Protection device for an electric DC network, in-vehicle electrical system for a vehicle, vehicle, and DC charging station

Abstract

The present invention relates to a protection device (8) for a direct current network (1), comprising a voltage measuring device (SV1) between each potential line (HV+L, HV-L) and a reference potential line (ML) and a protection circuit (9) for reducing electric shocks due to Y capacitors (CyF+, CyF-, CyL+, CyL-) of the electrical direct current network (1), the protection circuit (9) comprising protection switches (SS1, SS2) between each potential line (HV+L, HV-L) and the reference potential line (ML), wherein a number of trigger criteria are set, the first protection switch (SS1) and / or the second protection switch (SS2) being operable to close only when all the set trigger criteria are fulfilled, as determined by the first voltage measuring device (SV1) and / or the second voltage measuring device (SV2).

Description

Technical Field

[0001] The present invention relates to a protection device for an electrical DC network, an in-vehicle electrical system for a vehicle, a vehicle, and a DC charging station based on the constituent elements of the superordinate concept of claim 1.

[0002] From the prior art, Patent Document 1 belonging to this field describes an in-vehicle electrical system structure for an automobile, and this in-vehicle electrical system structure has a high-voltage energy accumulator for providing a first high-voltage potential and a second high-voltage potential. The overall voltage can be picked up between the first and second high-voltage potentials, there is a first insulation resistance between the first high-voltage potential and a predetermined electrical ground, and there is a second insulation resistance between the second high-voltage potential and the predetermined electrical ground. An insulation monitoring device monitors the first and second insulation resistances and has a balancing circuit designed to perform an active symmetrization process, whereby the difference between the first insulation resistance and the second insulation resistance is at least reduced by the active symmetrization process.

[0003] Patent Document 2 also discloses an in-vehicle electrical system structure for providing first and second high-voltage potentials, and the overall voltage can be picked up between these high-voltage potentials. This in-vehicle electrical system structure is symmetrically configured such that the first insulation resistance between the first high-voltage potential and the ground and the second insulation resistance between the second high-voltage potential and the ground differ by at most a predetermined extent. For this purpose, this in-vehicle electrical system structure has a symmetry monitoring device, which is designed to monitor the in-vehicle electrical system symmetry and trigger a predetermined measure when the first insulation resistance differs from the second insulation resistance by more than a predetermined range.

[0004] From the prior art, as described in Patent Document 3, a method for operating an electric vehicle electrical system is also known. In this method of operating a first vehicle electrical system loaded with a first DC voltage and a second vehicle electrical system loaded with a second DC voltage, the first and second vehicle electrical systems are electrically coupled by an energy coupler having a first clock-type energy converter. The first and second DC voltages are electrically insulated from the electrical reference potential by an electrical insulation device. The electrical insulation device is monitored. The first and second vehicle electrical systems are conductively coupled by an energy coupler. When an interference occurs in the insulation device in one of the regions of both vehicle electrical systems, the energy coupler controls the respective electrical potential of the other of both vehicle electrical systems so that the respective potential difference of these electrical potentials with respect to the reference potential becomes smaller than a set reference value. Patent Document 4 describes a protection device for an electric DC network, particularly for a high-voltage network, an in-vehicle electrical system for a vehicle, a vehicle, and a DC charging station. This protection device includes a first voltage measuring device between a positive potential line and a reference potential line for measuring the voltage therebetween, and a second voltage measuring device between a negative potential line and the reference potential line for measuring the voltage therebetween, or includes a fault current measuring device in the reference potential line. Further, this protection device includes a protection circuit and has an electrical series circuit of a discharge resistor and a first protection switch between the positive potential line and the reference potential line, and an electrical series circuit of a discharge resistor and a second protection switch between the negative potential line and the reference potential line, or has two protection circuit portions. The first protection circuit portion includes an electrical 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 an electrical series circuit of a second discharge resistor and a second protection switch between the negative potential line and the reference potential line. The first protection switch is operable to close when it is determined by the first and / or second voltage measuring devices that a predetermined voltage value is being undershot, and the second protection switch is operable to close when it is determined by the second and / or first voltage measuring devices that a predetermined voltage value is being undershot. As an alternative, the first protection switch and / or the second protection switch are operable to close when a fault current is measured by a fault current device.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] The object of the present invention is to provide a protection device for an electric DC network improved compared to the prior art, an in-vehicle electrical system for a vehicle improved compared to the prior art, a vehicle having such an in-vehicle electrical system improved compared to the prior art, and a DC charging station improved compared to the prior art.

Means for Solving the Problem

[0007] According to the present invention, this problem is solved by a protection device for an electric DC network having the features described in claim 1, an in-vehicle electrical system for a vehicle having the features of claim 5, a vehicle having the features of claim 6, and a DC charging station having the features of claim 7.

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

[0009] A protection device for an electric DC network, particularly for a high-voltage network, for example for an in-vehicle electrical system of a vehicle, includes a first voltage measuring device between a positive potential line and a reference potential line for measuring the voltage between the positive potential line and the reference potential line, and a second voltage measuring device between a negative potential line and the reference potential line for measuring the voltage between the negative potential line and the reference potential line. The reference potential line is particularly an electrical ground potential, particularly a vehicle ground potential when the protection device is used in a vehicle, and for example a ground potential when the protection device is used in a DC charging station.

[0010] Furthermore, the protection device includes a protection circuit for reducing an electric shock caused by a Y capacitor of the electric DC network, particularly to a person, i.e., to a human body.

[0011] The protection circuit includes a first protection switch between the positive potential line and the reference potential line, and a second protection switch between the negative potential line and the reference potential line. A plurality of trigger criteria are set, and the first protection switch and / or the second protection switch are operable to close only when all of the set trigger criteria determined by the first voltage measuring device and / or the second voltage measuring device are met. The trigger criteria relate in particular to fault causes / interferences that may occur and that, if they occur, should prevent the closing of the protection switch. Preferably, at least one trigger criterion is set for each of these fault causes / interferences, which is met when there is physical contact with one of the high voltage potentials, i.e. when there is contact with a person, i.e. with the human body, and is not met when each of the respective fault causes occurs. The triggering, i.e. the closing, of each protection switch takes place only when all of the predetermined trigger criteria are met, i.e. satisfied. Thereby, it is ensured that each protection switch is closed only when there is physical contact with one of the high voltage potentials, i.e. when there is contact with a person, i.e. with the human body, and false closing based on the occurrence of one or more of the fault causes / interferences is avoided.

[0012] The in-vehicle electrical system according to the invention for a vehicle, in particular for an electric vehicle or a hybrid vehicle, in particular for a high-voltage in-vehicle electrical system, in particular a high-voltage in-vehicle electrical system, comprises 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 comprises such an in-vehicle electrical system, in particular a high-voltage in-vehicle electrical system, comprising such a protection device.

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

[0015] The concept of "high voltage" means, in particular, an electrical DC voltage greater than about 60 V. In particular, the concept of "high voltage" is designed to be compatible with the standard ECE R 100.

[0016] According to the solution of the present invention, not only is the protection circuit triggered very quickly to keep the charging and energy embodied by the body resistance low, but false triggering is carried out as little as possible, or preferably avoided. False triggering will lead to insulation failure in a very short time span. Furthermore, this protection circuit acts such that a large shift in the high voltage potential occurs, which is the largest difference with respect to the minimum energy value of the energy stored in the Y capacitor. Furthermore, if the false triggering of the protection circuit is repeated, the function of the insulation monitor may be impaired. For example, interference sources in vehicles and / or DC charging stations may trigger false triggering of the protection circuit. This is avoided or at least significantly reduced by the solution of the present invention.

[0017] According to the solution of the present invention, the evaluation of the protection circuit becomes more stable against false triggering because a plurality of trigger criteria must be satisfied simultaneously. The individual trigger criteria are evaluated, in particular, by an AND operation. The individual trigger criteria are determined depending on the type of interference. The characteristics of the discharge of the Y capacitor due to body contact are compared with the interference pattern. In order to distinguish each interference from such a CY body resistance discharge, it is preferable to find at least one indicator that can be detected by measurement or evaluation. Such at least one indicator must be distinguished for each interference with respect to the characteristics of the CY body current discharge. For example, this is the distinction between common mode and differential mode events, the minimum recharge voltage, the time constant of capacitor recharge (the time constant of the e-function), the frequency / frequency spectrum or repetition rate of clock interference, etc. Voltage measurement by a voltage measuring device is used as the measured input quantity, i.e., voltage measurement between the positive potential line and the reference potential line and between the negative potential line and the reference potential line is used.

[0018] By associating the trigger of the protection circuit with various characteristic indicators of CY body discharge, it is possible to minimize or completely avoid the number of false triggers. At the same time, a very fast trigger time is achieved, along with which the energy / discharge embodied in the human body is minimized.

[0019] The voltage measured by the voltage measuring device is evaluated in particular as follows: - The difference of the currently occurring voltage dU from the positive potential line to the reference potential line and from the negative potential line to the reference potential line with respect to the previously determined voltage value is determined, and / or, - The voltage change dU / dt of the voltage from the positive potential line to the reference potential line and from the negative potential line to the reference potential line, i.e., the voltage change over time, is determined, and / or, - Regarding the evaluation of the voltage from the positive potential line to the reference potential line and from the negative potential line to the reference potential line, especially in both of the above determinations, the opposite sign is considered, and / or, - The periodic repetition of the occurring interference is considered.

[0020] Therefore, the trigger criteria include the following: - The voltage difference of the currently occurring voltage between the positive potential line and the reference potential line and between the negative potential line and the reference potential line with respect to the previously determined voltage value, and / or, - The voltage change over time of the voltage between the positive potential line and the reference potential line and between the negative potential line and the reference potential line, and / or, - The opposite sign of the voltage between the positive potential line and the reference potential line and between the negative potential line and the reference potential line, and / or, - The non-existence of the periodic repetition of other trigger criteria.

[0021] The first protection switch and / or the second protection switch is operable only in the following cases. - The voltage difference over time between the voltage currently present between the positive potential line and the reference potential line and the previously determined voltage value, and between the voltage present between the negative potential line and the reference potential line, exceeds a set limit value, which is, in one possible embodiment, a limit value of 30 V, and - The voltage change over time between the voltage present between the positive potential line and the reference potential line and the voltage present between the negative potential line and the reference potential line exceeds a set limit value, and - When there is an opposite sign between the voltage present between the positive potential line and the reference potential line and the voltage present between the negative potential line and the reference potential line.

[0022] The limit value depends in particular on the time constant t = R*C to be considered. Here, R is the human body resistance, assumed to be the lowest value according to a specification set with a maximum of 500 ohms. For example, the body resistance is considered within the range of 300 ohms to 30 k ohms. C depends on the total capacitance of the Y capacitors present in the high-voltage system, i.e., the high-voltage DC network. This is vehicle situation-dependent, for example, depending on whether only the vehicle is considered during driving operations, or the vehicle is considered in relation to a DC charging station. For example, for C, it ranges from 200 nF (especially optimized for the vehicle only, especially for the low capacitance of the Y capacitors) to about 8 μF (for the DC charging station and the vehicle) during megawatt charging, i.e., during high-power DC charging. All capacitance values are for each high-voltage potential, i.e., a value twice as large is assumed as the total capacitance. The protection circuit is required in particular to become active under a voltage exceeding 60 V. For example, for low frequencies, an insulation monitor is considered as the discrimination target (test resistance of about 800 k ohms, clock time of about 10 s), and for frequencies exceeding the trigger time constant, an inverter with a clock frequency of at least 2 kHz is considered as the discrimination target.

[0023] According to the present invention, the first protection circuit and / or the second protection circuit are operable only when the non-existence of the periodic repetition of other trigger criteria is also determined.

[0024] For example, an analog and / or digital evaluation of the voltage determined by the first voltage measuring device and / or by the second voltage measuring device is provided.

[0025] For example, in the analog evaluation by the output of a voltage measurement (for example, a high-resistance voltage divider), for each high-voltage potential, two evaluations are combined via an operational amplifier circuit. These operational amplifier circuits have two different time constants. The operational amplifier circuit with the first time constant (low frequency, below the time constant of discharge through the human body resistance) determines the voltage difference with respect to the previously determined voltage value. The operational amplifier circuit with the second time constant (high frequency, above the time constant of discharge through the human body resistance) determines the voltage change over time. Both of these trigger criteria are combined via a logical AND operation, and at the same time, a logical AND operation is performed with the negative result of the evaluation of the other high-voltage potential respectively, thereby determining whether both voltages have opposite signs. If the combined result is "true", the protection circuit is activated.

[0026] In the digital evaluation, the measured voltage is detected, for example, by a microcontroller, an Asic (application-specific integrated circuit), or an FPGA (field-programmable gate array, i.e., a digital engineering integrated circuit capable of loading a logic circuit). Filtering and determination of the voltage difference with respect to the previously determined voltage value and the voltage change over time are performed for each high-voltage potential based on software, and then the AND operation already described for the analog evaluation is performed. If the combined result is "true", the protection circuit is activated.

[0027] For example, the analog and digital evaluations are embodied simultaneously, especially as redundancy.

[0028] By the above-described solution, it is realized that contact with a high potential by a human body is recognized as quickly as possible, and the start of operation of the protection circuit is executed. The quick start of operation is based on the discharge process / recharge process of the Y capacitor that proceeds relatively quickly during contact with the high potential by the human body (on the order of about 10 ms). At this time, most of the energy embodied in the body or most of the charge flowing through the body is generated at the start of the discharge process / recharge process. This decays according to the e function. Furthermore, this requires triggering the protection circuit as quickly as possible.

