CN114017898B

CN114017898B - Multi-split system

Info

Publication number: CN114017898B
Application number: CN202111312199.8A
Authority: CN
Inventors: 刘东来; 陈林; 王善云
Original assignee: Qingdao Hisense Hitachi Air Conditioning System Co Ltd
Current assignee: Qingdao Hisense Hitachi Air Conditioning System Co Ltd
Priority date: 2021-11-08
Filing date: 2021-11-08
Publication date: 2023-04-28
Anticipated expiration: 2041-11-08
Also published as: CN114017898A

Abstract

The invention relates to a multi-split system, which comprises a calculation module, a control module and a control module, wherein the calculation module calculates the difference delta P between the discharge pressure Pd and the suction pressure Ps of a compressor before the compressor is stopped when an outdoor unit receives a shutdown instruction of the last indoor unit in operation; a control module configured to perform the following pressure equalizing control: judging the size between delta P and delta P3; when delta P is less than or equal to delta P3, if the current frequency H of the compressor is greater than the safety frequency value H0 when the compressor is safely stopped, the compressor is stopped after the frequency of the compressor is reduced to be less than or equal to H0, and if H is less than or equal to H0, the compressor is stopped; when ΔP >. ΔP3, the first differential pressure control is entered when the current operation mode is the cooling mode, and the second differential pressure control is entered when the current operation mode is the heating mode. The invention effectively balances the pressure difference on the basis of not increasing hardware components, and effectively reduces the liquid return risk and noise risk.

Description

Multi-split system

Technical Field

The invention belongs to the technical field of air conditioners, and particularly relates to a multi-split system.

Background

In the conventional multi-split system, as shown in fig. 1, the multi-split system includes an outdoor unit 100 and a plurality of indoor units (only one indoor unit 200 is shown in fig. 1), and the indoor units 200 and the outdoor unit 100 are connected through refrigerant connection pipes. The indoor unit 200 is provided with an indoor heat exchanger 210, an indoor fan 220, and an indoor-side electronic expansion valve 230, and the outdoor unit 100 includes an outdoor heat exchanger 110, an outdoor fan 120, a compressor 130, a four-way valve 140, an outdoor-side electronic expansion valve 150, and an oil separator 160, which are connected by refrigerant connection lines.

After the multi-split air conditioner unit is shut down, the operation can be started again after the refrigerant pressure difference before and after the compressor 130 is balanced, otherwise, the start failure of the compressor 130 can be caused.

At present, in order to balance the refrigerant pressure difference before and after the compressor stops running, a one-way valve is generally arranged from an exhaust port to a four-way valve of the compressor, and a bypass pipeline is arranged at the joint of the one-way valve and the exhaust port and on an air return pipeline of the compressor so as to improve the speed of refrigerant pressure difference balance.

After the machine is stopped (or after the last indoor machine instruction is received), judging whether to perform refrigerant recovery operation or not, if yes, running refrigerant recovery control, and recovering the refrigerant to a high-pressure side by using a compressor running designated frequency to prepare for next starting; then, after the cold recovery operation is exited, the high-pressure refrigerant gas in the check valve from the compressor discharge port is bypassed to the low-pressure side by the bypass circuit.

However, the bypass pipeline is arranged on the exhaust pipeline and the return pipeline of the compressor, so that the complexity of the pipeline of the outdoor unit is increased, the production efficiency of the multi-split air conditioner is reduced, and the cost is increased.

To overcome the above problems, currently, the system based on fig. 1 achieves differential pressure balancing by employing a pressure equalizing control strategy. When the refrigeration is stopped, the outdoor electronic expansion valves 150 are kept in a fully opened state, and the indoor electronic expansion valves 230 of all indoor units are opened for a fixed opening degree and maintained for n seconds, so that system pressure equalization is realized; when the heating is stopped, the current opening of the indoor side electronic expansion valves 230 of all the indoor units is maintained, the outdoor side electronic expansion valve 150 is opened for a fixed opening and maintained for m seconds, and the system pressure equalizing is realized.

The scheme has two hidden troubles, (1) when a gas-liquid separator does not exist in the multi-split system and the content machine of the condenser of the outdoor unit is smaller, the refrigerant is guided to the suction side of the compressor through valve opening and pressure equalizing, and the risk of liquid return of the compressor in the starting process exists; (2) The pressure equalizing process of opening the indoor-side electronic expansion valve 230 after the cooling operation is stopped may bring about a large refrigerant flowing sound.

