A power battery thermal management control system and method thereof

Abstract

The present invention relates to the technical field of electric vehicle heat management, and provides a power battery heat management control system and method, the system comprising: a heat exchanger, a heater, an electronic water pump M1 and a power battery pack connected in sequence through pipelines, the output pipeline of the power battery pack is connected to the input pipeline of the heat exchanger or the engine through a three-way valve Y2, the output pipeline of the engine is connected to the input pipeline of the cooling fan or the three-way valve Y1 through a three-way valve Y3, the output pipeline of the cooling fan is connected to the input pipeline of the three-way valve Y1, the output pipeline of the three-way valve Y1 is connected to the input pipeline of the electronic water pump M1 or the electronic water pump M2, and the output pipeline of the electronic water pump M2 is connected to the input pipeline of the engine. The power battery heat management system comprises an internal cycle and an external cycle, and the internal cycle or the external cycle can be selected to heat or cool the power battery pack to different degrees, and the temperature of the power battery pack can be more accurately regulated.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal management of electric vehicles, and provides a power battery thermal management control system and method thereof. Background Art

[0002] The charging and discharging power of the power battery in electric vehicles is affected by many external environmental factors, among which temperature has a greater impact on the power battery of electric vehicles. How to reasonably control the temperature of the power battery pack during charging and discharging is one of the problems that the new energy vehicle industry urgently needs to solve. Summary of the invention

[0003] The present invention provides a power battery thermal management control system, which includes an internal cycle and an external cycle. The internal cycle or the external cycle can be selected to heat or cool the power battery pack to different degrees, and the temperature of the power battery pack can be more accurately regulated.

[0004] The present invention is implemented as follows: a power battery thermal management control system, the system comprising:

[0005] The heat exchanger Chiller, the heater PTC, the electronic water pump M1 and the power battery pack are connected in sequence through pipelines. The output pipeline of the power battery pack is connected to the input pipeline of the heat exchanger Chiller or the engine Motor through the three-way valve Y2. The output pipeline of the engine Motor is connected to the input pipeline of the cooling fan or the three-way valve Y1 through the three-way valve Y3. The output pipeline of the cooling fan is connected to the input pipeline of the three-way valve Y1. The output pipeline of the three-way valve Y1 is connected to the input pipeline of the electronic water pump M1 or the electronic water pump M2. The output pipeline of the electronic water pump M2 is connected to the input pipeline of the engine Motor. The refrigerant in the heat exchanger Chiller is returned to the heat exchanger Chiller through the compressor and the condenser in sequence.

[0006] The compressor, the heater PTC, the electronic water pump M1, the electronic water pump M2, the cooling fan, the heat exchanger Chiller, the three-way valve Y1, the three-way valve Y2 and the three-way valve Y3 are all connected to the VCU controller.

[0007] Furthermore, the system also includes: an expansion pot, and another output pipeline of the cooling fan is connected to the input pipeline of the three-way valve Y1 through the expansion pot.

[0008] Furthermore, the system also includes:

[0009] DC / DC is installed between the output pipeline of the electronic water pump M2 and the input pipeline of the engine.

[0010] The present invention is implemented in a power battery thermal management control method, which heats and cools a power battery pack during the charging and discharging process based on the power battery thermal management control system, wherein the charging process includes a fast charging mode and a slow charging mode.

[0011] Furthermore, the heating control method in the slow charging mode is as follows:

[0012] When the minimum temperature T1 of the power battery is lower than 5°C, the VCU controller starts the electronic water pump M1 and the heater PTC in sequence, controls the three-way valve Y2 and the three-way valve Y1 to be in the normal position, and regularly detects the minimum temperature T1 of the power battery. When T1>5°C, the power battery is slowly charged. When T1 reaches 10°C, the electronic water pump M1 and the heater PTC are turned off in sequence.

[0013] Furthermore, the heating control method in the fast charging mode is as follows:

[0014] When the minimum temperature T1 of the power battery is lower than 15°C, the VCU controller starts the electronic water pump M1 and the heater PTC in sequence, and controls the three-way valve Y2 and the three-way valve Y1 to be in the normal position. The battery management system BMS of the power battery regularly detects the minimum temperature T1 of the power battery. When T1>5°C, the power battery is slowly charged. When T1 reaches 15°C, the electronic water pump M1 and the heater PTC are turned off in sequence.

