CN109682021B

CN109682021B - Outdoor unit protection method and device and air conditioning system

Info

Publication number: CN109682021B
Application number: CN201811527352.7A
Authority: CN
Inventors: 李丛来; 宋旭彤; 张恒; 颜鹏
Original assignee: Qingdao Hisense Hitachi Air Conditioning System Co Ltd
Current assignee: Qingdao Hisense Hitachi Air Conditioning System Co Ltd
Priority date: 2018-12-13
Filing date: 2018-12-13
Publication date: 2021-05-14
Anticipated expiration: 2038-12-13
Also published as: CN109682021A

Abstract

The invention discloses an outdoor unit protection method and device and an air conditioning system, and relates to the technical field of air conditioners. The outdoor unit protection method comprises the following steps: judging the working state of the outdoor unit; if the outdoor unit is in the combined working state, judging whether an outdoor unit in a working stop state exists in the outdoor unit; if the outdoor unit in the stop state exists in the outdoor unit set, the opening K of an expansion valve contained in the outdoor unit in the stop state is controlled to be more than 0. The outdoor unit protection device applies the outdoor unit protection method. The invention provides an outdoor unit protection method and device and an air conditioning system, which are used in the field of air conditioners.

Description

Outdoor unit protection method and device and air conditioning system

Technical Field

The invention relates to the technical field of air conditioners, in particular to an outdoor unit protection method and device and a refrigeration system.

Background

In the prior art, a central air conditioner is widely used in large buildings such as schools, companies and hotels, and comprises a plurality of indoor units installed indoors and an outdoor unit installed outdoors, wherein the outdoor unit comprises a plurality of outdoor units connected in parallel.

Each outdoor unit comprises a compressor, a one-way valve and an expansion valve, wherein the one-way valve and the expansion valve are positioned on the exhaust side of the compressor, a bypass loop is arranged between the one-way valve and the expansion valve, and the bypass loop is used for controlling whether the exhaust side and the suction side of the compressor are communicated or not. When one outdoor unit stops working, the accumulated refrigerant is condensed in the pipeline between the one-way valve and the expansion valve along with the change of outdoor working conditions, so that the pressure of the pipeline between the one-way valve and the expansion valve is increased, and the exhaust pressure of the compressor is increased. When the discharge pressure of the compressor reaches the discharge threshold, the outdoor unit protection device sends a unit stop instruction to control all outdoor units included in the outdoor unit to stop so as to ensure the safety of the outdoor unit, but the central air conditioner stops running completely. Therefore, when one outdoor unit stops working, the bypass circuit SVA included in the outdoor unit which stops working can be opened, so that the refrigerant accumulated between the one-way valve and the expansion valve can return to the inlet of the compressor through the bypass circuit SVA, and the compressor is subjected to liquid impact when being started next time.

Disclosure of Invention

The invention aims to provide an outdoor unit protection method and device and a refrigeration system, which are used for preventing the outdoor unit which stops working from being liquid knocked in the next starting process while ensuring the normal working of other outdoor units when one outdoor unit stops working.

In order to achieve the above object, the present invention provides a method for protecting an outdoor unit, comprising:

judging the working state of the outdoor unit;

if the outdoor unit is in the combined working state, judging whether an outdoor unit in a working stop state exists in the outdoor unit;

if the outdoor unit in the stop state exists in the outdoor unit set, the opening K of an expansion valve contained in the stop outdoor unit is controlled to be more than 0, so that the discharge pressure P of a compressor contained in the stop outdoor unit is less than P_max，P_maxIs the discharge pressure threshold of the compressor.

