DE102022002626B3 - Vehicle with a high-voltage electrical system and method for operating the high-voltage electrical system - Google Patents

Abstract

The invention relates to a vehicle (1) with a high-voltage electrical system (2) with a traction battery (3), high-voltage potentials (HV+, HV-), a reference potential (M), insulation resistances (Riso+, Riso-), Y capacitances (Cy+, Cy -), an insulation monitor (4), voltage measuring devices (V1, V2) between the high-voltage potentials (HV+, HV-) and the reference potential (M), a potential distribution control circuit (5) and a processing unit (6), which is designed and set up to determine the current vehicle status and to control the potential distribution control circuit (5) to prevent a potential voltage limit value for the vehicle status from being exceeded, a potential voltage limit value being predetermined for several vehicle statuses or being able to be determined by the processing unit (6).

Description

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

From the prior art, as in the DE 10 2018 211 625 A1 described, an on-board electrical system arrangement for a motor vehicle, a motor vehicle and a method for monitoring an on-board electrical system symmetry are known. The vehicle electrical system arrangement includes a high-voltage energy storage device for providing a first and a second high-voltage potential, between which a total voltage can be tapped, a first insulation resistance between the first high-voltage potential and a mass, and a second insulation resistance between the second high-voltage potential and the Dimensions. The on-board electrical system arrangement is designed symmetrically in such a way that, at least in a certain state of the on-board electrical system arrangement, the first insulation resistance differs from the second insulation resistance by a maximum of a predeterminable amount. The on-board electrical system arrangement has a symmetry monitoring device which is designed to monitor the on-board electrical system symmetry to check whether the first insulation resistance differs from the second insulation resistance by more than the predeterminable amount and, if this is the case, to trigger a predetermined measure.

In the DE 10 2018 116 055 B3 A method and an insulation monitor for resistance-adaptive insulation monitoring are described. In the method for insulation monitoring of an HV system, which has a first line with a first voltage value and a second line with a second voltage value, a first potential difference between the first voltage value and ground and a second potential difference between the second voltage value and ground are formed. A first series connection of a first semiconductor switch with a first resistance is arranged between the first voltage value and ground and a second series connection of a second semiconductor switch with a second resistance is arranged between the second voltage value and ground. A first and a second pulse width modulation are carried out on the two semiconductor switches, with a first and a second pair of resistance values of the two series circuits being modulated by means of the respective pulse width modulation. A first voltage measurement is carried out for the first pair of resistance values and a first pair of values from the first and second potential difference is thereby determined. A second voltage measurement is carried out for the second pair of resistance values, thereby determining a second pair of values from the first and second potential difference. The two pairs of values are used to calculate a first insulation resistance of the first line and a second insulation resistance of the second line.

From the DE 10 2021 003 843 A1 an insulation monitor for a high-voltage electrical system of a motor vehicle and a method for operating the insulation monitor are known. The on-board electrical system includes an HV battery and is galvanically isolated from the vehicle ground. A Y capacitance is provided between the positive potential and the vehicle mass and between the negative potential and the vehicle mass. The insulation monitor has a current source or a voltage source. Furthermore, the insulation monitor includes a voltmeter for measuring at least one of the potentials. The insulation monitor is configured to apply a negative current using the current source when the potential measured by the voltmeter exceeds a predetermined upper value and to apply a positive current using the current source when the potential measured by the voltmeter falls below a predetermined lower value, which reaches a maximum permissible contact current is limited in the event of an insulation fault, and the size of the insulation resistances can be determined based on the voltage measured by the voltmeter and the charged recharging current.

In the DE 10 2018 115 929 A1 A method for transferring energy from a charging device to an on-board electrical system of a vehicle and a system with a charging device and an on-board electrical system of a vehicle connected to the charging device are described. The electrical system has a positive potential, a negative potential and an earth potential. A first Y-capacitor is arranged between the positive potential and the ground potential and a second Y-capacitor is arranged between the negative potential and the ground potential. A first adjustable resistance device is connected in parallel to the first Y-capacitor and a second adjustable resistance device is connected in parallel to the second Y-capacitor. In the method, the charging device is connected to the vehicle electrical system, a first voltage is measured across the first Y capacitor, an ohmic resistance of the first adjustable resistance device and/or the second adjustable resistance device is set as a function of the measured first voltage, and energy is transferred from the charging device into the Transfer on-board network.

The generic writing DE 10 2020 007 868 A1 shows a procedure for Charging an electrical energy storage device of a vehicle, wherein the vehicle is coupled to a DC charging source for a charging process. A DC voltage from the DC charging source is converted into a charging voltage for charging the electrical energy storage device via a DC-DC converter in the vehicle. An insulation monitoring unit of the vehicle determines a potential distribution between a first potential of the vehicle and a second potential of the vehicle and a resistance value of at least one insulation resistance of the vehicle. Depending on the determined potential distribution and the resistance value of the at least one insulation resistor, at least one potential protection resistor of a potential protection circuit is connected between the second potential of the vehicle and a reference potential.

Also the DE 10 2021 003 884 A1 discloses a protective device for an electrical direct current network, in particular for a high-voltage network. The protective device comprises a protective circuit for reducing an electric shock caused by Y capacitors of the direct current electrical network, the protective circuit comprising a first protective switch between a plus potential line and a reference potential line and a second protective switch between a minus potential line and the reference potential line. For testing purposes, a tripping of the protective circuit can be detected via a voltage measurement after a test circuit has been switched on.

The invention is based on the object of specifying a vehicle with a high-voltage on-board electrical system that is improved compared to the prior art and an improved method for operating the high-voltage on-board electrical system.

The object is achieved according to the invention by a vehicle with a high-voltage electrical system with the features of claim 1 and a method for operating the high-voltage electrical system with the features of claim 7.

Advantageous embodiments of the invention are the subject of the subclaims.

A vehicle has a high-voltage electrical system. The term “high voltage”, also abbreviated as HV, is understood to mean in particular an electrical direct voltage that 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 high-voltage electrical system includes a traction battery, i.e. H. an electrochemical energy storage device for supplying energy to at least one electric drive machine for driving the vehicle. The vehicle is therefore in particular an electric vehicle or hybrid vehicle.

Furthermore, the high-voltage electrical system includes a positive high-voltage potential, a negative high-voltage potential, a reference potential designed in particular as a ground potential, an insulation resistance between the positive high-voltage potential and the reference potential, an insulation resistance between the negative high-voltage potential and the reference potential, a Y capacitance between the positive high-voltage potential and the Reference potential, a Y capacitance between the negative high-voltage potential and the reference potential, an insulation monitor electrically coupled to the positive high-voltage potential, the negative high-voltage potential and the reference potential, a voltage measuring device between the positive high-voltage potential and the reference potential for measuring a positive high-voltage potential voltage from the positive high-voltage potential to the reference potential, a voltage measuring device between the negative high-voltage potential and the reference potential for measuring a negative high-voltage potential voltage from the negative high-voltage potential to the reference potential, a potential distribution control circuit and a processing unit which is coupled to the voltage measuring devices for evaluating the measured high-voltage potential voltages and to the potential distribution control circuit for controlling them.

