A cascade high temperature heat pump control method and device

Abstract

The present invention discloses a cascade high-temperature heat pump control method and device, which obtains the current temperature difference; if the current temperature difference is within the preset temperature difference range, the current working condensing pressure in the high-temperature heat pump system is obtained as the ideal condensing pressure; if the current temperature difference is not within the preset temperature difference range, the ideal condensing pressure is determined until the current temperature difference is within the preset temperature difference range; PI control is performed to determine the target condensing pressure until the current temperature difference is within the ideal temperature difference range; the low-temperature medium evaporation pressure of the low-temperature working medium in the low-temperature heat pump system is determined; the intermediate temperature is calculated; and the high-temperature system expansion valve in the high-temperature heat pump system is adjusted according to the intermediate temperature. The method of the present invention can realize the speed adjustment control of the high-temperature compressor alone, the speed adjustment control of the low-temperature compressor alone, and the adjustment of the high-temperature system expansion valve alone, which solves the technical problem of the cascade heat pump system in the prior art that is easy to cause overshoot and oscillation during the temperature control process.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pump control, and in particular to a cascade high-temperature heat pump control method and device. Background Art

[0002] At present, the demand for high-temperature heat in industrial fields such as energy storage, industrial drying, and aquaculture is increasing year by year. In the context of responding to the global energy crisis and environmental challenges, high-temperature heat pump technology has become a hot spot for research and application due to its high efficiency, energy saving and environmental protection characteristics. Among them, the cascade high-temperature heat pump decomposes a large temperature difference range into two or more smaller temperature difference intervals. Each interval uses a refrigerant suitable for its own temperature range, and realizes step-by-step heat transfer through interconnected evaporative condensers.

[0003] Traditional switch control and PID control have been widely used for a long time due to their simplicity and practicality. However, in the use of high-temperature heat pumps, the system actuator action not only changes with user needs, but is also affected by many external conditions. The existing cascade heat pump system operation process is highly nonlinear, has a large time lag and is affected by multiple factors at the same time. In the process of adjusting and controlling temperature, there are technical problems such as overshoot and oscillation that are easy to cause.

[0004] In view of this, it is necessary to propose a cascade high-temperature heat pump control method and device to solve or at least partially solve the above technical problems. Summary of the invention

[0005] The main purpose of the present invention is to provide a cascade high-temperature heat pump control method and device, aiming to solve the technical problem in the prior art that the cascade heat pump system is prone to overshoot and oscillation during the temperature control process.

[0006] To achieve the above object, the present invention provides a cascade high temperature heat pump control method, comprising the steps of:

[0007] S10, obtaining the current temperature difference between the output temperature of the target fluid and the ideal temperature;

[0008] S20, determining whether the current temperature difference is within a preset temperature difference range;

[0009] S31, if the current temperature difference is within the preset temperature difference range, obtaining the current working condensing pressure in the high temperature heat pump system as the ideal condensing pressure;

[0010] S32: If the current temperature difference is not within the preset temperature difference range, the high temperature medium saturation pressure and minimum condensing pressure of high temperature medium The ideal condensing pressure is determined by using a dichotomy method until the current temperature difference is within the preset temperature difference range;

[0011] S40, performing PI control on the condensing pressure based on the ideal condensing pressure and the current temperature difference to determine the target condensing pressure until the current temperature difference is within the ideal temperature difference range;

[0012] S50, determining the low-temperature medium evaporation pressure of the low-temperature working medium in the low-temperature heat pump system according to the current ambient temperature of the low-temperature heat pump system ;

[0013] S60, using the formula:

[0014] Calculate the intermediate temperature, where , ;

[0015] in, is the intermediate temperature, is the high temperature medium condensation temperature of the high temperature working medium, is the low-temperature evaporation temperature of the low-temperature working medium, η L is the thermodynamic perfection of the low-temperature heat pump, η H is the thermodynamic perfection of the high-temperature heat pump, is the heat transfer temperature difference, is the constant pressure specific heat capacity of the fluid medium, is the flow rate of the target fluid, is the ideal temperature of the target fluid, is the inlet temperature of the target fluid, is the compression power consumption of the high temperature heat pump, is the compression power consumption of the low-temperature heat pump, among which the condensation temperature of the high-temperature medium Corresponding to the target condensing pressure, the evaporation temperature of the low-temperature medium Evaporation pressure of low temperature medium correspond;

[0016] S70, adjusting a high temperature system expansion valve in the high temperature stage heat pump system according to the intermediate temperature.

