Method for operating high-voltage on-board electrical system of vehicle

Abstract

The invention relates to a method for operating a high-voltage on-board electrical system (3) of a vehicle (2), comprising a protection device (8) for coping with human body contact with one of the high-voltage potentials (HV +, HV-) and a reference potential (M) during charging of a high-voltage battery (6) by means of a direct-current charging station (5), the protection device (8) having a voltage measuring device (SV1, SV2), sV2) and a protection circuit (9). According to the invention, at one of the high-voltage potentials (HV +, HV-), a galvanically coupled DC-DC converter (GW) is arranged between the protection device (8) and the DC charging connection, and the charging voltage provided by the DC charging station (5) is lower than the nominal voltage of the high-voltage battery (6). According to the invention, it is determined whether a human 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), and this is used as a trigger criterion for actuating a protection circuit (9) and / or a further protection circuit (9) in which the high-voltage potential (HV +, HV-) of the DC-DC converter (GW) is arranged, hV-) and the reference potential (M) are arranged at a position between the DC-DC converter (GW) and the DC charging interface.

Description

Technical Field

[0001] The invention relates to a method for operating a high-voltage on-board electrical system of a vehicle according to the features of the preamble of claim 1 . Background Art

[0002] As described in the similar document DE 10 2019 008 833 A1, a protection device for a DC power grid, an onboard electrical system of a vehicle, a vehicle and a DC charging station is known in the prior art. The protection device includes a first voltage measuring device located between the positive potential line and the reference potential line and a second voltage measuring device located between the negative potential line and the reference potential line, or a fault current measuring device located in the reference potential line. In addition, the protection device also includes a protection circuit having two protection circuit parts, wherein the first protection circuit part includes a series circuit of a first discharge resistor and a first protection switch located between the positive potential line and the reference potential line, and the second protection circuit part includes a series circuit of a second discharge resistor and a second protection switch located between the negative potential line and the reference potential line. When the first and / or second voltage measuring device determines that the voltage is below and / or exceeds the specified voltage value, the first protection switch and the second protection switch can be actuated to close, or when the fault current is measured by the fault current measuring device, the first and / or second protection switch can be actuated to close.

[0003] DE 10 2017 009 355 A1 discloses a method for operating a first onboard electrical system to which a first DC voltage is applied and a second onboard electrical system to which a second DC voltage is applied, wherein the first onboard electrical system and the second onboard electrical system are electrically coupled by means of an energy coupler, the energy coupler having a first clocked energy converter. Here, the first DC voltage and the second DC voltage are electrically insulated from a reference potential by means of an electrical insulation device and monitored by the electrical insulation device. The first onboard electrical system and the second onboard electrical system are galvanically coupled by means of the energy coupler, wherein, in the event of a failure of the insulation device, in the region of one of the two onboard electrical systems, the energy coupler controls the potential of the other of the two onboard electrical systems so that the potential difference of each of these potentials with respect to the reference potential is less than a specified comparison value.

[0004] In addition, in the prior art known internally, a DC power grid and an operating method thereof, as well as an onboard electrical system of a vehicle, a protection device for a vehicle and a DC charging station are known. The protection device includes a voltage measuring device and a protection circuit located between each potential line and a reference potential line, and the protection circuit has a series circuit of a protection capacitor, a protection resistor and a corresponding protection switch between the corresponding potential line and the reference potential line, or has two protection circuit parts, and the two protection circuit parts have a series circuit of a protection capacitor, a protection resistor and a protection switch between the corresponding potential line and the reference potential line. The discharge resistor is connected in parallel with the protection capacitor and the protection resistor, and the series circuit composed of a fast discharge resistor and a fast discharge switch is connected in parallel with the protection capacitor or the protection capacitor and the protection resistor. When it is determined by means of the first and / or second voltage measuring device that at least one triggering criterion has occurred, the first and / or second protection switch can be actuated to close.

[0005] As a prior art, another protection device for a DC grid, an onboard electrical system of a vehicle, a vehicle and a DC charging station is also known. The protection device comprises a corresponding voltage measuring device and a protection circuit between each potential line and a reference potential line, the protection circuit having a protection switch and at least one resistor between the corresponding potential line and the reference potential line, the at least one resistor being designed as a resistor with a fixed resistance value of a maximum of 800Ω or a voltage-dependent resistor, wherein when the presence of at least one triggering criterion is determined by means of the corresponding voltage measuring device, the corresponding protection switch can be actuated to close. Summary of the invention

[0006] The object of the present invention is to provide a method for operating a high-voltage on-board electrical system of a vehicle which is improved compared to the prior art.