According to the invention, the processing unit is designed and set up to determine a currently existing vehicle status and to control the potential distribution control circuit to prevent a potential voltage limit value for the vehicle status from being exceeded, with a potential voltage limit value being predetermined for several vehicle statuses or being able to be determined by the processing unit. The respective potential voltage limit value is an absolute amount. It therefore applies to both the positive high-voltage potential voltage, here correspondingly with a positive sign, and for the negative high-voltage potential voltage, here correspondingly with a negative sign.

In a method according to the invention for operating the high-voltage on-board electrical system of the vehicle, it is accordingly provided that the processing unit determines the current vehicle status and controls the potential distribution control circuit to prevent the potential voltage limit value being exceeded, which is specified for this vehicle status or is determined by the processing unit before the potential distribution control circuit is activated .

The solution according to the invention thus enables a vehicle condition-dependent limitation of the high-voltage potential voltages to the reference potential to the respective potential voltage limit value. This ensures in particular compliance with normative upper limits for energy/charge stored in the Y capacities. In particular, due to an increasing use of higher voltage levels, for example 800V, in vehicles, the stored energy/charge in the Y capacitances, which are in particular designed as or include filter capacitors, increases. Compliance with the normative upper limits therefore represents a challenge. When charging at a DC charging station, Y capacities in the DC charging station are also electrically connected in parallel to the Y capacities of the vehicle. This leads to a further increase in stored energy/charge.

The solution according to the invention allows larger Y capacitances to be installed in the vehicle, which means that the filtering options of the vehicle's power electronics can be improved. Furthermore, the solution according to the invention makes it possible to prevent overloading of insulation in the DC charging station when charging via a galvanically coupled DC-DC converter. In addition, the solution according to the invention makes it possible for the insulation monitor in the vehicle and/or an insulation monitor in the DC charging station to function even when the potential distribution control circuit is active, i.e. H. with active switching to limit the high-voltage potential voltages to the respective potential voltage limit value.

• - Fahrzeugstatus I: Fahrbetrieb, und
• - Fahrzeugstatus II: Laden der Traktionsbatterie an einer Gleichstromladestation mit einer Ladespannung, die mindestens so groß ist wie eine Batterienennspannung der Traktionsbatterie, und
• - Fahrzeugstatus III: Laden der Traktionsbatterie über einen galvanisch gekoppelten Gleichspannungswandler an einer Gleichstromladestation mit einer Ladespannung und einer Auslegungsspannung ihrer Isolation, die kleiner ist als die Batterienennspannung der Traktionsbatterie, und
• - Fahrzeugstatus IV: Betrieb einer Hochvoltkomponente mit einer Auslegungsspannung ihrer Isolation, die kleiner ist als eine Auslegungsspannung des Hochvoltbordnetzes, über einen galvanisch gekoppelten Gleichspannungswandler.

According to the invention it is provided that a potential voltage limit value is predetermined or can be determined by the processing unit for one

• - Vehicle status I: driving, and
• - Vehicle status II: Charging the traction battery at a DC charging station with a charging voltage that is at least as large as a nominal battery voltage of the traction battery, and
• - Vehicle status III: Charging the traction battery via a galvanically coupled DC-DC converter at a DC charging station with a charging voltage and a design voltage of its insulation that is smaller than the nominal battery voltage of the traction battery, and
• - Vehicle status IV: Operation of a high-voltage component with a design voltage of its insulation that is smaller than a design voltage of the high-voltage on-board electrical system via a galvanically coupled DC-DC converter.

These vehicle statuses require, in particular due to a different total capacity of the Y-capacities active in the respective vehicle status, their own potential voltage limit value, which, in particular in vehicle statuses II and III, also depends on the Y-capacities of the respective DC charging station, by means of which the traction battery is charged. depends and can therefore differ between different DC charging stations.

• Sicherheitsziel I: Reduzierung der maximalen Energie in den Y-Kapazitäten. Bei Fahrzeugen mit höheren Auslegungsspannungen des Hochvoltbordnetzes, d. h. Betriebsspannungen, beispielsweise 850V oder höher, steigt der Energieinhalt der Y-Kapazitäten quadratisch mit der Gleichspannung an. Der in den Y-Kapazitäten gespeicherte Ladungsinhalt steigt proportional mit der Gleichspannung an. Bei den Y-Kapazitäten handelt es sich teilweise um real existierende Bauteile in Form von EMV-Filter-Komponenten (EMV = Elektromagnetische Verträglichkeit) und teilweise um so genannte Streukapazitäten. Die maximal gespeicherte Energie und die maximale Ladungsmenge sind normativ begrenzt, um einen gefährlichen Stromschlag als Folge eines einfachen Isolationsfehlers zu verhindern. Beispielhafte Normen hierzu sind die ISO 17409 und die J1772. Als maximale Energie in den Y-Kapazitäten wird eine komplett unsymmetrische Hochvoltpotentialverteilung betrachtet. Dabei liegt zwischen einem Hochvoltpotential und dem Bezugspotential die volle Batteriespannung der Traktionsbatterie an, während über dem anderen Hochvoltpotential und dem Bezugspotential 0V, d. h. keine Spannung, anliegt. Die in den Y-Kapazitäten gespeicherten Energien, d. h. die Summe der Energien beider Hochvoltpotentiale, können reduziert werden, indem die Unsymmetrie der Hochvoltpotentiale bezogen auf das Bezugspotential eingeschränkt, d. h. begrenzt, wird. Dies wird durch die oben beschriebene Lösung über den entsprechenden Potentialspannungsgrenzwert und die mittels der Verarbeitungseinheit entsprechend angesteuerte Potentialverteilungssteuerungsschaltung zum Verhindern des Überschreitens des Potentialspannungsgrenzwertes erreicht.

