Thermal management system with feedforward control and method of managing the same

Abstract

The present application relates to the technical field of vehicle battery thermal management, and discloses a thermal management system with feedforward control, which comprises a compressor, the outlet of the compressor is connected with an external heat exchanger, the outlet of the external heat exchanger is divided into two branches, the first branch is connected with an evaporator through a first electronic expansion valve, the evaporator is connected with a gas-liquid separator through a one-way valve, the second branch is connected with a plate heat exchanger through a second electronic expansion valve, the plate heat exchanger is connected with the gas-liquid separator, the gas-liquid separator is connected with the compressor, the plate heat exchanger is connected with a battery, the battery is connected with the plate heat exchanger through an antifreeze pump, and the compressor, the first electronic expansion valve and the second electronic expansion valve are connected with a feedforward controller. The present application also discloses a management method of the thermal management system with feedforward control. The thermal management system with feedforward control and the management method thereof introduce feedforward control, so that the thermal management system can quickly reach stability, and the problem that the evaporator and the plate heat exchanger compete for flow due to too large flow resistance difference is avoided.

Description

Technical Field

[0001] This invention relates to the field of vehicle battery thermal management technology, specifically to a thermal management system with feedforward control and its management method. Background Technology

[0002] When new energy vehicles have cooling needs in both the passenger compartment and the battery, the different resistances on both sides of the different thermal management systems have different effects on the flow distribution to the evaporator and plate heat exchanger. If PID regulation is directly applied to both, the flow on both sides will oscillate, causing the compressor speed to fluctuate. The target control of the air conditioning outlet temperature and the battery side water temperature will be unstable, and the system parameters will be unstable, which will shorten the life of electrical components and prolong the system adjustment time.

[0003] Chinese Patent (Publication Date: March 29, 2024, Publication No.: CN117774615A) discloses a method, apparatus, and vehicle for determining a refrigerant circuit for thermal management, relating to the field of vehicle technology. The main technical solution includes: obtaining a first refrigerant circuit combination corresponding to the passenger compartment and a second refrigerant circuit combination corresponding to the battery; combining available refrigerant circuits common to the first and second refrigerant circuit combinations to form a third refrigerant circuit combination, and determining it as the execution circuit for refrigerant circulation. By identifying refrigerant circuits that can respectively meet the thermal management requirements of the battery and passenger compartment, and matching the identified refrigerant circuits, a set of refrigerant circuits that can simultaneously meet the heating and cooling requirements of the battery and passenger compartment is obtained. This achieves the selection of a refrigerant circuit that simultaneously meets the heating and cooling requirements of the passenger compartment and battery based on the status of the refrigerant circuits. Furthermore, the combination of multiple refrigerant circuits can effectively avoid the inability to meet the heating and cooling requirements of the passenger compartment and / or battery due to unavailable refrigerant circuits.

[0004] Chinese Patent (Publication Date: March 29, 2024, Publication No.: CN117774605A) discloses a vehicle thermal management system, a vehicle, and a control method for the vehicle thermal management system. The vehicle thermal management system includes: an air conditioning system; a battery thermal management system, including a battery pack and a plate heat exchanger connected to the air conditioning system, the plate heat exchanger and the battery pack forming a first coolant circuit; an electric drive thermal management system, including an electric drive module and a radiator, the radiator and the electric drive module forming a second coolant circuit; a first valve, and a second valve; wherein the plate heat exchanger, the first valve, the radiator, and the second valve are sequentially connected to form a coupling circuit. Thus, when both the first and second valves are open, the battery thermal management system and the electric drive thermal management system can be connected, allowing the two thermal management systems to operate coupled and share the plate heat exchanger and radiator, thereby improving the utilization rate of the heat dissipation components in the vehicle thermal management system.

