A power battery heating system and a water temperature control method for power battery heating

Abstract

This invention discloses a power battery heating system and a water temperature control method for power battery heating. It utilizes a three-way proportional valve and a first three-way valve to introduce engine waste heat recovery water into the power battery for heating. By adjusting the opening of the first outlet and the second outlet of the three-way proportional valve, the amount of engine cooling water entering the battery heat exchanger is adjusted, thereby achieving real-time adjustment of the desired inlet water temperature entering the battery heat exchanger. This ensures that the power battery heating inlet water temperature is controlled at the desired inlet water temperature, avoiding the impact of power battery heating on its lifespan.

Description

Technical Field

[0001] This invention belongs to the field of vehicle thermal management, specifically relating to a power battery heating system and a method for controlling the water temperature of the power battery. Background Technology

[0002] In low-temperature environments, the ion activity of power batteries decreases, leading to a significant reduction in discharge capacity. Vehicle review organizations conducted range tests on new energy vehicles in northern winters and found that their range was generally reduced by more than half, severely impacting their driving range. Therefore, increasing the temperature of the power battery in winter to enhance ion activity and thus increase battery discharge capacity has become a crucial method for improving the winter driving range of new energy vehicles.

[0003] CN111546945A discloses a heating device, heating control method, and range-extended electric vehicle for a power battery, describing the use of engine waste heat to heat the power battery. However, the heating of the power battery requires strict control over the inlet water temperature; otherwise, the battery's lifespan will be affected. When using engine waste heat to heat the power battery, the engine coolant temperature cannot be controlled. How to effectively control the inlet water temperature for power battery heating is a pressing problem that needs to be solved, but this patent application does not address this issue. Summary of the Invention

[0004] The purpose of this invention is to provide a power battery heating system and a water temperature control method for power battery heating, so as to control the inlet water temperature of the power battery heating at the desired inlet water temperature and avoid heating affecting the lifespan.

[0005] The power battery heating system of this invention includes a controller, a PTC-heated power battery water circuit, a first temperature sensor for detecting the actual inlet water temperature of the battery heat exchanger, and a second temperature sensor for detecting the actual inlet water temperature of the power battery. The first and second temperature sensors are installed in the PTC-heated power battery water circuit and connected to the controller. The heating system also includes a three-way proportional valve, a first three-way valve, an engine waste heat recovery water circuit, and a third temperature sensor for detecting engine coolant temperature and connected to the controller. The inlet of the three-way proportional valve is connected to the outlet of the PTC-heated power battery water circuit; the first outlet of the three-way proportional valve is connected to the first inlet of the first three-way valve; the outlet of the first three-way valve is connected to the inlet of the PTC-heated power battery water circuit; the second outlet of the three-way proportional valve is connected to the inlet of the engine waste heat recovery water circuit; and the outlet of the engine waste heat recovery water circuit is connected to the second inlet of the first three-way valve. The controller is connected to a three-way proportional valve. The controller controls the opening of the first and second outlets of the three-way proportional valve based on the engine coolant temperature, the actual inlet water temperature of the battery heat exchanger, and the actual inlet water temperature of the power battery. This allows only a portion of the engine coolant to enter the battery heat exchanger, ensuring that the water temperature entering the battery heat exchanger reaches the desired inlet water temperature. This enables real-time adjustment of the water temperature in the pipelines entering the power battery.