[0017] Further, step S32 specifically includes:

[0018] S321, if the current temperature difference is not within the preset temperature difference range, obtain the high temperature medium saturation pressure of the high temperature working medium in the high temperature stage heat pump system , obtain the minimum condensing pressure of the high-temperature medium in the high-temperature working medium of the high-temperature heat pump system ;

[0019] S322, using formula Get the current initial value of the condensing pressure ;

[0020] S323, determine the current initial value of the condensing pressure Check whether the current temperature difference is within the preset temperature difference range;

[0021] S324, if the condensing pressure is currently set to the initial value If the current temperature difference is within the preset temperature difference range, the current initial value of the condensing pressure is determined. is the ideal condensing pressure;

[0022] S325, if the condensing pressure is currently set to the initial value If the current temperature difference is not within the preset temperature difference range, the condensing pressure is judged to be the current initial value. Check whether the current outlet water temperature is higher than the ideal temperature;

[0023] S326, if the condensing pressure is currently set to the initial value If the current outlet water temperature is higher than the ideal temperature, the condensing pressure is set to the initial value. Updated to high temperature medium saturation pressure , and enter step S322 based on the minimum condensing pressure of the high temperature medium And the updated high temperature medium saturation pressure Re-obtain the current initial value of the condensing pressure ;

[0024] S327, if the condensing pressure is currently set to the initial value When the current outlet water temperature is lower than the ideal temperature, the condensing pressure is set to the initial value. Updated to the minimum condensing pressure of low temperature medium , and enter step S322 based on the high temperature medium saturation pressure And updated minimum condensing pressure of high temperature media Re-obtain the current initial value of the condensing pressure ;

[0025] Repeat steps S322 to S325 until the ideal condensing pressure is obtained.

[0026] Using formula Calculate the temperature difference at the narrow point and obtain Assumed condensation temperature , and then determine the assumed condensation temperature is the minimum condensation temperature of the high temperature medium ;

[0027] in, is the refrigerant flow rate, For the narrow temperature difference, is the constant pressure specific heat capacity of the fluid, is the flow rate of the target fluid, is the ideal temperature of the target fluid, is the inlet temperature of the target fluid, is the target outlet enthalpy of the high temperature system condenser, is the target inlet enthalpy of the high temperature system condenser, is the enthalpy of the refrigerant at the bubble point of the high-temperature condenser, is the enthalpy of the refrigerant at the outlet of the high-temperature condenser;

[0028] According to the refrigerant physical property model, obtain the minimum condensation temperature of high temperature medium Corresponding minimum condensing pressure of high temperature medium .

[0029] Furthermore, the rotation speed of the high temperature system compressor in the high temperature stage heat pump system is determined by PI control according to the target condensing pressure.

[0030] Furthermore, according to the condensation temperature of the high temperature medium PI control is used to determine the working pressure of the high temperature system expansion valve.

[0031] Furthermore, the rotation speed of the low-temperature system compressor in the low-temperature stage heat pump system is determined by adopting PI control according to the evaporation pressure of the low-temperature medium.

[0032] Furthermore, the working pressure of the low-temperature system expansion valve is adjusted according to the outlet superheat of the low-temperature system evaporator.

[0033] Furthermore, using the formula Get the evaporation pressure of low temperature medium ,in, is the ambient temperature, is the heat exchange area of ​​the evaporator, is the evaporator type coefficient, is the heat transfer coefficient.

[0034] The present invention also provides a cascade high-temperature heat pump device, comprising a high-temperature heat pump system, a low-temperature heat pump system and a system to be heated;

[0035] The high-temperature heat pump system includes a high-temperature system condenser, a high-temperature system expansion valve and a high-temperature system compressor which are connected by a high-temperature pipeline and arranged in sequence. The high-temperature system condenser is located between the high-temperature system compressor and the high-temperature system expansion valve. The inlet and outlet ends of the high-temperature side of the high-temperature system condenser are respectively connected to the high-temperature pipeline.

[0036] The system to be heated includes a delivery pipeline and a delivery pump arranged on the delivery pipeline, and the inlet and outlet ends of the low temperature side of the high temperature system condenser are respectively connected to the delivery pipeline;

[0037] The low-temperature heat pump system includes a low-temperature system condenser evaporator, a low-temperature system expansion valve, a low-temperature system evaporator and a low-temperature system compressor which are connected by pipelines and arranged in sequence. The low-temperature system condenser evaporator is located between the low-temperature system compressor and the low-temperature system expansion valve, the low-temperature system evaporator is located between the low-temperature system expansion valve and the low-temperature system compressor, the inlet end and the outlet end of the low-temperature side of the low-temperature system condenser evaporator are respectively connected to the high-temperature pipeline, and the inlet end and the outlet end of the high-temperature side of the low-temperature system condenser evaporator are respectively connected to the low-temperature pipeline;

[0038] It also includes a monitoring sensor to be heated, which includes an outlet water temperature sensor, an inlet water temperature sensor and a water flow sensor arranged on the delivery pipeline, the inlet water temperature sensor and the water flow sensor are respectively arranged on the input side of the high temperature system condenser, and the outlet water temperature sensor is arranged on the output side of the high temperature system condenser;

