade heat pump system according to claim 3, characterized in that, The controller is configured to: The initial intermediate water temperature is updated to determine the target intermediate water temperature, and the corresponding performance coefficient is determined based on the target intermediate water temperature. The process involves iteratively updating the intermediate water temperature and determining the corresponding performance coefficients. When the difference between the intermediate water temperature corresponding to the K+1 reel and the intermediate water temperature corresponding to the K reel is less than a preset value, the intermediate water temperature corresponding to the K+1 reel is taken as the target temperature; where K is an integer greater than 1.

6. The cascade heat pump system according to any one of claims 1-5, characterized in that, The controller is configured to: Using the target temperature as the heat exchange target of the low-temperature refrigerant zone, the opening adjustment amount of the control valve is determined based on the difference between the current heat exchange temperature of the low-temperature refrigerant zone and the target temperature. The target opening is determined based on the opening adjustment amount.

7. The cascade heat pump system according to claim 6, characterized in that, The controller is configured to: Using the target temperature as the heat exchange target of the low-temperature refrigerant zone, an adjustment model for the control valve is constructed; The difference between the current heat exchange temperature of the low-temperature refrigerant region and the target temperature is used as the input of the adjustment model to obtain the opening adjustment amount output by the adjustment model.

8. The cascade heat pump system according to claim 7, characterized in that, The type of refrigerant in the low-temperature refrigerant zone is different from that in the high-temperature refrigerant zone.

9. A control method for a cascade heat pump system, characterized in that, The cascade heat pump system includes: Outdoor unit; Cascaded water module; the cascaded water module includes: Evaporator-condenser; compressor; Gas-liquid separator; Control valve; A heat exchanger, the heat exchanger comprising: The low-temperature refrigerant zone is used to heat the inlet water temperature of the heat exchanger to the target temperature; the low-temperature refrigerant zone is connected to the control valve, the evaporator-condenser and the outdoor unit to form a low-temperature refrigerant circulation loop; The high-temperature refrigerant zone is used to heat the target temperature to the outlet water temperature; the high-temperature refrigerant zone is connected in sequence to the evaporator-condenser, the gas-liquid separator and the compressor to form a high-temperature refrigerant circulation loop; The method includes: According to the target temperature, the opening degree of the control valve is adjusted to the target opening degree so that the low-temperature refrigerant zone heats the inlet water temperature of the heat exchanger to the target temperature.

10. The method according to claim 9, characterized in that, The step of adjusting the opening degree of the control valve to the target opening degree according to the target temperature includes: The target temperature for heat exchange in the low-temperature refrigerant zone is determined based on the outlet water temperature and the inlet water temperature. The target opening degree of the control valve is determined based on the target temperature, and the opening degree of the control valve is adjusted to the target opening degree.

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