CN115923453B

CN115923453B - PID (proportion integration differentiation) regulation zone control method and system for transcritical carbon dioxide air conditioner heat pump

Info

Publication number: CN115923453B
Application number: CN202310082884.9A
Authority: CN
Inventors: 曹锋; 贾凡; 殷翔; 何凯程
Original assignee: Xian Jiaotong University
Current assignee: Xian Jiaotong University
Priority date: 2023-01-31
Filing date: 2023-01-31
Publication date: 2025-03-14
Anticipated expiration: 2043-01-31
Also published as: CN115923453A

Abstract

The invention discloses a regional control method and a regional control system for PID regulation of a transcritical carbon dioxide air conditioner heat pump, wherein the regional control method for PID regulation comprises the following steps of obtaining the liquid carrying degree of the transcritical carbon dioxide air conditioner heat pump; and if the liquid carrying degree is greater than the preset threshold value of the liquid carrying degree, acquiring the actual exhaust pressure of the compressor, the target exhaust pressure of the compressor, the actual air supply temperature of the carriage and the target air supply temperature of the carriage, and carrying out partition control based on the difference value of the actual exhaust pressure of the compressor and the target exhaust pressure of the compressor and the difference value of the actual air supply temperature of the carriage and the target air supply temperature of the carriage. The invention particularly provides a compressor of a transcritical carbon dioxide air conditioner heat pump and an electronic expansion valve control logic, which can solve the problem of system imbalance caused by PID regulation in the operation of a heat pump mode in the prior art, and can ensure the safety and simultaneously ensure that the system has higher energy efficiency ratio.

Description

PID (proportion integration differentiation) regulation zone control method and system for transcritical carbon dioxide air conditioner heat pump

Technical Field

The invention belongs to the technical field of transcritical carbon dioxide air conditioners, and particularly relates to a regional control method and a regional control system for PID (proportion integration differentiation) regulation of a transcritical carbon dioxide air conditioner heat pump.

Background

The electric automobile has no dependence on fossil fuel resources and has the characteristics of environmental protection, and has good application prospect, but the pure electric automobile has certain heating requirements in winter due to insufficient engine waste heat, and the air conditioner or other heating systems are required to provide the heat load required by the automobile, so that the transcritical carbon dioxide heat pump air conditioning system applied to the electric automobile is required to have two modes of refrigeration and heat pump at the same time.

For a transcritical carbon dioxide system, the proper filling quantity difference is larger under different working conditions, and is related to a plurality of factors such as ambient temperature, indoor and outdoor air quantity, air supply temperature and the like, and as the refrigerating and heat pump filling quantity requirements are also different to a certain extent, the research shows that the filling quantity requirement of the heat pump system running at low ambient temperature is smaller, and the filling quantity can easily reach the vicinity of the upper limit of the refrigerant requirement under the working condition at low ambient temperature.

Under the working condition of a heat pump, the fluid at two sides of the heat regenerator is at the low pressure side of the system, so that the heat exchange temperature difference hardly exists, and the refrigerant at the outlet of the evaporator is directly fed into the compressor after passing through the liquid reservoir and being unheated. When the system is in normal operation, the refrigerant at the outlet of the evaporator is in a saturated state, so that the influence is small, and once the liquid level of the liquid reservoir is higher than the liquid separation critical value, the refrigerant at the outlet of the liquid reservoir is two-phase, the flow of the system is rapidly increased when the rotating speed of the compressor is unchanged, the temperature of the exhaust is also rapidly reduced due to the liquid suction, the control characteristic of the system is changed, and the original control logic is faced with the risk of imbalance. In the system starting stage, due to the difference of initial parameters, even if the filling amount does not reach the upper limit of the working condition, the PID adjustment is likely to cause the system to enter a serious overcharge state, so that the safety of the system is seriously affected. In summary, a new method and system for controlling the PID regulation and zoning of the transcritical carbon dioxide air conditioner heat pump are needed.

Disclosure of Invention

The invention aims to provide a method and a system for controlling PID regulation and zoning of a transcritical carbon dioxide air conditioner heat pump, which are used for solving one or more technical problems. The technical scheme of the invention particularly provides a compressor of a transcritical carbon dioxide air conditioner heat pump and an electronic expansion valve control logic, which can solve the problem of system imbalance caused by PID regulation in the operation of a heat pump mode in the prior art, and can ensure the safety and make the system have higher energy efficiency ratio.