[0039] It also includes a high-temperature input pressure sensor and a high-temperature output pressure sensor arranged on the high-temperature pipeline, the high-temperature input pressure sensor is arranged upstream of the high-temperature system compressor, and the high-temperature output pressure sensor is arranged downstream of the high-temperature system compressor;

[0040] It also includes a low-temperature input pressure sensor and a low-temperature output pressure sensor arranged on the low-temperature pipeline, the low-temperature input pressure sensor is arranged upstream of the low-temperature system compressor, and the low-temperature output pressure sensor is arranged upstream of the low-temperature system expansion valve;

[0041] It also includes a processing module, which is used to implement the steps of the above-mentioned cascade high-temperature heat pump control method.

[0042] Compared with the prior art, the cascade high-temperature heat pump control method provided by the present invention has the following beneficial effects:

[0043] The present invention provides a cascade high-temperature heat pump control method, which determines the current temperature difference based on the output temperature of the target fluid and the ideal temperature; determines whether the absolute value of the current temperature difference is within the preset temperature difference range; determines that the current working condensing pressure of the high-temperature heat pump system is the ideal condensing pressure when the absolute value of the current temperature difference is within the preset temperature difference range, and adopts the dichotomy method to perform rough adjustment when the absolute value of the current temperature difference is not within the preset temperature difference range until the absolute value of the current temperature difference is within the preset temperature difference range to obtain the ideal condensing pressure; performs condensing pressure PI adjustment based on the ideal condensing pressure and the current temperature difference to determine the target condensing pressure so that the current temperature difference is within the ideal temperature difference range, and realizes the speed adjustment control of the high-temperature compressor of the high-temperature heat pump system according to the current temperature difference by using the rough adjustment and fine adjustment method, which has fast convergence response and good stability, and can avoid overshoot oscillation due to the constraints of physical working conditions. The speed adjustment control of the low-temperature compressor in the low-temperature heat pump system is realized by determining the low-temperature medium evaporation pressure of the low-temperature working medium in the low-temperature heat pump system according to the current ambient temperature of the low-temperature heat pump system. By obtaining the intermediate temperature based on the high-temperature medium condensation temperature and the low-temperature medium evaporation temperature, and adjusting the high-temperature system expansion valve according to the intermediate temperature, the high-temperature medium condensation temperature and the low-temperature medium evaporation temperature can directly adjust the high-temperature system expansion valve. The cascade high-temperature heat pump control method of the present invention can achieve independent speed regulation and control of the high-temperature compressor, independent speed regulation and control of the low-temperature compressor, and independent regulation of the high-temperature system expansion valve, solving the technical problem of the cascade heat pump system in the prior art that it is easy to cause overshoot and oscillation during the temperature control process. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0045] Figure 1 It is a flow chart of the cascade high temperature heat pump control method of the present invention;

[0046] Figure 2 It is a schematic flow chart of determining the ideal condensing pressure by using the dichotomy method in the cascade high-temperature heat pump control method of the present invention;

[0047] Figure 3 It is a schematic structural diagram of the cascade high-temperature heat pump control device of the present invention.

[0048] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments.

[0049] Legend:

[0050] 10. Low temperature heat pump system; 11. Low temperature system expansion valve; 12. Low temperature system evaporator; 13. Low temperature input pressure sensor; 14. Low temperature system compressor; 15. Low temperature system condenser evaporator; 16. Low temperature output pressure sensor;

[0051] 20. High temperature heat pump system; 22. High temperature input pressure sensor; 23. High temperature system compressor; 24. High temperature output pressure sensor; 25. High temperature system condenser; 26. High temperature system expansion valve;

[0052] 30. System to be heated; 31. Delivery pump; 32. Outlet water temperature sensor; 33. Inlet water temperature sensor; 34. Water flow sensor.

[0053] in, Figure 3 The arrows in the figure indicate the direction of fluid flow. DETAILED DESCRIPTION

[0054] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0055] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0057] Please refer to Figure 1 , Figure 2 and Figure 3 , the present invention provides a cascade high-temperature heat pump control method, comprising the steps of: S10, obtaining a current temperature difference between an output temperature of a target fluid and an ideal temperature;

[0058] S20, determining whether the current temperature difference is within a preset temperature difference range;

[0059] S31, if the current temperature difference is within the preset temperature difference range, obtaining the current working condensing pressure in the high temperature heat pump system as the ideal condensing pressure;

[0060] S32: If the current temperature difference is not within the preset temperature difference range, the high temperature medium saturation pressure and minimum condensing pressure of high temperature medium The ideal condensing pressure is determined by using a dichotomy method until the current temperature difference is within the preset temperature difference range;

