Method and control unit for controlling a charging process of an electric vehicle

Abstract

The invention relates to a method for controlling a charging process of an electric vehicle (1), comprising the following steps: I) communication (S1) between the electric vehicle (1) and a charging device (7) connected to the electric vehicle (1) by means of a charging cable (6), as to whether the charging device (7) is a DC charging device or an AC charging device; II) requesting and measuring (S2) a charging voltage of the charging device (7) by the electric vehicle (1); III) checking (S3) whether the charging voltage provided by the charging device (7) is greater than or equal to a threshold value, wherein the threshold value is characteristic of a DC charging voltage; IV) preventing (S4) a charging process if the communication (S1) has shown that the charging device (7) is a DC charging device and, upon checking (S3), it has been determined that the charging voltage provided by the charging device (7) is not greater than or equal to a threshold value, and V) starting (S5) a charging process if no prevention of a charging process is brought about in step V). The invention further relates to a control unit (8), to an electric vehicle (1), and to a computer program product for carrying out the method.

Description

[0001] 24-1286 1

[0002] Method and control unit for controlling the charging process of an electric vehicle

[0003] The invention relates to a method for controlling the charging process of an electric vehicle and a control unit for carrying out the method. Furthermore, the invention relates to an electric vehicle with the control unit and a computer program for executing the method.

[0004] Charging an electric vehicle can be done using direct current (DC) or alternating current (AC). For the purposes of this text, an electric vehicle is defined as a vehicle that is at least partially electrically powered, in particular a battery electric vehicle (BEV) or a plug-in hybrid electric vehicle (PHEV). Battery electric vehicles, and to some extent plug-in hybrid electric vehicles, can be equipped with in-vehicle charging electronics and a charging socket that allows for both AC and DC charging. In this case, the vehicle's control unit, which manages the charging process, must be able to detect whether the charging socket is connected to an AC charging device, such as a public charging station or a wallbox, or to a DC charging device, such as a fast charger.This allows the control unit to manage the vehicle's internal charging electronics, such as electrical converters, for the charging process. Determining whether the charging device connected to the electric vehicle is an AC or DC charger can be achieved through communication between the electric vehicle and the charger, particularly via a signal line in the charging cable.

[0005] If the communication between the electric vehicle and the connected charging device regarding the type of voltage supplied by the charging device is faulty, there is a risk of damage to components of the charging electronics in the electric vehicle and / or the electronics in the charging device. For example, if the vehicle's internal charging electronics have been configured by the control unit for DC charging, while the electric vehicle is actually connected to an AC charging device, electronic components in the electric vehicle or the charging station may be damaged. This risk is particularly high if the connections for AC and DC charging are not physically separated in the charging socket and the corresponding charging plug. 24-1286 2

[0006] It is an object of the invention to provide a method and a control unit for controlling a charging process of an electric vehicle that enables reliable detection of the type of voltage provided by a charging device.

[0007] This problem is solved by a method and a control unit according to the independent claims. Advantageous embodiments and further developments of the invention are described in the dependent claims.

[0008] In this process, an electric vehicle is connected to a charging device via a charging cable. The charging device could be, for example, a charging station on public or private property or a wallbox. The process uses communication between the electric vehicle and the charging device to determine whether it is a DC or AC charging device. This communication can occur, for example, via at least one signal conductor in the charging cable. In a subsequent step, also known as "pre-charging," the electric vehicle requests and measures the charging voltage from the charging device. The process then checks whether the charging voltage provided by the charging device is greater than or equal to a threshold value characteristic of a DC charging voltage. This threshold value is, for example, at least 400 V.A charging process is prevented if communication between the electric vehicle and the charging device indicates that the charging device is a DC charger and a check of the charging voltage provided by the charging device reveals that the charging voltage is not at least the threshold value, for example, at least 400 V. Preventing the charging process can, in particular, mean that charging contactors in the electric vehicle are not opened. A charging process will only be initiated in a subsequent step if no prevention of the charging process occurred in the previous step.