[0006] Preferably, the engine waste heat recovery water circuit includes a second three-way valve, a third three-way valve, a first water pump, an engine water jacket, and a fourth three-way valve. The first inlet of the second three-way valve serves as the inlet of the engine waste heat recovery water circuit and is connected to the second outlet of the three-way proportional valve. The second inlet of the second three-way valve is connected to the outlet of the engine water tank. The outlet of the second three-way valve is connected to the first inlet of the third three-way valve. The second inlet of the third three-way valve is connected to the outlet of the engine radiator. The outlet of the third three-way valve is connected to the inlet of the first water pump. The outlet of the first water pump is connected to the inlet of the engine water jacket. The outlet of the engine water jacket is connected to the inlet of the fourth three-way valve. The first outlet of the fourth three-way valve is connected to the inlet of the engine radiator. The second outlet of the fourth three-way valve serves as the outlet of the engine waste heat recovery water circuit and is connected to the second inlet of the first three-way valve. The controller is connected to the first water pump to control its operation. A third temperature sensor is installed on the water pipe connecting the outlet of the engine water jacket to the inlet of the fourth three-way valve, thereby fully utilizing the engine waste heat to heat the power battery.

[0007] Preferably, a thermostat is installed on the water pipe connecting the first outlet of the fourth three-way valve to the inlet of the engine radiator.

[0008] Preferably, the PTC-heated power battery water circuit includes a PTC heater, a battery heat exchanger, a second water pump, a third water pump, a battery water storage tank, and a fifth three-way valve. The outlet of the battery water storage tank is connected to the first inlet of the fifth three-way valve, the outlet of the fifth three-way valve is connected to the inlet of the third water pump, the outlet of the third water pump is connected to the first inlet of the battery heat exchanger, the first outlet of the battery heat exchanger is connected to the inlet of the pipeline in the power battery, the outlet of the pipeline in the power battery is connected to the second inlet of the fifth three-way valve, the inlet of the second water pump serves as the inlet of the PTC-heated power battery water circuit and is connected to the outlet of the first three-way valve, the outlet of the second water pump is connected to the inlet of the PTC heater, the outlet of the PTC heater is connected to the second inlet of the battery heat exchanger, and the second outlet of the battery heat exchanger serves as the outlet of the PTC-heated power battery water circuit and is connected to the inlet of the three-way proportional valve. The controller is connected to the second and third water pumps and controls their operation; the controller is also connected to the PTC heater and controls its operation; the first temperature sensor is installed on the water pipe connecting the second inlet of the battery heat exchanger to the outlet of the PTC heater, and the second temperature sensor is installed on the water pipe connecting the inlet of the power battery to the first outlet of the battery heat exchanger.

[0009] The water temperature control method for power battery heating according to the present invention is applied to the aforementioned power battery heating system. This water temperature control method is executed by a controller and includes:

[0010] S1. Determine if the power battery requires heating. If yes, proceed to S2; otherwise, continue with S1.

[0011] S2. Determine if the engine is running. If yes, execute S3; otherwise, execute S4.

[0012] S3. Determine whether the engine coolant temperature is greater than or equal to the preset first temperature threshold Tx. If yes, execute S5; otherwise (indicating that the engine coolant temperature is too low or the engine has stopped and the engine waste heat is not utilized), execute S4.

[0013] S4. Control the first outlet opening of the three-way proportional valve to 100% and the second outlet opening to 0, control the PTC heater to work, use the heat generated by the PTC heater to heat the power battery, and then return to execute S1.

[0014] S5. Query the preset inlet water temperature table according to the power battery temperature to obtain the current power battery heating desired inlet water temperature Ta, and then execute S6; wherein, the preset inlet water temperature table is a correspondence table between the power battery temperature and the power battery heating desired inlet water temperature obtained through calibration.

[0015] S6. Determine the current desired inlet water temperature T of the battery heat exchanger based on the current desired inlet water temperature Ta of the power battery, the actual inlet water temperature Tb of the power battery, and the previous desired inlet water temperature T of the battery heat exchanger t-1 , and then execute S7. t

[0016] S7. According to the current desired inlet water temperature T of the battery heat exchanger t and the actual inlet water temperature Tc of the battery heat exchanger, adjust the opening degrees of the first outlet and the second outlet of the three-way proportional valve to control the amount of engine cooling water introduced, so as to control the inlet water temperature flowing into the battery heat exchanger, and then return to execute S1.

