Protection device for DC power grid, vehicle-mounted power supply for vehicle, vehicle and DC charging station

Abstract

The present invention relates to a protection device (8) for a DC power grid (1), in particular a high-voltage power grid. According to the present invention, the protection device (8) comprises: a first voltage measuring device (SV1) between the positive potential line (HV+L) and the reference potential line (ML) and a second voltage measuring device (SV2) between the negative potential line (HV-L) and the reference potential line (ML), or a fault current measuring device (10) in the reference potential line (ML); and a protection circuit (9) having two protection circuit parts (9.1, 9.2), wherein the first protection circuit part (9.1) comprises a series circuit consisting of a first discharge resistor (Re1) and a first protection switch (SS1) between the positive potential line (HV+L) and the reference potential line (ML), the second protection circuit part (9.2) comprises a series circuit consisting of a second discharge resistor (Re2) and a second protection switch (SS2) between the negative potential line (HV-L) and the reference potential line (ML), and wherein the first and second protection switches (SS1, SS2) can be driven to close when a specified voltage value is determined to be lower and / or higher by means of the first and / or second voltage measuring devices (SV1, SV2), or the first and / or second protection switches (SS1, SS2) can be driven to close when a fault current is measured by means of the fault current measuring device (10).

Description

Field of the Invention

[0001] The present invention relates to a protection device for a DC power grid according to the preamble of claim 1, a vehicle on-board power supply, a vehicle, and a DC charging station. Background Art

[0002] A method for operating an on-board power supply is known from the prior art as described in DE 10 2017 009 355 A1. In a method for operating a first on-board power supply supplied with a first DC voltage and a second on-board power supply supplied with a second DC voltage, the first and second on-board power supplies are electrically coupled by means of an energy coupler having a first beat transducer. The first and second DC voltages are electrically isolated from a reference potential by means of an electrical isolation mechanism. The electrical isolation mechanism is monitored. The first and second on-board power supplies are current-coupled by means of the energy coupler. When an isolation mechanism failure occurs in a region of one of the two on-board power supplies, the energy coupler controls the potential of the corresponding other on-board power supply of the two on-board power supplies such that the potential difference between this potential and the corresponding potential of the reference potential is less than a predetermined comparison value.

[0003] DE 10 2017 009 352 A1 describes an energy coupler for electrical coupling of on-board power supplies and a method for electrical coupling of on-board power supplies. The energy coupler for electrically coupling a first on-board power supply supplied with a first DC voltage to a second on-board power supply supplied with a second DC voltage has a first beat transducer and a second beat transducer. The first and second beat transducers each have an on-board power supply terminal and an intermediate circuit terminal. The on-board power supply terminal of the first beat transducer is connected to the first on-board power supply, and the on-board power supply terminal of the second beat transducer is connected to the second on-board power supply. The intermediate circuit terminals of the first and second beat transducers are connected to a common DC voltage intermediate circuit. A first potential of the DC voltage intermediate circuit is electrically connected to one of the potentials of the first on-board power supply by means of the first beat transducer, and a second potential of the DC voltage intermediate circuit is electrically connected to one of the potentials of the second on-board power supply by means of the second beat transducer. Summary of the Invention

[0004] It is therefore an object of the present invention to provide a protection device for a DC power grid that is improved compared to the prior art, an on-board power supply for a vehicle that is improved compared to the prior art, a vehicle having such an on-board power supply, and a DC charging station that is improved compared to the prior art.

[0005] According to the present invention, this object is achieved by a protection device for a DC grid having the features of claim 1, a vehicle on-board power supply having the features of claim 7, a vehicle having the features of claim 8, and a DC charging station having the features of claim 9.

[0006] Advantageous designs of the present invention are the subject matter of the dependent claims.

[0007] The protection device according to the present invention for a DC grid, in particular a high-voltage grid such as a vehicle on-board power supply, includes a first voltage measuring device for measuring the voltage between a positive potential line and a reference potential line between the positive potential line and the reference potential line and a second voltage measuring device for measuring the voltage between the negative potential line and the reference potential line between the negative potential line and the reference potential line. The reference potential is in particular the ground potential, in particular the vehicle ground potential when using the protection device in a vehicle, and for example the ground potential when using the protection device in a DC charging station.

[0008] In addition, the protection device includes a protection circuit. The protection circuit includes, for example, a series circuit of a discharge resistor and a first protection switch between the positive potential line and the reference potential line and a series circuit of a discharge resistor and a second protection switch between the negative potential line and the reference potential line. Alternatively, the protection circuit includes two protection circuit portions, wherein the first protection circuit portion includes a series circuit of a first discharge resistor and a first protection switch between the positive potential line and the reference potential line, and the second protection circuit portion includes a series circuit of a second discharge resistor and a second protection switch between the negative potential line and the reference potential line.

[0009] In both variants of the protection circuit of the protection device, the first protection switch can be controlled to turn off when a voltage lower than a predetermined voltage is determined by means of the first voltage measuring device, and the second protection switch can be controlled to turn off when a voltage lower than a predetermined voltage value is determined by means of the second voltage measuring device.

[0010] Alternatively, the first protection switch can be controlled to turn off when a voltage higher than a predetermined voltage value is determined by means of the second voltage measuring device, and the second protection switch can be controlled to turn off when a voltage higher than a predetermined voltage value is determined by means of the first voltage measuring device.

[0011] Instead of two voltage measuring devices, a fault current measuring device can be provided in the reference potential line. Then, in both variants of the protection circuit, the first protection switch and / or the second protection switch can be controlled to turn off when a fault current is measured by means of the fault current measuring device.

[0012] The vehicle on-board power supply according to the present invention for a vehicle, in particular an electric vehicle or a hybrid vehicle, in particular a high-voltage power supply, includes such a protection device.

[0013] A vehicle according to the invention, in particular an electric vehicle or a hybrid vehicle, comprises such a protection device, in particular such an on-vehicle power supply, in particular a high-voltage on-vehicle power supply, having such a protection device.

[0014] A DC charging station according to the invention, in particular an off-vehicle DC charging station, in particular for charging the high-voltage battery of a vehicle, in particular an electric vehicle or a hybrid vehicle, and in particular such a vehicle, comprises such a protection device.

[0015] The term "high voltage" in particular refers to a DC voltage which is in particular greater than approximately 60 V. In particular, the term "high voltage" is designed to comply with standard ECE R 100.

[0016] The solution according to the invention solves the problems associated with Y capacitors in vehicles, in particular electric vehicles and hybrid vehicles, and in DC charging stations, as explained below. Such Y capacitors are used as a measure to reduce the emission of EMC interference (EMC: electromagnetic compatibility). However, they are at a higher dangerous potential for high-voltage safety considerations. For example, according to standards SAE J1772, IEC 60479-1 and -2, the charge quantity contained in the Y capacitor is referred to as a health threat characteristic (C1 characteristic curve). As the operating voltage of the vehicle increases, it becomes increasingly difficult to comply with the limit values required by this standard. Sometimes, alternative measures, so-called alternative countermeasures, for complying with safety regulations such as enhanced, in particular doubled, electrical insulation are also not permitted. Another standard, LV123, and related standards, for example, specify a maximum internal energy of 0.2 J for the charge quantity of all Y capacitors. When an escape route via alternative measures is permitted, then, for example, the enhanced, in particular doubled, electrical insulation described above can be used. But this can only be achieved when all interconnected high-voltage systems are correspondingly strengthened in terms of isolation. That is, for example, during DC charging, the vehicle and the DC charging station, in particular the charging pile, must be correspondingly enhanced in terms of insulation. But since there is no mandatory standard for this, it is also possible to connect systems with different insulation designs, thereby not complying with the safety requirements.