Disclosure of Invention

The invention aims to provide a multi-split system which is used for effectively balancing the pressure difference of a compressor on the basis of not increasing hardware components and effectively reducing the liquid return risk and the noise risk.

In order to solve the technical problems, the invention provides the following technical scheme for solving the problems:

the utility model provides a many online systems, includes indoor set and off-premises station, its characterized in that, many online systems still includes:

a calculation module for calculating a difference Δp between discharge pressure Pd and suction pressure Ps of the compressor before the outdoor unit is stopped when the outdoor unit receives a shutdown instruction of the last indoor unit in operation;

a control module configured to perform the following pressure equalizing control:

judging the size between delta P and delta P3, wherein delta P3 takes the minimum value of delta P1 and delta P2, delta P1 is a preset safe starting pressure difference of the compressor, and delta P2 is a preset pressure difference lower limit value used when the compressor is empty;

when delta P is less than or equal to delta P3, if the current frequency H of the compressor is greater than the safety frequency value H0 when the compressor is safely stopped, the compressor is stopped after the frequency of the compressor is reduced to be less than or equal to H0, and if H is less than or equal to H0, the compressor is stopped;

when delta P > -delta P3, entering a first differential pressure control when the current operation mode is a refrigeration mode, and entering a second differential pressure control when the current operation mode is a heating mode;

first differential pressure control: when H is greater than the minimum operating frequency H0 of the compressor, the compressor is frequency-reduced, delta P is obtained at fixed time, and the size between delta P and delta P3 is judged;

when delta P is less than or equal to delta P3 at a detection time t1, if H is less than or equal to H0, the unit is stopped, and if H is more than H0, the compressor is down-converted to be less than or equal to H0 and stopped;

entering a first differential pressure control when DeltaP > DeltaP3 is at t 1;

at t1, if H=h0 and DeltaP > DeltaP3, stopping the compressor, and opening a first opening degree of an electronic expansion valve of the last indoor unit when the last indoor unit is closed, and closing the indoor electronic expansion valve until DeltaP is less than or equal to DeltaP 3;

second differential pressure control: when H is more than H0, the compressor is down-converted, delta P is obtained at fixed time, and the size between delta P and delta P3 is judged;

when delta P is less than or equal to delta P3 at a detection time t2, if H is less than or equal to H0, the unit is stopped, and if H is more than H0, the compressor is down-converted to be less than or equal to H0 and stopped;

entering a second differential pressure control when DeltaP > DeltaP3 is at t 2;

at t2, if h=h0 and Δp > - Δp3, the compressor is stopped, the outdoor electronic expansion valve is opened by a second opening degree, and when Δp is less than or equal to Δp3, the outdoor electronic expansion valve is closed.

In some embodiments of the present application, in the first differential pressure control, when H > H0, while the compressor is down-converting, the outdoor fan operates at the highest gear, the outdoor electronic expansion valve is fully opened, the indoor electronic expansion valve of the indoor unit that is started to operate is controlled according to the superheat degree, and the indoor fan is set before shutdown.

In some embodiments of the present application, in the first pressure difference control, when Δp+.Δp3 at t1, if H > H0, during the compressor down-conversion, the indoor side electronic expansion valve opening and the indoor fan gear are maintained.

In some embodiments of the present application, in the first differential pressure control, at t1, if h=h0 and Δp > - Δp3, the compressor is stopped, the electronic expansion valve of the last indoor unit is opened to a first opening degree, the outdoor fan is operated at the highest gear, and the indoor fan is stopped.

In some embodiments of the present application, during the cooling mode, if it is determined that the compressor oil return operation needs to be performed, the pressure equalizing control is performed after the compressor oil return operation is completed.

In some embodiments of the present application, in the second differential pressure control, when H > H0, while the compressor is down-converting, the outdoor fan operates at the highest gear, the outdoor electronic expansion valve is controlled according to the superheat degree or the suction superheat degree of the outdoor heat exchanger, the indoor electronic expansion valve of the indoor unit that is started to operate is controlled according to the supercooling degree, and the indoor fan is set before shutdown.

In some embodiments of the present application, in the second pressure difference control, when Δp+.Δp3 at t2, if H > H0, during the compressor down-conversion, the indoor side electronic expansion valve opening and the indoor fan gear are maintained.

In some embodiments of the present application, in the second pressure difference control, at t2, if h=h0 and Δp >. Δp3, the compressor is stopped, and the outdoor-side electronic expansion valve is opened by a second opening degree, and the outdoor fan is operated at the highest gear.

In some embodiments of the present application, during the heating mode, if it is determined that the compressor oil return operation or the defrost operation needs to be performed, the pressure equalizing control is performed after the compressor oil return operation or the defrost operation is completed.

Compared with the prior art, the multi-split system provided by the invention has the following advantages and beneficial effects:

(1) Comparing the set differential pressure delta P3 with delta P, when the differential pressure value of the differential pressure delta P3 and delta P is small and the differential pressure value of the differential pressure delta P3 is smaller, when the differential pressure value of the differential pressure delta P3 and delta P reaches the shutdown condition under the safety frequency value H0 of the compressor, the safety shutdown of the compressor can be directly controlled, when the differential pressure value of the differential pressure delta P3 and delta P is larger, the differential pressure value is reduced through frequency reduction, and the differential pressure value balance before the shutdown under the safety frequency value H0 of the compressor is ensured;

(2) When the frequency of the compressor reaches the minimum operating frequency h0, in order to balance the differential pressure value, the opening degree of the indoor electronic expansion valve is required to be adjusted in a refrigerating mode, or the opening degree of the outdoor electronic expansion valve is required to be adjusted in a heating mode to realize system pressure equalizing after shutdown; when the frequency of the compressor reaches the minimum operating frequency h0, the pressure difference value is smaller than that after the compressor is directly stopped in the prior art, so that the pressure equalization is easy to realize quickly in comparison with the prior art, the adjustment quantity of the refrigerant is small, the possibility of liquid return is small, and the noise of the refrigerant is also small;

(3) The pressure equalizing scheme of the check valve and the bypass loop is arranged relatively, any hardware is not additionally added, and the hardware input cost is reduced.

Drawings

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

FIG. 1 is a block diagram of an embodiment of a multi-split system of the prior art;

FIG. 2 is a flow chart illustrating the implementation of pressure equalization control in an embodiment of the multi-split system of the present invention;

FIG. 3 is a flow chart illustrating a first differential pressure control implemented in an embodiment of the multi-split system of the present invention;

FIG. 4 is a flow chart illustrating a second differential pressure control implementation in a multi-split system according to an embodiment of the present invention.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. In the description of the present invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, merely to facilitate describing the present invention and simplify the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention.

In the description of the present invention, it should be noted that the terms "mounted," "connected," and "coupled" are to be construed broadly, as well as, for example, fixedly coupled, detachably coupled, or integrally coupled, unless otherwise specifically indicated and defined. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art. In the description of the above embodiments, particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

The terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.

Basic operation principle of air conditioner

The refrigeration cycle of the air conditioner includes a compressor, a condenser, an expansion valve, and an evaporator. The refrigeration cycle includes a series of processes involving compression, condensation, expansion, and evaporation, and supplies a refrigerant to the air that has been conditioned and heat exchanged.

The compressor compresses a refrigerant gas in a high-temperature and high-pressure state and discharges the compressed refrigerant gas. The discharged refrigerant gas flows into the condenser. The condenser condenses the compressed refrigerant into a liquid phase, and heat is released to the surrounding environment through the condensation process.

The expansion valve expands the liquid-phase refrigerant in a high-temperature and high-pressure state condensed in the condenser into a low-pressure liquid-phase refrigerant. The evaporator evaporates the refrigerant expanded in the expansion valve and returns the refrigerant gas in a low-temperature and low-pressure state to the compressor. The evaporator may achieve a cooling effect by exchanging heat with a material to be cooled using latent heat of evaporation of a refrigerant. The air conditioner may adjust the temperature of the indoor space throughout the cycle.

The air conditioner outdoor unit refers to a portion including a compressor of a refrigeration cycle and includes an outdoor heat exchanger, the air conditioner indoor unit includes an indoor heat exchanger, and the electronic expansion valve may be provided in the air conditioner indoor unit or the outdoor unit.

The indoor heat exchanger and the outdoor heat exchanger function as a condenser or an evaporator. When the indoor heat exchanger is used as a condenser, the air conditioner is used as a heater for a heating mode, and when the indoor heat exchanger is used as an evaporator, the air conditioner is used as a cooler for a cooling operation mode.

Air conditioner

The application relates to a multi-split air conditioner.

Referring to fig. 1, a block diagram of an existing air conditioner is shown.

The outdoor unit 100 includes a compressor 130, a four-way valve 140, a gas side shut-off valve (not shown), an outdoor side electronic expansion valve 150, a liquid side shut-off valve (not shown), an outdoor heat exchanger 110, and an outdoor fan 120.

The four-way valve 140 switches the flow path of the refrigerant discharged from the compressor, and has four terminals C, D, S and E.

When the four-way valve is powered down, the default C is connected with the default D, and the default S is connected with the default E, so that the indoor heat exchanger 210 is used as an evaporator, and the air conditioner is used for refrigerating.

During air conditioning refrigeration, the four-way valve 140 is turned off, the high-temperature and high-pressure gaseous refrigerant discharged from the compressor 130 is condensed into high-temperature and high-pressure liquid refrigerant in the outdoor heat exchanger 110 through the oil separator 160 and the four-way valve 140, the high-temperature and high-pressure liquid refrigerant flows into the outdoor-side electronic expansion valve 150, and the liquid refrigerant flowing out of the outdoor-side electronic expansion valve 150 flows into the indoor unit 200.

The refrigerant flowing into the indoor unit 200 is throttled into a low-temperature low-pressure liquid refrigerant by the indoor-side electronic expansion valve 230, the low-temperature low-pressure liquid refrigerant is evaporated into a low-temperature low-pressure gaseous refrigerant by the indoor heat exchanger 210, and the low-temperature low-pressure gaseous refrigerant flowing out of the indoor unit 200 flows into the suction end of the compressor 130 by the four-way valve 140.

When the four-way valve is electrified and commutated, the C and the S are connected, and the D and the E are connected, so that the indoor heat exchanger is used as a condenser and the air conditioner heats.

When the air conditioner heats, the four-way valve 140 is electrified and commutated, the high-temperature and high-pressure gaseous refrigerant discharged from the compressor 130 flows into the indoor unit 200 through the oil separator 160 and the four-way valve 140, the high-temperature and high-pressure gaseous refrigerant flowing into the indoor unit 200 is condensed into high-temperature and high-pressure liquid refrigerant in the indoor heat exchanger 210, and the liquid refrigerant flows out from the indoor electronic expansion valve 230.

The high-temperature and high-pressure liquid refrigerant flowing out of the indoor-side electronic expansion valve 230 is throttled into a low-temperature and low-pressure liquid refrigerant by the outdoor-side electronic expansion valve 150, and the low-temperature and low-pressure liquid refrigerant is evaporated into a low-temperature and low-pressure gaseous refrigerant by the outdoor heat exchanger 110, and flows into the suction end of the compressor 130 through the four-way valve 140.

In order to effectively realize system voltage sharing based on the structure of the existing multi-split system, the multi-split system further comprises a calculation module and a control module.

The specific control process of the system having the above structure may refer to flowcharts shown in fig. 2 to 4, and a specific description of these flowcharts as follows.

Pressure equalizing control

Referring to fig. 2, a flowchart of how to perform pressure equalization control on a multi-split system is shown.

The calculating module is configured to calculate a difference Δp between the discharge pressure Pd and the suction pressure Ps of the compressor 130 before the outdoor unit 100 is shut down when the outdoor unit 100 receives a shutdown command of the last indoor unit in operation.

The detection of the specific discharge pressure Pd and suction pressure Ps can be obtained by providing pressure sensors at the discharge port and suction port of the compressor.

The purpose of the obtained difference Δp is to control the Δp to reduce Δp and to ensure that the compressor discharge pressure Ps and suction pressure Ps are equalized, thereby ensuring that the compressor is shut down and reliably started again.

In order to reliably judge Δp, Δp3 is reliably set in the present application, so that the compressor 130 is reliably and safely started, and the problem that the oil pool surface falls to the empty after the compressor 130 is stopped is avoided.

In the present application, Δp3 takes the minimum value of Δp1 and Δp2, where Δp1 is a preset compressor safe start pressure difference, and Δp2 is a preset pressure difference lower limit value for the compressor 130 when empty.

The selection of Δp2 is related to the actual operation condition, and in order to ensure the reliability of Δp3, Δp2 takes the minimum value under all operation conditions and all online schemes.

Before the multi-split system under the current working condition and the online scheme is controlled, delta P3, delta P1 and delta P2 can be obtained.

Δp and Δp3 and the compressor current frequency H need to be obtained before the compressor 130 is stopped, and then the following control is performed.

S21: determining the sizes of Δp and Δp3, if Δp is less than or equal to Δp3, proceeding to S22, if Δp > - Δp3, proceeding to S25.

The determination of Δp and Δp3 as above may be performed by a determination module.

S22: whether the current frequency H of the compressor is larger than a safety frequency value H0 when the compressor is safely stopped is judged, if yes, the process goes to S23, and if not, the process goes to S24.

In this application, the judgment of H and H0 may also be performed by the judgment module.

H0 is preset, a known value, for the compressor 130.

The compressor 130 is directly stopped at the frequency H0, which is safe for the compressor 130, for the following reasons.

If the compressor 130 is directly stopped at a high frequency, i.e., the high frequency is directly reduced to 0Hz, a large reverse current is generated depending on the reverse electromagnetic resistance, and damage is caused to the driving module for driving the compressor 130, so that a safety frequency value, i.e., H0, is generally set when the compressor 130 is safely stopped for protecting the compressor 130.

S23: and (5) reducing the frequency of the compressor to be less than or equal to H0, and stopping the compressor.

ΔP is less than or equal to ΔP3, which indicates that the current ΔP is small and that the compressor 130 may be shut down.

Considering that the current frequency H of the current compressor is larger, the compressor can be directly stopped after the frequency is reduced to be less than or equal to H0, and the pressure difference delta P can be further reduced due to the reduction of the frequency of the compressor.

In the application, a fixed down-conversion speed is selected for down-conversion until the frequency is less than or equal to H0.

S24: the compressor is directly shut down.

Δp is small and the frequency of the compressor 130 satisfies the safety frequency value H0 at the time of the safety shutdown, so the compressor 130 can be directly shutdown.

S25: if the operation mode is determined to be the cooling mode or the heating mode, the process proceeds to S26, and if the operation mode is the heating mode, the process proceeds to S27.

Since the operation mode of the multi-split system has an influence on the pressure difference Δp of the compressor 130, control is performed for the heating mode and the cooling mode, respectively.

First differential pressure control

S26: a first pressure differential control is entered.

In the first differential pressure control, a compressor minimum operating frequency H0 is set, which represents a compressor minimum operating frequency that the drive module can support, and H0 > H0.

Before the compressor 130 is shut down, the frequency H > H0.

As follows, the pressure equalizing control at the compressor current frequency H > H0 will be described.

S261: the compressor down-converts and periodically acquires ΔP.

The compressor 130 frequency down can reduce the pressure differential Δp.

In this application, a fixed down-conversion speed is selected for down-conversion.

In addition, in order to increase the flow speed of the refrigerant from the high pressure to the low pressure, the outdoor fan 120 is operated at the highest gear while the compressor 130 is down-frequency, the outdoor side electronic expansion valve 150 is fully opened, the indoor side electronic expansion valve (e.g., the indoor side electronic expansion valve 230) of the indoor unit operated at the start-up is controlled according to the degree of superheat, and the indoor fan 220 is maintained at the setting before the shutdown.

The degree of superheat of the indoor heat exchanger 210 is related to the opening degree of the indoor-side electronic expansion valve 230, and when the degree of superheat is small, the opening degree of the indoor-side electronic expansion valve 230 is large, and at this time, the flow rate of the refrigerant at the indoor side is large, and the refrigerating capacity is increased; when the opening degree of the indoor-side electronic expansion valve 230 is small, the degree of superheat is large.

Accordingly, the degree of superheat can be adjusted by adjusting the opening degree of the indoor-side electronic expansion valve 230, and a corresponding refrigerating capacity can be obtained.

The target superheat degree may be set, and the opening degree of the indoor-side electronic expansion valve 230 may be adjusted according to the obtained real-time superheat degree and the target superheat degree.

For example, the real-time superheat may be obtained by calculating the difference Trg-Trl between the gas tube temperature Trg and the liquid tube temperature Trl of the indoor heat exchanger 210.

Acquisition of ΔP is described in the section above.

S262: the magnitude between Δp and Δp3 is determined at a fixed time, and if Δp is not more than Δp3 at the detection time t1, the process proceeds to S263, and if Δp > - Δp3 at t1, the process returns to S261.

Note that, although Δp > Δp3is set at t1, since the compressor 130 is not yet stopped at this time, the current compressor frequency H does not reach H0, and thus the first differential pressure control is still performed, and the process proceeds to S261.

S263: whether the current frequency H of the compressor is greater than H0 is determined, and if so, the process proceeds to S264, and if not, the process proceeds to S265.

Referring to S22, since H0 is a safe frequency value for safe shutdown of the compressor, it is preferable to safely shutdown the compressor 130 when Δp is small, and therefore, when the frequency H does not reach H0, H0 should be used as a limitation condition for shutdown.

S264: and (5) reducing the frequency of the compressor to be less than or equal to H0, and stopping the compressor.

Considering that the current frequency H of the current compressor is currently large, the compressor can be directly stopped after being down-converted to H0 or less, and the pressure difference Δp can be further reduced due to the reduction of the frequency of the compressor 130.

During this down-conversion, the opening degree of the indoor-side electronic expansion valve 230 and the shift position of the indoor fan 220 are maintained.

S265: the compressor is directly shut down.

The compressor is stopped as described above, and the compressor 130 is stopped at the safety frequency value H0 under the premise of controlling Δp.ltoreq.Δp3.

Pressure equalizing according to need

S266: if h=h0 at the detection time t1, the magnitudes of Δp and Δp3 are determined, and if Δp > - Δp3, the process proceeds to S267.

When the compressor 130 frequency H reaches H0, the compressor 130 is shut down.

After the compressor 130 is shut down, the pressure equalization is performed on demand, referred to as "on demand pressure equalization".

That is, when ΔP >. ΔP3, it is necessary to perform pressure equalization on the system, and when ΔP is not more than ΔP3, it is unnecessary to perform pressure equalization on the system, and the machine unit is directly stopped.

S267: and stopping the compressor, opening the first opening degree of the indoor electronic expansion valve of the last indoor unit in operation, and closing the indoor electronic expansion valve when the detected delta P is less than or equal to delta P3.

After the compressor 130 is shut down, in the cooling mode, the indoor-side electronic expansion valve (for example, the indoor-side electronic expansion valve 230) of the last indoor unit is opened by a first opening degree to realize system pressure equalization, and the pressure equalization is completed until Δp is detected to be less than or equal to Δp3, at this time, the indoor-side electronic expansion valve 230 is closed.

In addition, in order to accelerate the flow rate of the refrigerant from the high pressure to the low pressure, the outdoor fan 120 is ensured to be operated at the highest gear while the first opening degree is opened, and the indoor fan 220 is stopped.

Therefore, after the on-demand pressure equalizing control is completed, the whole unit is stopped except that the indoor-side electronic expansion valve 230 is closed.

In S267, since the frequency of the compressor 130 has been previously adjusted to h0 and since h0 is the minimum compressor operating frequency, it is definitely lower than the normal compressor operating frequency, even if Δp greater than Δp3 is present at the h0 frequency of the compressor 130, Δp' greater than Δp3 is much smaller than that present at the normal compressor operating frequency in the related art.

Namely, Δp' > "Δp >" Δp3.

Therefore, the indoor electronic expansion valve is opened at the moment, so that pressure equalization in a system refrigeration mode is easier and faster to realize, and the probability of liquid return and noise is effectively reduced.

If it is determined that the compressor oil return operation is to be executed during the cooling mode, the above-described pressure equalizing control is executed after the completion of the compressor oil return operation.

Compressor oil return operation refers to the system determining whether oil return is required after a period of long-term low frequency operation of compressor 130.

For example, if the compressor 130 is operated at 20Hz for 1 hour, the system considers that oil should be returned because at low frequencies, compressor oil is not circulated, most of the oil is outside the system and not returned to the compressor 130, which for a long time may cause starvation of the compressor 130, and risk wear.

A typical oil return operation, such as (1) returning oil from the exhaust gas to the compressor 130 via an oil separator 160; (2) Oil return is accomplished by a specific oil return procedure, primarily by returning oil to the compressor 130 via return air.

Second differential pressure control

S27: and enter a second differential pressure control.

In the second differential pressure control, a compressor minimum operating frequency H0 is set, which represents a compressor minimum operating frequency that the driving module can support, and H0 > H0.

Before the compressor 130 is shut down, the frequency H > H0.

S271: the compressor down-converts and periodically acquires ΔP.

The compressor 130 frequency down can reduce the pressure differential Δp.

In addition, in order to increase the flow speed of the refrigerant from the high pressure to the low pressure, the outdoor fan 120 is operated at the highest gear while the compressor 130 is down-frequency, the outdoor side electronic expansion valve is controlled according to the superheat degree of the outdoor heat exchanger 110 or the suction superheat degree, the electronic expansion valve (e.g., the indoor side electronic expansion valve 230) of the indoor unit operated at the start-up is controlled according to the supercooling degree, and the indoor fan 220 is maintained at the setting before the shutdown.

The indoor-side electronic expansion valve 230 of the indoor unit operated at the start-up is described in terms of supercooling degree control.

The degree of supercooling of the indoor heat exchanger 210 is related to the opening degree of the indoor-side electronic expansion valve 230, and when the degree of supercooling is small, the opening degree of the indoor-side electronic expansion valve 230 is large, and at this time, the refrigerant flow rate of the indoor unit is large, and the heating capacity is increased; when the opening degree of the indoor-side electronic expansion valve 230 is small, the supercooling degree is large.

Accordingly, the degree of supercooling can be adjusted by adjusting the opening degree of the indoor-side electronic expansion valve 230, so that the corresponding heating capacity can be obtained.

The target supercooling degree may be set, and the opening degree of the indoor-side electronic expansion valve 230 may be adjusted according to the acquired real-time supercooling degree and target supercooling degree.

For example, the real-time supercooling degree can be obtained by the difference Tc-Trl between the refrigerant saturation temperature Tc and the liquid tube temperature Trl of the indoor heat exchanger of each operation indoor unit.

Acquisition of ΔP is described in the section above.

S272: the magnitude between Δp and Δp3 is determined at the timing, and if Δp is not more than Δp3 at the detection time t2, the process proceeds to S273, and if Δp > - Δp3 at t2, the process returns to S271.

Note that, although Δp > Δp3is set at t2, since the compressor 130 is not yet stopped at this time, the current compressor frequency H does not reach H0, and thus the second differential pressure control is still performed, and the process proceeds to S271.

S273: whether the current frequency H of the compressor is greater than H0 is determined, and if so, the process proceeds to S274, and if not, the process proceeds to S275.

S274: and (5) reducing the frequency of the compressor to be less than or equal to H0, and stopping the compressor.

S275: the compressor is directly shut down.

Pressure equalizing according to need

S276: if h=h0 at the detection time t2 and the magnitudes of Δp and Δp3 are determined, if Δp > - Δp3, the process proceeds to S277.

S277: and stopping the compressor, opening the outdoor electronic expansion valve by a second opening degree, and closing the outdoor electronic expansion valve until the detected delta P is less than or equal to delta P3.

After the compressor 130 is stopped, in the heating mode, the outdoor electronic expansion valve (for example, the outdoor electronic expansion valve 150) is opened by a second opening degree to realize the system pressure equalization, and the pressure equalization is completed until Δp is detected to be equal to or smaller than Δp3, at which time the outdoor electronic expansion valve 150 is closed.

In addition, in order to accelerate the flow speed of the refrigerant from the high pressure to the low pressure, the second opening is opened while ensuring that the outdoor fan 120 is operated at the highest gear, and the opening of the indoor-side electronic expansion valve 230, the indoor fan 220, is controlled according to the normal heating or residual heat blowing.

It should be noted that, the waste heat blowing control herein means that when the heating indoor unit receives a shutdown instruction, the air supply process is not immediately stopped, and the heat in the indoor heat exchanger 210 is released for a period of time, so that the heat is fully utilized by a user.

The control of the waste heat of blowing is also a common control mode in the air conditioner, and will not be described in detail herein.

Therefore, after the on-demand pressure equalizing control is completed, the entire unit is stopped except for closing the outdoor-side electronic expansion valve 150.