[0061] S40, performing PI control on the condensing pressure based on the ideal condensing pressure and the current temperature difference to determine the target condensing pressure until the current temperature difference is within the ideal temperature difference range;

[0062] S50, determining the low-temperature medium evaporation pressure of the low-temperature working medium in the low-temperature heat pump system according to the current ambient temperature of the low-temperature heat pump system ;

[0063] S60, using the formula:

[0064] Calculate the intermediate temperature, where , ;

[0065] in, is the intermediate temperature, is the high temperature medium condensation temperature of the high temperature working medium, is the low-temperature evaporation temperature of the low-temperature working medium, η L is the thermodynamic perfection of the low-temperature heat pump, η H is the thermodynamic perfection of the high-temperature heat pump, is the heat transfer temperature difference, is the constant pressure specific heat capacity of the fluid medium, is the flow rate of the target fluid, is the ideal temperature of the target fluid, is the inlet temperature of the target fluid, is the compression power consumption of the high temperature heat pump, is the compression power consumption of the low-temperature heat pump, among which the condensation temperature of the high-temperature medium Corresponding to the target condensing pressure, the evaporation temperature of the low-temperature medium Evaporation pressure of low temperature medium correspond;

[0066] S70, adjusting a high temperature system expansion valve in the high temperature stage heat pump system according to the intermediate temperature.

[0067] The present invention provides a cascade high-temperature heat pump control method, which determines the current temperature difference based on the output temperature of the target fluid and the ideal temperature; determines whether the absolute value of the current temperature difference is within the preset temperature difference range; determines that the current working condensing pressure of the high-temperature heat pump system is the ideal condensing pressure when the absolute value of the current temperature difference is within the preset temperature difference range, and adopts the dichotomy method to perform rough adjustment when the absolute value of the current temperature difference is not within the preset temperature difference range until the absolute value of the current temperature difference is within the preset temperature difference range to obtain the ideal condensing pressure; performs condensing pressure PI adjustment based on the ideal condensing pressure and the current temperature difference to determine the target condensing pressure so that the current temperature difference is within the ideal temperature difference range, and realizes the speed adjustment control of the high-temperature compressor of the high-temperature heat pump system according to the current temperature difference by using the rough adjustment and fine adjustment method, which has fast convergence response and good stability, and can avoid overshoot oscillation due to the constraints of physical working conditions. The speed adjustment control of the low-temperature compressor in the low-temperature heat pump system is realized by determining the low-temperature medium evaporation pressure of the low-temperature working medium in the low-temperature heat pump system according to the current ambient temperature of the low-temperature heat pump system. By obtaining the intermediate temperature based on the high-temperature medium condensation temperature and the low-temperature medium evaporation temperature, and adjusting the high-temperature system expansion valve according to the intermediate temperature, the high-temperature medium condensation temperature and the low-temperature medium evaporation temperature can directly adjust the high-temperature system expansion valve. The cascade high-temperature heat pump control method of the present invention can achieve independent speed regulation and control of the high-temperature compressor, independent speed regulation and control of the low-temperature compressor, and independent regulation of the high-temperature system expansion valve, solving the technical problem of the cascade heat pump system in the prior art that it is easy to cause overshoot and oscillation during the temperature control process.

[0068] It is understandable that when judging whether the current temperature difference is within the preset temperature difference range, the preset temperature difference range can be set to [-A, A], A is a positive number, and then judging whether the current temperature difference belongs to [-A, A] to judge whether the current temperature difference is within the preset temperature difference range; it is also possible to set the preset temperature difference value to A, A is a positive number, and then judging whether the absolute value of the current temperature difference is within the preset temperature difference range to judge whether the current temperature difference is within the preset temperature difference range. It is understandable that when judging whether the current temperature difference is within the ideal temperature difference range, the ideal temperature difference range can be set to [-B, B], B is a positive number, and then judging whether the current temperature difference belongs to [-B, B] to judge whether the current temperature difference is within the ideal temperature difference range; it is also possible to set the ideal temperature difference value to B, B is a positive number, and then judging whether the absolute value of the current temperature difference is greater than the ideal temperature difference value to judge whether the current temperature difference is within the ideal temperature difference range. In the present invention, in order to achieve stable regulation and control, the ideal temperature difference range is within the preset temperature difference range.

[0069] It can be understood that according to the saturation pressure of the high temperature medium P CSE and high temperature medium minimum condensing pressure Pcmin determines the ideal condensing pressure, wherein the current temperature difference under the ideal condensing pressure is within the preset temperature difference range; based on the ideal condensing pressure and the current temperature difference, the condensing pressure is PI controlled and adjusted to determine the target condensing pressure, wherein the current temperature difference under the target condensing pressure is within the ideal temperature difference range, in the present invention, the current temperature difference is made within the preset temperature difference range by coarse adjustment, and the current temperature difference is further made within the ideal temperature difference range by fine adjustment. Optionally, the target fluid is water fluid.