[0017] The problem is solved by the invention in that by measuring the voltage of a high voltage potential relative to a reference potential, in particular the ground potential, a drift of the high voltage potential caused by body currents (i.e., because the body, in particular the human body, touches one of the high voltage potential and the reference potential) with respect to the reference potential is identified. In order to reduce the voltage as quickly as possible at the relevant high voltage potential that decreases to the reference potential, a discharge resistor is connected and advantageously a non-charged protection capacitor is connected electrically in parallel therewith. The voltage between the relevant high voltage potential and the reference potential thus jumps to a much lower level, whereby the body current decreases proportionally to the voltage. The solution according to the invention thus allows a reduction of the electric shock caused by the Y capacitor to the body, in particular the human body. Thus, the above requirements can be complied with. It is also possible to limit the electrical energy realized by the human body resistance of the Y capacitor to less than 0.2 J, although the energy stored in the Y capacitor can be much higher.

[0018] Advantageously, a protection capacitor is electrically connected in parallel with the discharge resistor as described above. The discharge resistor only needs to have a very low ohmic value to quickly reduce the body current. However, disadvantageously, a low ohmic insulation defect is thus generated. Therefore, the combination consisting of the discharge resistor and the electrically parallel protection capacitor is much more advantageous. The discharge resistor ensures that the electrically parallel protection capacitor has no voltage at the moment of switching on. After switching on, it is used for the rapid discharge of the Y capacitor of the relevant high voltage potential.

[0019] Thus, the protection circuit includes, for example, a series circuit of a discharge resistor and a first protection switch between the positive potential line and the reference potential line and a series circuit of a discharge resistor and a second protection switch between the negative potential line and the reference potential line, wherein the protection capacitor is electrically connected in parallel with the discharge resistor. Alternatively, the protection circuit includes two protection circuit portions, wherein the first protection circuit portion includes a series circuit of a first discharge resistor and a first protection switch between the positive potential line and the reference potential line, wherein a first protection capacitor is electrically connected in parallel with the first discharge resistor, and wherein the second protection circuit portion includes a series circuit of a second discharge resistor and a second protection switch between the negative potential line and the reference potential line, wherein a second protection capacitor is electrically connected in parallel with the second discharge resistor.

[0020] For example, not only is the protection capacitor electrically connected in parallel with the discharge resistor, but a series circuit consisting of the protection capacitor and a protection resistor is also electrically connected in parallel therewith. By means of the protection resistor, the current flowing through the protection capacitor is advantageously limited.

[0021] Therefore, the protection circuit includes, for example, a series circuit of a discharge resistor and a first protection switch between the positive potential line and the reference potential line, and a series circuit of a discharge resistor and a second protection switch between the negative potential line and the reference potential line, wherein a series circuit formed by the protection capacitor and the protection resistor is electrically parallel to the discharge resistor. Alternatively, the protection circuit includes these two protection circuit portions, wherein the first protection circuit portion includes a series circuit of a first discharge resistor and a first protection switch between the positive potential line and the reference potential line, wherein a series circuit formed by the first protection capacitor and the first protection resistor is electrically parallel to the first discharge resistor, and wherein the second protection circuit portion includes a series circuit formed by a second discharge resistor and a second protection switch between the negative potential line and the reference potential line, wherein a series circuit formed by the second protection resistor and the second protection capacitor is electrically parallel to the second discharge resistor.

[0022] For example, a first voltage evaluation unit is provided in engagement with the first voltage measuring device and the first protection switch, for evaluating the voltage determined by the first voltage measuring device and for controlling the first protection switch when the voltage is below a predetermined voltage limit value, and a second voltage evaluation unit is provided in engagement with the second voltage measuring device and the second protection switch, for evaluating the voltage determined by the second voltage measuring device and for controlling the second protection switch when the voltage is below a predetermined voltage limit value.

[0023] Alternatively, a common voltage evaluation unit is provided, for example, in engagement with the voltage measuring device and the protection switch, for evaluating the voltage determined by the first voltage measuring device and the voltage determined by the second voltage measuring device, and for controlling the first protection switch when the voltage determined by the first voltage measuring device is below a predetermined voltage limit value and for controlling the second protection switch when the voltage determined by the second voltage measuring device is below a predetermined voltage limit value.

[0024] In the case of using a fault current measuring device, correspondingly, a current evaluation unit is provided in engagement with the fault current measuring device and the protection switch, for evaluating the measured fault current and for controlling the first protection switch and / or the second protection switch based on the measured fault current.

[0025] In a possible embodiment, it may be provided that the shared voltage evaluation unit is connected to a third voltage measuring device and a fourth voltage measuring device, wherein the third voltage measuring device is arranged between the positive potential line and the reference potential line to measure the voltage between the positive potential line and the reference potential line, and the fourth voltage measuring device is arranged between the negative potential line and the reference potential line to measure the voltage between the negative potential line and the reference potential line, and wherein a first switching unit is provided in the positive potential line between the connection point with respect to the first voltage measuring device and the connection point with respect to the third voltage measuring device, and a second switching unit is provided in the negative potential line between the connection point with respect to the second voltage measuring device and the connection point with respect to the fourth voltage measuring device. This embodiment is particularly recommended for the high-voltage vehicle power supply of electric vehicles or hybrid vehicles, wherein the first and second switching units are the charging contactors of the high-voltage vehicle power supply, which are closed after being connected to the DC charging station for DC charging. Through the above solution, before the switching unit, i.e., the charging contactor, is closed and thus inevitably associated with an increase in the capacitance of the Y capacitor due to the parallel connection of the DC charging station and the vehicle, it can be determined in advance whether the protection circuit can comply with the legal limit values, for example, when the insulation in the charging cable fails.