[0009] The invention is based in particular on the considerations set out below: When charging an electric vehicle, communication takes place between the electric vehicle and the charging device before the charging process starts, determining whether the charging device is an AC or DC charging device. In the event of a communication error, it could happen that a DC charging device is incorrectly detected, even though an AC charging device is actually connected to the electric vehicle. The risk of such a communication error can occur, for example, if the communication signal is not robust and / or cannot be assigned an ASIL (Automotive Safety Integrity Level) integrity rating.In the so-called pre-charge process, the electric vehicle requests a charging voltage from the charging device, which is then checked, for example, with a voltage sensor, before the vehicle's charging contactors open, thus enabling the current flow for the charging process. When checking the charging voltage, there is a risk that it will not be possible to detect whether it is an AC or DC voltage. For example, the voltage sensor may not be able to reliably distinguish between AC and DC charging voltages due to its sampling frequency or a technical fault, particularly not according to ASIL requirements. If the aforementioned potential faults occur together, there is a risk that an AC charging device connected to the electric vehicle will be subjected to a DC voltage. This could lead to damage to the AC charging device or to components connected to it.Such a misidentification of the charging device's voltage type is prevented, according to the principle proposed here, in particular by checking, before the actual charging process, especially during the so-called pre-charge process before the charging contactors close, whether the charging device's charging voltage is at least the threshold value characteristic of a DC charging voltage, such as 400 V. This check is based on the consideration that the voltage amplitude during AC charging, according to current international standards, is always significantly less than 400 V, while DC charging uses charging voltages of at least 400 V or higher, for example, 400 V or 800 V. The threshold value characteristic of a DC charging voltage is therefore higher than the charging voltage typically used for AC charging (for example, according to a national standard). A charging voltage greater than or equal to the threshold of, for example, 400 V, would therefore be incorrect.A voltage of at least 400 V is therefore a reliable indicator that a DC charger is connected to the electric vehicle. If, due to a communication error, a DC charger is incorrectly detected when in fact an AC charger is connected, checking the charging voltage according to the principle proposed here will show that the voltage does not reach at least the threshold value of, for example, 400 V, because the AC charger cannot provide such a high voltage. In this case, the charging process is prevented; specifically, the charging contactors of the electric vehicle do not open to allow charging current to flow to the vehicle. This reliably prevents a DC charging process from initiating at the AC charger, which could otherwise damage components of the charging electronics of the charger and / or the electric vehicle.

[0010] According to one embodiment, the charging device is an AC charging device. As explained above, the method is particularly suitable for protecting an AC charging device from a DC charging process being initiated by an electric vehicle connected to the AC charging device.

[0011] According to one embodiment, the charging cable has a charging plug that is connected to an electric vehicle's charging socket via an adapter. Such an adapter can be used to connect a charging plug to a charging socket that conforms to a different standard, for example, a different country-specific standard and / or a standard that has changed over time. Since the risk of faulty communication between the electric vehicle and the charging device is increased when using an adapter, the method described here is particularly advantageous when using an adapter in order to prevent faulty charging processes.

[0012] According to one embodiment, the adapter is configured to connect the charging plug to a DC port of the charging socket. When using an adapter for the DC port of the charging socket, there is a risk that an AC charging device could be accidentally connected to the DC port. If the charging socket in use allows both AC and DC charging via the same connection pins, there would be a risk that a DC charging process would be initiated on the AC charging device. This is advantageously prevented in the method described herein by checking the charging voltage to a minimum threshold value of, for example, 400 V, thus reducing the risk of damage to electronic components due to the incorrect use of a DC charging adapter in combination with an AC charging device.

[0013] In one configuration of the procedure, an error message is issued to the user of the electric vehicle if the charging process is prevented. In this case, the error message can, for example, be sent to a user interface in the vehicle and / or to a device identified by 24-1286 5.

[0014] The user's app may be used. The error message might, for example, prompt the user to check the electric vehicle's connection to the charging device. Specifically, the user might be asked to check whether a DC charging adapter was accidentally used on a charging cable plug when the cable is connected to an AC charging device.

