A control method of an evi heat pump

Abstract

The application discloses a control method of an EVI heat pump, which is used for controlling the opening degree change of an EVI electronic expansion valve used for controlling the injection enthalpy of a compressor; different control modes are adopted within N minutes after the start of the compressor and after N minutes; different parameters and different modes are adopted in a heating mode and a cooling mode, the opening degree adjustment of the EVI electronic expansion valve is controlled, and the opening degree change of the EVI electronic expansion valve is controlled. In this way, the injection enthalpy entering the compressor can be ensured to be sufficient, the heating or cooling capacity can be greatly improved, the exhaust temperature can be controlled in a reasonable range to ensure the stable and efficient operation of the unit, and the speed of the heat pump system entering the stable operation is shortened.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of heat pump air conditioners, and in particular to a control method for an EVI heat pump. BACKGROUND

[0002] With the implementation of the national coal-to-electricity policy, air energy low-temperature variable frequency heat pump units are being promoted for use. The commonly used air energy low-temperature variable frequency heat pump units are equipped with EVI compressors, economizers, EVI electronic expansion valves and throttles and other components to ensure the heating demand in winter in severe cold regions. The use of air source heat pumps with EVI technology has many advantages such as improving heating / cooling capacity, energy efficiency and expanding the operating temperature range of the heat pump, for example, through EVI technology, the heating effect can be increased at extremely low temperatures (-30℃), and the cooling effect can be increased at extremely high temperatures (56℃).

[0003] The core of EVI technology is that one more throttling process into the compressor injection port is added than the ordinary cycle, which provides secondary compression for the compressor, increases the compressor discharge capacity, and achieves the purpose of improving the heating capacity in low temperature environment and improving the cooling capacity in high temperature environment. Therefore, the core of EVI technology is the flow control of the EVI electronic expansion valve. At present, many manufacturers still use the table lookup method for the flow control of the EVI electronic expansion valve, which gives a fixed opening of the EVI electronic expansion valve according to the ambient temperature and the return water temperature. This segmented table method not only increases the workload of the development and testing process, but also is not flexible enough to fully realize the effect of EVI technology. In addition, some manufacturers do not have a control method for the EVI electronic expansion valve in cooling mode, and the cooling mode cannot realize EVI technology.

[0004] The prior art with publication number CN112393463A discloses a self-adaptive adjustment method for temperature probe faults of an air source heat pump system, and the specific control method includes the following steps: S1: judging whether the coil temperature sensor or the return air temperature sensor is faulty, the result is yes, turning to S2, and the result is no, turning to S3; S2: judging the exhaust gas superheat B = exhaust gas temperature - water outlet temperature T - subcooling compensation value K, the electronic expansion valve opening change amount P = coefficient KP * (average exhaust gas superheat in the past 30s - target exhaust gas superheat A), turning to S1; S3: return air superheat C = return air temperature - coil temperature, electronic expansion valve opening change amount P = coefficient KP * (average return air superheat SH in the past 30s - target return air superheat TSH).

[0005] In the prior art, the opening change of the electronic expansion valve is determined according to the exhaust gas superheat difference value in unit time, the operating temperature range of the heat pump is limited, and the time from the start of the unit to the stable operation is longer.

[0006] Therefore, there is a need for an advanced EVI electronic expansion valve control method, and the application provides an EVI heat pump control method to overcome the above-mentioned defects. SUMMARY

[0007] To solve the problems in the prior art, the application aims to provide an EVI heat pump control method that can ensure sufficient injection enthalpy into the compressor, greatly improve the heating or cooling capacity, control the exhaust temperature within a reasonable range to ensure stable and efficient operation of the unit, and shorten the time for the heat pump system to enter stable operation.

[0008] To achieve the above-mentioned purposes, the application adopts the following technical solutions: an EVI heat pump control method for controlling the opening degree change of an EVI electronic expansion valve, which is used to control the injection enthalpy of a compressor.

[0009] Different control methods are used within N minutes of compressor startup and after N minutes of compressor startup.

