Triple co-generation air conditioning system and control method thereof

Abstract

The control method comprises the following steps that when the triple co-generation air conditioning system has the working conditions of high-temperature low-load heating and high-temperature water heating, the opening degree of an outdoor main electronic expansion valve (201) on the outdoor unit side (200) of the triple co-generation air conditioning system is subjected to hierarchical control; underclocking control is conducted on the lowest operation frequency of the compressor (202) and the lowest operation frequency of the outer draught fan (203); the opening degree of an indoor electronic expansion valve (101) on the indoor unit side (100) of the triple co-generation air conditioning system is subjected to hierarchical control, and the opening degree of an indoor unit valve (102) in a shutdown state is controlled, so that the bypass effect is achieved, and high pressure is reduced; and the four-way valve in the heating mode is subjected to control mode switching. Through the technical means of reducing the load of the outdoor unit, adjusting the opening degree of the valve and the like, the high pressure of the system is controlled to continuously rise, the stability and reliability of the system are improved, and then the user experience is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of trigeneration air-conditioning systems, and more specifically, relates to a trigeneration air-conditioning system and a control method thereof. Background Art

[0002] In current integrated energy systems for air conditioning and hot water supply, trigeneration air conditioning systems (air conditioning + hot water + floor heating) are gaining market favor due to their high energy efficiency, multi-purpose functionality, and flexible and practical system applications. However, in actual engineering applications, especially when the system simultaneously performs high-load tasks such as "high-temperature, low-load heating and high-temperature hot water," the load on the condensing side increases significantly, causing the high pressure to continue to rise. As a result, the unit is prone to problems such as high-pressure protection, excessive exhaust temperature, and drive overcurrent, which seriously affect the system stability and may even cause the system to automatically shut down, significantly reducing the user experience.

[0003] Specifically, the technical issues to be resolved include at least:

[0004] (1) The heat exchange temperature difference is small and it is difficult to dissipate heat on the condensing side: When the system is in the "double high temperature" heating condition, that is, the system is in low-load heating, and a small number of indoor units are turned on while meeting the high-temperature hot water working condition. When the compressor starts, the heat exchange temperature difference on the condensing side is small, and the number of indoor units turned on at this time is small, resulting in a small condensing area. Therefore, the heat exchange capacity of the system is poor, which in turn affects the rapid change of the high pressure of the outdoor unit, causing the high pressure to increase with the increase of the compressor frequency.

[0005] (2) Heating requires ensuring the reversing pressure difference, which causes the compressor to increase its frequency: When the heating mode is turned on for the first time, the compressor needs to increase its frequency to the reversing frequency to ensure that the pressure difference can meet the reversing pressure difference, which will cause the high pressure of the outdoor unit to rise rapidly.

[0006] (3) Unbalanced refrigerant distribution: When the heating mode is turned on, the refrigerant mainly flows to the indoor heat exchanger; but when the hot water mode is started, part of the refrigerant is diverted to the water heat exchanger, resulting in uneven system flow distribution and reduced heat exchange efficiency. Summary of the Invention

[0007] In order to address the deficiencies in the prior art, the present invention provides a trigeneration air-conditioning system and a control method thereof. By reducing the load of the external unit, adjusting the valve opening and other technical means, the continuous rise of the system high pressure can be controlled to a certain extent, thereby improving the stability and reliability of the system.

[0008] The present invention adopts the following technical solutions.

[0009] A first aspect of the present invention provides a control method for a trigeneration air conditioning system, comprising the following steps:

[0010] When the trigeneration air-conditioning system encounters high-temperature low-load heating and high-temperature hot water conditions, the opening of the outdoor main electronic expansion valve on the outdoor unit side of the trigeneration air-conditioning system is controlled in stages, and the minimum operating frequency of the compressor and the outdoor fan is controlled to be reduced;

[0011] Implementing graded control on the opening of the indoor electronic expansion valve on the indoor unit side of the trigeneration air conditioning system, and controlling the opening of the indoor valve of the shutdown unit to play a bypass role and reduce the high pressure;

[0012] And switch the control mode of the four-way valve in heating mode.