In particular, it is provided that the potential voltage limit value for the respective vehicle status is specified or can be determined by the processing unit as a function of at least one safety goal to be met. The following safety objectives are particularly specified:

• Safety objective I: Reduction of the maximum energy in the Y capacities. In vehicles with higher design voltages of the high-voltage electrical system, ie operating voltages, for example 850V or higher, the energy content of the Y capacitances increases as the square of the DC voltage. The charge content stored in the Y capacitances increases proportionally with the DC voltage. The Y capacitances are partly actually existing components in the form of EMC filter components (EMC = electromagnetic compatibility) and partly so-called stray capacitances. The maximum stored energy and the maximum amount of charge are normatively limited to prevent dangerous electric shock as a result of a simple insulation fault. Example standards for this are ISO 17409 and J1772. A completely asymmetrical high-voltage potential distribution is considered the maximum energy in the Y capacitances. The full battery voltage of the traction battery is present between one high-voltage potential and the reference potential, while 0V, ie no voltage, is present across the other high-voltage potential and the reference potential. The energies stored in the Y capacitances, ie the sum of the energies of both high-voltage potentials, can be reduced by limiting, ie limiting, the asymmetry of the high-voltage potentials relative to the reference potential. This is achieved by the solution described above via the corresponding potential voltage limit value and the potential distribution control circuit, which is correspondingly controlled by the processing unit, to prevent the potential voltage limit value from being exceeded.

Safety objective II: Compliance with a maximum insulation design in a high-voltage system with a lower voltage design when connecting two high-voltage systems via a galvanically coupled voltage converter. This applies in particular to vehicle status III, ie the charging of the traction battery via the galvanically coupled DC-DC converter at a DC charging station with a charging voltage and a design voltage of its insulation that is smaller than the nominal battery voltage of the traction battery, and vehicle status IV, ie the operation of a high-voltage component with a Design voltage of their insulation, which is smaller than the design voltage of the high-voltage on-board electrical system, via the galvanically coupled DC-DC converter. The high-voltage system with a higher voltage design is the high-voltage system, in particular the high-voltage electrical system, of the vehicle. The high-voltage system with a lower voltage design is the DC charging station in vehicle status III and the high-voltage component in vehicle status IV. If the vehicle, in particular its traction battery, is charged with a higher voltage level, for example 800V, via the galvanically coupled DC-DC converter at a DC charging station in which the insulation design is lower than this voltage level of the vehicle, for example only 400V or 500V (vehicle status III), then should According to this safety objective II, the insulation of the DC charging station will never be overloaded. The same also applies to the operation of the high-voltage component with a lower design voltage of the insulation, for example 500V, compared to the design voltage of the vehicle, for example 800V, via the galvanically coupled DC-DC converter (vehicle status IV). Here, too, according to this safety objective II, the insulation of this high-voltage component should never be overloaded. In addition, it must be ensured, at least if necessary, that the high-voltage potential voltages between the high-voltage potentials relative to the reference potential do not undergo a sign reversal, in particular during operation of the vehicle and the DC charging station or during operation of the vehicle and the high-voltage component.

Safety objective III: Compatibility with the insulation monitor in the vehicle and/or in the DC charging station. The insulation monitor in the vehicle or in the DC charging station determines the insulation resistance by recharging the high-voltage potential distribution by a certain, in particular predetermined, amount. On the one hand, the voltage swing required for this must not lead to an exceedance of the safety target I (maximum energy content in Y capacities) and the safety target II (maximum voltage of the insulation not exceeded), but on the other hand, this voltage swing must still be sufficiently high so that the insulation monitor is sufficient can determine the exact calculation result.

It is therefore provided in particular that the potential voltage limit value for the respective vehicle status is predetermined or can be determined by the processing unit as a function of a total capacity of all Y-capacities active in this vehicle status.

In vehicle condition I, i.e. H. When the vehicle is driving, the insulation monitor in the vehicle is active. The vehicle is not connected to a DC charging station. This means that only the Y capacities in the vehicle are active. Their total capacity is known and is therefore used to determine or specify the potential voltage limit value. This potential voltage limit, i.e. H. the limit value of the maximum high-voltage potential voltages to the reference potential can thus be calculated in order to comply with the safety objective I, for example a potential voltage limit value of 600V, i.e. H. a maximum positive high-voltage potential voltage from the positive high-voltage potential to the reference potential of 600V and a maximum negative high-voltage potential voltage from the negative high-voltage potential to the reference potential of -600V. The insulation monitor causes a cyclical shift in the high-voltage potentials. The potential distribution control circuit, which is appropriately controlled by the processing unit, limits this cyclic potential shift when the potential voltage limit value is reached, i.e. H. the maximum high-voltage potential voltages.

In particular, it is provided that the total capacity in vehicle status II or III can be determined by the processing unit from the sum of the Y capacities of the high-voltage vehicle electrical system and an estimated Y total capacity value of the DC charging station or can be measured using at least one metrological device.

In vehicle state II, ie charging the traction battery at a DC charging station with a charging voltage that is at least as large as a nominal battery voltage of the traction battery of, for example, 800V, there is a connection of the vehicle and thus of its high-voltage electrical system to a DC charging station with the same or higher charging voltage, for example with a charging voltage of 1000V. The insulation monitor in the vehicle or in the DC charging station is active and monitors the vehicle and the DC charging station. The total capacity of all active Y capacities, ie of the DC charging station and vehicle, is not exactly known at the beginning of the charging process, since the Y capacities of the DC current charging station are not known, but can be estimated, for example, from the sum of the Y capacities of the vehicle and an additionally assumed Y total capacity value for the DC charging station, for example a maximum normatively permissible capacity of the DC charging station of, for example, 500nF per high-voltage potential. Alternatively, the total capacity is determined using measurements. Based on the total capacity determined in the manner described, the potential voltage limit value, ie the limit value of the maximum high-voltage potential voltages to the reference potential, is calculated in order to comply with the safety objective I, for example a potential voltage limit value of 550V, ie a maximum positive high-voltage potential voltage from the positive high-voltage potential to the reference potential of 550V and a maximum negative high-voltage potential voltage from the negative high-voltage potential to the reference potential of -550V. The insulation monitor causes a cyclical shift in the high-voltage potentials. The potential distribution control circuit, which is appropriately controlled by the processing unit, limits this cyclic potential shift when the potential voltage limit value, ie the maximum high-voltage potential voltages, is reached.

In vehicle condition III, i.e. H. Charging the traction battery via the galvanically coupled DC-DC converter at a DC charging station with a charging voltage and a design voltage of its insulation that is smaller than the nominal battery voltage of the traction battery, there is a connection of the vehicle and thus of its high-voltage electrical system to such a DC charging station with a charging voltage of, for example, 500V. The traction battery is therefore charged via the galvanically coupled DC-DC converter. The insulation monitor in the vehicle or in the DC charging station is active and monitors the vehicle and the DC charging station. The total capacity of all active Y capacities, i.e. H. of DC charging station and vehicle, is not exactly known at the beginning of the charging process because the Y capacities of the DC charging station are not known, but can be estimated, for example, from the sum of the Y capacities of the vehicle and an additionally assumed Y total capacity value for the DC charging station, for example, a maximum normatively permissible capacity of the DC charging station of, for example, 500nF per high-voltage potential. Alternatively, the total capacity is determined using measurements. Based on the total capacity determined in the manner described, the potential voltage limit, i.e. H. the limit value of the maximum high-voltage potential voltages to the reference potential, calculated in order to comply with the safety objective I, for example a potential voltage limit value of 550V, i.e. H. a maximum positive high-voltage potential voltage from the positive high-voltage potential to the reference potential of 550V and a maximum negative high-voltage potential voltage from the negative high-voltage potential to the reference potential of -550V. The insulation monitor causes a cyclical shift in the high-voltage potentials. The potential distribution control circuit, which is appropriately controlled by the processing unit, limits this cyclic potential shift when the potential voltage limit value is reached, i.e. H. the maximum high-voltage potential voltages.

