CN116817485A - Double-stage compression heat pump system, load and unload control method and control system - Google Patents
Double-stage compression heat pump system, load and unload control method and control system Download PDFInfo
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Abstract
一种双级压缩热泵系统、加减载控制方法及控制系统，热泵系统包括低压级压缩机与高压级压缩机，通过控制器同时对低压级压缩机与高压级压缩机的转速进行调节，实现对冷凝器出水温度的调节；单独对高压级压缩机的转速进行调节，实现对低压级压缩机与高压级压缩机之间的级间压力进行调节。通过采集实际冷凝器出口水温、低压级压缩机转速、高压级压缩机转速；基于设定冷凝器出口水温与实际冷凝器出口水温差值对低压级压缩机转速进行调节，同时对高压级压缩机转速等比例进行调节；采集低压级吸气压力、高压级排气压力、级间压力；基于最优级间压力与实际级间压力差值对高压级压缩机转速进行调节。本发明提高了热泵系统运行的能效水平以及安全性。
A two-stage compression heat pump system, load addition and reduction control method and control system. The heat pump system includes a low-pressure stage compressor and a high-pressure stage compressor. The controller simultaneously adjusts the rotation speeds of the low-pressure stage compressor and the high-pressure stage compressor to achieve Adjust the condenser outlet water temperature; separately adjust the speed of the high-pressure stage compressor to adjust the interstage pressure between the low-pressure stage compressor and the high-pressure stage compressor. By collecting the actual condenser outlet water temperature, low-pressure stage compressor speed, and high-pressure stage compressor speed; based on the difference between the set condenser outlet water temperature and the actual condenser outlet water temperature, the low-pressure stage compressor speed is adjusted, while the high-pressure stage compressor The rotation speed is adjusted proportionally; the low-pressure stage suction pressure, high-pressure stage exhaust pressure, and inter-stage pressure are collected; the high-pressure stage compressor speed is adjusted based on the difference between the optimal inter-stage pressure and the actual inter-stage pressure. The invention improves the energy efficiency level and safety of the heat pump system operation.
Description
Technical Field
The application belongs to the technical field of heat pumps, and relates to a two-stage compression heat pump system, an load and unload control method and a control system.
Background
When the heating amount is the same, the power consumption of the heat pump is only one fifth of that of the traditional equipment, so that the heat pump system is widely applied to various fields. In some application scenarios, the heat pump system needs to operate under a large temperature difference condition. Because of the large temperature difference, the heating capacity and energy efficiency of the traditional single-stage compression heat pump system are reduced, and the exhaust temperature of a compressor in the system is also higher.
The principle of the two-stage compression technology is to divide a compression process into two processes of high and low pressure stages for compression so as to reduce the pressure difference born by each stage. By reducing the pressure difference and matching with the inter-stage economizer for air supplementing, the two-stage compression technology can effectively improve the heating capacity and energy efficiency of the heat pump system under the working condition of large temperature difference.
In order to improve the energy efficiency level and the adjustment capability of a compressor in a heat pump system, a variable frequency motor is gradually applied to the heat pump system. In a double-stage compression heat pump system with double variable frequency motors, the rotational speed of the high-pressure stage compressor and the rotational speed of the low-pressure stage compressor can be changed, so that the outlet water temperature of the condenser can be controlled by adjusting the rotational speed of the compressors. But the high and low pressure stage inter-stage pressures will change as the speed ratio of the high and low stage compressors changes. Inter-stage pressure is an important operating parameter of a two-stage compression heat pump system, affecting the energy efficiency and oil supply capacity of the heat pump system. Under different operating conditions, the optimal interstage pressure with the lowest operating energy consumption is different. In order to better increase the energy efficiency level of the two-stage compression heat pump system, besides adjusting the outlet water temperature of the condenser, the interstage pressure needs to be adjusted.
Disclosure of Invention
The application aims to solve the problems in the prior art, and provides a two-stage compression heat pump system, an acceleration and deceleration control method and a control system, so that the heat pump system has the capacity of adjusting the outlet water temperature of a condenser and the interstage pressure, and the heat pump system can be more energy-saving and safer while the capacity of adjusting the heat pump system is ensured.