[0017] Preferably, the method for determining the current desired inlet water temperature T of the battery heat exchanger in step S6 t is as follows: If Ta > Tb + Ty, then make T t = T t-1 + Tz; if Tb - Ty ≤ Ta ≤ Tb + Ty, then make T t = T t-1 ; if Ta < Tb - Ty, then make T t = T t-1 - Tz. Where, Ty represents a preset second temperature threshold, Tz represents a preset third temperature threshold, and the initial value T0 of the desired inlet water temperature of the battery heat exchanger is equal to a preset fourth temperature threshold Tv. Adjusting based on the current desired inlet water temperature Ta of the power battery and the actual inlet water temperature Tb of the power battery on the basis of the previous desired inlet water temperature of the battery heat exchanger to obtain the current desired inlet water temperature of the battery heat exchanger can make the subsequent water temperature control more accurate and reasonable.

[0018]

[0018] Preferably, the method for adjusting the opening degrees of the first outlet and the second outlet of the three-way proportional valve in step S7 is as follows: If T t > Tc + Ty, then control the opening degree of the first outlet of the three-way proportional valve to decrease by m and the opening degree of the second outlet to increase by m to increase the amount of engine cooling water introduced; if Tc - Ty ≤ T t ≤ Tc + Ty, then control the opening degrees of the first outlet and the second outlet of the three-way proportional valve to remain unchanged; if T t < Tc - Ty, then control the opening degree of the first outlet of the three-way proportional valve to increase by m and the opening degree of the second outlet to decrease by m to reduce the amount of engine cooling water introduced. Where, m represents a preset opening degree threshold, the initial value of the opening degree of the first outlet of the three-way proportional valve is 100%, and the initial value of the opening degree of the second outlet is 0.

[0019]

[0019] Preferably, the preset first temperature threshold Tx = 60 °C, the preset second temperature threshold Ty = 2 °C, the preset third temperature threshold Tz = 2 °C, the preset fourth temperature threshold Tv = 50 °C, and the preset opening degree threshold m = 1%.

[0020] Preferably, if the vehicle power supply is in the ON position, the driving heating function is turned on, the power battery temperature is less than the preset fifth temperature threshold Tu, and the power battery SOC is greater than the preset SOC threshold, then the power battery has a heating requirement; otherwise, the power battery does not have a heating requirement.

[0021] Preferably, the preset fifth temperature threshold Tu = 0℃ and the preset SOC threshold is equal to 10%.

[0022] This invention utilizes a three-way proportional valve and a first three-way valve to introduce waste heat recovery water from the engine into the power battery for heating. By adjusting the opening of the first outlet and the second outlet of the three-way proportional valve, the amount of engine cooling water entering the battery heat exchanger is adjusted, thereby achieving real-time adjustment of the desired inlet water temperature entering the battery heat exchanger. This ensures that the power battery heating inlet water temperature is controlled at the desired inlet water temperature, avoiding the impact of power battery heating on its lifespan. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the power battery heating system in this embodiment (the controller is not shown).

[0024] Figure 2 This is a flowchart of the water temperature control method for power battery heating in this embodiment. Detailed Implementation

[0025] like Figure 1 As shown, the power battery heating system in this embodiment includes a controller, a PTC heating power battery water circuit, a first temperature sensor 1 for detecting the actual inlet water temperature of the battery heat exchanger, a second temperature sensor 2 for detecting the actual inlet water temperature of the power battery, a three-way proportional valve 3, a first three-way valve 4, an engine waste heat recovery water circuit, and a third temperature sensor 5 for detecting the engine water temperature.