[0026] The protection switches are respectively designed as semiconductor switches, such as MOSFET, IGBT or thyristor for example. Brief Description of the Drawings

[0027] Hereinafter, the embodiments of the present invention will be explained in detail with reference to the drawings, wherein:

[0028] Figure 1 Schematically shows an embodiment of a DC power grid with a protection device,

[0029] Figure 2 Schematically shows Figure 1 the working mode of the protection device,

[0030] Figure 3 Schematically shows an alternative protection device,

[0031] Figure 4 Schematically shows another embodiment of a DC power grid with a protection device,

[0032] Figure 5 Schematically shows another embodiment of a DC power grid with a protection device,

[0033] Figure 6 Schematically shows the simulation results of the simulation,

[0034] Figure 7 Schematically shows the simulation results of the simulation,

[0035] Figure 8Schematically shows the simulation results of the simulation

[0036] Figure 9 Schematically shows the protection circuit for component optimization

[0037] Figure 10 Schematically shows the protection device

[0038] Figure 11 Schematically shows the working mode of the protection circuit

[0039] Figure 12 Schematically shows at Figure 11 the voltage and current varying with time in the shown working mode

[0040] Corresponding components carry the same reference numerals in all the figures Detailed implementation manner

[0041] The following describes in conjunction with Figure 1-1 3 the protection device 8 for a DC power grid 1, especially a high-voltage power grid. In the shown example, the high-voltage power grid is the high-voltage on-board power supply 3 of a vehicle 2, especially an electric vehicle or a hybrid vehicle, which preferably employs the protection device 8. However, the protection device 8 can alternatively or additionally also be used in a DC charging station 5, to which the vehicle 2 and other vehicles, especially electric vehicles and hybrid vehicles, can be connected to charge the high-voltage battery 6 of the vehicle 2. The DC power grid 1 then includes, in the connected state of the vehicle 2, the on-board power supply 3 of the vehicle 2, especially the high-voltage on-board power supply 3 and the DC charging station 5. The high-voltage battery 6 of the vehicle 2 charged through the DC charging station 5 is especially used to supply electrical energy to at least one electric drive unit for driving the vehicle 2

[0042] Y capacitors CyF+, CyF-, CyL+, CyL- are applied as a measure in both the vehicle 2 and the DC charging station 5 to reduce the emission of EMC interference (EMC: electromagnetic compatibility). In particular, the Y capacitors CyF+, CyF-, CyL+, CyL- are mostly more advantageous and more compact EMC filtering measures compared to inductive interference filters such as common-mode or differential-mode chokes. Therefore, from the perspective of EMC, it is advantageous to use Y capacitors CyF+, CyF-, CyL+, CyL- with large capacitance values

[0043] However, in an electrified vehicle 2, such as an electric vehicle or a hybrid vehicle, it is disadvantageous that the vehicle user may be subjected to the stored energy of the Y capacitors CyF+, CyF-, CyL+, CyL- when he may come into contact with the high-voltage potentials HV+, HV- and at the same time be connected to the ground potential. He is then electrocuted. Depending on the intensity of the electric shock, it can be health-threatening. For example, it can cause ventricular fibrillation or death. Such an electric shock is a so-called "direct fault" and must be avoided. Therefore, the stored energy of the Y capacitors CyF+, CyF-, CyL+, CyL- is limited according to the standard to rule out a threat to the vehicle user.

[0044] Therefore, from the perspective of high-voltage safety, a low capacitance value of the Y capacitors CyF+, CyF-, CyL+, CyL- is advantageous. According to the standard, for example, in the specification LV123, there is a requirement that the maximum stored energy in the Y capacitors CyF+, CyF-, CyL+, CyL- should not exceed 0.2 J, in particular, or a so-called alternative countermeasure, i.e., an alternative measure, such as enhanced insulation, is specified. However, this always results in the situation where when two high-voltage systems, such as the vehicle 2 and the DC charging station 5, are connected and enhanced insulation is selected as an alternative countermeasure, both participants should always have enhanced insulation at the same time. However, this cannot be ensured at present.

[0045] According to other standards such as SAE J1772, IEC 60479-1, and IEC 60479-2, the stored energy of the Y capacitors CyF+, CyF-, CyL+, CyL- is not listed as the upper limit level that threatens health, but the electric charge amount that should not exceed the specified value is called the hazard mechanism. For example, the body current IR is given for this purpose. K Duration of the body current IR K Value relationship curve. Here, alternative paths such as enhanced insulation are not accepted.

[0046] Figure 1 The circuit structure of an embodiment of the DC power grid 1 designed as a high-voltage power grid during the DC charging process of the vehicle 2 is shown. The DC power grid 1 thus includes the high-voltage on-board power supply 3 of the vehicle 2 and the DC charging station 5 connected thereto via the charging cable 4. Here, in the example shown, the charging cable 4 has already been connected to the terminal contacts AK+, AK- of the DC charging terminal 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.

[0047] On the left is the DC charging station 5, which has a charging station voltage source 8, an internal resistance R of the charging station LS and the Y capacitors CyL+, CyL-.

[0048] The charging cable 4 is shown beside it on the right.

[0049] On its right side, vehicle 2 together with its high-voltage on-board power supply 3 is shown, which includes charging contactors LS+, LS-, Y capacitors CyF+, CyF- such as an EMC filter, X capacitor Cx such as a DC current intermediate circuit, and a high-voltage battery 6 with main contactors HS+, HS-. The high-voltage battery 6 is shown as a battery power supply 7, which includes, for example, a plurality of single cells connected in electrical series and / or electrical parallel, having an internal battery resistance R Batt .

[0050] In addition, a human body MK is shown in this circuit diagram, which has a human body resistance R K and a switch symbol for an insulation fault IF, for example, in the case of a defective charging cable 4, where, for example, the positive potential HV+ fails. It is also possible for an insulation fault IF to occur at the negative potential HV-. This is not shown here. If an insulation fault IF occurs, the switch symbol is closed. Discharge through the human body MK takes place in the case of such an insulation fault IF and contact of the human body MK with one of the high-voltage potentials HV+, HV- and the reference potential M

[0051] To avoid or at least reduce discharge through the human body MK to an extent that is especially permitted with regard to health threats, a protection device 8 with a protection circuit 9 is provided for reducing the current surges caused by the Y capacitors CyF+, CyF-, CyL+, CyL-. In the example shown, the protection device 8 includes: a first voltage measuring device SV1 between the positive potential line HV+L and the reference potential line ML for measuring the voltage between the positive potential line HV+L and the reference potential line ML, i.e., the voltage between the positive potential HV+ and the reference potential M, especially the ground potential, especially the vehicle body-in-white ground, and a second voltage measuring device SV2 between the negative potential line HV-L and the reference potential line ML for measuring the voltage between the negative potential line HV-L and the reference potential line ML, i.e., the voltage between the negative potential HV- and the reference potential M, especially the ground potential, especially the vehicle body-in-white ground

[0052] Alternatively, in an embodiment not shown, the first voltage measuring device can also be arranged between the HV potential (HV- or HV+) and the reference potential M, and the corresponding second voltage measuring device can be arranged between the two HV potentials (HV- and HV+)

[0053] The voltage measurement and in particular the voltage measurement devices SV1, SV2 control their corresponding protection switches SS1, SS2 when the voltage is below a predetermined voltage value. The protection switches SS1, SS2 are designed, for example, as semiconductor switches such as MOSFETs. Thereby, the discharge network between the positive potential HV+ and the reference potential M, in particular the vehicle body ground, or the discharge network between the negative potential HV- and the reference potential M, in particular the vehicle body ground, is switched on. The discharge network is in the example shown the protection circuit part 9.1, 9.2 of the protection circuit 9.

[0054] The corresponding discharge network, i.e. the corresponding protection circuit parts 9.1, 9.2, preferably consists of an uncharged capacitor hereinafter referred to as protection capacitor Cs, Cs1, Cs2 and a resistor electrically connected in parallel hereinafter also referred to as discharge resistor Re, Re1, Re2. In addition, protection resistors Rs, Rs1, Rs2 are provided, which are electrically connected in series with the protection capacitors Cs, Cs1, Cs2. For example, only the discharge resistors Re, Re1, Re2 can also be provided, but it should have a very low ohmic value in order to quickly reduce the body current IR K . However, the disadvantage is that a low-ohmic insulation defect is thus produced. Therefore, only the combination comprising the protection capacitors Cs, Cs1, Cs2 and the discharge resistors Re, Re1, Re2 will be considered hereinafter.

