EP3099523A1

EP3099523A1 - On-board electrical system, and method for operating an on-board electrical system

Info

Publication number: EP3099523A1
Application number: EP15701024.0A
Authority: EP
Inventors: Holger Fink
Original assignee: Robert Bosch GmbH; Samsung SDI Co Ltd
Current assignee: Robert Bosch GmbH; Samsung SDI Co Ltd
Priority date: 2014-01-27
Filing date: 2015-01-23
Publication date: 2016-12-07
Also published as: US10279699B2; CN105934362B; DE102014201351A1; CN105934362A; KR102002082B1; US20160339795A1; WO2015110591A1; KR20160114147A

Abstract

The invention relates to an on-board electrical system (1) for a motor vehicle, wherein the on-board electrical system (1) has a low-voltage electrical subsystem (21) for at least one low-voltage load (29), and has a high-voltage electrical subsystem (20) for at least one high-voltage load (25), and has a starter generator (30), wherein the high-voltage electrical subsystem (20) is connected to the low-voltage electrical subsystem (21) by means of a coupling unit (33), wherein the on-board electrical system (1) has a battery (40) which is designed to generate the high voltage and to feed said high voltage into the high-voltage electrical subsystem (20), and which has at least two battery units (41) having individual voltage taps (42) which are routed to the coupling unit (33). In this case, provision is made for the coupling unit (33) to be designed to provide at least a first and a second operating state, wherein, in the first operating state, the high-voltage electrical subsystem (20) is fed from all of the battery units (41) of the battery (40) and the low-voltage electrical subsystem (21) is fed from one battery unit (41), and, in the second operating state, the high-voltage electrical subsystem (20) is fed from one battery unit (41) and the low-voltage electrical subsystem (21) is fed from at least one battery unit (41). The invention also relates to a method for operating an on-board electrical system (1) of this kind, and also to a motor vehicle comprising an on-board electrical system of this kind.

Description

Description title

The invention relates to a vehicle electrical system for a motor vehicle, and to a motor vehicle having such a vehicle electrical system.

In motor vehicles with an internal combustion engine, an electrical system is provided for supplying the electric starter or starter for the internal combustion engine and other electrical devices of the motor vehicle, which is operated by default with 12 volts. When starting the engine is on the electrical system of a

Starter battery provided a voltage to a starter, soften the

Internal combustion engine starts when, for example, by a corresponding starter signal, a switch is closed. If the internal combustion engine is started, this drives an electric generator, which then generates a voltage of about 12 volts and provides it via the electrical system to the various electrical consumers in the vehicle. The electric generator also charges the starter battery charged by the starting process. If the battery is charged via the electrical system, the actual voltage may also be above the rated voltage, eg. B. at 14 V or at 14.4 V. The electrical system with 12 V, or 14 V voltage is referred to in the present disclosure as a low-voltage electrical system.

It is known in electric and hybrid vehicles another electrical system with a

Rated voltage of 48 V to use, which is referred to in the context of the invention as a high voltage electrical system.

Disclosure of the invention

The invention provides a vehicle electrical system for a motor vehicle, wherein the electrical system is a low-voltage subnet for at least one low-voltage consumer and a High voltage subnet for at least one high voltage consumer and a starter generator, wherein the high voltage subnet is connected to the low voltage subnet via a coupling unit which is adapted to take the high voltage subnet power and supply the low voltage subnet, the

High voltage subnet having a battery which is adapted to generate the high voltage and deliver it to the high voltage subnet, and the at least two

Battery units having Einzelspannungsabgriffen which are guided to the coupling unit, wherein the coupling unit is adapted to provide at least a first and a second operating state, wherein in the first operating state

High voltage subnet is fed from all battery units of the battery and the low voltage subnet is fed from a battery unit and in the second

Operating state, the high voltage subnet is powered from a battery unit and the low voltage subnet is powered from at least one battery unit. The invention has the advantage that electrical low-voltage consumers can be operated by the low voltage sub-network, the low on a first

Voltage are designed, and for high-voltage consumers, the high-voltage sub-network is ready, i. the sub-board network with a relation to the first voltage increased voltage. The supply of the low voltage subnetwork is the charging and

Discharge processes in the high-voltage sub-network superimposed. The

Low voltage subnetwork supply via the high voltage subnetwork takes place unidirectionally, d. H. The coupling unit preferably provides the energy transfer only in one direction. The electrical system can be used both in stationary applications, e.g. in wind turbines, as well as in vehicles, e.g. in hybrid and electric vehicles.

In particular, the electrical system can be used in vehicles that have start-stop systems. The presented system, d. H. the electrical system and an associated control unit,

for example, a battery management system, is particularly suitable for use in vehicles having a 48 volt generator and a 14 volt starter, the 14 volt starter is preferably designed for start / stop systems. The system presented is particularly suitable for use in vehicles that have a boost recuperation system (BRS). Boost recuperation systems (BRS) generate electrical energy during braking, downhill or sail operation to supply the electrical consumers. The BRS increases the efficiency of the system so that fuel can be saved or emissions can be reduced. The battery in the high voltage subnetwork can be the

Assist combustion engine, which is referred to as boost, or even be used at low speeds for short distances even for purely electric driving, e.g. with an electric parking and Ausparken.

The terms "battery" and "battery unit" are used in the present description, adapted to common usage, used for accumulator or Akkumulatoreinheit. The battery includes one or more battery packs that include a battery cell

Battery Module, a module string or a battery pack can denote. The

Battery cells are preferably spatially combined and interconnected circuitry, for example, connected in series or parallel to modules. Several modules can form so-called battery direct converters (BDCs) and several battery direct converters form a battery direct inverter (BDI). Advantageous developments and improvements of the subject matter specified in the independent claim are possible by the measures listed in the dependent claims.

So it is advantageous if the selectively switchable battery units each for

Provision of low voltage are designed. The battery units can thus be alternately claimed to provide the low voltage, z. B. to support a start-stop system, resulting in an increased life of the battery unit.

