Method for operating a high-voltage onboard electrical system of a vehicle

Abstract

The invention relates to a method for operating a high-voltage onboard electrical system (3) of a vehicle (2), comprising a protection device (8) in the event of a physical contact with one of the high-voltage potentials (HV+, HV-) and a reference potential (M) while charging a high-voltage battery (6) by means of a DC charging station (5), wherein the protection device (8) has a voltage measuring device (SV1, SV2) and a protection circuit (9). According to the invention, a galvanically coupled DC-DC converter (GW) is arranged in one of the high-voltage potentials (HV+, HV-) between the protection device (8) and a DC charging connection, and the DC charging station (5) provides a charging voltage which is lower than a nominal voltage of the high-voltage battery (6). It is ascertained whether the physical contact with the high-voltage potential (HV+, HV-) in which the DC-DC converter (GW) is arranged is being carried out between the DC-DC converter (GW) and the DC charging station (5) and this is used as a trigger criterion for actuating the protection circuit (9) and / or an additional protection circuit (9) arranged between the high-voltage potential (HV+, HV-) in which the DC-DC converter (GW) is arranged and the reference potential (M) at a position between the DC-DC converter (GW) and the DC charging connection.

Description

[0001] Method for operating a high-voltage electrical system of a vehicle

[0002] The invention relates to a method for operating a high-voltage electrical system of a vehicle according to the features of the preamble of claim 1.

[0003] As described in the generic document DE 10 2019 008 833 A1, a protective device for an electrical direct current network, an on-board electrical system for a vehicle, a vehicle, and a direct current charging station are known from the prior art. The protective device comprises a first voltage measuring device between a positive potential line and a reference potential line and a second voltage measuring device between a negative potential line and the reference potential line, or a residual current measuring device in the reference potential line.The protective device further comprises a protective circuit with two protective circuit parts, wherein the first protective circuit part comprises a series connection of a first discharge resistor and a first protective switch between the positive potential line and the reference potential line, and the second protective circuit part comprises a series connection of a second discharge resistor and a second protective switch between the negative potential line and the reference potential line. The first and second protective switches can be controlled to close when a predetermined voltage value is undershot and / or exceeded as determined by the first and / or second voltage measuring device, or the first and / or second protective switches can be controlled to close when a fault current is measured by the residual current measuring device.

[0004] DE 102017 009 355 A1 discloses a method for operating a first vehicle electrical system supplied with a first electrical direct voltage and a second vehicle electrical system supplied with a second electrical direct voltage, wherein the first and second vehicle electrical systems are electrically coupled by means of an energy coupler comprising a first clocked energy converter. The first and second electrical direct voltages are electrically isolated from an electrical reference potential by means of an electrical isolation device and are monitored by the electrical isolation device.The first and the second on-board electrical system are galvanically coupled by means of the energy coupler, wherein in the event of a fault in the isolation device in an area of ​​one of the two on-board electrical systems, the energy coupler controls electrical potentials of the respective other of the two on-board electrical systems in such a way that respective potential differences between these electrical potentials and the reference potential are smaller than a predetermined comparison value.

[0005] Furthermore, a protective device for an electrical direct current network and a method for its operation, as well as an on-board electrical system for a vehicle, a vehicle, and a direct current charging station, are known from internally known prior art. The protective device comprises a voltage measuring device between a respective potential line and a reference potential line, and a protective circuit with a series connection of a protective capacitor, a protective resistor, and a respective circuit breaker between the respective potential line and the reference potential line, or with two protective circuit parts with a series connection of a protective capacitor, a protective resistor, and a circuit breaker between the respective potential line and the reference potential line.A discharge resistor is connected in parallel to the protective capacitor and the protective resistor, and a series circuit comprising a rapid discharge resistor and a rapid discharge switch is connected in parallel to the protective capacitor or to the protective capacitor and the protective resistor. The first and / or second protective switch can be triggered to close upon the occurrence of at least one trigger criterion determined by the first and / or second voltage measuring device.

[0006] A further internal protective device for an electrical direct current network, an on-board electrical system for a vehicle, a vehicle, and a direct current charging station is also known as prior art. The protective device comprises a respective voltage measuring device between a respective potential line and a reference potential line, and a protective circuit with a circuit breaker between the respective potential line and the reference potential line and at least one resistor, which is designed as a resistor with a fixed resistance value of a maximum of 800 Ω or as a voltage-dependent resistor, wherein the respective circuit breaker can be controlled to close upon the occurrence of at least one triggering criterion determined by means of the respective voltage measuring device. The object of the invention is to provide a method for operating a high-voltage on-board electrical system of a vehicle that is improved compared to the prior art.

[0007] The object is achieved according to the invention by a method for operating a high-voltage electrical system of a vehicle having the features of claim 1.

[0008] Advantageous embodiments of the invention are the subject of the subclaims.