[0029] However, it is also necessary that false triggering based on other influencing factors is excluded or occurs at least rarely. A falsely triggered protection circuit leads to a very disadvantageous potential distribution in terms of energy from each high potential to the reference potential. Therefore, the energy value stored in the Y capacitor reaches near its maximum value. For example, the positive potential with respect to the reference potential becomes almost 0 V, and the negative potential with respect to the reference potential becomes almost close to the system voltage of the high-voltage system, for example, 800 V. Furthermore, under a falsely triggered protection circuit, insulation failure occurs at the moment the protection circuit is activated. Furthermore, under the connection due to the capacitance of the protection circuit, an additional capacitance is connected in parallel with the Y capacitor, which basically provides the possibility of storing even more energy in the thus increased overall Y capacitance.

[0030] Since the protection circuit must recognize as quickly as possible the discharge due to the human body resistance, it is necessary to be configured quickly with respect to the reaction behavior. Therefore, the protection circuit is highly sensitive to the influence of other interferences. By the solution described above, false triggers that may result from such increased sensitivity are avoided or at least significantly reduced. Providing means for distinguishing between interference and contact with the human body resistance is, as already explained above, for example, the comparison of the signs of both measured voltages, which enables the distinction between common-mode disturbances and differential-mode disturbances, a filter for distinguishing interference frequencies, in particular the formation of an average value for distinguishing small energy effects, or the voltage change in the comparison with the average value over a defined time period, the maximum voltage amplitude of the recharge process, and / or, for example, a scanning process based on a set repetition rate for recognizing a regularly pulsating interference source, such as an inverter.

[0031] Focusing on the recharge process of the Y capacitor when contacted by the human body, this corresponds to common-mode interference or, respectively, to the triggering of a common-mode current. This is preferably distinguished from the following effects: The common-mode interference, also called common-mode noise, of clocked high-voltage components results in a common current contribution through the reference potential, similar to the case of body discharge. Due to the large number of clocked high-voltage components in a vehicle, their various different clock frequencies, and the possible variability of clock frequencies, for example, in an on-board charger with an insulating LLC-DC / DC converter, the frequency range can be widely dispersed.

[0032] In addition to the common-mode interference described above, the clock-type high-voltage power consumption unit acts to cause differential-mode interference. Such a high-voltage power consumption unit may also affect the evaluation circuit with its interference level. The insulation monitor also induces the recharging behavior of the same Y capacitor as the body discharge. At this time, under the principles of both well-known insulation monitors, in particular, the insulation monitor by the recharging resistor is critical. The following table compares the CY body discharge with the interference effects described above in terms of frequency spectrum, voltage amplitude, type of interference (CM or DM), and repetition rate.

[0033]

Table 1

[0034] The efforts to avoid false triggering of the protection circuit lie particularly in combining a plurality of indicators with each other.

[0035] For example, for voltage measurement, a band-pass filter that can be implemented by, for example, hardware or software may be provided. This makes it possible to discriminate particularly downward the common-mode interference of the human body resistance against the interference of the insulation monitor, and makes it possible to discriminate particularly upward the common-mode interference against the clock-type components. Thereby, the interaction between the insulation monitor, the high-voltage power consumption unit, and the charging station (EVSE) and the protection circuit is reduced.

[0036] For example, for the positive potential and the negative potential, a logical operation of the voltage trigger is provided. This makes it possible to reliably distinguish between common-mode interference and differential-mode interference, and thereby it is only necessary to consider the common-mode interference hereafter. Thereby, the interaction between the clock-type power consumption unit and the protection circuit is reduced.

[0037] For example, a minimum recharge amplitude of, for example, 50 V is considered, i.e., the protection circuit is triggered only then. That is, small interferences are ignored. Thereby, the interaction between the clocked power consumption unit and the protection circuit is reduced.

[0038] For example, a moving average, i.e., the average value of the voltage over a set time period, is considered, and the protection circuit is triggered only when this is reached. Very low-resistance and regular interferences are thereby evaluated even more weakly. Thereby, the interaction between the clocked power consumption unit and the protection circuit is reduced.

[0039] In one possible embodiment, in order to evaluate the voltage determined by the first voltage measuring device and the voltage determined by the second voltage measuring device, and in order to activate the first protection switch and / or the second protection switch only when all set trigger criteria determined by the first voltage measuring device and / or the second voltage measuring device are met, a common voltage evaluation unit connected to the voltage measuring device and the protection circuit is provided.

[0040] Each protection switch is configured, for example, as a semiconductor switch, for example as a MOSFET, IGBT, or thyristor.

[0041] In one possible embodiment, the protection circuit includes, for example, an electrical series circuit of a discharge resistor and the first protection switch between the positive potential line and the reference potential line, and an electrical series circuit of a discharge resistor and the second protection switch between the negative potential line and the reference potential line. As an alternative, the protection circuit includes, for example, two protection circuit parts, the first protection circuit part including an electrical series circuit of a first discharge resistor and the first protection switch between the positive potential line and the reference potential line, and the second protection circuit part including an electrical series circuit of a second discharge resistor and the second protection switch between the negative potential line and the reference potential line.

[0042] The above-described solution solves the problems associated with Y capacitors in vehicles, particularly electric and hybrid vehicles, and DC charging stations, as will be explained later. Such Y capacitors are used as a measure to reduce the emission of EMC interference (EMC = electromagnetic compatibility). However, due to the Y capacitor, the potential risk increases for reasons of high-voltage safety. For example, in standards SAE J1772, IEC60479-1 and -2, the charge contained in the Y capacitor is listed as an indicator threatening health (C1 characteristic curve). The higher the operating voltage of the vehicle, the more difficult it becomes to comply with the limit values required by these standards. In part, alternative measures for complying with safety settings, such as enhanced, particularly doubled, electrical insulation, and so-called alternative measured values, are not allowed. Another standard, LV123 and related standards, define, for example, a maximum energy content of 0.2 J for the charge of all Y capacitors. If avoidance through alternative measures is allowed, for example, the enhanced, particularly doubled, electrical insulation already mentioned can be applied. However, this is only possible if all high-voltage systems connected to each other are correspondingly enhanced and insulated. That is, in the case of DC charging, for example, not only the vehicle but also the DC charging station, particularly the charging column, must be correspondingly enhanced and insulated. However, since there is no mandatory standard for this, it is also conceivable that systems with different insulation designs are connected, and for this reason, safety requirements are not complied with.

[0043] These problems are solved by the circuit described above. Voltage measurements for each high-voltage potential with respect to a reference potential, particularly with respect to ground potential, enable the recognition of a shift in the high-voltage potential with respect to the reference potential that may result from a body current, i.e., in particular, a body contact between one of the high-voltage potentials and the reference potential and a human. At the corresponding high-voltage potential where the voltage with respect to the reference potential has decreased, a discharge resistor and preferably an uncharged protection capacitor electrically connected in parallel thereto are added to reduce the voltage as quickly as possible. Thereby, the voltage between the corresponding high-voltage potential and the reference potential jumps sharply to a very low level, whereby the body current is reduced in proportion to the voltage. The solution described above in this way enables the reduction of electric shock, particularly to the human body, caused by the Y capacitor. Compliance with the requirements described above becomes possible in this way. Despite the fact that the energy stored in the Y capacitor can become significantly high, it is likewise possible to limit the electrical energy of the Y capacitor embodied by the body resistance to a level below 0.2 J.

[0044] As already mentioned above, it is preferable for the protection capacitor to be electrically connected in parallel to the discharge resistor. In order to quickly reduce the body current, the discharge resistor alone should be very low resistance. However, there is the disadvantage that this is accompanied by low-resistance insulation failure. Therefore, a combination of a discharge resistor and a protection capacitor electrically connected in parallel is much more preferable. The discharge resistor ensures that the protection capacitor electrically connected in parallel is at zero voltage at the moment of connection. The protection capacitor acts after connection for the rapid discharge of the Y capacitor of the corresponding high-voltage potential.

[0045] Thus, the protection circuit includes, for example, an electrical series circuit of a discharge resistor and a first protection switch between the positive potential line and the reference potential line, and an electrical series circuit of a discharge resistor and a second protection switch between the negative potential line and the reference potential line, and the protection capacitor is electrically connected in parallel to the discharge resistor. As an alternative, the protection circuit includes both protection circuit portions, the first protection circuit portion includes an electrical series circuit of a first discharge resistor and a first protection switch between the positive potential line and the reference potential line, and a first protection capacitor is electrically connected in parallel to the first discharge resistor, the second protection circuit portion includes an electrical series circuit of a second discharge resistor and a second protection switch between the negative potential line and the reference potential line, and a second protection capacitor is electrically connected in parallel to the second discharge resistor.

[0046] For example, not only is the protection capacitor electrically connected in parallel to the discharge resistor, but also an electrical series circuit composed of the protection capacitor and a protection resistor is electrically connected in parallel. There is an advantage that the current passing through the protection capacitor is limited by the protection resistor.

[0047] Thus, the protection circuit includes, for example, an electrical series circuit of a discharge resistor and a first protection switch between the positive potential line and the reference potential line, and an electrical series circuit of a discharge resistor and a second protection switch between the negative potential line and the reference potential line, and an electrical series circuit composed of the protection capacitor and a protection resistor is electrically connected in parallel to the discharge resistor. As an alternative, the protection circuit includes both protection circuit portions, the first protection circuit portion includes an electrical series circuit of a first discharge resistor and a first protection switch between the positive potential line and the reference potential line, and an electrical series circuit composed of the first protection capacitor and a protection resistor is electrically connected in parallel to the first discharge resistor, the second protection circuit portion includes an electrical series circuit of a second discharge resistor and a second protection switch between the negative potential line and the reference potential line, and an electrical series circuit composed of the second protection capacitor and a second protection resistor is electrically connected in parallel to the second discharge resistor.

[0048] In another embodiment, the protection circuit includes an electrical series circuit of an electrical resistor and a first protection switch between the positive potential line and the reference potential line, and an electrical series circuit of an electrical resistor and a second protection switch between the negative potential line and the reference potential line. The electrical resistor has a fixed resistance value, in particular a maximum of 800 Ω, in particular a maximum of 600 Ω, in particular lower than the human body resistance, i.e., significantly lower than the human body resistance, in particular a maximum of 200 Ω, in particular a maximum of 50 Ω or lower, for example lower than 5 Ω. Thereby, the energization to the human body is clearly reduced. As an alternative, the electrical resistor is, for example, a voltage-dependent resistor, and the resistance value of the voltage-dependent resistor is configured to be reduced, in particular gradually and significantly reduced, when the voltage is rising through the connection of the voltage-dependent resistor, and the maximum resistance value of the voltage-dependent resistor is, for example, a maximum of 800 Ω, in particular a maximum of 600 Ω, in particular lower than the human body resistance, i.e., significantly lower than the human body resistance, in particular a maximum of 200 Ω, in particular a maximum of 50 Ω or lower, for example lower than 5 Ω. Thus, this applies to all resistance values that the voltage-dependent resistor may have when a voltage occurs through the connection. Thereby, the energization to the human body is clearly reduced. Thus, the voltage-dependent resistor is configured such that its resistance value becomes even lower as the voltage across the connection increases.

[0049] An embodiment of such a protection circuit is a protection circuit optimized for components. In a protection circuit that serves to reduce CY electric shock, i.e., electric shock to a person caused by a Y capacitor, it is assumed that only one potential, i.e., only the positive potential or the negative potential, is connected to the frame ground through the human body resistance. When both potentials are connected to the frame ground, this is the same as a short circuit of the vehicle battery when used in a vehicle protection device, and is the same as a short circuit of a DC charging station, for example, a charging column, when used as a protection device of a DC charging station. Such a short circuit must be separated by a fuse or a current sensor and a cutoff device controlled thereby. From this, it is clear that it is never possible to apply the protection circuit to both the positive potential and the negative potential simultaneously. That is, the electrical resistance can be utilized for the safety of both potentials in the manner described above.

[0050] As an alternative, the protection circuit includes two protection circuit portions. The first protection circuit portion includes an electrical series circuit of a first electrical resistance and a first protection switch between the positive potential line and the reference potential line. The second protection circuit portion includes an electrical series circuit of a second electrical resistance and a second protection switch between the negative potential line and the reference potential line. Each electrical resistance is an electrical resistance having the fixed resistance value described above. Thereby, the energization to the human body is clearly reduced. As an alternative, each electrical resistance is a voltage-dependent electrical resistance, and is configured such that the resistance value of the voltage-dependent electrical resistance is reduced, particularly gradually increased, when the voltage rises through the connection portion of the voltage-dependent electrical resistance. The maximum resistance value of the voltage-dependent electrical resistance corresponds to the value listed above for the maximum resistance value. Therefore, this applies to all resistance values that the voltage-dependent electrical resistance can have when a voltage is generated through the connection portion. Thereby, the energization to the human body is clearly reduced. Thus, the voltage-dependent electrical resistance is configured such that its resistance value takes a lower resistance value as the voltage across the connection portion becomes higher.

[0051] In the embodiment of the protection circuit described above, where the same electrical resistance is used for an electrical series circuit that includes only one electrical resistance, i.e., has a first protection switch between the positive potential line and the reference potential line, and an electrical series circuit that has a second protection switch between the negative potential line and the reference potential line, in particular, it is provided that not both protection switches are operable to close simultaneously, or operate, but rather only one of the two protection switches operates.

[0052] The solution described above solves the problems associated with Y - capacitors in vehicles, in particular electric and hybrid vehicles, and in DC charging stations, as will be explained later. Such Y - capacitors are used as a measure to reduce the emission of EMC interference (EMC = electromagnetic compatibility). However, due to the Y - capacitor, the potential risk increases for reasons of high - voltage safety. In various standards, the charge contained in the Y - capacitor, or the energy stored, is cited as an indicator that threatens health. For example, in the standards SAE J1772, IEC60479 - 1 and - 2, the charge contained in the Y - capacitor is cited as an indicator that threatens health (C1 characteristic curve). The higher the operating voltage of the vehicle, the more difficult it becomes to comply with the limit values required by these standards. In part, alternative measures for complying with safety settings, such as, for example, enhanced, in particular doubled, electrical insulation, and so - called alternative measured values, are not allowed. Another standard, LV123 and related standards, for example, define a maximum energy content of 0.2 J for the charge of all Y - capacitors. If avoidance through alternative measures is allowed, for example, the enhanced, in particular doubled, electrical insulation already mentioned can be applied. However, this can only be implemented if all high - voltage systems connected to each other are correspondingly enhanced and insulated. That is, for example, in the case of DC charging, not only the vehicle but also the DC charging station, in particular the charging column, must be correspondingly enhanced and insulated. However, since there is no mandatory standard for this, it is conceivable that systems with different insulation designs are connected, and for this reason, safety requirements are not complied with.

[0053] These problems are solved by the circuit described above. By measuring the voltage for each high-voltage potential with respect to the reference potential, particularly with respect to the ground potential, a shift in the high-voltage potential with respect to the reference potential that can be attributed to the body current, i.e., particularly to one of the high-voltage potentials and the reference potential, and that can be attributed to physical contact between a human and the reference potential, is recognized. At the corresponding high-voltage potential where the voltage has dropped with respect to the reference potential, a resistor is added in order to reduce the voltage as quickly as possible. Thereby, the voltage between the corresponding high-voltage potential and the reference potential jumps sharply to a very low level, whereby the body current is reduced in proportion to the voltage. Thus, the solution described above enables the reduction of electric shock, particularly to a human body, caused by the Y capacitor. Compliance with the requirements described above becomes possible in this way. Even though the energy stored in the Y capacitor can become significantly high, it is likewise possible to limit the electrical energy of the Y capacitor embodied by the body resistance to less than 0.2 J.

[0054] When compared with a parallel circuit electrically connected in series with the respective protection switches of a capacitor connected in series with a protection resistor and a discharge resistor, the advantage of the protection circuit of a protection device having an electrical series circuit of a resistor or first and second resistors each having a protection switch between each potential line and the reference potential line is that the protection circuit of the solution described above does not require such a discharge resistor. Thereby, when a relatively low voltage is reached between the positive potential and the reference potential or between the negative potential and the reference potential, an automatic return to a state with a higher insulation resistance is made even though the first and / or second protection switches are still closed. In a protection circuit having a parallel circuit electrically connected in series with the respective protection switches of a capacitor connected in series with a protection resistor and a discharge resistor, the protection resistor will reduce the overall insulation value of the high-voltage system, particularly of a DC network, such as the on-vehicle electrical system of a vehicle, to an even lower value when the first or second protection switch is closed. This is avoided by the solution described above.

[0055] Furthermore, the protection circuit of the above-described solution can, in the case of a plurality of contacts with a high voltage potential, i.e., a positive or negative potential, occurring very rapidly in succession, each time serve as an equivalent conduction path to the body current. In contrast, in a protection circuit having a parallel circuit electrically connected in series with each protection switch of a capacitor and a discharge resistor connected in series with a protection resistor, it must wait until it is discharged to a very low voltage value through the discharge resistor of the protection capacitor, or such a protection circuit will have a protective effect that decreases due to body contact with a high voltage potential occurring rapidly and continuously. This is because the protection capacitor still has a residual voltage and not much energy can be stored anymore.

[0056] Therefore, the protection device described herein, especially its protection circuit, is preferably configured to be able to connect autonomously, that is, to be able to close the first and / or second protection switches, and after a short duration in this connected state, to be able to open each closed protection switch again. In that case, there is an advantage that communication with the upper control device inside the vehicle regarding how to implement any measures, such as the opening of a contactor, especially a charging contactor and / or a main contactor, or the discharging of a Y capacitor, etc., is omitted. For example, there is no defective protective cover for the high-voltage cable, and the recognition of constantly occurring insulation faults, that is, low insulation resistance, is preferably recognized by a separate instrument, such as an insulation monitor, and / or by measuring the high-voltage potential distribution. Such an instrument is not a component of the protection device and its protection circuit described herein and has no relevance to it. As described above, the protection device and its protection circuit described herein can be triggered even under repeated and thus quickly repeated human contact at very short intervals, and thus can guarantee human protection. For example, false triggering based on EMC interference does not lead to further measures in the vehicle, such as an incorrect stop of the high-voltage system. The autonomous function of the protection device, especially its protection circuit, enables a flexible and simple integration into an existing high-voltage system. Furthermore, the autonomous function reduces the safety requirements related to the protection device and its protection circuit, for example, eliminating the need for functions with fuses / communication with other control devices.

[0057] Different from a protection circuit having a parallel circuit electrically connected in series with each protection switch of a capacitor and a discharge resistor connected in series with a protection resistor, the solution described herein does not lead to an increase in the overall capacitance between the positive potential and the reference potential and between the negative potential and the reference potential.

[0058] Comparing a protection circuit having a parallel circuit electrically connected in series with respective protection switches of a capacitor and a discharge resistor connected in series with a protection resistor, with the solution described herein, it is clear that the uncharged capacitor has a relatively low impedance at the moment the protection circuit is connected, thereby enabling a more rapid reduction of the body current. Accordingly, the charge transmitted and the energy embodied in the human body are slightly lower at the first moment. However, in the subsequent time course, the capacitor is charged and its impedance increases accordingly. However, the electrical resistance configured as a voltage-dependent resistor in the form of a varistor in the solution described herein remains substantially constant until, for example, a varistor voltage of 80 V is reached, and accordingly, the body current can be reduced more rapidly in the subsequent process.

[0059] In one possible embodiment, the voltage-dependent electrical resistance and, accordingly, the one electrical resistance in the embodiment mentioned above having one electrical resistance, and, in the alternative embodiment mentioned above having both protection circuit portions and the first and second electrical resistances, the first electrical resistance and / or the second electrical resistance is configured as one varistor or as a series circuit and / or a parallel circuit of a plurality of varistors, with or without, for example, additional wiring. The additional wiring is, in particular, a series resistor for limiting the varistor current.

[0060] In one possible embodiment, the electrical resistance and / or the first electrical resistance and / or the second electrical resistance are electrically connected in series with the electrical protection resistance. That is, in the embodiment mentioned above having one electrical resistance, this electrical resistance is electrically connected in series with the electrical protection resistance. At this time, the electrical series circuit of the electrical resistance and the electrical protection resistance forms a common discharge network between the positive potential and the reference potential, and between the negative potential and the reference potential. In the alternative embodiment mentioned above having both protection circuit portions and the first and second electrical resistances, the first electrical resistance is electrically connected in series with the electrical protection resistance, and / or the second electrical resistance is electrically connected in series with the electrical protection resistance. At this time, the electrical series circuit of each electrical resistance and each electrical protection resistance forms a discharge network between the positive potential and the reference potential, or forms a discharge network between the negative potential and the reference potential. The electrical protection resistance or each electrical protection resistance serves to avoid damage to each protection switch due to an overly high current. For example, if it is always ensured by the electrical resistance or each electrical resistance in the embodiment as a voltage-dependent electrical resistance that the maximum energization is restricted so as not to lead to damage to each protection switch, the electrical protection resistance or each electrical protection resistance can be omitted.

[0061] As the human body resistance described above, that is, as the human body resistance, a resistance value of 500 Ω is assumed based on the specification of the standard that should be particularly observed.

[0062] In another embodiment, the protection circuit includes an electrical series circuit of an electrical protection capacitor, an electrical protection resistance, and a first protection switch between the positive potential line and the reference potential line, and an electrical series circuit of an electrical protection capacitor, an electrical protection resistance, and a second protection switch between the negative potential line and the reference potential line. An electrical discharge resistance is electrically connected in parallel to the protection capacitor and the protection resistance, and an electrical series circuit consisting of an electrical rapid discharge resistance and a rapid discharge switch is electrically connected in parallel to the protection capacitor, or to the protection capacitor and the protection resistance.

[0063] An embodiment of such a protection circuit is a protection circuit optimized for components. In a protection circuit that serves to reduce CY electric shock, i.e., electric shock to a person by a Y capacitor, it is assumed that only one potential, i.e., only the positive potential or the negative potential, is connected to the frame ground via the body resistance of a person. If both potentials are connected to the frame ground, this is the same as a short circuit of the vehicle battery when used in a vehicle protection device, and the same as a short circuit of, for example, a charging column of a DC charging station when used as a protection device of a DC charging station. Such a short circuit must be separated by a fuse or a current sensor and a cutoff device controlled thereby. From this, it is clear that it is never possible to apply the protection circuit simultaneously for the positive potential and the negative potential. That is, this embodiment of the protection circuit can be applied for the safety of both potentials in the manner described above.

[0064] In a method of operating this embodiment of the protection device, when a trigger criterion is satisfied, the first protection switch or the second protection switch is closed, reopened after the protection capacitor is charged, then the rapid discharge switch is closed, and reopened after the protection capacitor is discharged.

[0065] In this embodiment of the protection circuit, it is preferable that both protection switches are not particularly simultaneously, and only one of the two protection switches each time is operable to close, or provided to operate, particularly depending on the above.

[0066] In an alternative embodiment, the protection circuit includes two protection circuit portions. The first protection circuit portion includes an electrical series circuit of a first electrical protection capacitor, a first electrical protection resistor, and a first protection switch between a positive potential line and a reference potential line, with a first electrical discharge resistor electrically connected in parallel to the first protection capacitor and the first protection resistor, and an electrical series circuit consisting of a first electrical rapid discharge resistor and a first rapid discharge switch electrically connected in parallel to the first protection capacitor or the first protection resistor. The second protection circuit portion includes an electrical series circuit of a second electrical protection capacitor, a second electrical protection resistor, and a second protection switch between a negative potential line and a reference potential line, with a second electrical discharge resistor electrically connected in parallel to the second protection capacitor and the second protection resistor, and an electrical series circuit consisting of a second electrical rapid discharge resistor and a second rapid discharge switch electrically connected in parallel to the second protection capacitor or the second protection resistor.

[0067] In a method of correspondingly operating the protection device in that case, the first protection switch is closed when a trigger criterion is met, opened again after charging of the first protection capacitor, then the first rapid discharge switch is closed and opened again after discharging of the first protection capacitor, and / or the second protection switch is closed when a trigger criterion is met, opened again after charging of the second protection capacitor, then the second rapid discharge switch is closed and opened again after discharging of the second protection capacitor.

[0068] The above-described solution solves the problems associated with Y-capacitors in vehicles, particularly electric and hybrid vehicles, and DC charging stations, as will be explained later. Such Y-capacitors are used as a measure to reduce the emission of EMC interference (EMC = electromagnetic compatibility). However, due to the Y-capacitor, the potential risk becomes higher for reasons of high-voltage safety. For example, in standards SAE J1772, IEC60479-1 and -2, the charge contained in the Y-capacitor is listed as an indicator threatening health (C1 characteristic curve). The higher the operating voltage of the vehicle, the more difficult it becomes to comply with the limit values required by these standards. In part, alternative measures to comply with safety settings, such as enhanced, particularly doubled, electrical insulation, and so-called alternative measured values, are not allowed. Another standard, LV123 and related standards, define a maximum energy content of 0.2 J, for example, for the charge of all Y-capacitors. If avoidance through alternative measures is allowed, for example, the enhanced, particularly doubled, electrical insulation already mentioned can be applied. However, this can be implemented only when all high-voltage systems connected to each other are correspondingly enhanced and insulated. That is, in the case of DC charging, for example, not only the vehicle but also the DC charging station, particularly the charging column, must be correspondingly enhanced and insulated. However, since there is no mandatory standard for this, it is conceivable that systems with different insulation designs are connected, and for this reason, safety requirements are not complied with.

[0069] These problems are solved by the circuit described above. By measuring the voltage for each high-voltage potential with respect to a reference potential, particularly with respect to ground potential, a shift in the high-voltage potential with respect to the reference potential, which can be a consequence of the body current, i.e., particularly a consequence of the body contact between one of the high-voltage potentials and the reference potential and a human being, is recognized. At the corresponding high-voltage potential where the voltage with respect to the reference potential is decreasing, a discharge resistor and preferably an uncharged protection capacitor electrically in parallel therewith are added to reduce the voltage as quickly as possible. Thereby, the voltage between the corresponding high-voltage potential and the reference potential jumps sharply to a very low level, whereby the body current is reduced in proportion to the voltage. Thus, the solution described above enables the reduction of electric shock, particularly to the human body, caused by the Y capacitor. Compliance with the requirements described above becomes possible in this way. Although the energy stored in the Y capacitor can become significantly high, it is similarly possible to limit the electrical energy of the Y capacitor embodied by the body resistance to less than 0.2 J.

[0070] A combination of a discharge resistor and a protection capacitor connected electrically in parallel is particularly preferred. The discharge resistor ensures that the protection capacitor connected electrically in parallel is at zero voltage at the moment of connection. The protection capacitor acts after connection for the rapid discharge of the Y capacitor of the corresponding high-voltage potential.

[0071] Not only the protection capacitor but also an electrical series circuit consisting of the protection capacitor and a protection resistor are connected electrically in parallel with respect to the discharge resistor, which has the advantage that the current through the protection capacitor is limited by the protection resistor.

[0072] Furthermore, for at least the protection capacitor or for the protection capacitor and the protection resistor, an additional fast charge resistor electrically connected in parallel thereto enables the protection circuit of the above-described solution to provide an equivalent conduction path to body current in the case of a plurality of very rapidly successive contacts with a high voltage potential, i.e., a positive or negative potential. Without such an additional fast discharge resistor, the protection capacitor would be charged, for example, up to 80 V depending on its capacitance relative to the capacitance of the Y capacitor of the high voltage system after the first connection. When reconnected to such a voltage in a very short time, a slightly higher voltage would ultimately occur in the human body. This is because the charging in the protection capacitor has not been completely dissipated. Thus, the protection function would deteriorate with each subsequent temporary connection. Therefore, it would be necessary to wait until the protection capacitor is discharged to a very low voltage value through the discharge resistor, or such a protection circuit would have a protection effect that deteriorates due to body contact with a rapidly successive high voltage potential. This is because the protection capacitor still has a residual voltage and is no longer able to store much energy. This problem is solved by the above-described protection circuit. This is because the protection circuit is extended by a fast discharge circuit for rapidly discharging the protection capacitor. At this time, as described above, first each protection switch is connected. After the protection capacitor is charged, this protection switch is opened again. Then, the protection capacitor is discharged by the fast discharge resistor connected in parallel, and the fast discharge switch is closed. After the protection capacitor is discharged, the fast discharge switch is opened again, and the protection circuit is ready for use again.

[0073] The protection device described here, especially its protection circuit, is preferably configured to be able to connect autonomously, that is, to be able to close the first and / or second protection switches, and after a short duration in this connected state, to be able to open each closed protection switch again. In that case, for example, there is an advantage that communication with the upper control device inside the vehicle about how to implement any measures such as opening of a contactor, especially a charging contactor and / or a main contactor, or discharging of a Y capacitor is omitted. For example, there is no defective protection cover for the high-voltage cable, and it is preferable that recognition of constantly occurring insulation defects, that is, low insulation resistance, is recognized by a separate instrument, for example, an insulation monitor, and / or by measurement of the high-voltage potential distribution. Such an instrument is not a component of the protection device and its protection circuit described here and has no relevance to this. As described above, the protection device and its protection circuit described here can be triggered even under repeated and thus rapidly repeated human contact at very short intervals, and thus can guarantee human protection. For example, false triggering based on EMC interference does not lead to further measures in the vehicle such as false stopping of the high-voltage system. The autonomous function of the protection device, especially its protection circuit, enables flexible and simple integration into an existing high-voltage system. Furthermore, the autonomous function reduces the safety requirements related to the protection device and its protection circuit, for example, eliminating the need for functions with fuses / communication with other control devices.

[0074] Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

Brief Description of the Drawings

[0075]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0076] In all the figures, corresponding parts are denoted by the same reference numerals.

[0077] Hereinafter, with reference to FIGS. 1 to 6, a protection device 8 for an electric DC network 1, in particular for a high-voltage network, for example for an in-vehicle electrical system 3 of a vehicle 2, will be described. This protection device 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, 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. The reference potential M is in particular an electrical ground potential, in particular the vehicle ground potential when the protection device 8 is used in the vehicle 2, and for example the ground potential when the protection device 8 is used at a DC charging station 5.

[0078] Furthermore, the protection device 8 includes a protection circuit 9 for reducing an electric shock, in particular caused by the Y capacitors CyF+, CyF-, CyL+, CyL- of the electric DC network 1, in particular to a person, i.e., to the human body.

[0079] The protection circuit 9 includes a first protection switch SS1 between the positive potential line HV+L and the reference potential line ML, and a second protection switch SS2 between the negative potential line HV-L and the reference potential line ML. A plurality of trigger criteria are intended, and the first protection switch SS1 and / or the second protection switch SS2 are operable to close only when all of the set trigger criteria determined by the first voltage measuring device SV1 and / or the second voltage measuring device SV2 are met. The trigger criteria relate in particular to possible causes of faults / interferences that, when they occur, prevent the closing of the protection switches SS1, SS2. Preferably, at least one trigger criterion is set for each of these causes of faults / interferences, which is met when there is physical contact with one of the high voltage potentials HV+, HV-, i.e., when there is contact with a person, i.e., when there is contact with a human body, and is not met when one of the respective causes of faults occurs. The trigger, i.e., closing of each of the protection circuits SS1, SS2, takes place only when all of the set trigger criteria are met, i.e., when they are satisfied. Thereby, it is guaranteed that each of the protection switches SS1, SS2 is closed only when there is physical contact with one of the high voltage potentials HV+, HV-, i.e., when there is contact with a person, i.e., when there is contact with a human body, and false closing based on the occurrence of one or more of the causes of faults / interferences is avoided.

[0080] The on-vehicle electrical system 3 for a vehicle 2, in particular for an electric vehicle or a hybrid vehicle, in particular for a high-voltage on-vehicle electrical system, in particular the high-voltage on-vehicle electrical system 3, includes such a protection device 8.

[0081] The vehicle 2, in particular an electric vehicle or a hybrid vehicle, in particular includes such a protection device 8, in particular includes such an on-vehicle electrical system 3, in particular a high-voltage on-vehicle electrical system 3, which includes such a protection device 8.

[0082] In particular, a DC charging station 5 outside the vehicle, in particular a high-voltage DC charging station, for charging a vehicle 2, in particular an electric vehicle or a hybrid vehicle, and in particular a high-voltage battery 6 of such a vehicle 2, includes such a protection device 8.

[0083] The voltages measured by the voltage measuring devices SV1, SV2 are evaluated in particular as follows: - The difference of the currently occurring voltage dU from the positive potential line HV+L to the reference potential line ML and from the negative potential line HV-L to the reference potential line ML with respect to the previously determined voltage value is determined, and / or, - The voltage change dU / dt of the voltage from the positive potential line HV+L to the reference potential line ML and from the negative potential line HV-L to the reference potential line ML, i.e., over time, is determined, and / or, - With regard to the evaluation of the voltages from the positive potential line HV+L to the reference potential line ML and from the negative potential line HV-L to the reference potential line ML, in particular in both of the above determinations, the opposite sign is taken into account, and / or, - The periodic repetition of the occurring interference is taken into account.

[0084] That is, the trigger criteria in particular include the following: - The voltage difference of the currently occurring voltage between the positive potential line HV+L and the reference potential line ML and between the negative potential line HV-L and the reference potential line ML with respect to the previously determined voltage value, and / or, - The voltage change over time of the voltage occurring between the positive potential line HV+ and the reference potential line ML and between the negative potential line HV-L and the reference potential line ML, and / or, - The opposite sign of the voltage occurring between the positive potential line HV+L and the reference potential line ML and between the negative potential line HV-L and the reference potential line ML, and / or, - The non-existence of the periodic repetition of other trigger criteria.

[0085] The first protection switch SS1 and / or the second protection switch SS2 is operable only in particular in the following cases.

[0086] In one possible embodiment, the voltage difference over time between the voltage currently occurring between the positive potential line HV+L and the reference potential line ML and the previously determined voltage value for the voltage occurring between the negative potential line HV-L and the reference potential line ML exceeds a set limit value, which is 30V in one possible embodiment, and - the voltage change over time between the voltage occurring between the positive potential line HV+L and the reference potential line ML and the voltage occurring between the negative potential line HV-L and the reference potential line ML exceeds a set limit value, and - when there is an opposite sign between the voltage occurring between the positive potential line HV+L and the reference potential line ML and the voltage occurring between the negative potential line HV-L and the reference potential line ML.

[0087] For example, in order to evaluate the voltages determined by the first voltage measuring device SV1 and the second voltage measuring device SV2, and in order to activate the first protection switch SS1 and / or the second protection switch SS2 only when all the set trigger criteria determined by the first voltage measuring device SV1 and / or the second voltage measuring device SV2 are met, a common voltage evaluation unit 12 connected to the voltage measuring devices SV1, SV2 and the protection circuits SS1, SS2 is provided.

[0088] Figures 1 and 2, 3 and 4, and 5 and 6 show various embodiments of the protection circuit 9, and Figures 2, 4 and 6 show an optimized aspect of the components of each embodiment.

[0089] In the illustrated example, the high-voltage network 3 is the high-voltage vehicle electrical system 3 of the vehicle 2 to which the protection device 8 is preferably applied, particularly in an electric vehicle or a hybrid vehicle. However, the protection device 8 can alternatively or additionally be applied to a DC charging station 5 that can connect the vehicle 2 and other vehicles, particularly electric vehicles or hybrid vehicles, for the electrical charging of the high-voltage battery 6 of the vehicle 2. In that case, the DC network 1 includes the in-vehicle electrical system 3 of the vehicle 2, particularly the high-voltage network 3, and the DC charging station 5 when the vehicle 2 is connected. The high-voltage battery 6 of the vehicle 2 charged electrically at such a DC charging station 5 serves to provide electrical energy, particularly for at least one electric drive unit of the vehicle 2 for driving the vehicle 2.

[0090] In both the vehicle 2 and the DC charging station 5, the Y capacitors CyF+, CyF-, CyL+, CyL- are used as a measure to reduce the emission of EMC interference (EMC = electromagnetic compatibility). In particular, the Y capacitors CyF+, CyF-, CyL+, CyL- are often a more convenient and compact EMC filter measure compared to inductive interference suppression filters such as common-mode chokes and differential-mode chokes. Therefore, from the perspective of EMC, it is advisable to use Y capacitors CyF+, CyF-, CyL+, CyL- with a high capacitance value.

[0091] However, in an electrified vehicle 2, for example, in an electric vehicle or a hybrid vehicle, when a vehicle user comes into contact with the high-voltage potentials HV+, HV- in some cases and is simultaneously connected to the ground potential, the energy content of the Y capacitors CyF+, CyF-, CyL+, CyL- can become perceptible. In that case, the vehicle user will receive an electric shock. Depending on the magnitude of such an electric shock, this can endanger health. For example, it can lead to ventricular fibrillation or even death. Such an electric shock is a so-called "single fault" and should be avoided. Therefore, the energy content of such Y capacitors CyF+, CyF-, CyL+, CyL- is restricted by standards to eliminate the danger to the vehicle user.

[0092] That is, from the perspective of high-voltage safety, low capacitance values of the Y capacitors CyF+, CyF-, CyL+, and CyL- are preferred. For example, as defined by the LV123 regulation, the standard has requirements such as not exceeding a maximum energy content of 0.2 J in the Y capacitors CyF+, CyF-, CyL+, and CyL-, or there are requirements to provide so-called "alternative measurement values", that is, alternative measures such as enhanced insulation. However, this always results in the situation that when two high-voltage systems such as the vehicle 2 and the DC charging station 5 are connected, if enhanced insulation is selected as the "alternative measurement value", both participants must always have such enhanced insulation at the same time. However, it cannot be ensured at present.

[0093] For example, other standards such as SAE J1772, IEC60479-1, and IEC60479-2 do not list the energy content of the Y capacitors CyF+, CyF-, CyL+, and CyL- as a quantity threatening health that should not be exceeded, but list the charging amount that should not exceed the set value as a harmful mechanism. For example, for this purpose, a graph showing the relationship between the body current time and the body current value is published. Alternative measures such as enhanced insulation are not tolerated there.

[0094] Figures 1, 3, and 5 show the circuit structures of respective embodiments of the electrical DC network 1 configured as a high-voltage network during the DC charging process of the vehicle 2. Therefore, this DC network 1 includes the high-voltage in-vehicle electrical system 3 of the vehicle 2 and the DC charging station 5 connected thereto by the charging cable 4. In the illustrated embodiment here, the charging cable 4 is already connected to the connection contacts AK+, AK- of the DC charging connection part of the vehicle 2, and the charging contactors LS+, LS- of the vehicle 2 on the high-voltage potential lines HV+L, HV-L are still open.

[0095] On the left side, there is a charging station voltage source 13 and a charging station internal resistance RLS There is a DC charging station 5 having a Y capacitor CyL+, CyL-.

[0096] On its right side, a charging cable 4 is shown.

[0097] On its right side, a vehicle 2 and its high-voltage in-vehicle electrical system 3 are shown, including charging contactors LS+, LS-, Y capacitors CyF+, CyF-, for example, an EMC filter, for example, an X capacitor Cx of a DC intermediate circuit, a high-voltage battery 6 and its main contactors HS+, HS-. The high-voltage battery 6 is shown as an electric battery energy source 7 including a plurality of individual cells having, for example, a battery internal resistance R connected in series and / or in parallel. Batt It is shown as an electric battery energy source 7 including a plurality of individual cells having a body resistance R.

[0098] In addition to this, in this circuit diagram, a human body MK is shown, including a body resistance R and a circuit symbol representing an insulation fault IF, which is, for example, a fault in the positive potential line HV+ here when there is a fault in the charging cable 4. The insulation fault IF can also occur similarly in the negative potential line HV-. This is not shown in the figure. When the insulation fault IF occurs, the switch symbol is closed. When such an insulation fault IF occurs and contact occurs between one of the high-voltage potentials HV+, HV- and the reference potential and the human body MK, discharge occurs through the human body MK. K- It is shown as a human body MK including a body resistance R and a circuit symbol representing an insulation fault IF, which is, for example, a fault in the positive potential line HV+ here when there is a fault in the charging cable 4. The insulation fault IF can also occur similarly in the negative potential line HV-. This is not shown in the figure. When the insulation fault IF occurs, the switch symbol is closed. When such an insulation fault IF occurs and contact occurs between one of the high-voltage potentials HV+, HV- and the reference potential and the human body MK, discharge occurs through the human body MK.

[0099] To avoid such discharges passing through the human body MK or, at least, to reduce them to an acceptable level, particularly with regard to health hazards, a protection device 8 having a protection circuit 9 for reducing the electric shock by the Y capacitors CyF+, CyF-, CyL+, CyL- is provided. The protection device 8 includes, in all the examples shown, both voltage measuring devices SV1, SV2 and a protection circuit 9 having both protection switches SS1, SS2. Thereby, a discharge network is created between the positive potential HV+ and the reference potential M, particularly between the body ground, and a discharge network is created between the negative potential HV- and the reference potential M, particularly between the body ground. Such a discharge network is, in the examples shown in FIGS. 1, 3 and 5, the protection circuit portions 9.1, 9.2 of the protection circuit 9.

[0100] Each discharge network, that is, each of the protection circuit portions 9.1, 9.2, is preferably composed of an uncharged capacitor, hereinafter referred to as protection capacitors Cs, Cs1, Cs2, and a resistor electrically connected in parallel, hereinafter referred to as discharge resistors Re, Re1, Re2, in the embodiments shown in FIGS. 1 and 2. In addition, protection resistors Rs, Rs1, Rs2 are provided which are electrically connected in series to the protection capacitors Cs, Cs1, Cs2. For example, only the discharge resistors Re, Re1, Re2 may be provided, but in order to rapidly reduce the body current, this must be of very low resistance. However, there is the disadvantage that a low-resistance insulation failure is thereby caused. Therefore, hereinafter, attention is paid only to the combination of the protection capacitors Cs, Cs1, Cs2 and the discharge resistors Re, Re1, Re2.

[0101] Each discharge resistor Re, Re1, Re2 ensures that the protective capacitors Cs, Cs1, Cs2, which are electrically connected in parallel, are at zero voltage at the moment of connection. After connection, the protective capacitors act for the rapid discharge of the corresponding Y capacitors CyF+, CyF-, CyL+, CyL- of the high voltage potentials HV+, HV-. In the example of FIG. 1 shown, the protection device 8 is shown arranged to have a protection circuit 9 of the vehicle 2. However, the protection device may be arranged at the DC charging station 5 under the same function.

[0102] During the DC charging process, the high voltage potentials HV+, HV- do not necessarily have to be symmetrically distributed with respect to the reference potential M, but at least the insulation values to be observed for the high voltage potentials HV+, HV- must be guaranteed with respect to the reference potential M, for example, at 100 ohms / volt. Human contact with the high voltage potentials HV+, HV- is manifested as a decrease in insulation resistance and, as a result, as a shift of the high voltage potentials HV+, HV- with respect to the reference potential M.

[0103] The insulation monitor of the vehicle 2 or the DC charging station 5 periodically checks the insulation resistance, but the time span until an insulation fault IF is recognized is at most 30 seconds for the vehicle 2 or at most 2 minutes for the DC charging station 5, which is too long to protect a person from the shock caused by the energy stored in the Y capacitors CyF+, CyF-, CyF+, CyF- in the case of open insulation.

[0104] The functional form of the protection device 8 having a protection circuit 9 for reducing the Cy shock conforms to the limit values related to the potential hazards described, for example, in SAE J1772, IEC 60479-1, and IEC 60479-2. There, the charge flowing through the human body MK is cited as a harmful mechanism and is shown in a graph. Therefore, in order to minimize the flowing charge, the goal is the rapid recognition and reduction of the body current. The operation of the mechanical charging contactors LS+, LS- and / or the main contactors HS+, HS- alone is too slow for this purpose.

[0105] In the protection circuit 9 described above, a drop in the insulation value is quickly recognized by voltage measurement, and thereby, immediately, for example via a hardware circuit, the discharged protection capacitors Cs, Cs1, Cs2 are connected in parallel to the corresponding high voltage potentials HV+, HV- with respect to the body resistance R K or the Y capacitors CyF+, CyF-, CyL+, CyL-. In this way, the voltages at these high voltage potentials HV+, HV- and the reference potential M drop rapidly. The current passing through the human body MK also decreases in proportion to the voltage drop.

[0106] At this time, the discharge resistors Re, Re1, Re2 have two functions. On the one hand, the discharge resistors act for the complete discharge of the protection capacitors Cs, Cs1, Cs2 before their connection. On the other hand, after the connection, the discharge resistors accelerate the removal of the already reduced voltage between the high voltage potentials HV+, HV- and the reference potential M, and thereby, together with the continuously decreasing voltage, the current passing through the human body MK is reduced again. Each of the other high voltage potentials HV+, HV- raises the voltage to the same extent with respect to the reference potential M, but is not contacted by the human body MK and is therefore not critical. In the next step, the main contactors HS+, HS- of the high voltage battery 6 are opened, the contactors of the DC charging station 5 and / or the charging contactors LS+, LS- are opened, and in the last step, it is preferable to perform an active discharge of the X capacitor Cx and the Y capacitors CyF+, CyF- of the vehicle 2.

[0107] The protection device 8 having the protection circuit 9 can comply with the set standards such as the standard IEC60479-1. The higher the DC charging voltage, the higher the voltage generated through the Y capacitors CyF+, CyF-, CyL+, CyL-. As a result, the assumed body resistance R KUnder the condition, a current that increases in proportion to the voltage of the Y capacitors CyF+, CyF-, CyL+, and CyL- also occurs at the start of the contact process. The current passing through the body decreases particularly in an exponential form along with the process of capacitor discharge through the resistance. The current at the start of contact is calculated as the quotient of the voltage and the resistance. When assuming the maximum charging voltage of 920V, an initial value of the contact current of 460V / 1200 ohms = 383 mA can be obtained under the high-voltage potential distribution that is also assumed to be symmetric with respect to the reference potential M (460V for each Y capacitor). On the premise of this initial value of the current, this 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 in the so-called C1 characteristic curve of the standard SAE J 1772. The time duration of this current can be obtained through the calculation of the time constant t = R × C of capacitor discharge. The corresponding time duration (Y-axis) at this time corresponds to 3 × t. For example, a duration of about 100 ms in this state is still allowed. As a goal, a residual body current lower than 5 mA is selected, that is, the residual voltage must be lower than 6V.

[0108] For example, under the asymmetric high-voltage potential distribution with respect to the reference potential M, the higher the voltage of the Y capacitors CyF+, CyF-, CyL+, and CyL-, the shorter the maximum duration becomes. A current exceeding 500 mA is not allowed. This is because in that case, a maximum voltage of 600V will occur in the Y capacitors CyF+, CyF-, CyL+, and CyL-. If it exceeds this, the charging process must be aborted.

[0109] Therefore, it is possible to calculate whether the protection device 8 having the protection circuit 9 can comply with the required maximum current and time duration. When this condition is not met, the charging process must be aborted immediately. This is because further errors will lead to danger to human life. The input quantities for this calculation are the voltage measurements of the Y capacitors CyF+, CyF-, CyL+, and CyL- of both high-voltage potentials HV+ and HV-, the knowledge regarding the reaction speed of the circuit itself, and the numerical table of the maximum allowable current and duration.

[0110] Here, a voltage evaluation unit 12 is provided, where the voltages detected by the voltage measuring devices SV1 and SV2 are evaluated, and the protection switches SS1 and SS2 can be actuated accordingly. Furthermore, it may be intended that the voltage evaluation unit 12 can output other information, in particular to a control device that is slower than this or to the DC charging station 5. Information as an example is the opening or closing of the charging contactors LS+ and LS-, the interruption of the DC charging process, the opening or closing of the main contactors HS+ and HS- of the high-voltage battery 6, the start of the active discharge of the high-voltage intermediate circuit of the vehicle 2, and / or the information that since everything is normal, the DC charging process can be started.

[0111] Especially for the driving operation of the vehicle 2, for the AC charging operation, and for the assembly and maintenance work, in the case of the DC network 1 without the DC charging station 5, the only difference from the state in DC charging is the absence of the DC charging station 5. As failure mechanisms, for example, cable defects in the high-voltage cables as a result of an accident or defects in the housing of the high-voltage electronics are considered. Even when the high-voltage system is damaged during assembly or maintenance, the protection device 8 having the protection circuit 9 can reduce the charge amount.

[0112] The protection circuit 9 for reducing the Y shock caused by insulation failure IF remains the same as that described above. For this purpose, the protection device 8 having the protection circuit 9 is of course arranged in the vehicle 2. The function is the same as that for the insulation defect during DC charging described above. When a voltage drop between one of the high-voltage potentials HV+ and HV- and the reference potential M is recognized, the respective protection capacitors Cs, Cs1, and Cs2 are additionally connected, and the total capacitance of the Y capacitors CyF+, CyF-, CyL+, and CyL- of the corresponding high-voltage potential HV+ and HV- is discharged. It is more preferable that the opening of the main contactors HS+ and HS- of the high-voltage battery 6 is instructed, and the active discharge of the X capacitor Cx and both Y capacitors CyF+ and CyF- of the vehicle 2 is started. The charging contactors LS+ and LS- are already open before that and are kept open.

[0113] Figure 2 shows a component-optimized protection circuit 9. In the protection circuit 9 for reducing Cy shock, only one high-voltage potential HV+, HV- is connected to the reference potential M, for example the frame ground, via the body resistance R K It is assumed that both high-voltage potentials HV+, HV- are connected to the reference potential M, especially the frame ground. If both high-voltage potentials HV+, HV- are connected to the reference potential M, especially the frame ground, this is equivalent to a short circuit of the high-voltage battery 6 or the DC charging station 5, and such a short circuit must be separated by a fuse or a current sensor and a cutoff device controlled thereby.

[0114] From this, it is clear that it is never possible to apply the protection circuit 9 for reducing Cy shock simultaneously for the positive potential HV+ and the negative potential HV-. Therefore, as shown in Figure 2, a single protection capacitor Cs, a discharge resistor Re, and further a protection resistor Rs can be applied for the safety of both high-voltage potentials HV+, HV-. That is, two protection circuits 9.1, 9.2 are not necessary. The voltage measurement by both voltage protection devices SV1, SV2 for the connection of the protection circuit 9, and both protection switches SS1, SS2 must still be maintained. Figure 2 shows such component optimization. This is meaningful, for example, when the discharge resistor Re must also have a relatively high component value based on the high operating voltage in the vehicle 2 and the DC charging station 5 and the large capacitance of the Y capacitors CyF+, CyF-, CyL+, CyL-. Here, the protection device 8, especially its protection circuit 9, is reduced only by the necessary additional cost to be integrated into the vehicle 2 or the DC charging station 5. The connection parts AHV+, AHV-, AM to the positive potential HV+, the negative potential HV-, and the reference potential M can be made very small. This is because only a current in the order of milliseconds flows during a fault. Otherwise, the connection parts AHV+, AHV-, AM are currentless and only serve for voltage measurement. As a result, the rapid integration of the protection device 8 having the protection circuit 9 into the existing high-voltage system is possible with few modifications. If there is sufficient planning time, of course, this function can also be integrated into the existing equipment.

[0115] That is, as shown in FIG. 2, the protection circuit 9 includes an electrical series circuit 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 an electrical series circuit of the same discharge resistor Re and a second protection switch SS2 between the negative potential line HV-L and the reference potential ML.

[0116] Alternatively, as shown in FIG. 1, the protection circuit 9 includes two protection circuit portions 9.1 and 9.2. The first protection circuit portion 9.1 includes an electrical series circuit 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 portion 9.2 includes an electrical series circuit of a second discharge resistor Re2 and a second protection switch SS2 between the negative potential line HV-L and the reference potential ML.

[0117] For the discharge resistors Re, Re1, and Re2, as already described above, it is preferable that the protection capacitors Cs, Cs1, and Cs2 are electrically connected in parallel. That is, as shown in FIG. 2, a single protection capacitor Cs is electrically connected in parallel to a single discharge resistor Re, or, as shown in FIG. 1, the respective protection capacitors Cs1 and Cs2 are electrically connected in parallel to the discharge resistors Re1 and Re2 of the respective protection circuit portions 9.1 and 9.2.

[0118] That is, as shown in FIG. 2, the protection circuit 9 includes an electrical series circuit 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 an electrical series circuit of a discharge resistor Re and a second protection switch SS2 between the negative potential line HV-L and the reference potential ML. The protection capacitor Cs is electrically connected in parallel to the discharge resistor Re. As an alternative, as shown in FIG. 1, the protection circuit 9 includes both protection circuit portions 9.1 and 9.2. The first protection circuit portion 9.1 includes an electrical series circuit 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 first protection capacitor Cs1 is electrically connected in parallel to the first discharge resistor Re1. The second protection circuit portion 9.2 includes an electrical series circuit of a second discharge resistor Re2 and a second protection switch SS2 between the negative potential line HV-L and the reference potential ML. The second protection capacitor Cs2 is electrically connected in parallel to the second discharge resistor Re2.

[0119] For the discharge resistors Re, Re1, and Re2, in the example illustrated here, not only are the protection capacitors Cs, Cs1, and Cs2 electrically connected in parallel, but also an electrical series circuit composed of the protection capacitors Cs, Cs1, and Cs2 and the protection resistors Rs, Rs1, and Rs2 is electrically connected in parallel.

[0120] That is, as shown in FIG. 2, the protection circuit 9 includes an electrical series circuit 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 an electrical series circuit of a discharge resistor Re and a second protection switch SS2 between the negative potential line HV-L and the reference potential ML. An electrical series circuit composed of a protection capacitor Cs and a protection resistor Rs is electrically connected in parallel to the discharge resistor Re. As an alternative, as shown in FIG. 1, the protection circuit 9 includes both protection circuit portions 9.1 and 9.2. The first protection circuit portion 9.1 includes an electrical series circuit 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. An electrical series circuit composed of a first protection capacitor Cs1 and a first protection resistor Rs1 is electrically connected in parallel to the first discharge resistor Re1. The second protection circuit portion 9.2 includes an electrical series circuit of a second discharge resistor Re2 and a second protection switch SS2 between the negative potential line HV-L and the reference potential ML. An electrical series circuit composed of a second protection capacitor Cs2 and a second protection resistor Rs2 is electrically connected in parallel to the second discharge resistor Re2.

[0121] FIGS. 3 and 4 show another embodiment of the protection device 8, particularly its protection circuit 9, and FIG. 4 shows an optimized component configuration.

[0122] Each discharge network, that is, each protection circuit portion 9.1 and 9.2 in FIG. 3, is preferably composed of an electrical series circuit of resistors R, R1, R2 and protection resistors Rs, Rs1, Rs2.

[0123] The electrical resistors R, R1, R2 are voltage-dependent resistors in the illustrated example, and are configured such that the resistance value of the voltage-dependent resistor is reduced, particularly gradually increased, when the voltage rises through the connection of the voltage-dependent resistor. The maximum resistance value of the voltage-dependent resistor is, for example, at most 800 Ω, particularly at most 600 Ω, particularly the human body resistance R KRather, that is, lower than the human body resistance, particularly significantly lower, particularly up to 200 Ω at most, particularly at most 50 Ω or lower than this, for example lower than 5 Ω. Thereby, the energization to the human body is clearly reduced. The voltage-dependent resistance is configured, for example, as a single varistor, or as a series circuit and / or parallel circuit of a plurality of varistors with or without additional wiring, for example.

[0124] As an alternative, the electrical resistances R, R1, R2 are particularly at most 800 Ω, particularly at most 600 Ω, particularly the human body resistance R K Rather, that is, lower than the human body resistance, particularly significantly lower, particularly at most 200 Ω, particularly at most 50 Ω or lower than this, for example lower than 5 Ω, and is an electrical resistance having a fixed resistance value. Thereby, the energization to the human body is also clearly reduced.

[0125] For example, only the resistances R, R1, R2 may be provided. The electrical protection resistances Rs, Rs1, Rs2 serve to avoid damage to the respective protection switches SS1, SS2 due to an overly high current. Therefore, for example, if it is always ensured that the maximum energization is restricted by the electrical resistances R, R1, R2 in an embodiment particularly as a voltage-dependent electrical resistance so as not to lead to damage to the respective protection switches SS1, SS2, the electrical protection resistances R, R1, R2 can be omitted.

[0126] In the example illustrated in FIG. 3, a protection device 8 having a protection circuit 9 is shown disposed in a vehicle 2. However, the protection device may be disposed at a DC charging station 5 under the same function.

[0127] In the protection device 8 illustrated here, particularly in the protection circuit 9, particularly in each protection circuit portion 9.1, 9.2, fault recognition is performed through voltage measurement with respect to the reference potential M.

[0128] During the DC charging process in which the charging contactors LS+, LS- shown open in Fig. 3 are closed, the high voltage potentials HV+, HV- do not necessarily have to be symmetrically distributed with respect to the reference potential M, but at least the insulation values to be observed for the high voltage potentials HV+, HV- must be guaranteed, for example, at 100 ohms / volt with respect to the reference potential M. Human contact with the high voltage potentials HV+, HV- becomes apparent as a decrease in insulation resistance and, as a result, as a shift of the high voltage potentials HV+, HV- with respect to the reference potential M.

[0129] The insulation monitors of the vehicle 2 or the DC charging station 5 periodically inspect the insulation resistance, but the time span until an insulation fault IF is recognized is at most 30 seconds for the vehicle 2 or at most 2 minutes for the DC charging station 5, which is too long to protect a person from the shock due to the energy stored in the Y capacitors CyF+, CyF-, CyF+, CyF- in the case of open insulation.

[0130] The functional form of the protection device 8 having the protection circuit 9 for reducing the Cy shock conforms to the limit values regarding potential hazards described, for example, in SAE J1772, IEC 60479-1, and IEC 60479-2. There, the amount of charge flowing through the human body MK is cited as a harmful mechanism and is shown in a graph. Therefore, in order to minimize the flowing charge, the goal is the rapid recognition and reduction of the body current. The operation of the mechanical charging contactors LS+, LS- and / or the main contactors HS+, HS- alone is too slow for this purpose.

[0131] In the protection circuit 9 described above, a drop in the insulation value is rapidly recognized by voltage measurement, and thereby immediately, for example, via a hardware circuit, the electrical resistances R, R1, R2 are connected in parallel with the body resistance R K or the Y capacitors CyF+, CyF-, CyL+, CyL- corresponding to the high voltage potentials HV+, HV-. In this way, the voltages at this high voltage potentials HV+, HV- and the reference potential M drop rapidly. The energization through the human body MK also decreases in proportion to the voltage drop.

[0132] The other high voltage potentials HV+ and HV- each increase the voltage to a similar level with respect to the reference potential M, but are not contacted by the human body MK and are thus not critical.

[0133] In the next step, the main contactors HS+ and HS- of the high voltage battery 6 are opened, the contactors of the DC charging station 5 and / or the charging contactors LS+ and LS- are opened, and in the last step, the active discharge of the X capacitor Cx and the Y capacitors CyF+ and CyF- of the vehicle 2 is preferably carried out.

[0134] The protection device 8 having the protection circuit 9 can comply with the set standards such as the standard IEC60479-1. The higher the DC charging voltage, the higher the voltage generated through the Y capacitors CyF+, CyF-, CyL+, and CyL-. As a result, under the assumed body resistance R K a current that increases in proportion to the voltage of the Y capacitors CyF+, CyF-, CyL+, and CyL- also occurs at the start of the contact process. The current passing through the body decreases particularly in an exponential form as it follows the process of capacitor discharge through the resistance. The current at the start of contact is calculated as the quotient of the voltage and the resistance. Assuming a maximum charging voltage of 920V, an initial contact current value of 460V / 1200 ohms = 383 mA is obtained under the high voltage potential distribution that is also assumed to be symmetric with respect to the reference potential M (460V for each Y capacitor). Based on this initial value of the current, this current can be converted to a sinusoidal alternating current by dividing by root 6. This corresponds to the value on the X-axis in the so-called C1 characteristic curve of the standard SAE J 1772. The time duration of this current can be obtained by calculating the time constant t = R × C of the capacitor discharge. At this time, the corresponding time duration (Y-axis) corresponds to 3 × t. For example, a duration of about 100 ms in this state is still allowed. As a goal, a residual body current lower than 5 mA is selected, that is, the residual voltage must be lower than 6V.

[0135] For example, under an asymmetric high-voltage potential distribution with respect to the reference potential M, the higher the voltage across the Y capacitors CyF+, CyF-, CyL+, CyL-, the shorter the maximum duration will be. A current exceeding 500 mA is not allowed. This is because in that case, a maximum voltage of 600 V will be generated across the Y capacitors CyF+, CyF-, CyL+, CyL-. If this is exceeded, the charging process must be aborted.

[0136] Therefore, it is possible to calculate whether the protection device 8 having the protection circuit 9 can comply with the required maximum current-duration. When this condition is not met, the charging process must be aborted immediately. This is because further errors will lead to personal danger. The input quantities for this calculation are the voltage measurements across the Y capacitors CyF+, CyF-, CyL+, CyL- of both high-voltage potentials HV+, HV-, the knowledge regarding the circuit's own reaction speed, and the numerical table of the maximum allowable current-duration.

[0137] The protection circuit 9 can serve as an equivalent conduction path to body current in the case of a plurality of contacts that proceed very rapidly in succession with the high voltage potentials HV+, HV-. Therefore, the protection device 8 described here, especially its protection circuit 9, can be autonomously connected, that is, the first and / or second protection switches SS1, SS2 can be closed, and after a short duration in this connected state, the respective closed protection switches SS1, SS2 can be opened again. In that case, there is an advantage that communication with the upper control device inside the vehicle 2 regarding how to implement any measures such as opening the charging contactors LS+, LS- and / or the main contactors HS+, HS- and discharging the Y capacitors CyF+, CyF-, CyL+, CyL- is omitted. For example, there is no defective protective cover for the high voltage cable, and the recognition of constantly occurring insulation faults, that is, low insulation resistance, is preferably recognized by a separate instrument, for example, an insulation monitor, and / or by measuring the high voltage potential distribution. Such an instrument is not a component of the protection device 8 and its protection circuit 9 described here and has no relevance to this. As described above, the protection device 8 and its protection circuit 9 described here can be triggered even under repeated and rapid contacts by a person at very short intervals, thus ensuring the protection of the person. For example, false triggering due to EMC interference does not lead to further measures in the vehicle 2 such as a false stop of the high voltage system. The autonomous function of the protection device 8, especially its protection circuit 9, enables the realization of a flexible and simple integration into an existing high voltage system. Furthermore, due to the autonomous function, the safety requirements related to the protection device 8 and its protection circuit 9 are reduced, for example, functions with fuses / communication with other control devices are no longer required.

[0138] The protection device 8 can also be applied in the case of the DC network 1 without the DC charging station 5, especially for the driving operation of the vehicle 2, for the AC charging operation, and for the assembly and maintenance work. The only difference from the case of DC charging is the absence of the DC charging station 5. As failure mechanisms, for example, defects in the high-voltage cable as a result of an accident, or defects in the housing of the high-voltage electronics, etc. are considered. Even when the high-voltage system is damaged during assembly or maintenance, the protection device 8 having the protection circuit 9 can reduce the charge amount.

[0139] At this time, the protection circuit 9 for reducing the Y shock caused by the insulation fault IF remains the same as that described above. For this purpose, the protection device 8 having the protection circuit 9 is of course arranged in the vehicle 2. The function is the same as that for the insulation defect during DC charging described above. When a voltage drop between one of the high-voltage potentials HV+, HV- and the reference potential M is recognized, the respective electrical resistances R, R1, R2 are additionally connected, and the total capacitance of the Y capacitors CyF+, CyF-, CyL+, CyL- of the corresponding high-voltage potentials HV+, HV- is discharged. It is more preferable that the main contactors HS+, HS- of the high-voltage battery 6 are instructed to open, and the active discharge of the X capacitor Cx and both Y capacitors CyF+, CyF- of the vehicle 2 is started. The charging contactors LS+, LS- are already open before and are kept open.

[0140] Figure 4 shows the protection circuit 9 optimized for components. In the protection circuit 9 for reducing the Cy shock, it is assumed that only one of the high-voltage potentials HV+, HV- is connected to the reference potential M, for example, the frame ground, via the body resistance R K If both high-voltage potentials HV+, HV- are connected to the reference potential M, especially the frame ground, this is the same as a short circuit of the high-voltage battery 6 or the DC charging station 5, and such a short circuit must be separated by a fuse or a current sensor and a circuit breaker controlled thereby.

[0141] From this, it is clear that the protection circuit 9 for reducing the Cy shock cannot be applied simultaneously to the positive potential HV+ and the negative potential HV-. Therefore, as shown in FIG. 4, a single resistor R and, optionally, a single protection resistor Rs can be applied for the safety of both high-voltage potentials HV+, HV-. That is, two protection circuits 9.1, 9.2 are not necessary. The voltage measurement by both voltage protection devices SV1, SV2 for the connection of the protection circuit 9, and both protection switches SS1, SS2 must continue to exist.

[0142] In FIG. 4, the protection device 8, and in particular its protection circuit 9, is reduced only by the necessary additional cost to be integrated into the vehicle 2 or the DC charging station 5. The connections AHV+, AHV-, AM to the positive potential HV+, negative potential HV-, and reference potential M can be made very small. This is because only a current in the millisecond range flows during a fault. Otherwise, the connections AHV+, AHV-, AM are currentless and only serve for voltage measurement. As a result, the rapid integration of the protection device 8 having the protection circuit 9 into the existing high-voltage system is possible with few modifications. If there is sufficient planning time, of course, this function can also be integrated into the existing equipment.

[0143] That is, as shown in FIG. 4 for example, the protection circuit 9 includes an electrical series circuit of an electrical resistor R between the positive potential line HV+L and the reference potential ML and a first protection switch SS1, and an electrical series circuit of the same discharge resistor R between the negative potential line HV-L and the reference potential ML and a second protection switch SS2.

[0144] The electrical resistor R is, for example, an electrical resistor having a fixed resistance value as listed above, or a voltage-dependent resistor as shown in FIG. 4, and the resistance value of the voltage-dependent electrical resistor is configured to be reduced, particularly gradually increased, when the voltage rises through the connection of the voltage-dependent electrical resistor, and the maximum resistance value is provided as described above. Thereby, the energization to the human body is clearly reduced.

[0145] The resistor R configured as a voltage-dependent electrical resistor is configured, for example, as a single varistor or as a series circuit and / or parallel circuit of a plurality of varistors with and / or without additional wiring.

[0146] As an alternative, the protection circuit 9 includes two protection circuit parts 9.1, 9.2 as shown in FIG. 3. The first protection circuit part 9.1 includes an electrical series circuit of a first electrical resistor R1 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 includes an electrical series circuit of a second electrical resistor R2 and a second protection switch SS2 between the negative potential line HV-L and the reference potential ML.

[0147] Each of the electrical resistors R1, R2 is, for example, an electrical resistor having a fixed resistance value as mentioned above or a voltage-dependent resistor as shown in FIG. 3. The resistance value of the voltage-dependent electrical resistor is configured to be reduced, particularly gradually and significantly, when the voltage rises through the connection part of the voltage-dependent electrical resistor, and the maximum resistance value is provided as described above. Thereby, the energization to the human body is significantly reduced.

[0148] Each of the resistors R1, R2 configured as a voltage-dependent electrical resistor is configured, for example, as a single varistor or as a series circuit and / or parallel circuit of a plurality of varistors with and / or without additional wiring.

[0149] In one possible embodiment, as already described above, the electrical resistors R, R1, R2 are electrically connected in series with the protective resistors Rs, Rs1, Rs2. That is, as shown in FIG. 4, a single electrical resistor R is electrically connected in series with a single electrical protective resistor Rs, or as shown in FIG. 3, the electrical resistors R1, R2 of the respective protection circuit parts 9.1, 9.2 are electrically connected in series with the electrical protective resistors Rs1, Rs2 of the respective protection circuit parts 9.1, 9.2.

[0150] At this time, the electrical series circuits of the respective electrical resistances R, R1, R2 and the respective electrical protection resistances Rs, Rs1, Rs2 form a discharge network between the positive potential HV+ and the reference potential M, or form a discharge network between the negative potential HV− and the reference potential M. The electrical protection resistance Rs or the respective electrical protection resistances Rs1, Rs2 serve to avoid breakage of the respective protection switches SS1, SS2 due to an overly high current. For example, if it is always ensured that the maximum energization is restricted by the electrical resistance R or the respective electrical resistances R1, R2 in the embodiment as a voltage-dependent electrical resistance so as not to lead to breakage of the respective protection switches SS1, SS2, the electrical protection resistance Rs or the respective electrical protection resistances Rs1, Rs2 can be omitted.

[0151] Therefore, when the electrical protection resistance Rs or the respective protection resistances Rs1, Rs2 are present, the protection circuit 9, as shown in FIG. 4, includes the electrical series circuit of the electrical resistance R, the electrical protection resistance Rs, and the first protection switch SS1 between the positive potential line HV+L and the reference potential line ML, and the electrical series circuit of the resistance R, the electrical protection resistance Rs, and the second protection switch SS2 between the positive potential line HV+L and the reference potential line ML, or the protection circuit 9 includes both protection circuit portions 9.1, 9.2 as shown in FIG. 3. The first protection circuit portion 9.1 includes the electrical series circuit of the first electrical resistance R1, the first electrical protection resistance Rs1, and the first protection switch SS1 between the positive potential line HV+L and the reference potential line ML, and the second protection circuit portion 9.2 includes the electrical series circuit of the second electrical resistance R2, the second electrical protection resistance Rs2, and the second protection switch SS2 between the positive potential line HV+L and the reference potential line ML.

[0152] The human body resistance R described above K is assumed to have a resistance value of 500 Ω, that is, as the body resistance of a person, that is, of the human body MK, based on the specification of the standard that should be particularly observed.

[0153] FIGS. 5 and 6 show another embodiment of the protection device 8, particularly of its protection circuit 9, and FIG. 6 shows a component-adapted aspect.

[0154] Each discharge network, that is, each protection circuit portion 9.1, 9.2 in FIG. 5, is preferably composed here, in the following, of an uncharged capacitor, hereinafter referred to as protection capacitors Cs, Cs1, Cs2, and a resistor electrically connected in parallel, hereinafter referred to as discharge resistors Re, Re1, Re2. In addition to this, protection resistors Rs, Rs1, Rs2 electrically connected in series to the protection capacitors Cs, Cs1, Cs2 are provided. Further, rapid discharge resistors Rse, Rse1, Rse2 are provided in parallel to the protection capacitors Cs, Cs1, Cs2 and also, for example, in parallel to the protection resistors Rs, Rs1, Rs2, and are electrically connected in series to rapid discharge switches Se, Se1, Se2.

[0155] Each of the discharge resistors Re, Re1, Re2 ensures that the protection capacitors Cs, Cs1, Cs2 connected in parallel are at zero voltage at the moment of connection. After connection, the protection capacitors act for the rapid discharge of the corresponding Y capacitors CyF+, CyF-, CyL+, CyL- of the high voltage potentials HV+, HV-.

[0156] With the additional rapid discharge resistors Rse, Rse1, and Rse2, the protection circuit 9 can serve as an equivalent conduction path to body current in the case of a plurality of very rapidly successive contacts with the high voltage potentials HV+ and HV-. Without such additional rapid discharge resistors Rse, Rse1, and Rse2, the protection capacitors Cs, Cs1, and Cs2 would be charged up to, for example, 80V depending on their capacitance relative to the capacitance of the Y capacitors CyF+, CyF-, CyL+, and CyL- of the high voltage system after the first connection. If connected to such a voltage again in a very short time, a slightly higher voltage would ultimately occur in the human body MK. This is because the charging in the protection capacitors Cs, Cs1, and Cs2 has not been completely dissipated. Thus, the protection function would deteriorate with each subsequent temporary connection. Therefore, it would be necessary to wait until the protection capacitors Cs, Cs1, and Cs2 are discharged through the discharge resistors Re, Re1, and Re2 to a very low voltage value, or such a protection circuit would have a deteriorating protection effect due to body contact with the rapidly and continuously occurring high voltage potentials HV+ and HV-. This is because the protection capacitors Cs, Cs1, and Cs2 still have a residual voltage and cannot store much energy. This problem is solved by the protection circuit 9 described above. This is because the protection circuit 9 is extended by a rapid discharge circuit for rapidly discharging the protection capacitors Cs, Cs1, and Cs2. In this case, first, the respective protection switches SS1 and SS2 are connected. After the protection capacitors Cs, Cs1, and Cs2 are charged, the protection switches SS1 and SS2 are opened again. Then, the discharge of the protection capacitors Cs, Cs1, and Cs2 is performed by the rapid discharge resistors Rse, Rse1, and Rse2 located in parallel, and the rapid discharge switches Se, Se1, and Se2 are closed. After the discharge of the protection capacitors Cs, Cs1, and Cs2, the rapid discharge switches Se, Se1, and Se2 are opened again, and the protection circuit 9 is ready for use again.

[0157] The protection device 8 described here, and in particular its protection circuit 9, can be connected autonomously, i.e., it can close the first and / or second protection switches SS1, SS2, and can open each closed protection switch SS1, SS2 again after a short duration in this connected state. It is preferably provided that it is conceived in this way. In that case, there is an advantage that communication with the upper control device inside the vehicle 2 is omitted regarding how to implement any measures, such as opening of contactors, in particular charging contactors LS+, LS− and / or main contactors HS+, HS−, and discharging of Y capacitors CyF+, CyF−, CyL+, CyL−. For example, there is no defective protection cover for the high-voltage cable, and it is preferable that the recognition of constantly occurring insulation defects, i.e., low insulation resistance, is recognized by a separate instrument, for example, an insulation monitor, and / or by measuring the high-voltage potential distribution. Such an instrument is not a component of the protection device 8 and its protection circuit 9 described here and has no relevance to this. As described above, the protection device 8 and its protection circuit 9 described here can be triggered even under repeated and thus rapidly repeated human contact at very short intervals, and thus human protection can be ensured. For example, false triggering based on EMC interference does not lead to further measures in the vehicle 2, such as an incorrect stop of the high-voltage system. The autonomous function of the protection device 8, in particular its protection circuit 9, enables a flexible and simple integration into an existing high-voltage system. Furthermore, due to the autonomous function, the safety requirements regarding the protection device 8 and its protection circuit 9 are reduced, for example, a function with a fuse / communication with other control devices is not required.

[0158] In the example illustrated in FIG. 5, the protection device 8 having the protection circuit 9 is arranged and illustrated in the vehicle 2. However, the protection device may be arranged at the DC charging station 5 under the same function.

[0159] In the protection device 8 shown here, particularly in the protection circuit 9, and particularly in each of the protection circuit portions 9.1, 9.2, fault recognition is performed through voltage measurement with respect to the reference potential M.

[0160] During the DC charging process in which the charging contactors LS+, LS- shown open in Fig. 5 are closed, the high voltage potentials HV+, HV- do not necessarily have to be symmetrically distributed with respect to the reference potential M, but at least the insulation values to be observed for the high voltage potentials HV+, HV- must be guaranteed with respect to the reference potential M, for example, at 100 ohms / volt. Human contact with the high voltage potentials HV+, HV- becomes apparent as a decrease in the insulation resistance and, as a result, as a shift of the high voltage potentials HV+, HV- with respect to the reference potential M.

[0161] The insulation monitors of the vehicle 2 or the DC charging station 5 periodically inspect the insulation resistance, but the time span until an insulation fault IF is recognized is at most 30 seconds for the vehicle 2 or at most 2 minutes for the DC charging station 5, which is too long to achieve protection against electric shock to humans in the case of discharge insulation from the energy stored in the Y capacitors CyF+, CyF-, CyL+, CyL-.

[0162] The functional form of the protection device 8 having the protection circuit 9 for reducing Cy shock conforms to the limit values regarding potential hazards described, for example, in SAE J1772, IEC 60479-1, and IEC 60479-2. There, the amount of charge flowing through the human body MK is cited as a harmful mechanism and is shown in a graph. Therefore, in order to minimize the flowing charge, the goal is the rapid recognition and reduction of the body current. The operation of the mechanical charging contactors LS+, LS- and / or the main contactors HS+, HS- alone is too slow for this purpose.

[0163] In the protection circuit 9 described above, a decrease in the insulation value is rapidly recognized by voltage measurement, and thereby, immediately, for example, via a hardware circuit, the discharged protection capacitors Cs, Cs1, Cs2 are connected to the corresponding high voltage potentials HV+ and HV- with respect to the body resistance R. Kor is connected in parallel with the Y capacitors CyF+, CyF-, CyL+, CyL-. In this way, the voltages at this high voltage potential HV+, HV- and the reference potential M drop sharply. The current passing through the human body MK also decreases in proportion to the voltage drop.

[0164] At this time, the discharge resistors Re, Re1, Re2 have two functions. On the one hand, the discharge resistors act for the complete discharge of the protection capacitors Cs, Cs1, Cs2 before connection. On the other hand, after connection, the discharge resistors accelerate the removal of the already reduced voltage between the high voltage potentials HV+, HV- and the reference potential M, so that, together with the continuously decreasing voltage, the current passing through the human body MK is reduced again. Each of the other high voltage potentials HV+, HV- raises the voltage to the same extent with respect to the reference potential M, but is not contacted by the human body MK and is therefore not critical. In the next step, the main contactors HS+, HS- of the high voltage battery 6, the contactors of the DC charging station 5, and / or the charging contactors LS+, LS- can be opened, and in the last step, the active discharge of the X capacitor Cx and the Y capacitors CyF+, CyF- of the vehicle 2 can be carried out. However, as described above, in the solution described here, such opening of the contactors is not carried out, but at least by the protection device 8, and in the manner described above, the rapid discharge of the protection capacitors Cs, Cs1, Cs2 by the rapid discharge resistors Rse, Rse1, Rse2 is carried out, whereby the protection circuit 9 is quickly ready for use again.

[0165] The protection device 8 having the protection circuit 9 can comply with the set standards such as the standard IEC60479-1. The higher the DC charging voltage, the higher the voltage generated through the Y capacitors CyF+, CyF-, CyL+, CyL-. As a result, the assumed body resistance R KUnder this condition, a current that increases in proportion to the voltage of the Y capacitors CyF+, CyF-, CyL+, and CyL- also occurs at the start of the contact process. The current passing through the body decreases in particular in an exponential form as the capacitor discharges through the resistance. The current at the start of contact is calculated as the quotient of the voltage and the resistance. Assuming a maximum charging voltage of 920V, an initial contact current value of 460V / 1200 ohms = 383 mA is obtained under the high-voltage potential distribution that is also assumed to be symmetric with respect to the reference potential M (460V for each Y capacitor). Based on this initial value of the current, this current can be converted to an alternating current with a sinusoidal waveform by dividing by the square root of 6. This corresponds to the value on the X-axis in the so-called C1 characteristic curve of the standard SAE J 1772. The duration of this current can be obtained through the calculation of the time constant t = R × C of the capacitor discharge. The corresponding duration (Y-axis) at this time corresponds to 3 × t. For example, a duration of about 100 ms in this state is still allowed. As a goal, a residual body current lower than 5 mA is selected, that is, the residual voltage must be lower than 6V.

[0166] For example, under an asymmetric high-voltage potential distribution with respect to the reference potential M, the higher the voltage of the Y capacitors CyF+, CyF-, CyL+, and CyL-, the shorter the maximum duration becomes. A current exceeding 500 mA is not allowed. This is because in that case, a maximum voltage of 600V will be generated in the Y capacitors CyF+, CyF-, CyL+, and CyL-. If this is exceeded, the charging process must be aborted.

[0167] Therefore, it is possible to calculate whether the protection device 8 having the protection circuit 9 can comply with the required maximum current and duration. When this condition is not met, the charging process must be aborted immediately. This is because further errors will lead to danger to the person. The input quantities for this calculation are the voltage measurements of the Y capacitors CyF+, CyF-, CyL+, and CyL- of both high-voltage potentials HV+ and HV-, the knowledge regarding the reaction speed unique to the circuit, and the numerical table of the maximum allowable current and duration.

[0168] In the case of a plurality of contacts that proceed very rapidly in succession with the high voltage potentials HV+ and HV-, the protection circuit 9 can serve as an equivalent conduction path to the body current each time. Therefore, the protection device 8 described here, especially its protection circuit 9, can be autonomously connected, that is, the first and / or second protection switches SS1 and SS2 can be closed, and after a short duration in this connected state, the respective closed protection switches SS1 and SS2 can be opened again. In that case, there is an advantage that communication with the upper control device inside the vehicle 2 regarding how to implement measures such as opening the charging contactors LS+ and LS- and / or the main contactors HS+ and HS-, and discharging the Y capacitors CyF+, CyF-, CyL+, and CyL- is omitted. For example, there is no defective protective cover for the high voltage cable, and the recognition of constantly occurring insulation defects, that is, low insulation resistance, is preferably recognized by a separate instrument, for example, an insulation monitor, and / or by measuring the high voltage potential distribution. Such an instrument is not a component of the protection device 8 and its protection circuit 9 described here and has no relevance to it. As described above, the protection device 8 and its protection circuit 9 described here can be triggered even under repeated and rapid human contacts at very short intervals, thus ensuring human protection. For example, false triggering due to EMC interference does not lead to further measures in the vehicle 2 such as an incorrect stop of the high voltage system. The autonomous function of the protection device 8, especially its protection circuit 9, enables the realization of a flexible and simple integration into the existing high voltage system. Furthermore, due to the autonomous function, the safety requirements related to the protection device 8 and its protection circuit 9 are reduced, and for example, functions with fuses / communication with other control devices are not required.

[0169] The protection device 8 can also be applied in the case of the DC network 1 without the DC charging station 5, especially for the driving operation of the vehicle 2, for the AC charging operation, and for the assembly and maintenance work. The only difference from the case of DC charging is the absence of the DC charging station 5. As failure mechanisms, for example, defects in the high-voltage cable as a result of an accident, or defects in the housing of the high-voltage electronics, etc. are considered. Even when the high-voltage system is damaged during assembly or maintenance, the protection device 8 having the protection circuit 9 can reduce the charge amount.

[0170] The protection circuit 9 for reducing the Y shock caused by the insulation fault IF remains the same as that described above. For this purpose, the protection device 8 having the protection circuit 9 is of course arranged in the vehicle 2. The function is the same as that for the insulation defect during DC charging described above. When a voltage drop between one of the high-voltage potentials HV+, HV- and the reference potential M is recognized, the respective protection capacitors Cs, Cs1, Cs2 are additionally connected, and the total capacitance of the Y capacitors CyF+, CyF-, CyL+, CyL- of the corresponding high-voltage potential HV+, HV- is discharged. For example, it is possible to further instruct the opening of the main contactors HS+, HS- of the high-voltage battery 6 and to start the active discharge of the X capacitor Cx and both Y capacitors CyF+, CyF- of the vehicle 2. The charging contactors LS+, LS- have already been opened before and remain open.

[0171] Figure 6 shows the protection circuit 9 optimized for components. In the protection circuit 9 for reducing the Cy shock, it is assumed that only one of the high-voltage potentials HV+, HV- is connected to the reference potential M, for example, the frame ground, via the body resistance R K If both high-voltage potentials HV+, HV- are connected to the reference potential M, especially the frame ground, this is the same as a short circuit of the high-voltage battery 6 or the DC charging station 5, and such a short circuit must be separated by a fuse or a current sensor and a circuit breaker controlled thereby.

[0172] From this, it is clear that it is never possible to apply the protection circuit 9 for reducing the Cy shock simultaneously for the positive potential HV+ and the negative potential HV-. Therefore, as shown in FIG. 6, a single protection capacitor Cs, a discharge resistor Re, a protection resistor Rs, a rapid discharge resistor Rse, and a rapid discharge switch Se can be applied for the safety of both high voltage potentials HV+, HV-. That is, two protection circuits 9.1, 9.2 are not necessary. The voltage measurement by both voltage protection devices SV1, SV2 for connecting the protection circuit 9, and both protection switches SS1, SS2 must continue to exist. FIG. 6 shows such component optimization. This is significant, for example, when the discharge resistor Re also has to have a relatively high component value based on the high operating voltage at the vehicle 2 and the DC charging station 5 and the large capacitance of the Y capacitors CyF+, CyF-, CyL+, CyL-.

[0173] FIG. 6 shows an embodiment of the entire protection device 8 having such a component-optimized protection circuit 9, that is, not having both protection circuit parts 9.1, 9.2. Here, the protection device 8, especially its protection circuit 9, is reduced only by the necessary additional cost to be integrated into the vehicle 2 or the DC charging station 5. The connection parts AHV+, AHV-, AM to the positive potential HV+, the negative potential HV-, and the reference potential M can be made very small. This is because only a current in the order of milliseconds flows during a fault. Otherwise, the connection parts AHV+, AHV-, AM are currentless and only serve for voltage measurement. As a result, the rapid integration of the protection device 8 having the protection circuit 9 into the existing high voltage system is possible with few modifications. If there is sufficient planning time, of course, this function can also be integrated into the existing equipment.

[0174] That is, as shown in FIG. 6, the protection circuit 9 includes an electrical series circuit of an electrical protection capacitor Cs, an electrical protection resistor Rs, and a first protection switch SS1 between the positive potential line HV+L and the reference potential ML, and an electrical series circuit of an electrical protection capacitor Cs, an electrical protection resistor Rs, and a second protection switch SS2 between the negative potential line HV-L and the reference potential ML. An electrical discharge resistor Re is electrically connected in parallel to the protection capacitor Cs and the protection resistor Rs, and an electrical series circuit composed of an electrical rapid discharge resistor Rse and a rapid discharge switch Se is electrically connected in parallel to the protection capacitor Cs, or to the protection capacitor Cs and the protection resistor Rs.

[0175] In the method of operating the protection device 8, when a trigger reference is satisfied, the first protection switch SS1 or the second protection switch SS2 is closed, then opened again after the protection capacitor Cs is charged, then the rapid discharge switch Se is closed, and then opened again after the protection capacitor Cs is discharged.

[0176] In an alternative embodiment, the protection circuit 9 comprises, as shown in FIG. 5, two circuit parts 9.1, 9.2. The first protection circuit part 9.1 comprises an electrical series circuit of a first electrical protection capacitor Cs1, a first electrical protection resistor Rs1, and a first protection switch SS1 between the positive potential line HV+L and the reference potential ML. A first electrical discharge resistor Re1 is electrically connected in parallel to the first electrical protection capacitor Cs1 and the first electrical protection resistor Rs1. An electrical series circuit consisting of a first electrical rapid discharge resistor Rse1 and a first rapid discharge switch Se1 is electrically connected in parallel to the first electrical protection capacitor Cs1, or to the first protection capacitor Cs1 and the first electrical protection resistor Rs1. The second protection circuit part 9.2 comprises an electrical series circuit of a second electrical protection capacitor Cs2, a second electrical protection resistor Rs2, and a second protection switch SS2 between the negative potential line HV-L and the reference potential ML. A second electrical discharge resistor Re2 is electrically connected in parallel to the second electrical protection capacitor Cs2 and the second electrical protection resistor Rs2. An electrical series circuit consisting of a second electrical rapid discharge resistor Rse2 and a second rapid discharge switch Se2 is electrically connected in parallel to the second electrical protection capacitor Cs2, or to the second protection capacitor Cs2 and the second electrical protection resistor Rs2.

[0177] In that case, in the method of operating the protection device 8 accordingly, when the trigger criterion is met, the first protection switch SS1 is closed, opened again after the first protection capacitor Cs1 is charged, then the first rapid discharge switch Se1 is closed, opened again after the protection capacitor Cs1 is discharged, and / or when the trigger criterion is met, the second protection switch SS2 is closed, opened again after the second protection capacitor Cs2 is charged, then the second rapid discharge switch Se2 is closed, opened again after the protection capacitor Cs2 is discharged.

[0178] The following describes the preferred availability of the protection device 8. In the vehicle 2 having a high-voltage system at the 800V level, it is difficult to comply with the limit values required by the standard for the discharge by the Y capacitors CyF+, CyF-, CyL+, CyL-. This is particularly true for existing vehicles 2 where the design space of the vehicle 2 is already filled and it is not possible to adapt to a high-voltage system with large additional components. In that case, the above-described solution method, which can be easily installed in the vehicle 2 at low cost and with little required space, is suitable.

[0179] Furthermore, the regulations of the standard are particularly satisfied by the above-described solution method, whereby the approval of the vehicle 2 becomes easier or possible for the first time. With such a protection device 8 and its protection circuit 9, the limit values are achieved without adding electronics, and there is no need to make any modifications to the high-voltage system or its components.

[0180] The maximum energy content of 0.2J required by LV123 has already been exceeded by the DC charging station 5 at 632V. "Alternative measurement values", that is, alternative measures, are necessarily required. As the only solution, doubled insulation is currently being considered. In that case, all connected systems, that is, the vehicle 2 and the DC charging station 5, must have enhanced insulation at the same time, which cannot be ensured at present. However, the protection device 8 and its protection circuit 9 can suppress the energy flowing through the human body MK to a value below 0.2J as well. Therefore, it becomes yet another solution for "alternative measurement values".

[0181] The protection device 8 and its protection circuit 9 make it possible to reduce the dangerous discharge current of the Y capacitors CyF+, CyF-, CyL+, CyL- when a human touches them when the insulation is damaged during DC charging, for example, when the charging plug or the charging cable 4 is damaged. Even in any other vehicle state, when the insulation is also damaged, the dangerous discharge current when a human touches it is reduced.

[0182] Improved EMC interference suppression is made possible by a larger configuration of the Y capacitors CyF+, CyF-, CyL+, CyL-. It becomes possible to eliminate the requirement for doubled insulation of the entire high-voltage system. This applies to both the vehicle 2 and the DC charging station 5.

[0183] The protection device 8 having the protection circuit 9 can be arranged in the vehicle 2 and / or the DC charging station 5.

Explanation of symbols

[0184] 1 DC network 2 Vehicle 3 High-voltage in-vehicle electrical system 4 Charging cable 5 DC charging station 6 High-voltage battery 7 Battery energy source 8 Protection device 9 Protection circuit 9.1, 9.2 Protection circuit parts 12 Voltage evaluation unit 13 Charging station voltage source AHV+, AHV-, AM connection parts AK+, AK- connection contacts Cs, Cs1, Cs2 Protection capacitors Cx X capacitor CyF+, CyF- Y capacitors in vehicle CyL+, CyL- Y capacitors in DC charging station HS+, HS- Main contactors HV+, HV- High-voltage potentials HV+L, HV-L High-voltage potential lines IF Insulation fault LS+, LS- Charging contactors M Reference potential ML Reference potential line MK Human body R Batt Battery internal resistance R, R1, R2 Resistors Re, Re1, Re2 Discharge resistors R K Body resistance R LS Internal resistance of the charging station Rs, Rs1, Rs2 Protection resistors Rse, Rse1, Rse2 Rapid discharge resistors Se, Se1, Se2 Rapid discharge switches SS1, SS2 Protection switches SV1, SV2 Voltage measuring devices

Claims

1. A protection device (8) for an electrical DC network (1), 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), 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), and a protection circuit (9) for reducing an electric shock caused by a Y capacitor of the electrical DC network (1), the protection circuit (9) includes a first protection switch (SS1) between the positive potential line (HV+L) and the reference potential line (ML) and a second protection switch (SS2) between the negative potential line (HV−L) and the reference potential line (ML), a plurality of trigger criteria are set, in the protection device (8), the first protection switch (SS1) and / or the second protection switch (SS2) are operable to close only when all the set trigger criteria determined by the first voltage measuring device (SV1) and / or the second voltage measuring device (SV2) are met, the trigger criteria are the voltage difference of the currently occurring voltage between the positive potential line (HV+L) and the reference potential line (ML) and the voltage between the negative potential line (HV−L) and the reference potential line (ML) with respect to the previously determined voltage value in terms of time, the voltage change of the voltage occurring between the positive potential line (HV+L) and the reference potential line (ML) and the voltage occurring between the negative potential line (HV−L) and the reference potential line (ML), the opposite signs of the voltage occurring between the positive potential line (HV+L) and the reference potential line (ML) and the voltage occurring between the negative potential line (HV−L) and the reference potential line (ML), the non-existence of a periodic repetition of other trigger criteria, and include, The first protection switch (SS1) and / or the second protection switch (SS2) are such that the voltage difference with respect to the voltage value determined previously in time of the voltage currently occurring between the positive potential line (HV+L) and the reference potential line (ML), and of the voltage occurring between the negative potential line (HV−L) and the reference potential line (ML), exceeds a set limit value, and the voltage change of the voltage occurring between the positive potential line (HV+L) and the reference potential line (ML), and of the voltage occurring between the negative potential line (HV−L) and the reference potential line (ML), exceeds a set limit value, and the reverse signs of the voltage occurring between the positive potential line (HV+L) and the reference potential line (ML), and of the voltage occurring between the negative potential line (HV−L) and the reference potential line (ML), exist, and the non-existence of a periodic repetition of the other trigger criteria is also determined, and is operable only when that is the case, the protection device (8). **Claim 2** The protection device (8) according to claim 1, characterized in that an analog and / or digital evaluation of the voltage determined by the first voltage measuring device (SV1) and / or by the second voltage measuring device (SV2) is provided. **Claim 3** A common voltage evaluation unit (12) connected to both the voltage measuring devices (SV1, SV2) and both the protection switches (SS1, SS2) is provided 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 actuating the first protection switch (SS1) and / or the second protection switch (SS2) only when all the set trigger criteria determined by the first voltage measuring device (SV1) and / or by the second voltage measuring device (SV2) are met. The protection device (8) according to claim 1 or 2, characterized in that. **Claim 4** The protection device (8) according to claim 1 or 2, characterized in that each of the protection switches (SS1, SS2) is configured as a semiconductor switch.

5. An in-vehicle electrical system (3) for a vehicle (2), in particular a high-voltage in-vehicle electrical system (3), comprising the protection device (8) according to claim 1 or 2.

6. A vehicle (2) comprising the in-vehicle electrical system (3) according to claim 5, in particular an electric vehicle or a hybrid vehicle.

7. A DC charging station (5), in particular a high-voltage DC charging station, comprising the protection device (8) according to claim 1 or 2.

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