In order to achieve the above purpose, the present application has the following technical scheme:
a two-stage compression heat pump system comprises a low-pressure stage compressor and a high-pressure stage compressor, wherein the rotation speeds of the low-pressure stage compressor and the high-pressure stage compressor are simultaneously regulated by a controller, so that the regulation of the outlet water temperature of a condenser is realized; the rotating speed of the high-pressure stage compressor is independently adjusted through the controller, so that the inter-stage pressure between the low-pressure stage compressor and the high-pressure stage compressor is adjusted.
As a preferable scheme, the low-pressure stage compressor and the high-pressure stage compressor are respectively controlled by respective variable frequency motors in rotation speed, the first PID controller is used for receiving the real-time collected condenser water outlet temperature data, simultaneously adjusting the rotation speeds of the low-pressure stage compressor and the high-pressure stage compressor, the second PID controller is used for receiving the real-time collected interstage pressure data between the low-pressure stage compressor and the high-pressure stage compressor, and independently adjusting the rotation speed of the high-pressure stage compressor.
As a preferable scheme, the outlet of the low-pressure stage compressor is connected with the inlet of the high-pressure stage compressor, the outlet of the high-pressure stage compressor is connected with the inlet of the oil-gas separator, the outlet of the gas path of the oil-gas separator is connected with the inlet of the pressure maintaining valve, and the outlet of the pressure maintaining valve is connected with the inlet of the condenser.
As a preferable scheme, an oil way outlet of the oil-gas separator is connected with an inlet of an oil cooler, an outlet of the oil cooler is connected with an inlet of an oil quantity control valve, and an outlet of the oil quantity control valve is connected with an oil injection port of the high-pressure stage compressor.
As a preferable scheme, the outlet of the condenser is connected with the inlet of the first passage of the intercooler through a main passage, the outlet of the first passage of the intercooler is connected with the inlet of the main passage expansion valve, the outlet of the main passage expansion valve is connected with the inlet of the evaporator, and the outlet of the evaporator is connected with the inlet of the low-pressure stage compressor.
As a preferable scheme, the outlet of the condenser is connected with the inlet of the air supplementing branch expansion valve through the air supplementing branch, the outlet of the air supplementing branch expansion valve is connected with the inlet of the second passage of the intercooler, the outlet of the second passage of the intercooler is connected with the inlet of the one-way valve, and the outlet of the one-way valve is connected with the outlet of the low-pressure stage compressor.
An load and unload control method of a two-stage compression heat pump system comprises the following steps:
setting a target outlet water temperature of the condenser;
collecting the actual outlet water temperature of a condenser, the rotating speed of a low-pressure stage compressor and the rotating speed of a high-pressure stage compressor;
based on the difference value between the target water outlet temperature of the condenser and the actual water outlet temperature of the condenser, the rotating speed of the low-pressure stage compressor is regulated, and the rotating speed of the high-pressure stage compressor is regulated in equal proportion;
and collecting the suction pressure of the low-pressure stage compressor, the discharge pressure of the high-pressure stage compressor and the interstage pressure, and adjusting the rotating speed of the high-pressure stage compressor based on the difference value between the optimal interstage pressure and the actual interstage pressure calculated by the suction pressure and the discharge pressure.
As a preferred embodiment, the calculation expression of the optimal inter-stage pressure is as follows:
wherein C is a correction coefficient; p (P) in Suction pressure for the low pressure stage compressor; p (P) out Is the discharge pressure of the high-pressure stage compressor.
As a preferable scheme, the actual outlet water temperature of the condenser, the rotating speed of the low-pressure stage compressor and the rotating speed of the high-pressure stage compressor are collected when the judging system is in a stable running state, and the conditions for judging the system to be in the stable running state are as follows:
the fluctuation value of the suction pressure of the low-pressure stage compressor and the discharge pressure of the high-pressure stage compressor is less than 50kPa/min, and the fluctuation value of the outlet water temperature of the condenser is less than 5 ℃/min;
in the step of adjusting the rotation speed of the low-pressure stage compressor and adjusting the rotation speed of the high-pressure stage compressor in equal proportion, the proportion is the rotation speed ratio of the low-pressure stage compressor and the high-pressure stage compressor before adjustment; and if the rotation speed adjustment value of the low-pressure stage compressor is greater than the set threshold value, limiting the rotation speed adjustment value of the low-pressure stage compressor to the set threshold value.