[0009] In a method according to the invention for operating a high-voltage on-board electrical system of a vehicle with a protective device for protecting a human body in the event of physical contact with one of the high-voltage potentials and a reference potential during charging of a high-voltage battery by a direct current charging station to which the vehicle is connected by means of a charging cable, wherein the protective device has a voltage measuring device and a protective circuit with a circuit breaker between the respective high-voltage potential and the reference potential, it is provided that a galvanically coupled direct-current converter is arranged in one of the high-voltage potentials of the high-voltage on-board electrical system of the vehicle between the protective device and a direct current charging connection of the vehicle and that the direct current charging station provides a charging voltage which is lower than a nominal voltage of the high-voltage battery.It is determined whether physical contact with the high-voltage potential in which the DC-DC converter is arranged occurs between the DC-DC converter and the DC charging station, hereinafter also referred to as position P2 or second position. This is used as a triggering criterion for controlling the protective circuit, in particular at least one circuit breaker of the protective circuit, and / or for controlling another protective circuit, in particular at least one circuit breaker of this another protective circuit, which is arranged between the high-voltage potential in which the DC-DC converter is arranged and the reference potential at a position between the DC-DC converter and the DC charging connection.

[0010] According to the invention, it is provided that, based on a gradient of the measured voltage between the high-voltage potential in which the DC-DC converter is arranged and the reference potential, it is determined whether the body contact occurs between the DC-DC converter and the DC charging station, ie at position P2.

[0011] In particular, it is provided that if it has been determined that the body contact with the high-voltage potential in which the DC-DC converter is arranged occurs between the DC-DC converter and the DC charging station, i.e. at position P2, and in addition a voltage of the high-voltage potential in which the DC-DC converter is arranged to the reference potential between the DC-DC converter and the DC charging station immediately before the body contact does not exceed a predetermined limit value, the protective switches are not closed.

[0012] In particular, it is provided that if it has been determined that the body contact with the high-voltage potential in which the DC-DC converter is arranged occurs between the DC-DC converter and the DC charging station, i.e. at position P2, and in addition the voltage of the high-voltage potential in which the DC-DC converter is arranged to the reference potential between the DC-DC converter and the DC charging station immediately before the body contact exceeds the predetermined limit value, at least the protective switch between the high-voltage potential in which the DC-DC converter is arranged and the reference potential is closed and then opened again.In this case, this circuit breaker is closed until a current voltage of the high-voltage potential in which the DC-DC converter is arranged to the reference potential between the DC-DC converter and the DC charging station is zero, and then opened again, and / or it is closed until a current voltage of the high-voltage potential in which the DC-DC converter is arranged to the reference potential between the DC-DC converter and the high-voltage battery is as great as a difference between a voltage of the high-voltage potential in which the DC-DC converter is arranged to the reference potential between the DC-DC converter and the high-voltage battery immediately before body contact and the voltage of the high-voltage potential in which the DC-DC converter is arranged to the reference potential between the DC-DC converter and the DC charging station immediately before body contact, and then opened again.

[0013] Alternatively or additionally, it is provided that if it has been determined that the body contact with the high-voltage potential in which the DC-DC converter is arranged occurs between the DC-DC converter and the DC charging station, i.e. at position P2, and in particular if the voltage of the high-voltage potential in which the DC-DC converter is arranged to the reference potential between the DC-DC converter and the DC charging station immediately before the body contact exceeds the predetermined limit value, the at least one protective switch of the further protective circuit which is arranged between the high-voltage potential in which the DC-DC converter is arranged and the reference potential at the position between the DC-DC converter and the DC charging connection is closed.

[0014] In particular, the gradient is compared with a predetermined threshold value, whereby it is determined in particular whether the threshold value is exceeded or undercut, and thereby it is determined whether physical contact occurs between the DC-DC converter and the DC charging station.

[0015] In particular, it is provided that by closing the respective circuit breaker, at least one electrical resistor is connected between the high-voltage potential at which the DC-DC converter is arranged and the reference potential, i.e., the protective circuit of the protective device and / or the additional protective circuit has at least this resistor. The protective circuit of the protective device and / or the additional protective circuit can also have further components. In particular, the protective circuit is designed as described in DE 102019 008 833 A1, DE 10 2021 003 834, and / or DE 10 2021 003 835.

[0016] The described solution ensures the correct functioning of the protective device and its protective circuit even when the high-voltage vehicle electrical system includes a galvanically coupled DC-DC converter and physical contact with the high-voltage potential in which this DC-DC converter is located occurs at position P2, i.e., between the DC-DC converter and the DC charging station. This ensures rapid discharge of Y capacitors in this case as well, thus avoiding electric shocks of a magnitude that could be dangerous to humans.

[0017] The described solution focuses on measuring the high-voltage potentials relative to the reference potential. By differentiating the voltage (forming the derivative) of the voltage, the original output voltage can be determined based on the gradient of the voltage curve. Based on the output voltage, it can then be determined, by comparing it with threshold values, whether the body contact and thus the body discharge is occurring on the primary or secondary side of the DC-DC converter.

[0018] Embodiments of the invention are explained in more detail below with reference to a drawing.