In addition, security objective II is also taken into account here, i.e. H. Overloading of the insulation of the DC charging station should be avoided. In order to comply with safety objective II, if this DC charging station has a maximum insulation design, i.e. H. a design voltage of its insulation, for example 500V, is assumed, a potential voltage limit of 500V is determined or specified on the connection side to the DC charging station, i.e. H. a maximum positive high-voltage potential voltage from the positive high-voltage potential to the reference potential of 500V and a maximum negative high-voltage potential voltage from the negative high-voltage potential to the reference potential of -500V. The insulation monitor causes a cyclical shift in the high-voltage potentials. The potential distribution control circuit, which is appropriately controlled by the processing unit, limits this cyclic potential shift when the potential voltage limit value is reached, i.e. H. the maximum high-voltage potential voltages.

In this vehicle state III, it must also be ensured in accordance with safety objective II that the high-voltage potential voltages between the high-voltage potentials do not undergo a sign reversal in relation to the reference potential. This means that it must be avoided that the voltage from the positive high-voltage potential to the reference potential becomes negative and/or the voltage from the negative high-voltage potential to the reference potential becomes positive. The potential voltage limit, i.e. H. the limit value of the maximum high-voltage potential voltages to the reference potential is thus determined or specified in such a way that no sign reversal takes place. The potential distribution control circuit, which is appropriately controlled by the processing unit, limits the potential shift when this potential voltage limit value is reached. The high-voltage potential distribution is thereby controlled by means of the potential distribution control circuit in such a way that no sign reversal occurs.

It is therefore provided in possible embodiments of the vehicle and the method that the potential voltage limit value is such is or is specified or can be determined by the processing unit that a sign reversal of the high-voltage potential voltages is prevented.

In a possible embodiment, the potential distribution control circuit has a controllable current source between the positive high-voltage potential and the reference potential and/or a controllable current source between the negative high-voltage potential and the reference potential. The potential distribution control circuit controlled by the processing unit intervenes to prevent the potential voltage limit value from being exceeded by controlling one of the two high-voltage potential voltages to the reference potential to the previously determined or predetermined potential voltage limit value. A maximum current for adjusting the high-voltage potential distribution is, for example, 10mA. If only one controllable power source is provided, i.e. H. between the positive high-voltage potential and the reference potential or between the negative high-voltage potential and the reference potential, this drives positive and negative currents, i.e. H. she is trained and equipped accordingly. Alternatively, two controllable power sources are used, i.e. H. one controllable current source per high-voltage potential, then each with only one possible current direction. The controllable power source or the respective controllable power source can be galvanically isolated or coupled.

In a possible embodiment, the potential distribution control circuit has a controllable voltage source between the positive high-voltage potential and the reference potential and/or a controllable voltage source between the negative high-voltage potential and the reference potential. The potential distribution control circuit controlled by the processing unit intervenes to prevent the potential voltage limit value from being exceeded by controlling one of the two high-voltage potential voltages to the reference potential to the previously determined or predetermined potential voltage limit value. If only one controllable voltage source is used, i.e. H. between the positive high-voltage potential and the reference potential or between the negative high-voltage potential and the reference potential, then this voltage source only controls a high-voltage potential to the reference potential. Alternatively, two controllable voltage sources are used, i.e. H. a controllable voltage source between the positive high-voltage potential and the reference potential and a controllable voltage source between the negative high-voltage potential and the reference potential. The voltage source or the respective voltage source can be galvanically isolated or coupled.

In a possible embodiment, the potential distribution control circuit has a controllable resistance between the positive high-voltage potential and the reference potential and a controllable resistance between the negative high-voltage potential and the reference potential. The potential distribution control circuit controlled by the processing unit intervenes to prevent the potential voltage limit value from being exceeded by controlling one of the two high-voltage potential voltages to the reference potential to the previously determined or predetermined potential voltage limit value. The respective controllable resistance consists, for example, of a fixed resistor with a minimum resistance value of, for example, 100 Ohm/V and/or a controllable component. The control can take place, for example, via a clocking operation of a low resistance or via the operation of a semiconductor in the linear range.

For the vehicle described, in particular its high-voltage electrical system, and the method described, it is in particular provided that the potential distribution control circuit is inactive as long as the potential voltage limit is not reached, i.e. H. as long as the maximum positive high-voltage potential voltage from the positive high-voltage potential to the reference potential and the maximum negative high-voltage potential voltage from the negative high-voltage potential to the reference potential are not reached. The insulation monitor, in particular in the vehicle, or the insulation monitor in the DC charging station, if the vehicle is coupled to it for charging the traction battery, can thus shift the high-voltage potentials uninfluenced by the potential distribution control circuit and calculate the insulation value in accordance with its functionality described above. If the potential voltage limit, i.e. H. one of the maximum high-voltage potential voltages is reached, then this is determined by the processing unit, which evaluates the voltage measuring devices, and the potential distribution control circuit is then activated, which is then limited accordingly to the potential voltage limit value, i.e. H. prevents it from being exceeded. This ensures in particular that security objective III is achieved, i.e. H. the compatibility with the insulation monitor in the vehicle and/or in the DC charging station.

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

• 1 schematisch eine Ausführungsform eines Hochvoltbordnetzes eines Fahrzeugs,
• 2 schematisch eine weitere Ausführungsform eines Hochvoltbordnetzes eines Fahrzeugs, und
• 3 schematisch eine weitere Ausführungsform eines Hochvoltbordnetzes eines Fahrzeugs.

Show:

• 1 schematically an embodiment of a high-voltage electrical system of a vehicle,
• 2 schematically another embodiment of a high-voltage electrical system of a vehicle, and
• 3 schematically another embodiment of a high-voltage electrical system of a vehicle.

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

The 1 until 3 show exemplary embodiments of a vehicle 1 with a high-voltage electrical system 2.

The high-voltage electrical system 2 includes a traction battery 3, a positive high-voltage potential HV+ coupled to the traction battery 3, a negative high-voltage potential HV- coupled to the traction battery 3 and a reference potential M, which is designed in particular as a ground potential.

Furthermore, the high-voltage electrical system 2 includes an insulation resistance Riso+ between the positive high-voltage potential HV+ and the reference potential M and an insulation resistance Riso- between the negative high-voltage potential HV- and the reference potential M.