In S277, since the frequency of the compressor 130 has been previously adjusted to h0 and since h0 is the minimum operating frequency of the compressor, it is definitely lower than the normal operating frequency of the compressor, even if Δp greater than Δp3 is present at the frequency h0 of the compressor 130, Δp' greater than Δp3 is considerably smaller than that present at the normal operating frequency of the compressor in the related art.

Namely, Δp' > "Δp >" Δp3.

Therefore, the outdoor electronic expansion valve is opened at the moment, so that pressure equalization under the condition of heating of the system is easier and faster to realize, and the probability of liquid return and noise is effectively reduced.

If it is determined that the compressor oil return operation or the defrosting operation needs to be performed during the heating mode, the above-described pressure equalizing control is performed after the compressor oil return operation or the defrosting operation is completed.

The utility model provides a many online systems can be under the condition that does not additionally increase any hardware, realizes the system pressure-equalizing before shutting down, and realizes the pressure-equalizing as required after shutting down, when can guaranteeing the system pressure-equalizing, reduces liquid return danger and refrigerant flow noise.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. The utility model provides a many online systems, includes indoor set and off-premises station, its characterized in that, many online systems still includes:

a calculation module for calculating a difference Δp between the discharge pressure Pd and the suction pressure Ps of the compressor before the shutdown when the outdoor unit receives a shutdown instruction of the last indoor unit in operation;

when delta P is less than or equal to delta P3 at a detection time t1, if H is less than or equal to H0, stopping the unit, and if H is more than H0, reducing the frequency of the compressor to be less than or equal to H0;

entering a first differential pressure control when DeltaP > DeltaP3 is at t 1;

at t1, if H=h0 and DeltaP > DeltaP3, stopping the compressor, and opening the indoor electronic expansion valve of the last indoor unit to a first opening degree until DeltaP is less than or equal to DeltaP 3, and closing the indoor electronic expansion valve;

2. The multiple on-line system according to claim 1, wherein in the first pressure difference control, when H > H0, the compressor is down-converted, the outdoor fan is operated at the highest gear, the outdoor side electronic expansion valve is fully opened, the indoor side electronic expansion valve of the indoor unit operated at the start-up is controlled according to the degree of superheat, and the indoor fan is kept at the setting before the shutdown.

3. The variable refrigerant flow system according to claim 1, wherein in the first pressure difference control, when Δp is equal to or smaller than Δp3 at t1, if H > H0, the indoor electronic expansion valve opening and the indoor fan gear are maintained during the compressor frequency-reducing period.

4. The multiple on-line system according to claim 1, wherein in the first pressure difference control, if h=h0 and Δp > - Δp3, the compressor is stopped, the electronic expansion valve of the last indoor unit is opened to a first opening degree, the outdoor fan is operated at the highest gear, and the indoor fan is stopped.

5. The multiple on-line system according to any one of claims 1 to 4, wherein during the cooling mode, if it is determined that the compressor oil return operation needs to be performed, the pressure equalizing control is performed after the compressor oil return operation is completed.

6. The multiple on-line system according to claim 1, wherein in the second pressure difference control, when H > H0, the compressor is down-converted, the outdoor fan is operated at the highest gear, the outdoor electronic expansion valve is controlled according to the superheat degree of the outdoor heat exchanger or the suction superheat degree, the indoor electronic expansion valve of the indoor unit operated at the start-up is controlled according to the supercooling degree, and the indoor fan is kept at the setting before the shutdown.

7. The variable refrigerant flow system according to claim 1, wherein in the second pressure difference control, when Δp is equal to or smaller than Δp3 at t2, if H > H0, the indoor electronic expansion valve opening and the indoor fan gear are maintained during the compressor frequency-down period.

8. The variable refrigerant flow system according to claim 1, wherein in the second pressure difference control, at t2, if h=h0 and Δp > - Δp3, the compressor is stopped, and the outdoor-side electronic expansion valve is opened by a second opening degree, and the outdoor fan is operated at a highest gear.

9. The multiple on-line system according to any one of claims 6 to 8, wherein during the heating mode, if it is determined that the compressor oil return operation or the defrost operation needs to be performed, the pressure equalizing control is performed after the compressor oil return operation or the defrost operation is completed.