[0015] Furthermore, the heating control method during the discharge process is as follows:

[0016] If the lowest temperature T1 of the power battery is lower than 0°C, the VCU controller starts the electronic water pump M1 and the heater PTC in sequence, controls the three-way valve Y2 and the three-way valve Y1 to be in the normal position, and starts the electronic water pump M2 at the same time, controls the three-way valve Y3 to be in the variable position, and the battery management system BMS of the power battery pack regularly detects the difference between the lowest temperature T1 of the power battery and the outlet water temperature T3 of the external circulation, as well as the outlet water temperature T3 of the external circulation;

[0017] 1) If T3-T1<15℃ and T3<30℃, the power battery pack is heated by the heater PTC. When the battery pack water inlet temperature T2>45℃, the heater PTC relay is disconnected;

[0018] 2) If T3-T1≥15℃ and T3<30℃, the VCU controller controls the PTC relay to be in the disconnected state, turns off the electronic water pump M2, and the three-way valve Y1 and the three-way valve Y2 are in the shifted position, and the power battery pack is heated by the excess heat of the engine;

[0019] 3) If T3 - T1 < 15°C and T3 ≥ 30°C, heat the power battery pack through the PTC heater, control the three-way valve Y3 to be in the normal position, and start the cooling fan. When the inlet temperature T2 of the battery pack > 45°C, disconnect the PTC heater relay;

[0020] 4) If T3 - T1 ≥ 15°C and T3 ≥ 30°C, the VCU controller controls the PTC relay to be in the off state, closes the electronic water pump M2, controls the three-way valves Y1 and Y2 to be in the displaced position, the three-way valve Y3 to be in the normal position, starts the cooling fan, and heats the power battery pack with the excess heat of the engine, while dissipating heat through the cooling fan.

[0021] Furthermore, the slow charge mode and the cooling method in the slow charge mode are as follows:

[0022] When 35°C ≤ T1 ≤ 42°C, monitor the outlet temperature T3 of the external circulation;

[0023] 5) If T3 ≤ 25°C, start the electronic water pump M1, control the three-way valves Y1, Y2, and Y3 to be in the displaced position, and cool down the power battery pack with the low-temperature coolant in the external circulation;

[0024] 6) If 25°C < T3 ≤ 30°C, start the electronic water pump M1, control the three-way valves Y1 and Y2 to be in the displaced position, the three-way valve Y3 to be in the normal position, and start the cooling fan. Cool down the power battery pack with the low-temperature coolant in the external circulation, and the cooling fan dissipates heat from the coolant in the external circulation;

[0025] 7) If T3 ≥ 25°C, start the electronic water pump M1 and the compressor, and control the three-way valves Y2 and Y1 to be in the normal position.

[0026] 8) When T1 < 35°C, if the difference between the highest temperature and the lowest temperature of the power battery pack is greater than 8°C, start the electronic water pump M1 and the compressor, control the three-way valves Y2 and Y1 to be in the normal position, until the difference between the highest temperature and the lowest temperature of the power battery pack is less than 6°C, then turn off the electronic water pump M1 and the compressor;

[0027] 9) When T1 ≥ 42°C, start the electronic water pump M1 and the compressor, control the three-way valves Y2 and Y1 to be in the normal position, and control the heat exchanger chiller to be in the high gear.

[0028] Furthermore, the cooling method during the discharging process is as follows:

[0029] If the maximum temperature T4 of the power battery pack is 35℃≤T4≤42℃, start the electronic water pump M1 and the compressor, and control the three-way valve Y2 and the three-way valve Y1 to be in the normal position; if 42℃≤T4≤45℃, start the electronic water pump M1 and the compressor, control the three-way valve Y2 and the three-way valve Y1 to be in the normal position, control the heat exchanger Chiller to be in the middle position, and the default gear of the heat exchanger is the low gear; when T4≥45℃, start the electronic water pump M1 and the compressor, control the three-way valve Y2 and the three-way valve Y1 to be in the normal position, and control the heat exchanger Chiller to be in the high position.

[0030] The power battery thermal management system provided by the present invention includes an internal cycle and an external cycle. The internal cycle or the external cycle can be selected to heat or cool the power battery pack to different degrees, and the temperature of the power battery pack can be more accurately regulated. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of the structure of a power battery thermal management control system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The specific implementation of the present invention will be further explained in detail below by describing the optimal embodiment with reference to the accompanying drawings.