According to a preferred embodiment, the coupling unit has at least one reverse-blocking switch. Preferably, the reverse-blocking switch for connecting and disconnecting a selectively switchable battery unit for

Low voltage subnet. These switches have the property that in the state "on" they allow a flow of current in one direction only and in the state "off" one

Reverse voltage both polarity can accommodate. When connecting a battery unit to the low-voltage subnetwork, at least one reverse-blocking switch, more preferably two reverse-blocking switch, is preferably actuated. When switching off a battery unit to the low-voltage subnetwork, at least one reverse-blocking-capable switch, particularly preferably two reverse-blocking-capable switches, is likewise preferably actuated.

According to a preferred embodiment, the coupling unit has at least one reverse-blocking switch. The forward blocking switches are preferably suitable for the series connection of the selectively switchable battery units. It is preferably provided that when separating the line between two battery units, at least one reverse-blocking switch is actuated. Likewise, it is preferably provided that during the connection of the line between the battery units, at least one reverse-blocking switch is actuated. According to a preferred embodiment, the coupling unit is adapted to switch at least two battery units with respect to the low voltage subnet to each other in parallel. Particularly preferably, in the second operating state, at least two, preferably all battery units are connected in parallel with respect to the low-voltage subnetwork. This makes it possible that, in the case of deviating states of charge of the two battery units, a supply of the low-voltage subnetwork from that

Battery unit takes place, which has the higher state of charge or provides the higher voltage. For the same or similar states of charge of the battery units, the low-voltage subnet is supplied from both battery units. According to a preferred embodiment, the coupling unit is adapted to serially connect at least two battery units with respect to the high voltage subnetwork, i. to connect with each other in series. Particularly preferably, in the first operating state, at least two battery units are connected in series with respect to the high-voltage subnetwork. In addition, it can be provided that the low-voltage subnetwork at least one

Condenser has. The capacitor is preferably configured to stabilize the low voltage when changing the connected battery unit. The capacitor is also preferably also suitable as an energy store, which is set up to generate the low voltage at least in the short term and to feed it into the low voltage subnet. The voltage dip in the low-voltage subnetwork can be further advantageously reduced if the switchover occurs at such times when the on-board electrical system current is as low as possible. This can be done, for example, by evaluating a signal for the on-board electrical system current and dependent control of the switch of the coupling unit. In addition, syncing with a

Consumer management system to provide high voltage consumers, such.

Switch off heating systems for a short time without sacrificing comfort, in order to enable switching of the battery units without significant voltage drop.

Preferably, the coupling unit is adapted to provide at least one further operating state, wherein in the further operating state, the high voltage subnet is fed from several, in particular two, three or four battery units and the low voltage subnet is fed from several, in particular two, three or four parallel battery units.

The electrical system preferably has a control unit for controlling the coupling unit

Circuit of the battery units. The control unit may for example be assigned to a battery management system associated with the battery, which comprises, for example, further units which are set up, measuring data on temperatures, supplied voltages, discharged currents and charge states of the battery or the

To detect and process battery units, for example, to make statements about the health of the battery. The control unit for controlling the

Coupling unit can have a computer program that executes one of the methods according to the invention.

According to the invention, a motor vehicle is also specified with an internal combustion engine and one of the vehicle electrical systems described above. In a method according to the invention for operating one of the previously described

Bordnetze the control of the coupling unit for setting the first or second operating state in response to an operating phase of the motor vehicle.

A first operating phase can be a parked vehicle or parking vehicle, a second operating phase a motor vehicle start, a third operating phase a start Stop operation of the motor vehicle and / or a fourth phase of operation a driving operation of the motor vehicle.

Preferably, the second operating state in the first operating phase, d. H. set when the vehicle or parked vehicle.

Preferably, a series connection of several, preferably all battery units takes place with respect to the high-voltage sub-network in the second operating phase. The second operating phase may in particular be a starting state of a motor vehicle, for example also a cold start state of a motor vehicle, the latter being defined by the passage of a defined period of time, for example after the lapse of 10 min, 20 min, 1 h, 2 h, 12 h or 24 H.

Preferably, a series connection of several, preferably all battery units with respect to the high-voltage sub-network in the fourth operating phase, d. H. when driving the motor vehicle.

The third operating phase preferably comprises a start operating state and a

Stop mode. In the start operating state, the settings are preferably selected according to the settings in the second operating phase, and in the

Stop mode the settings according to the settings at the first

Operating phase.

Preferably, that battery unit is used to supply the low-voltage subnetwork, which has the highest state of charge at a given time.

In particular, it is also preferred that in the first operating state, the supply of the low voltage subnet is made from that battery unit which has the highest

Charge state has. Considering an optimized operating strategy for the electrical system with the illustrated series connection of the battery units, the following considerations are made. It is assumed that in uniformly aged cells, the internal resistance and the capacity of the cells at the same reference conditions, ie. H. substantially the same temperature and the same state of charge, are approximately equal.

The maximum achievable power is limited by uniformly aged cells by that cell with the lowest charge state. The maximum removable energy is limited by evenly charged cells by the cell with the lowest state of charge. The maximum allowable load performance is limited by the cell with the highest state of charge for evenly aged cells.

The maximum deliverable energy is limited by evenly aged cells by the cell with the highest state of charge.

Since the battery system in a boost recuperation system should be able to store as much energy as possible during a braking process, and at the same time should be able to support a boost process as well as possible, this can be the reason for this

Be derived requirement that the battery units and the cells therein should all have the same state of charge as possible in order to meet the requirements as well as possible.