[0026] The engine waste heat recovery water circuit includes a second three-way valve 6, a third three-way valve 7, a first water pump 8, an engine water jacket 9, and a fourth three-way valve 10. The first inlet of the second three-way valve 6 serves as the inlet of the engine waste heat recovery water circuit and is connected to the second outlet of the three-way proportional valve 3 via a water pipe. The first outlet of the three-way proportional valve 3 is connected to the first inlet of the first three-way valve 4 via a water pipe. The second inlet of the second three-way valve 6 is connected to the outlet of the engine water tank 11 via a water pipe. The outlet of the second three-way valve 6 is connected to the first inlet of the third three-way valve 7 via a water pipe. The second inlet of the third three-way valve 7 is connected to the outlet of the engine radiator 12 via a water pipe. The outlet of the third three-way valve 7 is connected to the inlet of the first water pump 8 via a water pipe. The outlet of the first water pump 8 is connected to the engine water jacket 9. The engine water jacket 9's outlet is connected to the inlet of the fourth three-way valve 10 via a water pipe. The first outlet of the fourth three-way valve 10 is connected to the inlet of the engine radiator 12 via a water pipe. The second outlet of the fourth three-way valve 10, serving as the outlet of the engine waste heat recovery water circuit, is connected to the second inlet of the first three-way valve 4 via a water pipe. The controller is connected to the first water pump 8 to control its operation. The third temperature sensor 5 is installed on the water pipe connecting the outlet of the engine water jacket 9 to the inlet of the fourth three-way valve 10. The third temperature sensor 5 is connected to the controller and sends the detected engine water temperature to the controller for judgment. A thermostat 20 is installed on the water pipe connecting the first outlet of the fourth three-way valve 10 to the inlet of the engine radiator 12.

[0027] The PTC-heated power battery water circuit includes a PTC heater 13, a battery heat exchanger 14, a second water pump 15, a third water pump 16, a battery water storage tank 17, and a fifth three-way valve 18. The outlet of the battery water storage tank 17 is connected to the first inlet of the fifth three-way valve 18 via a water pipe. The outlet of the fifth three-way valve 18 is connected to the inlet of the third water pump 16 via a water pipe. The outlet of the third water pump 16 is connected to the first inlet of the battery heat exchanger 14 via a water pipe. The first outlet of the battery heat exchanger 14 is connected to the inlet of a pipeline in the power battery 19 via a water pipe. The outlet of the pipeline in the power battery 19 is connected to the second inlet of the fifth three-way valve 18 via a water pipe. The inlet of the second water pump 15 serves as the inlet of the PTC-heated power battery water circuit and is connected to the outlet of the first three-way valve 4 via a water pipe. The outlet of the second water pump 15 is connected to the inlet of the PTC heater 13 via a water pipe. The outlet of the PTC heater 13 is connected to the second inlet of the battery heat exchanger 14 via a water pipe. The second outlet of the battery heat exchanger 14, serving as the outlet of the PTC heating power battery water circuit, is connected to the inlet of the three-way proportional valve 3 via a water pipe. The controller is connected to the second water pump 15 and the third water pump 16, controlling their operation. The controller is also connected to the PTC heater 13, controlling its operation. The first temperature sensor 1 is installed on the water pipe connecting the second inlet of the battery heat exchanger 14 to the outlet of the PTC heater 13. The first temperature sensor 1 is connected to the controller, sending the detected actual inlet water temperature of the battery heat exchanger to the controller for judgment. The second temperature sensor 2 is installed on the water pipe connecting the inlet of the power battery 19 to the first outlet of the battery heat exchanger 14. The second temperature sensor 2 is connected to the controller, sending the detected actual inlet water temperature of the power battery to the controller for judgment. The controller is connected to the three-way proportional valve 3. The controller controls the opening degree of the first outlet and the second outlet of the three-way proportional valve 3 according to the engine water temperature, the actual inlet water temperature of the battery heat exchanger, and the actual inlet water temperature of the power battery.

