A PID regulation zoning control method and system for a transcritical carbon dioxide air conditioning heat pump

Abstract

The present invention discloses a transcritical carbon dioxide air conditioning heat pump PID regulation zoning control method and system, the PID regulation zoning control method comprises the following steps: obtaining the liquid content of the transcritical carbon dioxide air conditioning heat pump; if the liquid content is greater than the preset liquid content threshold, obtaining 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; 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. The present invention specifically provides a compressor and electronic expansion valve control logic for a transcritical carbon dioxide air conditioning heat pump, which can solve the system imbalance problem caused by PID regulation when operating in heat pump mode in the prior art, and can ensure safety while making the system have a higher energy efficiency ratio.

Description

Technical Field

[0001] The invention belongs to the technical field of transcritical carbon dioxide air conditioning, and in particular relates to a PID regulation zoning control method and system for a transcritical carbon dioxide air conditioning heat pump. Background Art

[0002] Electric vehicles have no dependence on fossil fuel resources and are environmentally friendly, so they have good application prospects. However, pure electric vehicles do not have enough engine waste heat, so there is a certain demand for heating in the car in winter. They need to rely on air conditioning or other heating systems to provide the required heat load for the vehicle. Therefore, the transcritical carbon dioxide heat pump air-conditioning system used in electric vehicles needs to have both cooling and heat pump modes.

[0003] For transcritical carbon dioxide systems, the appropriate filling amount under different working conditions varies greatly, which is related to many factors such as ambient temperature, indoor and outdoor air volume, and supply air temperature. Since the filling amount requirements for refrigeration and heat pumps are also different, research has found that the filling amount requirement for heat pump systems operating at low ambient temperatures is smaller, and at low ambient temperatures, the filling amount can easily reach near the upper limit of the refrigerant demand under this working condition.

[0004] In the transcritical carbon dioxide heat pump air conditioning system, under heat pump working conditions, since the fluids on both sides of the regenerator are on the low-pressure side of the system, there is almost no heat exchange temperature difference, and the refrigerant at the evaporator outlet is not heated after passing through the liquid reservoir and directly enters the compressor. When the system is operating normally, the refrigerant at the evaporator outlet is in a saturated state, which has little impact; but once the liquid level in the liquid reservoir is higher than the liquid separation critical value, the refrigerant at the liquid reservoir outlet is two-phase, and the system flow increases sharply when the compressor speed remains unchanged. The exhaust temperature also drops sharply due to the suction liquid, the system control characteristics change, and the original control logic faces the risk of maladjustment. In the system startup stage, due to the difference in 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, which seriously affects the system safety. In summary, a new PID adjustment zoning control method and system for transcritical carbon dioxide air conditioning heat pumps is urgently needed. Summary of the invention

[0005] The purpose of the present invention is to provide a transcritical carbon dioxide air conditioning heat pump PID regulation zoning control method and system to solve one or more of the above-mentioned technical problems. The technical solution of the present invention specifically provides a transcritical carbon dioxide air conditioning heat pump compressor and electronic expansion valve control logic, which can solve the system imbalance problem caused by PID regulation when operating in heat pump mode in the prior art, and can ensure safety while making the system have a higher energy efficiency ratio.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a transcritical carbon dioxide air conditioning heat pump PID regulation zoning control method, comprising the following steps:

[0008] Obtaining the liquid content of the transcritical carbon dioxide air conditioning heat pump;

[0009] 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;

[0010] Among them, the calculation expression of liquid density is:

[0011]

[0012] Where, θ is the liquid content; S suc is the inspiratory 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;

[0013] 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.

[0014] A further improvement of the present invention is that the value range of the preset threshold value of liquid content is 5°C to 10°C.

[0015] A further improvement of the present invention is 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.

[0016] A further improvement of the present invention is that after obtaining the liquid content of the transcritical carbon dioxide air conditioning heat pump, the following steps are also included:

[0017] 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.

[0018] A further improvement of the present invention is that after the partition 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:

[0019] 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;

[0020] 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.

[0021] The present invention provides a transcritical carbon dioxide air conditioning heat pump PID regulation partition control system, comprising:

[0022] An acquisition module, used to acquire the liquid content of the transcritical carbon dioxide air conditioning heat pump;

[0023] 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;

[0024] Among them, the calculation expression of liquid density is:

[0025]

[0026] Where, θ is the liquid content; S suc is the inspiratory 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;

[0027] 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.