An add-drop control system for the dual stage compression heat pump system, comprising:
the monitoring module is used for acquiring the suction and exhaust pressure of the compressor in the heat pump system and judging whether the system is stable or not;
the control module is used for setting the target outlet water temperature of the condenser; collecting the actual outlet water temperature of a condenser, the rotating speed of a low-pressure stage compressor and the rotating speed of a high-pressure stage compressor; based on the difference value between the target water outlet temperature of the condenser and the actual water outlet temperature of the condenser, the rotating speed of the low-pressure stage compressor is regulated, and the rotating speed of the high-pressure stage compressor is regulated in equal proportion; and collecting the suction pressure of the low-pressure stage compressor, the discharge pressure of the high-pressure stage compressor and the interstage pressure, and adjusting the rotating speed of the high-pressure stage compressor based on the difference value between the optimal interstage pressure and the actual interstage pressure calculated by the suction pressure and the discharge pressure.
Compared with the prior art, the application has at least the following beneficial effects:
the water outlet temperature of the condenser of the heat pump system is regulated through the rotation speed of the low-pressure stage compressor and the rotation speed of the high-pressure stage compressor, so that the control precision is high, the energy loss caused by frequent start-up and stop of start-up and stop control is avoided, and the need of additional mechanical parts for slide valve control is also avoided. According to the application, the rotation speeds of the high-pressure compressor and the low-pressure compressor are simultaneously regulated by the controller, the same mass flow change of the refrigerant can be realized under the condition of smaller regulation quantity of the rotation speed of the compressor, and the motor runs closer to a design working condition point, so that the efficiency is higher; the two-stage compression heat pump system has small inter-stage pressure change, can avoid too high inter-stage pressure lifting during adjustment, causes small oil supply quantity, and improves the operation safety of the heat pump system. The application adjusts the interstage pressure of the heat pump system through the rotating speed of the high-pressure stage compressor, so that the interstage pressure is at the optimal interstage pressure, thereby improving the energy efficiency level of the heat pump system.
Furthermore, the load and unload control method of the two-stage compression heat pump system judges whether the system is in a stable running state, and avoids control imbalance caused by control under the condition that the parameters of the heat pump system are not stable in the starting process.
Furthermore, the load and unload control method of the two-stage compression heat pump system limits the rotation speed regulating value of the low-pressure stage compressor in the regulating process, and avoids insufficient oil supply caused by overhigh pressure between stages.
Drawings
FIG. 1 is a schematic diagram of a dual stage compression heat pump system according to an embodiment of the present application;
FIG. 2 is a flow chart of an load and unload control method of a dual stage compression heat pump system according to an embodiment of the present application;
FIG. 3 is a block diagram of an overload and overload control system of the dual-stage compression heat pump system according to an embodiment of the present application;
in the accompanying drawings: 1-a low pressure stage compressor; 2-high pressure stage compressor; 3-an oil-gas separator; 4-a pressure maintenance valve; a 5-condenser; 6-an intercooler; 7-an evaporator; 8-a one-way valve; 9-an oil quantity control valve; 10-an air supplementing branch expansion valve; 11-a main expansion valve; 12-an oil cooler; 13-a first PID controller; 14-a second PID controller.
Detailed Description
In order that those skilled in the art will better understand the present application, a technical solution in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present application without making any inventive effort, shall fall within the scope of the present application.