In addition to the requirements for the high-voltage subnetwork, the system also has requirements for starting operations in the low-voltage subnetwork. In order for these requirements to be met as well as possible by means of a combination of the high-performance energy store and the battery, it is preferred to use that battery unit to supply the low-voltage subnetwork which has the highest charge state at a given time. The requirements for the selection of the switching states of the coupling unit can be met with the following operating strategy: The supply of the low voltage subnet always takes place from that battery unit, which currently has the highest state of charge. Since the supply of the low-voltage subnetwork is superimposed on the charging and discharging processes in the high-voltage subnetwork and the low-voltage sub-network power supply takes place unidirectionally, this selection rule ensures that the

Battery unit with the highest state of charge is discharged faster or is charged slower than the other battery units. This has a symmetrization of

Charge states of the battery units result. So that a very fast change from one battery unit to the next does not occur with the same state of charge of the battery units, a threshold value for the difference ASOCumschait of the charge states is introduced, eg a difference ASOCumschait with a defined value between 0.5% and 20%, preferably between 1% and 5%, more preferably about 2%, which must be exceeded, so that the supply of the

Low voltage subnet from a battery unit to that battery unit changes, which has a correspondingly higher state of charge than the currently used to supply the low voltage subnet battery unit. The switchover in the supply is always on that battery unit, which currently has the highest state of charge, and the switching takes place when the current supply of the

Low voltage sub-network through-connected battery unit has a state of charge, which is lower by at least ASOCumschait than the state of charge of that battery unit with the highest state of charge. Advantages of the invention

The invention provides a low-cost vehicle electrical system with a lithium-ion battery system for vehicles, which has a high voltage subnet, a low voltage subnet and a boost recuperation system with unidirectional supply of the low voltage subnet. This can be compared to known systems a potential separating

DC-DC converters (DC / DC converters) are eliminated, as well as the lead-acid battery.

In addition, no separate starter in the low voltage subnet is needed. The system is therefore characterized by a reduced volume and by a lower weight compared to currently under development BRS systems. The Boost recuperation system can also store significantly more energy when properly designed compared to currently under development BRS systems and thereby recover more electrical energy in the system during long braking or downhill driving.

The provision according to the invention for the selection of the switching states of the coupling unit has the effect that the battery can perform necessary tasks in an optimized manner in different operating phases of the vehicle electrical system. In particular, the supply of the

Low voltage subnet ensured. The supply takes place as interruption free as possible, d. H. as possible without voltage dips. Should while

Switching phases of the coupling unit in the short term, the uninterruptible supply of the low voltage subnetwork not be possible, the voltage drop in Low voltage subnet nevertheless limited to tolerable values. In addition, the battery provides sufficient electrical energy even with longer downtime. The battery can supply high-voltage consumers even during stop phases during start-stop operation.

In addition, the supply of the high voltage subnet is ensured, d. H. The battery provides the high-voltage sub-network substantially without interruption for the necessary operating conditions, the electrical energy. With regard to the storage of electrical energy optimization means that as much electrical energy can be recovered in a braking operation and that the battery can be charged with the highest possible performance. With regard to the provision of electrical energy, the optimization means that the battery enables the starting processes by providing electrical energy with the required voltage and power, and that as much electrical energy as possible can be made available for the boost operation.

Brief description of the drawings

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. Show it

FIG. 1 shows a low-voltage on-board network according to the prior art,

Figure 2 shows a vehicle electrical system with a high voltage subnet and a

Low voltage subnetwork and a unidirectional, potential separating

DC converter,

Figure 3 shows a vehicle electrical system with a high voltage subnet and a

Low-voltage subnetwork and a bi-directional, potential-separating DC-DC converter,

Figure 4 shows a vehicle electrical system with a high voltage subnet and a

Low voltage subnet and a unidirectional, galvanic

separating DC-DC converter, FIG. 5 shows a coupling unit in an exemplary operating state,

FIG. 6 shows the coupling unit from FIG. 5 in a further exemplary operating state,

FIG. 7 shows the coupling unit from FIG. 5 in a further exemplary operating state,

FIG. 8 shows the coupling unit from FIG. 5 in a further exemplary operating state,

FIG. 9 reverse and reverse blocking switches;

FIG. 10 Settings of operating states as a function of operating phases,

FIG. 11 shows operating states and their properties in a first operating phase,

FIG. 12 operating states and their properties in a second operating phase,

Figure 13 operating conditions and their properties in a third phase of operation and

Figure 14 operating conditions and their properties in a fourth phase of operation.

FIG. 1 shows a vehicle electrical system 1 according to the prior art. When starting a

Internal combustion engine is provided via the electrical system 1 from a starter battery 10, a voltage to a starter 1 1 available, which (not shown) starts the engine when, for example, by a corresponding starter signal, a switch 12 is closed. If the internal combustion engine is started, this drives an electric generator 13, which then generates a voltage of about 12 volts and provides it via the vehicle electrical system 1 to the various electrical consumers 14 in the vehicle. The electric generator 13 also charges the starter battery 10 charged by the starting process.

FIG. 2 shows a vehicle electrical system 1 with a high-voltage sub-network 20 and a

Low voltage subnet 21 and a unidirectional, potential separating

DC voltage converter 22, which forms a coupling unit between the high-voltage sub-network 20 and the low-voltage sub-network 21. The electrical system 1 can be an electrical system of a Vehicle, in particular a motor vehicle, transport vehicle or forklift to be.

The high-voltage sub-network 20 is, for example, a 48-volt electrical system with a

electric generator 23 which is operable by an internal combustion engine (not shown). The generator 23 is formed in this embodiment, in

Depending on a rotational movement of the engine of the vehicle to generate electrical energy and feed it into the high-voltage sub-network 20. The high voltage sub-network 20 further comprises a battery 24, which may be formed, for example, as a lithium-ion battery and which is adapted to feed the necessary operating voltage in the high-voltage sub-network 20. In the high voltage sub-network 20 are more

Load resistors arranged, which may be formed for example by at least one, preferably by a plurality of electrical high-voltage consumers 25 of the motor vehicle, which are operated with the high voltage.