In addition, the high-voltage electrical system 2 includes a Y-capacitance Cy+ between the positive high-voltage potential HV+ and the reference potential M and a Y-capacitance Cy- between the negative high-voltage potential HV- and the reference potential M.

Furthermore, the high-voltage electrical system 2 includes an insulation monitor 4 electrically coupled to the positive high-voltage potential HV+, the negative high-voltage potential HV- and the reference potential M.

In addition, the high-voltage electrical system 2 includes a voltage measuring device V1 between the positive high-voltage potential HV+ and the reference potential M for measuring a positive high-voltage potential voltage from the positive high-voltage potential HV+ to the reference potential M and a voltage measuring device V2 between the negative high-voltage potential HV- and the reference potential M for measuring a negative high-voltage potential voltage from the negative one High-voltage potential HV- to reference potential M.

Furthermore, the high-voltage electrical system 2 includes a potential distribution control circuit 5 and a processing unit 6, which is coupled to the voltage measuring devices V1, V2 for evaluating the measured high-voltage potential voltages and to the potential distribution control circuit 5 for controlling them.

The processing unit 6 is designed and set up to determine a currently existing vehicle status and to control the potential distribution control circuit 5 to prevent a potential voltage limit value for the vehicle status from being exceeded, whereby a potential voltage limit value is predetermined for several vehicle statuses or can be determined by the processing unit 6. The respective potential voltage limit value is an absolute amount. It therefore applies to both the positive high-voltage potential voltage, here correspondingly with a positive sign, and for the negative high-voltage potential voltage, here correspondingly with a negative sign.

This solution thus enables a vehicle condition-dependent limitation of the high-voltage potential voltages to the reference potential M to the respective potential voltage limit value. This ensures in particular compliance with normative upper limits in the Y capacities Cy+, Cy- stored energy/charge. In particular, due to an increasing use of higher voltage levels, for example 800V, in vehicles 1, the stored energy/charge increases in the Y capacitances Cy+, Cy-, which are designed in particular as filter capacitors or include them. Compliance with the normative upper limits therefore represents a challenge. When charging at a DC charging station, Y capacities in the DC charging station are also electrically connected in parallel to the Y capacities Cy+, Cy- of vehicle 1. This leads to a further increase in stored energy/charge.

• - Fahrzeugstatus I: Fahrbetrieb, und/oder
• - Fahrzeugstatus II: Laden der Traktionsbatterie 3 an einer Gleichstromladestation mit einer Ladespannung, die mindestens so groß ist wie eine Batterienennspannung der Traktionsbatterie 3, und/oder
• - Fahrzeugstatus III: Laden der Traktionsbatterie 3 über einen galvanisch gekoppelten Gleichspannungswandler an einer Gleichstromladestation mit einer Ladespannung und einer Auslegungsspannung ihrer Isolation, die kleiner ist als die Batterienennspannung der Traktionsbatterie 3, und/oder
• - Fahrzeugstatus IV: Betrieb einer Hochvoltkomponente mit einer Auslegungsspannung ihrer Isolation, die kleiner ist als eine Auslegungsspannung des Hochvoltbordnetzes 2, über einen galvanisch gekoppelten Gleichspannungswandler.

In the solution described here, it is in particular provided that a potential voltage limit value is specified or can be determined by the processing unit 6 for each

• - Vehicle status I: driving, and/or
• - Vehicle status II: Charging the traction battery 3 at a DC charging station with a charging voltage that is at least as large as a nominal battery voltage of the traction battery 3, and / or
• - Vehicle status III: Charging the traction battery 3 via a galvanically coupled DC-DC converter at a DC charging station with a charging voltage and a design voltage of its insulation that is smaller than the nominal battery voltage of the traction battery 3, and / or
• - Vehicle status IV: Operation of a high-voltage component with a design voltage of its insulation that is smaller than a design voltage of the high-voltage vehicle electrical system 2 a galvanically coupled DC-DC converter.

These vehicle statuses each require their own potential voltage limit value, in particular due to a different total capacity of the Y-capacities Cy+, Cy- active in the respective vehicle status, which, in particular in vehicle status II and III, also depends on the Y-capacities of the respective DC charging station, by means of which the traction battery 3 is charged in each case and can therefore differ between different DC charging stations.

• Sicherheitsziel I: Reduzierung der maximalen Energie in den Y-Kapazitäten Cy+, Cy-. Bei Fahrzeugen 1 mit höheren Auslegungsspannungen des Hochvoltbordnetzes 2, d. h.
• Betriebsspannungen, beispielsweise 850V oder höher, steigt der Energieinhalt der Y-Kapazitäten Cy+, Cy- quadratisch mit der Gleichspannung an. Der in den Y-Kapazitäten Cy+, Cy- gespeicherte Ladungsinhalt steigt proportional mit der Gleichspannung an. Bei den Y-Kapazitäten Cy+, Cy- handelt es sich teilweise um real existierende Bauteile in Form von EMV-Filter-Komponenten (EMV = Elektromagnetische Verträglichkeit) und teilweise um so genannte Streukapazitäten. Die maximal gespeicherte Energie und die maximale Ladungsmenge sind normativ begrenzt, um einen gefährlichen Stromschlag als Folge eines einfachen Isolationsfehlers zu verhindern.
• Beispielhafte Normen hierzu sind die ISO 17409 und die J1772. Als maximale Energie in den Y-Kapazitäten Cy+, Cy- wird eine komplett unsymmetrische Hochvoltpotentialverteilung betrachtet. Dabei liegt zwischen einem Hochvoltpotential HV+, HV- und dem Bezugspotential M die volle Batteriespannung der Traktionsbatterie 3 an, während über dem anderen Hochvoltpotential HV-, HV+ und dem Bezugspotential M 0V, d. h. keine Spannung, anliegt. Die in den Y- Kapazitäten Cy+, Cy- gespeicherten Energien, d. h. die Summe der Energien beider Hochvoltpotentiale HV+, HV-, können reduziert werden, indem die Unsymmetrie der Hochvoltpotentiale HV+, HV- bezogen auf das Bezugspotential M eingeschränkt, d. h. begrenzt, wird. Dies wird durch die oben beschriebene Lösung über den entsprechenden Potentialspannungsgrenzwert und die mittels der Verarbeitungseinheit 6 entsprechend angesteuerte Potentialverteilungssteuerungsschaltung 5 zum Verhindern des Überschreitens des Potentialspannungsgrenzwertes erreicht.