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

[0008] Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0009] In the method for operating a high-voltage on-board electrical system of a vehicle according to the present invention, the high-voltage on-board electrical system of the vehicle has a protective device to protect a human body when a human body contacts one of the high-voltage potentials and a reference potential during charging of a high-voltage battery by a DC charging station connected to the vehicle by means of a charging line, wherein the protective device has a voltage measuring device and a protective circuit having a protective switch between the corresponding high-voltage potential and the reference potential, and is designed to be arranged between the protective device and the DC charging interface of the vehicle in one of the high-voltage potentials of the high-voltage on-board electrical system of the vehicle, and the charging voltage provided by the DC charging station is lower than the rated voltage of the high-voltage battery. It is determined whether the human body contact with the high-voltage potential in which the DC-DC converter is arranged is between the DC-DC converter and the DC charging station, which is also referred to as position P2 or the second position below. This will be used as a trigger criterion for actuating a protection circuit, in particular at least one protection switch of the protection circuit, and / or actuating another protection circuit, in particular at least one protection switch of the other protection circuit, in which the protection circuit is arranged between the high voltage potential of the DC-DC converter and a reference potential at a position between the DC-DC converter and the DC charging interface.

[0010] According to the present invention, it is designed to determine whether human body contact is made between the DC-DC converter and the DC charging station (i.e., at position P2) based on the rising slope of the voltage measured between the high voltage potential in which the DC-DC converter is arranged and the reference potential.

[0011] In particular, it is designed that if it is determined that human 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 the voltage of the high-voltage potential in which the DC-DC converter is arranged between the DC-DC converter and the DC charging station relative to the reference potential does not exceed a specified threshold value immediately before human body contact, the protective switch will not be closed.

[0012] In particular, it is designed that if it is determined that human 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 the voltage of the high-voltage potential in which the DC-DC converter is arranged between the DC-DC converter and the DC charging station relative to the reference potential exceeds a specified threshold value just before human body contact, the protective switch is closed at least between the high-voltage potential in which the DC-DC converter is arranged and the reference potential, and then opened again. The protective switch is closed here until the current voltage of the high-voltage potential of the DC-DC converter arranged between the DC-DC converter and the DC charging station relative to the reference potential is zero, and then it is opened again, and / or the protective switch is closed until the current voltage of the high-voltage potential of the DC-DC converter arranged between the DC-DC converter and the high-voltage battery relative to the reference potential is equal to the voltage difference between the voltage of the high-voltage potential of the DC-DC converter arranged between the DC-DC converter and the high-voltage battery relative to the reference potential before human body contact and the voltage of the high-voltage potential of the DC-DC converter arranged between the DC-DC converter and the DC charging station relative to the reference potential before human body contact, and then it is opened again.

[0013] Alternatively or additionally, it is designed that if it is determined that human 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 between the DC-DC converter and the DC charging station relative to the reference potential exceeds a specified threshold value just before human body contact, at least one protection switch of another protection circuit is closed, and the protection circuit 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 interface.

[0014] In particular, the rising slope is compared with a specified threshold value, wherein in particular it is determined whether the threshold value is undershot or exceeded and thus whether a human body contact has occurred between the DC-DC converter and the DC charging station.

[0015] In particular, it is designed to connect at least one resistor between the high voltage potential and the reference potential in which the DC-DC converter is arranged by closing the corresponding protection switch, that is, the protection circuit of the protection device and / or another protection circuit has at least this resistor. In addition, the protection circuit of the protection device and / or another protection circuit may also have other components. The protection circuit is particularly designed as described in DE 10 2019 008 833 A1, DE 10 2021 003 834 and / or DE 10 2021 003 835.

[0016] With the solution described, the correct functioning of the protection device and its protection circuit can still be ensured if the high-voltage on-board electrical system has a galvanically coupled DC-DC converter and the human body contact with the high-voltage potential in which the DC-DC converter is arranged occurs at position P2, i.e. between the DC-DC converter and the DC charging station. In this way, a rapid discharge of the Y capacitor can also be ensured in this case, thereby preventing the person from receiving an electric shock of dangerous intensity.

[0017] In the solution described, the voltage measurement of the high voltage potential is observed in particular relative to a reference potential. By differentiating the voltage (derivative), the initial voltage can be determined on the basis of the change in the voltage rise slope. Based on the initial voltage, it can then be determined by comparison with a threshold value whether the human body contact and the human body discharge occurred on the primary side or the secondary side of the DC-DC converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Embodiments of the present invention are explained in more detail below with reference to the accompanying drawings.