Compared with the prior art, in the outdoor unit protection method provided by the invention, if the outdoor unit in the stop working state exists in the outdoor unit, the opening K of the expansion valve contained in the outdoor unit in the stop working state is controlled to be more than 0, so that the refrigerant condensed in the pipeline between the one-way valve and the expansion valve can enter the whole pipelineIn the pipeline of the air conditioning system, the pipeline pressure between the one-way valve and the expansion valve can be reduced, so that the discharge pressure P of the compressor included in the outdoor unit which stops working is less than the discharge pressure threshold value P_max. And when the outdoor unit stops working, the discharge pressure P of the compressor is less than the discharge pressure threshold P_maxWhen the outdoor unit in the outdoor unit group stops working due to a fault and the like, the outdoor unit in the outdoor unit group in the normal working state can normally work when the outdoor unit group is in the combined working state. In addition, in the method for protecting the outdoor unit, the refrigerant condensed in the pipeline between the one-way valve and the expansion valve is not required to be sent to the suction side of the compressor by utilizing the SVA, so that the outdoor unit which stops working is prevented from being impacted by liquid when being started next time.

The invention also provides an outdoor unit protection device, which comprises:

the first judgment module is used for judging the working state of the outdoor unit;

the second judgment module is used for judging whether the outdoor unit in a working stop state exists in the outdoor unit when the outdoor unit is in a combined working state;

a valve control module for controlling the opening K of the expansion valve contained in the outdoor unit with stopping work to be more than 0 when the outdoor unit with stopping work exists in the outdoor unit group, so that the discharge pressure P of the compressor contained in the outdoor unit with stopping work is less than P_max，P_maxIs an exhaust pressure threshold.

Compared with the prior art, the beneficial effects of the outdoor unit protection device provided by the invention are the same as those of the outdoor unit protection method, and are not repeated herein.

The invention also provides a computer storage medium for storing one or more computer instructions, wherein the computer software instructions comprise a computer program designed for executing the outdoor unit protection method.

The invention also provides an air conditioning system which comprises the outdoor unit protection device in the technical scheme.

Compared with the prior art, the beneficial effect of the air conditioning system provided by the invention is the same as that of the protection method of the outdoor unit, and the description is omitted here.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 is a schematic structural diagram of an air conditioning system according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of an outdoor unit according to an embodiment of the present invention;

fig. 3 is a first flowchart of a protection method for an outdoor unit according to an embodiment of the present invention;

fig. 4 is a second flowchart of a protection method for an outdoor unit according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of an outdoor unit protection device according to an embodiment of the present invention;

fig. 6 is an architecture diagram of an outdoor unit protection device according to an embodiment of the present invention.

Reference numerals:

100-indoor unit group, 110-indoor unit;

200-outdoor unit group, 210-outdoor unit;

210A-compressor, 210B-heat exchanger;

211-a first outdoor unit, 212-a second outdoor unit;

213-a third outdoor unit, 214-a fourth outdoor unit;

300-outdoor unit protection device, 310-first judgment module;

320-a second judgment module, 330-a third judgment module;

340-a fourth judging module, 350-a first state confirming module;

360-a second status confirmation module, 370-a valve control module;

410-inlet manifold, 420-outlet manifold;

500-outdoor unit protection terminal, 510-memory;

520-processor, 530-transceiver;

540-bus, EVO-expansion valve;

FV-four-way valve, SVA-bypass circuit;

VD-check valve.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1, an embodiment of the present invention provides an air conditioning system including an indoor unit 100, an outdoor unit 200, and an outdoor unit protection device 300 for protecting the outdoor unit 200. The outdoor unit protection device 300 can prevent the outdoor unit 210 which is stopped from being liquid-impacted when the next start is performed, while ensuring the normal operation of the other outdoor units 210 when one of the outdoor units 210 stops operating.