[0005] Chinese Patent (Publication Date: March 29, 2024, Publication No.: CN117774778A) discloses a vehicle battery system heating method, apparatus, medium, and vehicle. The vehicle battery system heating method includes: in response to an ambient temperature lower than a battery heating temperature threshold, acquiring the power demanded by the vehicle during driving and the heating power that the vehicle can provide to the battery at the ambient temperature; based on the heating power, determining the heating time required for the battery to heat from the ambient temperature to a target heating cutoff temperature; based on the ratio of the remaining total discharge capacity to the rated capacity of the battery system, determining the target state of charge of the battery when the vehicle starts heating the battery, wherein the remaining total discharge capacity is the product of the sum of the demanded power and the heating power and the heating time; and in response to the battery reaching the target state of charge, heating the battery based on the heating power. This disclosed technical solution can improve the low-temperature driving range of pure electric vehicles and optimize the user's driving experience.

[0006] However, the aforementioned patents still suffer from the problem of the evaporator and plate heat exchanger competing for flow due to the large difference in flow resistance. This leads to unstable control of the air conditioner outlet temperature and battery-side water temperature, resulting in unstable system parameters, shortened lifespan of electrical components, and extended system adjustment time. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of the above-mentioned technologies by providing a thermal management system with feedforward control and its management method. By introducing feedforward control, the thermal management system can quickly reach stability, extend the life of electrical components, and avoid the problem of the evaporator and plate heat exchanger competing for flow due to excessive differences in flow resistance.

[0008] To achieve the above objectives, the thermal management system with feedforward control designed in this invention includes a compressor. The outlet of the compressor is connected to an external heat exchanger. The external heat exchanger is equipped with a fan that communicates with the outside environment. The outlet of the external heat exchanger is divided into two branches. The first branch is connected to an evaporator through a first electronic expansion valve. The evaporator is equipped with a blower that communicates with the passenger compartment. The evaporator is connected to the inlet of a gas-liquid separator through a one-way valve. The second branch is connected to the inlet of a channel of a plate heat exchanger through a second electronic expansion valve. The outlet of this channel of the plate heat exchanger is connected to the inlet of the gas-liquid separator. The outlet of the gas-liquid separator is connected to the compressor. The outlet of the other channel of the plate heat exchanger is connected to a battery. The battery is connected to the inlet of this channel of the plate heat exchanger through an antifreeze pump. The compressor, the first electronic expansion valve, and the second electronic expansion valve are connected to a feedforward controller.

[0009] A management method for a thermal management system with feedforward control as described in claim 1, wherein when both the passenger compartment and the battery have cooling requirements, the battery level is divided according to the urgency of cooling of the battery, and the calibration values ​​of the first electronic expansion valve, the second electronic expansion valve and the compressor in the feedforward stage are obtained according to bench calibration or theoretical calculation for different battery levels, and feedforward control is adopted before PID control.

[0010] Preferably, at time t1, the battery cooling demand and the passenger cabin cooling demand are received. The feedforward controller determines that the current battery temperature does not exceed its safety limit, records the battery level as 1, and adjusts the opening of the first electronic expansion valve and the second electronic expansion valve. At time t2, the opening of the first electronic expansion valve is adjusted to the calibrated value D1 and maintained, and the opening of the second electronic expansion valve is adjusted to the calibrated value E1 and maintained, where D1 > E1. At time t3, the compressor speed is adjusted to the calibrated value N1. Then, the opening of the first electronic expansion valve is controlled by PID based on the subcooling degree, and the compressor speed is controlled by PID based on the NTC temperature of the evaporator. After the opening of the second electronic expansion valve is maintained at the calibrated value E1 until time t4, the opening of the second electronic expansion valve is controlled by PID based on the battery water temperature.

[0011] Preferably, at time t1', the battery cooling demand and the passenger cabin cooling demand are received. The feedforward controller determines that the current battery temperature exceeds its safety limit, records the battery level as 2, and adjusts the opening of the first electronic expansion valve and the second electronic expansion valve. At time t2', the opening of the first electronic expansion valve is adjusted to the calibrated value D1' and maintained, and the opening of the second electronic expansion valve is adjusted to the calibrated value E1' and maintained, where D1' < E1'. At time t3', the compressor speed is adjusted to the calibrated value N1'. Then, the opening of the second electronic expansion valve is controlled by PID based on the subcooling degree, and the compressor speed is controlled by PID based on the battery water temperature. After the opening of the first electronic expansion valve is maintained at the calibrated value D1 until time t4', the opening of the second electronic expansion valve is controlled by PID based on the NTC temperature of the evaporator.