[0019] In the attached figure:

[0020] Figure 1 A vehicle coupled to a DC charging station is schematically shown. DETAILED DESCRIPTION

[0021] Figure 1 A vehicle 2 coupled to a DC charging station 5 is schematically shown. The vehicle 2 has a high-voltage onboard electrical system 3, which has high-voltage potentials HV+, HV-, namely a positive potential HV+ and a negative potential HV-, and a reference potential M, in particular a ground or earth potential. In addition, the high-voltage onboard electrical system 3 has a protective device 8 to protect a human body MK when a human body comes into contact with one of the high-voltage potentials HV+, HV- and the reference potential M while the DC charging station 5 is charging the high-voltage battery 6. In a state coupled to the DC charging station 5, the high-voltage onboard electrical system 3 forms a DC power grid 1 therewith. The high-voltage battery 6 of the vehicle 2 charged at the DC charging station 5 is used in particular to provide electrical energy to at least one electric drive unit of the vehicle 2 in order to drive the vehicle 2.

[0022] Both in the vehicle 2 and in the DC charging station 5, Y capacitors CyF+, CyF-, CyL+, CyL- are used as a measure to reduce EMC interference (EMC=Electromagnetic Compatibility). In particular, compared with inductive noise filters, such as common-mode inductors or differential-mode inductors, Y capacitors CyF+, CyF-, CyL+, CyL- are in most cases a more cost-effective and compact EMC filtering measure. Therefore, from an EMC point of view, large-capacitance Y capacitors CyF+, CyF-, CyL+, CyL- should be used.

[0023] However, for an electrified vehicle 2, i.e. an electric vehicle or a hybrid vehicle, the disadvantage is that if the vehicle user has access to the high voltage potential HV+, HV- and at the same time is connected to the ground potential, he will feel the capacitance of the Y capacitors CyF+, CyF-, CyL+, CyL-. He will then receive an electric shock. Depending on the intensity of this shock, this can be a threat to health. For example, it can cause ventricular fibrillation or death. Such electric shocks belong to so-called "simple faults" and should be avoided. Therefore, this capacitance of the Y capacitors CyF+, CyF-, CyL+, CyL- is limited by standards to prevent a threat to the vehicle user.

[0024] Therefore, from the perspective of high-voltage safety, a smaller capacitance value of the Y capacitor CyF+, CyF-, CyL+, and CyL- is advantageous. As a regulatory standard, for example, the provisions in the regulation LV123 require that the maximum capacitance of the Y capacitor CyF+, CyF-, CyL+, and CyL- must not be exceeded, especially 0.2J, or so-called "alternative measures" such as reinforced insulation should be arranged. However, this will result in that when two high-voltage systems (for example, vehicle 2 and DC charging station 5) are coupled, if reinforced insulation is selected as the "alternative measure", both must always have this reinforced insulation at the same time. However, this cannot be guaranteed at present.

[0025] In other standards, such as IEC 1772, IEC 60479-1 and IEC60479-2, the capacitance of the Y capacitors CyF+, CyF-, CyL+, CyL- is not referred to as a quantity that is hazardous to health and must not be exceeded, but rather the charge that must not exceed a specified value is referred to as a destructive mechanism. For example, a diagram is described for this purpose, showing the relationship between the value of the human body current and the duration of the human body current. Alternative approaches, such as reinforced insulation, are not accepted here.

[0026] Figure 1The circuit structure of an embodiment of the high-voltage on-board electrical system 3 during the DC charging process of the vehicle 2 is shown. The high-voltage on-board electrical system 3 of the vehicle 2 is coupled to the DC charging station 5 by means of the charging line 4. Here, in the example shown, the charging line 4 has been connected to the connection contacts AK+, AK- of the DC charging interface 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. For charging, they will be closed.

[0027] On the left is the charging station power supply SQ and the charging station internal resistance R LS And a DC charging station 5 of Y capacitors CyL+, CyL-.

[0028] On the right side thereof a charging cable 4 is shown.

[0029] On the right side, a vehicle 2 is shown with a high-voltage onboard electrical system 3, including charging contactors LS+, LS-, Y capacitors CyF+, CyF-, such as EMC filters, X capacitors Cx of an intermediate DC circuit, and a high-voltage battery 6 with main contactors HS+, HS-. The high-voltage battery 6 is shown as a battery power source 7, including, for example, a plurality of single cells connected in series and / or in parallel and a battery internal resistor R Batt .

[0030] Furthermore, the circuit diagram shows a human body MK, which has a human body resistance R K And a switch icon IF indicating an insulation fault, for example when the charging line 4 is damaged, here taking the fault on the positive potential HV+ as an example. The insulation fault IF may also occur on the negative potential HV-. This is not shown here. When an insulation fault IF occurs, the switch icon is closed. When such an insulation fault IF occurs and the human body MK contacts one of the high voltage potentials HV+, HV- and the ground potential M, discharge occurs through the human body MK.