[0019] It shows:

[0020] Fig. 1 shows a schematic of a vehicle coupled to a DC charging station.

[0021] Figure 1 shows a schematic representation of a vehicle 2 coupled to a direct current charging station 5. The vehicle 2 has a high-voltage electrical system 3 with high-voltage potentials HV+, HV-, i.e. with a positive potential HV+ and a negative potential HV-, and with a reference potential M, in particular ground or earth potential. Furthermore, the high-voltage electrical system 3 has a protective device 8 for protecting a human body MK in the event of physical contact with one of the high-voltage potentials HV+, HV- and the reference potential M while a high-voltage battery 6 is being charged by the direct current charging station 5. When coupled to the direct current charging station 5, the high-voltage electrical system 3 forms a common direct current network 1 with the latter. The high-voltage battery 6 of the vehicle 2, which is electrically charged at the direct current charging station 5, serves in particular to provide electrical energy for at least one electric drive unit of the vehicle 2 for driving the vehicle 2.

[0022] Both in vehicle 2 and in the DC charging station 5, Y-capacitors CyF+, CyF-, CyL+, and CyL- are used as a measure to reduce the emission of EMC interference (EMC = electromagnetic compatibility). In particular, Y-capacitors CyF+, CyF-, CyL+, and CyL- are generally cheaper and more compact EMC filter measures than inductive interference filters, such as common mode or differential mode chokes. From an EMC perspective, it would therefore be advantageous to use Y-capacitors CyF+, CyF-, CyL+, and CyL- with large capacitance values. However, a disadvantage of an electrified vehicle 2, such as an electric vehicle or hybrid vehicle, is that the energy content of the Y capacitors CyF+, CyF-, CyL+, CyL- can be felt by a vehicle user if they can touch a high-voltage potential HV+, HV- and are simultaneously connected to ground potential. They will then receive an electric shock.Depending on the severity of this electric shock, it can be hazardous to health. For example, it can lead to ventricular fibrillation or even death. Such an electric shock represents a so-called "single fault" and must be avoided. Therefore, the energy content of the Y capacitors CyF+, CyF-, CyL+, and CyL- is limited by regulations to prevent any danger to the vehicle user.

[0023] From a high-voltage safety perspective, small capacitance values ​​for the Y capacitors CyF+, CyF-, CyL+, and CyL- are advantageous. Normative requirements, for example those regulated in standard LV123, require that a maximum energy content, in particular 0.2 J, in the Y capacitors CyF+, CyF-, CyL+, and CyL- not be exceeded, or that so-called "alternative measures" be provided, such as reinforced insulation. However, this always means that when two high-voltage systems are coupled, for example, vehicle 2 and DC charging station 5, if reinforced insulation is selected as the "alternative measure," both devices must always have this reinforced insulation at the same time. However, this cannot currently be guaranteed.

[0024] In other standards, such as IEC 1772, IEC 60479-1, and IEC 60479-2, the energy content of the Y capacitors CyF+, CyF-, CyL+, and CyL- is not specified as a health-endangering quantity that must not be exceeded. Instead, a charge quantity is specified as the damaging mechanism, which must not exceed a specified value. For example, a graph showing the relationship between the duration of a body current and the value of the body current is provided. An alternative approach, such as reinforced insulation, is not accepted here.

[0025] Figure 1 shows a circuit layout of an embodiment of the high-voltage electrical system 3 during a direct current charging process of the vehicle 2. The high-voltage electrical system 3 of the vehicle 2 is connected to the direct current charging station 5 via a charging cable 4. In the example shown, the charging cable 4 is already connected to the connection contacts AK+, AK- of a direct current charging port of the vehicle 2, and the charging contactors LS+, LS- of the vehicle 2 in the high-voltage potential lines HV+L, HV-L are still open. They are closed for charging.

[0026] On the left side is the DC charging station 5 with a charging station voltage source SQ, a charging station internal resistance RLS and the Y capacitors CyL+, CyL-,

[0027] Charging cable 4 is shown to the right.

[0028] To the right, the vehicle 2 is shown with its high-voltage electrical system 3, comprising the charging contactors LS+, LS-, the Y-capacitors CyF+, CyF-, for example, EMC filters, an X-capacitor Cx, for example, of a DC link, and the high-voltage battery 6 with its main contactors HS+, HS-. The high-voltage battery 6 is shown as an electrical battery energy source 7, comprising, for example, a plurality of individual cells electrically connected in series and / or parallel, with an internal battery resistance R Ba tt.

[0029] Additionally, this circuit diagram depicts the human body MK with a body resistance RK and a switch symbol for an insulation fault IF, for example, in the case of a defective charging cable 4, here an example of a fault at the positive potential HV+. The insulation fault IF can also be

[0030] Negative potential HV- may occur. This is not shown here. If the insulation fault IF occurs, the switch symbol is closed. In the event of such an insulation fault IF and contact of the human body MK with one of the

[0031] High-voltage potentials HV+, HV- and a reference potential M cause a discharge through the human body MK.