[0012] Preferably, assuming t2 < t2a < t3, at time t2a, the compressor speed reaches bN1 through rapid loading, where b < 1, and then the compressor enters soft start. At time t3, the speed reaches the calibrated value N1.

[0013] Preferably, let t2' < t2'a < t3'. At time t2'a, the compressor speed reaches bN1' through rapid loading, where b < 1. Then, the compressor enters soft start, and at time t3', the speed reaches the calibrated value N1'.

[0014] Preferably, the calibration value of the opening degree of the first electronic expansion valve in the feedforward stage is related to the ambient temperature of the passenger compartment and the air volume of the blower. When the ambient temperature of the passenger compartment is higher, the calibration value of the opening degree of the first electronic expansion valve in the feedforward stage is higher. When the air volume of the blower is larger, the calibration value of the opening degree of the first electronic expansion valve in the feedforward stage is higher.

[0015] Preferably, the calibrated value of the opening of the second electronic expansion valve in the feedforward stage is related to the battery temperature; the higher the battery temperature, the higher the calibrated value of the opening of the second electronic expansion valve in the feedforward stage.

[0016] Preferably, the calibrated value of the compressor speed in the feedforward phase is related to the cooling capacity requirement of the passenger compartment; the greater the cooling capacity requirement of the passenger compartment, the higher the speed of the compressor.

[0017] Preferably, the compressor speed during the feedforward phase is calibrated to be related to the battery temperature; the higher the battery temperature, the higher the compressor speed.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. By introducing feedforward control and calibrating the timing of feedforward control for each electrical component, the thermal management system can quickly reach stability, thus extending the lifespan of the electrical components.

[0020] 2. A soft start time is reserved from the start-up of the compressor until it reaches the feedforward speed to prevent compressor overshoot and further shorten the stabilization time;

[0021] 3. The feedforward values ​​are calibrated according to the urgency of battery cooling needs, and the feedforward control time is extended for some electrical components to avoid the problem of the evaporator and plate heat exchanger competing for flow due to excessive differences in flow resistance. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the thermal management system with feedforward control according to the present invention;

[0023] Figure 2 Diagram showing the control method of a thermal management system with feedforward control when the battery level is 1.

[0024] Figure 3 This diagram illustrates the control method of a thermal management system with feedforward control when the battery level is 2.

[0025] The components in the diagram are labeled as follows:

[0026] 1. Compressor; 2. External heat exchanger; 3. Fan; 4. Evaporator; 5. Blower; 6. Check valve; 7. Gas-liquid separator; 8. Plate heat exchanger; 9. Battery; 10. Antifreeze pump; 11. First electronic expansion valve EXV1; 12. Second electronic expansion valve EXV2. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0028] like Figure 1 As shown, a thermal management system with feedforward control includes a compressor 1. The outlet of the compressor 1 is connected to an external heat exchanger 2. The external heat exchanger 2 is equipped with a fan 3 that communicates with the outside. The outlet of the external heat exchanger 2 is divided into two branches. The first branch is connected to an evaporator 4 through a first electronic expansion valve EXV1. The evaporator 4 is equipped with a blower 5 that communicates with the passenger compartment. The evaporator 4 is connected to the inlet of a gas-liquid separator 7 through a one-way valve 6. The second branch is connected to the inlet of a channel of a plate heat exchanger 8 through a second electronic expansion valve EXV2. The outlet of this channel of the plate heat exchanger 8 is connected to the inlet of the gas-liquid separator 7. The outlet of the gas-liquid separator 7 is connected to the compressor 1. The outlet of the other channel of the plate heat exchanger 8 is connected to a battery 9. The battery 9 is connected to the inlet of this channel of the plate heat exchanger 8 through an antifreeze pump 10. The compressor 1, the first electronic expansion valve EXV1, and the second electronic expansion valve EXV2 are connected to a feedforward controller.