[0031] In order to avoid discharge through the human body MK, or at least reduce it to an acceptable level, especially in terms of health damage, the protection device 8 is designed with a protection circuit 9 to reduce the electric shock caused by the Y capacitors CyF+, CyF-, CyL+, and CyL-. The protection device 8 has a first voltage measuring device SV1 located between the positive potential line HV+L and the reference potential line ML, which is used to measure the voltage between the positive potential line HV+L and the reference potential line ML, that is, the positive potential HV+ and the reference potential M, especially the ground potential, especially the grounding of the body frame, and a second voltage measuring device SV2 located between the negative potential line HV-L and the reference potential line ML, which is used to measure the voltage between the negative potential line HV-L and the reference potential line ML, that is, the negative potential HV- and the reference potential M, especially the grounding potential, especially the grounding of the body frame. The voltage measuring device, especially the voltage measuring devices SV1 and SV2, will actuate the corresponding protection switches SS1 and SS2 when at least one specified triggering criterion occurs. The protection switches SS1 and SS2 are designed as semiconductor switches, such as MOSFETs, for example. Thus, a discharge network is connected between the positive potential HV+ and the reference potential M, in particular the vehicle frame ground, or between the negative potential HV- and the reference potential M, in particular the vehicle frame ground. In the example shown, these discharge networks are protection circuit parts 9.1, 9.2 of the protection circuit 9.

[0032] Each discharge network (i.e., each protection circuit part 9.1, 9.2) comprises at least one resistor, through which the Y capacitors CyF+, CyF-, CyL+, CyL- are discharged. In the example shown, each discharge network preferably consists of uncharged capacitors, hereinafter referred to as protection capacitors Cs1, Cs2, and parallel resistors, hereinafter referred to as discharge resistors Re1, Re2. In addition, protection resistors Rs1, Rs2 are provided, which are connected in series with the protection capacitors Cs1, Cs2. For example, it is also possible to provide only discharge resistors Re1, Re2.

[0033] So far, the high-voltage onboard electrical system 3 together with the protective device 8 corresponds to that described in DE 10 2019 008 833 A1. Therefore, for more information on its structure and functional principle, refer to DE 10 2019 008 833 A1, especially the drawings and the description of the drawings therein. Other examples of such high-voltage onboard electrical systems 3 with protective devices 8 are described in DE 10 2021 003 834 and DE 10 2021 003 835. They differ mainly in the structure of the protective device, especially the components of the discharge network.

[0034] For the solution described below, the protection device 8 described in DE 10 2019 008 833 A1, DE 10 2021 003 834 and DE 10 2021 003 835 and its specific functional principle for the high-voltage on-board electrical system 3 of the vehicle 2 can be used, namely Figure 1 The protective device 8 shown in can also be designed as an alternative to the embodiments described in DE 10 2019 008 833 A1, DE 10 2021 003 834 and DE 10 2021 003 835 and function as described therein.

[0035] The main difference of the high-voltage on-board electrical system 3 shown here with respect to the high-voltage on-board electrical system 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 on-board electrical system 3 of the vehicle 2 shown and described here, a galvanically coupled DC-DC converter GW is arranged between one of the high-voltage potentials HV+, HV-, in the example shown here the high-voltage potential HV+, and the DC charging interface of the vehicle 2. 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 the rated voltage of the high-voltage battery 6. The DC charging station 5 shown is such a DC charging station 5.

[0036] If an insulation fault IF and the human body contact mentioned above occur between one of the high-voltage potentials HV+, HV- and the reference potential M, between the DC-DC converter GW and the DC charging station 5 and the high-voltage potential in which the DC-DC converter GW is arranged, the DC-DC converter GW will affect the action of the protection device 8. In the example shown here, the 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-, and is then related to the negative potential HV-. Between the DC-DC converter GW and the DC charging station 5, this human body contact position with the high-voltage potential in which the DC-DC converter GW is arranged and which is very critical for the action of the protection device 8 will be referred to as position P2 below.

[0037] Other locations where human contact between one of the high-voltage potentials HV+, HV- and the reference potential M may occur include another high-voltage potential, in the example shown, the negative potential HV-, hereinafter referred to as location P1, and a high-voltage potential between the DC-DC converter GW and the high-voltage battery 6, in which the DC-DC converter GW is arranged, hereinafter referred to as location P3. In these two other locations P1 and P3, human contact is also not dangerous for the protective device 8, in particular for its functional principle and mode of action, when a galvanically coupled DC-DC converter GW is used in the high-voltage on-board electrical system 3 of the vehicle 2. Thus, if human contact with one of the high-voltage potentials HV+, HV- occurs in one of the two locations P1, P3, the protective device 8 continues to operate as described in DE 10 2019 008 833 A1, DE 10 2021 003 834 or DE 10 2021 003 835, in particular as described in the drawings and the description of the drawings, and in the process achieves the same effects as described therein.