[0010] In heating mode: whether the opening degree of the EVI electronic expansion valve needs to be adjusted is determined according to the heating target exhaust superheat H_target, the current exhaust temperature Tpq, and the outlet water temperature Tcs.

[0011] Within N minutes of compressor startup, if the opening degree of the EVI electronic expansion valve needs to be adjusted, the opening degree of the EVI electronic expansion valve is periodically adjusted according to the heating target exhaust superheat H_target, the current exhaust temperature Tpq, the outlet water temperature Tcs, the exhaust temperature change amount ΔTd, and the electronic expansion valve exhaust proportional coefficient Kp.

[0012] After N minutes of compressor startup, if the opening degree of the EVI electronic expansion valve needs to be adjusted, the opening degree of the EVI electronic expansion valve is periodically adjusted according to the heating target exhaust superheat H_target, the current exhaust temperature Tpq, the outlet water temperature Tcs, the exhaust temperature change amount ΔTd, the electronic expansion valve heating adjustment coefficient Kh, and the electronic expansion valve exhaust differential coefficient Kd.

[0013] In cooling mode: whether the opening degree of the EVI electronic expansion valve needs to be adjusted is determined according to the cooling target exhaust superheat C_target, the current exhaust temperature Tpq, and the ambient temperature Thj.

[0014] Within N minutes of compressor startup, if the opening degree of the EVI electronic expansion valve needs to be adjusted, the opening degree of the EVI electronic expansion valve is periodically adjusted according to the cooling target exhaust superheat C_target, the current exhaust temperature Tpq, the ambient temperature Thj, the exhaust temperature change amount ΔTd, and the electronic expansion valve exhaust proportional coefficient Kp.

[0015] Wherein, after the compressor is started for N minutes, if the opening of the EVI electronic expansion valve needs to be adjusted, the opening of the EVI electronic expansion valve is adjusted periodically according to the target exhaust gas superheat C_targett, the current exhaust gas temperature Tpq, the ambient temperature Thj, the exhaust gas temperature variation ΔTd, the electronic expansion valve refrigeration adjustment coefficient Kc and the electronic expansion valve exhaust gas differential coefficient Kd.

[0016] Preferably, if the opening of the EVI electronic expansion valve needs to be adjusted, the way of reducing the opening of the EVI electronic expansion valve is different from the way of increasing the opening of the EVI electronic expansion valve.

[0017] Preferably, in the heating mode, if Tpq-Tcs

[0018] Preferably, in the heating mode, within N minutes after the compressor is started, if the EVI electronic expansion valve needs to be reduced, the EVI electronic expansion valve is taken as a period of M seconds, and the variation S of the EVI electronic expansion valve is equal to (H_target-Tpq+Tcs-Kp*ΔTd) / 2; within N minutes after the compressor is started, if the EVI electronic expansion valve needs to be increased, the EVI electronic expansion valve is taken as a period of M seconds, and the variation S of the EVI electronic expansion valve is equal to Tpq-Tcs-H_target+Kp*ΔTd.

[0019] Preferably, in the heating mode, after the compressor is started for N minutes, if the EVI electronic expansion valve needs to be reduced, the EVI electronic expansion valve is taken as a period of Tth seconds, and the variation S of the EVI electronic expansion valve is equal to Kh*(H_target-Tpq+Tcs)-Kd*ΔTd; after the compressor is started for N minutes, if the EVI electronic expansion valve needs to be increased, the EVI electronic expansion valve is taken as a period of Tth seconds, and the variation S of the EVI electronic expansion valve is equal to Kh*(Tpq-Tcs-H_target)+Kd*ΔTd.

[0020] Preferably, in the refrigeration mode, if Tpq-Thj

[0021] As preferred, in the refrigeration mode, if the EVI electronic expansion valve needs to be closed, the EVI electronic expansion valve takes M seconds as a period, and the change amount S of the EVI electronic expansion valve is equal to (C_target - Tpq+ Thj - Kp * DeltaTd) / 2; if the EVI electronic expansion valve needs to be opened, the EVI electronic expansion valve takes M seconds as a period, and the change amount S of the EVI electronic expansion valve is equal to Tpq - Thj - C_target + Kp * DeltaTd within N minutes of the start of the compressor.