In the low-voltage sub-network 21, which is arranged on the output side of the DC-DC converter 22, there are a starter 26, which is set to close a switch 27 to start the engine, and an energy storage 28, which is set, the low voltage in the amount of, for example 14th Volt for that

Low voltage subnet 21 to provide. In the low voltage subnet 21 are more

Low-voltage consumers 29 are arranged, which are operated with the low voltage. The energy store 28 includes, for example, galvanic cells, in particular those of a lead-acid battery, which usually has a voltage of 12.8 volts when fully charged (state of charge, SOC = 100%). When the battery is discharged (state of charge, SOC = 0%), the energy store 28 unloaded has a terminal voltage of typically 10.8 volts. The vehicle electrical system voltage in the low-voltage sub-network 21 is in driving operation, depending on the temperature and state of charge of the energy storage 28, approximately in

Range between 10.8 volts and 15 volts. The DC-DC converter 22 is connected on the input side to the high-voltage sub-network 20 and to the generator 23. The DC-DC converter 22 is connected on the output side to the low-voltage sub-network 21. The DC-DC converter 22 is formed, a DC voltage received on the input side, for example a DC voltage

DC voltage with which the high voltage subnet is operated, for example, between 12 and 48 volts, to receive and generate an output voltage, which is different from the voltage received on the input side, in particular a

Output voltage to produce, which is smaller than the voltage received on the input side, for example, 12 V or 14 V. Figure 3 shows an electrical system 1 with a high-voltage sub-network 20 and a

Low voltage sub-network 21, which are connected by a bidirectional, potential-separating DC-DC converter 31. The illustrated vehicle electrical system 1 is in

Essentially designed as the electrical system shown in Figure 2, wherein the generator is integrated in the high voltage subnet and for the energy transfer between the

Teilbordnetzen 20, 21 a DC-DC converter 31 is used, the

potential separation is performed. In both subnetworks 20, 21, moreover, consumers 25, 29 are arranged, as described with reference to FIG. Essentially, the system illustrated in FIG. 3 differs in the integration of the starter. While in the system shown in Figure 2, the starter 26 is disposed in the low voltage subnet 21 and thereby the DC-DC converter 22 can be unidirectionally designed for energy transport from the high voltage sub-network 20 in the low voltage subnet 21, in the architecture shown in Figure 3, a starter generator 30 in High voltage subnet 20 used. In this case, the DC-DC converter 31 is bidirectional, so that the battery 24 can be charged via the low-voltage sub-network 21, if necessary.

FIG. 4 shows a vehicle electrical system 1 with a high-voltage sub-network 20 and a

Low voltage subnet 21, for example, a vehicle electrical system 1 of a vehicle, in particular a motor vehicle, transport vehicle or forklift. The electrical system 1 is particularly suitable for use in vehicles with a 48-volt generator, a 14-volt starter and a boost recuperation system.

The high-voltage sub-network 20 includes a starter-generator 30, which has a

Internal combustion engine (not shown) can start and is operable by this. The starter-generator 30 is designed to generate electrical energy as a function of a rotational movement of the engine of the vehicle and to feed it into the high-voltage sub-network 20. In the high voltage sub-network 20 load resistors are arranged, which may be formed for example by at least one, preferably by a plurality of electrical high-voltage consumers 25 of the motor vehicle, which are operated with the high voltage. The high voltage sub-network 20 also includes a battery 40, which may be formed, for example, as a lithium-ion battery and which is adapted to feed the operating voltage of 48 volts in the high voltage sub-network 20. The lithium-ion battery 40 preferably has a rated voltage of 48 volts

Minimum capacity of about 15 Ah to save the required electrical energy.

The battery 40 has a plurality of battery units 41 -1, 41 -2, ... 41 -n, wherein the

Battery units 41 are assigned a plurality of battery cells, which are usually connected in series and partially in addition to each other in parallel to the required

To achieve power and energy data with the battery 40. The individual battery cells are, for example, lithium-ion batteries with a voltage range of 2.8 to 4.2 volts. The battery units 41 -1, 41 -2, ... 41 -n are assigned Einzelspannungsabgriffe 80-1 1, 80-12, 80-21, 80-22, ... 80-n1, 80-n2, via which the Voltage of a coupling unit 33 is supplied. The coupling unit 33 is set up to connect at least one of the battery units 41 of the battery 40 to the low-voltage sub-network 21 for its operation or support, and to appropriately interconnect these with respect to the high-voltage sub-network 20.

The coupling unit 33 couples the high voltage subnet 20 to the

Low-voltage sub-network 21 and provides the output side, the low-voltage sub-network 21, the necessary operating voltage ready, for example, 12 V or 14 V. The structure and the

The mode of operation of the coupling unit 33 will be described with reference to FIGS. 5 to 7.

The low-voltage sub-network 21 includes the low-voltage consumers 29, which are designed, for example, for operation at 14 V voltage. After a

Embodiment is provided that the lithium-ion battery 40, the supply of closed circuit loads, which are shown as a consumer 25, 29, takes over when the vehicle is parked. For example, it can be provided that in this case the requirements of the so-called airport tests are met, wherein after six weeks of service the vehicle is still bootable and the battery provides the quiescent currents of the low-voltage consumers 29 in the low voltage subnet 21 during the service life, so that, for example, an anti-theft alarm system is supplied. In the low-voltage sub-network 21, an energy store 28 is optionally arranged, which can deliver very high power for a short time, ie is optimized for high performance, and as a

Cache acts. The energy storage 28 fulfills the purpose that overvoltages when switching the battery units 41 are further avoided. Is used as

Energy storage 28 is a capacitor used, its dimensioning is preferred:

^ max ^ switch

AU where Lax is the maximum on-board electrical system _current which can flow in the I during the switching operations, t _equals the time during which no battery unit 41 for the

Supply is available, and AU _{max is} the maximum permissible change of the

On-board voltage during the switching process. Figure 5 shows a coupling unit 33, which is designed as a unidirectional, galvanically non-separating DC-DC converter (DC / DC converter). The coupling unit 33 comprises reverse blocking switches 44, 45, which have the property that in a state "on" they allow current to flow in only one direction and in a second state "off" they can absorb a blocking voltage of both polarities. This is an essential difference to simple semiconductor switches, such as e.g. IGBT switches, as they can not pick up reverse voltage due to their intrinsic diode. Due to the dependence on the direction of current flow, two different types of switches are shown in FIG. 5, namely RSSJ 45 and RSS_r 44, which do not have to differ in their production, but are merely installed with different polarity. An example of the structure of the reverse blocking switches 44, 45 will be described with reference to FIG.