[0038] If human body contact occurs at position P3, that is, between the DC-DC converter GW and the high-voltage battery 6, the voltage between the high-voltage potential connected by the human body MK and the reference potential M is reduced to 0V at position P3 by means of the protective device 8. At position P2, the voltage drop between the high-voltage potential and the reference potential M is the same as the voltage value at position P3. Since at position P2, the initial voltage between the high-voltage potential and the reference potential M reduces the voltage value of the DC-DC converter GW, as a final value, a significantly reduced voltage, or even a negative voltage, is also caused. However, since the human body contact does not occur at position P2, but at position P3, this is not important. When the human body contact occurs at position P3, the voltage is quickly reduced. As described in DE 102019 008 833 A1, DE 10 2021 003 834 or DE 10 2021 003 835, the functional principle of the protective device is favorable for human body contact at position P3, so for human body contact at position P3, it is also retained in the solution described here.

[0039] If human contact occurs at position P2, i.e., between the DC-DC converter GW and the DC charging station 5, then at position P3, the voltage between the high voltage potential connected by the human body MK and the reference potential M will only decrease by a small value, more precisely, the voltage between the high voltage potential and the reference potential M at position P2 will be reduced. At position P2, the voltage between the high voltage potential and the reference potential M will decrease to 0V on the capacitor discharge curve. As described in DE 10 2019 008 833 A1, DE 10 2021003 834 or DE 10 2021 003 835, switching on the protection circuit 9 of the protection device 8 at position P3 will immediately reduce the voltage at position P3 to 0V. The consequence is that from the moment of switching on, at position P2, the voltage between the high voltage potential connected by the human body MK and the reference potential M will decrease by the voltage value present at position P3 at the moment of switching on. Due to the sign change, since the initial voltage at position P2 is lower than that at position P3, the voltage value at position P2 will subsequently increase, which may lead to even greater danger than when the protection circuit 9 of the protection device 8 is not switched on.

[0040] If human body contact occurs at position P1, that is, at a high voltage potential where no DC-DC converter GW is arranged, in the example shown here, at the negative potential HV-, the voltage between the high voltage potential connected by the human body MK and the reference potential M is reduced to 0V at position P1 by means of the protective device 8. The voltage between the other high voltage potential and the reference potential M will increase by the same value whether at position P2 or position P3. However, since the contact of the human body MK occurs at position P1 in this case, this is not important because the voltage will drop rapidly here. As described in DE 10 2019 008 833 A1, DE 10 2021 003 834 or DE 10 2021 003 835, the functional principle of the protective device is favorable for human body contact at position P3, and therefore, for human body contact at position P3, it is also retained in the solution described here.

[0041] Thus, based on the above description, it can be seen that it is necessary to distinguish whether the human body MK is in 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 human body MK is in contact with the high voltage potential in which the DC-DC converter GW is arranged at position P2, because a functional principle of the protection device 8 (especially the protection circuit 9) different from that described in DE 10 2019 008 833 A1, DE 10 2021 003 834 or DE 10 2021 003 835 is required.

[0042] Therefore, the solution described here is designed to determine whether the human body contact with the high voltage potential in which the DC-DC converter GW is arranged is between the DC-DC converter GW and the DC charging station 5, that is, whether the human body contact is at the position P2. Since the identification of the corresponding positions P1, P2, P3 (especially the position P2) must be carried out very quickly so that the protection device 8 (especially its protection circuit 9) takes correct action, it is not possible to wait for the discharge curve to stabilize, that is, the capacitor discharge e function of the Y capacitor CyF+, CyF-, CyL+, CyL-to stabilize.

[0043] The distinguishing feature used for the solution described here is the rising slope of the discharge curve, i.e. the derivative of the discharge curve. In this way, it is determined whether a human body contact has taken place between the DC-DC converter GW and the DC charging station 5 based on the rising slope of the voltage measured between the high voltage potential and the reference potential M in which the DC-DC converter GW is arranged. In this case, the voltage is measured by means of a voltage measuring device designated for measuring the voltage between the high voltage potential and the reference potential M, in the example shown here, by means of a first voltage measuring device SV1.

[0044] For the high voltage potential in which the DC-DC converter GW is arranged, the grid equation applies, so here for the positive potential HV+:

[0045] U P3 (t) = U Gw +U P2 (t) (1)

[0046] in

[0047] U P3 (t) is the voltage between the high voltage potential, here the positive potential HV+, in which the DC-DC converter GW is arranged, and the reference potential M at the position P3,

[0048] U P2 (t) is the voltage between the high voltage potential, here the positive potential HV+, in which the DC-DC converter GW is arranged, and the reference potential M at the position P2,

[0049] U GW is the voltage of the DC-DC converter GW.

[0050] The human body discharge at position P3 has the following variation curve relative to position P3:

[0051]

[0052] And for its rising slope (derivative):

[0053]

[0054] The human body discharge at position P2 has the following variation curve relative to position P3:

[0055]

[0056] And for its rising slope (derivative):

[0057]

[0058] U 0P3 and U 0P2 This corresponds to the high voltage potential in which the DC-DC converter GW is arranged, in this case the positive potential HV+, relative to the reference potential M, at the position P3 or P2 immediately before the human body discharge occurs. R is the human body resistance R K , and C is the total capacitance of the Y capacitors CyF+, CyF-, CyL+, CyL- to be discharged.