[0032] In order to avoid this discharge through the human body MK or at least to reduce it to a permissible level, particularly with regard to a health hazard, the protective device 8 is provided with a protective circuit 9 for reducing the electric shock through the Y capacitors CyF+, CyF-, CyL+, CyL-. The protective device 8 comprises a first voltage measuring device SV1 between the positive potential line HV+L and the reference potential line ML for measuring a voltage between the positive potential line HV+L and the reference potential line ML, i.e. between the positive potential HV+ and the reference potential M, in particular ground potential, in particular the vehicle body mass, and a second voltage measuring device SV2 between the negative potential line HV-L and the reference potential line ML for measuring a voltage between the negative potential line HV-L and the reference potential line ML, i.e.between the negative potential HV- and the reference potential M, in particular ground potential, in particular the vehicle bodyshell. The voltage measurements, in particular the voltage measuring devices SV1, SV2, control an associated protective switch SS1, SS2 when at least one predetermined triggering criterion occurs. The protective switches SS1, SS2 are each designed as a semiconductor switch, for example a MOSFET. This connects a discharge network between the positive potential HV+ and the reference potential M, in particular the bodyshell, or a discharge network between the negative potential HV- and the reference potential M, in particular the bodyshell. In the example shown, these discharge networks are protective circuit parts 9.1, 9.2 of the protective circuit 9.

[0033] The respective discharge network, ie the respective protective circuit part 9.1, 9.2, comprises at least one electrical resistor, via which the Y capacitors CyF+, CyF-, CyL+, CyL- are discharged. In the example shown, the respective discharge network preferably consists of an uncharged capacitor, hereinafter referred to as protective capacitor Cs1, Cs2, and an electrically parallel-connected resistor, hereinafter referred to as

[0034] Discharge resistors Re1, Re2 are designated. Additionally, a protective resistor Rs1, Rs2 is provided, which is electrically connected in series with the protective capacitor Cs1, Cs2. For example, only the discharge resistors Re1, Re2 could be provided.

[0035] As described so far, the high-voltage electrical system 3 including the protective device 8 corresponds to that described in DE 10 2019 008 833 A1. For further information on its structure and functionality, reference is therefore made to DE 10 2019 008 833 A1, in particular to its figures and figure descriptions. Further examples of such high-voltage electrical systems 3 with a protective device 8 are described in DE 10 2021 003 834 and DE 10 2021 003 835. They differ essentially in the structure of the protective device, in particular in the components of the discharge network.

[0036] For the solution described below, the protective devices 8 described in DE 102019 008 833 A1, in DE 10 2021 003 834 and in DE 102021 003 835 and their respective mode of operation for the high-voltage electrical system 3 of the vehicle 2 can be used, ie the protective device 8 shown in Figure 1 can also be designed in the form of another of the embodiments described in DE 102019 008 833 A1, in DE 10 2021 003 834 and in DE 102021 003 835 and function as described there.

[0037] The essential difference between the high-voltage electrical system 3 shown here and the high-voltage electrical systems 3 shown and described in DE 10 2019 008 833 A1, DE 10 2021 003 834, and DE 10 2021 003 835 is that in the high-voltage electrical system 3 of the vehicle 2 shown and described here, a galvanically coupled DC-DC converter GW is arranged between the protective device 8 and the DC charging connection of the vehicle 2 at one of the high-voltage potentials HV+, HV- (in the example shown here, at the positive potential HV+). This makes it possible to charge the high-voltage battery 6 at a DC charging station 5 that provides a charging voltage that is lower than a nominal voltage of the high-voltage battery 6. The DC charging station 5 shown is such a DC charging station 5.

[0038] This DC-DC converter GW affects the effectiveness of the protective device 8 if the insulation fault IF and the above-described physical contact between one of the high-voltage potentials HV+, HV- and the reference potential M with the high-voltage potential in which the DC-DC converter GW is arranged occurs between the DC-DC converter GW and the DC charging station 5. In the example shown here, this high-voltage potential is the positive potential HV+. In other examples, the DC-DC converter GW can also be arranged in the negative potential HV-, so that this

[0039] Negative potential HV- would be affected. This position of body contact with the high-voltage potential, in which the DC-DC converter GW is arranged, between the DC-DC converter GW and the DC charging station 5, which is critical for the effectiveness of the protective device 8, is referred to below as position P2.

[0040] The other possible positions in which body contact could occur between one of the high-voltage potentials HV+, HV-, and the reference potential M are the other high-voltage potential, in the example shown, the negative potential HV-, hereinafter referred to as position P1, and the high-voltage potential in which the DC-DC converter GW is arranged, between the DC-DC converter GW and the high-voltage battery 6, hereinafter referred to as position P3. At these two other positions P1 and P3, body contact is uncritical for the protective device 8, in particular for its functionality and effect, even when the galvanically coupled DC-DC converter GW is used in the high-voltage on-board electrical system 3 of the vehicle 2.If the body contact occurs with one of the high-voltage potentials HV+, HV-, thus at one of these two positions P1, P3, the protective device 8 continues to operate as described in DE 10 2019 008 833 A1, in DE 10 2021 003 834 or in DE 10 2021 003 835, in particular in their figures and figure descriptions, and achieves the same effect as described there.