[0033] Figure 1 This is a schematic diagram of the structure of a power battery thermal management control system provided in an embodiment of the present invention. For the sake of convenience, only the parts related to the embodiment of the present invention are shown.

[0034] The system includes:

[0035] The heat exchanger Chiller, the heater PTC, the electronic water pump M1 and the power battery pack are connected in sequence through pipelines. The output pipeline of the power battery pack is connected to the input pipeline of the heat exchanger Chiller or the DC / DC through the three-way valve Y2. The output pipeline of the DC / DC is connected to the input pipeline of the engine. The output pipeline of the engine is connected to the input pipeline of the cooling fan or the three-way valve Y1 through the three-way valve Y3. One output pipeline of the cooling fan is directly connected to the input pipeline of the three-way valve Y1. The other output pipeline of the cooling fan is connected to the input pipeline of the three-way valve Y1 through the expansion pot; the output pipeline of the three-way valve Y1 is connected to the input pipeline of the electronic water pump M1 or the electronic water pump M2, and the output pipeline of the electronic water pump M2 is connected to the input pipeline of the DC / DC;

[0036] The refrigerant in the heat exchanger Chiller returns to the heat exchanger Chiller via the compressor and the condenser in sequence.

[0037] In the present embodiment, the compressor, the heater PTC, the electronic water pump M1, the electronic water pump M2, the cooling fan, the heat exchanger Chiller, the three-way valve Y1, the three-way valve Y2 and the three-way valve Y3 are all connected to the VCU controller.

[0038] In an embodiment of the present invention, the heat exchanger Chiller, the heater PTC, the electronic water pump M1, the power battery pack, the three-way valve Y2 in the normal position and the three-way valve Y1 constitute an internal circulation, and the internal circulation is heated by the heater PTC to heat the power battery pack, and the internal circulation is cooled by the compressor and the condenser to cool the power battery pack; the three-way valve Y3 and the three-way valve Y2 in the displaced position, the electronic water pump M1, the power battery pack, the three-way valve Y2 in the displaced position, the DC / DC and the engine MOTOR constitute an external circulation, and the external circulation heats the power battery pack by preheating the engine. The water outlet temperature of the external circulation in the present invention is the water temperature at the input water pipe of the three-way valve Y1.

[0039] In an embodiment of the present invention, the heating control method in the slow charging mode based on the above power battery thermal management control system is specifically as follows:

[0040] When the minimum temperature T1 of the power battery is lower than 5°C, the VCU controller starts the internal circulation, that is, starts the electronic water pump M1 and the heater PTC in sequence, controls the three-way valve Y2 and the three-way valve Y1 to be in the normal position, and the battery management system BMS of the power battery regularly detects the minimum temperature T1 of the power battery. When T1>5°C, the power battery is slowly charged. When T1 reaches 10°C, the electronic water pump M1 and the heater PTC are turned off in sequence.

[0041] In an embodiment of the present invention, the heating control method in the fast charging mode based on the above power battery thermal management control system is specifically as follows:

[0042] When the minimum temperature T1 of the power battery is lower than 15°C, the VCU controller starts the internal circulation, that is, starts the electronic water pump M1 and the heater PTC in sequence, controls the three-way valve Y2 and the three-way valve Y1 to be in the normal position, and the battery management system BMS of the power battery regularly detects the minimum temperature T1 of the power battery. When T1>5°C, the power battery is slowly charged. When T1 reaches 15°C, the electronic water pump M1 and the heater PTC are turned off in sequence.