[0059] By observing the two derivatives, we can derive the relationship between the difference in the rising slope and the contact position of the human body. When contact is made at position P3, the derivative formula (Formula (3)) contains the coefficient U 0P3 , while when contact is made at position P2, the derivative (formula (5)) contains the coefficient U 0P2 .

[0060] Therefore, the location of human contact can be immediately identified by means of the rising slope, and then the protection device 8, in particular its protection circuit 9, can also be immediately operated correctly. For this purpose, the determined rising slope is compared in particular with at least one specified threshold value. In particular, it is determined whether the threshold value is undershot or exceeded. Through this comparison, it is determined whether human contact occurs at position P2.

[0061] The rise slope (derivative) can be determined, for example, by means of a capacitor circuit, an operational amplifier (differentiator) or by repeated detection, ie measuring the voltage by means of the relevant, here first, voltage measuring device SV1 , and calculation.

[0062] Next, the response options of the protective device 8 will be described for human contact determined at each position P1, P2, and P3, or especially when it is determined that human contact occurs at position P2, because if human contact occurs at positions P1 and P3, that is, it is not determined that human contact occurs at position P2, the high voltage potential involved will be short-circuited / quickly discharged with the help of the protective device 8 and its protective circuit 9 by the method described in DE 10 2019 008 833A1 and / or DE 10 2021 003 834 and / or DE 10 2021 003 835.

[0063] Here, the main difference from DE 10 2019 008 833 A1, DE 10 2021 003 834 and DE 10 2021 003 835 is that it is determined whether human contact occurs at position P2, and if this is the case, other actions are taken. Therefore, the triggering criterion of the protection circuit 9 for triggering human contact positions P1, P2, P3 is increased, that is, for closing at least one or two protection switches SS1, SS2, and in particular, the triggering criterion of whether human contact occurs at position P2 is increased, or the triggering criterion of human contact occurs at position P2. As described above, this triggering criterion, that is, its existence, is determined here in particular according to the rising slope of the voltage between the high voltage potential, in the example shown here, the positive potential HV+, and the reference potential M over time t, in particular according to formula (5).

[0064] If it is determined from this that the human body contact with the high voltage potential, in the example shown, the positive potential HV+, in which the DC-DC converter GW is arranged, occurs between the DC-DC converter GW and the DC charging station 5 (i.e., at position P2), then there are several options for the functional principle of the protection device 8 (in particular its protection circuit 9) to be implemented next:

[0065] - If the voltage does not threaten personnel, the value of Y capacitor CyF+, CyF-, CyL+, CyL- is U 0P2 If the conversion of electric quantity does not lead to exceeding a specified, especially legally specified, threshold value, no action is performed by the protection device 8. If the voltage U of the high voltage potential of the DC-DC converter GW relative to the reference potential M is arranged between the DC-DC converter GW and the DC charging station 5 (i.e., at position P2), then the protection device 8 will not perform any action. 0P2 If the specified threshold is not exceeded before human body contact, the protection switches SS1 and SS2 will not be closed.

[0066] - The high voltage potential of the DC-DC converter GW is arranged therein, in the example shown here, the positive potential HV+, which is discharged at position P3 relative to the reference potential M, and the specific voltage value of the discharge is U 0P2 , i.e., the voltage value of the high voltage potential of the DC-DC converter GW disposed between the DC-DC converter GW and the DC charging station 5 (i.e., at position P2) relative to the reference potential M immediately before human body contact. This can be done, for example, by closing the protective switch involved, here the first protective switch SS1, and opening it again. Here, for example, once the voltage between the high voltage potential of the DC-DC converter GW disposed at position P3 and the reference potential M is U 0P3 -U 0P2, that is, the voltage corresponds to the voltage U between the DC-DC converter GW and the DC charging station 5 (ie, at the position P2) in which the DC-DC converter GW is arranged relative to the reference potential M. 0P2 At the same time, the high voltage potential of the DC-DC converter GW arranged between the DC-DC converter GW and the high voltage battery 6 (i.e., at position P3) is relative to the reference potential M, and the voltage U immediately before the human body contacts the DC-DC converter GW is 0P3 As an alternative, for example, if at position P2, i.e., in 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, the voltage between the high voltage potential and the reference potential M is 0V, for example, disconnection will be performed. In particular, when U 0P2 If the voltage of the high voltage potential of the DC-DC converter GW arranged between the DC-DC converter GW and the DC charging station 5 (i.e., at position P2) exceeds a specified threshold value relative to the reference potential M before human body contact, at least the protective switch SS1 will be closed between the high voltage potential of the DC-DC converter GW arranged therein and the reference potential M until the current voltage of the high voltage potential of the DC-DC converter GW arranged between the DC-DC converter GW and the DC charging station 5 relative to the reference potential M is zero, and then it will be disconnected again, and / or until the current voltage of the high voltage potential of the DC-DC converter GW arranged between the DC-DC converter GW and the high-voltage battery 6 relative to the reference potential M is equal to the voltage difference between the voltage of the high voltage potential of the DC-DC converter GW arranged between the DC-DC converter GW and the high-voltage battery 6 relative to the reference potential M before human body contact and the voltage of the high voltage potential of the DC-DC converter GW arranged between the DC-DC converter GW and the DC charging station 5 relative to the reference potential M before human body contact, and then it will be disconnected again.