[0022] As preferred, in the refrigeration mode, if the EVI electronic expansion valve needs to be closed, the EVI electronic expansion valve takes Ttc seconds as a period, and the change amount S of the EVI electronic expansion valve is equal to Kh * (H_target - Tpq+ Tcs) - Kd * DeltaTd after N minutes of the start of the compressor; if the EVI electronic expansion valve needs to be opened, the EVI electronic expansion valve takes Ttc seconds as a period, and the change amount S of the EVI electronic expansion valve is equal to Kc * (Tpq - Tcs - C_target) + Kd * DeltaTd after N minutes of the start of the compressor.

[0023] The technical scheme of the present application has the following beneficial effects: different operation parameters can be set for different models by using the above technical scheme, the exhaust temperature, the ambient temperature (in the refrigeration mode), and the water outlet temperature (in the heating mode) are used to participate in the opening degree control of the EVI electronic expansion valve, which is especially suitable for the condition that the outdoor ambient temperature is lower than -25 DEG C or higher than 53 DEG C, the compression ratio of the unit is high, the operation is unstable, and the heat pump capacity is extremely low. By adjusting the opening degree of the EVI electronic expansion valve, the injection enthalpy into the compressor is sufficient, the heating or refrigeration capacity is greatly improved, and the exhaust temperature is controlled in a reasonable range to ensure stable and efficient operation of the unit; the speed of the heat pump system entering the stable operation is shortened. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described in detail below, wherein identical or similar reference numerals designate identical or similar elements throughout the whole description. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0025] In the description of the present application, it needs to be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship based on the shown orientation or positional relationship, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0026] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise stated, the meaning of "a plurality of" is two or more, unless otherwise explicitly limited.

[0027] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0028] In the present application, unless otherwise explicitly specified and limited, the "upper" or "lower" of the first feature to the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the "upper", "above" and "on" of the first feature to the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The "below", "under" and "under" of the first feature to the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature. Embodiment

[0029] A control method of an EVI heat pump, the control method is used to control the opening degree change of an EVI electronic expansion valve, the EVI electronic expansion valve is used to control the injection enthalpy of a compressor;

[0030] Different control methods are used within N minutes of starting the compressor and after N minutes of starting the compressor;

[0031] In heating mode: according to the heating target exhaust gas superheat H_target, the current exhaust gas temperature Tpq and the outlet water temperature Tcs, whether the opening degree of the EVI electronic expansion valve is adjusted is determined;

[0032] Wherein, within N minutes of compressor starting, if the opening degree of the EVI electronic expansion valve needs to be adjusted, then according to the heating target exhaust gas superheat H_target, the current exhaust gas temperature Tpq, the outlet water temperature Tcs, the exhaust gas temperature change amount ΔTd and the electronic expansion valve exhaust gas proportional coefficient Kp, the opening degree of the EVI electronic expansion valve is periodically adjusted;

[0033] Wherein, after N minutes of compressor starting, if the opening degree of the EVI electronic expansion valve needs to be adjusted, then according to the heating target exhaust gas superheat H_target, the current exhaust gas temperature Tpq, the outlet water temperature Tcs, the exhaust gas temperature change amount ΔTd, the electronic expansion valve heating adjustment coefficient Kh and the electronic expansion valve exhaust gas differential coefficient Kd, the opening degree of the EVI electronic expansion valve is periodically adjusted;

[0034] In cooling mode: according to the cooling target exhaust gas superheat C_target, the current exhaust gas temperature Tpq and the ambient temperature Thj, whether the opening degree of the EVI electronic expansion valve is adjusted is determined;