[0043] In an embodiment of the present invention, the discharge process heating method based on the above power battery thermal management control system is specifically as follows:

[0044] If the lowest temperature T1 of the power battery is lower than 0°C, the VCU controller starts the internal circulation in sequence, i.e. starts the electronic water pump M1 and the heater PTC, controls the three-way valve Y2 and the three-way valve Y1 to be in the normal position, and starts the large circulation at the same time, i.e. starts the electronic water pump M2, controls the three-way valve Y3 to be in the variable position, and the battery management system BMS of the power battery pack regularly detects the difference between the lowest temperature T1 of the power battery and the outlet water temperature T3 of the external circulation, as well as the outlet water temperature T3 of the external circulation;

[0045] 1) If T3-T1<15℃ and T3<30℃, the power battery pack is heated by the heater PTC. When the battery pack water inlet temperature T2>45℃, the heater PTC relay is disconnected;

[0046] 2) If T3-T1≥15℃ and T3<30℃, the VCU controller controls the PTC relay to be in the disconnected state, turns off the electronic water pump M2, and the three-way valve Y1 and the three-way valve Y2 are in the shifted position, and the power battery pack is heated by the excess heat of the engine;

[0047] 3) If T3-T1<15℃ and T3≥30℃, the power battery pack is heated by the heater PTC, the three-way valve Y3 is controlled to be in the normal position, and the cooling fan is started. When the battery pack water inlet temperature T2>45℃, the heater PTC relay is disconnected;

[0048] 4) If T3-T1≥15℃ and T3≥30℃, the VCU controller controls the PTC relay to be in the disconnected state, turns off the electronic water pump M2, controls the three-way valve Y1 and the three-way valve Y2 to be in the changed position, and the three-way valve Y3 to be in the normal position, starts the cooling fan, and heats the power battery pack with the excess heat of the engine, while dissipating the heat through the cooling fan.

[0049] In the embodiment of the present invention, if the power battery temperature T1>0°C, the power battery is discharged normally according to actual demand and the power matrix table, that is, no heating is required.

[0050] In an embodiment of the present invention, the cooling method in the slow charging and fast charging modes based on the above power battery thermal management control system is specifically as follows:

[0051] When 35℃≤T1≤42℃, monitor the outlet water temperature T3 of the external circulation;

[0052] 5) If T3 ≤ 25°C, start the electronic water pump M1, control the three-way valve Y1, three-way valve Y2 and three-way valve Y3 to be in a position change, and cool the power battery pack through the low-temperature coolant in the external circulation;

[0053] 6) If 25°C < T3 ≤ 30°C, start the electric water pump M1, control the three-way valves Y1 and Y2 to be in the displaced position, the three-way valve Y3 to be in the normal position, and start the cooling fan. Cool down the power battery pack through the low-temperature coolant in the external circulation, and the cooling fan cools down the coolant in the external circulation.

[0054] 7) If T3 ≥ 25°C, start the electric water pump M1 and the compressor, and control the three-way valves Y2 and Y1 to be in the normal position.

[0055] 8) When T1 < 35°C, if the difference between the maximum temperature and the minimum temperature of the power battery pack is greater than 8°C, start the electric water pump M1 and the compressor, control the three-way valves Y2 and Y1 to be in the normal position, until the difference between the maximum temperature and the minimum temperature of the power battery pack is less than 6°C, then turn off the electric water pump M1 and the compressor.

[0056] 9) When T1 ≥ 42°C, start the electric water pump M1 and the compressor, control the three-way valves Y2 and Y1 to be in the normal position, and control the chiller to be in the high gear.

[0057] In the embodiment of the present invention, the cooling method during the discharging process of the above power battery thermal management control system is specifically as follows:

[0058] For the maximum temperature T4 of the power battery pack, if 35°C ≤ T4 ≤ 42°C, start the electric water pump M1 and the compressor, and control the three-way valves Y2 and Y1 to be in the normal position; if 42°C ≤ T4 ≤ 45°C, start the electric water pump M1 and the compressor, control the three-way valves Y2 and Y1 to be in the normal position, control the chiller to be in the medium gear, and the default gear of the chiller is the low gear; when T4 ≥ 45°C, start the electric water pump M1 and the compressor, control the three-way valves Y2 and Y1 to be in the normal position, and control the chiller to be in the high gear.

[0059] In the embodiment of the present invention, a plurality of temperature sensors are provided on the power battery pack, and the plurality of temperature sensors are arranged at different positions of the power battery pack. The above temperature sensors are used to detect the temperatures at different positions of the power battery pack. Among them, the maximum temperature is the highest temperature of the power battery pack, and the minimum temperature is the lowest temperature of the power battery pack.