[0041] If body contact occurs at position P3, i.e. between the DC-DC converter GW and the high-voltage battery 6, then the voltage between the high-voltage potential contacted by the body MK and the reference potential M at position P3 is reduced to 0V by means of the protective device 8. At position P2, the voltage between this high-voltage potential and the reference potential M is reduced by the same amount as at position P3. Since the output voltage between this high-voltage potential and the reference potential M at position P2 is reduced by the voltage value of the DC-DC converter GW, the final value is also a much lower or even negative voltage. However, since body contact occurs at position P3 and not at position P2, this is not important. At position P3, where body contact occurs, the voltage is quickly reduced.The functioning of the protective device as described in DE 10 2019 008 833 A1, in DE 10 2021 003 834 or in DE 102021 003 835 is therefore advantageous for body contact at position P3 and is therefore also retained in the solution described here for body contact at position P3.

[0042] If body contact occurs at position P2, i.e., between the DC-DC converter GW and the DC charging station 5, the voltage between the high-voltage potential contacted by the body MK and the reference potential M at position P3 is reduced by only a small amount, namely by the voltage between this high-voltage potential and the reference potential M at position P2. The voltage between this high-voltage potential and the reference potential M is reduced to 0V at position P2 on a capacitor discharge curve. Activating the protective circuit 9 of the protective device 8 at position P3, as described in DE 10 2019 008 833 A1, DE 10 2021 003 834, or DE 102021 003 835, would abruptly reduce the voltage at position P3 to 0V.As a result, from the moment of activation, the voltage between the high-voltage potential contacted by the body MK and the reference potential M at position P2 is reduced by the voltage value that prevailed at position P3 at the time of activation. Due to the change in sign, since the output voltage at position P2 is lower than at position P3, the voltage at position P2 then increases and thus poses an even greater risk than without the activation of the protective circuit 9 of the protective device 8.

[0043] If the body contact occurs at position P1, i.e. at the high-voltage potential at which the DC-DC converter GW is not located, in the example shown here thus at the negative potential HV-, then the voltage between the high-voltage potential contacted by the body MK and the reference potential M at position P1 is reduced to 0V by means of the protective device 8. The voltage between the other high-voltage potential and the reference potential M increases by the same amount at both positions P2 and P3. However, since in this case the contact by the human body MK occurs at position P1, this is irrelevant because the voltage is quickly dissipated there.The functioning of the protective device as described in DE 10 2019 008 833 A1, in DE 10 2021 003 834 or in DE 102021 003 835 is therefore advantageous for body contact at position P3 and is therefore also retained in the solution described here for body contact at position P3.

[0044] As can be seen from the previous descriptions, it is therefore necessary to distinguish whether the body MK came into contact with the high-voltage potential in which the DC-DC converter GW is arranged at position P2 or P3. In particular, it must be determined whether the body MK came into contact with the high-voltage potential in which the DC-DC converter GW is arranged at position P2, because then a different mode of operation of the protective device 8, in particular the protective circuit 9, is required than that described in DE 102019 008 833 A1, DE 10 2021 003 834, or DE 10 2021 003 835.

[0045] The solution described here therefore provides for determining whether physical contact with the high-voltage potential in which the DC-DC converter GW is arranged occurs between the DC-DC converter GW and the DC charging station 5, i.e. whether physical contact occurs at position P2. Since the respective position P1, P2, P3, in particular position P2, must be detected very quickly in order for the protective device 8, in particular its protective circuit 9, to take the correct action, it is not possible to wait for the discharge curve, i.e. the e-function of the capacitor discharge of the Y capacitors CyF+, CyF-, CyL+, CyL-, to decay. The distinguishing feature used for the solution described here is the slope of the discharge curve, i.e. the derivative of the discharge curve.Based on the gradient of the measured voltage between the high-voltage potential at which the DC-DC converter GW is arranged and the reference potential M, it is determined whether physical contact has occurred between the DC-DC converter GW and the DC charging station 5. The voltage is measured using the voltage measuring device provided for measuring the voltage between this high-voltage potential and the reference potential M, in the example shown here, using the first voltage measuring device SV1.

[0046] The mesh equation applies to the high-voltage potential in which the

[0047] DC-DC converter GW is arranged, here for the plus potential HV+:

[0048] Oops t) — U GW + Up2( ) (1)

[0049] This is

[0050] [ / P3(t) the voltage between the high-voltage potential in which the DC-DC converter GW is arranged, here the positive potential HV+, and the reference potential M at position P3,

[0051] [ / p2(t) the voltage between the high-voltage potential in which the DC-DC converter GW is arranged, here the plus potential HV+, and the reference potential M at position P2,

[0052] U GW the voltage of the DC-DC converter GW.