[0035] Wherein, within N minutes of compressor starting, if the opening degree of the EVI electronic expansion valve needs to be adjusted, then according to the cooling target exhaust gas superheat C_target, the current exhaust gas temperature Tpq, the ambient temperature Thj, the exhaust gas temperature change amount ΔTd and the electronic expansion valve exhaust gas proportional coefficient Kp, the opening degree of the EVI electronic expansion valve is periodically adjusted;

[0036] Wherein, after N minutes of compressor starting, if the opening degree of the EVI electronic expansion valve needs to be adjusted, then according to the cooling target exhaust gas superheat C_targett, the current exhaust gas temperature Tpq, the ambient temperature Thj, the exhaust gas temperature change amount ΔTd, the electronic expansion valve cooling adjustment coefficient Kc and the electronic expansion valve exhaust gas differential coefficient Kd, the opening degree of the EVI electronic expansion valve is periodically adjusted.

[0037] In this way, different models using the above technical solutions can set different operating parameters, and the exhaust gas temperature, the ambient temperature (when cooling) and the outlet water temperature (when heating) are used to participate in the control of the opening degree of the EVI electronic expansion valve. This is especially suitable for the condition that the outdoor ambient temperature is lower than -25℃ or higher than 53℃, the compression ratio of the unit is high, the operation is unstable, and the heat pump capacity is extremely low. By adjusting the opening degree of the EVI electronic expansion valve, the injection enthalpy into the compressor is sufficient, the heating or cooling capacity is greatly improved, and the exhaust gas temperature is controlled within a reasonable range to ensure stable and efficient operation of the unit; the speed of the heat pump system entering stable operation is shortened.

[0038] In the embodiment, the exhaust proportional coefficient Kp and the exhaust differential coefficient Kd of the sub-expansion valve are proportional and differential parameters in the PID algorithm. The proportion reflects the deviation signal of the control system. Once the deviation occurs, the control action is immediately generated to reduce the deviation. The output of the proportional controller is proportional to the input deviation, which can quickly reflect the deviation and thus reduce the deviation, but cannot eliminate the static deviation. The function of the differential can reflect the trend of the deviation signal and introduce an effective correction signal in the system before the value of the deviation signal becomes too large, thereby accelerating the action speed of the system. The differential element helps the system to reduce overshoot, overcome oscillation, accelerate the response speed of the system, reduce the adjustment time, and thus improve the dynamic performance of the system.

[0039] In the embodiment, if the opening of the EVI electronic expansion valve needs to be adjusted, the way of closing the opening of the EVI electronic expansion valve is different from the way of opening the opening of the EVI electronic expansion valve. In this way, the EVI electronic expansion valve can be further controlled in detail.

[0040] In the heating mode, if Tpq-Tcs

[0041] Further, in the heating mode, within N minutes after the start of the compressor, if the EVI electronic expansion valve needs to be closed, the EVI electronic expansion valve has a cycle of M seconds, and the change amount S of the EVI electronic expansion valve is (H_target-Tpq+Tcs-Kp *ΔTd) / 2.

[0042] Within N minutes after the start of the compressor, if the EVI electronic expansion valve needs to be opened, the EVI electronic expansion valve has a cycle of M seconds, and the change amount S of the EVI electronic expansion valve is Tpq-Tcs-H_target+Kp*ΔTd.

[0043] Further, in the heating mode, after N minutes after the start of the compressor, if the EVI electronic expansion valve needs to be closed, the EVI electronic expansion valve has a cycle of Tth seconds, and the change amount S of the EVI electronic expansion valve is Kh*(H_target-Tpq+Tcs)-Kd*ΔTd.

[0044] After N minutes after the start of the compressor, if the EVI electronic expansion valve needs to be opened, the EVI electronic expansion valve has a cycle of Tth seconds, and the change amount S of the EVI electronic expansion valve is Kh*(Tpq-Tcs-H_target)+Kd*ΔTd.

[0045] In this embodiment, in the cooling mode, if Tpq-Thj

[0046] Further, in the cooling mode, within N minutes of compressor startup, if the EVI electronic expansion valve needs to be closed, the EVI electronic expansion valve is periodically closed with M seconds as a cycle, and the change amount S of the EVI electronic expansion valve is equal to (C_target - Tpq+Thj - Kp * ΔTd) / 2.