[0028] A further improvement of the present invention is that the value range of the preset threshold value of liquid content is 5°C to 10°C.

[0029] A further improvement of the present invention is 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.

[0030] A further improvement of the present invention is that, in the control module, after obtaining the liquid content of the transcritical carbon dioxide air conditioning heat pump, the control module further includes the following steps:

[0031] 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.

[0032] A further improvement of the present invention is that, in the control module, after performing the partition 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, the following steps are further included:

[0033] 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;

[0034] 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.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] In the method provided by the present invention, combined with the research on the charging amount of the transcritical carbon dioxide heat pump air conditioning system, the focus is on the control adjustment and overcharge state of the heat pump system, and the system control is adjusted by using the relevant control logic, which can solve the system imbalance problem caused by PID adjustment when the heat pump mode is running in the prior art, and can ensure safety while making the system have a higher energy efficiency ratio. Specifically, the method of the present invention is based on the research on the system behavior state after the compressor sucks liquid in the heat pump mode of the transcritical carbon dioxide heat pump air conditioning system, by collecting the suction temperature, exhaust temperature, suction pressure, and exhaust pressure of the compressor, and judging whether the system is running in the overcharge (compressor sucks liquid) state caused by the initial state and control logic through the proposed liquid calculation formula, and then collecting the actual exhaust pressure and supply air temperature of the system and comparing them with the target value to judge the current system partition and determine the adjustment order of the compressor and the electronic expansion valve according to the current partition; it is worth further emphasizing that the method of the present invention has a certain improvement in the robustness of the system PID control after the control characteristics are changed when the system enters a quasi-overcharge state, and the system control may not enter an imbalanced state in a larger initial state space. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art; obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 It is a flow chart of a PID regulation zoning control method for a transcritical carbon dioxide air conditioning heat pump provided by an embodiment of the present invention;

[0039] Figure 2 is a schematic diagram of a transcritical carbon dioxide air conditioning heat pump system in an embodiment of the present invention;

[0040] Figure 3 It is a schematic block diagram of the logic of the control sequence selection of the transcritical carbon dioxide air conditioning heat pump compressor and the electronic expansion valve in an embodiment of the present invention;

[0041] Figure 4 1 is a schematic diagram of controlling partitions according to real-time parameters of a transcritical carbon dioxide air conditioning heat pump system in an embodiment of the present invention;

[0042] Figure 5 It is a schematic diagram of a transcritical carbon dioxide air conditioning heat pump PID regulation zoning control system provided by an embodiment of the present invention;

[0043] In the figure, 1. compressor; 2. four-way reversing valve; 3. defrost heat exchanger; 4. main heat exchanger; 5. electronic expansion valve; 6. regenerator; 7. outdoor heat exchanger; 8. liquid storage tank; 9. indoor fan; 10. first PID controller; 11. second PID controller. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0045] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0046] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0047] See also Figure 1 The embodiment of the present invention provides a transcritical carbon dioxide air conditioning heat pump PID regulation partition control method, which may specifically include the following steps:

[0048] Step 1, collecting compressor suction and exhaust parameters, and judging whether the system is inhaling liquid by the liquid carrying degree θ; wherein the compressor suction and exhaust parameters include compressor exhaust temperature, exhaust pressure, suction temperature and suction pressure;

[0049] The above calculation formula for liquid content is:

[0050]

[0051] Where: θ is the liquid content; S suc is the inspiratory entropy value; P dis is the compressor exhaust pressure; T suc is the compressor suction temperature; P suc is the compressor suction pressure; Tdis is the compressor exhaust temperature; η is the compressor isentropic efficiency (which can be obtained by the compressor isentropic efficiency fitting formula), T(H, P) and H(T, P) are refrigerant physical property functions.

[0052] Step 2, by collecting the real-time status parameters of the system, according to the difference between the actual value and the target value of the compressor exhaust pressure and the cabin air supply temperature, the real-time status of the system is divided into four control areas for zone control; among which, the zones are the compressor speed priority control area, the electronic expansion valve opening priority control area, the control imbalance area and the stable control area.