It should be noted that the terms "first," "second," and the like are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the application described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
Referring to fig. 1, the two-stage compression heat pump system of the embodiment of the application includes a low-pressure stage compressor 1 and a high-pressure stage compressor 2, wherein an outlet of the low-pressure stage compressor 1 is connected with an inlet of the high-pressure stage compressor 2, an outlet of the high-pressure stage compressor 2 is connected with an inlet of an oil-gas separator 3, an outlet of a gas path of the oil-gas separator 3 is connected with an inlet of a pressure maintaining valve 4, an outlet of the pressure maintaining valve 4 is connected with an inlet of a condenser 5, an outlet of the condenser 5 is connected with a first passage inlet of an intercooler 6 by a main passage, a first passage outlet of the intercooler 6 is connected with an inlet of a main passage expansion valve 11, an outlet of the main passage expansion valve 11 is connected with an inlet of an evaporator 7, and an outlet of the evaporator 7 is connected with an inlet of the low-pressure stage compressor 1; the outlet of the condenser 5 is connected with the inlet of the air supplementing branch expansion valve 10 by the air supplementing branch, the outlet of the air supplementing branch expansion valve 10 is connected with the inlet of the second passage of the intercooler 6, the outlet of the second passage of the intercooler 6 is connected with the inlet of the one-way valve 8, and the outlet of the one-way valve 8 is connected with the outlet of the low-pressure stage compressor 1; the oil outlet of the oil-gas separator 3 is connected with the inlet of the oil cooler 12, the outlet of the oil cooler 12 is connected with the inlet of the oil quantity control valve 9, and the outlet of the oil quantity control valve 9 is connected with the oil injection port of the high-pressure stage compressor 2; the first PID controller 13 controls the rotation speed of the high-pressure stage compressor and the low-pressure stage compressor by collecting the water temperature at the outlet of the condenser in real time; the second PID controller 14 controls the rotational speed of the high-pressure stage compressor 2 by capturing the inter-stage pressure in real time.
In the embodiment of the application, when the two-stage compression heat pump system is operated, after the medium-pressure gas-phase refrigerant output by the outlet of the low-pressure stage compressor 1 is in air supplementing mixing with the one-way valve 8, the medium-pressure gas-phase refrigerant is output by the high-pressure stage compressor 2, after oil-gas separation in the oil-gas separator 3, heat is released in the condenser 5 to be condensed into high-pressure liquid-phase refrigerant, after the main path of the refrigerant is supercooled by the medium-temperature medium-pressure two-phase refrigerant in the air supplementing branch, the main path of the refrigerant passes through the main path expansion valve 11 to be throttled to the low-pressure two-phase refrigerant, and then the low-pressure two-phase refrigerant enters the evaporator 7 to absorb heat of a heat source and returns to the low-pressure stage compressor 1; the heat released by the condenser 5 is condensed into high-pressure liquid-phase refrigerant, the air supplementing branch is throttled into medium-pressure two-phase refrigerant by the air supplementing branch expansion valve 10, and the medium-pressure two-phase refrigerant is mixed with the gas-phase refrigerant at the outlet of the low-pressure stage compressor 1 by the one-way valve 8 after heat exchange with the main high-pressure liquid-phase refrigerant by the intercooler 6 and enters the high-pressure stage compressor 2.
Based on the two-stage compression heat pump system, the embodiment of the application discloses a load-shedding control method of the two-stage compression heat pump system, which adjusts the rotating speeds of high-pressure and low-pressure stage compressors according to parameters acquired in real time so as to change the outlet temperature and the interstage pressure of a condenser of the heat pump system.
Referring to fig. 2, the load shedding control method for a two-stage compression heat pump system according to an embodiment of the application includes the following steps:
setting a target outlet water temperature of the condenser 5;
collecting the actual outlet water temperature of the condenser 5, the rotating speed of the low-pressure stage compressor 1 and the rotating speed of the high-pressure stage compressor 2;
based on the difference value between the target water outlet temperature of the condenser 5 and the actual water outlet temperature of the condenser 5, the rotating speed of the low-pressure stage compressor 1 is regulated, and the rotating speed of the high-pressure stage compressor 2 is regulated in equal proportion;
collecting the suction pressure of the low-pressure stage compressor 1, the discharge pressure of the high-pressure stage compressor 2 and the interstage pressure, and adjusting the rotating speed of the high-pressure stage compressor 2 based on the difference value between the optimal interstage pressure and the actual interstage pressure calculated by the suction pressure and the discharge pressure.
The calculation expression of the optimal interstage pressure is as follows:
wherein C is a correction coefficient; p (P) in Suction pressure for the low pressure stage compressor 1; p (P) out The discharge pressure of the high-pressure stage compressor 2.