[0055] The corresponding Re, Re1, Re2 ensure that the protection capacitors Cs, Cs1, Cs2 connected in parallel are voltage-free at the moment of switching on. After switching on, it is used for the rapid discharge of the Y capacitors CyF+, CyF-, CyL+, CyL- of the relevant high-voltage potentials HV+, HV-. In accordance with Figure 1 the example shown in, the protection device 8 with the protection circuit 9 is arranged in the vehicle 2. However, it can also be arranged in the DC charging station 5 in the case of the same function.

[0056] Figure 2 Shows the mode of operation of the protection device 8, in particular the protection circuit 9 and in particular the corresponding protection circuit parts 9.1, 9.2. Fault recognition is carried out by voltage measurement with respect to the reference potential M.

[0057] During the DC current charging process, although the high-voltage potentials HV+, HV- do not necessarily have to be symmetrically distributed with respect to the reference potential M, it should be ensured that the high-voltage potentials HV+, HV- comply with at least the insulation value with respect to the reference potential M, for example greater than 100 ohms / volt. "A person touches the high-voltage potentials HV+, HV-" is manifested in the reduction of the insulation resistance, which is caused by the drift of the high-voltage potentials HV+, HV- with respect to the reference potential M.

[0058] The insulation monitors in the vehicle 2 or the DC charging station 5 regularly check the insulation resistance, but the time period before the identification of an insulation defect IF can be up to a maximum of 30 seconds in the case of the vehicle 2 or up to a maximum of two minutes in the case of the DC charging station 5. Therefore, they cannot prevent the electrocution of a person by the energy stored in the Y capacitors CyF+, CyF-, CyF+, CyF- in the case of an open insulation.

[0059] The protective device 8 with the protection circuit 9 for reducing the Cy impact operates with a view to the limit values for dangerous potentials as described, for example, in the standards SAE J1772, IEC 60479-1 and IEC 60479-2. Here, the electric charge flowing through the human body MK and shown in the graph is referred to as the harmful mechanism. The aim is therefore to identify and reduce the body current IR as quickly as possible. K , in order to minimize the flowing charge. The individual control of the mechanical charging contactors LS+, LS- and / or the main contactors HS+, HS- is too slow for this purpose.

[0060] In the above-mentioned protection circuit 9, the reduction of the insulation value is quickly identified by voltage measurement, and thereupon, for example, the protection capacitors Cs, Cs1, Cs2 for discharging with respect to the relevant high-voltage potentials HV+, HV- are immediately connected in parallel to the human body resistance R by means of a hardware circuit. K or the Y capacitors CyF+, CyF-, CyL+, CyL-. As a result, the voltage between the high-voltage potentials HV+, HV- and the reference potential M suddenly decreases. The current flowing through the human body MK decreases proportionally to the voltage drop.

[0061] The discharge resistors Re, Re1, Re2 have two functions here. Firstly, it is used for their complete discharge before the protection capacitors Cs, Cs1, Cs2 are switched on. Secondly, it accelerates the decrease of the voltage that has dropped between the high-voltage potentials HV+, HV- and the reference potential M after being switched on, and thus the current flowing through the human body MK also decreases with the continuing decrease of the voltage. The corresponding other high-voltage potentials HV-, HV+ increase their voltage with respect to the reference potential M to the same extent, but are not touched by the human body MK and are therefore not dangerous. In a further step, the main contactors HS+, HS- of the high-voltage battery 6 are advantageously opened, the contactors in the DC charging station 5 and / or the charging contactors LS+, LS- are opened, and in a last step, the active discharge of the X capacitor Cx and the Y capacitors CyF+, CyF- of the vehicle 2 is carried out.

[0062] Figure 3Shows alternative fault identification via fault current measurement by means of the fault current measuring device 10. Instead of identifying a fault via the respective voltage measurement of the respective high voltage potentials HV+, HV- with respect to the reference potential M, fault current identification can also be employed. For this purpose, the protection device 8 includes the fault current measuring device 10 within the reference potential line ML. The first protection switch SS1 and / or the second protection switch SS2 can be controlled to close in the case of measuring a fault current by means of the fault current measuring device 10 and are thus correspondingly controlled and closed in this case. Here, advantageously, there is a current evaluation unit 11 connected to the fault current measuring device 10 and the protection switches SS1, SS2 for evaluating the measured fault current and controlling the first protection switch SS1 and / or the second protection switch SS2 based on the measured fault current.

[0063] However, this method is relatively difficult because relatively high charging DC currents must be analyzed for very small fault currents. Additionally, in the presence of a fault current, it is also necessary to distinguish between common-mode interference and differential-mode interference because the output current of the DC charging station 5 also contains a so-called ripple current, i.e., an AC current component.

[0064] Fault identification by means of voltage measurement is thus easy to implement and advantageous. Therefore, fault identification by means of voltage measurement will be further described below.

[0065] By means of the protection device 8 with the protection circuit 9, a predetermined standard such as the standard IEC60479-1 can be complied with. The higher the DC charging voltage, the higher the voltage applied across the Y capacitors CyF+, CyF-, CyL+, CyL-. This thus also causes a current that is proportional to the voltage of the Y capacitors CyF+, CyF-, CyL+, CyL- to increase at the start of the contact process assuming a human body resistance R K The current flowing through the body decreases as the capacitor discharges through the resistor, especially in an exponential function form. The current at the start of the contact is calculated as the quotient of the voltage and the resistance. Assuming a maximum charging voltage of 920V, when it is also assumed that the high voltage potentials are symmetrically distributed with respect to the reference potential M (460V across each Y capacitor), the initial contact current value is 460 volts / 1200 ohms = 383 mA. Starting from this initial current value, the current can be converted into a sinusoidal AC current by dividing by the square root of 6. This corresponds to the value on the X-axis of the so-called C1 characteristic curve within the standard SAE J 1772. The duration of this current can be determined by calculating the time constant t = R × C for the capacitor discharge. The corresponding duration (Y-axis) is then 3 × t at this time. For example, a dwell time of approximately 100 milliseconds in this state is still allowed. As a goal, a residual body current IR K less than 5 mA is selected, i.e., the residual voltage should be less than 6 volts.

[0066] The higher the voltage on a Y capacitor CyF+, CyF-, CyL+, CyL-, for example in the case of an asymmetric high-voltage potential distribution with respect to the reference potential M, the shorter the maximum residence time. A current exceeding 500 mA is not allowed because then the maximum voltage of 600 V will occur on a Y capacitor CyF+, CyF-, CyL+, CyL-. The charging process should also be aborted.

[0067] Therefore, with the aid of the protection device 8 with the protection circuit 9, it can be calculated whether it is still possible to comply with the required maximum current duration. If this condition is not met, the charging process should be aborted immediately because other faults will pose a danger to personnel. The input parameters for this calculation are the voltage measurements on the Y capacitors CyF+, CyF-, CyL+, CyL- at the two high-voltage potentials HV+, HV-, the known self-response speed of the circuit, and a value table of the maximum allowable current residence time.