[0013] Preferably, for the outdoor main electronic expansion valve on the external unit side, the high pressure is divided into multiple intervals from low to high, each interval corresponds to an outdoor main electronic expansion valve opening, and the opening of the outdoor main electronic expansion valve corresponding to each interval from low to high gradually decreases; if the outdoor temperature exceeds the temperature threshold, the opening of the outdoor main electronic expansion valve is controlled according to the interval to which the high pressure belongs.

[0014] Preferably, for the outdoor main electronic expansion valve, the high pressure is divided into six intervals from low to high using five nodes Tc1, Tc2, Tc3, Tc4, and Tc5, namely high pressure Tc ≥ Tc5, Tc4 ≤ Tc < Tc5, Tc3 ≤ Tc < Tc4, Tc2 ≤ Tc < Tc3, Tc1 ≤ Tc < Tc2, and Tc < Tc1, corresponding to not performing optimization control, and the five outdoor main electronic expansion valve openings Pw1, Pw2, Pw3, Pw4, and Pw5, respectively;

[0015] If the outdoor temperature Tenv exceeds the temperature threshold T1, the opening of the outdoor main electronic expansion valve is controlled according to the interval to which the high pressure Tc belongs; if the outdoor temperature Tenv does not exceed the temperature threshold T1, the optimization control is not performed.

[0016] Preferably, for the compressor and the external fan, if the trigeneration air-conditioning system is in heating mode, the minimum operating frequencies of the compressor and the fan are reduced according to a set ratio.

[0017] Preferably, for the indoor unit electronic expansion valve on the indoor unit side, the rated capacity of the indoor unit is divided into multiple intervals from low to high, each interval corresponds to an indoor electronic expansion valve opening, and the indoor electronic expansion valve opening corresponding to each interval from low to high gradually increases, and the indoor electronic expansion valve opening when the outdoor temperature Tenv exceeds the temperature threshold T1 is greater than the indoor electronic expansion valve opening when the outdoor temperature Tenv exceeds the temperature threshold T1.

[0018] Preferably, for the indoor unit electronic expansion valve, the rated capacity Qe of the indoor unit is divided into two intervals from low to high by a node Qy, namely the rated capacity Qe of the indoor unit < Qy and Qe ≥ Qy;

[0019] If the outdoor temperature Tenv exceeds the temperature threshold T1, in the cases of Qe < Qy and Qe ≥ Qy, the opening degrees of the indoor electronic expansion valve are controlled by Pn1 and Pn2 respectively; if the outdoor temperature Tenv does not exceed the temperature threshold T1, in the cases of Qe < Qy and Qe ≥ Qy, the opening degrees of the indoor electronic expansion valve are controlled by Pn3 and Pn4 respectively, where Pn2 > Pn1 > Pn4 > Pn3.

[0020] Preferably, for the shutdown indoor unit valve, if the outdoor temperature Tenv exceeds the temperature threshold T1 and the high pressure Tc of the combined heat and power air conditioning system ≥ Tc1 °C, then the initial step number is P1 PLS when starting within T min after shutdown. After T min, the shutdown indoor unit valve is adjusted in the following manner, and the adjustment range is [Ps1, Ps2]; otherwise, the initial step number is P2 PLS when starting within T min after shutdown. After T min, the shutdown indoor unit valve is adjusted in the following manner, and the adjustment range is [Ps1, Ps3], where P1 > P2 and Ps2 > Ps3.

[0021] Preferably, for the four-way valve, the indoor unit capacity demand is divided into multiple intervals from low to high. Each interval corresponds to an indoor electronic expansion valve opening degree and a four-way valve control strategy. The indoor electronic expansion valve opening degrees corresponding to the intervals from low to high gradually increase, and after the four-way valve position action is completed, it is controlled according to the initial opening degree or normal control.

[0022] Preferably, for the four-way valve, the indoor unit capacity demand Qr is divided into two intervals from low to high by a node Qz, namely the rated capacity Qr of the indoor unit ≥ Qz and Qr < Qz;

[0023] If the outdoor temperature Tenv exceeds the temperature threshold T1, in the case of Qr ≥ Qz, the opening degree of the indoor electronic expansion valve is controlled by Pv1, and after the four-way valve position action is completed, it is controlled according to the initial opening degree. In the case of Qr < Qz, the opening degree of the indoor electronic expansion valve is controlled by Pv2, and after the four-way valve position action is completed, it is controlled according to the normal control;

[0024] If the outdoor temperature Tenv does not exceed the temperature threshold T1, in the case of Qr ≥ Qz, the opening degree of the indoor electronic expansion valve is controlled by Pv3, and after the four-way valve position action is completed, it is controlled according to the initial opening degree. In the case of Qr < Qz, the opening degree of the indoor electronic expansion valve is controlled by Pv4, and after the four-way valve position action is completed, it is controlled according to the normal control.