[0029] When the thermal management system with feedforward control in this embodiment is used, if there is a cooling demand in both the crew cabin and the battery 9, the battery level is divided according to the urgency of cooling of the battery 9. The calibration values ​​of the first electronic expansion valve EXV1, the second electronic expansion valve EXV2 and the compressor 1 in the feedforward stage are obtained according to bench calibration or theoretical calculation for different battery levels. Feedforward control is adopted before PID control.

[0030] Specifically, refer to Figure 2Assuming that at time t1, the cooling requirements of battery 9 and the passenger cabin are received, the feedforward controller determines that the current temperature of battery 9 has not exceeded its safety limit, and the battery level is recorded as 1. At this time, the actual opening degree of the first electronic expansion valve EXV1 is D2, the actual opening degree of the second electronic expansion valve EXV2 is E2, and the actual speed of the compressor is N2. The opening degrees of the first electronic expansion valve EXV1 and the second electronic expansion valve EXV2 are adjusted. At time t2, the opening degree of the first electronic expansion valve EXV1 is adjusted to the calibrated value D1 and maintained. The opening of the second electronic expansion valve EXV2 is adjusted to the calibrated value E1 and maintained, D1 > E1. Assuming t2 < t2a < t3, at time t2a, the compressor 1's speed reaches bN1 through rapid loading, where b < 1 (0.95 in this embodiment). Then, the compressor 1 enters soft start mode. At time t3, the speed reaches the calibrated value N1. At this time, the actual temperature of the evaporator 4 drops from C2 to C3, the actual inlet water temperature of the battery 9 drops from B2 to B3, and the subcooling of the external heat exchanger 2 increases from K2 to K3. As can be seen, the differences between the three control variables and the target values ​​are reduced before entering PID control, which can make PID control slower and avoid over-adjustment due to excessive adjustment speed, thus reducing the time to reach the stable stage. Then, the opening degree of the first electronic expansion valve EXV1 is controlled by PID based on the subcooling degree of the external heat exchanger 2, and the speed of the compressor 1 is controlled by PID based on the NTC temperature of the evaporator 4. After the opening degree of the second electronic expansion valve EXV2 is maintained at the calibrated value E1 until time t4, the opening degree of the second electronic expansion valve EXV2 is controlled by PID based on the water temperature of the battery 9. In this embodiment, the time from time t3 to time t4 is 20 seconds. By extending the feedforward control time of the second electronic expansion valve EXV2, more refrigerant can flow to the evaporator 4, giving priority to meeting the cooling needs of the passenger compartment, and the adjustment is stable, avoiding the problem of "competing for flow" between the evaporator 4 and the plate heat exchanger 8. Finally, at time t5, the target value of the evaporator 4 temperature C1 is achieved, the target value of the battery 9 inlet water temperature is B1, and the target value of the subcooling degree of the external heat exchanger 2 is K1.

[0031] refer to Figure 3Assuming that at time t1', the cooling requirements of battery 9 and the passenger cabin are received, the feedforward controller determines that the current temperature of battery 9 exceeds its safety limit, and the battery level is denoted as 2. At this time, the actual opening degree of the first electronic expansion valve EXV1 is D2', the actual opening degree of the second electronic expansion valve EXV2 is E2', and the actual speed of the compressor is N2'. The opening degrees of the first electronic expansion valve EXV1 and the second electronic expansion valve EXV2 are adjusted. At time t2', the opening degree of the first electronic expansion valve EXV1 is adjusted to the calibrated value D1' and maintained. The opening of the second electronic expansion valve EXV2 is adjusted to the calibrated value E1' and maintained, D1' < E1'. Assume t2' < t2'a < t3'. At time t2'a, the compressor 1 speed reaches bN1' through rapid loading, b < 1. Then, compressor 1 enters soft start. At time t3', the speed reaches the calibrated value N1'. At this time, the actual temperature of evaporator 4 drops from C2' to C3', the actual inlet water temperature of battery 9 drops from B2' to B3', and the subcooling of external heat exchanger 2 increases from K2' to K3. As can be seen, the differences between the three control variables and the target values ​​are reduced before entering PID control, which can make PID control slower and avoid over-adjustment due to excessive adjustment speed, thus reducing the time to reach the stable stage. Then, the opening degree of the second electronic expansion valve EXV2 is controlled by PID based on the subcooling degree of the external heat exchanger 2, and the speed of the compressor 1 is controlled by PID based on the water temperature of the battery 9. After the opening degree of the first electronic expansion valve EXV1 is maintained at the calibrated value D1 until time t4', the opening degree of the second electronic expansion valve EXV2 is controlled by PID based on the NTC temperature of the evaporator 4. In this embodiment, the time from time t3' to time t4' is 20 seconds. By extending the feedforward control time of the first electronic expansion valve EXV1, more refrigerant can flow to the battery 9, giving priority to meeting the cooling needs of the battery 9, and the adjustment is stable, avoiding the problem of "competing for flow" between the evaporator 4 and the plate heat exchanger 8. Finally, at time t5', the target value of the evaporator 4 temperature C1' is achieved, the target value of the battery 9 inlet water temperature is B1', and the target value of the subcooling degree of the external heat exchanger 2 is K1'.