[0068] Figure 4 Shows the determination of a safe or unsafe operating state. For this purpose, the circuit has been expanded with two additional voltage measuring devices SV3, SV4. Thus, it is possible to determine whether the protection circuit 9 can comply with the legal limit values in the event of, for example, a fault in the insulation within the charging cable 4, before the charging contactors LS+, LS- are closed due to the parallel connection of the DC charging station 5 and the vehicle 2 and the capacitance of the Y capacitors CyF+, CyF-, CyL+, CyL- necessarily increases accordingly. Ideally, for all four voltage measurements, so-called contactor bonding identification of the vehicle 2 is used. The condition is that the maximum delay before the protection capacitors Cs, Cs1, Cs2 are switched on is not exceeded during voltage evaluation. This is advantageously implemented in hardware and without evaluation via a microprocessor.

[0069] Here, there is a voltage evaluation unit 12 in which the voltages measured by the voltage measuring devices SV1 - SV4 are evaluated and the protection switches SS1, SS2 can be controlled accordingly. Additionally, it can be stipulated that the voltage evaluation unit 12 can output other information I, in particular to a slower controller or the DC charging station 5. Exemplary information I is the opening or closing of the charging contactors LS+, LS-, the interruption of the DC charging process, the opening or closing of the main contactors HS+, HS- of the high-voltage battery 6, the initiation of the active discharge of the high-voltage intermediate circuit of the vehicle 2, and / or information I indicating that everything is normal and thus the DC charging process can be started.

[0070] Figure 5A DC grid 1 is shown, which is especially used for the driving operation of a vehicle 2, AC charging operation, and installation and maintenance work, but without a DC charging station 5. The only difference from the state during DC charging is the absence of the DC charging station 5. As a fault mechanism, for example, a defective high-voltage cable or a defective high-voltage electronic device housing caused by an accident is considered. In the case where the high-voltage system is damaged during installation or maintenance, the protection device 8 together with its protection circuit 9 can also reduce the charge quantity.

[0071] The protection circuit 9 for reducing the Y impact caused by an insulation defect IF is as described above. For this purpose, the protection device 8 together with its protection circuit 9 is naturally arranged in the vehicle 2. This function is the same as when an insulation fault occurs during DC charging as described above. With the recognition of the reduction in the voltage between one of the high-voltage potentials HV+, HV- and the reference potential M, the corresponding protection capacitors Cs, Cs1, Cs2 are turned on and the total capacitance of the Y capacitors CyF+, CyF-, CyL+, CyL- of the relevant high-voltage potentials HV+, HV- is discharged. It is also beneficial to command the opening of the main contactors HS+, HS- of the high-voltage battery 6 and start the active discharge of the X capacitor Cx of the vehicle 2 and the two Y capacitors CyF+, CyF-. The charging contactors LS+, LS- have already been opened first and also remain always open.

[0072] The simulation of the discharge of the Y capacitors CyF+, CyF-, CyL+, CyL- due to an insulation defect in the case of a fault at the positive potential HV+ during DC charging at the DC charging station 5 will be described below. The voltage of the DC charging station 5 is 920 volts. The battery voltage of the high-voltage battery 6 is 915 volts. All insulation resistances are 1 megaohm. The capacitances of the Y capacitors CyL+, CyL- of the charging station 5 are 500 nF each. The capacitances of the Y capacitors CyF+, CyF- of the vehicle 2 are 1000 nF each. The human body resistance R K is 1200 ohms. The first discharge resistance Re1 of the first protection circuit part 9.1 is 1200 ohms. The capacitance of the first protection capacitor Cs1 of the first protection circuit part 9.1 is 200 μF. The first protection resistance Rs1 of the first protection circuit part 9.1 is 1 ohm.

[0073] At the moment t = 0.05 seconds, by closing the switch showing the insulation defect IF, the human body resistance R between the positive potential HV+ and the reference potential M K is connected. Once the voltage between the positive potential HV+ and the reference potential M drops below 350 volts, the first protection switch SS1 is closed and the discharge network, that is, the first protection circuit part 9.1, is connected.

[0074] The simulation aims at a target value of less than 5 milliamperes after the first protective capacitor Cs1 is switched on. That is, there is no time limit for this value. However, if a higher body current IR that can be reduced more quickly via the discharge resistors Re, Re1, Re2 is permitted as the target value K , a significant reduction of the corresponding protective capacitors Cs, Cs1, Cs2 can be achieved.

[0075] Figures 6-8 The simulation results are shown. Figure 6 The voltages UCyF+, UCyF-, UCyL+, UCyL- and currents ICyF+, ICyF-, ICyL+, ICyL- of the Y capacitors CyL+, CyL-, CyF+, CyF- of the DC charging station 5 and the vehicle 2 are shown with respect to time t. At time t = 0.05 s, the human body resistance R K is switched on. Capacitor recharge occurs, which is not visible in the above currents on this scale, but is Figure 7 more clearly visible in the curve of the body current IR K . However, recharge can be seen in the voltages UCyF+, UCyF-, UCyL+, UCyL- of the Y capacitors CyL+, CyL-, CyF+, CyF-. From time t = approximately 0.051 s onwards, the first protective capacitor Cs1 is switched on. This causes the Y capacitors CyL+, CyF+ to discharge almost immediately. The remaining voltage at time t = approximately 0.0515 s is 5.2 volts. The recharge current (approx. 60 A - 130 A, depending on the potential) is determined by the first protective resistor Rs1. After the high-voltage potentials HV+, HV- are recharged via the protective capacitor Cs1, i.e., after approximately 0.051 s, the voltage at the negative potential HV- and the reference potential M is 911.4 V.

[0076] Figure 7 Shows the voltage UR K across the human body resistance R K , its current IR K , the current IRe1 of the first discharge resistor Re1 and the current ICs1 and voltage UCs1 of the first protective capacitor Cs1. The body current IR K is 383 milliamperes in case of a fault. It decays to a value of approximately 292 milliamperes in an e-function before the first protective switch SS1 is switched on. After the first protective switch SS1 is switched on, when the voltage between the positive potential HV+ and the reference potential M is below 350 volts, the body current IR KThe current ICS1 in the first protection capacitor Cs1 corresponds to the sum of the currents ICyF+, ICyF-, ICyL+, ICyL- of all capacitors CyL+, CyL-, CyF+, CyF- when the first protection switch SS1 is turned on. It is about 350A.

[0077] Figure 8 Here, the human body resistance R K The current IR K And the resistance R K Charge LR K and through the human body resistance R K Energy transmitted ER K . Charge LR K At time t=approx. 0.051 sec., it is approximately 0.326 C and then increases only slightly. K Energy transmitted ER K It is 0.131 J, which is lower than the maximum value of 0.2 J required in the standard LV123. Although this maximum value originally applies to the energy stored in the Y capacitors CyF+, CyF-, CyL+, and CyL-, it is assumed that the contained energy is discharged in the human body MK and is not limited by the protection circuit 9. Therefore, the protection circuit 9 can also be an alternative measure, that is, an alternative countermeasure.