In order to achieve the above purpose, the invention adopts the following technical scheme:

the invention provides a PID regulation zone control method for a transcritical carbon dioxide air conditioner heat pump, which comprises the following steps:

acquiring the liquid carrying degree of the transcritical carbon dioxide air conditioner heat pump;

If the liquid carrying degree is larger than the preset threshold value of the liquid carrying degree, the actual exhaust pressure of the compressor, the target exhaust pressure of the compressor, the actual air supply temperature of the carriage and the target air supply temperature of the carriage are obtained;

Wherein, the calculation expression of the degree of liquid carrying is that,

Wherein θ is the liquid carrying degree, S _suc is the suction entropy value, P _dis is the discharge pressure of the compressor, T _suc is the suction temperature of the compressor, P _suc is the suction pressure of the compressor, T _dis is the discharge temperature of the compressor, eta is the isentropic efficiency of the compressor, and T (H, P) and H (T, P) are the physical functions of the refrigerant;

The method comprises the steps of carrying out partition control on the basis of the difference value between the actual exhaust pressure of the compressor and the target exhaust pressure of the compressor and the difference value between the actual air supply temperature of the carriage and the target air supply temperature of the carriage, entering a stable control area if the actual exhaust pressure of the compressor is smaller than the target exhaust pressure of the compressor and the actual air supply temperature of the carriage is larger than the target air supply temperature of the carriage, entering a compressor rotating speed priority control area if the actual exhaust pressure of the compressor is larger than the target exhaust pressure of the compressor and the actual air supply temperature of the carriage is larger than the target air supply temperature of the carriage, entering an electronic expansion valve opening priority control area if the actual exhaust pressure of the compressor is smaller than the target exhaust pressure of the compressor and the actual air supply temperature of the carriage is smaller than the target air supply temperature of the carriage, and entering a control offset area if the actual exhaust pressure of the compressor is larger than the target exhaust pressure of the compressor and the actual air supply temperature of the carriage is smaller than the target air supply temperature of the carriage.

The invention is further improved in that the preset threshold value of the liquid carrying degree is within the range of 5-10 ℃.

The invention further improves that the step of obtaining the liquid carrying degree of the transcritical carbon dioxide air conditioner heat pump is implemented after the system is started for a first preset time period.

The invention further improves that the method further comprises the following steps after the liquid carrying degree of the transcritical carbon dioxide air conditioning heat pump is obtained:

And if the liquid carrying degree is smaller than or equal to a preset threshold value of the liquid carrying degree, the first PID controller and the second PID controller work simultaneously, wherein the first PID controller is used for controlling the air supply temperature of the carriage through the rotating speed of the compressor, and the second PID controller is used for controlling the exhaust pressure of the system through the opening degree of the electronic expansion valve.

The invention further improves that the method further comprises the following steps after the partition control is carried out based on the difference value between the actual exhaust pressure of the compressor and the target exhaust pressure of the compressor and the difference value between the actual air supply temperature of the carriage and the target air supply temperature of the carriage:

after the partition control is carried out for a second preset time period, when the fluctuation of the rotation speed of the compressor is less than or equal to 100RPM/min and the fluctuation of the opening degree of the valve is less than or equal to 5 steps/min, the system is considered to be stable;

comparing the stable liquid level theta of the suction belt of the compressor of the system, judging whether the system is in the adjustable range of the PID controller, and if so, outputting abnormal state.

The invention provides a PID regulation zone control system of a transcritical carbon dioxide air conditioner heat pump, which comprises the following components:

the acquisition module is used for acquiring the liquid carrying degree of the transcritical carbon dioxide air conditioner heat pump;

The control module is used for acquiring the actual exhaust pressure of the compressor, the target exhaust pressure of the compressor, the actual air supply temperature of the carriage and the target air supply temperature of the carriage when the liquid carrying degree is larger than a preset threshold value of the liquid carrying degree;

Wherein, the calculation expression of the degree of liquid carrying is that,

The invention further improves that in the acquisition module, the step of acquiring the liquid carrying degree of the transcritical carbon dioxide air conditioner heat pump is implemented after the system is started for a first preset time period.