Before the actual outlet water temperature of the condenser 5, the rotating speed of the low-pressure stage compressor 1 and the rotating speed of the high-pressure stage compressor 2 are collected, whether the system is in a stable running state or not is judged, and when the system is started, all parameters in the system are not stable, and the load and unload requirements can be wrongly judged, so that the load and unload control is needed to be performed after a period of running. In the embodiment, whether the system stably operates or not is judged by acquiring the suction and exhaust pressure of the compressor and the outlet water temperature of the condenser in the heat pump system: the fluctuation value of the suction pressure of the low-pressure stage compressor 1 and the discharge pressure of the high-pressure stage compressor 2 is less than 50kPa/min, and the fluctuation value of the outlet water temperature of the condenser 5 is less than 5 ℃/min.
The step of collecting the actual outlet water temperature of the condenser 5, the rotating speed of the low-pressure stage compressor 1 and the rotating speed of the high-pressure stage compressor 2 is implemented after the fluctuation of the suction and exhaust pressure of the compressor and the fluctuation of the water temperature at the outlet of the condenser in the heat pump system are smaller than the set values.
In the step of adjusting the rotation speed of the low-pressure stage compressor 1 and adjusting the rotation speed of the high-pressure stage compressor 2 in equal proportion, the proportion is the rotation speed ratio of the high-pressure stage compressor and the low-pressure stage compressor before adjustment; if the rotation speed adjustment value of the low-pressure stage compressor 1 is greater than the set threshold value, the rotation speed adjustment value of the low-pressure stage compressor 1 is limited to the set threshold value.
The rotating speed of the low-pressure stage compressor 1 is adjusted based on the difference value between the target water outlet temperature of the condenser 5 and the actual water outlet temperature of the condenser 5, and the rotating speed of the high-pressure stage compressor 2 is adjusted after the rotating speed of the high-pressure stage compressor 2 is adjusted in equal proportion, and the rotating speed of the high-pressure stage compressor 2 is adjusted after a first preset time length based on the difference value between the optimal inter-stage pressure and the actual inter-stage pressure calculated based on the suction and exhaust pressure. The first preset time period may be a time delay of 10 seconds of operation (the values are only exemplary values here) until the pressures are relatively stable throughout.
The first PID controller is used for controlling the outlet temperature of the condenser of the heat pump system through the rotating speed of the low-pressure stage compressor and the rotating speed of the high-pressure stage compressor, and the second PID controller is used for controlling the inter-stage pressure through the rotating speed of the high-pressure stage compressor. When the outlet water temperature of the condenser is set to be higher than the outlet water temperature of the actual condenser, the first PID controller acts to increase the rotation speed of the low-pressure stage compressor according to the PID regulation characteristic and increases the rotation speed of the high-pressure stage compressor according to the rotation speed ratio of the high-pressure stage compressor before regulation, so that the mass flow of the refrigerant in the heat pump system is increased, and the heating capacity of the heat pump system is increased to improve the outlet temperature of the actual condensed water. When the outlet water temperature of the condenser is set to be smaller than the outlet water temperature of the actual condenser, the first PID controller acts to reduce the rotation speed of the low-pressure stage compressor according to the PID regulation characteristic and reduces the rotation speed of the high-pressure stage compressor according to the rotation speed ratio of the high-pressure stage compressor before regulation, so that the mass flow of the refrigerant in the heat pump system is reduced, and the heating capacity of the heat pump system is reduced to reduce the outlet temperature of the actual condensed water. In addition, when the compressor speed is actually adjusted, it is determined whether the low pressure stage compressor speed adjustment value is greater than a set threshold value of 250rpm (the values are only exemplary values herein). And limiting the compressor speed regulating value to a set threshold value if the low-pressure stage compressor speed regulating amount is greater than the set threshold value. And if the low-pressure stage compressor rotating speed regulating quantity is smaller than the set threshold value, maintaining the compressor rotating speed regulating value unchanged.
And (3) based on the difference value between the optimal interstage pressure and the actual interstage pressure calculated by the suction and exhaust pressure, regulating the rotating speed of the high-pressure stage compressor 2, and repeating the control steps after a second preset time length. When the actual interstage pressure is greater than the optimal interstage pressure, the second PID controller acts to increase the high pressure stage compressor speed according to the PID tuning characteristics. When the actual inter-stage pressure is less than the optimal inter-stage pressure, the second PID controller acts to reduce the high pressure stage compressor speed in accordance with the PID tuning characteristics.
The load and unload control method of the heat pump system adopting the variable frequency motor generally adopts variable frequency adjustment, so that some defects of the traditional adjustment method can be avoided. However, in a dual stage compression heat pump system, changes in the speed of the high and low pressure stage compressors can result in changes in the inter-stage pressure that affect the energy efficiency and oil delivery of the heat pump system. Therefore, the advantages of variable frequency regulation can be further exerted and the energy efficiency and the safety of the heat pump system can be improved by regulating the inter-stage pressure while the heat pump system is on load reduction.
The control method provided by the application divides the control steps into two parts:
the first part is to adjust the outlet water temperature of the condenser 5 of the heat pump system, namely the heating quantity, through the rotation speed of the high-low pressure stage compressor. Adjusting the speed of the low pressure stage compressor 1 and the speed of the high pressure stage compressor 2 according to the original speed ratio of the high pressure stage compressor and the low pressure stage compressor can maintain the pressure between stages unchanged while increasing the mass flow rate of the refrigerant of the heat pump system. The high-low pressure level rotating speed is adjusted simultaneously, and the same mass flow change can be realized under the condition of smaller compressor rotating speed adjusting quantity, so that the motor operates closer to a design working condition point, and the efficiency is higher. The small change of the inter-stage pressure can also avoid the small oil supply caused by the too high lifting of the inter-stage pressure during adjustment;
the second part is to regulate the inter-stage pressure by the speed of the high-pressure stage compressor 2. The first section simultaneously adjusts the high and low pressure stage compressor speeds, but the leakage of the compressor differs at different compressor speeds, and thus the inter-stage pressure varies somewhat. In addition, the optimal inter-stage pressure may also vary due to compressor suction and discharge pressure variations. In conclusion, the rotating speed of the high-pressure stage compressor 2 is regulated by distinguishing the actual interstage pressure from the optimal interstage pressure, so that the power consumption of the compressor can be further reduced, and the energy efficiency of the heat pump system can be improved.
Referring to fig. 3, the embodiment of the application further provides an load and unload control system of a two-stage compression heat pump system, which includes:
the monitoring module is used for acquiring the suction and exhaust pressure of the compressor in the heat pump system and judging whether the system is stable or not;
the control module is used for setting the target outlet water temperature of the condenser 5; collecting the actual outlet water temperature of the condenser 5, the rotating speed of the low-pressure stage compressor 1 and the rotating speed of the high-pressure stage compressor 2; based on the difference value between the target water outlet temperature of the condenser 5 and the actual water outlet temperature of the condenser 5, the rotating speed of the low-pressure stage compressor 1 is regulated, and the rotating speed of the high-pressure stage compressor 2 is regulated in equal proportion; collecting the suction pressure of the low-pressure stage compressor 1, the discharge pressure of the high-pressure stage compressor 2 and the interstage pressure, and adjusting the rotating speed of the high-pressure stage compressor 2 based on the difference value between the optimal interstage pressure and the actual interstage pressure calculated by the suction pressure and the discharge pressure.
The calculation expression of the optimal interstage pressure is as follows:
wherein C is a correction coefficient; p (P) in Suction pressure for the low pressure stage compressor 1; p (P) out The discharge pressure of the high-pressure stage compressor 2.
Further, the step of setting the target outlet water temperature of the condenser 5 by the control module is implemented after the compressor suction and discharge pressure fluctuation and the condenser outlet water temperature fluctuation in the heat pump system in the monitoring module are smaller than the set values.
Further, in the step of adjusting the rotation speed of the low-pressure stage compressor 1 and adjusting the rotation speed of the high-pressure stage compressor 2 in equal proportion, the control module adjusts the rotation speed ratio of the low-pressure stage compressor 1 to the high-pressure stage compressor 2 before adjusting.
Further, in the step of adjusting the rotation speed of the low-pressure stage compressor 1 and adjusting the rotation speed of the high-pressure stage compressor 2 in equal proportion, if the rotation speed adjustment value of the low-pressure stage compressor 1 is greater than the set threshold, the control module limits the rotation speed adjustment value of the low-pressure stage compressor 1 to the set threshold.