[0053] In the technical solution provided by the embodiment of the present invention, different restrictions are imposed on the PID controller according to different partitions, so that it can operate normally or keep the current value unchanged; in each partition, the PID controller may be restricted to keep its output value unchanged, and the restriction will be lifted when it enters other control areas.

[0054] The embodiment of the present invention is further preferred, and further includes after step 2:

[0055] Step 3, after the system is considered stable, by comparing the size of the compressor suction liquid content θ after the system is stable, it is determined whether the system is in the adjustable range of the PID controller. If it is determined to be out of adjustment, it is displayed that the current state of the system is abnormal and needs to be repaired. Specifically, if the system is controlled for a period of time to determine whether it is stable, when the compressor speed fluctuation is <100RPM / min and the valve opening fluctuation is <5 steps / min, the system is considered stable; after determining that the system control is stable, the liquid content θ is continued to be judged. If its value is still large, it is judged to be liquid, indicating that the current PID control logic is not suitable, and the display system has entered an abnormal state and needs to be repaired.

[0056] Preferably, in the embodiment of the present invention, before judging in step 2, it can be judged whether the system startup time T>200s, where 200s is a recommended value and can be appropriately adjusted according to the actual operating characteristics of the system.

[0057] In the embodiment of the present invention, if the compressor suction liquid degree θ≤5°C (the threshold value here can be any value between 5°C and 10°C), the conventional control logic is entered, the compressor speed controls the system supply air temperature, the electronic expansion valve opening controls the system exhaust pressure, and the two PID controllers work simultaneously.

[0058] In step 2 of the embodiment of the present invention, if the compressor suction liquid degree θ>5°C (the threshold value here can be any value between 5°C and 10°C), the zoning judgment is performed according to the collected compressor exhaust pressure, cabin air supply temperature target value and actual value; wherein, if the actual value of the exhaust pressure is less than its target value and the actual value of the supply air temperature is less than the target value, it enters the electronic expansion valve opening priority control area; if the actual value of the exhaust pressure is less than the target value and the actual value of the supply air temperature is greater than the target value, it enters the normal control area; if the actual value of the exhaust pressure is greater than the target value and the actual value of the supply air temperature is less than the target value, it enters the compressor speed priority control area, and other areas are imbalance areas.

[0059] See also Figure 2 A transcritical carbon dioxide air conditioning heat pump system provided in an embodiment of the present invention comprises: the outlet of the compressor 1 is connected to the A port of the four-way reversing valve 2, the B port of the four-way reversing valve 2 is connected to the inlet of the defrosting heat exchanger 3, the outlet of the defrosting heat exchanger 3 is connected to the main heat exchanger 4, the outlet of the main heat exchanger 4 is connected to the inlet of the electronic expansion valve 5, the outlet of the electronic expansion valve 5 is connected to the first passage of the regenerator 6, the first passage outlet of the regenerator 6 is connected to the inlet of the outdoor heat exchanger 7, the outlet of the outdoor heat exchanger 7 is connected to the C port of the four-way reversing valve 2, the D port of the four-way reversing valve 2 is connected to the liquid reservoir 8, the liquid reservoir 8 is connected to the second passage of the regenerator 6, and the second passage outlet of the regenerator 6 is connected to the inlet of the compressor 1. Indoor air is blown in through the indoor fan 9, the first PID controller 10 controls the compressor speed by real-time acquisition of the air supply temperature; the second PID controller 11 controls the opening of the electronic expansion valve 5 by real-time acquisition of the exhaust pressure value.

[0060] In the system of the embodiment of the present invention, the transcritical carbon dioxide reverse defrosting system can be controlled to operate in the heating mode or the cooling mode through the four-way reversing valve.

[0061] In an embodiment of the present invention, when the above-mentioned transcritical carbon dioxide air-conditioning heat pump system is in heating mode, the high-temperature and high-pressure steam output from the outlet of the compressor 1 flows through the AB channel of the four-way reversing valve 2 and then flows into the defrost heat exchanger 3, and then enters the main heat exchanger 4. After the high-temperature and high-pressure steam releases heat in the two heat exchangers, it is throttled to a low-temperature and low-pressure state through the electronic expansion valve 5, enters the outdoor heat exchanger 7 to absorb ambient heat, and then the refrigerant passes through the CD channel of the four-way reversing valve 2 and returns to the compressor 1 through the liquid storage tank 8.