[0047] Within N minutes of compressor startup, if the EVI electronic expansion valve needs to be opened, the EVI electronic expansion valve is periodically opened with M seconds as a cycle, and the change amount S of the EVI electronic expansion valve is equal to Tpq–Thj –C_target+Kp*ΔTd.

[0048] Further, in the cooling mode, after N minutes of compressor startup, if the EVI electronic expansion valve needs to be closed, the EVI electronic expansion valve is periodically closed with Ttc seconds as a cycle, and the change amount S of the EVI electronic expansion valve is equal to Kh* (H_target - Tpq+Tcs) - Kd * ΔTd.

[0049] After N minutes of compressor startup, if the EVI electronic expansion valve needs to be opened, the EVI electronic expansion valve is periodically opened with Ttc seconds as a cycle, and the change amount S of the EVI electronic expansion valve is equal to Kc* (Tpq–Tcs –C_target) + Kd* ΔTd.

[0050] In this embodiment, ΔTd is the change amount of the exhaust temperature, which is equal to the difference between the exhaust temperature at the current time (n) and the exhaust temperature at the previous time interval (n-1), i.e., ΔTd = Td(n) - Td(n-1). N minutes, M minutes, Tth seconds, and Ttc seconds are all set by the system itself.

[0051] A heat pump system employing the above-mentioned EVI heat pump control method, wherein a heat pump system exhaust temperature sensor is installed on the exhaust port of the heat pump compressor, the exhaust temperature sensor is electrically connected to the controller, and the exhaust temperature sensor samples the exhaust temperature in real time; a water outlet temperature sensor is installed on the heat pump plate water outlet, the water outlet temperature sensor is electrically connected to the controller, and the water outlet temperature sensor samples the water outlet temperature in real time; an environment temperature sensor is installed behind the heat pump host, the environment temperature sensor is electrically connected to the controller, and the environment temperature sensor samples the environment temperature in real time. Multiple heat pump operating parameters are stored in the heat pump controller, and the controller is installed inside the host.

[0052] After the heat pump is powered on, the controller collects the exhaust temperature Tpq, the outlet water temperature Tcs, the ambient temperature Thj, and the EVI electronic expansion valve opening change amount S in real time. The decimal of the calculation result is rounded off. Nine heat pump operation parameters can be manually adjusted. The default values are independently set by the factory according to different models (system configuration, refrigerant type, etc.). Common models can be set as: H_target=45, C_target=30, P=3, Ttc=20, Tth=10, Kc=2, Kh=1, Kp=10, Kd=15.

[0053] In the description of the present specification, the description referring to the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0054] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application, and those of ordinary skill in the art can make changes, modifications, replacements and variations to the above-described embodiments without departing from the principles and spirit of the present application within the scope of the present application.