The invention further improves that the control module further comprises the following steps after the liquid carrying degree of the transcritical carbon dioxide air conditioner heat pump is obtained:

The invention further improves that the control module further comprises the following steps after the partition control is carried out based on the difference value between the actual exhaust pressure of the compressor and the target exhaust pressure of the compressor and the difference value between the actual air supply temperature of the carriage and the target air supply temperature of the carriage:

Compared with the prior art, the invention has the following beneficial effects:

In the method provided by the invention, the research on the filling amount of the transcritical carbon dioxide heat pump air conditioning system is combined, the control adjustment and the overcharging state of the heat pump system are focused, the control of the system is adjusted by using related control logic, the problem of system imbalance caused by PID adjustment in the operation of a heat pump mode in the prior art can be solved, and the system can have higher energy efficiency ratio while ensuring the safety. Specifically, the method of the invention is based on the research on the behavior state of the system after the suction of the compressor with liquid in the heat pump mode of the transcritical carbon dioxide heat pump air conditioning system, by collecting the suction temperature, the discharge temperature, the suction pressure and the discharge pressure of the compressor, judging whether the system operates in an overcharged (suction with liquid) state of the compressor caused by an initial state and a control logic through a proposed liquid-carrying calculation formula, then collecting the actual discharge pressure and the air supply temperature of the system, comparing with a target value, judging the current system partition, and determining the adjustment sequence of the compressor and an electronic expansion valve according to the current partition.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description of the embodiments or the drawings used in the description of the prior art will be given in brief, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic flow chart of a control method for controlling PID regulation and zoning of a transcritical carbon dioxide air conditioner heat pump according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a transcritical carbon dioxide air conditioning heat pump system in accordance with an embodiment of the present invention;

FIG. 3 is a schematic block diagram of a transcritical carbon dioxide air conditioning heat pump compressor and electronic expansion valve control sequence selection logic in an embodiment of the present invention;

FIG. 4 is a schematic diagram of a transcritical carbon dioxide air conditioning heat pump system controlling zones according to real-time parameters in an embodiment of the present invention;

FIG. 5 is a schematic diagram of a PID control zone control system for a transcritical carbon dioxide air conditioner heat pump according to an embodiment of the present invention;

In the figure, 1, a compressor, 2, a four-way reversing valve, 3, a defrosting heat exchanger, 4, a main heat exchanger, 5, an electronic expansion valve, 6, a heat regenerator, 7, an outdoor heat exchanger, 8, a liquid storage device, 9, an indoor fan, 10, a first PID controller, 11 and a second PID controller.

Detailed Description

In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention 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 invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures 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 invention 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.

The invention is described in further detail below with reference to the attached drawing figures:

Referring to fig. 1, the method for controlling PID adjustment and partition of a transcritical carbon dioxide air conditioner heat pump according to the embodiment of the present invention specifically includes the following steps:

Step 1, collecting air suction and exhaust parameters of a compressor, and judging whether the system sucks air and carries liquid according to the liquid carrying degree theta, wherein the air suction and exhaust parameters of the compressor comprise air suction temperature, air suction pressure, air suction temperature and air suction pressure of the compressor;

the calculation formula of the liquid carrying degree is as follows:

Wherein θ is the liquid carrying degree, S _suc is the suction entropy value, P _dis is the discharge pressure of the compressor, T _suc is the suction temperature of the compressor, P _suc is the suction pressure of the compressor, T _dis is the discharge temperature of the compressor, eta is the isentropic efficiency of the compressor (which can be obtained by a fitting formula of the isentropic efficiency of the compressor), and T (H, P) and H (T, P) are the physical functions of the refrigerant.

And 2, dividing the real-time state of the system into four control areas for partition control according to the difference value of the actual value and the target value of the exhaust pressure of the compressor and the air supply temperature of the carriage by acquiring the real-time state parameters of the system, wherein the partitions are a compressor rotating speed priority control area, an electronic expansion valve opening priority control area, a control offset area and a stable control area.

In the technical scheme provided by the embodiment of the invention, different limits are applied to the PID controller according to different partitions so that the PID controller can normally run or keep the current value unchanged, and the PID controller can be limited in each partition so that the output value can be kept unchanged, and the limits can be released after the PID controller enters other control areas.