In the solution described here, it is in particular provided that the potential voltage limit value for the respective vehicle status is predefined or can be determined by the processing unit 6 depending on at least one safety goal to be met. The following safety objectives are particularly specified:

• Safety goal I: Reduction of the maximum energy in the Y capacitances Cy+, Cy-. For vehicles 1 with higher design voltages of the high-voltage electrical system 2, ie
• Operating voltages, for example 850V or higher, the energy content of the Y capacitances Cy+, Cy- increases squarely with the DC voltage. The charge content stored in the Y capacitances Cy+, Cy- increases proportionally with the DC voltage. The Y capacitances Cy+, Cy- are partly actually existing components in the form of EMC filter components (EMC = electromagnetic compatibility) and partly so-called stray capacitances. The maximum stored energy and the maximum amount of charge are normatively limited to prevent dangerous electric shock as a result of a simple insulation fault.
• Example standards for this are ISO 17409 and J1772. A completely asymmetrical high-voltage potential distribution is considered the maximum energy in the Y capacitances Cy+, Cy-. The full battery voltage of the traction battery 3 is present between a high-voltage potential HV+, HV- and the reference potential M, while 0V, ie no voltage, is present across the other high-voltage potential HV-, HV+ and the reference potential M. The energies stored in the Y capacitances Cy+, Cy-, ie the sum of the energies of both high-voltage potentials HV+, HV-, can be reduced by restricting, ie limiting, the asymmetry of the high-voltage potentials HV+, HV- in relation to the reference potential M. This is achieved by the solution described above via the corresponding potential voltage limit value and the potential distribution control circuit 5, which is correspondingly controlled by means of the processing unit 6, to prevent the potential voltage limit value from being exceeded.

Safety objective II: Compliance with a maximum insulation design in a high-voltage system with a lower voltage design when connecting two high-voltage systems via a galvanically coupled voltage converter. This particularly applies to vehicle status III, i.e. H. charging the traction battery 3 via the galvanically coupled DC-DC converter at a DC charging station with a charging voltage and a design voltage of its insulation that is smaller than the nominal battery voltage of the traction battery 3, and the vehicle status IV, i.e. H. the operation of a high-voltage component with a design voltage of its insulation that is smaller than the design voltage of the high-voltage vehicle electrical system 2 via the galvanically coupled DC-DC converter. The high-voltage system with a higher voltage design is the high-voltage system, in particular high-voltage electrical system 2, of vehicle 1. The high-voltage system with a lower voltage design is the DC charging station in vehicle status III and the high-voltage component in vehicle status IV.

If the vehicle 1, in particular its traction battery 3, is charged with a higher voltage level, for example 800V, via the galvanically coupled DC-DC converter at a DC charging station in which the insulation design is lower than this voltage level of the vehicle 1, for example only 400V or 500V (vehicle status III) , then according to this safety objective II, an overload of the insulation of the DC charging station should never occur. The same also applies to the operation of the high-voltage component with a lower design voltage of the insulation, for example 500V, compared to the design voltage of the vehicle 1, for example 800V, via the galvanically coupled DC-DC converter (vehicle status IV). Here, too, according to this safety objective II, the insulation of this high-voltage component should never be overloaded. In addition, at least if necessary, it must be ensured that the high-voltage potential voltages between the high-voltage potentials HV+, HV-, based on the reference potential M, do not undergo a sign reversal, in particular when the vehicle 1 and the DC charging station are in operation or when the vehicle 1 and the high-voltage component are in operation.

Safety objective III: Compatibility with the insulation monitor 4 in vehicle 1 and/or in the DC charging station. The insulation monitor 4 in the vehicle 1 or in the DC charging station determines the insulation resistance by increasing the high-voltage potential distribution by a certain amount, in particular predetermined amount is transferred. On the one hand, a voltage swing required for this must not lead to an exceedance of the safety target I (maximum energy content in Y capacities Cy+, Cy-) and the safety target II (maximum voltage of the insulation not exceeded), but on the other hand, this voltage swing must still be sufficiently high the insulation monitor 4 can determine a sufficiently accurate calculation result.

In the solution described here, it is therefore particularly provided that the potential voltage limit value for the respective vehicle status is predetermined or can be determined by the processing unit 6 as a function of a total capacity of all Y capacitances Cy+, Cy- active in this vehicle status.

In vehicle condition I, i.e. H. When vehicle 1 is driving, the insulation monitor 4 in vehicle 1 is active. There is no connection between vehicle 1 and a DC charging station. Only the Y capacitances Cy+, Cy- in vehicle 1 are active. Their total capacity is known and is therefore specified for determining or specifying the potential voltage limit value. This potential voltage limit, i.e. H. the limit value of the maximum high-voltage potential voltages to the reference potential M can thus be calculated in order to comply with the safety objective I, for example a potential voltage limit value of 600V, i.e. H. a maximum positive high-voltage potential voltage from the positive high-voltage potential HV+ to the reference potential M of 600V and a maximum negative high-voltage potential voltage from the negative high-voltage potential HV- to the reference potential M of -600V. The insulation monitor 4 causes a cyclical shift in the high-voltage potentials HV+, HV-. The potential distribution control circuit 5, which is correspondingly controlled by the processing unit 6, limits this cyclic potential shift when the potential voltage limit value is reached, i.e. H. the maximum high-voltage potential voltages.

In the solution described here, it is in particular provided that the total capacity in vehicle status II or III can be determined by the processing unit 6 from the sum of the Y capacities Cy+, Cy- of the high-voltage vehicle electrical system 2 and an estimated Y total capacity value of the DC charging station or by means of at least one measurement Facility is measurable.

In vehicle condition II, i.e. H. Charging the traction battery 3 at a DC charging station with a charging voltage that is at least as large as a nominal battery voltage of the traction battery 3 of, for example, 800V, there is a connection of the vehicle 1 and thus of its high-voltage electrical system 2 to a DC charging station with the same or higher charging voltage, for example with a Charging voltage of 1000V. The insulation monitor 4 in vehicle 1 or in the DC charging station is active and monitors vehicle 1 and the DC charging station. The total capacity of all active Y capacities Cy+, Cy-, i.e. H. of DC charging station and vehicle 1, is not exactly known at the beginning of the charging process because the Y capacities of the DC charging station are not known, but can be estimated, for example, from the sum of the Y capacities Cy+, Cy- of vehicle 1 and an additional assumed Y -Total capacity value for the DC charging station, for example a maximum normatively permissible capacity of the DC charging station of, for example, 500nF per high-voltage potential. Alternatively, the total capacity is determined using measurements.

Based on the total capacity determined in the manner described, the potential voltage limit, i.e. H. the limit value of the maximum high-voltage potential voltages to the reference potential M, calculated in order to comply with the safety objective I, for example a potential voltage limit value of 550V, i.e. H. a maximum positive high-voltage potential voltage from the positive high-voltage potential HV+ to the reference potential M of 550V and a maximum negative high-voltage potential voltage from the negative high-voltage potential HV- to the reference potential M of -550V. The insulation monitor 4 causes a cyclical shift in the high-voltage potentials HV+, HV-. The potential distribution control circuit 5, which is correspondingly controlled by the processing unit 6, limits this cyclic potential shift when the potential voltage limit value is reached, i.e. H. the maximum high-voltage potential voltages.