[0062] In an embodiment of the present invention, when the above-mentioned transcritical carbon dioxide air-conditioning heat pump system is in cooling mode, the high-temperature and high-pressure steam output from the outlet of the compressor 1 flows through the AC channel of the four-way reversing valve 2, then enters the outdoor heat exchanger 7 to release heat, and then passes through the second channel of the heat regenerator 6 to exchange heat with the low-pressure side refrigerant. After further cooling, it flows into the electronic expansion valve 5 to be throttled to low pressure, enters the main heat exchanger 4 and the defrost heat exchanger 3 to absorb heat, and then returns to the compressor 1 through the BD channel of the four-way reversing valve 2 and the liquid storage tank 8 in sequence.

[0063] Based on the above-mentioned transcritical carbon dioxide air conditioning heat pump system, the embodiment of the present invention discloses a control partition judgment method for the control component of the electric vehicle transcritical carbon dioxide air conditioning heat pump system, which judges whether the current system is in the state of suction with liquid based on the state parameters of the real-time acquisition system, and improves the system operation performance and safety by intervening in the start and stop of the compressor and the electronic expansion valve PID controller; for example, Figure 3 As shown, before using this method, it is necessary to carry out zoning design based on the dynamic characteristics of the system when sucking air with liquid.

[0064] See also Figure 3 , an embodiment of the present invention provides a control partition determination method for a control component of a transcritical carbon dioxide air conditioning heat pump system for an electric vehicle, and the process may specifically include the following steps:

[0065] Step 1, determine whether the system is currently in a basically stable state and judge whether it is liquid-carrying: Since the system has different refrigerant requirements under different working conditions, the same filling amount, the same working condition control method and initial conditions also have a certain impact on the control result; in view of this, the present invention collects four parameters of compressor suction pressure, suction temperature, exhaust pressure, and exhaust temperature to judge the system suction liquid-carrying situation. Here, after determining that the system is not in the initial startup state, the current state is judged. The specific process is to calculate the liquid-carrying degree θ based on the collected compressor suction pressure, suction temperature, exhaust pressure, and exhaust temperature:

[0066]

[0067] Where: θ is the liquid content; S suc is the inspiratory 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, which is calculated by the fitting formula;

[0068] When the calculated liquid carryover θ<5℃, it is considered that the system has slight or no liquid carryover, and the PID controller that controls the compressor and the electronic expansion valve opening works simultaneously to adjust the system state; when the calculated liquid carryover θ>5℃, it is determined that the compressor is in the state of suction liquid carryover, and the system may run into the control dead zone, and enter step 2 for judgment;

[0069] Step 2, determine the control partition according to the current state of the system and control it: after determining that the compressor is in the state of suction with liquid, in order to ensure that the system air supply temperature can still meet the requirements and ensure the safety of the system, collect the actual value and target value of the compressor exhaust pressure, the actual value and target value of the cabin air supply temperature to determine the action sequence of the two components;

[0070] If the compressor exhaust pressure is less than the target value and the cabin air supply temperature is greater than the target value, according to the PID regulation characteristics, the opening of the electronic expansion valve will gradually decrease, and the compressor speed will gradually decrease. Both will lead to a decrease in the system refrigerant mass flow rate, which helps to reduce the suction liquid, and enter the state where the compressor speed and valve opening PID controllers work simultaneously;

[0071] When the exhaust pressure of the compressor is less than the target value and the cabin air supply temperature is less than the target value, the PID controller will increase the compressor speed and reduce the opening of the electronic expansion valve. The increase in the compressor speed is not conducive to the system leaving the state of suction with liquid. Here, the PID controller that controls the opening of the electronic expansion valve (the second PID controller works) is first operated, and the compressor speed remains unchanged temporarily (the first PID controller stops working). After the calculated liquid degree θ drops below 5°C, it enters the normal control state. The first PID controller and the second PID controller work simultaneously and start to adjust the compressor speed.