For example, as shown in fig. 1 and 2, the indoor unit 100 includes 8 indoor units 110, the outdoor unit 200 includes 4 outdoor units 210, and the 4 outdoor units 210 are a first outdoor unit 211, a second outdoor unit 212, a third outdoor unit 213, and a fourth outdoor unit 214, respectively. Each outdoor unit 210 mainly comprises a compressor 210A and a heat exchanger 210B, and in addition, further comprises a one-way valve VD, a four-way valve FV and an expansion valve EVO arranged on the heat exchanger 210B, wherein the exhaust side of the compressor 210A is connected with the inlet of the one-way valve VD, the outlet of the one-way valve VD is connected with a first interface of the four-way valve FV, a second interface of the four-way valve FV is connected with the inlet of each outdoor unit 210 in the outdoor unit 200 through an inlet manifold 410, an outlet manifold 420 of each outdoor unit 210 in the outdoor unit 200 is connected with a first heat exchange interface of the heat exchanger 210B, a second heat exchange interface of the heat exchanger 210B is connected with a third interface of the four-way valve FV, and a fourth interface of the four-way valve FV; meanwhile, a pipeline between the outlet of the one-way valve VD and the first interface of the four-way valve FV is communicated with the heat absorption side of the compressor 210A through a bypass circuit SVA, the bypass circuit SVA can be connected with the pipeline between the outlet of the one-way valve VD and the first interface of the four-way valve FV and the heat absorption side of the compressor 210A, and a bypass valve is arranged on the bypass circuit SVA and used for controlling the bypass circuit SVA to be opened or closed. In fig. 1, a direction indicated by a solid arrow is an operation direction of the refrigerant in the air conditioning system pipeline when the refrigerant is introduced into the indoor unit 100, and a direction indicated by a dotted arrow is an operation direction of the refrigerant in the air conditioning system pipeline when the refrigerant flows out of the indoor unit 100.

As can be seen in conjunction with fig. 1 and 2: when any one of the 4 outdoor units 210 stops operating, the compressor 210A and the expansion valve EVO included in the outdoor unit 210 that stops operating are both automatically closed, so that gaseous refrigerant (high temperature and high pressure) in the pipeline between the one-way valve VD and the expansion valve EVO accumulates, and as the outdoor temperature rises, liquid refrigerant in the pipeline between the one-way valve VD and the expansion valve EVO is gradually changed into gaseous refrigerant, so that the discharge pressure of the compressor 210A increases.

For the sake of clarity, the protection device 300 and the protection method for outdoor units according to the present invention will be described in detail with reference to the accompanying drawings.

As shown in fig. 1 to 3, an embodiment of the present invention provides an outdoor unit protection method, including:

step S100: judging the working state of the outdoor unit 200;

if the outdoor unit 200 is in the combined operation state, step S200 is performed.

If the outdoor unit set 200 is in the independent working state, it is described that the outdoor units 210 in the outdoor unit set 200 do not affect each other, that is, one of the outdoor units 210 stops working and does not affect the working of the other outdoor units 210, and in this case, the process can be finished without protecting the outdoor unit set 200.

Step S200: judging whether an outdoor unit 210 in a stopped state exists in the outdoor unit 200;

if the outdoor unit 210 in the stopped state exists in the outdoor unit set 200, step S400 is performed.

If there is no outdoor unit 210 in the stopped state in the outdoor unit 200, it is described that each outdoor unit 210 in the outdoor unit 200 normally operates, and in this case, the process can be terminated without protecting the outdoor unit 200.

Step S400: the opening K of the expansion valve EVO included in the outdoor unit 210 stopped is controlled to be greater than 0 so that the discharge pressure P of the compressor 210A included in the outdoor unit 210 stopped is controlled to be less than P_max，P_maxIs the discharge pressure threshold of the compressor 210A.

Based on the above-mentioned outdoor unit protection method, if the outdoor unit 210 in the stopped state exists in the outdoor unit 200, the opening degree of the expansion valve EVO included in the outdoor unit 210 in the stopped state is controlled to be greater than 0, so that the refrigerant condensed in the pipeline between the one-way valve VD and the expansion valve EVO can enter the pipeline of the whole air conditioning system, and thus the pipeline pressure between the one-way valve VD and the expansion valve EVO can be reduced, and the discharge pressure P of the compressor 210A included in the outdoor unit 210 in the stopped state is smaller than the discharge pressure threshold P_max. And the discharge pressure P of the compressor 210A included in the outdoor unit 210 stopped is less than the discharge pressure threshold P_maxIn this case, the outdoor unit protection device 300 does not issue a shutdown command to the outdoor units 210 in the normal operating state in the outdoor unit 200, so that when one of the outdoor units 210 in the outdoor unit 200 stops operating due to a failure or the like, the outdoor unit 210 in the normal operating state in the outdoor unit 200 can normally operate when the outdoor unit 200 is in the combined operating state. In addition, in the above method for protecting the outdoor unit, the refrigerant condensed in the pipe between the check valve VD and the expansion valve EVO is not sent to the suction side of the compressor by the bypass circuit SVA, so that the outdoor unit 210 which stops working is prevented from being hit by liquid at the next start.