[0053] A body discharge at position P3 has the following course with respect to position P3: and for its gradient (derivative) applies: A body discharge at position P2 has the following course relative to position P3: and for its gradient (derivative) applies:

[0054] U 0P3 and U 0P2 correspond to the voltages of the high-voltage potential in which the DC-DC converter GW is arranged, in this example the

[0055] Positive potential HV+, to the reference potential M at positions P3 and P2 immediately before the onset of the body discharge. R is the body resistance RK and C is the total capacitance of the Y capacitors CyF+, CyF-, CyL+, CyL-,

[0056] Considering the two derivatives, a difference in the gradient results depending on the position of the body contact. For a contact at position P3, the formula for the derivative (formula (3)) contains the factor U 0P3 , while in case of contact at position P2 the derivative (formula (5)) has the factor U 0P2 contains.

[0057] The gradient allows the location of body contact to be identified without delay, allowing the protective device 8, in particular its protective circuit 9, to respond correctly immediately. For this purpose, the determined gradient is compared with at least one predefined threshold value. In particular, it is determined whether this threshold value is exceeded or undershot. This comparison determines whether or not body contact occurred at position P2.

[0058] The determination of the gradient (derivative) can be carried out, for example, using a capacitor circuit, an operational amplifier (differentiator) or by multiple sampling, ie measuring the voltage using the relevant, here the first, voltage measuring device SV1, and calculation.

[0059] In the following, reaction options of the protective device 8 for the determined body contact at the respective position P1, P2, P3 are described, or in particular if it has been determined that the body contact occurs at position P2, because if the body contact occurs at the positions P1 and P3, ie if it is not determined that the body contact occurs at position P2, then a short-circuiting / rapid discharge of the affected high-voltage potential takes place by means of the protective device 8 and its protective circuit 9 on the basis of DE 10 2019 008 833 A1 and / or in the

[0060] DE 10 2021 003 834 and / or in the manner described in DE 102021 003 835.

[0061] The essential difference to DE 102019 008 833 A1, DE 102021 003 834, and DE 10 2021 003 835 is therefore the determination of whether the body contact occurs at position P2, and if so, the different procedure. This adds the triggering criterion for triggering the protective circuit 9, i.e., for closing at least one or both circuit breakers SS1, SS2, at positions P1, P2, P3 of the body contact, in particular the triggering criterion of whether or not the body contact occurs at position P2, or the triggering criterion that the body contact occurs at position P2. This triggering criterion, ie its presence, is determined, as described above, in particular based on the increase in the voltage over time t between the high-voltage potential in which the DC-DC converter GW is arranged, in the example shown here the plus potential HV+, and the reference potential M, in particular according to formula (5).

[0062] If it has thus been determined that the body contact with the high-voltage potential in which the DC-DC converter GW is arranged, in the example shown thus with the positive potential HV+, occurs between the DC-DC converter GW and the DC charging station 5, i.e. at position P2, then there are several possibilities for the then implemented functioning of the protective device 8, in particular its protective circuit 9:

[0063] - No action by the protective device 8 if the voltage does not pose a danger to humans, ie the reloading of the

[0064] Y capacitors CyF+, CyF-, CyL+, CyL- by the amount of U 0P2 does not result in any exceedance of specified, particularly legally prescribed, limit values. Thus, if the voltage U 0P2of the high-voltage potential in which the DC-DC converter GW is arranged, to the reference potential M between the DC-DC converter GW and the DC charging station 5, i.e. at position P2, does not exceed a predetermined limit immediately before physical contact, the protective switches SS1, SS2 are not closed. - Discharge of the high-voltage potential in which the DC-DC converter GW is arranged, in the example shown here the positive potential HV+, to the reference potential M at position P3 by the voltage value U 0P2, i.e. by the value of the voltage of the high-voltage potential in which the DC-DC converter GW is arranged, to the reference potential M between the DC-DC converter GW and the DC charging station 5, i.e. at position P2, immediately before body contact. This can be done, for example, by closing the relevant circuit breaker, here the first circuit breaker SS1, and then opening it again. The opening occurs, for example, as soon as a voltage of U is present at position P3 between the high-voltage potential in which the DC-DC converter GW is arranged and the reference potential M. 0P3 - U 0P2 is applied, ie until this voltage is equal to the difference between the voltage U 0P2 of the high-voltage potential in which the DC-DC converter GW is arranged, to the reference potential M between the DC-DC converter GW and the DC charging station 5, ie at position P2, to the voltage U 0P3of the high-voltage potential in which the DC-DC converter GW is arranged, to the reference potential M between the DC-DC converter GW and the high-voltage battery 6, ie at position P3, immediately before the body contact. Alternatively, the opening takes place, for example, when at position P2, ie in the high-voltage potential in which the DC-DC converter GW is arranged, between the