[0067] For both options according to the two examples above, it is necessary to know as accurately as possible the high voltage potential between the DC-DC converter GW and the DC charging station 5 (i.e., at position P2) in which the DC-DC converter GW is arranged relative to the reference potential M immediately before the human body contacts U. 0P2 The voltage can be adjusted according to the DC-DC converter GWU 0P2 The conversion ratio of , and the voltage U measured by the corresponding voltage measuring device (here the first voltage measuring device SV1) between the DC-DC converter GW and the high-voltage battery 6 (i.e., at the position P3) in which the DC-DC converter GW is arranged relative to the reference potential M before the human body contacts 0P3This voltage is determined or measured directly at the input of the DC-DC converter GW by means of another voltage measuring device.

[0068] As an alternative to these two options, in particular as an alternative to the second listed option, for example, discharging can also be performed at position P2. For this purpose, another discharge circuit, in particular another discharge network, in particular another protective circuit 9 is required between the high voltage potential and the reference potential in which the DC-DC converter GW is arranged at position P2, that is, between the DC-DC converter GW and the DC charging station 5. In order to realize this option, the high-voltage on-board electrical system 3 has such another discharge circuit, in particular another protective circuit 9, at this position P2. Advantageously, the protective circuit adopts the design as described in DE 10 2019008 833 A1 and / or DE 10 2021 003 834 and / or DE 10 2021 003 835.

[0069] Thus, when using the other protection circuit, especially when the voltage U of the high voltage potential of the DC-DC converter GW disposed between the DC-DC converter GW and the DC charging station 5 (i.e., at position P2) is lowered relative to the reference potential M immediately before the human body contacts the DC-DC converter GW. 0P2 If a specified threshold value is exceeded, at least one protective switch of another protective circuit 9 arranged between the high voltage potential of the DC-DC converter GW and the reference potential M in the region of position P2, i.e. between the DC-DC converter GW and the DC charging interface, is closed.

[0070] In order to better distinguish or to be able to respond more quickly, in addition to the above-mentioned rising slope of the voltage measured between the high voltage potential of the DC-DC converter GW and the reference potential M, other measurement parameters are used, such as the high voltage potential of the DC-DC converter GW, which is the positive potential HV+ in the example shown here, the current value of the voltage measurement determined by the first voltage measuring device SV1 relative to the reference potential M, or its average value in a specified time period. For example, a threshold value or an average value can be specified for the current value of the voltage measurement. If it is lower than the threshold value, and the rising slope value calculated from the voltage measured between the high voltage potential of the DC-DC converter GW and the reference potential M is, for example, less than -1e5, and the protection switch of another protection circuit 9 is in the open state, the protection switch SS1 of the protection circuit 9 will be closed next. If it is lower than the threshold value of the above-mentioned voltage measurement, and the rising slope value calculated from the voltage measured between the high voltage potential of the DC-DC converter GW and the reference potential M is, for example, between -1e4 and -1e5, then, for example, the protection switch of another protection circuit 9 will be closed. Furthermore, the first protection switch SS1 of the protection circuit 9 is not allowed to be in the closed state.

[0071] Thus, for the solution, the positions P1, P2, P3 of the human body contact can be derived from the rising slope of the discharge curve, and then the protection device 8 can respond correctly. The 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. Here, the galvanically coupled DC-DC converter GW can also be used to supply power to auxiliary units, for example. The solution can also be used for a DC charging station 5 composed of a galvanically coupled DC-DC converter and / or a battery and a galvanically coupled converter.