[0025] The second aspect of the present invention provides a trigeneration air-conditioning system, comprising: an indoor unit side, an outdoor unit side and a controller, characterized in that the controller executes a control method for a trigeneration air-conditioning system according to the first aspect, implements hierarchical control of the opening of the outdoor main electronic expansion valve on the outdoor unit side, and performs frequency reduction control on the minimum operating frequency of the compressor and the outdoor fan; implements hierarchical control of the opening of the indoor electronic expansion valve on the indoor unit side, controls the opening of the indoor unit valve in the shutdown state, and switches the control mode of the four-way valve in the heating mode.

[0026] Compared with the existing technology, the beneficial effects of the present invention include at least: to address the problems of difficulty in heat dissipation on the condensing side, to ensure the frequency increase of the heating reversing compressor and the imbalance of refrigerant distribution, the present invention optimizes the control method by combining heat exchange and increasing the circulation in the pipeline, thereby improving and enhancing the stability and reliability of the system, and thus improving and enhancing the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of a high-pressure control method for a trigeneration air-conditioning system in a high-load working state according to an embodiment of the present invention;

[0028] Figure 2 The present invention provides a structural block diagram of a trigeneration air conditioning system. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0030] like Figure 1 As shown, embodiment 1 of the present invention provides a control method for a trigeneration air conditioning system, specifically a high-voltage control method for high-load working conditions. It is worth noting that the control method provided by the present invention can be applied to existing trigeneration air conditioning systems. Unless otherwise specified, the components targeted in the control method are all components of the trigeneration air conditioning system that are composed of existing connection relationships, such as Figure 2 As shown, the interior unit side 100 of the trigeneration air conditioning system is connected to the exterior unit side 200 through a pipeline via a high-pressure gas pipe valve and a liquid pipe valve.

[0031] The indoor unit side 100 includes multiple indoor units, divided into active and inactive units according to their operating status. Each of these units is connected to an indoor electronic expansion valve on its branch line. For a clearer presentation of the technical solution, by way of example and not limitation, active indoor units are connected to indoor electronic expansion valve 101, while inactive indoor units are connected to inactive indoor valve 102. The outdoor unit side includes a fan, a compressor, a four-way valve connected between the compressor outlet and the heat exchanger, and an outdoor main electronic expansion valve 201 located in the high-pressure liquid pipe. The remaining components of the trigeneration air conditioning system, such as but not limited to the gas-liquid separator, oil separator, oil return solenoid valve, and oil return capillary tube, can adopt the same connection method as existing trigeneration air conditioning systems.

[0032] As one of the outstanding substantive features of the present invention, the present invention optimizes the coupled control of system heat exchange and circulation within the pipeline, adjusts according to the system high pressure and load, and realizes hierarchical control of the operating frequency of the outdoor unit compressor 202 and the fan 203, as well as the opening of each valve in the system, so as to solve the problems of high pressure protection, excessive exhaust temperature, and drive overcurrent that occur in the existing trigeneration unit system when performing the "high temperature, low load heating and high temperature hot water" task, thereby improving the stability and reliability of the trigeneration air conditioning system. Specifically, the control method includes the following steps:

[0033] When the trigeneration air-conditioning system encounters high-temperature, low-load heating and high-temperature hot water conditions, the outdoor main electronic expansion valve opening of the external unit side 200 is controlled in stages, and the minimum operating frequency of the compressor 202 and the outdoor fan 203 is controlled to be reduced. Preferably, but not restrictively, the optimization control of the external unit side 200 specifically includes:

[0034] For the outdoor main electronic expansion valve 201, the high pressure is divided into multiple intervals from low to high, each interval corresponds to an opening of the outdoor main electronic expansion valve 201, and the unit is PLS (Pulses). The opening of the outdoor main electronic expansion valve 201 corresponding to each interval from low to high gradually decreases, and the opening of the outdoor main electronic expansion valve 201 corresponding to the last interval is adjusted and controlled according to normal logic, that is, no optimization control is performed.