In the coupling unit 33, the individual voltage taps 80 of the battery units 41 are each supplied to one of the different reverse blocking switches RSSJ 45 and RSS_r 44. The reverse blocking switches RSSJ 45 are the output side of the

Coupling unit 33 connected to the positive pole 52, and the reverse blocking switch RSS_r 44 are the output side of the coupling unit 33 connected to the negative pole 51. The coupling unit 33 includes reverse blocking switches VSS 90, which may be, for example, standard semiconductor switches. An example of the structure of the reverse inhibit switch 90 will be described with reference to FIG. In the

Coupling unit 33, the individual taps of the battery units 41 are branched and fed in parallel to the reverse blocking switches each a non-forward switch VSS 90. The reverse inhibit switches VSS 90 serially connect the battery units 41 if the reverse inhibit switches VSS 90 are closed. In this case, a forward-blocking switch 90 is arranged between each two battery units 41, so that n-1 reverse-blocking switches VSS 90-1, VSS 90-2, ... VSS 90-Π-1 are provided in n battery units.

The reference symbol 73 shows the current path through the battery units 41 for supplying the high-voltage subnetwork. All non-forward switch 90 are closed. According to one embodiment, the vehicle electrical system or the control system is set up so that the battery 40 can only supply the starter-generator 30 with energy when all the non-forward-locking switches 90 are switched on. For the charging of the battery 40, the reverse blocking switches 90 need not necessarily be turned on, since the intrinsic diodes of the reverse blocking switch 90 can carry the charging current. Preferably, the reverse blocking switch 90 are always turned on when no parallel operation for the supply of the

Low voltage sub-network 21 takes place to the power loss within the

forward lock switch 90 to reduce.

The use of the reverse blocking switch 90 also allows two or more battery units 41 to be connected in parallel to supply the low voltage subnetwork 21. In this case, the affected reverse inhibit switches 90 are controlled to the "off" state, as will be explained with reference to Figure 8. In a different one

Voltage level of the parallel-connected battery units 41, the energy flow into the low voltage sub-network 21 only from that battery unit 41, which has the higher voltage level. The flow of energy from the higher voltage battery pack 41 to the lower voltage battery pack 41 is inhibited by the reverse inhibit switches 44, 45 associated with the lower voltage battery pack 41. During the parallel connection of battery units 41, the reverse blocking switches 90 are turned off and the generator ideally does not feed any energy into the high voltage sub-network 20. FIG. 6 shows the supply of the low-voltage sub-network 21 by way of example from FIG

Battery unit 41 -2 via the activated reverse blocking switches RSSJ 45-i, RSS_r 44-i. From the positive terminal 52, a current path 71 leads via the reverse blocking switch RSSJ 45-i via the second through-connected battery unit 41 -2 via the further reverse blocking switch RSS_r 44-i to the negative pole 51. The others

reverse blocking switch 44, 45 are turned off.

The voltage level of the high voltage subnet 20 based on the mass of

Low voltage sub-network 21 depends on which of the battery units 41 is switched on or are. In any of the operating states, however, one of the potentials has an amount which is a voltage limit equal to the sum of the high voltage and the

Low voltage exceeds, i. at a 48 volt mains and a 14 volt mains at about 62 volts. However, there may be negative potentials compared to the mass of the

Low voltage subnet 21 occur.

The operation of the starter-generator 30 is independent of the operation of the coupling unit 33 and the supply of the low-voltage sub-network 21st In the through-connected

Battery unit 41, which supplies the low voltage subnet 21, results in a

Overlay by the low voltage part of the network current and possibly fed by the starter-generator 30 in the entire battery 40 charging current (generator mode) or by the entire battery 40 extracted discharge (engine operation). As long as the allowable limits of the battery cells, e.g. the maximum allowable discharge current of the cells are not exceeded, these processes can be considered independently. So that the low-voltage sub-network 21 is reliably supplied, at least one of the battery units 41 is always connected via the associated switches 44, 45, 90 of the coupling device 33. Due to the multiple redundant supply of the

Low voltage sub-network 21 can be constructed with the architecture presented a system which has a very high availability of electrical energy in the

Low voltage subnet 21 has.

FIG. 7 shows the supply of the low-voltage sub-network 21 by way of example from FIGS

Battery units 41 -1, 41 -2 via the activated reverse blocking switches RSSJ 45-i, RSSJ 45-j, RSS_r 44-i, RSS_r 44-j. From the positive pole 52, a first current path 71 leads via a reverse blocking switch RSSJ 45-i via the second battery unit 44-2 and via the further reverse blocking switch RSS r 44-i to the negative pole 51. From

Plus pole 52 also leads a further current path 72 via the reverse blocking switch RSSJ 45-j via the first through-connected battery unit 41 -1 via the further reverse blocking switch RSS_r 44-j to the negative pole 51.