[0065] DC-DC converter GW and the DC charging station 5, the voltage between this high-voltage potential and the reference potential M OV is. In particular, if the voltage U 0P2of the high-voltage potential in which the DC-DC converter GW is arranged to the reference potential M between the DC-DC converter GW and the DC charging station 5, i.e. at position P2, immediately before the body contact exceeds the specified limit value, at least the protective switch SS1 between the high-voltage potential in which the DC-DC converter GW is arranged and the reference potential M is closed until the current voltage of the high-voltage potential in which the DC-DC converter GW is arranged to the reference potential M between the DC-DC converter GW and the DC charging station 5 is zero, and then opened again, and / or until a current voltage of the high-voltage potential in which the DC-DC converter GW is arranged to the reference potential M between the DC-DC converter GW and the high-voltage battery 6 is as large as a difference between the voltage of the high-voltage potential,in which the DC-DC converter GW is arranged, to the reference potential M between the DC-DC converter GW and the high-voltage battery 6 immediately before the body contact and the voltage of the high-voltage potential in which the DC-DC converter GW is arranged, to the reference potential M between the DC-DC converter GW and the DC charging station 5 immediately before the body contact, and then opened again.

[0066] For these two possibilities according to the two points above, the most accurate knowledge possible about the voltage U 0P2 of the high-voltage potential in which the DC-DC converter GW is located to the reference potential M between the DC-DC converter GW and the DC charging station 5, ie at position P2, immediately before body contact. This voltage U 0P2 can be calculated from the transformation ratio of the DC-DC converter GW and from the voltage measured by the corresponding voltage measuring device, here the first

[0067] Voltage measuring device SV1, measured voltage U 0P3 of the high-voltage potential in which the DC-DC converter GW is arranged, to the reference potential M between the DC-DC converter GW and the high-voltage battery 6, ie at position P3, immediately before body contact or measured by means of a further voltage measuring device directly at an input of the DC-DC converter GW.

[0068] As an alternative to these two possibilities, in particular as an alternative to the possibility according to the second point above, unloading at the

[0069] Position P2. For this purpose, a further discharge circuit, in particular a further discharge network, in particular a further protection circuit 9, is required between the high-voltage potential in which the DC-DC converter GW is arranged and the reference potential at position P2, ie between the

[0070] DC-DC converter GW and the DC charging station 5. To implement this possibility, the high-voltage vehicle electrical system 3 has such an additional discharge circuit, in particular an additional protective circuit 9, at this position P2. This is advantageously designed as described in DE 102019 008 833 A1 and / or in

[0071] DE 10 2021 003 834 and / or in DE 102021 003 835.

[0072] When using this additional protection circuit, especially when the voltage U 0P2of the high-voltage potential in which the DC-DC converter GW is arranged, to the reference potential M between the DC-DC converter GW and the DC charging station 5, ie at position P2, immediately before body contact exceeds the predetermined limit value, at least one protective switch between the high-voltage potential in which the DC-DC converter GW is arranged and the reference potential M in the area of ​​position P2, ie between the DC-DC converter GW and the DC charging connection, arranged further protective circuit 9 is closed.

[0073] For better differentiation or faster reaction times, in addition to the above-described gradient of the measured voltage between the high-voltage potential at which the DC-DC converter GW is located and the reference potential M, further measured variables can be used, for example the current value of the voltage measurement of the high-voltage potential at which the DC-DC converter GW is located—in the example shown here, the positive potential HV+—to the reference potential M, determined here using the first voltage measuring device SV1—or its averaging over a predefined period of time. For example, a predefined limit value for this current value of the voltage measurement or an average value can be specified.The protective switch SS1 of the protective circuit 9 closes when this limit is undershot, at the same time the calculated gradient of the measured voltage between the high-voltage potential at which the DC-DC converter GW is arranged and the reference potential M has, for example, a value below -1e5, and the protective switch of the further protective circuit 9 is open. This protective switch of the further protective circuit 9 is closed, for example, when the above-mentioned limit of the voltage measurement is undershot and at the same time the calculated gradient of the measured voltage between the high-voltage potential at which the DC-DC converter GW is arranged and the reference potential M has, for example, a value between -1e4 and -1e5. In addition, the first protective switch SS1 of the protective circuit 9 must not be closed in this case.

[0074] With the described solution, the position P1, P2, P3 of the body contact can be deduced, particularly based on the gradient of the discharge curve, and the protective device 8 can then react correctly. The described solution is particularly suitable for vehicles 2 with a galvanically coupled DC-DC converter GW and / or with at least one inverter operated as a DC-DC converter. The galvanically coupled DC-DC converter GW can also be used, for example, to supply auxiliary units. The solution can also be used for DC charging stations 5 consisting of a galvanically isolating DC-DC converter and / or a battery and a galvanically coupled converter. List of reference symbols

