Method and apparatus for implementing electric vehicle charging and discharging function

Abstract

The application relates to power battery technology, in particular to a method for realizing the charging and discharging function of an electric vehicle, a vehicle controller for implementing the method and a vehicle-mounted charging and discharging unit. The method for realizing the charging and discharging function of an electric vehicle according to an aspect of the application comprises the following steps: after the charging and discharging unit is physically connected with the charging port of the electric vehicle, the charging and discharging unit sends a discharging request message to the vehicle control unit in response to a discharging command; the vehicle control unit determines whether the battery management system is allowed to operate in a discharging mode in response to the discharging request message; if it is determined that the operation in the discharging mode is allowed, the vehicle control unit returns an acknowledgement message to the charging and discharging unit and instructs the battery management system to enter the discharging mode; and a first communication process between the charging and discharging unit and the vehicle control unit or the battery management system is performed to enable the power battery to supply power to external equipment.

Description

Technical Field

[0001] This application relates to power battery technology, and in particular to a method for realizing the charging and discharging function of an electric vehicle, a vehicle controller for implementing the above method, and a charging and discharging unit. Background Technology

[0002] With the increasing popularity of smart electric vehicles, usage scenarios are becoming more diverse. In scenarios such as self-driving camping sites and car washes, there is a significant demand for standard 220V power supplies. On the other hand, although electric vehicles are typically equipped with 350V-800V DC high-voltage batteries, they cannot provide 220V AC power to external devices through the charging port. Therefore, achieving bidirectional power output capability in electric vehicles is urgently needed. Summary of the Invention

[0003] One object of this application is to provide a method for realizing the charging and discharging function of an electric vehicle, a vehicle controller for implementing the above method, and an on-board charging and discharging unit, which can realize the bidirectional output function of electrical energy in a simple and reliable manner.

[0004] According to one aspect of this application, a method for implementing the charging and discharging function of an electric vehicle is provided. The electric vehicle includes a vehicle control unit, a power battery, and a battery management system. The method includes the following steps:

[0005] Once the charging and discharging unit has completed the physical connection with the charging port of the electric vehicle, in response to the discharge command, the on-board charging and discharging unit sends a discharge request message to the vehicle control unit.

[0006] In response to the discharge request message, the vehicle control unit determines whether to allow the battery management system to operate in discharge mode;

[0007] If it is determined that operation in the discharge mode is permitted, the vehicle control unit returns an acknowledgment message to the charging and discharging unit and instructs the battery management system to enter the discharge mode.

[0008] The first communication process between the charging / discharging unit and the vehicle control unit or the battery management system is executed to enable the power battery to supply power to the external device.

[0009] Optionally, the above method further includes:

[0010] If the vehicle control unit does not receive the discharge request message within a set time interval from the completion of the physical connection, the second communication process between the charging / discharging unit and the vehicle control unit or the battery management system is executed to enable the external device to charge the power battery.

[0011] Optionally, in the above method, the vehicle control unit determines whether to allow the battery management system to operate in discharge mode based on the SOC value of the power battery.

[0012] Optionally, in the above method, the second communication process is based on the DC charging communication protocol GB / T27930.

[0013] Optionally, in the above method, the first communication process is based on the DC charging communication protocol GB / T27930, which includes at least the following modifications:

[0014] For CHM messages, the vehicle control unit or the battery management system only responds to the event of receiving the CHM message without considering the content of the CHM message, and sends a BHM message to the on-board charging and discharging unit.

[0015] For the BHM message, the maximum allowable charging voltage is replaced with the voltage value of the power battery;

[0016] For BCP messages, replace the maximum allowable charging current with the maximum allowable discharge current of the power battery;

[0017] For CML messages, replace the charger's maximum output voltage and maximum output current with the on-board charging and discharging unit's maximum allowable voltage and maximum allowable current.

[0018] For BCL messages, replace the voltage and current requirements with the real-time voltage and maximum allowable discharge current of the power battery.

[0019] For BCS messages, the on-board charging and discharging unit only responds to the event of receiving the BCS message without considering the content of the BCS message, and sends a CSS message to the vehicle control unit or battery management system.

[0020] Optionally, in the above method, while instructing the battery management system to enter the discharge mode, the vehicle control unit also adjusts the energy management strategy and thermal management strategy associated with the power battery to adapt to the discharge mode.