In vehicle state III, ie charging the traction battery 3 via the galvanically coupled DC-DC converter at a DC charging station with a charging voltage and a design voltage of its insulation that is smaller than the nominal battery voltage of the traction battery 3, there is a connection of the vehicle 1 and thus of its high-voltage electrical system 2 to one such a DC charging station with a charging voltage of, for example, 500V. The traction battery 3 is therefore charged via the galvanically coupled DC-DC converter. The insulation monitor 4 in vehicle 1 or in the DC charging station is active and monitors vehicle 1 and the DC charging station. The total capacity of all active Y-capacities Cy+, Cy-, ie of the DC charging station and vehicle 1, is not exactly known at the start of the charging process, since the Y-capacities of the DC charging station are not known, but can be estimated, for example are the sum of the Y-capacities Cy+, Cy- of the vehicle 1 and an additionally assumed Y-total capacity value for the DC charging station, for example a maximum normatively permissible capacity of the DC charging station of, for example, 500nF per high-voltage potential. Alternatively, the total capacity is determined using measurements.

Based on the total capacity determined in the manner described, the potential voltage limit, i.e. H. the limit value of the maximum high-voltage potential voltages to the reference potential M, calculated in order to comply with the safety objective I, for example a potential voltage limit value of 550V, i.e. H. a maximum positive high-voltage potential voltage from the positive high-voltage potential HV+ to the reference potential M of 550V and a maximum negative high-voltage potential voltage from the negative high-voltage potential HV- to the reference potential M of -550V. The insulation monitor 4 causes a cyclical shift in the high-voltage potentials HV+, HV-. The potential distribution control circuit 5, which is correspondingly controlled by the processing unit 6, limits this cyclic potential shift when the potential voltage limit value is reached, i.e. H. the maximum high-voltage potential voltages.

In addition, security objective II is also taken into account here, i.e. H. Overloading of the insulation of the DC charging station should be avoided. In order to comply with safety objective II, if this DC charging station has a maximum insulation design, i.e. H. a design voltage of its insulation, for example 500V, is assumed, a potential voltage limit of 500V is determined or specified on the connection side to the DC charging station, i.e. H. a maximum positive high-voltage potential voltage from the positive high-voltage potential HV+ to the reference potential M of 500V and a maximum negative high-voltage potential voltage from the negative high-voltage potential HV- to the reference potential M of -500V. The insulation monitor 4 causes a cyclical shift in the high-voltage potentials HV+, HV-. The potential distribution control circuit 5, which is correspondingly controlled by the processing unit 6, limits this cyclic potential shift when the potential voltage limit value is reached, i.e. H. the maximum high-voltage potential voltages.

In this vehicle state III, it must also be ensured in accordance with safety objective II that the high-voltage potential voltages between the high-voltage potentials HV+, HV- do not undergo a sign reversal in relation to the reference potential M. This means that it must be avoided that the voltage from the positive high-voltage potential HV+ to the reference potential M becomes negative and/or the voltage from the negative high-voltage potential HV- to the reference potential M becomes positive. The potential voltage limit, i.e. H. the limit value of the maximum high-voltage potential voltages to the reference potential M is thus determined or specified in such a way that no sign reversal takes place. The potential distribution control circuit 5, which is correspondingly controlled by the processing unit 6, limits the potential shift when this potential voltage limit value is reached. The high-voltage potential distribution is thereby controlled by means of the potential distribution control circuit 5 in such a way that no sign reversal occurs.

In the solution described here, it is therefore provided in particular that the potential voltage limit value is or is predetermined or can be determined by the processing unit 6 in such a way that a sign reversal of the high-voltage potential voltages is prevented.

The embodiments according to 1 until 3 differ in the design of the potential distribution control circuit 5. In all embodiments it is provided that the potential distribution is carried out by the processing unit 6 via the evaluation of the high-voltage potential voltages measured by the voltage measuring device V1, V2 from the positive high-voltage potential HV+ to the reference potential M and from the negative high-voltage potential HV- to the reference potential M in particular is permanently recorded. The intervention in a potential shift, in particular caused by the insulation monitor 4 of the vehicle 1 or the DC charging station, only takes place when the previously determined or specified potential voltage limit is reached.

In the embodiment according to 1 The potential distribution control circuit 5 has a controllable current source 7 between the positive high-voltage potential HV+ and the reference potential M, as in 1 shown, and / or a controllable current source between the negative high-voltage potential HV and the reference potential M. The potential distribution control circuit 5 controlled by the processing unit 6 intervenes to prevent the potential voltage limit value from being exceeded by controlling one of the two high-voltage potential voltages to the reference potential M to the previously determined or predetermined potential voltage limit value. A maximum current for adjusting the high-voltage potential distribution is, for example, 10mA. If only one controllable current source 7 is provided, ie between the positive high-voltage potential HV+ and the reference potential M, as shown here, or between the negative high-voltage potential HV- and the reference potential M, this drives positive and negative currents, meaning it is designed and set up accordingly. Alternatively, two controllable current sources 7 are used, ie one controllable current source 7 per high-voltage potential HV+, HV-, then each with only one possible current direction. The controllable power source 7 or the respective controllable power source 7 can be galvanically isolated or coupled.

In the embodiment according to 2 The potential distribution control circuit 5 has a controllable voltage source 8 between the positive high-voltage potential HV+ and the reference potential M, as in 2 shown, and / or a controllable voltage source 8 between the negative high-voltage potential HV and the reference potential M. The potential distribution control circuit 5 controlled by the processing unit 6 intervenes to prevent the potential voltage limit value from being exceeded by controlling one of the two high-voltage potential voltages to the reference potential M to the previously determined or predetermined potential voltage limit value. If only one controllable voltage source 8 is used, ie between the positive high-voltage potential HV+ and the reference potential M, as shown here, or between the negative high-voltage potential HV- and the reference potential M, then this voltage source 8 only controls a high-voltage potential HV+, HV- to the reference potential M. Alternatively, two controllable voltage sources 8 are used, that is, a controllable voltage source 8 between the positive high-voltage potential HV+ and the reference potential M and a controllable voltage source 8 between the negative high-voltage potential HV- and the reference potential M. The controllable voltage source 8 or the respective controllable voltage source 8 can be galvanically isolated or coupled.