[0070] It can be understood that when obtaining the intermediate temperature, the high temperature medium condensation temperature is determined according to the target condensation pressure. , according to the evaporation temperature of low temperature medium Determine the evaporation pressure of low temperature medium , according to the current environment, high temperature medium condensation temperature and low temperature medium evaporation temperature Determine the intermediate temperature.

[0071] Optionally, in the present invention, methods for determining the ideal condensing pressure include bisection method, Lagrange number multiplication method, Newton method, tangent method, secant method and heuristic algorithm; parameter setting methods in PI control (integral-differential control) include critical proportionality method, attenuation curve method, and relay feedback setting method.

[0072] Furthermore, the present invention adopts a dichotomy method to determine the ideal condensing pressure, and step S32 specifically includes:

[0073] S321, if the current temperature difference is not within the preset temperature difference range, obtain the high temperature medium saturation pressure of the high temperature working medium in the high temperature stage heat pump system , obtain the minimum condensing pressure of the high-temperature medium in the high-temperature working medium of the high-temperature heat pump system ;

[0074] S322, using formula Get the current initial value of the condensing pressure ;

[0075] S323, determine the current initial value of the condensing pressure Check whether the current temperature difference is within the preset temperature difference range;

[0076] S324, if the condensing pressure is currently set to the initial value If the current temperature difference is within the preset temperature difference range, the current initial value of the condensing pressure is determined. is the ideal condensing pressure;

[0077] S325, if the condensing pressure is currently set to the initial value If the current temperature difference is not within the preset temperature difference range, the condensing pressure is judged to be the current initial value. Check whether the current outlet water temperature is higher than the ideal temperature;

[0078] S326, if the condensing pressure is currently set to the initial value If the current outlet water temperature is higher than the ideal temperature, the condensing pressure is set to the initial value. Updated to high temperature medium saturation pressure , and enter step S322 based on the minimum condensing pressure of the high temperature medium And the updated high temperature medium saturation pressure Re-obtain the current initial value of the condensing pressure ;

[0079] S327, if the condensing pressure is currently set to the initial value When the current outlet water temperature is lower than the ideal temperature, the condensing pressure is set to the initial value. Updated to the minimum condensing pressure of low temperature medium , and enter step S322 based on the high temperature medium saturation pressure And updated minimum condensing pressure of high temperature media Re-obtain the current initial value of the condensing pressure ;

[0080] Repeat steps S322 to S325 until the ideal condensing pressure is obtained.

[0081] In the specific implementation, the high-temperature medium saturation pressure of the high-temperature working medium in the high-temperature heat pump system is obtained. , obtain the minimum condensing pressure of the high-temperature medium in the high-temperature working medium of the high-temperature heat pump system ; Using the formula Get the current initial value of the condensing pressure ; Determine the current initial value of the condensing pressure Check whether the current temperature difference is within the preset temperature difference range. If the condensing pressure is currently set to the initial value, If the absolute value of the current temperature difference is within the preset temperature difference range, the current initial value of the condensing pressure is determined. is the ideal condensing pressure; if the condensing pressure is currently set to the initial value The current temperature difference is not within the preset temperature difference range, and the condensing pressure is currently set to the initial value. When the current outlet water temperature is higher than the ideal temperature, the condensing pressure in step S322 is set to the initial value. As the initial value for optimization, the condensing pressure setting value is optimized by using the dichotomy method (for example, when the measured value of the outlet water temperature is higher than the target value of the outlet water temperature, the condensing pressure is re-proposed , the proposed condensing pressure As the initial value of the condensing pressure in step S322, the process proceeds to step S323; if the initial value of the condensing pressure is currently set If the current temperature difference is not within the preset temperature difference range, and the measured value of the outlet water temperature is less than the target value of the outlet water temperature, the condensing pressure in step S322 is set to the initial value. As the initial value for optimization, the condensing pressure setting value is optimized by using the dichotomy method. (For example, when the measured value of the outlet water temperature is less than the target value of the outlet water temperature, the condensing pressure is re-proposed. , the proposed condensing pressure The initial value of the condensing pressure in step S322 is currently set and the process proceeds to step S323; the above steps are repeated using the binary method until the ideal condensing pressure is obtained.