Claims

1. A control method of an EVI heat pump, characterized by: The control method is used for controlling the opening degree change of an EVI electronic expansion valve used for controlling the injection enthalpy of a compressor; Different control modes are adopted within N minutes after the start of the compressor and after N minutes; In the heating mode, whether the opening degree of the EVI electronic expansion valve needs to be adjusted is determined according to the heating target exhaust gas superheat H_target, the current exhaust gas temperature Tpq and the outlet water temperature Tcs; Within N minutes after the start of the compressor, if the opening degree of the EVI electronic expansion valve needs to be adjusted, the opening degree of the EVI electronic expansion valve is periodically adjusted according to the heating target exhaust gas superheat H_target, the current exhaust gas temperature Tpq, the outlet water temperature Tcs, the exhaust gas temperature change ΔTd and the exhaust gas proportional coefficient Kp of the electronic expansion valve; Within N minutes after the start of the compressor, if the opening degree of the EVI electronic expansion valve needs to be adjusted, the opening degree of the EVI electronic expansion valve is periodically adjusted according to the heating target exhaust gas superheat H_target, the current exhaust gas temperature Tpq, the outlet water temperature Tcs, the exhaust gas temperature change ΔTd, the heating adjustment coefficient Kh of the electronic expansion valve and the exhaust gas differential coefficient Kd of the electronic expansion valve. In the cooling mode, whether the opening degree of the EVI electronic expansion valve needs to be adjusted is determined according to the cooling target exhaust gas superheat C_target, the current exhaust gas temperature Tpq and the ambient temperature Thj; Within N minutes after the start of the compressor, if the opening degree of the EVI electronic expansion valve needs to be adjusted, the opening degree of the EVI electronic expansion valve is periodically adjusted according to the cooling target exhaust gas superheat C_target, the current exhaust gas temperature Tpq, the ambient temperature Thj, the exhaust gas temperature change ΔTd and the exhaust gas proportional coefficient Kp of the electronic expansion valve. Within N minutes after the start of the compressor, if the opening degree of the EVI electronic expansion valve needs to be adjusted, the opening degree of the EVI electronic expansion valve is periodically adjusted according to the cooling target exhaust gas superheat C_target, the current exhaust gas temperature Tpq, the ambient temperature Thj, the exhaust gas temperature change ΔTd, the cooling adjustment coefficient Kc of the electronic expansion valve and the exhaust gas differential coefficient Kd of the electronic expansion valve.

2. The control method of an EVI heat pump according to claim 1, characterized by: The way of reducing the opening degree of the EVI electronic expansion valve is different from the way of increasing the opening degree of the EVI electronic expansion valve if the opening degree of the EVI electronic expansion valve needs to be adjusted.

3. The control method of an EVI heat pump according to claim 2, characterized by: In the heating mode, if Tpq-Tcs 4. The control method of an EVI heat pump according to claim 3, characterized by: Within N minutes after the start of the compressor, if the opening degree of the EVI electronic expansion valve needs to be reduced, the EVI electronic expansion valve is taken as a period of M seconds, and the change S of the EVI electronic expansion valve is equal to (H_target-Tpq+Tcs-Kp*ΔTd) / 2. If the EVI electronic expansion valve needs to be opened wide within N minutes of the compressor starting, the EVI electronic expansion valve is set to a period of M seconds, and the change amount S of the EVI electronic expansion valve is Tpq-Tcs-H_target+Kp*ΔTd.

5. The control method of an EVI heat pump according to claim 3, characterized by: In the heating mode, if the EVI electronic expansion valve needs to be closed after N minutes of the compressor starting, the EVI electronic expansion valve is set to a period of Tth seconds, and the change amount S of the EVI electronic expansion valve is Kh*(H_target-Tpq+Tcs)-Kd*ΔTd. If the EVI electronic expansion valve needs to be opened wide after N minutes of the compressor starting, the EVI electronic expansion valve is set to a period of Tth seconds, and the change amount S of the EVI electronic expansion valve is Kh*(Tpq-Tcs-H_target)+Kd*ΔTd.

6. The control method of an EVI heat pump according to claim 2, characterized by: In the cooling mode, if Tpq-Thj 7. The control method of an EVI heat pump according to claim 6, characterized by: In the cooling mode, if Tpq-Thj If the EVI electronic expansion valve needs to be opened wide within N minutes of the compressor starting, the EVI electronic expansion valve is set to a period of M seconds, and the change amount S of the EVI electronic expansion valve is Tpq-Thj-C_target+Kp*ΔTd.

8. The control method of an EVI heat pump according to claim 6, characterized by: In the cooling mode, if Tpq-Thj If the EVI electronic expansion valve needs to be opened wide within N minutes of the compressor starting, the EVI electronic expansion valve is set to a period of M seconds, and the change amount S of the EVI electronic expansion valve is Tpq-Thj-C_target+Kp*ΔTd. In the cooling mode, if Tpq-Thj If the EVI electronic expansion valve needs to be opened wide within N minutes of the compressor starting, the EVI electronic expansion valve is set to a period of M seconds, and the change amount S of the EVI electronic expansion valve is Tpq-Thj-C_target+Kp*ΔTd.