In some embodiments, as shown in fig. 1 to 3, when the outdoor unit 210 stops operating, the compressor 210A included in the outdoor unit 210 stops operating, and the compressor operating frequency Ft is 0. Accordingly, the above determining whether or not the outdoor unit 200 has an outdoor unit in a stopped state includes:

step S200: determining whether the compressor operating frequency Ft included in each outdoor unit 210 included in the outdoor unit 200 is equal to 0;

if the operating frequency Ft of the compressor included in at least one outdoor unit 210 included in the outdoor unit 200 is equal to 0, step S210 is performed.

If the operating frequency Ft of the compressor included in each outdoor unit included in the outdoor unit set is greater than 0, step S220 is performed.

Step S210: the outdoor unit 210 which stops working is determined in the outdoor unit set 200, and the outdoor unit 210 which stops working in the outdoor unit set 200 is determined according to the working frequency Ft of the compressor.

Step S220: it is determined that each outdoor unit 210 in the outdoor unit set 200 is in an operating state.

Alternatively, as shown in fig. 1 to 3, in order to more accurately control the protection of the outdoor unit set 200 and reduce unnecessary protection operations of the outdoor unit set 200, if the outdoor unit set 200 has an outdoor unit 210 that is stopped, before the opening K of an expansion valve EVO included in the outdoor unit 210 that is stopped is controlled to be greater than 0, the method for protecting the outdoor unit set further includes:

step S300: it is determined whether or not the discharge pressure P of the compressor 210A included in the outdoor unit 210 stopped is equal to or greater than P_max；

If P < P_maxIt is to be noted that although the outdoor unit 210 is in a stop state, the line pressure between the check valve VD and the expansion valve EVO in the outdoor unit 210 can still ensure that the discharge pressure P of the compressor 210A in the outdoor unit 210 is within a safe range, at this time, step S310 is executed,

if P is greater than or equal to P_maxIt is explained that although the outdoor unit 210 is in the stopped state, the line pressure between the check valve VD and the expansion valve EVO in the outdoor unit 210 is already such that the outdoor unit 210 is in the stopped stateThe discharge pressure P of the compressor 210A in the outdoor unit 210 exceeds the standard, and the outdoor unit 210 has a safety hazard, at this time, step S320 is executed.

Step S310: it is determined that the outdoor unit 210, which stops operating in the outdoor unit 200, is in a safe state, and in this case, the process can be terminated without protecting the outdoor unit 200.

Step S320: it is determined that the outdoor unit 210, which stops operating in the outdoor unit set 200, is in an abnormal state, and step S400 is performed.

As can be seen from the above process, when the outdoor unit 210 which is in the stopped state exists in the outdoor unit set 200, the opening degree K of the expansion valve EVO included in the outdoor unit 210 which is in the stopped state is not necessarily controlled, and the opening degree K of the expansion valve EVO included in the outdoor unit 210 which is in the stopped state needs to be controlled only when it is determined that the outdoor unit 210 which is in the stopped state exists in the outdoor unit set 200, so that unnecessary protection operations of the outdoor unit set can be reduced.

In some embodiments, as shown in fig. 1, 2 and 4, the above-mentioned controlling of the opening K > 0 of the expansion valve EVO included in the deactivated outdoor unit 210 makes the discharge pressure P < P of the compressor 210A included in the deactivated outdoor unit 210_maxThe method comprises the following steps:

step S410: the opening K of the expansion valve EVO included in the outdoor unit 210 that has stopped operating is controlled.

Step S420: it is determined whether the discharge pressure P of the compressor 210A included in the outdoor unit 210 stopped is equal to P_maxK, k > 0, and the size of k may be set according to practical situations, for example, k is 0.3-0.8, when k is 0.5, the outdoor unit 210 which is stopped can be effectively ensured to be in a safe state, and the pipeline pressure of the outdoor unit 210 can be rapidly balanced at the next start.