[0075] 1 DC network

[0076] 2 vehicles

[0077] 3 High-voltage electrical system

[0078] 4 charging cables

[0079] 5 DC charging station

[0080] 6 high-voltage battery

[0081] 7 Battery energy source

[0082] 8 Protective device

[0083] 9 Protection circuit

[0084] 9.1 , 9.2 Protection circuit part

[0085] AK+, AK- connection contact of a DC charging port

[0086] Cs1, Cs2 protective capacitor

[0087] Cx X-capacitor

[0088] CyF+, CyF- Y capacitor vehicle

[0089] CyL+, CyL- Y capacitor DC charging station

[0090] GW DC-DC converter

[0091] HS+, HS- main contactor

[0092] HV+ plus potential

[0093] HV negative potential

[0094] HV+L positive potential line

[0095] HV-L negative potential line

[0096] IF insulation fault

[0097] LS+, LS- charging contactor

[0098] M reference potential

[0099] ML reference potential line

[0100] MK body

[0101] P1, P2, P3 positions

[0102] Rßatt Battery internal resistance

[0103] RK body resistance

[0104] RLS charging station internal resistance

[0105] Re1, Re2 discharge resistance

[0106] Rs1 , Rs2 protective resistor SQ charging station voltage source

[0107] SS1, SS2 circuit breaker

[0108] SV1 , SV2 voltage measuring device

Claims

Patent claims Method for operating a high-voltage on-board network (3) of a vehicle (2) with a protective device (8) for protecting a human body (MK) in the event of physical contact with one of the high-voltage potentials (HV+, HV-) and a reference potential (M) during charging of a high-voltage battery (6) by a direct current charging station (5) to which the vehicle (2) is connected by means of a charging cable (4), wherein the protective device (8) has a voltage measuring device (SV1, SV2) and a protective circuit (9) with a protective switch (SS1, SS2) between the respective high-voltage potential (HV+, HV-) and the reference potential (M), characterized in that in one of the high-voltage potentials (HV+,HV-) of the high-voltage electrical system (3) of the vehicle (2), a galvanically coupled DC-DC converter (GW) is arranged between the protective device (8) and a DC charging connection of the vehicle (2), and the DC charging station (5) provides a charging voltage which is lower than a nominal voltage of the high-voltage battery (6), wherein it is determined whether the body contact with the high-voltage potential (HV+, HV-), in which the DC-DC converter (GW) is arranged, occurs between the DC-DC converter (GW) and the DC charging station (5) by determining this on the basis of a gradient of the measured voltage between the high-voltage potential (HV+, HV-), in which the DC-DC converter (GW) is arranged, and the reference potential (M), and this is used as a triggering criterion for controlling the protective circuit (9) and / or a further protective circuit (9) which is arranged between the high-voltage potential (HV+, HV-), in which the DC-DC converter (GW) is arranged,and the reference potential (M) at a position between that, DC-DC converter (GW) and the DC charging port, is used. Method according to claim 1, characterized in that when it has been determined that the physical contact with the high-voltage potential (HV+, HV-) in which the DC-DC converter (GW) is arranged occurs between the DC-DC converter (GW) and the DC charging station (5), - if a voltage of the high-voltage potential (HV+, HV-) in which the DC-DC converter (GW) is arranged to the reference potential (M) between the DC-DC converter (GW) and the DC charging station (5) does not exceed a predetermined limit immediately before body contact, the protective switches (SS1, SS2) are not closed, - if the voltage of the high-voltage potential (HV+, HV-), in which the DC-DC converter (GW) is arranged, to the reference potential (M) between the DC-DC converter (GW) and the DC charging station (5) immediately before body contact exceeds the specified limit value, at least the protective switch (SS1, SS2) between the high-voltage potential (HV+, HV-), in which the DC-DC converter (GW) is arranged, and the reference potential (M) is closed until a current voltage of the High-voltage potential (HV+, HV-), in which the DC-DC converter (GW) is arranged, to the reference potential (M) between the DC-DC converter (GW) and the DC charging station (5) is zero, and then opened again, and / or until a current voltage of the high-voltage potential (HV+, HV-), in which the DC-DC converter (GW) is arranged, to the reference potential (M) between the DC-DC converter (GW) and the high-voltage battery (6) is as large as a difference between a voltage of the high-voltage potential (HV+, HV-) in which the DC-DC converter (GW) is arranged, to the reference potential (M) between the DC-DC converter (GW) and the high-voltage battery (6) immediately before the body contact and the voltage of the high-voltage potential (HV+, HV-) in which the DC-DC converter (GW) is arranged, to the reference potential (M) between the DC-DC converter (GW) and the DC charging station (5) immediately before the body contact, and is then opened again, and / or - at least one circuit breaker of the further protective circuit (9) which is located between the high-voltage potential (HV+, HV-), in which the DC-DC converter (GW) is arranged, and the reference potential (M) at the position between the DC-DC converter (GW) and the DC charging connection, is closed. Method according to claim 1 or 2, characterized in that the gradient is compared with a predetermined threshold value, wherein in particular it is determined whether the threshold value is undershot or exceeded, and thereby it is determined whether physical contact occurs between the DC-DC converter (GW) and the DC charging station (5). Method according to one of the preceding claims, characterized in that by closing the respective protective switch (SS1, SS2), at least one electrical resistor is connected between the high-voltage potential (HV+, HV-), in which the DC-DC converter (GW) is arranged, and the reference potential (M).

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