[0078] Figure 9 The component-optimized protection circuit 9 is shown. In the protection circuit 9 for reducing Cy surges, it is assumed that only one high voltage potential HV+, HV- passes through the human body resistance R K Connected to a reference potential M, for example housing ground. If both high-voltage potentials HV+, HV- are connected to a reference potential M, in particular housing ground, this would be equivalent to a short circuit of the high-voltage battery 6 or the DC charging station 5, which should be disconnected by a fuse or a current sensor together with a disconnection device controlled thereby.

[0079] It is clear from this that the protection circuit 9 is not used to reduce the Cy impact for the positive potential HV+ and the negative potential HV- at the same time. Therefore, a single protection capacitor Cs, a discharge resistor Re and a protection resistor Rs can be used to protect the two high voltage potentials HV+ and HV-, such as Figure 9 As shown. Therefore, the two protective circuit parts 9.1, 9.2 are not required. In addition, the voltage measurement by means of the two voltage measuring devices SV1, SV2 and the two protective switches SS1, SS2 for switching the protective circuit 9 should be retained. Figure 9This shows such component optimization. This is meaningful when the discharge resistance Re necessarily has a higher component value due to, for example, the high operating voltage or high capacitance of the Y capacitors CyF+, CyF-, CyL+, CyL- in the vehicle 2 and the DC charging station 5.

[0080] Figure 10 Shows an embodiment of a protection circuit 9 with particular component optimization, i.e., a protection device 8 without two protection circuit parts 9.1, 9.2. The protection switches SS1, SS2 are designed as MOSFETs here, but other semiconductor switches such as IGBTs or thyristors are also feasible. The protection device 8, especially its protection circuit 9, is reduced here to the additional costs required in the vehicle 2 or on the DC charging station 5. The terminals AHV+, AHV-, AM for the positive potential HV+, negative potential HV-, and reference potential M can remain small because only millisecond-level currents flow in the event of a fault. In other cases, the terminals AHV+, AHV-, AM are currentless and are only used for voltage measurement. As a result, the protection device 8 together with its protection circuit 9 can be integrated into an existing high-voltage system quickly and with few modifications. When there is a longer planning time, this function can obviously also be integrated into existing equipment.

[0081] Figure 11 Shows the mode of operation for voltage reduction by adding a capacitor, here a protection capacitor Cs, to an existing capacitive voltage divider. The capacitive voltage divider corresponds to the Y capacitors CyF+, CyF- in the vehicle 2 and during DC charging. The added discharge capacitor corresponds to the protection capacitor Cs. Before the time t < 0.5 s, there is a voltage division via the series circuit composed of the two Y capacitors CyF+, CyF- between the positive potential HV+ and the negative potential HV-. The two Y capacitors CyF+, CyF- are of the same size as each other, for example 1 μF, whereby the high-voltage potentials HV+, HV- are symmetrically distributed with respect to the reference potential M.

[0082] The target voltage is 400 volts in this example. This voltage is reduced across each Y capacitor CyF+, CyF- because the supply voltage is twice the target voltage, i.e., 800 volts. At the time t = 0.5 s, the first protection switch SS1 is turned on, whereby the protection capacitor Cs with 10 μF is paralleled with the Y capacitor CyF+ with respect to the positive potential HV+, so the sum of the capacitances is increased to 11 μF. Through the capacitive voltage divider together with the Y capacitor CyF- with the negative potential HV-, the voltage between the positive potential HV+ and the reference potential M is thus reduced to approximately 67 volts, while the voltage across the Y capacitor CyF- with the negative potential HV- rises to 733 volts. The voltage across the X capacitor Cx always remains constant at 800 volts.

[0083] The desired voltage after the protective capacitor Cs is turned on can be adjusted by setting the size of the protective capacitor Cs relative to the Y capacitors CyF+ and CyF-. The larger the protective capacitor Cs is compared to the Y capacitors CyF+ and CyF-, the lower the remaining residual voltage.

[0084] Figure 12 The voltages UCyF+, UCyF-, UCs1 of the Y capacitors CyF+ and CyF- and the protective capacitor Cs and the currents ICyF+, ICyF-, ICs1 obtained by the method as Figure 11 shown are plotted in a curve diagram as a function of time.

[0085] Therefore, the protection device 8 includes a first voltage measuring device SV1 for measuring the voltage between the positive potential line HV+L and the reference potential line ML between the positive potential line HV+L and the reference potential line ML, and a second voltage measuring device SV2 for measuring the voltage between the negative potential line HV-L and the reference potential line ML between the negative potential line HV-L and the reference potential line ML.

[0086] In addition, the protection device 8 includes a protection circuit 9. The protection circuit 9 includes a series circuit composed of a discharge resistor Re and a first protection switch SS1 between the positive potential line HV+L and the reference potential line ML, and a series circuit composed of the same discharge resistor Re and a second protection switch SS2 between the negative potential line HV-L and the reference potential line ML, as Figure 9 and 10 shown.

[0087] Alternatively, the protection circuit 9 includes two protection circuit parts 9.1 and 9.2. As Figures 1-5 shown, the first protection circuit part 9.1 includes a series circuit composed of a first discharge resistor Re1 and a first protection switch SS1 between the positive potential line HV+L and the reference potential line ML, and the second protection circuit part 9.2 includes a series circuit composed of a second discharge resistor Re2 and a second protection switch SS2 between the negative potential line HV-L and the reference potential line ML.

[0088] In both variants of the protection circuit 9 of the protection device 8, the first protection switch SS1 can be controlled to turn off when it is determined by the first voltage measuring device SV1 that the voltage is lower than a predetermined voltage value, and the second protection switch SS2 can be controlled to turn off when it is determined by the second voltage measuring device SV2 that the voltage is lower than a predetermined voltage value.

[0089] Instead of the two voltage measuring devices SV1 and SV2, a fault current measuring device 10 can be provided in the reference potential line ML, as Figure 3As shown. Thus, in two variants of the protection circuit 9, the first protection switch SS1 and / or the second protection switch SS2 can be controlled to turn off under a fault current measured by the fault current measuring device 10.

[0090] Advantageously, the protection capacitors Cs, Cs1, Cs2 are electrically connected in parallel with the discharge resistors Re, Re1, Re2 as described above, that is, the sole protection capacitor Cs is electrically connected in parallel with the sole discharge resistor Re, as Figure 9 and 10 shown, or the corresponding protection capacitors Cs1, Cs2 are electrically connected in parallel with the discharge resistors Re1, Re2 of the corresponding protection circuit parts 9.1, 9.2, as Figures 1-5 shown.

[0091] Therefore, the protection circuit 9 includes a series circuit composed of a discharge resistor Re and a first protection switch SS1 between the positive potential line HV+L and the reference potential line ML and a series circuit composed of a discharge resistor Re and a second protection switch SS2 between the negative potential line HV-L and the reference potential line ML, wherein the protection capacitor Cs is electrically connected in parallel with the discharge resistor Re, as Figure 9 and 10 shown. Or, the protection circuit 9 includes two protection circuit parts 9.1, 9.2, wherein the first protection circuit part 9.1 includes a series circuit composed of a first discharge resistor Re1 and a first protection switch SS1 between the positive potential line HV+L and the reference potential line ML, wherein the first protection capacitor Cs1 is electrically connected in parallel with the first discharge resistor Re1, and wherein the second protection circuit part 9.2 includes a series circuit composed of a second discharge resistor Re2 and a second protection switch SS2 between the negative potential line HV-L and the reference potential line ML, wherein the second protection capacitor Cs2 is electrically connected in parallel with the second discharge resistor Re2, as Figures 1-5 shown.