[0060] In the embodiment of the present invention, when the three-way valve Y1 is in the normal position (Y1A), the output pipeline of the three-way valve Y1 is connected to the electronic water pump M2, and when the three-way valve Y1 is in the displacement position (Y1B), the output pipeline of the three-way valve Y1 is connected to the electronic water pump M1; when the three-way valve Y2 is in the normal position (Y2B), the output pipeline of the three-way valve Y2 is connected to the heat exchanger Chiller, and when the three-way valve Y2 is in the displacement position (Y2A), the output pipeline of the three-way valve Y2 is connected to the DC / DC; when the three-way valve Y3 is in the normal position (Y3B), the output pipeline of the three-way valve Y3 is connected to the input pipeline of the three-way valve Y1 through the cooling fan, and when the three-way valve Y3 is in the displacement position (Y3A), the output pipeline of the three-way valve Y3 is directly connected to the input pipeline of the three-way valve Y1.

[0061] The power battery thermal management system provided by the present invention includes an internal cycle and an external cycle. The internal cycle or the external cycle can be selected to heat or cool the power battery pack to different degrees, and the temperature of the power battery pack can be more accurately regulated.

[0062] Obviously, the specific implementation of the present invention is not limited to the above-mentioned methods. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention, they are all within the protection scope of the present invention.

Claims

1. A power battery thermal management control method, characterized in that: The power battery thermal management control system includes: The heat exchanger Chiller, the heater PTC, the electronic water pump M1 and the power battery pack are connected in sequence through pipelines. The output pipeline of the power battery pack is connected to the heat exchanger Chiller or the input pipeline of the engine through the three-way valve Y2. The output pipeline of the engine is connected to the cooling fan or the input pipeline of the three-way valve Y1 through the three-way valve Y3. The output pipeline of the cooling fan is connected to the input pipeline of the three-way valve Y1. The output pipeline of the three-way valve Y1 is connected to the input pipeline of the electronic water pump M1 or the electronic water pump M2. The output pipeline of the electronic water pump M2 is connected to the input pipeline of the engine. The refrigerant in the heat exchanger Chiller is returned to the heat exchanger Chiller through the compressor and the condenser in sequence. The compressor, heater PTC, electronic water pump M1, electronic water pump M2, cooling fan, heat exchanger Chiller, three-way valve Y1, three-way valve Y2 and three-way valve Y3 are all connected to the VCU controller; Based on the power battery thermal management control system, the power battery pack is heated and cooled during the charging and discharging process, and the charging process includes a fast charging mode and a slow charging mode; The heating control method in the slow charging mode is as follows: When the lowest temperature T1 of the power battery is lower than 5°C, the VCU controller starts the electronic water pump M1 and the heater PTC in sequence, controls the three-way valve Y2 and the three-way valve Y1 to be in the normal position, and regularly detects the lowest temperature T1 of the power battery. When T1>5°C, the power battery is slowly charged. When T1 reaches 10°C, the electronic water pump M1 and the heater PTC are shut down in sequence. When the three-way valve Y1 is in the normal position, the output pipeline of the three-way valve Y1 is connected to the electronic water pump M2, and when the three-way valve Y1 is in the changed position, the output pipeline of the three-way valve Y1 is connected to the electronic water pump M1; when the three-way valve Y2 is in the normal position, the output pipeline of the three-way valve Y2 is connected to the heat exchanger Chiller, and when the three-way valve Y2 is in the changed position, the output pipeline of the three-way valve Y2 is connected to the DC / DC; when the three-way valve Y3 is in the normal position, the output pipeline of the three-way valve Y3 is connected to the input pipeline of the three-way valve Y1 through the cooling fan, and when the three-way valve Y3 is in the changed position, the output pipeline of the three-way valve Y3 is directly connected to the input pipeline of the three-way valve Y1.

2. The power battery thermal management control method according to claim 1, characterized in that: The system further comprises: an expansion pot, and another output pipeline of the cooling fan is connected to the input pipeline of the three-way valve Y1 through the expansion pot.

3. The power battery thermal management control method according to claim 1, characterized in that: The system further comprises: DC / DC is installed between the output pipeline of the electronic water pump M2 and the input pipeline of the engine.