[0035] If the outdoor temperature exceeds the temperature threshold, the opening of the outdoor main electronic expansion valve 201 is controlled according to the high pressure range. If the outdoor temperature does not reach the temperature threshold, the opening of the outdoor main electronic expansion valve 201 is adjusted and controlled according to normal logic.

[0036] Preferably but not restrictively, the high pressure is divided into six intervals from low to high by five nodes Tc1, Tc2, Tc3, Tc4, and Tc5, that is, high pressure Tc≥Tc5, Tc4≤Tc<Tc5, Tc3≤Tc<Tc4, Tc2≤Tc<Tc3, Tc1≤Tc<Tc2, Tc<Tc1, which correspond to the normal logic adjustment control and the opening degrees of the five outdoor main electronic expansion valves 201 Pw1, Pw2, Pw3, Pw4 and Pw5 respectively.

[0037] If the outdoor temperature Tenv exceeds the temperature threshold T1, the opening of the outdoor main electronic expansion valve 201 is controlled according to the interval of the high pressure Tc; if the outdoor temperature Tenv does not exceed the temperature threshold T1, the opening of the outdoor main electronic expansion valve 201 is adjusted and controlled according to normal logic.

[0038] With respect to compressor 202 and external fan 203, when the system is in heating mode, the minimum operating frequencies of compressor 202 and external fan 203 are adjusted from F1 to F2, and from F3 to F4. The minimum operating frequency of compressor 202, F1, is higher than the minimum operating frequency of compressor 202, F2; and the minimum operating frequency of external fan 203, F3, is higher than the minimum operating frequency of external fan 203, F4. Preferably, but not limited to, the minimum operating frequencies of compressor 202 and external fan 203 are reduced according to a set ratio.

[0039] When the trigeneration air conditioning system encounters high-temperature, low-load heating and high-temperature hot water conditions, the opening of the indoor electronic expansion valve 101 on the indoor unit side 100 is controlled in stages, and the indoor unit valve 102 in the off state and the four-way valve in the heating mode are optimized. Preferably, but not limited to, the optimized control of the indoor unit side 100 specifically includes:

[0040] For the indoor unit electronic expansion valve, the rated capacity of the indoor unit is divided into multiple intervals from low to high. Each interval corresponds to an opening degree of the indoor electronic expansion valve 101, and the unit is PLS. The opening degree of the indoor electronic expansion valve 101 corresponding to each interval from low to high gradually increases. When the outdoor temperature exceeds the temperature threshold, the opening degree of the indoor electronic expansion valve 101 is greater than the opening degree of the indoor electronic expansion valve 101 when the outdoor temperature does not exceed the temperature threshold.

[0041] Preferably but not limited thereto, a node Qy divides the rated capacity Qe of the indoor unit into two intervals from low to high, that is, the rated capacity Qe of the indoor unit is Qe < Qy and Qe ≥ Qy. If the outdoor temperature Tenv exceeds the temperature threshold T1, in the cases of Qe < Qy and Qe ≥ Qy, the opening degree of the indoor electronic expansion valve 101 is controlled by Pn1 and Pn2 respectively; if the outdoor temperature Tenv does not exceed the temperature threshold T1, in the cases of Qe < Qy and Qe ≥ Qy, the opening degree of the indoor electronic expansion valve 101 is controlled by Pn3 and Pn4 respectively, where Pn2 > Pn1 > Pn4 > Pn3.

[0042] For the shutdown indoor unit valve 102, the control of the shutdown indoor unit during system operation includes:

[0043] If the outdoor temperature Tenv exceeds the temperature threshold T1 and the highest high pressure Tc in the operation module is ≥ Tc1 °C, then within Tmin of shutdown, the initial step number is P1 PLS. After T min, the shutdown indoor unit valve 102 is adjusted in the following manner, and the adjustment range is [Ps1, Ps2]; otherwise, within T min of shutdown, the initial step number is P2 PLS. After T min, the shutdown indoor unit valve 102 is adjusted in the following manner, and the adjustment range is [Ps1, Ps3], where P1 > P2 and Ps2 > Ps3.