The embodiment of the present invention further preferably further includes, after step 2:

And 3, judging whether the system is stable or not by comparing whether the size resolution system of the suction liquid level theta value of the compressor is in the adjustable range of the PID controller after the system is stable or not, if the size resolution system is judged to be out of order, displaying that the current state of the system is abnormal and needs to be overhauled, wherein specifically, if the system is judged to be stable by controlling for a period of time, the system is considered to be stable when the rotation speed of the compressor fluctuates by less than 100RPM/min and the valve opening fluctuates by less than 5 steps/min, judging that the liquid level theta is continuously carried out after the system is judged to be stable, if the value is still larger, judging that the liquid level theta is carried out, indicating that the current PID control logic is unsuitable, displaying that the system is in an abnormal state and needs to be overhauled.

In the embodiment of the invention, preferably, before the step 2 is performed, whether the system is started up for a period of time T >200s can be determined, wherein 200s is a recommended value, and the system can be properly adjusted according to the actual operation characteristics of the system.

In the embodiment of the invention, if the suction liquid carrying degree theta of the compressor is less than or equal to 5 ℃ (the threshold value can be any value from 5 ℃ to 10 ℃), the control logic enters into the conventional control logic, the air supply temperature of the rotating speed control system of the compressor, the opening degree of the electronic expansion valve controls the exhaust pressure of the system, and the two PID controllers work simultaneously.

In step 2 of the embodiment of the invention, if the suction liquid level θ of the compressor is greater than 5 ℃ (the threshold value can be any value from 5 ℃ to 10 ℃), the partition judgment is performed according to the collected target value and the actual value of the discharge pressure of the compressor and the air supply temperature of the carriage, wherein if the actual value of the discharge pressure is smaller than the target value and the actual value of the air supply temperature is smaller than the target value, the air supply pressure enters the electronic expansion valve opening priority control area, if the actual value of the discharge pressure is smaller than the target value and the actual value of the air supply temperature is larger than the target value, the air supply pressure is larger than the target value and the actual value of the air supply temperature is smaller than the target value, the air supply temperature enters the compressor rotating speed priority control area, and the other areas are offset areas.

Referring to fig. 2, the transcritical carbon dioxide air conditioning heat pump system provided in the embodiment of the present invention includes an outlet of a compressor 1 connected to an a port of a four-way reversing valve 2, a B port of the four-way reversing valve 2 connected to an inlet of a defrosting heat exchanger 3, an outlet of the defrosting heat exchanger 3 connected to a main heat exchanger 4, an outlet of the main heat exchanger 4 connected to an inlet of an electronic expansion valve 5, an outlet of the electronic expansion valve 5 connected to a first passage of a regenerator 6, an outlet of the first passage of the regenerator 6 connected to an inlet of an outdoor heat exchanger 7, an outlet of the outdoor heat exchanger 7 connected to a C port of the four-way reversing valve 2, a D port of the four-way reversing valve 2 connected to a reservoir 8, a second passage of the reservoir 8 connected to a second passage of the regenerator 6, and a second passage outlet of the regenerator 6 connected to an inlet of the compressor 1. The indoor air is blown in through an indoor fan 9, a first PID controller 10 controls the rotating speed of the compressor through collecting the air supply temperature in real time, and a second PID controller 11 controls the opening of the electronic expansion valve 5 through collecting the exhaust pressure value in real time.

In the system provided by the embodiment of the invention, the trans-critical carbon dioxide reverse defrosting system can be controlled to work in a heating mode or a refrigerating mode through the four-way reversing valve.

In the embodiment of the invention, when the transcritical carbon dioxide air conditioning heat pump system is in a heating mode, high-temperature and high-pressure steam output by an outlet of the compressor 1 flows through an A-B channel of the four-way reversing valve 2 and then flows into the defrosting heat exchanger 3, then enters the main heat exchanger 4, releases heat in the two heat exchangers, then flows into a low-temperature and low-pressure state through the electronic expansion valve 5, enters the outdoor heat exchanger 7 to absorb environmental heat, and then the refrigerant flows through a C-D channel of the four-way reversing valve 2 and then flows back to the compressor 1 through the liquid reservoir 8.

In the embodiment of the invention, when the transcritical carbon dioxide air conditioning heat pump system is in a refrigeration mode, high-temperature and high-pressure steam output by an outlet of the compressor 1 flows through an A-C channel of the four-way reversing valve 2, then enters the outdoor heat exchanger 7 to release heat, then flows through a second channel of the heat regenerator 6 to exchange heat with low-pressure side refrigerant, flows into the electronic expansion valve 5 to throttle to low pressure after being further cooled, enters the main heat exchanger 4 and the defrosting heat exchanger 3 to absorb heat, and then sequentially flows through a B-D channel of the four-way reversing valve 2 and the liquid accumulator 8 to return to the compressor 1.