Further, the control module adjusts the rotation speed of the low-pressure stage compressor 1 based on the difference between the target water outlet temperature of the condenser 5 and the actual water outlet temperature of the condenser 5, adjusts the rotation speed of the high-pressure stage compressor 2 in equal proportion, and then acquires the suction pressure of the low-pressure stage compressor 1, the exhaust pressure of the high-pressure stage compressor 2 and the inter-stage pressure after a first preset period of time, and adjusts the rotation speed of the high-pressure stage compressor 2 based on the difference between the optimal inter-stage pressure and the actual inter-stage pressure calculated by the suction and exhaust pressure.
Further, the control module adjusts the rotation speed of the low-pressure stage compressor 1 and the rotation speed of the high-pressure stage compressor 2 through the first PID controller 13 to control the outlet temperature of the heat pump system condenser 5, and adjusts the rotation speed of the high-pressure stage compressor 2 through the second PID controller 14 to control the inter-stage pressure between the low-pressure stage compressor 1 and the high-pressure stage compressor 2.
Further, the control module calculates the difference between the optimal interstage pressure and the actual interstage pressure based on the suction and exhaust pressure, adjusts the rotation speed of the high-pressure stage compressor 2, and then repeats the steps in the control module after a second preset time period.
The embodiment of the application also provides a storage medium, in particular a computer readable storage medium (Memory), which is a Memory device in a computer device and is used for storing programs and data. It is understood that the computer readable storage medium herein may include both built-in storage media in a computer device and extended storage media supported by the computer device. The computer-readable storage medium provides a storage space storing an operating system of the terminal. Also stored in the memory space are one or more instructions, which may be one or more computer programs (including program code), adapted to be loaded and executed by the processor. The computer readable storage medium herein may be a high-speed RAM memory or a non-volatile memory (non volatile memory), such as at least one magnetic disk memory. One or more instructions stored in a computer-readable storage medium may be loaded and executed by a processor to implement the corresponding steps of the load and unload control method for a dual stage compression heat pump system in the above embodiments.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical aspects of the present application and not for limiting the same, and although the present application has been described in detail with reference to the above embodiments, it should be understood by those of ordinary skill in the art that: modifications and equivalents may be made to the specific embodiments of the application without departing from the spirit and scope of the application, which is intended to be covered by the claims.
Claims (10)
1. A two-stage compression heat pump system characterized by: the device comprises a low-pressure stage compressor (1) and a high-pressure stage compressor (2), wherein the rotation speeds of the low-pressure stage compressor (1) and the high-pressure stage compressor (2) are simultaneously regulated by a controller, so that the regulation of the outlet water temperature of a condenser (5) is realized; the rotating speed of the high-pressure stage compressor (2) is independently adjusted through the controller, so that the inter-stage pressure between the low-pressure stage compressor (1) and the high-pressure stage compressor (2) is adjusted.
2. The dual stage compression heat pump system of claim 1 wherein: the low-pressure-level compressor (1) and the high-pressure-level compressor (2) are respectively controlled by respective variable frequency motors to rotate, water outlet temperature data of the condenser (5) collected in real time are received through a first PID controller (13), the rotating speeds of the low-pressure-level compressor (1) and the high-pressure-level compressor (2) are regulated at the same time, inter-stage pressure data between the low-pressure-level compressor (1) and the high-pressure-level compressor (2) collected in real time are received through a second PID controller (14), and the rotating speeds of the high-pressure-level compressors (2) are regulated independently.
3. The dual stage compression heat pump system of claim 1 wherein: the outlet of the low-pressure stage compressor (1) is connected with the inlet of the high-pressure stage compressor (2), the outlet of the high-pressure stage compressor (2) is connected with the inlet of the oil-gas separator (3), the gas path outlet of the oil-gas separator (3) is connected with the inlet of the pressure maintaining valve (4), and the outlet of the pressure maintaining valve (4) is connected with the inlet of the condenser (5).
4. The dual stage compression heat pump system of claim 1 wherein: the oil way outlet of the oil-gas separator (3) is connected with the inlet of the oil cooler (12), the outlet of the oil cooler (12) is connected with the inlet of the oil quantity control valve (9), and the outlet of the oil quantity control valve (9) is connected with the oil injection port of the high-pressure stage compressor (2).