[0044] That is to say, when the outdoor ambient temperature Tenv > T1 °C and the high pressure Tc ≥ Tc1 °C, that is, when the outdoor temperature is high and the high pressure is high, it is necessary to synchronously increase the valve opening degree of the shutdown indoor unit. At this time, the initial step number of the shutdown indoor unit is P1, and the adjustment range should also be increased at this time to reduce or buffer the phenomenon of high pressure. When the outdoor ambient temperature and high pressure are in other interval ranges, the adjustment can be made according to P2 and the interval [Ps1, Ps{3]].

[0045] The control of the startup indoor unit valve 102 is as described in the optimization part of the indoor unit electronic expansion valve control. When the outdoor temperature is high or the system high pressure is high, it is necessary to increase the opening degree of the indoor unit valve102 to play a bypass role to reduce the high pressure.

[0046] For the four-way valve control, when the system operation state is in the "heating and hot water heating" mode, the control is as follows:

[0047] The indoor unit capacity demand is divided into multiple intervals from low to high. Each interval corresponds to an opening degree of the indoor electronic expansion valve 101 and a four-way valve control strategy. The opening degrees of the indoor electronic expansion valve 101 corresponding to the intervals from low to high gradually increase. After the four-way valve position action is completed, it is controlled according to the initial opening degree or normal control.

[0048] Preferably but not limited thereto, a node Qz divides the indoor unit capacity demand Qr into two intervals from low to high, namely, the rated capacity of the indoor unit Qr≥Qz, Qr<Qz. If the outdoor temperature Tenv exceeds the temperature threshold T1, when Qr≥Qz, the opening of the indoor electronic expansion valve 101 is controlled by Pv1, and after the position of the four-way valve is actuated, it is controlled according to the initial opening; when Qr<Qz, the opening of the indoor electronic expansion valve 101 is controlled by Pv2, and after the position of the four-way valve is actuated, it is controlled normally;

[0049] If the outdoor temperature Tenv does not exceed the temperature threshold T1, when Qr≥Qz, the opening of the indoor electronic expansion valve 101 is controlled by Pv3, and after the position of the four-way valve is actuated, it is controlled according to the initial opening; when Qr<Qz, the opening of the indoor electronic expansion valve 101 is controlled by Pv4, and after the position of the four-way valve is actuated, it is controlled normally.

[0050] As Figure 2 shown, Embodiment 2 of the present invention provides a combined heat, cooling and power air-conditioning system, including: an indoor unit side 100, an outdoor unit side 200 and a controller. The controller executes a high-load working state high-pressure control method for a combined heat, cooling and power air-conditioning system according to Embodiment 1, implements hierarchical control over the opening of the outdoor main electronic expansion valve 201 on the outdoor unit side 200, and performs frequency reduction control on the minimum operating frequencies of the compressor 202 and the outdoor fan 203; implements hierarchical control over the opening of the indoor electronic expansion valve 101 on the indoor unit side 100, controls the opening of the indoor unit valve 102 in the shutdown state, and switches the control mode of the four-way valve in the heating mode.

[0051] In order to more clearly introduce the outstanding substantial features of the present invention and the significant progress brought to the prior art, the following introduces an application example of implementing the present invention.

[0052] When the combined heat, cooling and power air-conditioning system is in the high-temperature low-load heating and high-temperature hot water supply working conditions, the controller of the combined heat, cooling and power air-conditioning system implements hierarchical control over the opening of the outdoor main electronic expansion valve 201 on the outdoor unit side 200, and performs frequency reduction control on the minimum operating frequencies of the compressor 202 and the outdoor fan 203, where:

[0053] The control optimization for the outdoor main electronic expansion valve 201 is as shown in the following table:

[0054]

[0055] The optimization control for the minimum operating frequencies of the compressor 202 and the outdoor fan 203 is as follows:

[0056] When the system is in the heating mode, adjust the minimum operating frequencies of the compressor 202 and the fan:

[0057] Adjust the minimum operating frequency of compressor 202 from F1 = 25 Hz to F2 = 20 Hz;

[0058] Adjust the minimum operating frequency of the external fan 203 from F3 = 40 Hz to F4 = 30 Hz.