[0028] like Figure 2 As shown, the water temperature control method for power battery heating in this embodiment is applied to the aforementioned power battery heating system. This water temperature control method is executed by a controller and includes:

[0029] The first step is to determine if the power battery requires heating. If so, proceed to the second step; otherwise, continue with the first step. Specifically, if the vehicle's power supply is in the ON position, the driving heating function is activated, the power battery temperature is lower than the preset fifth temperature threshold Tu (Tu = 0°C in this embodiment), and the power battery SOC is greater than the preset SOC threshold (10% in this embodiment), then the power battery requires heating; otherwise, the power battery does not require heating.

[0030] Step 2: Determine whether the engine is in operation. If so, proceed to Step 3; otherwise, proceed to Step 4.

[0031] Step 3: Determine whether the engine water temperature is greater than or equal to the preset first temperature threshold Tx (in this embodiment, Tx = 60°C). If so, proceed to Step 5; otherwise (indicating that the engine water temperature is too low or the engine has stopped, and no utilization of the engine waste heat is performed), proceed to Step 4.

[0032] Step 4: Control the first outlet opening of the three-way proportional valve 3 to be 100% and the second outlet opening to be 0, control the PTC heater 13 to operate, and use the heat generated by the operation of the PTC heater 13 to heat the power battery, and then return to execute Step 1.

[0033] Step 5: Query the preset water inlet temperature table according to the power battery temperature to obtain the current desired water inlet temperature Ta for heating the power battery, and then proceed to Step 6; wherein, the preset water inlet temperature table is a corresponding relationship table between the power battery temperature and the desired water inlet temperature for heating the power battery obtained through calibration.

[0034] Step 6: Determine whether Ta > Tb + Ty. If so, proceed to Step 7; otherwise, proceed to Step 8. Wherein, Tb represents the current actual water inlet temperature of the power battery, and Ty represents the preset second temperature threshold. In this embodiment, Ty = 2°C.

[0035] Step 7: Make T t = T t-1 + Tz, and then proceed to Step 11. Wherein, Tz represents the preset third temperature threshold, T t-1 represents the previous desired water inlet temperature of the battery heat exchanger, T t represents the current desired water inlet temperature of the battery heat exchanger, and the initial value T0 of the desired water inlet temperature of the battery heat exchanger is equal to the preset fourth temperature threshold Tv. In this embodiment, Tz = 2°C and Tv = 50°C.

[0036] Step 8: Determine whether Ta < Tb - Ty. If so, proceed to Step 9; otherwise (that is, when Tb - Ty ≤ Ta ≤ Tb + Ty), proceed to Step 10.

[0037] Step 9: Make T t = T t-1 - Tz, and then proceed to Step 11.

[0038] Step 10: Make T t = T t-1 , and then proceed to Step 11.

[0039] Step 11: Determine whether T t>Tc + Ty. If so, execute the twelfth step; otherwise, execute the thirteenth step. Here, Tc represents the actual inlet water temperature of the current battery heat exchanger.

[0040] The twelfth step: Control the opening of the first outlet of the three-way proportional valve 3 to decrease by m and the opening of the second outlet to increase by m to increase the amount of engine cooling water introduced, and then return to execute the first step. Here, m represents the preset opening threshold. The initial value of the opening of the first outlet of the three-way proportional valve is 100%, and the initial value of the opening of the second outlet is 0. In this embodiment, m = 1%.

[0041] The thirteenth step: Judge whether T t <Tc - Ty. If so, execute the fourteenth step; otherwise (that is, when Tc - Ty ≤ T t ≤ Tc + Ty), execute the fifteenth step.

[0042] The fourteenth step: Control the opening of the first outlet of the three-way proportional valve 3 to increase by m and the opening of the second outlet to decrease by m to reduce the amount of engine cooling water introduced, and then return to execute the first step.

[0043] The fifteenth step: Control the openings of both the first outlet and the second outlet of the three-way proportional valve 3 to remain unchanged, and then return to execute the first step.