[0032] In addition, in this embodiment, the calibration value of the opening degree of the first electronic expansion valve EXV1 in the feedforward stage is related to the ambient temperature of the crew cabin and the air volume of the blower 5. When the ambient temperature of the crew cabin is higher, the calibration value of the opening degree of the first electronic expansion valve EXV1 in the feedforward stage is higher. When the air volume of the blower 5 is larger, the calibration value of the opening degree of the first electronic expansion valve EXV1 in the feedforward stage is higher.

[0033] The opening degree of the second electronic expansion valve EXV2 during the feedforward stage is related to the temperature of battery 9. The higher the temperature of battery 9, the higher the opening degree of the second electronic expansion valve EXV2 during the feedforward stage.

[0034] In battery level 1, the rated speed of compressor 1 during the feedforward phase is related to the cooling capacity requirement of the passenger compartment; the greater the cooling capacity requirement of the passenger compartment, the higher the speed of compressor 1. In battery level 2, the rated speed of compressor 1 during the feedforward phase is related to the temperature of battery 9; the higher the temperature of battery 9, the higher the speed of compressor 1.

[0035] This invention relates to a thermal management system and its management method with feedforward control. Feedforward control is introduced, and the timing of feedforward control for each electrical component is calibrated, enabling the thermal management system to quickly reach stability and extending the lifespan of the electrical components. A soft-start time is reserved from compressor 1's start-up to reaching the feedforward speed to prevent overshoot and further shorten the stabilization time. The feedforward value is calibrated according to the urgency of the battery 9's cooling requirements, and the feedforward control time for some electrical components is extended to avoid the problem of the evaporator 4 and plate heat exchanger 8 competing for flow due to excessive differences in flow resistance.