[0072] Reference numerals list

[0073] 1 DC grid

[0074] 2 Vehicles

[0075] 3 High-voltage on-board electrical system

[0076] 4 Charging cable

[0077] 5 DC Charging Stations

[0078] 6 High voltage battery

[0079] 7 Battery Energy Source

[0080] 8 Protective devices

[0081] 9 Protection Circuit

[0082] 9.1, 9.2 Protection circuit part

[0083] AK+, AK- DC charging interface connection contacts

[0084] Cs1, Cs2 protection capacitors

[0085] Cx X capacitor

[0086] CyF+, CyF- Y capacitors for vehicles

[0087] CyL+, CyL- Y capacitors for DC charging stations

[0088] GW DC-DC Converters

[0089] HS+, HS- Main contactor

[0090] HV+ Positive potential

[0091] HV - Negative electrode potential

[0092] HV+L Positive potential line

[0093] HV-L Negative potential line

[0094] IF insulation fault

[0095] LS+, LS- Charging contactor

[0096] M Reference potential

[0097] ML reference potential line

[0098] MK Human Body

[0099] P1, P2, P3 positions

[0100] R Batt Battery internal resistance

[0101] R K Human body resistance

[0102] R LS Charging station internal resistance

[0103] Re1, Re2 discharge resistor

[0104] Rs1, Rs2 protection resistors

[0105] SQ Charging Station Power Supply

[0106] SS1, SS2 protection switch

[0107] SV1, SV2 voltage measuring device

Claims

1. A method for operating a high-voltage on-board electrical system (3) of a vehicle (2), the high-voltage on-board electrical system having a protective device (8) for protecting a human body (MK) when the human body (MK) comes into contact with one of the high-voltage potentials (HV+, HV-) and a reference potential (M) during charging of a high-voltage battery (6) via a DC charging station (5) connected to the vehicle (2) via a charging line (4), wherein: The protection device (8) comprises a voltage measuring device (SV1, SV2) and a protection circuit (9) having a protection switch (SS1, SS2) between the corresponding high voltage potential (HV+, HV-) and the reference potential (M). It is characterized in that In one of the high-voltage potentials (HV+, HV-) of the high-voltage onboard electrical system (3) of the vehicle (2), a current-coupled DC-DC converter (GW) is arranged between the protection device (8) and the DC charging interface of the vehicle (2), and The charging voltage provided by the DC charging station (5) is lower than the rated voltage of the high-voltage battery (6), wherein it is determined whether human 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), To this end, this is determined based on the rising slope of the voltage measured between the high voltage potential (HV+, HV-) in which the DC-DC converter (GW) is arranged and the reference potential (M), and It is used as a triggering criterion for actuating the protection circuit (9) and / or another protection circuit (9), wherein the other protection circuit (9) is arranged between the high voltage potential (HV+, HV-) of the DC-DC converter (GW) and the reference potential (M) at a position between the DC-DC converter (GW) and the DC charging interface.

2. The method according to claim 1, It is characterized in that When it is determined that human 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), then - if the voltage of the high voltage potential (HV+, HV-) between the DC-DC converter (GW) and the DC charging station (5) in which the DC-DC converter (GW) is arranged relative to the reference potential (M) does not exceed a specified threshold value immediately before human body contact, the protection switch (SS1, SS2) is not closed, - If the voltage of the high voltage potential (HV+, HV-) between the DC-DC converter (GW) and the DC charging station (5) in which the DC-DC converter (GW) is arranged relative to the reference potential (M) exceeds a specified threshold value before human body contact, at least the protection switch (SS1, SS2) between the high voltage potential (HV+, HV-) and the reference potential (M) in which the DC-DC converter (GW) is arranged is closed until the current voltage of the high voltage potential (HV+, HV-) between the DC-DC converter (GW) and the DC charging station (5) in which the DC-DC converter (GW) is arranged relative to the reference potential (M) is zero, and then disconnected again, and / or until the current voltage of the high voltage potential (HV+, HV-) between the DC-DC converter (GW) and the high-voltage battery (6) in which the DC-DC converter (GW) is arranged relative to the reference potential (M) is equal to the current voltage of the high voltage potential (HV+, HV-) between the DC-DC converter (GW) and the DC charging station (5) in which the DC-DC converter (GW) is arranged relative to the reference potential (M). - a voltage difference between a voltage of the high voltage potential (HV+, HV-) of the DC-DC converter (GW) between the DC-DC converter (GW) and the high voltage battery (6) immediately before human body contact with the reference potential (M) and a voltage difference between a voltage of the high voltage potential (HV+, HV-) of the DC-DC converter (GW) between the DC-DC converter (GW) and the DC charging station (5) immediately before human body contact with the reference potential (M), and then disconnected again, and / or - At least one protection switch of the other protection circuit (9) is closed, in which the other protection circuit is arranged between the high voltage potential (HV+, HV-) of the DC-DC converter (GW) and the reference potential (M) at a position between the DC-DC converter (GW) and the DC charging interface.

3. The method according to claim 1 or 2, It is characterized in that The rising slope is compared with a specified threshold value, wherein in particular it is determined whether the threshold value is undershot or exceeded, and then it is determined whether human body contact has occurred between the DC-DC converter (GW) and the DC charging station (5).

4. The method according to any one of the preceding claims, It is characterized in that By closing the corresponding protection switch (SS1, SS2), at least one 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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