[0015] The invention further relates to a control unit for controlling the charging process of an electric vehicle, configured to carry out the aforementioned method. In particular, a control unit is specified that is configured for communication between the electric vehicle and a charging device connected to the electric vehicle via a charging cable, determining whether the charging device is a DC or AC charging device. The control unit is further configured to check whether the charging voltage provided by the charging device is greater than or equal to a threshold value characteristic of a DC charging voltage. For example, the threshold value is at least 400 V.The control unit is configured to prevent a charging process if communication indicates that the charging device is a DC charger and that the charging voltage provided by the charger is below the threshold value, e.g., 400 V. Furthermore, the control unit is configured to initiate a charging process if the previous step fails to prevent it.

[0016] According to an advantageous embodiment, the control unit is configured to output an error message via a user interface if the charging process is prevented. Further advantageous and optional embodiments of the control unit result from the preceding description of the method, and vice versa.

[0017] The invention further relates to an electric vehicle containing the control unit described above, and to a computer program comprising instructions which, when the program is executed by a computer, cause it to execute the method described above.

[0018] An embodiment of the invention is described below with reference to the accompanying drawings. Further details, preferred embodiments, and further developments of the invention will be derived from these drawings. Figure 24-1286 schematically illustrates this in detail.

[0019] Fig. 1 shows an electric vehicle during a charging process at a charging device, and

[0020] Fig. 2 Steps of a method for controlling a charging process of an electric vehicle according to an exemplary embodiment.

[0021] The components shown, as well as the relative sizes of the components, are not to be considered as being to scale.

[0022] Figure 1 shows an electric vehicle 1 during a charging process. The electric vehicle 1 can be, in particular, a battery electric vehicle (BEV) or a plug-in hybrid electric vehicle (PHEV). The electric vehicle 1 has an electrical energy storage device 2, which is, in particular, a so-called high-voltage battery. The high-voltage battery can, for example, have a voltage of about 400 V or about 800 V. In particular, the electrical energy storage device 2 can be a lithium-ion battery comprising a plurality of lithium-ion battery cells. The electrical energy storage device 2 is intended to provide energy for driving an electric motor of the electric vehicle 1; that is, the electrical energy storage device 2 is a traction battery of the electric vehicle 1.

[0023] To charge the electrical energy storage device 2, the electric vehicle 1 has a charging socket 3. In the charging process shown, the electric vehicle 1 is connected to a charging device 7, for example a charging station or a wallbox, by means of a charging cable 6. The charging cable 6 can be connected to the charging socket 3 of the electric vehicle 1 by means of a charging plug 5. If the charging plug 5 and the charging socket 3 do not conform to the same standard, an adapter 4 can be used if necessary.

[0024] The electric vehicle is equipped with a control unit 8, which controls the charging process. The steps of a method for controlling the charging process are schematically illustrated in Figure 2 using a flowchart. After connecting the electric vehicle 1 to the charging device 7 via a charging cable 6, communication takes place in step S1 between the electric vehicle 1 and the charging device 7, checking whether the charging device 7 is an AC or DC charging device. This information can be received, for example, by the control unit 8 of the electric vehicle 1 from the charging device 7 via signal lines in the charging cable 6. In a further step S2, the control unit 8 requests and measures a charging voltage from the charging device 7. For this purpose, a voltmeter is, for example, integrated into or connected to the control unit 8.

[0025] In step S3 of the procedure, it is checked whether the voltage provided by the charging device 7 is greater than or equal to a threshold value characteristic of a DC charging voltage, where the threshold value is, for example, at least 400 V. If the check reveals that the charging voltage provided by the charging device 7 is not greater than or equal to the threshold value, and previous communication has established that the charging device 7 is a DC charging device, a charging process is prevented in step S4. This means, in particular, that the charging contactors of the electric vehicle 1 do not open, thus preventing the flow of a charging current from the charging device 7 to the electric vehicle 1. If the described conditions for preventing the charging process are not met, the charging process is started in step S5.