[0082] Furthermore, using the formula Calculate the temperature difference at the narrow point and obtain Assumed condensation temperature , and then determine the assumed condensation temperature is the minimum condensation temperature of the high temperature medium ;

[0083] in, is the refrigerant flow rate, For the narrow temperature difference, is the constant pressure specific heat capacity of the fluid, is the flow rate of the target fluid, is the ideal temperature of the target fluid, is the inlet temperature of the target fluid, is the target outlet enthalpy of the high temperature system condenser, is the target inlet enthalpy of the high temperature system condenser, is the enthalpy of the refrigerant at the bubble point of the high-temperature condenser, is the enthalpy of the refrigerant at the outlet of the high-temperature condenser;

[0084] According to the refrigerant physical property model, obtain the minimum condensation temperature of high temperature medium Corresponding minimum condensing pressure of high temperature medium .

[0085] Further, the rotation speed of the high temperature system compressor in the high temperature stage heat pump system is determined by PI control according to the target condensing pressure. It can be understood that PI control mainly includes proportional control and integral control.

[0086] Furthermore, according to the condensation temperature of the high temperature medium Determine the operating pressure of the high temperature system expansion valve.

[0087] Furthermore, according to the condensation temperature of the high temperature medium PI control is used to determine the working pressure of the high temperature system expansion valve.

[0088] Furthermore, the rotation speed of the low-temperature system compressor in the low-temperature stage heat pump system is determined by adopting PI control according to the evaporation pressure of the low-temperature medium.

[0089] Furthermore, the working pressure of the low-temperature system expansion valve is adjusted according to the outlet superheat of the low-temperature system evaporator.

[0090] Furthermore, using the formula Get the evaporation pressure of low temperature medium ,in, is the ambient temperature, is the heat exchange area of ​​the evaporator, is the evaporator type coefficient, In the present invention, the evaporator heat exchange area, evaporator type coefficient and heat exchange system data are identified offline. For a low-temperature heat pump system using R1234yf as a working fluid, .

[0091] Furthermore, the outlet superheat of the low-temperature system evaporator 12 is adjusted.

[0092] The control method of the cascade high-temperature heat pump of the present invention relies on cascade control for the outlet water temperature control mode. After the current temperature difference is roughly adjusted to be within the preset temperature difference range, fine adjustment is used to further make the current temperature difference within the ideal temperature difference range. The physical mechanism rough adjustment is combined with the PI control fine adjustment, which has strong robustness, fast response speed and strong anti-interference ability. The evaporation pressure of the low-temperature medium is determined based on the physical mechanism, which can realize accurate and efficient heat extraction of the heat pump and realize the decoupling of multiple operating parameters. The intermediate temperature is obtained by collecting operating data online, identifying model parameters, and outputting the optimal intermediate temperature based on the physical model, taking into account both model accuracy and interpretability.

[0093] The present invention also provides a cascade high-temperature heat pump device, comprising a high-temperature heat pump system 20, a low-temperature heat pump system 10 and a system to be heated 30;

[0094] The high-temperature heat pump system includes a high-temperature system condenser 25, a high-temperature system expansion valve 26 and a high-temperature system compressor 23 which are connected and arranged in sequence through a high-temperature pipeline. The high-temperature system condenser 25 is located between the high-temperature system compressor 23 and the high-temperature system expansion valve 26. The inlet and outlet ends of the high-temperature side of the high-temperature system condenser 25 are respectively connected to the high-temperature pipeline.

[0095] The system to be heated includes a delivery pipeline and a delivery pump 31 arranged on the delivery pipeline, and the inlet and outlet ends of the low temperature side of the high temperature system condenser 25 are respectively connected to the delivery pipeline;

[0096] The low-temperature heat pump system includes a low-temperature system condenser evaporator 15, a low-temperature system expansion valve 11, a low-temperature system evaporator 12 and a low-temperature system compressor 14 which are connected by pipelines and arranged in sequence. The low-temperature system condenser evaporator 15 is located between the low-temperature system compressor 14 and the low-temperature system expansion valve 11, and the low-temperature system evaporator 12 is located between the low-temperature system expansion valve 11 and the low-temperature system compressor 14. The inlet end and the outlet end of the low-temperature side of the low-temperature system condenser evaporator 15 are respectively connected to the high-temperature pipeline, and the inlet end and the outlet end of the high-temperature side of the low-temperature system condenser evaporator 15 are respectively connected to the low-temperature pipeline;

[0097] It also includes a monitoring sensor to be heated, which includes an outlet water temperature sensor 32, an inlet water temperature sensor 33 and a water flow sensor 34 arranged on the delivery pipeline, the inlet water temperature sensor and the water flow sensor are respectively arranged on the input side of the high temperature system condenser 25, and the outlet water temperature sensor is arranged on the output side of the high temperature system condenser 25;

[0098] It also includes a high temperature input pressure sensor 22 and a high temperature output pressure sensor 24 arranged on the high temperature pipeline, the high temperature input pressure sensor is arranged upstream of the high temperature system compressor 23, and the high temperature output pressure sensor is arranged downstream of the high temperature system compressor 23;

[0099] It also includes a low-temperature input pressure sensor 13 and a low-temperature output pressure sensor 19 arranged on the low-temperature pipeline, the low-temperature input pressure sensor is arranged upstream of the low-temperature system compressor 14, and the low-temperature output pressure sensor is arranged upstream of the low-temperature system expansion valve 11;

[0100] It also includes a processing module, which is used to implement the steps of the upper cascade high-temperature heat pump control method.