5. The dual stage compression heat pump system of claim 1 wherein: the outlet of the condenser (5) is connected with the inlet of a first passage of the intercooler (6) through a main passage, the outlet of the first passage of the intercooler (6) is connected with the inlet of the main passage expansion valve (11), the outlet of the main passage expansion valve (11) is connected with the inlet of the evaporator (7), and the outlet of the evaporator (7) is connected with the inlet of the low-pressure stage compressor (1).
6. The dual stage compression heat pump system of claim 1 wherein: the outlet of the condenser (5) is connected with the inlet of the air supplementing branch expansion valve (10) through the air supplementing branch, the outlet of the air supplementing branch expansion valve (10) is connected with the inlet of the second passage of the intercooler (6), the outlet of the second passage of the intercooler (6) is connected with the inlet of the one-way valve (8), and the outlet of the one-way valve (8) is connected with the outlet of the low-pressure stage compressor (1).
7. The method for controlling the load and unload of a two-stage compression heat pump system according to claim 1, comprising the steps of:
setting a target outlet water temperature of the condenser (5);
collecting the actual outlet water temperature of the condenser (5), the rotating speed of the low-pressure stage compressor (1) and the rotating speed of the high-pressure stage compressor (2);
based on the difference value between the target water outlet temperature of the condenser (5) and the actual water outlet temperature of the condenser (5), the rotating speed of the low-pressure-stage compressor (1) is regulated, and the rotating speed of the high-pressure-stage compressor (2) is regulated in equal proportion;
collecting suction pressure of the low-pressure stage compressor (1), discharge pressure of the high-pressure stage compressor (2) and interstage pressure, and adjusting the rotating speed of the high-pressure stage compressor (2) based on the difference value between the optimal interstage pressure and the actual interstage pressure calculated by the suction pressure and the discharge pressure.
8. The load and unload control method of claim 7, wherein said optimal inter-stage pressure is calculated as follows:
wherein C is a correction coefficient; p (P) in Suction pressure for the low pressure stage compressor (1); p (P) out Is the discharge pressure of the high-pressure stage compressor (2).
9. The load-increasing and load-decreasing control method according to claim 7, wherein the actual outlet water temperature of the condenser (5), the rotation speed of the low-pressure stage compressor (1) and the rotation speed of the high-pressure stage compressor (2) are collected when the system is judged to be in a stable operation state, and the condition that the system is judged to be in the stable operation state is satisfied: the fluctuation value of the suction pressure of the low-pressure stage compressor (1) and the fluctuation value of the discharge pressure of the high-pressure stage compressor (2) are smaller than 50kPa/min, and the fluctuation value of the outlet water temperature of the condenser (5) is smaller than 5 ℃/min;
in the step of adjusting the rotation speed of the low-pressure stage compressor (1) and adjusting the rotation speed of the high-pressure stage compressor (2) in equal proportion, the proportion is the rotation speed ratio of the low-pressure stage compressor (1) to the high-pressure stage compressor (2) before adjustment;
and, if the rotation speed adjustment value of the low-pressure stage compressor (1) is greater than the set threshold value, limiting the rotation speed adjustment value of the low-pressure stage compressor (1) to the set threshold value.
10. The load and unload control system for a two-stage compression heat pump system according to claim 1, comprising:
the monitoring module is used for acquiring the suction and exhaust pressure of the compressor in the heat pump system and judging whether the system is stable or not;
the control module is used for setting the target outlet water temperature of the condenser (5); collecting the actual outlet water temperature of the condenser (5), the rotating speed of the low-pressure stage compressor (1) and the rotating speed of the high-pressure stage compressor (2); based on the difference value between the target water outlet temperature of the condenser (5) and the actual water outlet temperature of the condenser (5), the rotating speed of the low-pressure-stage compressor (1) is regulated, and the rotating speed of the high-pressure-stage compressor (2) is regulated in equal proportion; collecting suction pressure of the low-pressure stage compressor (1), discharge pressure of the high-pressure stage compressor (2) and interstage pressure, and adjusting the rotating speed of the high-pressure stage compressor (2) based on the difference value between the optimal interstage pressure and the actual interstage pressure calculated by the suction pressure and the discharge pressure.
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