Based on the above-mentioned transcritical carbon dioxide air-conditioning heat pump system, the embodiment of the invention discloses a control partition judging mode of a control component of the transcritical carbon dioxide air-conditioning heat pump system of an electric automobile, which judges whether the current system is in an air-suction liquid-carrying state according to the state parameters of a real-time acquisition system, and improves the running performance and the safety of the system by intervening the start and stop of a compressor and an electronic expansion valve PID controller, and as shown in an exemplary figure 3, the partition design is required according to the dynamic characteristics of the system in the air-suction liquid-carrying state before using the method.

Referring to fig. 3, the control section judgment method of the control component of the transcritical carbon dioxide air conditioning heat pump system of the electric automobile provided by the embodiment of the invention specifically includes the following steps:

in the method, four parameters of the suction pressure, the suction temperature, the exhaust pressure and the exhaust temperature of a compressor are collected to judge the suction and liquid carrying condition of the system, wherein the judgment of the current state is started after the system is not in an initial starting state is determined, and the specific process is that the liquid carrying degree theta is calculated according to the collected suction pressure, suction temperature, exhaust pressure and exhaust temperature of the compressor:

Wherein θ is the liquid carrying degree, S _suc is the air suction entropy value, P _dis is the air discharge pressure of the compressor, T _suc is the air suction temperature of the compressor, P _suc is the air suction pressure of the compressor, T _dis is the air discharge temperature of the compressor, eta is the isentropic efficiency of the compressor and is calculated by a fitting formula;

When the liquid carrying degree theta is calculated to be less than 5 ℃, the system is considered to carry liquid slightly or not, and a PID controller controlling the opening of the compressor and the electronic expansion valve works simultaneously to adjust the state of the system;

Step 2, determining a control partition according to the current state of the system and controlling the control partition, namely determining the action sequence of two components after determining that the compressor is in a suction liquid carrying state, acquiring the actual value and the target value of the exhaust pressure of the compressor and the actual value and the target value of the air supply temperature of a carriage in order to ensure that the air supply temperature and the like of the system still meet the requirements and ensure the safety of the system;

if the exhaust pressure of the compressor is smaller than the target value, the air supply temperature of the carriage is larger than the target value, the opening of the electronic expansion valve is gradually reduced according to PID (proportion integration differentiation) regulation characteristics, the rotating speed of the compressor is gradually reduced, the mass flow of the refrigerant of the system is reduced, the suction liquid is helped to be lightened, and the two PID controllers of the rotating speed of the compressor and the opening of the valve enter into a simultaneous working state;

When the exhaust pressure of the compressor is smaller than a target value and the air supply temperature of a carriage is smaller than the target value, the PID controller can increase the rotating speed of the compressor, the opening degree of the electronic expansion valve is reduced, the increasing of the rotating speed of the compressor is unfavorable for the system to be separated from the liquid suction state, the PID controller (the second PID controller which controls the opening degree of the electronic expansion valve is firstly operated, the rotating speed of the compressor is temporarily unchanged (the first PID controller stops operating), the normal control state is started after the calculated liquid carrying degree theta is reduced below 5 ℃, and the first PID controller and the second PID controller work simultaneously to start to regulate the rotating speed of the compressor;

when the exhaust pressure of the compressor is larger than a target value, the air supply temperature of a carriage is larger than the target value, the rotating speed of the compressor is reduced by the PID controller, the opening of the electronic expansion valve is increased, the rotating speed of the compressor is reduced to be beneficial to the system to be separated from the state of the suction liquid, the opening of the electronic expansion valve is increased to increase the flow of the system, and the suction liquid is more serious, so that the first PID controller for controlling the compressor is firstly operated, the second PID controller for controlling the electronic expansion valve is firstly not operated, and then when the liquid carrying degree theta is reduced to be below 5 ℃, the first PID controller and the second PID controller are operated simultaneously, and the opening of the electronic expansion valve is started to be regulated;

when the exhaust pressure of the compressor is larger than a target value, the air supply temperature of a carriage is smaller than the target value, the PID controller can increase the rotating speed of the compressor, the opening of the electronic expansion valve is increased, the system is in a liquid suction and carrying state, the rotating speed of the compressor and the opening action of the valve can make the liquid suction and carrying of the system more serious, the system is in a control imbalance zone, the original PID control is difficult to break away from the current state, and new control logic needs to be considered for control;