[0072] When the exhaust pressure of the compressor is greater than the target value, and the cabin air supply temperature is greater than the target value, the PID controller will reduce the speed of the compressor and increase the opening of the electronic expansion valve. The reduction of the compressor speed is conducive to the system getting out of the state of air intake with liquid, while the increase of the opening of the electronic expansion valve will increase the system flow and make the air intake with liquid more serious. Therefore, at this time, the first PID controller controlling the compressor is first operated, and the second PID controller controlling the electronic expansion valve does not work first. Then, when the liquid degree θ drops below 5°C, the first PID controller and the second PID controller work at the same time and start to adjust the opening of the electronic expansion valve.

[0073] When the exhaust pressure of the compressor is greater than the target value and the air supply temperature of the cabin is less than the target value, the PID controller will increase the speed of the compressor and the opening of the electronic expansion valve. At this time, the system is in the state of air suction with liquid. The compressor speed and valve opening will make the air suction with liquid more serious. It is in the control disorder area. It is difficult to get rid of the current state by using the original PID control. It is necessary to consider introducing a new control logic for control.

[0074] Step 3, judging whether it is necessary to introduce overcharge / disorder suppression control according to the system control result: after judging that the compressor is in the state of suction liquid and making certain adjustments, the system can eventually run into two states, one of which is more ideal, the suction liquid phenomenon disappears, and the system runs normally; the other is that the system is still in the state of suction liquid, at this time, the suction liquid will cause the system energy efficiency ratio to decrease; among them, if the system continues to run in the imbalance zone mentioned in step 2, it will continue to adjust to the imbalance state, and it may also be in the state of suction liquid after adjustment. The system generally appears in the electronic expansion valve priority zone and the compressor speed priority zone. The imbalance zone is specifically manifested as the system remains stable, and both PID controllers do not act, but the defined liquid degree θ is still greater than 5°C. There are many reasons for its difficulty in adjustment. It may be that the current system charge exceeds the upper limit of the working condition, or it may be that the initial state is unreasonable, resulting in the use of partition control but the dynamic performance changes too much, resulting in the PID control logic being inapplicable. At this time, it is difficult to optimize and adjust by changing the PID controller, and shutdown or forced intervention is required.

[0075] Further explanation of the embodiment of the present invention is that during control, it is necessary to collect four signal values ​​of the compressor's suction temperature, suction pressure, exhaust temperature, and exhaust pressure at two points through the system's PT sensor, calculate the theoretical exhaust temperature through the compressor isentropic efficiency fitting formula, and subtract it from the actual exhaust temperature to determine the system's liquid-carrying condition; because the system may not have reached a steady state when it is started, and the current system filling state may be incorrectly determined, it is necessary to ensure that the system has been started and running for 200 seconds when entering the compressor suction liquid-carrying judgment (the values ​​here are only exemplary values).

[0076] Further explanation of the embodiment of the present invention, the suction liquid is generally considered to be caused by system overcharging, but in fact, in addition to excessive refrigerant filling, improper initial state and PID parameters may also cause the system to operate in the suction liquid state; in this state, the original dynamic characteristics of the system change, and the original PID adjustment will cause the system to fall into the control dead zone, and the performance will drop sharply while the system safety is difficult to guarantee. In order to avoid the suction liquid and control disorder caused by improper PID system parameters, the present invention introduces the compressor suction and exhaust pressure and temperature to judge whether the compressor is suction liquid. Here, the judgment is mainly based on the difference between the theoretical calculated exhaust temperature and the actual exhaust temperature. The theoretical exhaust temperature is calculated by the isentropic efficiency fitting formula of the compressor itself and the suction and exhaust pressure and temperature. When collecting the suction temperature, it is impossible to judge whether it is a two-phase state or a saturated gas state. Here, it is calculated according to the saturated gas. If the actual suction state is two-phase, the difference θ between the theoretical exhaust temperature and the actual exhaust temperature will appear, and it can be judged more simply and clearly whether the compressor is suction liquid. If in this state, it is divided into zones according to the difference between the current exhaust pressure and the supply air temperature of the system and their respective target values ​​and controlled in different control sequences. To explain in further detail, after determining that the compressor has inhaled air with liquid, the control partition will be carried out according to the current supply air temperature and compressor exhaust pressure. The basis for this is briefly described here.