[0026] By verifying that the supplied charging voltage is greater than or equal to the threshold value of, for example, at least 400 V, when the charging device was identified as a DC charging device during previous communication, it can be reliably ruled out that an AC charging device connected to the electric vehicle 1 was incorrectly identified as a DC charging device due to faulty communication, and that a DC charging process was subsequently initiated, which could damage components of the charging device 7 and / or the electric vehicle 1. In particular, this procedure reduces the risk of incorrect detection of a DC charging device when an AC charging plug 5 is used with a DC adapter 4.If such an adapter 4 is used and the charging socket uses 3 identical connection pins for the alternative transmission of an AC current or DC current, there would be a high risk that electronic components would be damaged by an incorrect detection of the type of voltage used.

[0027] If the charging process is prevented due to the check performed, in a further step S6 an error message is advantageously issued to a user of the electric vehicle 1, for example to a user interface in the vehicle and / or to an app on the user's smartphone. In this case, the user 24-1286 8 can be prompted to check the connection of the charging cable and, if applicable, the type of adapter being used.

[0028] Although the invention has been illustrated and described in detail with reference to exemplary embodiments, the invention is not limited by these embodiments. Rather, other variations of the invention can be derived by a person skilled in the art without departing from the scope of protection of the invention as defined by the claims.

[0029] 24-1286 9

[0030] Reference symbol list

[0031] 1 electric vehicle

[0032] 2 electrical energy storage units 3 charging sockets

[0033] 4 adapters

[0034] 5 charging plugs

[0035] 6 charging cables

[0036] 7 Charging device 8 Control unit

[0037] S1 to S6 process steps

Claims

24-1286 10 Patent claims 1. Method for controlling a charging process of an electric vehicle (1), comprising the steps: I) Communication (S1) between the electric vehicle (1) and a charging device (7) connected to the electric vehicle (1) by means of a charging cable (6), whether the charging device (7) is a DC charging device or an AC charging device, II) Requesting and measuring (S2) a charging voltage of the charging device (7) by the electric vehicle (1), III) Check (S3) whether the charging voltage provided by the charging device (7) is greater than or equal to a threshold value, wherein the threshold value is characteristic of a DC charging voltage, IV) Preventing (S4) a charging process if communication (S1) has shown that the charging device (7) is a DC charging device and verification (S3) has shown that the charging voltage provided by the charging device (7) is not greater than or equal to the threshold value, and V) Starting (S5) a charging process if no prevention of a charging process occurs in step V).

2. The method of claim 1, wherein the threshold is at least 400 V.

3. Method according to any of the preceding claims, wherein the charging device (7) is an AC charging device.

4. Method according to one of the preceding claims, wherein the charging cable (6) has a charging plug (5) which is connected to a charging socket (3) of the electric vehicle (1) by means of an adapter (4).

5. Method according to claim 4, wherein the adapter (4) is configured to connect the charging plug (5) to a DC port of the charging socket (3). 24-1286 11 6. Method according to one of the preceding claims, wherein in the event of the charging process being prevented an error message is issued to a user of the electric vehicle (1) (S6).

7. Control unit for controlling a charging process of an electric vehicle, wherein the control unit (8) is configured I) for communication (S1) between the electric vehicle (1) and a charging device (7) connected to the electric vehicle (1) by means of a charging cable (6), whether the charging device (7) is a DC charging device or an AC charging device, II) to request and measure (S2) a charging voltage of the charging device (7), III) to check (S3) whether the charging voltage provided by the charging device (7) is greater than or equal to a threshold value, wherein the threshold value is characteristic of a DC charging voltage, IV) to prevent (S4) a charging process if the communication (S1) has shown that the charging device (7) is a DC charging device and it has been determined that the charging voltage provided by the charging device (7) is not greater than or equal to the threshold value, and V) to start (S5) a charging process if no prevention of a charging process is effected.

8. Control unit according to claim 7, wherein the threshold is at least 400 V.

9. Control unit according to claim 7 or 8, wherein the control unit (8) is configured to issue an error message to a user of the electric vehicle (1) (S6) if the charging process has been prevented.

10. Electric vehicle (1) comprising a control unit (8) according to any one of claims 7 to 9.

11. Computer program product comprising instructions which, when the program is executed by a computer, cause it to execute the method according to any one of claims 1 to 6.

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