And 3, judging whether overcharge/imbalance inhibition control is required to be introduced according to a system control result, wherein after judging that the compressor is in an air suction liquid state and performs certain adjustment, the system can finally run to two states, one of the states is ideal, the air suction liquid state disappears, the system runs normally, the other is still in the air suction liquid state, at the moment, the energy efficiency ratio of the system is reduced due to the air suction liquid state, if the system runs continuously in the imbalance region mentioned in the step 2, the imbalance region is possibly continuously adjusted to be in the imbalance state, after adjustment, the air suction liquid state system is generally arranged in an electronic expansion valve priority region and a compressor rotating speed priority region, the imbalance region is embodied as that the system is kept stable, and the two PID controllers are not operated, but the defined liquid degree theta is still larger than 5 ℃, so that the reason that the adjustment is difficult is more, the current system filling amount exceeds the upper limit of the working condition, and the initial state is unreasonable, so that partition control is adopted but the dynamic performance is changed too much, so that the PID control logic is not suitable. It has been difficult to make optimal adjustments by changing the PID controller, requiring downtime or forced intervention.

According to the embodiment of the invention, four signal values of two points of the air suction temperature, the air suction pressure, the air discharge temperature and the air discharge pressure of the compressor are acquired through a PT sensor of the system during control, the theoretical air discharge temperature is calculated through an isentropic efficiency fitting formula of the compressor, and the theoretical air discharge temperature and the actual air discharge temperature are subjected to difference judgment to judge the system liquid carrying condition, and because the system possibly does not reach a steady state during starting, the current system filling state is erroneously judged, the operation of the system is ensured to be started for 200s (the numerical value is only an exemplary numerical value) during the judgment of entering the air suction liquid carrying of the compressor.

Further explanation of the embodiment of the invention is that the suction liquid is generally considered to be caused by the over-charging of the system, but in practice, besides the excessive refrigerant charging quantity, the improper initial state and PID parameters can possibly lead the system to operate in the suction liquid state, in this state, the original dynamic characteristics of the system are changed, the original PID regulation can lead the system to fall into a control dead zone, the performance is reduced sharply, and the safety of the system is difficult to ensure. In order to avoid the phenomena of liquid suction and control imbalance caused by improper PID system parameters, the invention introduces the suction and exhaust pressure and temperature of the compressor to judge whether the compressor sucks the liquid suction and liquid discharge, wherein the judgment is mainly based on the difference value between the theoretical calculated exhaust temperature and the actual exhaust temperature, and the theoretical exhaust temperature calculation is calculated through the isentropic efficiency fitting formula of the compressor itself and the suction and exhaust pressure and temperature. When the suction temperature is collected, whether the suction temperature is in a two-phase state or a saturated gas state cannot be judged, if the actual suction state is in the two-phase state according to saturated gas calculation, the difference theta between the theoretical discharge temperature and the actual discharge temperature is judged, whether the suction belt of the compressor is carried out by the compressor can be judged more simply and definitely, and if the suction belt is in the state, the control is carried out in different control sequences according to the current discharge pressure of the system, the difference between the supply temperature and the respective target values. Further specifically, after judging that the compressor has sucked in liquid, the control partition is performed according to the current air supply temperature and the discharge pressure of the compressor, and the control partition is briefly described herein.

In a conventional transcritical CO ₂ heat pump air conditioning system, as shown in fig. 2, the compressor discharge pressure is controlled by an electronic expansion valve through a second PID, and the cabin supply air temperature is controlled by the compressor speed through a first PID. In this process, the control logic is based on the supply air temperature increasing with increasing compressor speed and the discharge air pressure increasing with decreasing valve opening. When the compressor sucks the serious liquid, the situation changes, the exhaust temperature of the compressor is rapidly reduced after the compressor sucks the liquid, the heat exchange temperature difference is reduced due to the reduction of the exhaust temperature, the air supply temperature is reduced, the rotating speed of the compressor is increased according to the original PID logic, the flow of the refrigerant is further increased, the refrigerant is migrated due to heat exchange, the liquid is further increased, the air supply temperature is difficult to reach the target value, and the system enters the control dead zone. Through related researches, the phenomenon is restrained to a certain extent by reducing the flow of the refrigerant when the compressor sucks the liquid, and accordingly the control area of the system is divided into four parts shown in fig. 4 according to the air supply temperature, the target value and the current value of the discharge pressure of the compressor so as to alleviate the phenomenon of liquid suction and liquid entrainment of the system caused by control and initial conditions when the system is not overcharged.