[0059] When the trigeneration air-conditioning system has high temperature low load heating and high temperature hot water conditions, the opening of the indoor electronic expansion valve 101 of the indoor unit side 100 is controlled in stages, and the indoor unit valve 102 in the shutdown state and the four-way valve in the heating mode are optimized.

[0060] The optimization of indoor unit electronic expansion valve control is shown in the following table:

[0061]

[0062] The control optimization of the shut-down valve 102 includes the control of shutting down the internal unit during system operation, as follows:

[0063] When the outdoor ambient temperature Tenv>T1℃ and the highest high voltage Tc in the operating module ≥Tc1℃, the initial number of steps to be turned on within Tmin of shutdown is P1 PLS. After Tmin, it is adjusted according to the following method, and the adjustment range is [Ps1, Ps2]. Otherwise, the initial number of steps to be turned on within Tmin of shutdown is P2 PLS. After Tmin, it is adjusted according to the following method, and the adjustment range is [Ps1, Ps3].

[0064] For the optimization of the four-way valve control in heating mode, when the system is in the "heating and hot water" mode, the optimized control is shown in the following table:

[0065]

[0066] Embodiment 3 of the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is loaded into the processor, the high-voltage control method for the high-load working state of the trigeneration air-conditioning system according to embodiment 1 is implemented.

[0067] Embodiment 4 of the present invention provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the high-pressure control method for a trigeneration air-conditioning system in a high-load working state according to embodiment 1 is implemented.

[0068] 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 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 by the scope of protection of the claims of the present invention.

Claims

1. A control method for a trigeneration air conditioning system, characterized in that: The following steps are involved: When the trigeneration air-conditioning system is in high-temperature low-load heating and high-temperature hot water conditions, the opening of the outdoor main electronic expansion valve (201) on the outdoor unit side (200) of the trigeneration air-conditioning system is controlled in stages, and the minimum operating frequency of the compressor (202) and the outdoor fan (203) is controlled by frequency reduction; The opening of the indoor electronic expansion valve (101) on the indoor unit side (100) of the trigeneration air conditioning system is controlled in stages, and the opening of the indoor unit valve (102) in the shutdown state is controlled to play a bypass role and reduce the high pressure; And switch the control mode of the four-way valve in heating mode.

2. The control method of a trigeneration air conditioning system according to claim 1, characterized in that: For the outdoor main electronic expansion valve (201) on the external unit side (200), the high pressure is divided into a plurality of intervals from low to high, each interval corresponds to an opening of the outdoor main electronic expansion valve (201), and the opening of the outdoor main electronic expansion valve (201) corresponding to each interval from low to high gradually decreases; if the outdoor temperature exceeds a temperature threshold, the opening of the outdoor main electronic expansion valve (201) is controlled according to the interval to which the high pressure belongs.

3. The control method of a trigeneration air conditioning system according to claim 1 or 2, characterized in that: For the outdoor main electronic expansion valve (201), the high pressure is divided into six intervals from low to high using five nodes Tc1, Tc2, Tc3, Tc4, and Tc5, namely high pressure Tc≥Tc5, Tc4≤Tc<Tc5, Tc3≤Tc<Tc4, Tc2≤Tc<Tc3, Tc1≤Tc<Tc2, and Tc<Tc1, corresponding to not performing optimization control and the opening degrees of the five outdoor main electronic expansion valves (201), Pw1, Pw2, Pw3, Pw4, and Pw5, respectively; If the outdoor temperature Tenv exceeds the temperature threshold T1, the opening of the outdoor main electronic expansion valve (201) is controlled according to the interval to which the high pressure Tc belongs; if the outdoor temperature Tenv does not exceed the temperature threshold T1, the optimization control is not performed.

4. The control method of a trigeneration air conditioning system according to claim 1, characterized in that: For the compressor (202) and the external fan (203), if the trigeneration air-conditioning system is in a heating mode, the minimum operating frequencies of the compressor (202) and the fan are reduced according to a set ratio.