[0077] Conventional transcritical CO2 heat pump air conditioning system such as Figure 2 As shown, the compressor exhaust pressure is controlled by the electronic expansion valve through the second PID, and the cabin air supply temperature is controlled by the compressor speed through the first PID. In this process, the control logic is based on the fact that the supply air temperature increases with the increase of the compressor speed; the exhaust pressure increases with the decrease of the valve opening. When the compressor inhales liquid seriously, this situation changes. After the compressor inhales liquid, its exhaust temperature drops rapidly. The reduction in exhaust temperature will cause the heat exchange temperature difference to become smaller and the supply air temperature to decrease. At this time, according to the original PID logic, the compressor speed will increase, and the refrigerant flow rate will further increase. Due to heat exchange reasons, the refrigerant migrates, the suction liquid is further aggravated, and the supply air temperature is difficult to reach the target value, and the system enters the control dead zone. Through relevant research, it is found that reducing the refrigerant flow rate when the compressor inhales liquid has a certain inhibitory effect on this phenomenon. Based on this, the system control area is divided into the supply air temperature, the compressor exhaust pressure target value and the current value. Figure 4 The four parts shown are used to alleviate the system suction and liquid carrying phenomenon caused by control and initial conditions when the system is not overcharged.

[0078] In the method provided by the present invention, combined with the research on the charging amount of a transcritical carbon dioxide heat pump air-conditioning system, the focus is on the control and regulation of the heat pump system and the overcharging state, and the relevant control logic is used to regulate the system control, which can solve the system imbalance problem caused by PID regulation when operating in the heat pump mode in the prior art, and can make the system have a higher energy efficiency ratio while ensuring safety; wherein, the present invention proposes a parameter for judging the degree of liquid in the air intake of a transcritical carbon dioxide heat pump, and further discloses a method for determining the control partition according to the difference between the compressor exhaust pressure and the target value and the actual value of the cabin air supply temperature; according to relevant research work, the changes in the dynamic characteristics of the system when the transcritical carbon dioxide heat pump system is overcharged, the reasons for the failure of the original control are analyzed, and relevant basis is given; and a judgment criterion for the imbalance caused by continuing to use the current PID controller is proposed, so as to know whether the system is in an imbalanced state.

[0079] The following are device embodiments of the present invention, which can be used to perform method embodiments of the present invention. For details not disclosed in the device embodiments, please refer to the method embodiments of the present invention.

[0080] See also Figure 5 In another embodiment of the present invention, a transcritical carbon dioxide air conditioning heat pump PID regulation partition control system is provided, comprising:

[0081] An acquisition module, used to acquire the liquid content of the transcritical carbon dioxide air conditioning heat pump;

[0082] 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;

[0083] Among them, the calculation expression of liquid density is:

[0084]

[0085] Where, θ is the liquid content; S suc is the inspiratory 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;

[0086] 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.

[0087] In another embodiment of the present invention, a computer device is provided, the computer device including a processor and a memory, the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc., which are the computing core and control core of the terminal, which are suitable for implementing one or more instructions, and are specifically suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used for the operation of the transcritical carbon dioxide air conditioning heat pump PID regulation partition control method.

[0088] In another embodiment of the present invention, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It is understandable that the computer-readable storage medium here can include both built-in storage media in the computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the PID regulation partition control method for a transcritical carbon dioxide air conditioning heat pump in the above embodiment.

[0089] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0090] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0091] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0092] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection 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: The following steps are involved: 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; 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; Among them, the calculation expression of liquid density is: Where, θ is the liquid content; S suc is the inspiratory 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 imbalance zone is entered.

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

3. A transcritical carbon dioxide air conditioning heat pump PID regulation zoning control method 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 transcritical carbon dioxide air conditioning heat pump PID regulation zoning control method according to claim 1, characterized in that: After obtaining the liquid content of the transcritical carbon dioxide air conditioning heat pump, the method further includes 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 performing the 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, 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 partition control system, characterized in that: include: 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 liquid content threshold, an actual exhaust pressure of the compressor, a target exhaust pressure of the compressor, an actual air supply temperature of the cabin, and a target air supply temperature of the cabin; 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; Among them, the calculation expression of liquid density is: Where, θ is the liquid content; S suc is the inspiratory 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 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 content 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 following steps are also included: 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.

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 performing the partition 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, 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.

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