The method provided by the invention combines the research on the filling amount of the transcritical carbon dioxide heat pump air conditioning system, focuses on the control adjustment and the overcharging state of the heat pump system, uses the control logic to adjust the system control, can solve the problem of system imbalance caused by PID adjustment in the operation of a heat pump mode in the prior art, and can ensure the safety and simultaneously ensure the system to have higher energy efficiency ratio.

The following are device embodiments of the present invention that may be used to perform method embodiments of the present invention. For details of the device embodiment that are not careless, please refer to the method embodiment of the present invention.

Referring to fig. 5, in still another embodiment of the present invention, a PID regulated zone control system for a transcritical carbon dioxide air conditioning heat pump is provided, comprising:

Wherein, the calculation expression of the degree of liquid carrying is that,

In yet another embodiment of the present invention, a computer device is provided that includes a processor and a memory for storing a computer program including program instructions, the processor for executing the program instructions stored by the computer storage medium. The Processor may be a central processing unit (Central Processing Unit, CPU), other general purpose Processor, digital signal Processor (DIGITAL SIGNAL Processor, DSP), application Specific Integrated Circuit (ASIC), off-the-shelf Programmable gate array (Field-Programmable GATE ARRAY, FPGA) or other Programmable logic device, discrete gate or transistor logic device, discrete hardware components, etc., which are a computing core and a control core of the terminal adapted to implement one or more instructions, and in particular to load and execute one or more instructions in a computer storage medium to implement a corresponding method flow or a corresponding function, and the Processor according to embodiments of the present invention may be used to implement operations of a transcritical carbon dioxide air conditioner heat pump PID regulating partition control method.

In yet another embodiment of the present invention, a storage medium, specifically a computer readable storage medium (Memory), is a Memory device in a computer device, for storing a program 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 above-described embodiments with respect to a method for controlling a PID regulation partition of a transcritical carbon dioxide air conditioning heat pump.

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 solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made to the specific embodiments of the present invention without departing from the spirit and scope of the present invention, and any modifications and equivalents are intended to be included in the scope of the claims of the present invention.

Claims

1. A PID regulation zoning control method for a transcritical carbon dioxide air conditioning heat pump, characterized in that it comprises the following steps:

Obtaining the liquid content of the transcritical carbon dioxide air conditioning heat pump;

If the liquid content is greater than a preset liquid content threshold, the actual exhaust pressure of the compressor, the target exhaust pressure of the compressor, the actual air supply temperature of the cabin, and the target air supply temperature of the cabin are obtained; based on the difference between the actual exhaust pressure of the compressor and the target exhaust pressure of the compressor, and the difference between the actual air supply temperature of the cabin and the target air supply temperature of the cabin, zoning control is performed;

Among them, the calculation expression of liquid density is:

Wherein, θ is the liquid content; S _suc is the suction entropy value; P _dis is the compressor exhaust pressure; T _suc is the compressor suction temperature; P _suc is the compressor suction pressure; T _dis is the compressor exhaust temperature; η is the compressor isentropic efficiency, T(H, P) and H(T, P) are refrigerant physical property functions;

Among them, in the step of performing zoning control based on the difference between the actual exhaust pressure of the compressor and the target exhaust pressure of the compressor, and the difference between the actual air supply temperature of the cabin and the target air supply temperature of the cabin, if the actual exhaust pressure of the compressor is less than the target exhaust pressure of the compressor and the actual air supply temperature of the cabin is greater than the target air supply temperature of the cabin, then the stable control zone is entered; if the actual exhaust pressure of the compressor is greater than the target exhaust pressure of the compressor and the actual air supply temperature of the cabin is greater than the target air supply temperature of the cabin, then the compressor speed priority control zone is entered; if the actual exhaust pressure of the compressor is less than the target exhaust pressure of the compressor and the actual air supply temperature of the cabin is less than the target air supply temperature of the cabin, then the electronic expansion valve opening priority control zone is entered; if the actual exhaust pressure of the compressor is greater than the target exhaust pressure of the compressor and the actual air supply temperature of the cabin is less than the target air supply temperature of the cabin, then the control disorder zone is entered.