Claims

1. A management method for a thermal management system with feedforward control, the thermal management system including a compressor (1), characterized in that: The compressor (1) has an outlet connected to an external heat exchanger (2). The external heat exchanger (2) is equipped with a fan (3) that communicates with the outside. The outlet of the external heat exchanger (2) is divided into two branches. The first branch is connected to an evaporator (4) through a first electronic expansion valve (EXV1). The evaporator (4) is equipped with a blower (5) that communicates with the crew compartment. The evaporator (4) is connected to the inlet of a gas-liquid separator (7) through a one-way valve (6). The second branch is connected to a plate heat exchanger through a second electronic expansion valve (EXV2). The plate heat exchanger (8) has one channel inlet, and the outlet of this channel is connected to the inlet of the gas-liquid separator (7). The outlet of the gas-liquid separator (7) is connected to the compressor (1). The outlet of the other channel of the plate heat exchanger (8) is connected to a battery (9). The battery (9) is connected to the inlet of this channel of the plate heat exchanger (8) via an antifreeze pump (10). The compressor (1), the first electronic expansion valve (EXV1), and the second electronic expansion valve (EXV2) are connected to a feedforward controller. In the management method, when both the crew cabin and the battery (9) have cooling requirements, the battery level is divided according to the urgency of cooling of the battery (9). The calibration values ​​of the first electronic expansion valve (EXV1), the second electronic expansion valve (EXV2) and the compressor (1) in the feedforward stage are obtained according to bench calibration or theoretical calculation under different battery levels. Feedforward control is adopted before PID control is performed. Assuming that at time t1, the cooling demand from the battery (9) and the crew cabin is received, the feedforward controller determines that the current temperature of the battery (9) does not exceed its safety limit, records the battery level as 1, and adjusts the opening of the first electronic expansion valve (EXV1) and the second electronic expansion valve (EXV2). At time t2, the opening of the first electronic expansion valve (EXV1) is adjusted to the calibrated value D1 and maintained, and the opening of the second electronic expansion valve (EXV2) is adjusted to the calibrated value E1 and maintained, where D1 > E1. At time t3, the speed of the compressor (1) is adjusted to the calibrated value N1. Then, the first electronic expansion valve (EXV1)... The opening degree of V1) is controlled by PID based on the subcooling degree of the external heat exchanger (2), and the speed of the compressor (1) is controlled by PID based on the NTC temperature of the evaporator (4). The opening degree of the second electronic expansion valve (EXV2) is maintained at the calibrated value E1 until time t4. Then, the opening degree of the second electronic expansion valve (EXV2) is controlled by PID based on the water temperature of the battery (9). Let t2 < t2a < t3. At time t2a, the speed of the compressor (1) reaches bN1 through rapid loading, b < 1. Then the compressor (1) enters soft start. At time t3, the speed reaches the calibrated value N1. Assuming that at time t1', the cooling demand from the battery (9) and the crew cabin is received, the feedforward controller determines that the current temperature of the battery (9) exceeds its safety limit, records the battery level as 2, and adjusts the opening of the first electronic expansion valve (EXV1) and the second electronic expansion valve (EXV2). At time t2', the opening of the first electronic expansion valve (EXV1) is adjusted to the calibrated value D1' and maintained, and the opening of the second electronic expansion valve (EXV2) is adjusted to the calibrated value E1' and maintained, where D1' < E1'. At time t3', the speed of the compressor (1) is adjusted to the calibrated value N1', and then the second electronic expansion valve (EXV1) is adjusted to the calibrated value N1'. 2) The opening degree is controlled by PID based on the subcooling degree of the external heat exchanger (2). The speed of the compressor (1) is controlled by PID based on the water temperature of the battery (9). After the opening degree of the first electronic expansion valve (EXV1) is maintained at the calibrated value D1' until t4', the opening degree of the second electronic expansion valve (EXV2) is controlled by PID based on the NTC temperature of the evaporator (4). Let t2' < t2'a < t3'. At t2'a, the speed of the compressor (1) reaches bN1' through rapid loading, b < 1. Then the compressor (1) enters soft start. At t3', the speed reaches the calibrated value N1'.

2. The management method of the thermal management system with feedforward control according to claim 1, characterized in that: The calibration value of the opening of the first electronic expansion valve (EXV1) in the feedforward stage is related to the ambient temperature of the crew cabin and the air volume of the blower (5). When the ambient temperature of the crew cabin is higher, the calibration value of the opening of the first electronic expansion valve (EXV1) in the feedforward stage is higher. When the air volume of the blower (5) is larger, the calibration value of the opening of the first electronic expansion valve (EXV1) in the feedforward stage is higher.

3. The management method of the thermal management system with feedforward control according to claim 1, characterized in that: The opening degree of the second electronic expansion valve (EXV2) in the feedforward stage is related to the temperature of the battery (9). The higher the temperature of the battery (9), the higher the opening degree of the second electronic expansion valve (EXV2) in the feedforward stage.

4. The management method of the thermal management system with feedforward control according to claim 1, characterized in that: The speed of the compressor (1) during the feedforward phase is related to the cooling capacity requirement of the passenger cabin. The greater the cooling capacity requirement of the passenger cabin, the higher the speed of the compressor (1).

5. The management method of the thermal management system with feedforward control according to claim 1, characterized in that: The speed of the compressor (1) during the feedforward stage is related to the temperature of the battery (9). The higher the temperature of the battery (9), the higher the speed of the compressor (1).

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