FIG. 8 shows the supply of the low-voltage sub-network 21 by way of example from the battery units 41 -1, 41 -2 via the activated reverse-blocking switches RSSJ 45-i, RSSJ 45-j, RSS_r 44-i, RSS_r 44-j and the open reverse-blocking switch VSS 90 -1, which is located between the battery units 41 -1, 41 -2. From the positive pole 52, a first current path 72 leads via a reverse blocking switch RSSJ 45-i via the first battery unit 41 -1 and via the further reverse blocking switch RSS_r 44-j to the negative pole 51. From the positive pole 52 also leads a further current path 71 via the reverse blocking switch RSSJ 45-j on the second through-connected battery unit 41 -2 via the further reverse blocking switch RSS_r 44-i to the negative terminal 51. When the reverse inhibit switch VSS 90-1 is open, are the first battery unit 41 -1 and the second battery unit 41 -2 connected in parallel with respect to the low voltage subnet. The positive pole of the first battery unit 41 -1 is connected electrically high impedance. In the event that a switchover of the battery units 41 with uninterrupted

Supply of the high-voltage sub-network 20 should be made, the reverse blocking switch 90 must remain switched on. Therefore, a first switching method is specified in which, in a first step a), the reverse blocking switches 44, 45 assigned to the connected battery units 41 are switched off. Then, in a second step b), with a delay whose duration essentially depends on the characteristics of the switches 44, 45 used, the connection of the

zuzuschaltenden battery units 41 to the low voltage sub-network 21st

If, for example, in FIG. 7 battery unit 41 -2 is to be changed to 41 -1, those of battery unit 41, which are initially in current-carrying power, are assigned

reverse blocking switch 45-j, 44-i off and the others

reverse inhibit switch 45-i, 44-j turned on. If the coupling unit 33 were to receive the switching commands for the switches 45-i, 44-i, 45-j, 44-j in a synchronized manner, the positive pole 52 of the

Low voltage subnetwork during the switching phase of the circuit breaker with the connected higher potential of the two battery units and the negative pole 51 during the switching phase with the lower potential of the two battery units. This would in the short term, a much larger voltage to the low voltage sub-network 21 is applied as the specification of the low voltage subnet allowed. In the example shown in FIG. 7, the low-voltage subnetwork 21 would be connected in series because of the series connection

Battery units 41 in the short term, the sum of the partial voltages of the battery units 41 -1, 41 -2 are provided. To avoid these surges, is in the

Switchover of the coupling unit 33 proceeded as follows: - The switchover is such that the reverse blocking switch 44-i, 45-j of the current-carrying battery unit, in the example shown, the battery unit 41 -2, are first turned off and after the switch the current leading

Battery unit 41 -2 no longer carry power, the reverse blocking switch 44-j, 45-i of the battery unit 41 -1, which supply the

Low voltage subnet 21 to take over, turned on. The principle described is also referred to as "break-before-make".

The delay between switching off and on is required, since otherwise the voltage in the low-voltage sub-network 21 would rise to impermissibly high values in all switching operations during the transition phase, in the case illustrated in FIG. 7 to the sum of the voltages of the battery units 41 -1 and 41 -2, that is twice the value. If the coupling device 33 is switched with a delay time, but this means that the supply of the low voltage sub-network 21 is briefly interrupted. In order to avoid an inadmissible voltage dip, according to some

Embodiments buffering means of the energy storage 28 are made. If a capacitor is used as the energy store 28, then it takes place

Dimensioning preferably as described with reference to Figure 4.

The voltage dip in the low-voltage sub-network 21 can be further advantageously reduced, if the switching takes place at such times at which the electrical system power is as low as possible. This can be done, for example, by evaluating a signal for the on-board electrical system current and dependent control of the switch of the coupling unit. In addition, syncing with a

Consumer management system done to high voltage consumers, such as Switch off heating systems for a short time without sacrificing comfort, in order to enable switching of the battery units without significant voltage drop.

For the further case that the supply of the low voltage subnetwork 21 is not to be interrupted, a further switching method is provided, wherein in a first step c) all non-forward switch 90 are turned off. The starter-generator 30 feeds no energy in the switching phase

High voltage subnetwork and does not work in boost mode. With a short delay, the duration of which depends on the characteristics of the switches used, in a second step d) the reverse blocking switches 44, 45 are assigned to the associated switch

Battery unit or battery units 41 is turned on. In an optional third step e), if a change of the low-voltage subnet 21 connected battery unit 41 is provided, the shutdown of the first, connected battery unit 41 -1 of the low voltage subnet 21. It can also change between not directly

take place adjacent battery units 41. In a fourth step d), the reverse blocking switches 90 are switched on again. After the restoration of the connection, the parallel connection of the two battery units or the commutation of the first to the second battery unit is completed, without the supply of the low voltage subnet 21 was interrupted.

The selection of switching methods is made by the control system, for example, depending on which subnetwork should be prioritized. As another

Possibility can be provided in operating phases in which the full power or not the full voltage of the battery is required in the high voltage subnet, to go to a reduced voltage operation. Then can take place with the coupling unit 33 an uninterruptible supply of the low voltage subnet.

FIG. 9 shows a possible construction of reverse-blocking switches 44, 45 and reverse-blocking switches 90. The direction of passage of the switches is indicated by I. For example, a reverse inhibit switch RSS_r 44 includes one

IGBT, MOSFET or bipolar transistor 101 and a series-connected diode 103. In Figure 9, a MOSFET is shown, which has a likewise shown, intrinsic diode 102. The diode 103 connected in series with the MOSFET 101 is poled against the direction of the intrinsic diode 102 of the MOSFET 101. The reverse blocking switch RSS_r 44 passes the current in the forward direction I and locks in opposite direction. The reverse blocking switch RSSJ 45 corresponds to the RSS_r 44, is installed only with the reverse polarity, so that the pass and reverse directions are reversed. A reverse inhibit switch 90 includes a MOSFET, IGBT, or bipolar transistor 101, with its intrinsic diode 102 also shown. The switches RSSJ 45, RSS_r 44 and VSS 90 are characterized in particular by a barely noticeable delay in the switching operations, ie allow a very short switching time. About a suitable drive circuit, the

Time delay between switching off and switching on the switch can be set very accurately.

FIG. 10 shows the setting of switching states as a function of different operating phases. FIG. 10 shows four different operating phases 102, 103, 104, 105 whose detection or setting leads to a changeover 101 of the switching states of the coupling device. A first phase of operation 102 is a passive phase of the system, such as a parked vehicle or parked vehicle. A second operating phase 103 is a starting phase of the system, for example a motor vehicle start. A third operating phase 104 is a start-stop phase of the system, for example a start-stop operation of a motor vehicle. A fourth phase of operation 105 is an active phase of the system, for example a driving operation of the vehicle.