2. A PID regulation zoning control method for a transcritical carbon dioxide air conditioning heat pump according to claim 1, characterized in that the value range of the preset threshold value of the liquid concentration is 5°C to 10°C.

3. A PID regulation zoning control method for a transcritical carbon dioxide air-conditioning heat pump according to claim 1, characterized in that the step of obtaining the liquid content of the transcritical carbon dioxide air-conditioning heat pump is implemented after the system is started for a first preset time.

4. A PID regulation zoning control method for a transcritical carbon dioxide air conditioning heat pump according to claim 1, characterized in that after obtaining the liquid content of the transcritical carbon dioxide air conditioning heat pump, the method further comprises the following steps:

If the liquid content is less than or equal to the preset liquid content threshold, the first PID controller and the second PID controller work simultaneously; wherein the first PID controller is used to control the cabin air supply temperature through the compressor speed, and the second PID controller is used to control the system exhaust pressure through the electronic expansion valve opening.

5. A transcritical carbon dioxide air conditioning heat pump PID regulation zoning control method according to claim 1, characterized in that after the zoning control is performed based on the difference between the actual exhaust pressure of the compressor and the target exhaust pressure of the compressor, and the difference between the actual air supply temperature of the cabin and the target air supply temperature of the cabin, the following steps are also included:

After the partition control is performed for a second preset time, when the compressor speed fluctuation is less than or equal to 100 RPM/min and the valve opening fluctuation is less than or equal to 5 steps/min, the system is considered stable;

Compare the values of the compressor suction liquid concentration θ after the system stabilizes to determine whether the system is within the adjustable range of the PID controller. If it is determined to be out of adjustment, the output state is abnormal.

6. A transcritical carbon dioxide air conditioning heat pump PID regulation zoning control system, characterized by comprising:

An acquisition module, used to acquire the liquid content of the transcritical carbon dioxide air conditioning heat pump;

A control module, configured to obtain, when the liquid content is greater than a preset threshold value of the liquid content, an actual exhaust pressure of the compressor, an actual air supply temperature of the cabin, and a target air supply temperature of the cabin; and perform zoning control based on a difference between the actual exhaust pressure of the compressor and the target exhaust pressure of the compressor, and a difference between the actual air supply temperature of the cabin and the target air supply temperature of the cabin;

Among them, the calculation expression of liquid density is:

Among them, in the step of performing zoning control based on the difference between the actual exhaust pressure of the compressor and the target exhaust pressure of the compressor, and the difference between the actual air supply temperature of the cabin and the target air supply temperature of the cabin, if the actual exhaust pressure of the compressor is less than the target exhaust pressure of the compressor and the actual air supply temperature of the cabin is greater than the target air supply temperature of the cabin, then the stable control zone is entered; if the actual exhaust pressure of the compressor is greater than the target exhaust pressure of the compressor and the actual air supply temperature of the cabin is greater than the target air supply temperature of the cabin, then the compressor speed priority control zone is entered; if the actual exhaust pressure of the compressor is less than the target exhaust pressure of the compressor and the actual air supply temperature of the cabin is less than the target air supply temperature of the cabin, then the electronic expansion valve opening priority control zone is entered; if the actual exhaust pressure of the compressor is greater than the target exhaust pressure of the compressor and the actual air supply temperature of the cabin is less than the target air supply temperature of the cabin, then the control imbalance zone is entered.

7. A transcritical carbon dioxide air conditioning heat pump PID regulation zoning control system according to claim 6, characterized in that the value range of the preset threshold value of the liquid concentration is 5°C to 10°C.

8. A transcritical carbon dioxide air-conditioning heat pump PID regulation zoning control system according to claim 6, characterized in that, in the acquisition module, the step of acquiring the liquid content of the transcritical carbon dioxide air-conditioning heat pump is implemented after the system is started for a first preset time.

9. A transcritical carbon dioxide air conditioning heat pump PID regulation zoning control system according to claim 6, characterized in that, in the control module, after obtaining the liquid content of the transcritical carbon dioxide air conditioning heat pump, the control module further comprises the following steps:

10. A transcritical carbon dioxide air conditioning heat pump PID regulation zoning control system according to claim 6, characterized in that, in the control module, after the zoning control is performed based on the difference between the actual exhaust pressure of the compressor and the target exhaust pressure of the compressor, and the difference between the actual air supply temperature of the cabin and the target air supply temperature of the cabin, the following steps are further included: