DE102023001341A1 - Protection device for a direct current electrical network, vehicle electrical system, vehicle and direct current charging station - Google Patents

Abstract

The invention relates to a protective device (8) for a DC network (1), comprising a respective voltage measuring device (SV1, SV2) between a respective potential line (HV+L, HV-L) and a reference potential line (ML) and a protective circuit (9). a circuit breaker (SS1, SS2) between the respective potential line (HV+L, HV-L) and the reference potential line (ML) and at least one resistor (R, R1, R2), which acts as a resistor with a fixed resistance value of maximum 800 Ω or is designed as a voltage-dependent resistor, wherein the respective circuit breaker (SS1, SS2) can be controlled to close when at least one triggering criterion is determined by the respective voltage measuring device (SV1, SV2).

Description

The invention relates to a protective device for an electrical DC network according to the features of the preamble of claim 1, an on-board network for a vehicle, a vehicle and a DC charging station.

From the prior art, as in the DE 10 2017 009 355 A1 described, a method for operating electrical systems known. In the method for operating a first vehicle electrical system to which a first electrical DC voltage is applied and a second vehicle electrical system to which a second electrical DC voltage is applied, the first and second vehicle electrical systems are electrically coupled by means of an energy coupler having a first clocked energy converter. The first and the second electrical DC voltage are electrically insulated from an electrical reference potential by means of an electrical insulation device. The electrical isolation device is monitored. The first and the second vehicle electrical system are galvanically coupled by means of the energy coupler. If there is a fault in the isolation device in one area of one of the two vehicle electrical systems, the energy coupler controls electrical potentials of the respective other of the two vehicle electrical systems in such a way that the respective potential differences between these electrical potentials and the reference potential are smaller than a predetermined comparison value.

In the DE 10 2019 008 833 a protective device for an electrical DC network, in particular for a high-voltage network, an on-board network for a vehicle, a vehicle and a DC charging station is described. The protective device comprises either a first voltage measuring device between a plus potential line and a reference potential line for measuring a voltage between the plus potential line and the reference potential line and a second voltage measuring device between a minus potential line and the reference potential line for measuring a voltage between the minus potential line and the reference potential line, or a residual current measuring device in the reference potential line . The protective device also includes a protective circuit, either with an electrical series circuit of a discharge resistor and a first protective switch between the positive potential line and the reference potential line and an electrical series circuit of the discharge resistor and a second protective switch between the negative potential line and the reference potential line, or with two protective circuit parts, the first Protective circuit part comprises an electrical series circuit of a first discharge resistor and a first protective switch between the positive potential line and the reference potential line and the second protective circuit part comprises an electrical series circuit of a second discharge resistor and a second protective switch between the negative potential line and the reference potential line. The first circuit breaker can be controlled to close when the voltage falls below a specified value determined by the first and/or second voltage measuring device, and the second circuit breaker can be controlled to close when the voltage falls below the specified value determined by the second and/or first voltage measuring device. Alternatively, the first circuit breaker and/or the second circuit breaker can be controlled to close when a fault current is measured using the fault current measuring device.

The invention is based on the object of specifying a protective device for an electrical direct current network that is improved compared to the prior art, an on-board network for a vehicle that is improved compared to the prior art, a vehicle with such an on-board network and a direct current charging station that is improved compared to the prior art.

The object is achieved according to the invention by a protective device for an electrical DC network having the features of claim 1, an on-board network for a vehicle having the features of claim 8, a vehicle having the features of claim 9 and a DC charging station having the features of claim 10.

Advantageous configurations of the invention are the subject matter of the dependent claims.

A protective device according to the invention for an electrical DC network, in particular for a high-voltage network, includes a first voltage measuring device between a positive potential line and a reference potential line for measuring a 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 a voltage between the negative potential line and the reference potential line. The reference potential is in particular an electrical ground potential, in particular a vehicle ground potential when using the protective device in a vehicle, for example a ground potential when using the protective device in a DC charging station.

The protective device also includes a protective circuit with a first protective switch between the positive potential line and the reference potential line, a second protective switch between the negative potential line and the reference potential line and at least one electrical resistor.

The at least one electrical resistor is designed as an electrical resistor with a fixed resistance value of at most 800 Ω, in particular at most 600 Ω, in particular smaller, in particular significantly smaller, than a human body resistance, i. H. as a body resistance of a person, in particular a maximum of 200 Ω, in particular a maximum of or less than 50 Ω, for example less than 5 Ω.

Alternatively, the at least one electrical resistor is in the form of a voltage-dependent electrical resistor. The at least one electrical resistor designed as a voltage-dependent electrical resistor is designed in particular such that a resistance value of the voltage-dependent electrical resistor is reduced, in particular progressively reduced, with an increasing electrical voltage across terminals of the voltage-dependent electrical resistor. In particular, a maximum resistance value of the at least one electrical resistor designed as a voltage-dependent electrical resistor is a maximum of 800 Ω, in particular a maximum of 600 Ω, in particular smaller, in particular significantly smaller, than a human body resistance, i. H. as a body resistance of a person, in particular a maximum of 200 Ω, in particular a maximum of or less than 50 Ω, for example less than 5 Ω. This therefore applies to all resistance values that the voltage-dependent electrical resistance can have given the electrical voltages that occur across its connections. The voltage-dependent electrical resistor is thus designed in such a way that its resistance value decreases as the voltage across its connections increases. In addition, these resistance values amount to a maximum of 800 Ω, in particular a maximum of 600 Ω, and are in particular smaller, in particular significantly smaller, than the human body resistance, i. H. than the body resistance of a person, amount in particular to a maximum of 200 Ω, are in particular a maximum of or less than 50 Ω, for example less than 5 Ω. This significantly reduces the flow through the human body. The voltage-dependent electrical resistance is designed, for example, as a varistor or as a series connection and/or parallel connection of a plurality of varistors, for example with and/or without additional circuitry. The additional circuit is in particular a series resistor to limit the varistor current

The first circuit breaker and/or the second circuit breaker are/is upon the occurrence of at least one predetermined triggering criterion or multiple predetermined triggering criteria determined by means of the first voltage measuring device and/or by means of the second voltage measuring device, for example in the case of one by means of the first voltage measuring device and/or by means of the second voltage measuring device determined voltage change on an e-function with a time constant in a predetermined frequency band range and/or when the voltage falls below a predetermined voltage value determined by means of the first voltage measuring device and/or by means of the second voltage measuring device, for closing. This evaluation, i. H. the determination of the occurrence of the at least one triggering criterion or the multiple triggering criteria by means of the first voltage measuring device and/or by means of the second voltage measuring device takes place, for example, digitally or analogously.

The protective device thus has an evaluation of voltage levels between positive potential and reference potential and between negative potential and reference potential. The circuit breakers are each controlled via this if the at least one predetermined triggering criterion is given or the plurality of predetermined triggering criteria are given.

As an alternative to the two voltage measuring devices, a residual current measuring device can be provided in the reference potential line. Then, in both variants of the protective circuit, the first circuit breaker and/or the second circuit breaker can be controlled to close when a fault current is measured by means of the fault current measuring device.

An electrical vehicle electrical system according to the invention, in particular a high-voltage vehicle electrical system, for a vehicle, in particular for an electric vehicle or hybrid vehicle, includes the protective device described above.

A vehicle according to the invention, in particular an electric vehicle or hybrid vehicle, includes the protective device described above, in particular such an on-board electrical system, in particular a high-voltage on-board electrical system, with such a protective device.

An inventive, in particular vehicle-external, direct current charging station, in particular high-voltage direct current charging station, in particular for electrically charging a vehicle, in particular an electric vehicle or hybrid vehicle, in particular a high-voltage battery of such a vehicle, comprises the protective device described above.

The term "high voltage" is to be understood in particular as an electrical direct voltage which is in particular greater than approximately 60 V. In particular, the term “high voltage” must be interpreted in accordance with the ECE R 100 standard.

The solution according to the invention solves the problems associated with Y-capacitors in vehicles, in particular in electric vehicles and hybrid vehicles, and in DC charging stations, as will be explained below. Such Y-capacitors are used as measures to reduce the emission of EMC interference (EMC = electromagnetic compatibility). However, they represent an increased risk potential for high-voltage safety reasons. In various standards, the amount of charge contained or the energy stored in the Y-capacitors is named as a feature that is hazardous to health. For example, in the SAE J1772, IEC60479-1 and -2 standard, the amount of charge contained in the Y-capacitors is named as a feature that is hazardous to health (C1 characteristic). As the operating voltage of the vehicle increases, it becomes more and more difficult to comply with the limit values required by these standards. In some cases, alternative measures, so-called alternative measures, for complying with safety specifications, for example reinforced, in particular double, electrical insulation, are also not permitted. The additional standard LV123 and associated standards stipulate, for example, a maximum energy content of 0.2 J for the amount of charge on all Y-capacitors. If the way out via the alternative measures is allowed, then, for example, the already mentioned reinforced, in particular double, electrical insulation can be used. However, this can only be implemented if all high-voltage systems that are coupled with each other are appropriately insulated. i.e. that, for example, when charging with direct current, both the vehicle and the direct current charging station, in particular the charging station, must be insulated accordingly. However, since there is no mandatory standard for this, it would also be possible to connect systems with different insulation designs, which means that the safety requirements are not met.

This problem is solved by the invention described, because a voltage measurement for each high-voltage potential relative to the reference potential, in particular ground potential, detects a shift in the high-voltage potentials relative to the reference potential, which can be the result of a body current, i. H. the result of physical contact, particularly human contact, with one of the high-voltage potentials and with the reference potential. In order to reduce the voltage as quickly as possible at the affected high-voltage potential, at which the voltage is reduced to the reference potential, the resistor is switched on. The voltage between the affected high-voltage potential and the reference potential suddenly jumps to a much lower level, which reduces the body current in proportion to the voltage. The solution according to the invention thus makes it possible to reduce an electric shock to the body, in particular the human body, caused by the Y capacitors. Compliance with the requirements described above is thus made possible. It is also possible to limit the electrical energy dissipated by body resistance of the Y-capacitors to a level below 0.2 J, although the energy stored in the Y-capacitors can be much higher.

In one possible embodiment, the protective circuit comprises an electrical series circuit of the electrical resistor and the first protective switch between the plus potential line and the reference potential line and an electrical series circuit of the electrical resistor, i. H. the same electrical resistance, and the second protective switch between the negative potential line and the reference potential line.

This embodiment of the protection circuit is a component-optimized protection circuit. In the protective circuit, which serves to reduce a CY shock, ie an electric shock to a person through Y capacitors, it can be assumed that only one potential, ie a plus potential or a minus potential, is connected to a housing ground via a body resistance of the person. If both potentials were connected to the chassis ground, this would equate to a short-circuit in a vehicle battery when using the protective device in the vehicle, or a short-circuit in a DC charging station, for example a charging station, when using the protective device in the DC charging station, which is caused by a fuse or a current sensor must be disconnected with the shut-off device controlled thereby. This makes it clear that the protective circuit for the plus potential and the negative potential is never used at the same time. The electrical resistance can thus be used in the manner described to protect both potentials.

In this embodiment of the protection circuit, which comprises only the one electrical resistance, i. H. uses the same electrical resistance for the electrical series connection with the first protective switch between the positive potential line and the reference potential line and with the second protective switch between the negative potential line and the reference potential line, it is provided in particular that when using the first voltage measuring device and/or using the second voltage measuring device determined occurrence of the at least one predetermined triggering criterion or the several predetermined triggering criteria or in the case of the residual current measured by means of the residual current measuring device, not both circuit breakers, in particular not simultaneously, can be controlled or are controlled to close, but only one of the two circuit breakers, in particular depending on this , on which or in the area of which potential line (plus potential line or minus potential line), the occurrence of the at least one predetermined triggering criterion or the plurality of predetermined triggering criteria was determined.

Alternatively, the protective circuit comprises two protective circuit parts, the first protective circuit part comprising an electrical series connection of a first electrical resistor and the first protective switch between the plus potential line and the reference potential line and the second protective circuit part comprising an electrical series circuit of a second electrical resistor and the second protective switch between the negative potential line and the reference potential line includes.

The advantage of the solution described, i. H. the protective circuit of the protective device with the electrical series circuit of the resistor or the first and second resistor with the respective protective switch between the respective potential line and the reference potential line, compared to a parallel circuit of a capacitor connected in series with a protective resistor and electrically connected in series with the respective protective switch and one Discharge resistor is that the protective circuit of the solution described does not require such a discharge resistor. As a result, when lower voltages are reached between plus potential and reference potential or between minus potential and reference potential, a state with higher insulation resistances is automatically returned to, although the first and/or the second protective switch are still closed. In the protective circuit with the parallel connection, electrically connected in series with the respective protective switch, of the capacitor connected in series with the protective resistor and the discharge resistor, the protective resistor would, with a closed first or second protective switch, reduce the entire insulation value of a high-voltage system, in particular the DC network, for example the vehicle electrical system of the vehicle, to a smaller value. This is avoided by the solution described.

The protective circuit of the solution described can also be activated if a high-voltage potential is touched very quickly one after the other, i. H. the plus potential or the minus potential, always represent an equivalent discharge path to the body current. In contrast, in the protective circuit with the parallel circuit of the capacitor connected in series with the protective resistor and the discharge resistor, electrically connected in series with the respective circuit breaker, either one has to wait until the protective capacitor has been discharged to a very low voltage value via the discharge resistor, or this protective circuit has to be discharged With body contacts in rapid succession to a high-voltage potential, this represents a decreasing protective effect, because the protective capacitor still has a residual voltage and can no longer store as much energy.

It is therefore advantageously provided that the protective device described here, in particular its protective circuit, is designed in such a way that it is able to switch on autonomously, ie to close the first and/or second protective switch and switch it on after a short dwell time in it State to open the respective closed circuit breaker again. Communication within the vehicle to a higher-level control unit, which carries out measures such as opening contactors, in particular charging contactors and/or main contactors, and discharging the Y capacitors, is advantageously dispensed with here. The detection of a permanent insulation fault, i.e. a low insulation resistance and not, for example, a defective protective sheath of a high-voltage cable, is advantageously detected by another device, for example by an insulation monitor, also referred to as an insulation monitor, and/or by measuring a high-voltage potential distribution, which is not part of the protective device described here and its protective circuit and is also not connected to it. As mentioned, the protection device described here and its protection circuitry is capable of repeatedly and at very short intervals thus also in the case of rapid recurring touches by a person, and thus ensure protection for the person. Accidental triggering, for example due to an EMC fault, does not lead to further measures in the vehicle, such as the high-voltage system being switched off incorrectly. Due to the self-sufficient function of the protective device, in particular its protective circuit, flexible and simple integration into an existing high-voltage system can be implemented. The autonomous function also reduces the safety requirements for the protective device and its protective circuit, for example there is no secure function/communication with another control unit.

In contrast to the protective circuit with the parallel connection of the capacitor connected in series with the protective resistor and the discharge resistor electrically connected in series with the respective circuit breaker, the solution described here does not lead to an increase in the total capacitance between plus potential and reference potential and between minus potential and reference potential.

A comparison of the solution described here with the protective circuit with the parallel circuit of the capacitor connected in series with the protective resistor and the discharge resistor, electrically connected in series with the respective circuit breaker, shows that at the moment the protective circuit is switched on, the uncharged capacitor has a lower impedance has, whereby a faster reduction of the body current can be achieved. The transferred charge and the energy converted in the human body are therefore somewhat lower at first. Over time, however, the capacitor is charged and its impedance thus increases. However, the electrical resistance of the solution described here, which is designed as a voltage-dependent resistor in the form of a varistor, remains almost constant until its varistor voltage of, for example, 80 V is reached and can therefore reduce the body current more quickly as it progresses.

As already mentioned, the electrical resistor and/or the first electrical resistor and/or the second electrical resistor is designed, for example, as an electrical resistor with a fixed resistance value of a maximum of 800 Ω, in particular a maximum of 600 Ω, in particular smaller, in particular significantly smaller than a human body resistance, d. H. as a body resistance of a person, in particular a maximum of 200 Ω, in particular a maximum of or less than 50 Ω, for example less than 5 Ω, or as a voltage-dependent electrical resistance with a maximum resistance value of a maximum of 800 Ω, in particular a maximum of 600 Ω, in particular less, in particular significantly smaller than a human body resistance, i. H. as a body resistance of a person, in particular a maximum of 200 Ω, in particular a maximum of or less than 50 Ω, for example less than 5 Ω. I.e. in the above-specified embodiment with one electrical resistor, this electrical resistor is designed as an electrical resistor with this fixed resistance value or as a voltage-dependent electrical resistor with this maximum resistance value, and in the above-specified alternative embodiment with the two protective circuit parts and the first and second electrical resistor, the first electrical resistor and/or the second electrical resistor is designed as an electrical resistor with this fixed resistance value or as a voltage-dependent electrical resistor with this maximum resistance value.

As already mentioned, the voltage-dependent electrical resistance and thus in the above embodiment with one electrical resistor is this one electrical resistor and in the above stated alternative embodiment with the two protective circuit parts and the first and second electrical resistor is the first electrical resistor and/or the second electrical resistor is designed as a varistor or as a series connection and/or parallel connection of a plurality of varistors, for example with and/or without additional circuitry. The additional circuit is in particular a series resistor to limit the varistor current.

In one possible embodiment, the protective circuit includes at least one electrical protective resistor. In particular, the at least one electrical resistor is electrically connected in series with the at least one electrical protective resistor. In the embodiment with the two protective circuit parts, each protective circuit part advantageously includes such an electrical protective resistor. In this case, in particular, the electrical resistance of the respective protective circuit part is electrically connected in series with the electrical protective resistor of the respective protective circuit part. That is to say, in the above embodiment with one electrical resistor, this electrical resistor is electrically connected in series with an electrical protective resistor. The electrical series connection of the electrical resistance and electrical protective 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 above alternative embodiment with the two protective circuit parts and the first and second electrical resistor, the first electrical resistor is electrically connected in series with an electrical protective resistor and/or the second electrical resistor is electrically connected in series with an electrical protective resistor. The electrical series connection of the respective electrical resistor and the respective electrical protective resistor forms a discharge network between the positive potential and the reference potential or a discharge network between the negative potential and the reference potential. The electrical protective resistor or the respective electrical protective resistor serves to prevent the respective circuit breaker from being destroyed by an excessively high current. The electrical protective resistor or the respective electrical protective resistor can be omitted, for example, if it is always ensured by the electrical resistor or the respective electrical resistor, in particular in its design as a voltage-dependent electrical resistor, that a maximum current flow is limited in such a way that it does not lead to destruction of the respective circuit breaker.

In one possible embodiment, a common voltage evaluation unit coupled to the voltage measuring devices and the circuit breakers is for evaluating the voltage determined by the first voltage measuring device and the voltage determined by the second voltage measuring device and for controlling the first protective switch and/or the second protective switch in the case of the first voltage measuring device and/or the occurrence of the at least one triggering criterion or the plurality of triggering criteria determined by means of the second voltage measuring device.

When using the fault current measuring device, a current evaluation unit coupled to the fault current measuring device and the circuit breakers is provided for evaluating the measured fault current and for controlling the first circuit breaker and/or the second circuit breaker depending on the measured fault current.

In one possible embodiment it can be provided that the common voltage evaluation unit is coupled to a third voltage measuring device and a fourth voltage measuring device, the third voltage measuring device being arranged between the plus potential line and the reference potential line for measuring a voltage between the plus potential line and the reference potential line and the fourth voltage measuring device between the negative potential line and the reference potential line for measuring a voltage between the negative potential line and the reference potential line, and wherein a first switching unit is arranged in the positive potential line between a connection point to the first voltage measuring device and a connection point to the third voltage measuring device and in the negative potential line between a connection point to the second voltage measuring device and a second switching unit is arranged at a connection point to the fourth voltage measuring device. This embodiment is particularly suitable for the high-voltage vehicle electrical system of an electric vehicle or hybrid vehicle, with the first and second switching units being charging contactors of the high-voltage vehicle electrical system, which are closed for direct current charging after connection to a direct current charging station. With this solution is already before closing the switching units, d. H. the charging contactor, and the associated increase in the capacity of the Y capacitors due to the parallel connection of the DC charging station and the vehicle, it can be determined whether the protective circuit would be able to comply with legal limit values in the event of faulty insulation, for example in a charging cable.

The respective protective switch is designed, for example, as a semiconductor switch, for example as a MOSFET, IGBT or thyristor.

As the human body resistance mentioned above, i. H. A resistance value of 500 Ω is assumed or specified as the body resistance of a person, in particular according to the information in the standards to be observed. i.e. the human body resistance is accordingly defined as a resistance value of 500 Ω.

In one possible embodiment, several triggering criteria are specified, with the first circuit breaker and/or the second circuit breaker being/is only controllable to close when all specified triggering criteria are met and determined by means of the first voltage measuring device and/or by means of the second voltage measuring device. The tripping criteria relate in particular to the causes of faults/malfunctions that can occur and should be prevented from closing the circuit breakers when they occur. Advantageously, at least one triggering criterion is specified for each of these causes of error/faults in such a way that physical contact, ie contact by a person, ie a human being body, with one of the high-voltage potentials, and does not occur when the respective cause of the fault occurs. The triggering, ie the closing of the respective circuit breaker, only occurs when all the specified triggering criteria occur, ie are met. This ensures that the respective circuit breaker is only closed in the event of body contact, ie contact of a person, ie a human body, with one of the high-voltage potentials and incorrect closing due to the occurrence of one or more of the causes of error/faults is reliably avoided.

The solution described advantageously means that the protective circuit both triggers very quickly in order to keep the charge and energy converted in the body resistance low, and faulty triggering occurs as little as possible or is advantageously avoided. False tripping would result in an insulation fault for a very short period of time. In addition, the protective circuit ensures a massive shift in the high-voltage potentials, which represents a maximum deviation from the energetic minimum of the energy stored in the Y-capacitors. In addition, the function of an insulation monitor can be impaired in the event of repeated false triggering of the protective circuit. For example, sources of interference in the vehicle and/or in the DC charging station can cause the protective circuit to trip incorrectly. This is avoided or at least significantly reduced by the solution described.

As a result of the solution described, the evaluation of the protective circuit becomes more stable against false triggering, in that several triggering criteria have to occur simultaneously. The individual triggering criteria are evaluated in particular with an AND link. The individual triggering criteria depend on the type of fault. The form of the disturbance is compared with the characteristic of a discharge of the Y-capacitors through a body resistance. In order to distinguish any disturbance from such a CY body resistance discharge, at least one feature is advantageously found, which can be detected by a measurement or evaluation. At least this one characteristic per disorder must differ from the characteristic of the CY body current discharge.

For example, these are the distinction between common mode and differential mode events, minimum charge reversal voltages, time constants of a capacitor charge reversal (time constant of the e-function), frequencies/frequency spectra or repetition rates of a clocking disturbance, etc. The voltage measurement is used as the measurement input variable used by means of the voltage measuring devices, d. H. between plus potential line and reference potential line and between minus potential line and reference potential line.

By linking the triggering of the protection circuit to various characteristic features of a CY body discharge, the number of false triggerings can be minimized or completely avoided. At the same time, a very fast triggering time is achieved and thus the energy/charge converted in the human body is minimized.

• - Ermittlung von Abweichungen aktuell anliegenden Spannungen dU von Pluspotentialleitung zu Bezugspotentialleitung und von Minuspotentialleitung zu Bezugspotentialleitung bezogen auf einen zeitlich zuvor ermittelten Spannungswert, und/oder
• - Ermittlung von Spannungsänderungen dU/dt, d. h. über die Zeit, der Spannungen von Pluspotentialleitung zu Bezugspotentialleitung und von Minuspotentialleitung zu Bezugspotentialleitung, und/oder
• - Beachtung des entgegengesetzten Vorzeichens, insbesondere bei den obigen beiden Ermittlungen, bezüglich der Auswertung der Spannungen von Pluspotentialleitung zu Bezugspotentialleitung und von Minuspotentialleitung zu Bezugspotentialleitung, und/oder
• - Beachten einer zyklischen Wiederholung einer auftretenden Störung.

The voltages measured using the voltage measuring devices are evaluated in particular as follows:

• - Determination of deviations of currently applied voltages dU from positive potential line to reference potential line and from negative potential line to reference potential line based on a previously determined voltage value, and/or
• - Determination of voltage changes dU/dt, ie over time, the voltages from plus potential line to reference potential line and from minus potential line to reference potential line, and/or
• - Observation of the opposite sign, in particular in the above two determinations, with regard to the evaluation of the voltages from plus potential line to reference potential line and from minus potential line to reference potential line, and/or
• - Observe a cyclic repetition of an occurring fault.

• - die Spannungsabweichung der aktuell zwischen der Pluspotentialleitung und der Bezugspotentialleitung anliegenden Spannung und der zwischen der Minuspotentialleitung und der Bezugspotentialleitung anliegenden Spannung vom zeitlich zuvor ermittelten Spannungswert, und/oder
• - die Spannungsänderungen über die Zeit der zwischen der Pluspotentialleitung und der Bezugspotentialleitung anliegenden Spannung und der zwischen der Minuspotentialleitung und der Bezugspotentialleitung anliegenden Spannung, und/oder
• - das entgegengesetzte Vorzeichen der zwischen der Pluspotentialleitung und der Bezugspotentialleitung anliegenden Spannung und der zwischen der Minuspotentialleitung und der Bezugspotentialleitung anliegenden Spannung, und/oder
• - ein Nichtvorliegen einer zyklischen Wiederholung der anderen Auslösekriterien.

The trigger criteria therefore include in particular:

• - the voltage deviation of the voltage currently present between the plus potential line and the reference potential line and the voltage present between the minus potential line and the reference potential line from the voltage value previously determined, and/or
• - the voltage changes over time of the voltage present between the plus potential line and the reference potential line and the voltage present between the minus potential line and the reference potential line, and/or
• - the opposite sign of the voltage present between the plus potential line and the reference potential line and the voltage present between the minus potential line and the reference potential line, and/or
• - a non-existence of a cyclic repetition of the other triggering criteria.

• - die Spannungsabweichung der aktuell zwischen der Pluspotentialleitung und der Bezugspotentialleitung anliegenden Spannung und der zwischen der Minuspotentialleitung und der Bezugspotentialleitung anliegenden Spannung von dem zeitlich zuvor ermittelten Spannungswert einen vorgegebenen Grenzwert überschreitet, in einem möglichen Ausführungsbeispiel einen Grenzwert von 30 V, und
• - die Spannungsänderungen über die Zeit der zwischen der Pluspotentialleitung und der Bezugspotentialleitung anliegenden Spannung und der zwischen der Minuspotentialleitung und der Bezugspotentialleitung anliegenden Spannung einen vorgegebenen Grenzwert überschreitet, und
• - das entgegengesetzte Vorzeichen der zwischen der Pluspotentialleitung und der Bezugspotentialleitung anliegenden Spannung und der zwischen der Minuspotentialleitung und der Bezugspotentialleitung anliegenden Spannung vorliegt.

The first circuit breaker and/or the second circuit breaker are/is only controllable in particular when

• - the voltage deviation of the voltage currently present between the plus potential line and the reference potential line and the voltage present between the minus potential line and the reference potential line from the previously determined voltage value exceeds a predetermined limit value, in one possible exemplary embodiment a limit value of 30 V, and
• - the voltage changes over time of the voltage present between the plus potential line and the reference potential line and the voltage present between the minus potential line and the reference potential line exceed a predetermined limit value, and
• - the opposite sign of the voltage present between the plus potential line and the reference potential line and the voltage present between the minus potential line and the reference potential line.

The limit values depend in particular on the time constant to be considered t=R*C. Here R is the human body resistance, which according to standard specifications is assumed to be the lowest value up to 5000hm. For example, body resistances in the range from 3000hm to 30kOhm are taken into account. C depends on the in the high-voltage system, i. H. in the high-voltage direct current network, located total capacity of the Y-capacitors. This depends, for example, on the vehicle situation, for example whether only the vehicle is considered, for example while driving, or the vehicle in connection with a DC charging station. For example, a range of 200nF (in particular only vehicle, in particular optimized for low capacitances of the y-capacitors) up to a value for megawatt charging, i. H. DC charging with high power, from approx. 8µF (DC charging station and vehicle). All capacitance values refer to high-voltage potential, i. H. twice the value is to be assumed as the total capacity. In particular, the protection circuit has the requirement to be active at voltages above 60 V. For example, frequencies of the insulation monitor that are too low (approx. 800kOhm test resistor, cycle time approx. 10s) are seen as a delimitation, and an inverter with a cycle frequency of at least 2kHz is considered for frequencies above the tripping time constant.

In one possible embodiment, the first circuit breaker and/or the second circuit breaker can only be activated if the non-existence of a cyclical repetition of the other triggering criteria has also been determined.

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

For example, in analog evaluation, two evaluations are connected via operational amplifier circuits to one output of the voltage measurement (e.g. high-impedance resistor divider) for each high-voltage potential. The operational amplifier circuits have two different time constants. With the operational amplifier circuit of the first time constant (low frequency, below a time constant of a discharge via a human body resistance), the voltage deviation from the previously determined voltage value is determined. With the operational amplifier circuit of the second time constant (higher frequency, above the time constant of the discharge through a human body resistance), the voltage change over time is determined. These two triggering criteria are connected in a logical AND operation and at the same time a log. AND operation performed with the negated result of the evaluation of the respective other high-voltage potential, thereby determining whether the two voltages have opposite signs. If the overall result is "true", the protective circuit is activated.

With digital evaluation, the measured voltages are fed, for example, by a microcontroller, ASIC (application-specific integrated circuit) or FPGA (Field Programmable Gate Array, ie an integrated circuit of digital technology, in which a logic circuit can be loaded). The software-based filtering and determination of the voltage deviation from the previously determined voltage value and the voltage change over time for each high-voltage potential and then the AND operations already described for the analog evaluation are carried out. If the overall result is "true", the protective circuit is activated.

For example, the analogue and digital evaluation are implemented simultaneously, in particular as redundancy.

The solution described ensures that contact with a high-voltage potential by a human body is detected as quickly as possible and the protective circuit is switched on. The fast connection is due to the relatively fast discharging/recharging process of the Y-capacitors when the human body touches a high-voltage potential (approx. 10 ms). Most of the energy converted in the body or the charge flowing through the body occurs at the beginning of the discharging/recharging process. It weakens on an e function. This also makes it necessary to trip the protective circuit as quickly as possible.

However, it is also necessary for false tripping due to other influencing factors to be ruled out or at least to occur only rarely. An erroneously triggered protective circuit leads to an energetically very unfavorable potential distribution from the respective high-voltage potential to the reference potential, whereby the amount of energy stored in the Y-capacitors comes close to its maximum value, for example plus potential to reference potential about 0 V and reference potential to minus potential about close to one System voltage of the high-voltage system, for example 800V. In addition, an insulation fault is generated when the protective circuit is triggered by mistake at the moment when the protective circuit is activated. When switching on by means of a capacitance of the protective circuit, an additional capacitance is also connected in parallel with the Y capacitors, which basically offers the possibility of storing more energy in the now increased total Y capacitance.

Since the protective circuit must detect the discharge caused by human body resistance as quickly as possible, it is necessary to design it to react quickly. Thus, it also becomes sensitive to other disturbing influences. The solution described avoids or at least significantly reduces false triggering, which could be caused by this higher sensitivity. Means for distinguishing between interference and contact with a human body resistance offer, as already described above, for example the comparison of the signs of the two measured voltages, whereby a distinction between common-mode interference and differential-mode interference is made possible, filters for distinguishing interference frequencies, an averaging or voltage change compared to an average over a defined period of time, in particular to distinguish small energetic influences, a maximum voltage swing of the recharging processes, and/or sampling processes according to predetermined repetition rates, for example to detect regularly pulsating interference sources, such as inverters.

• Eine Gleichtaktstörung, auch als Common-Mode-Störungen bezeichnet, einer taktenden Hochvoltkomponente würde ebenso wie bei einer Körperentladung einen gemeinsamen Strombeitrag über das Bezugspotential zur Folge haben. Der Frequenzbereich kann weit gestreut sein durch die Vielzahl von taktenden Hochvoltkomponenten im Fahrzeug, deren unterschiedlicher Taktfrequenzen und eventuell sogar variabler Taktfrequenzen, beispielsweise bei einem Bordlader mit einem isolierenden LLC-DC/DC-Wandler.

If you look at the recharging process of the Y-capacitors when touched by a human body, this corresponds to common-mode interference or the triggering of common-mode currents. This is advantageously distinguished from the following influences:

• A common-mode interference, also referred to as common-mode interference, of a clocking high-voltage component would result in a common current contribution via the reference potential, just like in the case of a body discharge. The frequency range can be widely spread due to the large number of clocking high-voltage components in the vehicle, their different clock frequencies and possibly even variable clock frequencies, for example in the case of an on-board charger with an isolating LLC DC/DC converter.

In addition to the common-mode interference described above, clocking high-voltage consumers also cause differential-mode interference. These can also influence the evaluation circuit with their interference level. An insulation monitor also causes an identical charge reversal behavior as with a body discharge of the Y-capacitors. In the case of the two known insulation monitor principles, the insulation monitor using the charge-reversal resistor is particularly critical.

The following table compares the CY body discharge with the perturbations described above in terms of frequency spectrum, voltage swing, type of disturbance (CM or DM) and repetition rate. Type of error/interferer Frequency range (interference) spectrum voltage swing EVM failure (Common Mode (CM) or Differential Mode (DM)) refresh rate CY body discharge T=CY*R_body, about 2kHz Full reload CM One-off or slowly recurring Clocking consumer: Inverter, clocking error 0Hz - 1MHz <25V CM and DM >10kHz Clocking consumer: inverter, fundamental wave 0Hz - 1MHz <25V CM and DM 0-2kHz Clocking consumer: DC/DC converter 0Hz - 100MHz <25V CM and DM >50kHz Clocking consumer: heater 0Hz - 1MHz <25V CM and DM about 50Hz Clocking consumer: electric refrigerant compressor 0Hz - 100MHz <25V CM and DM about 10kHz isolation guard T=CY * 1 MOhm, about 1 Hz Full reload CM <1Hz, recurring Current ripple (direct current charging) Approx. 5-100kHz 100A*100mOhm = 10V CM and DM >100kHz

The approach to avoiding false triggering of the protective circuit is in particular to link several features with one another.

For example, a bandpass filter can be provided for the voltage measurement, which can be implemented using hardware or software, for example. This enables common-mode interference in human body resistance to be differentiated from interference from an insulation monitor, in particular downwards, and from common-mode interference from clocking components, in particular upwards. This reduces interaction of the protective circuit with the insulation monitor, high-voltage consumers and a charging station (EVSE).

For example, a logical linkage of the voltage release for plus potential and minus potential is provided. This enables a reliable distinction to be made between common-mode interference and differential-mode interference, so that only common-mode interference then needs to be considered. This reduces interaction of the protection circuit with clocking consumers.

For example, a minimum transfer stroke, for example 50 V, is taken into account, i. H. the protective circuit is only then triggered. Small disturbances are thus ignored. This reduces interaction of the protection circuit with clocking consumers.

For example, a moving average, i. H. an average value of the voltage over a predetermined period of time, and the protective circuit is only triggered when it is reached. Very low-impedance and regular disturbances are rated weaker as a result. This reduces interaction of the protection circuit with clocking consumers.

Exemplary embodiments of the invention are explained in more detail below with reference to drawings.

• 1 schematisch eine Ausführungsform eines Gleichstromnetzes mit einer Ausführungsform einer Schutzvorrichtung,
• 2 schematisch eine Ausführungsform eines Gleichstromnetzes mit einer Ausführungsform der Schutzvorrichtung mit einer bauteiloptimierten Schutzschaltung, und
• 3 schematisch eine Ausführungsform der Schutzvorrichtung mit einer bauteiloptimierten Schutzschaltung.

show:

• 1 schematically an embodiment of a direct current network with an embodiment of a protective device,
• 2 schematically an embodiment of a DC network with an embodiment of the protection device with a component-optimized protection circuit, and
• 3 schematically an embodiment of the protection device with a component-optimized protection circuit.

Corresponding parts are provided with the same reference symbols in all figures.

Based on 1 until 3 a protective device 8 for an electrical DC network 1, in particular for a high-voltage network, is described below. In the examples shown, the high-voltage network is a high-voltage vehicle electrical system 3 of a vehicle 2, in particular an electric vehicle or hybrid vehicle, in which the protective device 8 is advantageously used. However, the protective device 8 can alternatively or additionally also be used in a DC charging station 5 to which the vehicle 2 and other vehicles, in particular electric vehicles and hybrid vehicles, can be connected for electrically charging a high-voltage battery 6 of the vehicle 2 . When the vehicle 2 is connected, the DC network 1 then includes the vehicle electrical system 3, in particular the high-voltage vehicle electrical system 3, of the vehicle 2 and the DC charging station 5. The high-voltage battery 6 of the vehicle 2, which is electrically charged at this DC charging station 5, is used in particular to provide electrical energy for at least one electric drive unit of the vehicle 2 for driving the vehicle 2.

Y-capacitors CyF+, CyF-, CyL+, CyL- are used both in the vehicle 2 and in the DC charging station 5 as a measure to reduce the emission of EMC interference (EMC=electromagnetic compatibility). In particular, Y-capacitors CyF+, CyF-, CyL+, CyL- are mostly cheaper and more compact EMC filter measures compared to inductive interference suppression filters, for example common or differential mode chokes. From an EMC point of view, it would therefore be advantageous to use Y-capacitors CyF+, CyF-, CyL+, CyL- with large capacitance values.

Disadvantageous in an electrified vehicle 2, i. H. for example in an electric vehicle or hybrid vehicle, however, is that an energy content of the Y-capacitors CyF+, CyF-, CyL+, CyL- can be felt by a vehicle user if he can touch a high-voltage potential HV+, HV- and at the same time is in connection with the ground potential . He then receives an electric shock. Depending on the size of this electric shock, this can be hazardous to your health. For example, it can lead to ventricular fibrillation or death. Such an electric shock represents a so-called "simple error" and should be avoided. Therefore, this energy content of the Y-capacitors CyF+, CyF-, CyL+, CyL- is normatively limited in order to rule out any risk to the vehicle user.

From the point of view of high-voltage safety, small capacitance values of the Y-capacitors CyF+, CyF-, CyL+, CyL- are advantageous. Normatively, for example regulated in regulation LV123, there is the requirement not to exceed a maximum energy content, in particular 0.2 J, in the Y-capacitors CyF+, CyF-, CyL+, CyL- or so-called "alternative measures", i . H. alternative measures, such as increased isolation. However, this always has the consequence that when two high-voltage systems are coupled, for example vehicle 2 and DC charging station 5, both participants must always have this reinforced insulation available at the same time when choosing reinforced insulation as an "alternative measure". However, this cannot currently be guaranteed.

In other standards, for example SAE J1772, IEC 60479-1 and IEC60479-2, the energy content of the Y-capacitors CyF+, CyF-, CyL+, CyL- is not mentioned as a quantity that is hazardous to health and must not be exceeded, but rather a charge quantity as a damaging mechanism, which must not exceed a specified value. For example, a graph of a relation between a duration of a body current and a value of the body current is given for this purpose. An alternative route such as increased insulation is not accepted here.

1 shows a circuit structure of an embodiment of the electrical direct current network 1 designed as a high-voltage network during a direct current charging process of the vehicle 2. The direct current network 1 therefore includes the high-voltage vehicle electrical system 3 of the vehicle 2 and the direct current charging station 5 connected to it by means of a charging cable 4. In the example shown, the charging cable 4 is already connected with Connection contacts AK+, AK- of a DC charging connection of the vehicle 2 are connected and charging contactors LS+, LS- of the vehicle 2 in high-voltage potential lines HV+L, HV-L are still open.

On the left is the DC charging station 5 with a charging station voltage source 13, a charging station internal resistance R _LS and the Y-capacitors CyL+, CyL-.

The charging cable 4 is shown to the right.

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

In addition, the human body MK is shown in this circuit diagram with a body resistance R _K and a switch symbol for an insulation fault IF, for example with a defective charging cable 4, here an example of a fault at the positive potential HV+. The insulation fault IF can also occur at the negative potential HV-. This is not shown here. If the insulation fault IF occurs, the switch symbol is closed. With such an insulation fault IF and contact of the human body MK with one of the high-voltage potentials HV+, HV- and a reference potential M, a discharge occurs through the human body MK.

In order to avoid this discharge through the human body MK or at least reduce it to a permissible level, in particular with regard to a health hazard, a protective device 8 with a protective circuit 9 for reducing the electric shock through the Y-capacitors CyF+, CyF-, CyL+, CyL - intended. In the example shown, the protective device 8 includes a first voltage measuring device SV1 between the positive potential line HV+L and the reference potential line ML for measuring a voltage between the positive potential line HV+L and the reference potential line ML, i. H. between the positive potential HV+ and the reference potential M, in particular ground potential, in particular the vehicle body shell ground, and a second voltage measuring device SV2 between the negative potential line HV-L and the reference potential line ML for measuring a voltage between the negative potential line HV-L and the reference potential line ML, d. H. between the negative potential HV and the reference potential M, in particular ground potential, in particular the vehicle body shell ground.

The voltage measurements, in particular the voltage measuring devices SV1, SV2, control the occurrence of at least one predetermined triggering criterion or several predetermined triggering criteria, determined by means of these voltage measurements, in particular by means of the voltage measuring devices SV1, SV2, for example in the event of a determined voltage change on an e-function with a time constant in one specified frequency band range and/or an associated protective switch SS1, SS2 when it is determined that a specified voltage value is not reached. The protective switches SS1, SS2 are, for example, each in the form of a semiconductor switch, for example a MOSFET. As a result, a discharge network is switched between the positive potential HV+ and the reference potential M, in particular the body shell, or a discharge network between the negative potential HV− and the reference potential M, in particular the body shell. In the example shown, these discharge networks are protective circuit parts 9.1, 9.2 of the protective circuit 9.

The respective discharge network, here the respective protective circuit part 9.1, 9.2, preferably consists of an electrical series connection of a resistor R, R1, R2 and a protective resistor Rs, Rs1, Rs2.

In the example shown, the electrical resistor R, R1, R2 is a voltage-dependent electrical resistor, which is designed in such a way that a resistance value of the voltage-dependent electrical resistor is reduced, in particular increasingly reduced, when the electrical voltage across terminals of the voltage-dependent electrical resistor increases, with a maximum resistance value of the voltage-dependent electrical resistance is a maximum of 800 Ω, in particular a maximum of 600 Ω, in particular is smaller, in particular is significantly smaller than the human body resistance R _K , in particular is a maximum of 200 Ω, in particular is a maximum of or less than 50 Ω, for example less than is 5Ω. This significantly reduces the flow through the human body. The voltage-dependent resistor is, for example, a varistor or a series circuit and/or parallel connection of several varistors, for example with and/or without additional circuitry.

Alternatively, the electrical resistance R, R1, R2 is an electrical resistance with a fixed resistance value of a maximum of 800 Ω, in particular a maximum of 600 Ω, in particular smaller, in particular significantly smaller, than the human body resistance R _K , in particular a maximum of 200 Ω, in particular a maximum or smaller than 50 Ω, for example less than 5 Ω. This also significantly reduces the flow through the human body.

For example, only the resistor R, R1, R2 can also be provided. The electrical protective resistor Rs, Rs1, Rs2 serves to prevent the respective protective switch SS1, SS2 from being destroyed by an excessively high current. The electrical protective resistor Rs, Rs1, Rs2 can therefore be omitted, for example, if the electrical resistor R, R1, R2, in particular in its design as a voltage-dependent electrical resistor, always ensures that a maximum current flow is limited in such a way that it does not lead to a Destruction of the respective circuit breaker SS1, SS2 can lead.

In the example shown according to 1 the protective device 8 with the protective circuit 9 is shown arranged in the vehicle 2 . However, it can also be arranged in the DC charging station 5 with the same function.

In the protective device 8 shown here, in particular the protective circuit 9, in particular the respective protective circuit part 9.1, 9.2, an error is detected via the voltage measurement in relation to the reference potential M.

During a DC charging process in which the in 1 charging contactors LS+, LS- shown open are closed, the high-voltage potentials HV+, HV- do not necessarily have to be distributed symmetrically in relation to the reference potential M, but a minimum insulation value of the high-voltage potentials HV+, HV- to the reference potential M must be ensured, for example greater than 100 ohms/volt. Human touching of a high-voltage potential HV+, HV- is reflected in a reduction in insulation resistance and, as a result, in a shift in the high-voltage potentials HV+, HV- in relation to the reference potential M.

An insulation monitor in the vehicle 2 or in the direct current charging station 5 checks the insulation resistances cyclically, but the period of time before an insulation fault IF is detected, at a maximum of 30 seconds in the vehicle 2 or a maximum of two minutes in the direct current charging station 5, is far too long to provide protection against a To be able to represent the human impact in an open isolation from the energy stored in the Y-capacitors CyF+, CyF-, CyF+, CyF-.

The functioning of the protective device 8 with its protective circuit 9 for reducing a Cy shock is based, for example, on the limit values described in the standard SAE J1772, IEC 60479-1 and IEC60479-2 with regard to the risk potential. The amount of charge that flows through the human body MK and is shown in a diagram is named as the damaging mechanism. The aim is therefore to identify and reduce the body current as quickly as possible in order to minimize the charge that has flowed. Controlling the mechanical charging contactors LS+, LS- and/or main contactors HS+, HS- alone would be too slow for this.

In the protective circuit 9 described above, a drop in the insulation value is quickly detected by the voltage measurement and the electrical resistance R, R1, R2 to the relevant high-voltage potential HV+, HV- with body resistance R _K or Y-capacitor CyF+ is immediately detected, for example via a hardware circuit , CyF-, CyL+, CyL- connected in parallel. The voltage across this high-voltage potential HV+, HV- and the reference potential M is thus abruptly reduced. The current flow through the human body MK decreases proportionally with the voltage reduction.

The respective other high-voltage potential HV-, HV+ increases its voltage with respect to the reference potential M to the same extent, but is not touched by the human body MK and is therefore non-critical.

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

In an alternative fault detection not shown here via a fault current measurement using a fault current measuring device, a fault current detection is used instead of fault detection via the voltage measurement of the respective high-voltage potential HV+, HV- based on the reference potential M. For this purpose, the protective device 8 includes the fault current measuring device in the reference potential line ML. The first circuit breaker SS1 and/or the second circuit breaker SS2 can be controlled to close when a fault current is measured by means of the fault current measuring device and are therefore controlled accordingly in such a case and thereby closed. A current evaluation unit coupled to the fault current measuring device and the circuit breakers SS1, SS2 is advantageously provided here for evaluating the measured fault current and for controlling the first circuit breaker SS1 and/or the second circuit breaker SS2 depending on the measured fault current.

However, this method is more difficult because the relatively high charging direct current has to be analyzed for a very low leakage current. In addition, a distinction must be made between common-mode and differential-mode interference with the error current, since the output current of the DC charging station 5 also has a so-called ripple current, i. H. contains an alternating current component.

A fault detection via the voltage measurement is therefore easier to implement and advantageous. In the following, therefore, error detection by means of voltage measurement is presented in more detail.

The protective device 8 with its protective circuit 9 allows compliance with specified standards, for example the standard IEC 60479-1. The higher the DC charging voltage, the higher the voltage across the Y-capacitors CyF+, CyF-, CyL+, CyL-. With an assumed body resistance R _K , this also results in the voltage of the
Y-capacitors CyF+, CyF-, CyL+, CyL- proportionally higher current at the beginning of the touch process. The current through the body decreases as a capacitor discharges across a resistor, specifically in the form of an exponential function. The current at the beginning of touching is calculated from the quotient of voltage and resistance. With an assumed maximum charging voltage of 920 V and a high-voltage potential distribution that is also assumed to be symmetrical in relation to the reference potential M (460 V across each Y-capacitor), an initial value of the touch current of 460 V / 1200 ohms = 383 mA results. Starting from this initial current value, this current can be converted to a sinusoidal alternating current by dividing by the square root of 6. This corresponds to the value on the X-axis in the so-called C1 characteristic in the SAE J 1772 standard. The duration of this current can be determined by calculating the time constant of the capacitor discharge t = R x C. The corresponding time period (Y-axis) corresponds to 3 x t. For example, a dwell time of approx. 100 ms in this state is still permissible. A remaining body current of less than 5 mA was chosen as the target, ie the residual voltage must be less than 6 V.

The higher the voltage across a Y-capacitor CyF+, CyF-, CyL+, CyL-, for example in the case of an asymmetrical high-voltage potential distribution in relation to the reference potential M, the shorter the maximum dwell time. A current of more than 500 mA is not allowed, since a maximum voltage of 600 V would appear across a Y-capacitor CyF+, CyF-, CyL+, CyL-. The loading process must be aborted.

The protective device 8 with its protective circuit 9 can therefore be used to calculate whether it is still able to comply with the requested maximum current durations. If this condition is not met, the charging process must be stopped immediately, as another error would endanger people. Input variables for this calculation are voltage measurements across the Y-capacitors CyF+, CyF-, CyL+, CyL- of both high-voltage potentials HV+, HV-, knowledge of the circuit's own reaction speed and the table of values for the maximum permissible current dwell times.

To determine a safe or unsafe operating state, the circuit can be expanded to include two additional voltage measuring devices, not shown here, with the third voltage measuring device being arranged between the positive potential line HV+L and the reference potential line ML for measuring a voltage between the positive potential line HV+L and the reference potential line ML and the fourth voltage measuring device is arranged between the negative potential line HV-L and the reference potential line ML for measuring a voltage between the negative potential line HV-L and the reference potential line ML, and wherein in the positive potential line HV+L between a connection point to first voltage measuring device SV1 and a connection point to the third voltage measuring device, a first switching unit, in particular the first charging contactor LS+, is arranged and in the negative potential line ML between a connection point to the second voltage measuring device SV2 and a connection point to the fourth voltage measuring device, a second switching unit, in particular the second charging contactor LS-, is arranged. Thus, even before the charging contactors LS+, LS- are switched on and the capacity of the Y capacitors CyF+, CyF-, CyL+, CyL- is increased as a result of the parallel connection of DC charging station 5 and vehicle 2, it can be determined whether the protective circuit 9 in the Would be able to comply with the legal limit values in the event of faulty insulation, for example in the charging cable 4. Ideally, the so-called contactor adhesive detection of the vehicle 2 is used for all four voltage measurements. The condition, however, is that the maximum time delay before switching on the resistor R, R1, R2 is not exceeded during the voltage evaluation. This is therefore advantageously implemented on the hardware side and no evaluation is carried out using a microprocessor.

For example, an in 3 shown voltage evaluation unit 12, in which by means of the voltage measuring devices SV1, SV2 and the two other voltage measuring devices detected voltages are evaluated and the circuit breakers SS1, SS2 can be controlled accordingly. Provision can also be made for this voltage evaluation unit 12 to be able to output further information, in particular to slower control devices or to the DC charging station 5. Examples of information include opening or closing the charging contactors LS+, LS-, interrupting the DC charging process, opening or closing the main contactors HS+, HS- of the high-voltage battery 6, an initiation of the active discharge of the high-voltage intermediate circuit of the vehicle 2 and/or the information that everything is OK and the DC charging process can thus be started.

However, since the protective circuit 9 can provide an equivalent discharge path to the body current when a high-voltage potential HV+, HV- is touched very quickly one after the other, it is advantageously provided that the protective device 8 described here, in particular its protective circuit 9, is designed in such a way that it is able to is to be able to switch on independently, i. H. to close the first and/or second circuit breaker SS1, SS2 and, after a short dwell time in this switched-on state, to open the respective closed circuit breaker SS1, SS2 again. On communication within the vehicle 2 to a higher-level control unit, which takes measures such as opening the charging contactors LS+, LS- and/or main contactors HS+, HS- and discharging the Y-capacitors CyF+, CyF-, CyL+, CyL- is advantageously omitted here. The detection of a permanent insulation fault, i. H. a low insulation resistance and not, for example, a defective protective sheath of a high-voltage cable, is advantageously detected by another device, for example by an insulation monitor and/or by measuring a high-voltage potential distribution, which is not part of the protective device 8 and its protective circuit 9 described here and is also not related to this one. As mentioned, the protective device 8 described here and its protective circuit 9 are able to be triggered repeatedly at very short intervals and thus also in the event of rapid recurring contact by a person, thus ensuring protection for the person. Accidental triggering, for example due to an EMC fault, does not lead to further measures in the vehicle 2, such as the high-voltage system being switched off incorrectly. Due to the self-sufficient function of the protective device 8, in particular of its protective circuit 9, flexible and simple integration into an existing high-voltage system can be implemented. The self-sufficient function also reduces the safety requirements for the protective device 8 and its protective circuit 9; for example, a secure function/communication with a further control device is no longer required.

The protective device 8 can also be used in a direct current network 1 without the direct current charging station 5, in particular for driving the vehicle 2, for alternating current charging as well as for assembly and service work. The only difference to the situation when charging with direct current is that the direct current charging station 5 is missing. A defective high-voltage cable or a defective housing of high-voltage electronics as a result of an accident, for example, can be considered as a fault mechanism. The protective device 8 with its protective circuit 9 can also reduce the amount of charge in the event of damage to the high-voltage system during assembly or service.

The protective circuit 9 for reducing the Y shock caused by an insulation fault IF remains identical to that described above. For this purpose, the protective device 8 with its protective circuit 9 is of course arranged in the vehicle 2 . The function is identical to that described above for the insulation fault during DC charging. Upon detecting the reduction in tension between one of the High-voltage potentials HV+, HV- and the reference potential M are connected to the respective electrical resistance R, R1, R2 and the total capacitance of the Y-capacitors CyF+, CyF-, CyL+, CyL- of the affected high-voltage potential HV+, HV- is discharged. In addition, an opening of the main contactors HS+, HS- of the high-voltage battery 6 is advantageously commanded and an active discharge of the X-capacitor Cx and both Y-capacitors CyF+, CyF- of the vehicle 2 is initiated. The charging contactors LS+, LS- are already open beforehand and always remain open.

2 shows a component-optimized protective circuit 9. In the case of the protective circuit 9 for reducing a Cy shock, it can be assumed that only a high-voltage potential HV+, HV- is connected to the reference potential M, for example the housing ground, via the body resistance R _K . If both high-voltage potentials HV+, HV- were connected to the reference potential M, in particular the housing ground, this would be equivalent to a short-circuit in the high-voltage battery 6 or DC charging station 5, which must be separated by a fuse or a current sensor with a shutdown device controlled by it.

This makes it clear that the protection circuit 9 is never used at the same time to reduce a Cy shock for the plus potential HV+ and the minus potential HV-. Therefore, a single resistor R and optionally a single protective resistor Rs can be used to protect both high-voltage potentials HV+, HV-, as in FIGS 2 and 3 shown. There are therefore no two protective circuit parts 9.1, 9.2 required. The voltage measurements using the two voltage measuring devices SV1, SV2 and the two protective switches SS1, SS2 for switching on the protective circuit 9 must continue to exist. The 2 and 3 show such a component optimization.

3 shows an embodiment of the protective device 8, in particular with the component-optimized protective circuit 9, ie without the two protective circuit parts 9.1, 9.2. The protective switches SS1, SS2 are each designed as MOSFETs here, but other semiconductor switches are also possible, for example IGBTs or thyristors. The protective device 8 , in particular its protective circuit 9 , is reduced here to the additional effort required to be integrated in the vehicle 2 or at the DC charging station 5 . Connections AHV+, AHV-, AM to the positive potential HV+, negative potential HV- and reference potential M can be kept very small, since a current in the millisecond range only flows in the event of a fault. Otherwise the connections AHV+, AHV-, AM are current-free and are only used for voltage measurement. It follows from this that rapid integration of the protective device 8 with its protective circuit 9 into an existing high-voltage system is possible with minor changes. If there is more planning time, this function can of course also be integrated into an existing device.

In all embodiments, the protective device 8 thus includes the first voltage measuring device SV1 between the plus potential line HV+L and the reference potential line ML for measuring the voltage between the plus potential line HV+L and the reference potential line ML, and the second voltage measuring device SV2 between a minus 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.

Furthermore, the protective device 8 comprises the protective circuit 9 in all embodiments.

The protection circuit 9 includes, for example, as in the 2 and 3 shown, the electrical series connection of the electrical resistor R and the first protective switch SS1 between the positive potential line HV+L and the reference potential line ML and the electrical series connection of, ie the same, electrical resistor R and the second protective switch SS2 between the negative potential line HV-L and the reference potential line ML.

The electrical resistance R is, for example, an electrical resistance with a fixed resistance value of a maximum of 800 Ω, in particular a maximum of 600 Ω, in particular smaller, in particular significantly smaller, than the human body resistance R _K , in particular a maximum of 200 Ω, in particular a maximum of or less than 50 Ω, for example less than 5 Ω. This significantly reduces the flow through the human body.

Alternatively, the electrical resistance is R, as in 2 and 3 shown, for example, a voltage-dependent electrical resistor, which is designed in particular in such a way that the resistance value of the voltage-dependent electrical resistor is reduced with an increasing electrical voltage across the terminals of the voltage-dependent electrical resistor, in particular increasingly reduced, with the maximum resistance value of the voltage-dependent electrical resistor in particular is a maximum of 800 Ω, in particular a maximum of 600 Ω, in particular is smaller, is in particular significantly smaller than the human body resistance R _K , in particular a maximum of 200 Ω, in particular a maximum of or less than 50 Ω, for example less than 5 Ω. This therefore applies to all resistance values that the voltage-dependent electrical resistance can have given the electrical voltages that occur across its connections. This significantly reduces the flow through the human body. The voltage-dependent electrical resistor is thus designed in such a way that its resistance value decreases as the voltage across its connections increases.

The electrical resistor R designed as a voltage-dependent electrical resistor is designed, for example, as a varistor or as a series connection and/or parallel connection of a plurality of varistors with and/or without additional circuitry.

Alternatively, the protection circuit 9, as in 1 shown, for example two protective circuit parts 9.1, 9.2, the first protective circuit part 9.1 for example comprising the electrical series circuit of the first electrical resistor R1 and the first protective switch SS1 between the plus potential line HV+L and the reference potential line ML and the second protective circuit part 9.2 for example the electrical series circuit of the second includes electrical resistance R2 and the second circuit breaker SS2 between the negative potential line HV-L and the reference potential line ML.

The respective electrical resistance R1, R2 is, for example, an electrical resistance with a fixed resistance value of a maximum of 800 Ω, in particular a maximum of 600 Ω, in particular less than, in particular significantly less than, the human body resistance R _K , in particular a maximum of 200 Ω, in particular a maximum or less than 50 Ω, for example less than 5 Ω. This significantly reduces the flow through the human body.

Alternatively, the respective electrical resistance R1, R2, as in 1 shown, for example, a voltage-dependent electrical resistor, which is designed in particular in such a way that the resistance value of the voltage-dependent electrical resistor is reduced as the electrical voltage across the terminals of the voltage-dependent electrical resistor increases, in particular increasingly reduced, with the maximum resistance value of the voltage-dependent electrical resistor being a maximum is 800 Ω, in particular a maximum of 600 Ω, in particular is smaller, in particular significantly smaller than the human body resistance R _K , in particular is a maximum of 200 Ω, in particular a maximum of or less than 50 Ω, for example less than 5 Ω. This therefore applies to all resistance values that the voltage-dependent electrical resistance can have given the electrical voltages that occur across its connections. This significantly reduces the flow through the human body. The voltage-dependent electrical resistor is thus designed in such a way that its resistance value decreases as the voltage across its connections increases.

The respective electrical resistor R1, R2 designed as a voltage-dependent electrical resistor is designed, for example, as a varistor or as a series connection and/or parallel connection of a plurality of varistors with and/or without additional circuitry.

In both variants, the first circuit breaker SS1 and/or the second circuit breaker SS2 is/are when at least one predetermined triggering criterion or several predetermined triggering criteria occur, which is determined by means of the first voltage measuring device SV1 and/or by means of the second voltage measuring device SV2, for example in the case of a by means of the first voltage measuring device SV1 and/or the voltage change determined by means of the second voltage measuring device SV2 on an e-function with a time constant in a predefined frequency band range and/or when the voltage falls below a predefined voltage value determined by means of the first voltage measuring device SV1 and/or by means of the second voltage measuring device SV2, can be triggered to close . This evaluation, i. H. the determination of the occurrence of the at least one triggering criterion or of the plurality of triggering criteria by means of the first voltage measuring device SV1 and/or by means of the second voltage measuring device SV2 takes place digitally or analogously, for example.

The protective device 8 thus has an evaluation of voltage levels between the positive potential HV+ and the reference potential M and between the negative potential HV- and the reference potential M. The protective switches SS1, SS2 are each controlled via this if the at least one predetermined triggering criterion is given or the multiple predetermined triggering criteria are given .

As an alternative to the two voltage measuring devices SV1, SV2, a fault current measuring device can be provided in the reference potential line ML. Then in both variants of the protection circuit 9 the first circuit breaker SS1 and/or the second circuit breaker SS2 can be controlled to close when a fault current is measured by means of the fault current measuring device.

In one possible embodiment, as already mentioned above, the electrical resistor R, R1, R2 is electrically connected in series with an electrical protective resistor Rs, Rs1, Rs2. i.e. the electrical resistance R alone is electrically connected in series with the protective electrical resistance Rs alone, as in FIGS 2 and 3 shown, or the electrical resistor R1, R2 of the respective protective circuit part 9.1, 9.2 is electrically connected in series with the electrical protective resistor Rs1, Rs2 of the respective protective circuit part 9.1, 9.2, as in FIG 1 shown.

The electrical series connection of the respective electrical resistor R, R1, R2 and the respective electrical protective resistor Rs, Rs1, Rs2 forms a discharge network between the positive potential HV+ and the reference potential M or a discharge network between the negative potential HV- and the reference potential M. The electrical Protective resistor Rs or the respective electrical protective resistor Rs1, Rs2 serves to prevent the respective protective switch SS1, SS2 from being destroyed by an excessively high current. The electrical protective resistor Rs or the respective electrical protective resistor Rs1, Rs2 can be omitted, for example, if the electrical resistor R or the respective electrical resistor R1, R2, in particular in its design as a voltage-dependent electrical resistor, always ensures that a maximum current flow is limited in this way is that it cannot lead to the destruction of the respective circuit breaker SS1, SS2.

If the electrical protective resistor Rs or the respective protective resistor Rs1, Rs2 is present, the protective circuit 9 thus includes the electrical series connection of the electrical resistor R, the electrical protective resistor Rs and the first protective switch SS1 between the positive potential line HV+L and the reference potential line ML and the electrical series connection of the resistor R, the electrical protective resistor Rs and the second protective switch SS2 between the negative potential line HV-L and the reference potential line ML, as in FIGS 2 and 3 shown, or the protective circuit 9 comprises the two protective circuit parts 9.1, 9.2, the first protective circuit part 9.1 comprising the electrical series connection of the first electrical resistor R1, the first electrical protective resistor Rs1 and the first protective switch SS1 between the positive potential line HV+L and the reference potential line ML and the second protective circuit part 9.2 comprises the electrical series connection of the second electrical resistor R2, the second electrical protective resistor Rs2 and the second protective switch SS2 between the negative potential line HV-L and the reference potential line ML, as in 1 shown.

For example, as in 3 shown, a common voltage evaluation unit 12 coupled to the voltage measuring devices SV1, SV2 and the protective switches SS1, SS2 for evaluating the voltage determined by the first voltage measuring device SV1 and the voltage determined by the second voltage measuring device SV2 and for controlling the first protective switch SS1 and/or the second Circuit breaker SS2 is provided when the at least one triggering criterion or the plurality of triggering criteria occurs, which is determined by means of the first voltage measuring device SS1 and/or by means of the second voltage measuring device SS2.

When using the residual current measuring device, for example, a current evaluation unit coupled to the residual current measuring device and the protective switches SS1, SS2 is provided for evaluating the measured residual current and for controlling the first protective switch SS1 and/or the second protective switch SS2 depending on the measured residual current.

In an embodiment not shown here, it can be provided that the common voltage evaluation unit 12 is coupled to a third voltage measuring device and a fourth voltage measuring device, the third voltage measuring device being connected between the plus potential line HV+L and the reference potential line ML to measure the voltage between the plus potential line HV+L and the reference potential line ML and the fourth voltage measuring device is arranged between the minus potential line HV-L and the reference potential line ML for measuring the voltage between the minus potential line HV-L and the reference potential line ML, and wherein in the plus potential line HV+L between the connection point to the first voltage measuring device SV1 and the connection point to the third voltage measuring device the first switching unit, in particular in the form of the charging contactor LS+, is arranged in the positive potential line HV+L and in the negative potential line HV-L between the connection point to the second voltage measuring device SV2 and the connection point to fourth voltage measuring device, a second switching unit, here in the form of the charging contactor LS- in the negative potential line HV-L, is arranged.

The respective protective switch SS1, SS2 is designed, for example, as a semiconductor switch, for example as a MOSFET, IGBT or thyristor.

Advantageous possible uses of the protective device 8 are described below. In vehicles 2 with a high-voltage system in the 800 V level, it becomes difficult to comply with the normatively required limit values for discharge through Y-capacitors CyF+, CyF-, CyL+, CyL-. This applies in particular to existing vehicles 2 which do not allow any adjustments in the high-voltage system for large additional components due to the installation space already occupied in the vehicle 2 . The solution described is suitable here, since it can be installed in the vehicle 2 in a simple, cost-effective manner and with little space requirement.

Furthermore, the solution described satisfies regulations, in particular from standards, which makes it easier or even possible to register the vehicle 2 in the first place. With the addition of small electronics, this protective device 8 and its protective circuit 9 achieve the limit values without having to change anything in the high-voltage system and its components.

The maximum energy content of 0.2 J required in the LV123 is already exceeded at 632 V by the DC charging station 5. "Alternative measures", i. H. alternative measures are therefore absolutely necessary. The only solution currently being discussed is double insulation. All coupled systems, i. H. Vehicle 2 and DC charging station 5 must then have reinforced insulation at the same time, which cannot currently be guaranteed. However, the energy flowing through the human body MK can also be kept at a value below 0.2 J by the protective device 8 and its protective circuit 9 . It thus represents a further solution for "alternative measures".

The protective device 8 and its protective circuit 9 make it possible to reduce the dangerous discharge current of the Y-capacitors CyF+, CyF-, CyL+, CyL- upon human contact if the insulation is damaged during direct current charging, for example if the charging plug or charging cable 4 is damaged . In all other vehicle states, if the insulation is damaged, the dangerous discharge current is reduced when people come into contact with it.

Improved EMC interference suppression is possible through a larger design of the Y capacitors CyF+, CyF-, CyL+, CyL-. A waiver of the requirement for double insulation of the entire high-voltage system is made possible. This applies to vehicle 2 and DC charging station 5.

The protective device 8 with its protective circuit 9 can be arranged in the vehicle 2 and/or in the DC charging station 5 .

A resistance value of 500 Ω is assumed or specified as the above-mentioned human body resistance R _K , ie as the body resistance of a person, ie the human body MK, in particular in accordance with information in standards to be observed.

i.e. the human body resistance is accordingly defined as a resistance value of 500 Ω.

Reference List

1

direct current network

2

vehicle

3

On-board network, high-voltage on-board network

4

charging cable

5

DC charging station

6

high-voltage battery

7

battery power source

8th

protective device

9

protection circuit

9.1, 9.2

protection circuit part

12

voltage evaluation unit

13

charging station voltage source

AHV+, AHV-, AM

Connection

AK+, AK-

connection contact

Cx

X capacitor

CyF+, CyF-

Y-capacitor vehicle

CyL+, CyL-

Y capacitor DC charging station

HS+, HS-

main contactor

HV+, HV-

high-voltage potential

HV+L, HV-L

high-voltage potential line

IF

insulation fault

LS+, LS-

charging contactor

M

reference potential

ML

reference potential line

MK

human body

RBatt

internal battery resistance

R, R1, R2

Resistance

RK

body resistance

RLS

charging station internal resistance

Rs, Rs1, Rs2

protective resistor

SS1, SS2

circuit breaker

SV1, SV2

tension measuring device

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102017009355 A1 [0002]
• DE 102019008833 [0003]

Claims (10)

Protective device (8) for an electrical DC network (1), in particular for a high-voltage network (3), characterized by - a first voltage measuring device (SV1) between a positive potential line (HV+L) and a reference potential line (ML) for measuring a voltage between the positive potential line (HV+L) and the reference potential line (ML) and a second voltage measuring device (SV2) between a negative potential line (HV-L) and the reference potential line (ML) for measuring a voltage between the negative potential line (HV-L) and the reference potential line (ML) , and characterized by a protective circuit (9) with - a first protective switch (SS1) between the positive potential line (HV+L) and the reference potential line (ML) and a second protective switch (SS2) between the negative potential line (HV-L) and the reference potential line ( ML) and - at least one electrical resistor (R, R1, R2), which is designed as an electrical resistor with a fixed resistance value of a maximum of 800 Ω or as a voltage-dependent electrical resistor, - the first circuit breaker (SS1) and/or the second circuit breaker (SS2) can be controlled to close when at least one triggering criterion is determined by means of the first voltage measuring device (SV1) and/or by means of the second voltage measuring device (SV2). Protective device (8) according to one of the preceding claims, characterized in that the at least one electrical resistor (R, R1, R2) designed as a voltage-dependent electrical resistor is designed in such a way that a resistance value of the voltage-dependent electrical resistor increases when the electrical voltage increases Connections of the voltage-dependent electrical resistance are reduced, with a maximum resistance value of the at least one electrical resistance designed as a voltage-dependent electrical resistance (R, R1, R2) being a maximum of 800 Ω. Protective device (8) according to one of the preceding claims, characterized in that the fixed resistance value of the at least one electrical resistor (R, R1, R2) designed as an electrical resistor with a fixed resistance value or the maximum resistance value of the at least one electrical resistor designed as a voltage-dependent electrical resistor resistance (R, R1, R2) is less than 50 Ω. Protective device (8) according to one of the preceding claims, characterized in that the voltage-dependent electrical resistance is designed as a varistor or as a series connection and/or parallel connection of several varistors with and/or without additional circuitry. Protective device (8) according to one of the preceding claims, characterized in that the protective circuit (9) comprises at least one electrical protective resistor (Rs, Rs1, Rs2) which is electrically connected in series with the at least one electrical resistor (R, R1, R2). is. Protective device (8) according to one of the preceding claims, characterized in that the protective circuit (9) - an electrical series connection of the electrical resistor (R) and the first protective switch (SS1) between the positive potential line (HV+L) and the reference potential line (ML) and - an electrical series connection of the electrical resistor (R) and the second protective switch (SS2) between the negative potential line (HV-L) and the reference potential line (ML). Protective device (8) according to one of the preceding claims, characterized in that the protective circuit (9) comprises two protective circuit parts (9.1, 9.2), the first protective circuit part (9.1) being an electrical series connection of a first electrical resistor (R1) and the first protective switch ( SS1) between the positive potential line (HV+L) and the reference potential line (ML) and the second protective circuit part (9.2) comprises an electrical series connection of a second electrical resistor (R2) and the second protective switch (SS2) between the negative potential line (HV-L) and includes the reference potential line (ML). Vehicle electrical system (3), in particular high-voltage vehicle electrical system (3), for a vehicle (2), comprising a protective device (8) according to one of the preceding claims. Vehicle (2), in particular an electric vehicle or hybrid vehicle, comprising an on-board network (3). claim 8 . Direct current charging station (5), in particular high-voltage direct current charging station, comprising a protective device (8) according to one of Claims 1 until 7 .

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