4. The power battery thermal management control method according to claim 1, characterized in that: The heating control method in the fast charging mode is specifically as follows: When the minimum temperature T1 of the power battery is lower than 15°C, the VCU controller starts the electronic water pump M1 and the heater PTC in sequence, and controls the three-way valve Y2 and the three-way valve Y1 to be in the normal position. The battery management system BMS of the power battery regularly detects the minimum temperature T1 of the power battery. When T1>5°C, the power battery is slowly charged. When T1 reaches 15°C, the electronic water pump M1 and the heater PTC are turned off in sequence.

5. The power battery thermal management control method according to claim 1, characterized in that: The heating control method during the discharge process is as follows: If the minimum temperature T1 of the power battery is lower than 0°C, the VCU controller starts the electronic water pump M1 and the heater PTC in sequence, controls the three-way valves Y2 and Y1 to be in the normal position, turns on the electronic water pump M2 at the same time, controls the three-way valve Y3 to be in the displaced position, and the battery management system BMS of the power battery pack periodically detects the difference between the minimum temperature T1 of the power battery and the outlet water temperature T3 of the external circulation and the outlet water temperature T3 of the external circulation; 1) If T3 - T1 < 15°C and T3 < 30°C, heat the power battery pack through the heater PTC. When the inlet water temperature T2 of the battery pack > 45°C, then disconnect the heater PTC relay; 2) If T3 - T1 ≥ 15°C and T3 < 30°C, then the VCU controller controls the PTC relay to be in the off state, turns off the electronic water pump M2, and the three-way valves Y1 and Y2 are in the displaced position, and heat the power battery pack through the excess heat of the engine; 3) If T3 - T1 < 15°C and T3 ≥ 30°C, heat the power battery pack through the heater PTC, control the three-way valve Y3 to be in the normal position, and start the cooling fan. When the inlet water temperature T2 of the battery pack > 45°C, then disconnect the heater PTC relay; 4) If T3 - T1 ≥ 15°C and T3 ≥ 30°C, then the VCU controller controls the PTC relay to be in the off state, turns off the electronic water pump M2, controls the three-way valves Y1 and Y2 to be in the displaced position, the three-way valve Y3 is in the normal position, starts the cooling fan, heats the power battery pack through the excess heat of the engine, and dissipates heat through the cooling fan at the same time.

6. The power battery thermal management control method according to claim 1, characterized in that: The slow charge mode and the cooling method in the slow charge mode are as follows: When 35°C ≤ T1 ≤ 42°C, monitor the outlet water temperature T3 of the external circulation; 5) If T3 ≤ 25°C, start the electronic water pump M1, control the three-way valves Y1, Y2 and Y3 to be in the displaced position, and cool down the power battery pack through the low-temperature coolant in the external circulation; 6) If 25°C < T3 ≤ 30°C, start the electronic water pump M1, control the three-way valves Y1 and Y2 to be in the displaced position, the three-way valve Y3 is in the normal position, and start the cooling fan, cool down the power battery pack through the low-temperature coolant in the external circulation, and the cooling fan dissipates heat from the coolant in the external circulation; 7) If T3 ≥ 25°C, start the electronic water pump M1 and the compressor, and control the three-way valves Y2 and Y1 to be in the normal position; 8) When T1 < 35°C, if the difference between the highest temperature and the lowest temperature of the power battery pack is greater than 8°C, start the electronic water pump M1 and the compressor, control the three-way valves Y2 and Y1 to be in the normal position, until the difference between the highest temperature and the lowest temperature of the power battery pack is less than 6°C, then turn off the electronic water pump M1 and the compressor; 9) When T1 ≥ 42°C, start the electronic water pump M1 and the compressor, control the three-way valves Y2 and Y1 to be in the normal position, and control the heat exchanger chiller to be in the high gear.

7. The power battery thermal management control method according to claim 1, characterized in that: The cooling method during the discharging process is as follows: If the maximum temperature T4 of the power battery pack is 35℃≤T4≤42℃, start the electronic water pump M1 and the compressor, and control the three-way valve Y2 and the three-way valve Y1 to be in the normal position; if 42℃≤T4≤45℃, start the electronic water pump M1 and the compressor, control the three-way valve Y2 and the three-way valve Y1 to be in the normal position, control the heat exchanger Chiller to be in the middle position, and the default gear of the heat exchanger is the low gear; when T4≥45℃, start the electronic water pump M1 and the compressor, control the three-way valve Y2 and the three-way valve Y1 to be in the normal position, and control the heat exchanger Chiller to be in the high position.

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