Battery heating source selection method adopting heat pump system

Abstract

The invention belongs to the technical field of automobiles, and particularly relates to a battery heating source selection method adopting a heat pump system, a VCU judges that power battery heating operation can be executed, EXV-OHX does not fail, and when the environment temperature is larger than or equal to T1, a first mode is independently used for heating; t2 < = ambient temperature lt; when T1, heating is carried out in a second mode; ambient temperature lt; and when T1 is larger than T2, if the battery temperature is lower than Tmin and quick charging is carried out at the moment, heating is carried out in a fourth mode, and otherwise, heating is carried out in a third mode. According to the technical scheme, the battery heating function can still be achieved in a low-energy-consumption redundancy mode under the condition that a sensor or an actuator corresponding to whole vehicle heat management breaks down, meanwhile, the heat pump system can heat the battery in a low-temperature environment under the discharging working condition, and the battery heating efficiency is improved. The limitation of the battery temperature on the dynamic property of the vehicle is quickly relieved on the premise of not influencing the driving range, and the driving feeling is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of automobiles, and particularly relates to a method for selecting a heat source for battery heating using a heat pump system. Background Art

[0002] With the development of automotive electrification and intelligence, the thermal management system of electric vehicles has gradually developed towards integration. The thermal management system of electric vehicles not only affects the driving comfort of users, but also involves the issue of vehicle energy consumption. How to achieve low-energy and high-efficiency operation of the thermal management system has become a major challenge in the industry.

[0003] Currently, air source heat pumps and water heaters are often used as heat sources for power battery heating. Using air source heat pump technology can effectively improve the heating COP at -7°C and above, but at lower temperatures, the effect is average. Therefore, in the prior art, water heaters are often used to heat the battery at lower temperatures. However, the water heater has poor heating efficiency and high power consumption at low temperatures, thus having a greater impact on the vehicle's cruising range. At the same time, when the air source heat pump fails, using the water heater for alternative heating will also result in relatively high energy consumption. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for selecting a heat source for battery heating using a heat pump system, eliminating the battery water heater to solve the problems existing in the above background art.

[0005] To achieve the above purpose, the present application is implemented through the following technical solutions:

[0006] A method for selecting a heat source for battery heating using a heat pump system, comprising the following steps:

[0007] When the VCU determines that the power battery heating operation can be executed and the EXV-OHX is not failed, then:

[0008] When the ambient temperature ≥ T1, heating is performed using Mode 1 alone;

[0009] When T2 ≤ ambient temperature < T1, heating is performed using Mode 2;

[0010] When the ambient temperature < T2, if the battery temperature is lower than T min , and fast charging is being performed at this time, heating is performed using Mode 4, otherwise heating is performed using Mode 3;

[0011] If the EXV-OHX fails and the EXV-LCC fails, under the charging condition and when the battery pack is in the OA closed-loop stage, Mode 5 is used to perform low-temperature heating on the battery, otherwise, no heating is performed;

[0012] If the EXV-LCC is not failed, if the battery temperature is lower than T min, and fast charging is in progress at this time. Heating is carried out in Mode Four, otherwise heating is carried out in Mode Three.

[0013] Furthermore, Mode One means heating is carried out using only an air heat pump; Mode Two means heating is carried out using an air heat pump plus a water source heat pump; Mode Three means heating is carried out using only a water source heat pump; Mode Four means heating is carried out using a water source heat pump plus a low-efficiency air heat pump that uses a wind heating PTC to heat the air around the evaporator; Mode Five means heating is carried out using only a low-efficiency air heat pump that uses a wind heating PTC to heat the air around the evaporator.

[0014] Furthermore, for the heating method adopted in Mode One, an EXV-OHX is needed to achieve heat exchange between the refrigerant and the external air; for the heating method adopted in Mode Two, an EXV-OHX is needed to achieve heat exchange between the refrigerant and the external air and an EXV-LCC is needed to achieve heat exchange between the refrigerant and the motor coolant; for the heating methods adopted in Mode Three and Mode Four, an EXV-LCC is needed to achieve heat exchange between the refrigerant and the motor coolant; in Mode Five, heat exchange between the refrigerant and the hot air is directly achieved through an uncontrolled evaporator.

[0015] Furthermore, if the EXV-OHX is not faulty, the fault status of the ambient temperature sensor is judged. When the ambient temperature sensor is faulty, the ambient temperature value is replaced by the evaporator temperature value; if it is not faulty, the ambient temperature value is directly obtained through the ambient temperature sensor.

[0016] Furthermore, if the EXV-LCC is faulty, when the ambient temperature ≥ T2, heating is carried out in Mode One; if the ambient temperature < T2, during the discharging condition, battery heating is not carried out; during the charging condition, if the battery pack is in the OA closed-loop stage, Mode Five is used to carry out low-temperature heating of the battery, otherwise, heating is not carried out.

[0017] Furthermore, the VCU judges that the power battery heating operation can be executed. Specifically, the VCU receives the power battery temperature and its own fault status sent by the LBC controller through the CAN bus. If the lowest temperature of the power battery monomers is below the heating temperature threshold, it is judged that the power battery has a heating requirement.

[0018] Furthermore, according to the battery fault status, the battery water pump fault status, the compressor fault status, and the refrigerant amount in the pipeline, it is judged whether the self-state of the power battery meets the heating conditions.

[0019] Furthermore, if the received battery fault status shows that it has no faults itself, the battery water pump can normally transport the coolant, the compressor can operate normally to transport the refrigerant, and the refrigerant amount in the pipeline is sufficient for heat exchange, then heating is allowed and the power battery heating operation is executed. If the above conditions are not met, the battery heating operation is not executed and the system reports a fault.

[0020] The beneficial effects of the present invention are:

[0021] This technical solution can ensure that when the sensor or actuator fails in the thermal management of the vehicle, battery heating can still be achieved in an alternative mode to ensure that the battery heating function operates normally.

[0022] This technical solution is adopted in a low-temperature environment and under discharge conditions. Whether in normal mode or alternative mode, the battery can be heated with low energy consumption, and the limitation of battery temperature on vehicle power can be quickly removed without affecting the driving range. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the battery heating heat pump system architecture of the present invention.

[0024] Figure 2 A flow chart for selecting the battery heating mode of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings. The following embodiments are merely exemplary and can only be used to explain and illustrate the technical solution of the present invention, but cannot be construed as limiting the technical solution of the present invention.

[0026] In this technical proposal, the definitions of relevant abbreviations and key terms are:

[0027] EV is a pure electric vehicle, VCU is a vehicle controller, PTC is a positive temperature coefficient thermistor, and LBC is a battery controller.

[0028] This technical solution is aimed at liquid-cooled batteries. This technical solution cancels the battery water heater, and the vehicle only retains the passenger compartment air heating PTC. The battery heating is only implemented in the form of a heat pump. This technical solution proposes a method for selecting a heat source for battery heating using a heat pump system. In the event of a failure of the corresponding sensor or actuator of the vehicle thermal management, the battery heating function can still be realized in a redundant mode with low energy consumption. At the same time, in a low-temperature environment and under discharge conditions, the heat pump system can heat the battery with low energy consumption, and quickly remove the battery temperature restriction on the vehicle's power without affecting the driving range, thereby improving the driving experience.

[0029] like Figure 1 As shown, the battery thermal management system only uses a heat pump for heating, and the air-heating PTC uses PTC for the passenger compartment. This technical solution focuses on describing the process of selecting the heating source when the sensor and actuator in the thermal management system fail, and does not elaborate on the battery heat pump heating process (conventional technology in this field).

[0030] 1) The vehicle controller determines whether the power battery heating operation can be performed:

[0031] Specifically, the VCU receives the power battery temperature and its own fault status sent by the LBC controller through the CAN bus. If the lowest temperature of the power battery cell is below the heating temperature threshold, it is determined that the power battery has a heating demand. Then, based on the battery fault status, battery water pump fault status, compressor fault status and pipeline refrigerant quantity, it is determined whether the power battery's own status meets the heating conditions. If the received battery fault status shows that it has no fault, the battery water pump can normally transport coolant, the compressor can normally transport refrigerant, and the pipeline refrigerant quantity is sufficient for heat exchange, heating is allowed and the power battery heating operation is executed. If the above conditions are not met, the battery heating operation is not executed and the system reports a fault.

[0032] 2) Selection of redundant heating mode for thermal management system sensor or actuator failure:

[0033] There are three heat sources for low-temperature heating of the battery in this system, namely, air heat pump with air as heat source, water source heat pump with motor auxiliary heating function to heat the motor coolant, and low-efficiency air heat pump that actively turns on the air heating PTC to heat the air around the evaporator and then uses the hot air around the evaporator as heat source. There are three heating heat sources in total. Among them, the single low-efficiency air heat pump mode is only used in the design during the battery charging 0A closed-loop stage under the fault condition of the thermal management system.

[0034] Figure 1 EXV-OHX is used to represent the air heat exchange electronic expansion valve, EXV-OHX can control the amount of refrigerant flowing through the heat exchanger OHX, and EXV-LCC is used to represent the water source heat exchange electronic expansion valve, EXV-LCC can control the amount of refrigerant flowing through LCC.

[0035] Figure 2 Mode 1 in the corresponding flow chart indicates heating using an air heat pump alone, mode 2 indicates heating using an air heat pump plus a water source heat pump, mode 3 indicates heating using a water source heat pump alone, mode 4 indicates heating using a low-efficiency air heat pump that uses a water source heat pump plus an air-heating PTC to heat the air around the evaporator, and mode 5 indicates heating using a low-efficiency air heat pump that uses an air-heating PTC to heat the air around the evaporator. The heating method used in mode 1 requires the use of EXV-OHX to achieve heat exchange between the refrigerant and the outside air, the heating method used in mode 2 requires the use of EXV-OHX to achieve heat exchange between the refrigerant and the outside air and EXV-LCC to achieve heat exchange between the refrigerant and the motor coolant, the heating methods used in modes 3 and 4 require the use of EXV-LCC to achieve heat exchange between the refrigerant and the motor coolant, and mode 5 directly achieves heat exchange between the refrigerant and hot air through an uncontrolled evaporator.

[0036] The present application provides a method for selecting a heat source for battery heating using a heat pump system, comprising the following steps:

[0037] When it is determined that the battery can perform the heating operation, if there is no fault in the thermal management system, when the ambient temperature is ≥ T1, the air heat pump in mode 1 is used alone for heating, which has the advantages of fast heating rate and high energy efficiency ratio.

[0038] When T2≤ambient temperature<T1, the air has relatively less heat. Using mode 2 of water source heat pump plus air heat pump heating can fully utilize the air heat while increasing the heating rate.

[0039] When the ambient temperature is lower than T2, the ambient temperature is extremely low and the ambient heat is no longer usable. If the battery temperature is lower than T min And if fast charging is in progress at this time, mode four can be used for rapid heating (the output power of the fast charging pile is sufficient to support the power consumption of mode four). Otherwise, mode three is used for heating.

[0040] If the thermal management system fails, the redundant heating mode can also be selected to realize the battery heating function. When EXV-OHX fails, it means that the air heat pump cannot be used. At this time, determine whether the EXV-LCC has failed. If it fails, the water source heat pump heating method is unavailable. The above situation shows that modes one, two, three, and four are all unavailable. Under discharge conditions, consider using mode five, which has poor heating efficiency and high energy consumption, and does not heat the battery. Under charging conditions, if the battery pack is in the 0A closed-loop stage, mode five is used to heat the battery at a low temperature, otherwise, no heating is performed. If the EXV-LCC has not failed, select the corresponding mode according to the judgment conditions of modes three and four in the above mode.

[0041] If EXV-OHX has not failed, further determine the fault status of the ambient temperature sensor. When the ambient temperature sensor fails, the ambient temperature value is replaced by the evaporator temperature value. If it has not failed, the ambient temperature value is directly obtained through the ambient temperature sensor. At this time, if the EXV-LCC has no faults, select modes one, two, three, and four in the same way as described above under normal operating conditions. If the EXV-LCC has a fault, it means that modes two, three, and four are not available. When the ambient temperature is ≥T2, mode one is used to heat the battery. If the ambient temperature is <T2, consider using mode five under discharge conditions because the heating efficiency is poor and the energy consumption is high, and no battery heating is performed. Under charging conditions, if the battery pack is in the 0A closed-loop stage, mode five is used to heat the battery at a low temperature. Otherwise, no heating is performed.

[0042] In particular, when a serious fault occurs in the thermal management system and heating cannot be provided, the corresponding fault will be reported and the user will be notified to repair the vehicle to ensure the normal use of the thermal management system.

[0043] After the mode adopted for low-temperature battery heating is determined through the above steps, the vehicle controller completes the battery heating function by controlling related thermal management accessories.

[0044] The above describes in detail the structure, features and effects of the present invention based on the embodiments shown in the drawings. The above is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown in the drawings. Any changes made according to the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which still do not exceed the spirit covered by the description and drawings, should be within the protection scope of the present invention.

Claims

1. A method for selecting a heat source for battery heating using a heat pump system, characterized in that: It includes the following steps: The VCU determines that the power battery heating operation can be executed. If EXV-OHX is not failed, then: When the ambient temperature ≥ T1, heating is carried out separately using Mode 1; When T2 ≤ ambient temperature < T1, heating is carried out using Mode 2; When the ambient temperature < T2, if the battery temperature is lower than T min , and fast charging is in progress at this time, heating is carried out in Mode 4, otherwise heating is carried out in Mode 3; If EXV-OHX fails and EXV-LCC fails, under the charging condition and when the battery pack is in the OA closed-loop stage, Mode 5 is used to carry out low-temperature heating of the battery, otherwise, no heating is carried out; If EXV-LCC is not failed, if the battery temperature is lower than T min , and fast charging is in progress, mode 4 is used for heating, otherwise mode 3 is used for heating.

2. The method for selecting a heat source for battery heating using a heat pump system according to claim 1, characterized in that: Mode 1 means heating is carried out separately using an air heat pump; Mode 2 means heating is carried out using an air heat pump plus a water source heat pump; Mode 3 means heating is carried out separately using a water source heat pump; Mode 4 means heating is carried out using a low-efficiency air heat pump that uses a water source heat pump plus a wind-warm PTC to heat the air around the evaporator; Mode 5 means heating is carried out using a low-efficiency air heat pump that directly uses a wind-warm PTC to heat the air around the evaporator.

3. The method for selecting a heat source for battery heating using a heat pump system according to claim 2, characterized in that: The heating method adopted in Mode 1 needs to use EXV-OHX to realize the heat exchange between the refrigerant and the external air; the heating method adopted in Mode 2 needs to use EXV-OHX to realize the heat exchange between the refrigerant and the external air and EXV-LCC to realize the heat exchange between the refrigerant and the motor coolant; the heating methods adopted in Mode 3 and Mode 4 need to use EXV-LCC to realize the heat exchange between the refrigerant and the motor coolant; Mode 5 directly realizes the heat exchange between the refrigerant and the hot air through an uncontrolled evaporator.

4. The method for selecting a heat source for battery heating using a heat pump system according to claim 1, characterized in that: If EXV-OHX is not failed, judge the fault state of the ambient temperature sensor. When the ambient temperature sensor fails, the ambient temperature value is replaced by the evaporator temperature value; if not failed, the ambient temperature value is directly obtained through the ambient temperature sensor.

5. The method for selecting a heat source for battery heating using a heat pump system according to claim 1, characterized in that: If EXV-LCC fails, when the ambient temperature ≥ T2, heating is carried out using Mode 1; if the ambient temperature < T2, under the discharging condition, no battery heating is carried out; under the charging condition, if the battery pack is in the OA closed-loop stage, Mode 5 is used to carry out low-temperature heating of the battery, otherwise, no heating is carried out.

6. The method for selecting a heat source for battery heating using a heat pump system according to claim 1, characterized in that: The VCU determines that the power battery heating operation can be executed. Specifically, the VCU receives the power battery temperature and its own fault state sent by the LBC controller through the CAN bus. If the lowest temperature of the power battery single cell is below the heating temperature threshold, it is determined that the power battery has a heating requirement.

7. The method for selecting a heat source for battery heating using a heat pump system according to claim 6, characterized in that: Judge whether the self-state of the power battery meets the heating conditions according to the battery fault state, battery water pump fault state, compressor fault state and the refrigerant amount in the pipeline.

8. The method for selecting a heat source for battery heating using a heat pump system according to claim 7, characterized in that: If the received battery fault state shows that it has no fault itself, the battery water pump can normally transport the coolant, the compressor can normally operate to transport the refrigerant, and the refrigerant amount in the pipeline is sufficient for heat exchange, then heating is allowed and the power battery heating operation is executed. If the above conditions are not met, the battery heating operation is not executed and the system reports a fault.

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