If P ═ P_maxK, performing step S430.

If P > P_maxK, performing step S440.

Step S430: when P is equal to P_maxK, indicating that the outdoor unit 210 is in a safe state, and only the expansion valve EVO is closed, i.e. the opening of the expansion valve EVO included in the outdoor unit 210 is controlledAnd the degree K is 0, and the process is ended.

Step S440: the opening K of the expansion valve EVO included in the outdoor unit 210 stopped is controlled to change.

As shown in fig. 1 to 3 and 5, an embodiment of the present invention further provides an outdoor unit protection device 300, where the outdoor unit protection device 300 includes:

a first judging module 310, configured to judge a working state of the outdoor unit 200;

the second judging module 320 connected to the first judging module 310 is configured to judge whether the outdoor unit 200 has the outdoor unit 210 in the stopped state when the outdoor unit 200 is in the combined working state;

the valve control module 370 connected to the second determination module 320 controls the opening K of the expansion valve EVO included in the outdoor unit 210 stopped to be greater than 0 such that the discharge pressure P of the compressor 210A included in the outdoor unit 210 stopped to be less than P when the outdoor unit 210 stopped to be operated exists in the outdoor unit 200_max，P_maxIs an exhaust pressure threshold.

It can be understood that, when the valve control module 370 controls the opening K of the expansion valve EVO included in the outdoor unit 210 that stops working, the expansion valve EVO included in the outdoor unit 210 that stops working is the electromagnetic expansion valve EVO, so as to ensure that the valve control module can control the opening of the expansion valve EVO.

Compared with the prior art, the beneficial effects of the outdoor unit protection device 300 provided by the embodiment of the invention are the same as those of the outdoor unit protection method, and are not described herein again.

In some embodiments, as shown in fig. 1 to fig. 3 and fig. 5, the second determining module 320 is specifically configured to determine whether the operating frequency Ft of the compressor included in each outdoor unit 210 included in the outdoor unit set 200 is equal to 0;

the outdoor unit protection device 300 further includes a first status confirmation module 350, configured to determine that there is an outdoor unit 210 that stops operating in the outdoor unit 200 when an operating frequency Ft of a compressor included in at least one outdoor unit included in the outdoor unit is equal to 0, determine the outdoor unit 210 that stops operating in the outdoor unit 200 according to the operating frequency Ft of the compressor, and determine that each outdoor unit 210 in the outdoor unit 200 is in an operating state when the operating frequency Ft of the compressor included in each outdoor unit included in the outdoor unit is greater than 0.

In some embodiments, as shown in fig. 1 to 3 and 5, the outdoor unit protection device 300 further includes:

a third determining module 330 connected to the second determining module 320 and the valve controlling module 370, for determining whether or not a discharge pressure P of a compressor 210A included in the outdoor unit 210 stopped in operation is equal to or greater than P before controlling an opening K of an expansion valve EVO included in the outdoor unit 210 stopped in operation to be greater than 0 when the outdoor unit 210 stopped in operation exists in the outdoor unit 200_max(ii) a The discharge pressure P of the compressor 210A included in the outdoor unit 210 that has stopped operating may be obtained by a pressure sensor.

A second status confirmation module 360 connected to the third determination module 330 for confirming whether P is greater than or equal to P_maxWhen the operation is stopped, it is determined that the outdoor unit 210 in the outdoor unit 200 is in an abnormal state; at P < P_maxWhen the outdoor unit 210 stops working in the outdoor unit 200, determining that the outdoor unit is in a safe state;

the valve control module 370 is specifically configured to control the valve when P ≧ P_maxIn this case, the opening K of the expansion valve EVO included in the outdoor unit 210 stopped is controlled to be larger than 0.

In some embodiments, as shown in fig. 1, 2, 4 and 5, the valve control module 370 is specifically configured to control an opening K of an expansion valve EVO included in the outdoor unit 210 that stops working;

the outdoor unit protection device 300 further includes a fourth determining module 340 for determining whether a discharge pressure P of the compressor 210A included in the outdoor unit 210 stopped is equal to P_max-k, k > 0, optionally k is 0.3 to 0.8.

The valve control module 370 is also configured to control the valve when P is equal to P_maxWhen K is the value, the opening K of the expansion valve EVO included in the outdoor unit 210 stopped is controlled to be 0; in the case of P > P_maxK times, the expansion of the outdoor unit 210 which is stoppedThe opening K of the expansion valve EVO changes.

The embodiment of the invention also provides an air conditioning system, which comprises the outdoor unit protection device 300.

As shown in fig. 1, compared with the prior art, the beneficial effects of the air conditioning system provided by the embodiment of the present invention are the same as those of the protection method for the outdoor unit, and are not described herein again.

The embodiment of the invention also provides a computer storage medium for storing one or more computer instructions, wherein the computer software instructions comprise a computer program designed for executing the outdoor unit protection method.

Compared with the prior art, the beneficial effects of the computer storage medium provided by the embodiment of the invention are the same as those of the protection method of the outdoor unit, and are not repeated herein.

As shown in fig. 6, an embodiment of the present invention further provides an outdoor unit protection terminal 500, which includes a processor 520, a transceiver 530, a memory 510, and a bus 540, wherein the processor 520, the transceiver 530, and the memory 510 communicate with each other through the bus 540. Wherein the content of the first and second substances,

the memory 510 is used for storing a plurality of instructions to implement the above-mentioned outdoor unit protection method, and the processor 520 executes the plurality of instructions to implement the above-mentioned outdoor unit protection method.

The processor 520 according to the embodiment of the present invention may be a single processor, or may be a general term for multiple processing elements. For example, the processor 520 may be a Central Processing Unit (CPU), an Application Specific Integrated Circuit (ASIC), or one or more Integrated circuits configured to implement embodiments of the present invention, such as: one or more microprocessors (digital signal processors, DSP for short), or one or more Field Programmable Gate arrays (FPGA for short).

The memory 510 may be a single storage device or a combination of storage elements, and is used for storing executable program codes and the like. And the memory 510 may include a Random Access Memory (RAM) and may also include a non-volatile memory (non-volatile memory), such as a magnetic disk memory, Flash memory (Flash), and the like.

The bus 540 may be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, an Extended ISA (EISA) bus, or the like. The bus 540 may be divided into an address bus, a data bus, a control bus, and the like. For ease of illustration, only one thick line is shown in FIG. 6, but this is not intended to represent only one bus or type of bus.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the apparatus embodiment, since it is substantially similar to the method embodiment, it is relatively simple to describe, and reference may be made to some descriptions of the method embodiment for relevant points.

It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. A method for protecting an outdoor unit set, wherein the outdoor unit set is composed of a plurality of outdoor units connected in parallel, each outdoor unit comprises a compressor, a one-way valve and an expansion valve which are positioned on the exhaust side of the compressor, and the compressor and the expansion valve of the outdoor unit which stops working are automatically closed, and the method is characterized by comprising the following steps of:

judging the working state of the outdoor unit;

2. The method as claimed in claim 1, wherein the determining whether there is an outdoor unit in a stopped state in the outdoor unit includes:

judging whether the working frequency Ft of a compressor included in each outdoor unit in the outdoor unit set is equal to 0 or not;

if the working frequency Ft of a compressor included in at least one outdoor unit in the outdoor unit set is equal to 0, determining that the outdoor unit which stops working exists in the outdoor unit set, and determining the outdoor unit which stops working in the outdoor unit set according to the working frequency Ft of the compressor;

and if the working frequency Ft of the compressor included by each outdoor unit in the outdoor unit set is greater than 0, determining that each outdoor unit in the outdoor unit set is in a working state.

3. The method of claim 1, wherein if there is an outdoor unit in the outdoor unit that is in a stopped state, the method further comprises, before controlling an opening K of an expansion valve included in the stopped outdoor unit to be greater than 0:

judging whether the discharge pressure P of the compressor included in the outdoor unit stopped working is more than or equal to P_max；

If P is greater than or equal to P_maxDetermining that the outdoor unit which stops working in the outdoor unit is in an abnormal state, and controlling the opening K of an expansion valve contained in the outdoor unit which stops working to be larger than 0;

if P < P_maxAnd determining that the outdoor unit which stops working in the outdoor unit set is in a safe state.