Claims

1. A power battery heating system, comprising a controller, a PTC-heated power battery water circuit, a first temperature sensor (1) for detecting the actual inlet water temperature of the battery heat exchanger, and a second temperature sensor (2) for detecting the actual inlet water temperature of the power battery; the first temperature sensor (1) and the second temperature sensor (2) are installed in the PTC-heated power battery water circuit and connected to the controller; characterized in that: It also includes a three-way proportional valve (3), a first three-way valve (4), an engine waste heat recovery water circuit, and a third temperature sensor (5) for detecting engine water temperature and connected to the controller; the inlet of the three-way proportional valve (3) is connected to the outlet of the PTC heating power battery water circuit, the first outlet of the three-way proportional valve (3) is connected to the first inlet of the first three-way valve (4), the outlet of the first three-way valve (4) is connected to the inlet of the PTC heating power battery water circuit, the second outlet of the three-way proportional valve (3) is connected to the inlet of the engine waste heat recovery water circuit, and the outlet of the engine waste heat recovery water circuit is connected to the first inlet of the first three-way valve (4). Two inlet connections; the controller is connected to the three-way proportional valve (3), and controls the opening degree of the first outlet and the second outlet of the three-way proportional valve (3) according to the engine water temperature, the actual inlet water temperature of the battery heat exchanger, and the actual inlet water temperature of the power battery; wherein, the PTC heating power battery water circuit includes a PTC heater (13), a battery heat exchanger (14), a second water pump (15), a third water pump (16), a battery water storage bottle (17), and a fifth three-way valve (18), the outlet of the battery water storage bottle (17) is connected to the first inlet of the fifth three-way valve (18), and the outlet of the fifth three-way valve (18) is connected to the third water pump (16). The inlet of pump (16) is connected, the outlet of the third water pump (16) is connected to the first inlet of the battery heat exchanger (14), the first outlet of the battery heat exchanger (14) is connected to the inlet of the pipeline in the power battery (19), the outlet of the pipeline in the power battery (19) is connected to the second inlet of the fifth three-way valve (18), the inlet of the second water pump (15) serves as the inlet of the PTC heating power battery water circuit, the outlet of the second water pump (15) is connected to the inlet of the PTC heater (13), the outlet of the PTC heater (13) is connected to the second inlet of the battery heat exchanger (14), and the battery heat exchanger (14) is connected to the first inlet of the battery heat exchanger (14). The second outlet of the power battery is used as the outlet of the PTC heating power battery water circuit; the controller is connected to the second water pump (15) and the third water pump (16) to control the operation of the second water pump (15) and the third water pump (16); the controller is connected to the PTC heater (13) to control the operation of the PTC heater (13); the first temperature sensor (1) is installed on the water pipe that connects the second inlet of the battery heat exchanger (14) to the outlet of the PTC heater (13); the second temperature sensor (2) is installed on the water pipe that connects the pipeline inlet of the power battery (19) to the first outlet of the battery heat exchanger (14).

2. The power battery heating system according to claim 1, characterized in that: The engine waste heat recovery water circuit includes a second three-way valve (6), a third three-way valve (7), a first water pump (8), an engine water jacket (9), and a fourth three-way valve (10). The first inlet of the second three-way valve (6) serves as the inlet of the engine waste heat recovery water circuit. The second inlet of the second three-way valve (6) is connected to the outlet of the engine water tank (11). The outlet of the second three-way valve (6) is connected to the first inlet of the third three-way valve (7). The second inlet of the third three-way valve (7) is connected to the outlet of the engine radiator (12). The outlet of the third three-way valve (7) is connected to the first water pump (8). The inlet of pump (8) and the outlet of the first water pump (8) are connected to the inlet of the engine water jacket (9). The outlet of the engine water jacket (9) is connected to the inlet of the fourth three-way valve (10). The first outlet of the fourth three-way valve (10) is connected to the inlet of the engine radiator (12). The second outlet of the fourth three-way valve (10) serves as the outlet of the engine waste heat recovery water circuit. The controller is connected to the first water pump (8) to control the operation of the first water pump (8). The third temperature sensor (5) is installed on the water pipe that connects the outlet of the engine water jacket (9) to the inlet of the fourth three-way valve (10).