[0021] According to another aspect of this application, a vehicle control unit is provided, comprising:

[0022] Memory;

[0023] A processor coupled to the memory;

[0024] and a computer program stored in the memory, which is executed by the processor to perform the following operations:

[0025] In response to a discharge request message from the charge / discharge unit, determine whether the battery management system is allowed to operate in discharge mode;

[0026] If it is determined that entering the discharge mode is allowed, an acknowledgment message is returned to the charging and discharging unit, and the battery management system is instructed to enter the discharge mode.

[0027] The power battery is discharged by interacting with the charging and discharging unit to achieve a first communication process.

[0028] Optionally, in the aforementioned vehicle control unit, the processor is further configured to:

[0029] If the discharge request message is not received from the charging and discharging unit within a set time interval after the charging port of the electric vehicle completes physical connection with the charging and discharging unit, then the external device interacts with the charging and discharging unit to implement the second communication process, thereby enabling the external device to charge the power battery.

[0030] Optionally, in the aforementioned vehicle control unit, it is determined whether the battery management system is allowed to operate in discharge mode based on the SOC value of the power battery.

[0031] Optionally, in the above-mentioned vehicle control unit, the second communication process is specified by the DC charging communication protocol GB / T27930.

[0032] Optionally, in the above-mentioned vehicle control unit, the first communication process is implemented using the DC charging communication protocol GB / T27930, which includes at least the following modifications:

[0033] For CHM messages, the vehicle control unit only responds to the event of receiving the CHM message without considering the content of the CHM message, and sends a BHM message to the charging and discharging unit.

[0034] For the BHM message, replace the maximum allowable charging voltage with the voltage value of the power battery;

[0035] For BCP messages, replace the maximum allowable charging current with the maximum allowable discharge current of the power battery;

[0036] For CML messages, replace the charger's maximum output voltage and maximum output current with the charging and discharging unit's maximum allowable voltage and maximum allowable current.

[0037] For BCL messages, replace the voltage and current requirements with the real-time voltage and maximum allowable discharge current of the power battery.

[0038] For BCS messages, the charging / discharging unit only responds to the event of receiving the BCS message without considering the content of the BCS message, and sends a CSS message to the vehicle control unit or battery management system.

[0039] Optionally, in the aforementioned vehicle control unit, the processor is configured to, while instructing the battery management system to enter the discharge mode, also adjust the energy management strategy and thermal management strategy associated with the power battery to adapt to the discharge mode.

[0040] According to another aspect of this application, an electric vehicle is provided, including the vehicle control unit as described above.

[0041] According to another aspect of this application, a charging and discharging unit is provided, comprising:

[0042] port;

[0043] The controller is configured to perform the following operations:

[0044] In response to the user's discharge command, a discharge request message is sent to the vehicle control unit;

[0045] If an acknowledgment message is received from the vehicle control unit, the system interacts with the vehicle control unit or the battery management system to execute a first communication procedure, thereby enabling the power battery to supply power to the external device.

[0046] Optionally, in the above-described charging and discharging unit, the controller is further configured to:

[0047] Once a physical connection is established with the port of the electric vehicle, a wake-up signal is sent to the vehicle control unit.

[0048] Optionally, in the above-described charging and discharging unit, the controller is further configured to:

[0049] The external device interacts with the vehicle control unit to implement a second communication process, thereby enabling the external device to charge the power battery.

[0050] Optionally, in the above-mentioned charging and discharging unit, the charging and discharging unit is a bidirectional charging module.

[0051] In some embodiments, since the handshake judgment and CHM message judgment in the discharge handshake process are processed in parallel, time delays in the charging scenario can be avoided. Furthermore, the sending of the acknowledgment message is triggered by the receipt of the discharge request message, thus not affecting the communication load during normal charging and preventing misidentification of the charging station. Attached Figure Description

[0052] The above and / or other aspects and advantages of this application will become clearer and more readily understood from the following description taken in conjunction with the accompanying drawings, in which the same or similar elements are denoted by the same reference numerals. The drawings include:

[0053] Figure 1 This is a schematic block diagram of an electric vehicle according to some embodiments of this application.

[0054] Figure 2 for Figure 1 The diagram shows a schematic block diagram of the charging and discharging unit.

[0055] Figure 3 for Figure 1 The diagram shows a schematic block diagram of the vehicle control unit.

[0056] Figure 4 This is a flowchart of a method for implementing the charging and discharging function of an electric vehicle according to some other embodiments of this application. Detailed Implementation

[0057] The present application will now be described more fully with reference to the accompanying drawings, which illustrate exemplary embodiments thereof. However, the present application may be implemented in various forms and should not be construed as being limited to the embodiments given herein. The foregoing embodiments are intended to make the disclosure herein complete and thorough, so as to more fully convey the scope of protection of the present application to those skilled in the art.

[0058] In this specification, terms such as “comprising” and “including” indicate that, in addition to having the units and steps that are directly and explicitly stated in the specification and claims, the technical solution of this application does not exclude the presence of other units and steps that are not directly or explicitly stated.

[0059] Unless otherwise specified, terms such as “first” and “second” do not indicate the order of units in terms of time, space, size, etc., but are merely used to distinguish between units.

[0060] Figure 1 This is a schematic block diagram of an electric vehicle according to some embodiments of this application.

[0061] like Figure 1 As shown, the electric vehicle 10 includes a vehicle control unit 110, a battery management system 120, and a power battery 130. The charging and discharging unit 30 is an interface device between the electric vehicle and external devices, and it can communicate with the vehicle control unit 110; in addition, external devices 20 (e.g., chargers) can charge the power battery 130 through the charging and discharging unit 30, or the power battery 130 can supply power to external devices 20 (e.g., electrical appliances) through the charging and discharging unit 30.

[0062] The charging / discharging unit 30 may be, for example, a bidirectional charging module. In some embodiments, the charging / discharging unit 30 is configured to send a discharge request message to the vehicle control unit 110 when there is a discharge demand, and after receiving an acknowledgment message from the vehicle control unit 110, interact with the vehicle control unit 110 to execute a first communication process, thereby enabling the power battery 130 to supply power to the external device 20. In one example, when the charging / discharging unit completes a physical connection with the charging port of the electric vehicle and receives a discharge command (e.g., a user presses a discharge operation button set on the charging / discharging unit), the charging / discharging unit sends a discharge request message to the vehicle control unit. On the other hand, when there is a charging demand, the charging / discharging unit 30 will interact with the vehicle control unit 110 to execute a second communication process, thereby enabling the external device 20 to charge the power battery 130. Details regarding the first and second communication processes will be further described below.

[0063] Figure 2 for Figure 1 A schematic block diagram of the charging / discharging unit 30 is shown. Figure 2 As shown, the charging / discharging unit 30 may include ports 311A ​​and 311B, a power converter 312, and a controller 313. Port 311A ​​is the electrical interface between the charging / discharging unit and an external device, and port 311B is the electrical interface between the charging / discharging unit and the power battery. The power converter 312 has bidirectional conversion capability and includes, for example, a first conversion unit 312A and a second conversion unit 312B. Under the control of the controller 313, in discharge mode, the first conversion unit 312A converts the DC power input from the power battery via port 311B into AC power output to the external device 20 via port 311A, and in charging mode, the second conversion unit 312B converts the AC power input from the external device via port 311A ​​into DC power output to the power battery 130 via port 311B. The controller 313 may be configured to perform first and second communication processes with the vehicle controller 110 and to control the operation of the power converter 312.

[0064] In accordance with the operation of the aforementioned charging and discharging unit, the vehicle control unit 110 is configured to, in response to a discharge request message from the charging and discharging unit 30, determine whether the battery management system 120 is permitted to operate in discharge mode. Upon determining that entry into discharge mode is permitted, the vehicle control unit 110 returns an acknowledgment message to the charging and discharging unit 30 and instructs the battery management system 120 to enter discharge mode. Subsequently, the vehicle control unit 110 interacts with the charging and discharging unit 30 to implement a first communication process, which is used to discharge the power battery 130 (i.e., supply power to the external device 20). The vehicle control unit 110 is also configured to interact with the on-board charging and discharging unit 30 to implement a second communication process when the external device 20 is a charging device, thereby enabling the external device 20 to charge the power battery 130.

[0065] Optionally, the vehicle control unit 110 may determine whether the external device 20 is a charging device by: if no discharge request message is received from the charging / discharging unit 30 within a set time interval (e.g., 3 seconds) after the charging port of the electric vehicle completes physical connection with the charging / discharging unit 30, then the external device 20 is determined to be a charging device. Accordingly, in order for the vehicle control unit 110 to determine the moment of completion of physical connection, the charging / discharging unit 30 may send a wake-up signal to the vehicle control unit 110 after completing physical connection with the charging port of the electric vehicle.

[0066] Alternatively, the vehicle control unit 110 may determine whether to allow the battery management system 120 to operate in discharge mode based on the SOC value of the power battery 130. For example, the current SOC value of the power battery may be compared with a set TH_SOC; if the former is greater than the latter, it is determined that operation in discharge mode is allowed; otherwise, it is determined that the battery management system is prohibited from entering discharge mode.

[0067] Alternatively, the vehicle control unit 110 may be configured to adjust the energy management strategy and thermal management strategy associated with the power battery 130 to adapt to the discharge mode while instructing the battery management system 120 to enter the discharge mode.

[0068] Figure 3 for Figure 1 The diagram shows a schematic block diagram of the vehicle control unit. Figure 3 As shown, the vehicle control unit 110 includes a memory 111 (such as a non-volatile memory like flash memory, ROM, hard disk drive, disk, optical disk, etc.), a processor 112, and a computer program 113.

[0069] Memory 111 stores a computer program 113 that can be executed by processor 112. Processor 112 is configured to run the computer program 113 stored in memory 111. By running the computer program 113, various functions of the vehicle control unit can be implemented, such as, but not limited to, the functions of the vehicle control unit 110 described above.

[0070] In some embodiments, the second communication process is implemented using an existing charging protocol (e.g., the DC charging communication protocol GB / T27930), and the first communication process is implemented by making minor modifications to the existing charging protocol. Furthermore, before the communication process based on the existing protocol is initiated, a discharge handshake process is first performed between the charging / discharging unit and the vehicle control unit. Specifically, the discharge handshake process is initiated by the charging / discharging unit; that is, when the charging / discharging unit receives a user's discharge command, it sends the aforementioned discharge request message to the vehicle control unit. Subsequently, in response to the discharge request message, the vehicle control unit determines whether the battery management system is allowed to operate in discharge mode based on the vehicle status (e.g., the SOC value of the power battery). If allowed, the vehicle control unit sends an acknowledgment message to the charging / discharging unit and adjusts the energy management strategy and thermal management strategy associated with the power battery to adapt to the discharge mode. When the charging / discharging unit receives the acknowledgment message, it initiates the first communication process. On the other hand, in the aforementioned discharge handshake process, if the vehicle control unit does not receive a discharge request message within a set time interval from the time the charging / discharging unit completes physical connection with the electric vehicle's port, it will execute the second communication process.

[0071] It should be noted that, although in the above description, the first and second communication processes are performed between the charging / discharging unit and the vehicle control unit, in some other embodiments, the first and second communication processes may also be performed between the charging / discharging unit and the battery management system.

[0072] When the existing charging protocol used is the DC charging communication protocol GB / T27930, the following modifications can be made to the DC charging communication protocol GB / T27930 to implement the first communication process:

[0073] ●In the existing DC charging communication protocol GB / T27930, after the charger and electric vehicle are physically connected and powered on, and the voltage detection is normal, the charger periodically sends CHM messages to the battery management system to determine whether the handshake between the two parties is normal. When implementing the first communication process, the protocol can be modified so that the vehicle control unit or battery management system only responds to the receipt of a CHM message without considering its content, and sends a BHM message to the charging / discharging unit.

[0074] ● When implementing the first communication process, the maximum allowable charging voltage in the BHM message can be replaced with the voltage value of the power battery.

[0075] ●In the existing DC charging communication protocol GB / T27930, the BCP message is a message sent by the vehicle control unit or battery management system to the charger during the charging parameter configuration phase to report the charging parameters of the power battery. During the first communication process, a BCP message can be sent to the charging / discharging unit, where the maximum permissible charging current is replaced with the maximum permissible discharging current of the power battery.

[0076] ●In the existing DC charging communication protocol GB / T27930, the CML message is a message sent by the charger to the vehicle control unit or battery management system to indicate the charger's maximum output capacity. During the first communication process, a CML message can be sent to the vehicle control unit or battery management system, where the charger's maximum output voltage and maximum output current are replaced with the maximum permissible voltage and maximum permissible current of the charging / discharging unit.

[0077] ●In the existing DC charging communication protocol GB / T27930, BCL messages are sent by the vehicle control unit or battery management system to the charger, which enables the charger to adjust the charging voltage and charging current according to the battery charging demand, ensuring that the charging process proceeds normally.

[0078] When implementing the first communication process, a BCL message can be sent to the charging and discharging unit. The voltage and current requirements in this message are replaced with the real-time voltage and maximum allowable discharge current of the power battery.

[0079] ●In the existing DC charging communication protocol GB / T27930, the BCS message is sent by the vehicle control unit or battery management system to the charger, enabling the charger to monitor the charging status of the battery pack, such as charging voltage and charging current, during the charging process. When implementing the first communication process, the protocol can be modified so that the charging / discharging unit only responds to the receipt of the BCS message without considering its content, and sends a CSS message to the vehicle control unit or battery management system.

[0080] In some embodiments, since the handshake judgment and CHM message judgment in the discharge handshake process are processed in parallel, time delays in the charging scenario can be avoided. Furthermore, the sending of the acknowledgment message is triggered by the receipt of the discharge request message, thus not affecting the communication load during normal charging and preventing misidentification of the charging station.

[0081] Figure 4 This is a flowchart illustrating a method for implementing a charging and discharging function for an electric vehicle according to other embodiments of this application. The following description is for illustrative purposes only. Figure 1 The electric vehicle shown is used as an example to illustrate this point.

[0082] See Figure 4The process shown begins at step 410. In this step, after the charging / discharging unit 30 completes the physical connection with the electric vehicle's port and receives a discharge command, the charging / discharging unit 30 sends a discharge request message to the vehicle control unit 110 and sends a wake-up signal to the vehicle control unit 110 to bring the vehicle control unit 110 from the sleep state to the ready state; on the other hand, if the external device is a charging device, the charging / discharging unit 30 only sends a wake-up signal to the vehicle control unit 110. Optionally, the discharge request message can be sent repeatedly multiple times.

[0083] Then proceed to step 420. In this step, the vehicle control unit 110 determines whether a discharge request message has been received from the charging and discharging unit 30 within a set time interval since the physical connection between the electric vehicle's port and the charging and discharging unit 30 was completed (i.e., within a set time interval since the wake-up signal was received). If a discharge request message is received, proceed to step 430; otherwise, proceed to step 440.

[0084] In step 430, the vehicle control unit 110 determines whether the battery management system is allowed to operate in discharge mode. If allowed, the process proceeds to step 450; otherwise, the process ends. Optionally, the vehicle control unit 110 may determine whether the battery management system 120 is allowed to operate in discharge mode based on the SOC value of the power battery 130.

[0085] In step 440, a second communication process is executed between the charging / discharging unit 30 and the vehicle control unit 110 or the battery management system 120 to enable the external device (charger) 20 to charge the power battery 130. Optionally, the second communication process may be based on the DC charging communication protocol GB / T27930.

[0086] In step 450, the vehicle control unit 110 returns an acknowledgment message to the charging and discharging unit 30 and instructs the battery management system 120 to enter the discharge mode.

[0087] After step 450, Figure 4 The illustrated process proceeds to step 460, where a first communication procedure is executed between the charging / discharging unit 30 and the vehicle control unit 110 or the battery management system 120 to enable the power battery 130 to supply power to the external device 20. Optionally, the first communication procedure may be based on a modified DC charging communication protocol GB / T27930. Various modifications to the DC charging communication protocol GB / T27930 for implementing the first communication procedure have been described in detail above and will not be repeated here.

[0088] Those skilled in the art will understand that the various illustrative logic blocks, modules, circuits, and algorithm steps described herein can be implemented as electronic hardware, computer software, or a combination of both.

[0089] To demonstrate the interchangeability between hardware and software, various illustrative components, blocks, modules, circuits, and steps have been generally described above according to their functionality. Whether such functionality is implemented in hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art can implement the described functionality in varying ways for specific applications; however, such implementation decisions should not be construed as departing from the scope of this application.

[0090] Although only some specific embodiments of this application have been described, those skilled in the art will understand that this application can be implemented in many other forms without departing from its spirit and scope. Therefore, the examples and embodiments shown are to be considered illustrative rather than restrictive, and various modifications and substitutions may be made without departing from the spirit and scope of this application as defined by the appended claims.

[0091] The embodiments and examples presented herein are provided to best illustrate embodiments according to the present technology and its particular applications, thereby enabling those skilled in the art to implement and use the application. However, those skilled in the art will understand that the above description and examples are provided for ease of illustration and example only. The descriptions presented are not intended to cover all aspects of the application or to limit the application to the precise forms disclosed.

Claims

1. A method for realizing the charging and discharging function of an electric vehicle, the electric vehicle including a vehicle control unit, a power battery, and a battery management system, the method comprising the following steps: Once the charging and discharging unit has completed its physical connection with the charging port of the electric vehicle, in response to a discharge command, the charging and discharging unit sends a discharge request message to the vehicle control unit. In response to the discharge request message, the vehicle control unit determines whether to allow the battery management system to operate in discharge mode; If it is determined that operation in the discharge mode is permitted, the vehicle control unit returns an acknowledgment message to the charging and discharging unit and instructs the battery management system to enter the discharge mode. The first communication process between the charging / discharging unit and the vehicle control unit or the battery management system is executed to enable the power battery to supply power to external devices. The first communication process is based on the DC charging communication protocol GB / T 27930, which includes at least the following modifications: For CHM messages, the vehicle control unit or the battery management system only responds to the event of receiving the CHM message without considering the content of the CHM message, and sends a BHM message to the charging and discharging unit. For the BHM message, the maximum allowable charging voltage is replaced with the voltage value of the power battery; For the BCP message sent to the charging and discharging unit, the maximum allowable charging current is replaced with the maximum allowable discharging current of the power battery; For CML messages sent to the vehicle control unit or the battery management system, the maximum output voltage and maximum output current of the charger are replaced with the maximum allowable voltage and maximum allowable current of the charging and discharging unit. For the BCL message sent to the charging and discharging unit, the voltage requirement and current requirement are replaced with the real-time voltage and maximum allowable discharge current of the power battery. For BCS messages, the charging / discharging unit only responds to the event of receiving the BCS message without considering the content of the BCS message, and sends a CSS message to the vehicle control unit or battery management system.

2. The method of claim 1, further comprising: If the vehicle control unit does not receive the discharge request message within a set time interval from the completion of the physical connection, the second communication process between the charging / discharging unit and the vehicle control unit or the battery management system is executed to enable the external device to charge the power battery.

3. The method as described in claim 1 or 2, wherein, The vehicle control unit determines whether to allow the battery management system to operate in discharge mode based on the SOC value of the power battery.

4. The method of claim 2, wherein, The second communication process is based on the DC charging communication protocol GB / T27930.

5. The method as described in claim 1 or 2, wherein, While instructing the battery management system to enter the discharge mode, the vehicle control unit also adjusts the energy management strategy and thermal management strategy associated with the power battery to adapt to the discharge mode.

6. An electric vehicle, comprising a vehicle control unit, a power battery, and a battery management system. in, The vehicle control unit is configured as follows: In response to a discharge request message from the charge / discharge unit, determine whether the battery management system is allowed to operate in discharge mode; If it is determined that entering the discharge mode is allowed, an acknowledgment message is returned to the charging and discharging unit, and the battery management system is instructed to enter the discharge mode. The power battery is discharged by interacting with the charging and discharging unit to achieve the first communication process. The charging and discharging unit is configured as follows: Once the charging / discharging unit has completed its physical connection with the charging port of the electric vehicle, it sends a discharge request message to the vehicle control unit in response to the discharge command. If an acknowledgment message is received from the vehicle control unit, the system interacts with the vehicle control unit or the battery management system to execute a first communication procedure, thereby enabling the power battery to supply power to external devices. The first communication process is based on the DC charging communication protocol GB / T 27930, which includes at least the following modifications: For CHM messages, the vehicle control unit or the battery management system only responds to the event of receiving the CHM message without considering the content of the CHM message, and sends a BHM message to the charging and discharging unit. For the BHM message, the maximum allowable charging voltage is replaced with the voltage value of the power battery; For the BCP message sent to the charging and discharging unit, the maximum allowable charging current is replaced with the maximum allowable discharging current of the power battery; For CML messages sent to the vehicle control unit or the battery management system, the maximum output voltage and maximum output current of the charger are replaced with the maximum allowable voltage and maximum allowable current of the charging and discharging unit. For the BCL message sent to the charging and discharging unit, the voltage requirement and current requirement are replaced with the real-time voltage and maximum allowable discharge current of the power battery. For BCS messages, the charging / discharging unit only responds to the event of receiving the BCS message without considering the content of the BCS message, and sends a CSS message to the vehicle control unit or battery management system.

7. The electric vehicle as claimed in claim 6, wherein, The vehicle control unit is also configured to: If no discharge request message is received within a set time interval from the time the port of the charging / discharging unit is physically connected to the external device, the external device will interact with the charging / discharging unit to implement a second communication process, thereby enabling the external device to charge the power battery.

8. The electric vehicle as claimed in claim 6 or 7, wherein, Whether the battery management system is allowed to operate in discharge mode is determined based on the SOC value of the power battery.

9. The electric vehicle as claimed in claim 6 or 7, wherein, The charging / discharging unit is further configured to: When the external device connected to the port of the charging and discharging unit is a charging device, it interacts with the vehicle control unit or battery management system to execute a second communication process, thereby enabling the external device to charge the power battery.

10. The electric vehicle as claimed in claim 9, wherein, The charging and discharging unit is a bidirectional charging module.

11. The electric vehicle as claimed in claim 7, wherein, The second communication process is specified by the DC charging communication protocol GB / T27930.

12. The electric vehicle as claimed in claim 6 or 7, wherein, The vehicle control unit is configured to, while instructing the battery management system to enter the discharge mode, also adjust the energy management strategy and thermal management strategy associated with the power battery to adapt to the discharge mode.

13. A vehicle control unit, comprising: Memory; A processor coupled to the memory; and a computer program stored in the memory, which is executed by the processor to perform the following operations: In response to a discharge request message from the charge / discharge unit, determine whether the battery management system is allowed to operate in discharge mode; If it is determined that entering the discharge mode is allowed, an acknowledgment message is returned to the charging and discharging unit, and the battery management system is instructed to enter the discharge mode. Interacting with the charging and discharging unit to achieve the first communication process, thereby discharging the power battery. The first communication process is based on the DC charging communication protocol GB / T 27930, which includes at least the following modifications: For CHM messages, the vehicle control unit or the battery management system only responds to the event of receiving the CHM message without considering the content of the CHM message, and sends a BHM message to the charging and discharging unit. For the BHM message, the maximum allowable charging voltage is replaced with the voltage value of the power battery; For the BCP message sent to the charging and discharging unit, the maximum allowable charging current is replaced with the maximum allowable discharging current of the power battery; For CML messages sent to the vehicle control unit or the battery management system, the maximum output voltage and maximum output current of the charger are replaced with the maximum allowable voltage and maximum allowable current of the charging and discharging unit. For the BCL message sent to the charging and discharging unit, the voltage requirement and current requirement are replaced with the real-time voltage and maximum allowable discharge current of the power battery. For BCS messages, the charging / discharging unit only responds to the event of receiving the BCS message without considering the content of the BCS message, and sends a CSS message to the vehicle control unit or battery management system.

14. A charging / discharging unit, comprising: port; The controller is configured to perform the following operations: Once the charging and discharging unit has completed the physical connection with the charging port of the electric vehicle, it sends a discharge request message to the vehicle control unit in response to the discharge command. If an acknowledgment message is received from the vehicle control unit, the system interacts with the vehicle control unit or the battery management system to execute a first communication procedure, thereby enabling the power battery to supply power to external devices. The first communication process is based on the DC charging communication protocol GB / T 27930, which includes at least the following modifications: For CHM messages, the vehicle control unit or the battery management system only responds to the event of receiving the CHM message without considering the content of the CHM message, and sends a BHM message to the charging and discharging unit. For the BHM message, the maximum allowable charging voltage is replaced with the voltage value of the power battery; For the BCP message sent to the charging and discharging unit, the maximum allowable charging current is replaced with the maximum allowable discharging current of the power battery; For CML messages sent to the vehicle control unit or the battery management system, the maximum output voltage and maximum output current of the charger are replaced with the maximum allowable voltage and maximum allowable current of the charging and discharging unit. For the BCL message sent to the charging and discharging unit, the voltage requirement and current requirement are replaced with the real-time voltage and maximum allowable discharge current of the power battery. For BCS messages, the charging / discharging unit only responds to the event of receiving the BCS message without considering the content of the BCS message, and sends a CSS message to the vehicle control unit or battery management system.

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