In the embodiment according to 3 the potential distribution control circuit 5 has a controllable resistor 9 between the positive high-voltage potential HV+ and the reference potential M and a controllable resistor 9 between the negative high-voltage potential HV- and the reference potential M. The potential distribution control circuit 5 controlled by the processing unit 6 intervenes to prevent the potential voltage limit value from being exceeded by controlling one of the two high-voltage potential voltages to the reference potential M to the previously determined or predetermined potential voltage limit value. The respective controllable resistor 9 consists, for example, of a fixed resistor with a minimum resistance value of, for example, 100 ohms/V and/or a controllable component. The control can take place, for example, via a clocking operation of a low resistance or via the operation of a semiconductor in the linear range.

In the solution described here, it is particularly provided that the potential distribution control circuit 5 is inactive as long as the potential voltage limit is not reached, i.e. H. as long as the maximum positive high-voltage potential voltage from the positive high-voltage potential HV+ to the reference potential M and the maximum negative high-voltage potential voltage from the negative high-voltage potential HV- to the reference potential M is not reached. The insulation monitor 4, in particular in the vehicle 1, or the insulation monitor in the DC charging station, if the vehicle 1 is coupled to it for charging the traction battery 3, can thus shift the high-voltage potentials HV+, HV- without being influenced by the potential distribution control circuit 5 in accordance with its mode of operation described above calculate the insulation value. If the potential voltage limit, i.e. H. one of the maximum high-voltage potential voltages is reached, then this is determined by the processing unit 6, which evaluates the voltage measuring devices V1, V2, and the potential distribution control circuit 5 is then activated, which is then limited accordingly to the potential voltage limit value, i.e. H. prevents it from being exceeded. This ensures in particular that security objective III is achieved, i.e. H. the compatibility with the insulation monitor 4 in the vehicle 1 and/or in the DC charging station.

The solution described allows larger Y capacitances Cy+, Cy- to be installed in the vehicle 1, whereby the filtering options of power electronics of the vehicle 1 can be improved. Furthermore, the solution described makes it possible to prevent overloading of insulation in the DC charging station when charging via a galvanically coupled DC-DC converter. In addition, the solution described makes it possible for the insulation monitor 4 in the vehicle 1 and/or an insulation monitor in the DC charging station to function even when the potential distribution control circuit 5 is active, i.e. H. with active switching to limit the high-voltage potential voltages to the respective potential voltage limit value.

Reference symbol list

1

vehicle

2

High-voltage electrical system

3

Traction battery

4

Isolation monitor

5

Potential distribution control circuit

6

Processing unit

7

controllable power source

8th

controllable voltage source

9

controllable resistance

Cy+

Y capacity

Cy-

Y capacity

HV+

positive high voltage potential

HV

negative high voltage potential

M

reference potential

Riso+

Insulation resistance

riso

Insulation resistance

V1

Voltage measuring device

V2

Voltage measuring device

Claims (7)

Vehicle (1) with a high-voltage electrical system (2), the high-voltage electrical system (2) having: - a traction battery (3), - a positive high-voltage potential (HV+), - a negative high-voltage potential (HV-), - a reference potential (M), - an insulation resistance (Riso+) between the positive high-voltage potential (HV+) and the reference potential (M), - an insulation resistance (Riso-) between the negative high-voltage potential (HV-) and the reference potential (M), - a Y-capacitance (Cy+) between the positive high-voltage potential (HV+) and the reference potential (M), - a Y-capacitance (Cy-) between the negative high-voltage potential (HV-) and the reference potential (M), - one with the positive high-voltage potential (HV+), the negative one High-voltage potential (HV-) and the reference potential (M) electrically coupled insulation monitor (4), - a voltage measuring device (V1) between the positive high-voltage potential (HV+) and the reference potential (M) for measuring a positive high-voltage potential voltage, - a voltage measuring device (V2) between the negative high-voltage potential (HV-) and the reference potential (M) for measuring a negative high-voltage potential voltage, - a potential distribution control circuit (5), and - a processing unit (6) which is connected to the voltage measuring devices (V1, V2) for evaluating the measured high-voltage potential voltages and with the potential distribution control circuit (5) is coupled to control it, the processing unit (6) being designed and set up to - determine a currently existing vehicle status and - control the potential distribution control circuit (5) to prevent a potential voltage limit value for the vehicle status from being exceeded, for several vehicle status, a potential voltage limit value is predetermined or can be determined by the processing unit (6), characterized in that a potential voltage limit value is predetermined or can be determined by the processing unit (6) for a - vehicle status I: driving operation, and - vehicle status II: charging the traction battery ( 3) at a DC charging station with a charging voltage that is at least as large as a nominal battery voltage of the traction battery (3), and - vehicle status III: charging the traction battery (3) via a galvanically coupled DC-DC converter at a DC charging station with a charging voltage and a design voltage of its insulation , which is smaller than the nominal battery voltage of the traction battery (3), and - Vehicle status IV: Operation of a high-voltage component with a design voltage of its insulation that is smaller than a design voltage of the high-voltage vehicle electrical system (2), via a galvanically coupled DC-DC converter. Vehicle (1) after Claim 1 , characterized in that the potential voltage limit value for the respective vehicle status is predetermined depending on at least one safety objective to be met or can be determined by the processing unit (6). Vehicle (1) after Claim 1 or 2 , characterized in that the potential voltage limit value for the respective vehicle status is predetermined or can be determined by the processing unit (6) as a function of a total capacity of all Y capacitances (Cy+, Cy-) active in this vehicle status. Vehicle (1) after Claim 3 , characterized in that the total capacity in vehicle status II or III can be determined by the processing unit (6) from the sum of the Y capacities (Cy+, Cy-) of the high-voltage on-board network (2) and an estimated Y total capacity value of the DC charging station or by means of at least one can be measured using a metrological device. Vehicle (1) according to one of the preceding claims, characterized in that the potential voltage limit value is specified in such a way or it can be determined by the processing unit (6) that a sign reversal of the high-voltage potential voltages is prevented. Vehicle (1) according to one of the preceding claims, characterized in that the potential distribution control circuit (5) - a controllable current source (7) between the positive high-voltage potential (HV+) and the reference potential (M) and / or a controllable current source (7) between the negative high-voltage potential (HV-) and the reference potential (M), or - a controllable voltage source (8) between the positive high-voltage potential (HV+) and the reference potential (M) and / or a controllable voltage source (8) between the negative high-voltage potential (HV -) and the reference potential (M), or - a controllable resistance (9) between the positive high-voltage potential (HV+) and the reference potential (M) and a controllable resistance (9) between the negative high-voltage potential (HV-) and the reference potential ( M). Method for operating a high-voltage on-board electrical system (2) of a vehicle (1) according to one of the preceding claims, characterized in that the processing unit (6) determines the current vehicle status and controls the potential distribution control circuit (5) to prevent the potential voltage limit value for this from being exceeded Vehicle status is specified or is determined by the processing unit (6) before activating the potential distribution control circuit (5).

Images