[0101] It can be understood that the processing module in the present invention includes a temperature difference acquisition module, a high-temperature system condensing pressure coarse adjustment module, a high-temperature system condensing pressure fine adjustment module, an intermediate temperature control module and an evaporation pressure control module, wherein the temperature difference acquisition module, the temperature difference acquisition module is used to obtain the current temperature difference and determine whether the current temperature difference is within the preset temperature difference range, the high-temperature system condensing pressure coarse adjustment module is used to adjust the pressure to the ideal condensing pressure when the current temperature difference is not within the preset temperature difference range, until the current temperature difference is within the preset temperature difference range, the high-temperature system condensing pressure fine adjustment module is used to adjust the pressure to the target condensing pressure when the current temperature difference is within the preset temperature difference range, so that the current temperature difference under the target condensing pressure is within the ideal temperature difference range, the intermediate temperature control module is used to obtain the intermediate temperature, and adjust the high-temperature system expansion valve according to the intermediate temperature, and the evaporation pressure control module is used to determine the evaporation pressure of the low-temperature medium according to the current environment .

[0102] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A cascade high temperature heat pump control method, characterized in that: Includes steps: S10, obtaining the current temperature difference between the output temperature of the target fluid and the ideal temperature; S20, determining whether the current temperature difference is within a preset temperature difference range; S31, if the current temperature difference is within the preset temperature difference range, obtaining the current working condensing pressure in the high temperature heat pump system as the ideal condensing pressure; S32, if the current temperature difference is not within the preset temperature difference range, and minimum condensing pressure of high temperature medium Determine the ideal condensing pressure by using a dichotomy method until the current temperature difference is within a preset temperature difference range; S40, performing PI control on the condensing pressure based on the ideal condensing pressure and the current temperature difference to determine a target condensing pressure until the current temperature difference is within the ideal temperature difference range; S50, determining the low-temperature medium evaporation pressure of the low-temperature working medium in the low-temperature heat pump system according to the current ambient temperature of the low-temperature heat pump system ; S60, using the formula: Calculate the intermediate temperature, where , ; in, is the intermediate temperature, is the high temperature medium condensation temperature of the high temperature working medium, is the low-temperature evaporation temperature of the low-temperature working medium, η L is the thermodynamic perfection of the low-temperature heat pump, η H is the thermodynamic perfection of the high-temperature heat pump, is the heat transfer temperature difference, is the constant pressure specific heat capacity of the fluid medium, is the flow rate of the target fluid, is the ideal temperature of the target fluid, is the inlet temperature of the target fluid, is the compression power consumption of the high temperature heat pump, is the compression power consumption of the low-temperature heat pump, among which the condensation temperature of the high-temperature medium Corresponding to the target condensing pressure, the evaporation temperature of the low-temperature medium The evaporation pressure of the low temperature medium correspond, is the assumed condensation temperature; S70, adjusting a high-temperature system expansion valve in a high-temperature stage heat pump system according to the intermediate temperature.

2. The cascade high temperature heat pump control method according to claim 1, characterized in that: Step S32 specifically includes: S321, if the current temperature difference is not within the preset temperature difference range, obtain the high-temperature medium saturation pressure of the high-temperature working medium in the high-temperature heat pump system , obtain the minimum condensing pressure of the high-temperature medium in the high-temperature working medium of the high-temperature heat pump system ; S322, using formula Get the current initial value of the condensing pressure ; S323, determine the current initial value of the condensing pressure Check whether the current temperature difference is within the preset temperature difference range; S324, if the condensing pressure is currently set to the initial value If the current temperature difference is within the preset temperature difference range, the current initial value of the condensing pressure is determined. is the ideal condensing pressure; S325, if the condensing pressure is currently set to the initial value If the current temperature difference is not within the preset temperature difference range, the condensing pressure is judged to be the current initial value. Check whether the current outlet water temperature is higher than the ideal temperature; S326, if the condensing pressure is currently set to the initial value If the current outlet water temperature is higher than the ideal temperature, the condensing pressure is set to the initial value. Updated to high temperature medium saturation pressure , and enter step S322 based on the minimum condensing pressure of the high temperature medium And the updated high temperature medium saturation pressure Re-obtain the current initial value of the condensing pressure ; S327, if the condensing pressure is currently set to the initial value When the current outlet water temperature is lower than the ideal temperature, the condensing pressure is set to the initial value. Updated to the minimum condensing pressure of low temperature medium , and enter step S322 based on the high temperature medium saturation pressure And updated minimum condensing pressure of high temperature media Re-obtain the current initial value of the condensing pressure ; Repeat steps S322 to S325 until the ideal condensing pressure is obtained.