The battery underlying the figures 10 to 14 includes four exemplary

Battery units that can supply the high-voltage subnetwork each 12 V voltage. The coupling unit is set up to provide at least the following operating states:

Configuration Switching states High-voltage low-voltage sub-network mains

1 s4p 3 reverse blocking 12V supply from the 1 s4p

Switch between 4 battery unit adjacent

battery units

off, 8

reverse blocking

Switch this

battery units

switched on

2s1 p + 1 s2p 1 reverse blocking 36V supply from the 1 s2p

Switch between 2 battery unit adjacent

battery units off, 4

reverse blocking

Switch this

battery units

switched on

1 s1 p + 1 s3p 2 reverse-blocking 24V supply from the 1 s3p

Switch between 3 battery unit adjacent

battery units

off, 6

reverse blocking

Switch this

battery units

switched on

4s1p All 48V supply from one of the 4-battery-units switchable reverse switch,

2 reverse blocking

Switch for

Low voltage subnet switched on

The table shows configurations of the battery that can be set via the coupler. XsYp means X cells connected in series and Y cells in

Parallel. For example, 2s1 p means a series connection of two

Battery units and 1 s2p a parallel connection of two battery units.

FIG. 11 shows configurations of the battery system in the first phase of operation 102, d. H. for example, when the vehicle is parked. A first configuration 1 10 is 1 s4p, d. H. a battery unit is the

High voltage subnet switched on and all, d. H. here four battery units with respect to the low voltage subnet connected in parallel. This configuration is preferred in the first operating phase 102. It is then set when the idle mode of the

High voltage subnet is possible by only one battery unit available voltage. In the configuration 1 10 is a supply 1 14 of the

High-voltage subnetwork with the energy provided by a battery unit.

In addition, a balancing can be done 1 15 of the battery units, d. H. a compensation of the charges of the individual battery units. When the battery unit is connected in parallel to the 1 s4p configuration 1 10, the battery unit is discharged with the highest charge

Charge state automatically, and it adjusts to a balancing of the battery units. In a second configuration 1 1 1, namely 2s1 p + 1 s2p, with a non-forward switch between two adjacent battery units is turned off and four reverse blocking switch of these battery units are turned on, takes place

Supply 1 16 of the high-voltage subnetwork with a reduced voltage, here for example with half of the high voltage. Balancing 1 17 of the battery units is possible by changing the supply of the low voltage subnet. A

Supply 1 18 of the low voltage subnetwork is possible without interruption when changing the battery unit. In a third configuration 1 12, namely 1 s1 p + 1 s3p, in which two non-forward switch between three adjacent battery units are turned off and six rückwärtssperrfähige switch of these battery units are turned on, there is a supply 1 19 of the high voltage subnet with a reduced voltage, here, for example three quarters of the high voltage. Balancing 120 of the battery units can take place via a change in the supply 121 of the low-voltage subnetwork. A supply 121 of the low voltage subnetwork is possible without interruption.

The second and the third configuration 1 1 1, 1 12 are preferably set when the high voltage subnet can indeed be supplied with reduced voltage, but this voltage is necessarily higher than the low voltage that can be provided by a battery unit. In all configurations, with the exception of the first configuration 1 10, the balancing of the battery units is performed by a change of that battery unit, which is used to supply the low voltage subnet. Such a change can either with a short interruption of the direct supply of the low voltage subnet from a battery unit and thus with appropriate

Measures for buffering the electrical system, for example by means of a

Capacitor, or with an uninterruptible supply of the

Low voltage subnet. In the latter case, however, must be accepted in the switching phase that the voltage in the high-voltage subnetwork is briefly limited, for example, to two-thirds.

If the high voltage subnetwork in the first phase of operation 102 with the

High voltage is to be supplied, a fourth configuration 1 13, namely 4s1 p can be set. In this configuration, a supply 122 of the

High voltage subnetwork with the sum voltage of the battery units, in addition to a balancing 123 of the battery units via a change of the supply of the low voltage subnet done. The supply 124 of the low-voltage subnetwork is made from a single battery unit. When changing the switched

Battery unit is the supply 124 of the low voltage subnet not

without interruption, or there is a collapse of the high voltage supply 122nd

The supply of the low voltage subnet is carried out in the fourth configuration 1 13 during the Abstellphase from that battery unit which has the highest state of charge. This selection rule ensures that the battery unit with the highest charge state is discharged faster than the other battery units.

FIG. 12 shows the setting of the switching states in the second operating phase 103, for example the start of the motor vehicle. So that the system on the

High voltage subnet page can deliver its maximum possible power, all battery units are connected to a configuration 120 in series, d. H. in the example with four battery units to 4s1 p. Thus, a supply 121 of the high voltage subnetwork with maximum possible power of the battery, a supply 122 of the

Low voltage subnetwork from the battery unit with the largest state of charge (SOC). In this case, that battery unit is selected which has the largest charge state. In addition, there is an optimization 123 of the SOC difference of the battery units.

FIG. 13 shows the configuration of the battery system for the third operation phase 104, for example, the start-stop operation. The third operating phase 104 has a

Stop operation 131 and a start operation 132 on. In the stop mode 131, the same statements apply as for the first operating phase 102, which was described with reference to FIG. 11. The selection of the configuration of the battery system therefore preferably takes place according to the same criteria. If the high-voltage sub-network can operate with a low voltage in the stop mode 131, the configuration 1 s4p is preferably set. A supply 133 of the high-voltage consumers takes place with the power which is provided by a battery unit. A supply 134 of

Low-voltage consumer is made from the battery unit with the largest SOC. In addition, there is an optimization 135 of the SOC difference of the battery units and an optimization 136 regarding the maintenance of the performance for the start. For the subsequent start operation, the configuration 132 is changed. There is a Maximum power output 137 by the battery, a supply 138 of the low voltage subnet of that battery unit with the largest SOC and an optimization 139 of the SOC difference of the battery units. FIG. 14 shows the configuration of the battery system in the fourth operating phase 105, for example while driving. The fourth operating phase 105 has a boost operating state 141 and a recuperation operating state 142, as well as a

Operating state 143, in which the starter-generator feeds no energy into the electrical system and an operating state 144, in which the starter-generator feeds only low electrical energy into the electrical system, for example, less than 12 V or as 24 V.