[0092] In the example shown herein, not only the protection capacitors Cs, Cs1, Cs2 are electrically connected in parallel with the discharge resistors Re, Re1, Re2, but also a series circuit composed of the protection capacitors Cs, Cs1, Cs2 and the protection resistors Rs, Rs1, Rs2 is electrically connected in parallel therewith.

[0093] Therefore, the protection circuit 9 includes a series circuit composed of a discharge resistor Re and a first protection switch SS1 between the positive potential line HV+L and the reference potential line ML and a series circuit composed of a discharge resistor Re and a second protection switch SS2 between the negative potential line HV-L and the reference potential line ML, wherein the series circuit composed of the protection capacitor Cs and the protection resistor Rs is electrically connected in parallel with the discharge resistor Re, as Figure 9 and Figure 10As shown. Alternatively, the protection circuit 9 includes two protection circuit sections 9.1 and 9.2. Among them, the first protection circuit section 9.1 includes a series circuit composed of a first discharge resistor Re1 and a first protection switch SS1 between the positive potential line HV+L and the reference potential line ML. Among them, a series circuit composed of a first protection capacitor Cs1 and a first protection resistor Rs1 is electrically connected in parallel with the first discharge resistor Re1. And among them, the second protection circuit section 9.2 includes a series circuit composed of a second discharge resistor Re2 and a second protection switch SS2 between the negative potential line HV-L and the reference potential line ML. Among them, a series circuit composed of a second protection capacitor Cs2 and a second protection resistor Rs2 is electrically connected in parallel with the second discharge resistor Re2, as Figures 1-5 shown.

[0094] For example, a first voltage evaluation unit connected to the first voltage measurement device SV1 and the first protection switch SS1 is provided, which is used to evaluate the voltage determined by the first voltage measurement device SV1 and control the first protection switch SS1 when the voltage is lower than a predetermined voltage limit value. And a second voltage evaluation unit connected to the second voltage measurement device SV2 and the second protection switch SS2 is provided, which is used to evaluate the voltage determined by the second voltage measurement device SV2 and control the second protection switch SS2 when the voltage is lower than a predetermined voltage limit value.

[0095] Alternatively, for example, as Figure 4 shown, a common voltage evaluation unit 12 connected to the voltage measurement devices SV1 and SV2 and the protection switches SS1 and SS2 is provided, which is used to evaluate the voltage determined by the first voltage measurement device SV1 and the voltage determined by the second voltage measurement device SV2, and is used to control the first protection switch SS1 when the voltage determined by the first voltage measurement device SV1 is lower than a predetermined voltage limit value and control the second protection switch SS2 when the voltage determined by the second voltage measurement device SV2 is lower than a predetermined voltage limit value.

[0096] When using the fault current measurement device 10, correspondingly, for example, a current evaluation unit 11 connected to the fault current measurement device 10 and the protection switches SS1 and SS2 is provided, which is used to evaluate the measured fault current and control the first protection switch SS1 and / or the second protection switch SS2 according to the measured fault current.

[0097] In a possible implementation manner, it can be as Figure 4As stipulated, the shared voltage evaluation unit 12 is connected to the third voltage measuring device SV3 and the fourth voltage measuring device SV4. Among them, the third voltage measuring device SV3 is arranged between the positive potential line HV+L and the reference potential line ML to measure the voltage between the positive potential line HV+L and the reference potential line ML, and the fourth voltage measuring device SV4 is arranged between the negative potential line HV-L and the reference potential line ML to measure the voltage between the negative potential line HV-L and the reference potential line ML. And among them, a first switch unit (in the form of a charging contactor LS+ within the positive potential line HV+L here) is provided between the connection part for the first voltage measuring device SV1 and the connection part for the third voltage measuring device SV3 in the positive potential line HV+L, and a second switch unit (in the form of a charging contactor LS- within the negative potential line HV-L here) is provided between the connection part for the second voltage measuring device SV2 and the connection part for the fourth voltage measuring device SV4 in the negative potential line HV-L.

[0098] The following will describe the advantageous application possibilities of the protection device 8. In a vehicle 2 with a high-voltage system at the 800-volt level, it is difficult to comply with the discharge limit values required by the standards for the Y capacitors CyF+, CyF-, CyL+, CyL-. This especially applies to existing vehicles 2, which do not allow adjustments to be made in the high-voltage system for large additional components due to the occupied structural space within the vehicle 2. Here, the described solution is proposed because it can be installed in the vehicle 2 in a simple and inexpensive manner and with a low structural space requirement.

[0099] In addition, the regulations especially from the standards are met through the described solution, thereby simplifying or enabling the vehicle 2 to obtain access permission. With the protection device 8 and its protection circuit 9, the limit values are achieved by adding small electronic devices without having to make changes, for example, to the high-voltage system and its components.

[0100] The maximum internal energy of 0.2 J required by LV123 has already been exceeded at 632 volts due to the DC charging station 5. Therefore, "alternative measures", that is, alternative countermeasures, are necessarily required. As the only solution, double insulation is currently being discussed. Then, all connected systems, that is, the vehicle 2 and the DC charging station 5, should simultaneously have enhanced isolation, which is actually impossible to ensure. However, with the protection device 8 and its protection circuit 9, the energy flowing through the human body MK can also be kept below the value of 0.2 J. It is therefore another solution for the "alternative measures".

[0101] The protection device 8 and its protection circuit 9 allow for reducing the dangerous discharge current of the Y capacitors CyF+, CyF-, CyL+, CyL- during human contact when insulation is damaged during DC current charging, for example when the charging plug or charging cable 4 is damaged. In all other vehicle states, it also reduces the dangerous charging during human contact when insulation is damaged.

[0102] Improved EMC immunity is achieved through a larger design of the Y capacitors CyF+, CyF-, CyL+, CyL-. This will allow for dispensing with the required double insulation of the entire high-voltage system. This applies to the vehicle 2 and the DC charging station 5.

[0103] The protection device 8 and its protection circuit 9 can be arranged in the vehicle 2 and / or in the DC charging station 5.