4. The outdoor unit protection method according to claim 1, wherein the expansion valve opening K of the outdoor unit controlled to stop operating is larger than 0, so that a discharge pressure P < P of a compressor included in the outdoor unit controlled to stop operating is smaller than P_maxThe method comprises the following steps:

controlling an opening degree K of an expansion valve included in the outdoor unit which stops working;

judging whether the discharge pressure P of the compressor included in the outdoor unit stopped is equal to P_max-k，k＞0；

If P ═ P_maxK, controlling an opening K of an expansion valve included in the stopped outdoor unit to 0;

if P > P_maxK, controlling the opening degree K of the expansion valve contained in the stopped outdoor unit to change.

5. The outdoor unit protection method according to claim 4, wherein k is 0.3 to 0.8.

6. The utility model provides an outdoor unit protection device, outdoor unit comprises many off-premises stations that connect in parallel together, every off-premises station includes the compressor and is located the check valve and the expansion valve of compressor discharge side, the compressor and the expansion valve that the off-premises station that stop work included all self-closing, its characterized in that includes:

valve controlA control module for controlling the opening K of the expansion valve contained in the outdoor unit which stops working to be more than 0 when the outdoor unit which stops working exists in the outdoor unit group, so that the discharge pressure P of the compressor contained in the outdoor unit which stops working is less than P_max，P_maxIs an exhaust pressure threshold.

7. The outdoor unit protection device according to claim 6, wherein the second determining module is specifically configured to determine whether an operating frequency Ft of a compressor included in each outdoor unit included in the outdoor unit is equal to 0;

the outdoor unit protection device further comprises a first state confirmation module, wherein the first state confirmation module is used for determining that the outdoor unit which stops working exists in the outdoor unit when the working frequency Ft of the compressor included in at least one outdoor unit in the outdoor unit is equal to 0, determining the outdoor unit which stops working in the outdoor unit according to the working frequency Ft of the compressor, and determining that each outdoor unit in the outdoor unit is in the working state when the working frequency Ft of the compressor included in each outdoor unit in the outdoor unit is greater than 0.

8. The outdoor unit protection device according to claim 6, further comprising:

a third judging module, configured to, when there is an outdoor unit that stops operating in the outdoor unit, judge whether or not a discharge pressure P of a compressor included in the outdoor unit that stops operating is greater than or equal to P before an opening K of an expansion valve included in the outdoor unit that controls the outdoor unit that stops operating is greater than 0_max；

A second status confirmation module for confirming that P ≧ P_maxDetermining that the outdoor unit which stops working in the outdoor unit set is in an abnormal state; at P < P_maxDetermining that the outdoor unit which stops working in the outdoor unit set is in a safe state;

the valve control module is specifically used for controlling the valve to be more than or equal to P_maxWhen the operation is stopped, the opening K of an expansion valve included in the outdoor unit is controlled to be larger than 0.

9. The outdoor unit protection device according to claim 6,

the valve control module is specifically used for controlling the opening K of an expansion valve contained in the outdoor unit which stops working;

the outdoor unit protection device further comprises a fourth judgment module for judging whether the discharge pressure P of the compressor included in the outdoor unit which stops working is equal to P_max-k，k＞0；

The valve control module is also used for controlling the valve when P is equal to P_maxWhen K is higher than K, the opening K of the expansion valve included in the outdoor unit stopped is controlled to be 0; in the case of P > P_maxK, the opening degree K of the expansion valve included in the outdoor unit stopped is controlled to be changed.

10. The outdoor unit protection device according to claim 6, wherein k is 0.3 to 0.8.

11. A computer storage medium storing one or more computer instructions, the computer software instructions comprising a computer program designed to perform the outdoor unit protection method according to any one of claims 1 to 5.

12. An air conditioning system comprising the outdoor unit protection device according to any one of claims 6 to 10.