5. The control method of a trigeneration air conditioning system according to claim 1, characterized in that: For the indoor electronic expansion valve on the indoor unit side (100), the rated capacity of the indoor unit is divided into a plurality of intervals from low to high, each interval corresponds to an opening of the indoor electronic expansion valve (101), the opening of the indoor electronic expansion valve (101) corresponding to each interval from low to high gradually increases, and the opening of the indoor electronic expansion valve (101) when the outdoor temperature Tenv exceeds a temperature threshold T1 is greater than the opening of the indoor electronic expansion valve (101) when the outdoor temperature Tenv exceeds the temperature threshold T1.

6. The control method of a combined cooling, heating and power air conditioning system according to claim 1 or 5, characterized in that: For the indoor electronic expansion valve, a node Qy divides the rated capacity Qe of the indoor unit into two intervals from low to high, namely the rated capacity Qe of the indoor unit < Qy and Qe ≥ Qy; If the outdoor temperature Tenv exceeds the temperature threshold T1, in the cases of Qe < Qy and Qe ≥ Qy, the opening degrees of the indoor electronic expansion valve (101) are controlled by Pn1 and Pn2 respectively; if the outdoor temperature Tenv does not exceed the temperature threshold T1, in the cases of Qe < Qy and Qe ≥ Qy, the opening degrees of the indoor electronic expansion valve (101) are controlled by Pn3 and Pn4 respectively, where Pn2 > Pn1 > Pn4 > Pn3.

7. The control method of a combined cooling, heating and power air conditioning system according to claim 1 or 2, characterized in that: For the shutdown indoor unit valve (102), if the outdoor temperature Tenv exceeds the temperature threshold T1 and the high pressure Tc of the combined cooling, heating and power air conditioning system ≥ Tc1 °C, then the initial step number is P1 PLS at the start within T min, and after T min, the shutdown indoor unit valve (102) is adjusted in the following manner, and the adjustment range is [Ps1, Ps2]; otherwise, the initial step number is P2 PLS at the start within T min, and after T min, the shutdown indoor unit valve (102) is adjusted in the following manner, and the adjustment range is [Ps1, Ps3], where P1 > P2 and Ps2 > Ps3.

8. The control method of a combined cooling, heating and power air conditioning system according to claim 1, characterized in that: For the four-way valve, the indoor unit capacity demand is divided into multiple intervals from low to high, and each interval corresponds to an opening degree of the indoor electronic expansion valve (101) and a four-way valve control strategy. The opening degrees of the indoor electronic expansion valve (101) corresponding to the intervals from low to high gradually increase, and after the four-way valve position action is completed, it is controlled according to the initial opening degree or normal control.

9. The control method of a combined cooling, heating and power air conditioning system according to claim 1 or 8, characterized in that: For the four-way valve, a node Qz divides the indoor unit capacity demand Qr into two intervals from low to high, namely the rated capacity Qr of the indoor unit ≥ Qz and Qr < Qz; If the outdoor temperature Tenv exceeds the temperature threshold T1, in the case of Qr ≥ Qz, the opening degree of the indoor electronic expansion valve (101) is controlled by Pv1, and after the four-way valve position action is completed, it is controlled according to the initial opening degree. In the case of Qr < Qz, the opening degree of the indoor electronic expansion valve (101) is controlled by Pv2, and after the four-way valve position action is completed, it is controlled according to the normal control; If the outdoor temperature Tenv does not exceed the temperature threshold T1, in the case of Qr ≥ Qz, the opening degree of the indoor electronic expansion valve (101) is controlled by Pv3, and after the four-way valve position action is completed, it is controlled according to the initial opening degree. In the case of Qr < Qz, the opening degree of the indoor electronic expansion valve (101) is controlled by Pv4, and after the four-way valve position action is completed, it is controlled according to the normal control.

10. A trigeneration air conditioning system, comprising: An indoor unit side (100), an outdoor unit side (200) and a controller, characterized in that the controller executes a control method for a trigeneration air-conditioning system according to any one of claims 1 to 9, implements hierarchical control on the opening of the outdoor main electronic expansion valve (201) of the outdoor unit side (200), and performs frequency reduction control on the minimum operating frequency of the compressor (202) and the outdoor fan (203); implements hierarchical control on the opening of the indoor electronic expansion valve (101) of the indoor unit side (100), controls the opening of the indoor unit valve (102) in the shutdown state, and switches the control mode of the four-way valve in the heating mode.

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