[0104] List of reference numerals:

[0105] 1 DC grid

[0106] 2 Vehicle

[0107] 3 High-voltage on-board power supply

[0108] 4 Charging cable

[0109] 5 DC charging station

[0110] 6 High-voltage battery

[0111] 7 Battery power supply

[0112] 8 Protection device

[0113] 9 Protection circuit

[0114] 9.1, 9.2 Protection circuit parts

[0115] 10 Fault current measurement device

[0116] 11 Current evaluation unit

[0117] 12 Voltage evaluation unit

[0118] AHV+, AHV-, AM Terminals

[0119] AK+, AK- Terminal contacts

[0120] Cs, Cs1, Cs2 Protection capacitors

[0121] Cx X capacitor

[0122] CyF+, CyF- Vehicle-side Y capacitors

[0123] CyL+, CyL- DC charging station-side Y capacitors

[0124] ER K Energy

[0125] HS+ and HS- main contactors

[0126] HV+ and HV- high voltage potentials

[0127] HV+L and HV-L high voltage potential lines

[0128] I Information

[0129] ICs1 Current of the first protection capacitor

[0130] ICyF+ and ICyF- Currents of the vehicle-side Y capacitors

[0131] ICyL+ and ICyL- Currents of the DC charging station-side Y capacitors

[0132] IF Insulation defect

[0133] IRe1 Current of the first discharge resistor

[0134] IR K Current of the human body resistance

[0135] LR K Charge

[0136] LS+ and LS- Charging contactors

[0137] M Reference potential

[0138] ML Reference potential line

[0139] MK Human body

[0140] R Batt Internal resistance of the battery

[0141] Re, Re1, Re2 Discharge resistors

[0142] R K Human body resistance

[0143] R LS Internal resistance of the charging station

[0144] Rs, Rs1, Rs2 Protection resistors

[0145] SS1 and SS2 Protection switches

[0146] SV1, SV2, SV3, SV4 Voltage measuring devices

[0147] t Time

[0148] Voltage of the first protection capacitor of UCs1

[0149] Voltage of the vehicle-side Y capacitors UCyF+ and UCyF-

[0150] Voltage of the DC charging station-side Y capacitors UCyL+ and UCyL-

[0151] UR K Voltage of the human body resistance

Claims

1. A protection device (8) for a DC power grid (1), in particular a high-voltage power grid, characterized in that - a first voltage measuring device (SV1) is provided between the positive potential line (HV+L) and the reference potential line (ML) for measuring the voltage between the positive potential line (HV+L) and the reference potential line (ML), and a second voltage measuring device (SV2) is provided between the negative potential line (HV-L) and the reference potential line (ML) for measuring the voltage between the negative potential line (HV-L) and the reference potential line (ML), or - a fault current measuring device (10) is provided in the reference potential line (ML), and - a protection circuit (9) is provided, which protection circuit has: - a series circuit composed of a discharge resistor (Re) and a first protection switch (SS1) between the positive potential line (HV+L) and the reference potential line (ML), and a series circuit composed of a discharge resistor (Re) and a second protection switch (SS2) between the negative potential line (HV-L) and the reference potential line (ML), or - two protection circuit parts (9.1, 9.2), wherein the first protection circuit part (9.1) includes a series circuit composed of a first discharge resistor (Re1) and a first protection switch (SS1) between the positive potential line (HV+L) and the reference potential line (ML), and the second protection circuit part (9.2) includes a series circuit composed of a second protection switch (SS2) and a second discharge resistor (Re2) between the negative potential line (HV-L) and the reference potential line (ML), wherein - the first protection switch (SS1) can be driven to close when it is determined by means of the first voltage measuring device (SV1) that the voltage is lower than a specified voltage value and / or can be driven to close when it is determined by means of the second voltage measuring device (SV2) that the voltage is higher than a specified voltage value, and - the second protection switch (SS2) can be driven to close when it is determined by means of the second voltage measuring device (SV2) that the voltage is lower than a specified voltage value and / or can be driven to close when it is determined by means of the first voltage measuring device (SV1) that the voltage is higher than a specified voltage value, or - the first protection switch (SS1) and / or the second protection switch (SS2) can be driven to close when a fault current is measured by means of the fault current measuring device (10).

2. The protection device (8) according to claim 1, characterized in that, Protection capacitors (Cs, Cs1, Cs2) are electrically connected in parallel with the discharge resistors (Re, Re1, Re2).

3. The protection device (8) according to claim 2, characterized in that, A series circuit composed of protection capacitors (Cs, Cs1, Cs2) and protection resistors (Rs, Rs1, Rs2) is electrically connected in parallel with the discharge resistors (Re, Re1, Re2).

4. The protection device (8) according to any one of the preceding claims, characterized in that There is a first voltage evaluation unit connected to a first voltage measuring device (SV1) and a first protection switch (SS1) for evaluating the voltage determined by the first voltage measuring device (SV1) and controlling the first protection switch (SS1) when the voltage is below a specified voltage limit value, and there is a second voltage evaluation unit connected to a second voltage measuring device (SV2) and a second protection switch (SS2) for evaluating the voltage determined by the second voltage measuring device (SV2) and controlling the second protection switch (SS2) when the voltage is below a specified voltage limit value, or There is a first voltage evaluation unit connected to a first voltage measuring device (SV1) and a second protection switch (SS2) for evaluating the voltage determined by the first voltage measuring device (SV1) and controlling the second protection switch (SS2) when the voltage is above a specified voltage limit value, and there is a second voltage evaluation unit connected to a second voltage measuring device (SV2) and a first protection switch (SS1) for evaluating the voltage determined by the second voltage measuring device (SV2) and controlling the first protection switch (SS1) when the voltage is above a specified voltage limit value, or There is a current evaluation unit (11) connected to a fault current measuring device (10) and protection switches (SS1, SS2) for evaluating the measured fault current and controlling the first protection switch (SS1) and / or the second protection switch (SS2) based on the measured fault current, or There is a common voltage evaluation unit (12) connected to voltage measuring devices (SV1, SV2) and protection switches (SS1, SS2) for evaluating the voltage determined by the first voltage measuring device (SV1) and the voltage determined by the second voltage measuring device (SV2), and for controlling the first protection switch (SS1) when the voltage determined by the first voltage measuring device (SV1) or the second voltage measuring device (SV2) is below a specified voltage limit value, and for controlling the second protection switch (SS2) when the voltage determined by the second voltage measuring device (SV2) or the first voltage measuring device (SV1) is below a specified voltage limit value.

5. The protection device (8) according to claim 4, characterized in that, The common voltage evaluation unit (12) is connected to a third voltage measuring device (SV3) and a fourth voltage measuring device (SV4), wherein the third voltage measuring device (SV3) is arranged between the positive potential line (HV+L) and the reference potential line (ML) to measure the voltage between the positive potential line (HV+L) and the reference potential line (ML), and the fourth voltage measuring device (SV4) is arranged between the negative potential line (HV-L) and the reference potential line (ML) to measure the voltage between the negative potential line (HV-L) and the reference potential line (ML), wherein a first switching unit is provided in the positive potential line (HV+L) between the connection point for the first voltage measuring device (SV1) and the connection point for the third voltage measuring device (SV3), and a second switching unit is provided in the negative potential line (HV-L) between the connection point for the second voltage measuring device (SV2) and the connection point for the fourth voltage measuring device (SV4).

6. The protection device (8) according to any one of the preceding claims, characterized in that, The protection switches (SS1, SS2) are each designed as semiconductor switches.

7. An on-vehicle power supply (3) for a vehicle (2), in particular a high-voltage on-vehicle power supply (3), said on-vehicle power supply comprising a protection device (8) according to any one of the preceding claims.

8. A vehicle (2), in particular an electric vehicle or a hybrid vehicle, said vehicle comprising an on-vehicle power supply (3) according to claim 7.

9. A DC charging station (5), in particular a high-voltage DC charging station, said DC charging station comprising a protection device (8) according to any one of claims 1 to 6.

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