3. The cascade high temperature heat pump control method according to claim 1, characterized in that: Using formula Calculate the refrigerant flow rate of high temperature working medium in high temperature heat pump system; Using formula Calculate the temperature difference at the narrow point and obtain Assumed condensation temperature , and then determine the assumed condensation temperature Minimum condensation temperature of high temperature medium ; in, is the refrigerant flow rate, For the narrow temperature difference, is the constant pressure specific heat capacity of the fluid, is the flow rate of the target fluid, is the ideal temperature of the target fluid, is the inlet temperature of the target fluid, is the target outlet enthalpy of the high temperature system condenser, is the target inlet enthalpy of the high temperature system condenser, is the enthalpy of the refrigerant at the bubble point of the high-temperature condenser, is the enthalpy of the refrigerant at the outlet of the high-temperature condenser; According to the refrigerant physical property model, obtain the minimum condensation temperature of high temperature medium Corresponding minimum condensing pressure of high temperature medium .

4. The cascade high temperature heat pump control method according to claim 1, characterized in that: The speed of the high temperature system compressor in the high temperature stage heat pump system is determined by PI control according to the target condensing pressure.

5. The cascade high temperature heat pump control method according to claim 1, characterized in that: According to the condensation temperature of high temperature medium T c Use PI control to determine the working pressure of the high temperature system expansion valve.

6. The cascade high temperature heat pump control method according to claim 1, characterized in that: The speed of the low-temperature system compressor in the low-temperature stage heat pump system is determined by PI control according to the evaporation pressure of the low-temperature medium.

7. The cascade high temperature heat pump control method according to claim 1, characterized in that: Adjust the working pressure of the low-temperature system expansion valve according to the outlet superheat of the low-temperature system evaporator.

8. The cascade high temperature heat pump control method according to claim 1, characterized in that: Using formula Get the evaporation pressure of low temperature medium ,in, is the ambient temperature, is the heat exchange area of ​​the evaporator, is the evaporator type coefficient, is the heat transfer coefficient.

9. A cascade high temperature heat pump device, characterized in that: Including high-temperature heat pump system, low-temperature heat pump system and system to be heated; The high-temperature heat pump system comprises a high-temperature system condenser, a high-temperature system expansion valve and a high-temperature system compressor which are connected by a high-temperature pipeline and arranged in sequence, the high-temperature system condenser is located between the high-temperature system compressor and the high-temperature system expansion valve, and the inlet and outlet ends of the high-temperature side of the high-temperature system condenser are respectively connected to the high-temperature pipeline; The system to be heated includes a delivery pipeline and a delivery pump arranged on the delivery pipeline, and the inlet and outlet of the low temperature side of the high temperature system condenser are respectively connected to the delivery pipeline; The low-temperature heat pump system comprises a low-temperature system condenser evaporator, a low-temperature system expansion valve, a low-temperature system evaporator and a low-temperature system compressor which are connected by pipelines and arranged in sequence, the low-temperature system condenser evaporator is located between the low-temperature system compressor and the low-temperature system expansion valve, the low-temperature system evaporator is located between the low-temperature system expansion valve and the low-temperature system compressor, the inlet end and the outlet end of the low-temperature side of the low-temperature system condenser evaporator are respectively connected to the high-temperature pipeline, and the inlet end and the outlet end of the high-temperature side of the low-temperature system condenser evaporator are respectively connected to the low-temperature pipeline; It also includes a monitoring sensor to be heated, which includes an outlet water temperature sensor, an inlet water temperature sensor and a water flow sensor arranged on the delivery pipeline, the inlet water temperature sensor and the water flow sensor are respectively arranged on the input side of the high temperature system condenser, and the outlet water temperature sensor is arranged on the output side of the high temperature system condenser; It also includes a high-temperature input pressure sensor and a high-temperature output pressure sensor disposed on the high-temperature pipeline, wherein the high-temperature input pressure sensor is disposed upstream of the high-temperature system compressor, and the high-temperature output pressure sensor is disposed downstream of the high-temperature system compressor; It also includes a low-temperature input pressure sensor and a low-temperature output pressure sensor disposed on the low-temperature pipeline, wherein the low-temperature input pressure sensor is disposed upstream of the low-temperature system compressor, and the low-temperature output pressure sensor is disposed upstream of the low-temperature system expansion valve; It also includes a processing module, which is used to implement the steps of the cascade high-temperature heat pump control method according to any one of claims 1 to 8.

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