3. The power battery heating system according to claim 2, characterized in that: A thermostat (20) is installed on the water pipe connecting the first outlet of the fourth three-way valve (10) to the inlet of the engine radiator (12).

4. A method for controlling the water temperature of a power battery heater, applied to the power battery heating system as described in any one of claims 1 to 3, wherein the method is executed by a controller and includes: S1. Determine if the power battery requires heating. If yes, proceed to S2; otherwise, continue with S1. S2. Determine if the engine is running. If yes, execute S3; otherwise, execute S4. S3. Determine whether the engine coolant temperature is greater than or equal to the preset first temperature threshold Tx. If yes, execute S5; otherwise, execute S4. S4. Control the first outlet opening of the three-way proportional valve (3) to be 100% and the second outlet opening to be 0, control the PTC heater (13) to work, and then return to execute S1. S5. Query the preset water inlet temperature table according to the power battery temperature to obtain the current power battery heating desired water inlet temperature Ta, and then execute S6; wherein, the preset water inlet temperature table is a table of correspondence between the power battery temperature and the power battery heating desired water inlet temperature obtained through calibration. S6. Determine the current desired inlet water temperature T of the battery heat exchanger based on the current desired inlet water temperature Ta of the power battery, the actual inlet water temperature Tb of the power battery, and the previous desired inlet water temperature T of the battery heat exchanger t-1 , t , and then execute S7; where the method for determining the current desired inlet water temperature T of the battery heat exchanger is as follows: If Ta > Tb + Ty, then make T t = T t + Tz; if Tb - Ty ≤ Ta ≤ Tb + Ty, then make T t = T t-1 ; if Ta < Tb - Ty, then make T t = T t-1 ; Ty represents a preset second temperature threshold, Tz represents a preset third temperature threshold, and the initial value T0 of the desired inlet water temperature of the battery heat exchanger is equal to the preset fourth temperature threshold Tv;​​​​ S7. According to the expected inlet water temperature T of the current battery heat exchanger t and the actual inlet water temperature Tc of the battery heat exchanger, adjust the opening degrees of the first outlet and the second outlet of the three-way proportional valve (3), and then return to execute S1; wherein, the method for adjusting the opening degrees of the first outlet and the second outlet of the three-way proportional valve (3) is as follows: If T t >Tc + Ty, then control the opening degree of the first outlet of the three-way proportional valve (3) to decrease by m and the opening degree of the second outlet to increase by m; If Tc - Ty ≤ T t ≤Tc + Ty, then control the opening degrees of the first outlet and the second outlet of the three-way proportional valve (3) to remain unchanged; If T t <Tc - Ty, then control the opening degree of the first outlet of the three-way proportional valve (3) to increase by m and the opening degree of the second outlet to decrease by m; m represents a preset opening threshold value, the initial value of the opening degree of the first outlet of the three-way proportional valve (3) is 100%, and the initial value of the opening degree of the second outlet is 0.

5. The water temperature control method for power battery heating according to claim 4, characterized in that: The preset first temperature threshold Tx = 60℃, the preset second temperature threshold Ty = 2℃, the preset third temperature threshold Tz = 2℃, the preset fourth temperature threshold Tv = 50℃, and the preset opening threshold m = 1%.

6. The water temperature control method for power battery heating according to claim 4 or 5, characterized in that: If the vehicle's power supply is in the ON position, the driving heating function is on, the power battery temperature is lower than the preset fifth temperature threshold Tu, and the power battery SOC is higher than the preset SOC threshold, then the power battery has a heating requirement.

7. The water temperature control method for power battery heating according to claim 6, characterized in that: The preset fifth temperature threshold Tu = 0℃, and the preset SOC threshold is 10%.

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