In the boost operating state 141, the battery system should deliver the highest possible power to the starter-generator and can be charged in recuperation operating state 142 with the highest possible power. In addition to be provided or recorded as much energy in these two modes 141, 142 as possible. Therefore, in these two modes 141, 142, the configuration 4s1p is set. In the boost operating state 141, a delivery 145 of maximum power for the boost by the battery takes place, a supply 146 of the low-voltage subnetwork of that

Battery unit with the largest SOC and an optimization 147 of the SOC difference of the battery units. In Rekuperationsbetriebszustand 142 takes place a charge 148 with maximum power by the battery, a supply 149 of the low voltage subnet from that battery unit with the largest SOC and an optimization 150 of the SOC difference of the battery units. In the operating states 143, 144, in which the starter-generator feeds no energy into the electrical system or only low electrical energy fed into the electrical system, for example, to cover the energy needs, if no longer time

Recuperation phase has occurred, in principle, all four configurations 1 s4p, 2s1 p + 1 s2p, 1 s1 p + 1 s3p or 4s1 p are set, which is indicated by reference numerals 151 and 152. In these phases, no or low generator power 143, 144, the statements made for the parked vehicle apply. If the voltage in the high voltage subnet can be lowered down to the low voltage in such operating phases, the setting of the 1 s4p configuration is preferred. Then behaves the electrical system almost like a standard low voltage electrical system, in which the

Generator covers the average vehicle electrical system load. With the described procedure, the switching states of the coupling device for all four different operating phases 102, 103, 104, 105 of the vehicle can be set according to a defined rule. In those places where the description still leaves options or alternatives open, the boundary condition in the specific implementation of the high-voltage subnetwork creates uniqueness, for example the possibility of being able to operate the high-voltage subnetwork also with low voltage. The operating state 1 s4p is of particular interest even if the

High voltage subnet is not used to supply high voltage consumers, but to optimize the maximum power of the starter-generator. Then, the generator can be operated at moderate power at the low voltage, and the parallel connection of all battery units causes an on-board network adjusts with similar function as the low voltage subnet according to the current state of the art. The generator can directly supply the middle on-board electrical system, the battery is used in this state as a buffer memory. Are all battery units via the switches of

Coupling unit connected in parallel to the low voltage subnet power supply, so that battery unit with the highest state of charge is automatically discharged, and it automatically adjusts the balancing of the battery units. Is starting from this

Condition high performance of the starter generator required, for example, in boost mode or can be fed back in a Rekuperationsvorgang energy with such high power that this is not feasible in the low-voltage operation of the starter generator, so the battery changes over the switching states in the coupling unit is reconfigured to a 4s1 p configuration. When using fast semiconductor circuits of

Coupling the required switching times can be kept very small.

The invention is not limited to the embodiments described herein and the aspects highlighted therein. Rather, within the range specified by the claims, a variety of modifications are possible in the context

professional action.

Claims

claims

1 . On-board network (1) for a motor vehicle, wherein the electrical system (1) a

Low-voltage subnetwork (21) for at least one low-voltage consumer (29) and a high voltage sub-network (20) for at least one high-voltage consumer (25) and a starter generator (30), wherein the high-voltage subnet (20) with the low-voltage subnet (21) via a coupling unit ( 33), the on-board network (1) having a battery (40) which is set up to generate the high voltage and to feed it into the high-voltage subnetwork (20) and which has at least two battery units (41) with individual voltage taps (42), which are guided to the coupling unit (33), wherein the coupling unit (33) is adapted to provide at least a first and a second operating state, wherein in the first operating state, the high voltage sub-network (20) from all battery units (41) of the battery (40) is fed and that

Low voltage subnet (21) from a battery unit (41) is fed and in the second operating state, the high voltage subnet (20) from a battery unit (41) is fed and the low voltage subnet (21) from at least one battery unit (41) is fed.

2. Vehicle electrical system (1) according to claim 1, characterized in that the battery units (41) are each designed to provide the low voltage.

3. Vehicle electrical system (1) according to one of the preceding claims, characterized in that the coupling unit (33) rückwärtssperrfähige switch (44, 45) and / or reverse blocking switch (90).

4. Vehicle electrical system (1) according to one of the preceding claims, characterized in that in the second operating state, at least two battery units (41) with respect to the low voltage subnet (21) are connected in parallel to each other.

5. Vehicle electrical system (1) according to one of the preceding claims, characterized in that in the first operating state, at least two battery units (41) are connected in series with respect to the high voltage sub-network (20).

6. vehicle electrical system (1) according to one of the preceding claims, characterized in that the coupling unit (33) is adapted to at least one further

Provide operating state, wherein in the further operating state the

High voltage subnet (20) from several battery units (41) is fed and the low voltage subnet (21) of several parallel connected

Battery units (41) is fed.

7. Motor vehicle with an internal combustion engine and a vehicle electrical system (1) according to one of claims 1 to 6.

Method for operating a vehicle electrical system according to one of claims 1 to 6, wherein the control of the coupling unit for setting the first or second

Operating state in response to an operating phase (102, 103, 104, 105) of the motor vehicle takes place.

A method according to claim 8, characterized in that a first operating phase (102) is a parked vehicle or parking vehicle and / or a second operating phase (103) is a motor vehicle start and / or a third phase of operation (104) a start-stop operation of Motor vehicle is and / or a fourth

Operating phase (105) is a driving operation of the motor vehicle.

10. The method according to claim 8 or 9, characterized in that in the first operating state, the supply of the low voltage sub-network (21) from that battery unit (41) takes place, which has the highest state of charge.