DE102019212930B3 - Vehicle electrical system and method for operating a vehicle electrical system - Google Patents

Abstract

A vehicle electrical system (1) has an HV electrical system part (10), an LV electrical system part (20), a charging connection (32) for connecting the vehicle electrical system (1) to a charging station (30), and an energy transmission device (60) which in a charging mode converts a charging station voltage (CV) into an HV vehicle electrical system voltage (HV) and transfers energy from the charging station (30) to an HV energy store (12), in a discharge mode the HV vehicle electrical system voltage (HV) into the charging station voltage (CV) ) converts and transfers energy from the HV energy store (12) to the charging station (30), and in a recharging mode converts the HV vehicle electrical system voltage (HV) into an LV vehicle electrical system voltage (LV) and converts energy from the HV energy store (12) to an LV -Energy storage (22) transfers. According to the invention, an energy transmission device (60) is proposed for this purpose, comprising: a bidirectional voltage converter (62, 64), via which the transmission takes place in the charging mode in a first direction and the transmission takes place in the discharge mode and recharging mode in a second direction, and a switching device ( 66), which connects the voltage converter (62, 64) in charge mode and discharge mode with the charging connection (32) and the HV on-board power supply unit (10), and in reloading mode with the HV on-board power supply unit (10) and the LV on-board power supply unit (20) connects.

Description

The present invention relates to an electrical vehicle electrical system, for example for an electric or hybrid vehicle, according to the preamble of claim 1. Furthermore, the invention relates to a method for operating such a vehicle electrical system.

• - einen Hochvolt (HV)-Bordnetzteil mit einem elektrischen HV-Energiespeicher zur Bereitstellung einer HV-Gleichspannung (z. B. 400 V) als eine erste Bordnetzspannung,
• - einen Niedervolt (LV)-Bordnetzteil mit einem elektrischen LV-Energiespeicher zur Bereitstellung einer LV-Gleichspannung (z. B. 12 V) als eine zweite Bordnetzspannung,
• - einen Ladeanschluss zum Anschließen des Fahrzeugbordnetzes an eine Ladestation, die eine Ladestationsspannung (z. B. 220 V / 50 Hz Wechselspannung) für ein Übertragen von elektrischer Energie zwischen der Ladestation und dem Fahrzeugbordnetz bereitstellt,
• - eine Energieübertragungseinrichtung, die dazu ausgebildet ist,
• - in einem Lademodus die Ladestationsspannung in die HV-Bordnetzspannung zu wandeln und damit elektrische Energie von der Ladestation zum elektrischen HV-Energiespeicher zu übertragen,
• - in einem Entlademodus die HV-Bordnetzspannung in die Ladestationsspannung zu wandeln und damit elektrische Energie vom elektrischen HV-Energiespeicher zur Ladestation zu übertragen, und
• - in einem Umlademodus die HV-Bordnetzspannung in die LV-Bordnetzspannung zu wandeln und damit elektrische Energie vom elektrischen HV-Energiespeicher zum elektrischen LV-Energiespeicher zu übertragen.

Such vehicle electrical systems are known in various designs from the prior art and have:

• - A high-voltage (HV) on-board power supply unit with an electrical HV energy store to provide a HV DC voltage (e.g. 400 V) as a first on-board network voltage,
• - A low-voltage (LV) on-board power supply unit with an electrical LV energy storage device to provide a LV DC voltage (e.g. 12 V) as a second on-board network voltage,
• - A charging connection for connecting the vehicle electrical system to a charging station, which provides a charging station voltage (e.g. 220 V / 50 Hz AC voltage) for transferring electrical energy between the charging station and the vehicle electrical system,
• - an energy transmission device which is designed to
• - to convert the charging station voltage into the HV on-board network voltage in a charging mode and thus transfer electrical energy from the charging station to the electrical HV energy store,
• - to convert the HV vehicle electrical system voltage into the charging station voltage in a discharge mode and thus to transfer electrical energy from the electrical HV energy store to the charging station, and
• - To convert the HV vehicle electrical system voltage into the LV vehicle electrical system voltage in a recharging mode and thus transfer electrical energy from the electrical HV energy store to the electrical LV energy store.

In such known vehicle on-board networks, the energy transmission device typically comprises, on the one hand, a special on-board charger, often referred to as an “on-board charger” (OBC), in order to achieve the “charging mode” and the “discharging mode”, i.e. H. For example, to charge a 400 V high-voltage (HV) battery from a public 220 V AC voltage network or to transfer energy from the HV battery to the AC voltage network, and on the other hand, a dedicated DC / DC converter to activate the "recharging mode" accomplish, for example, to use energy from the 400 V HV battery to charge a 12 V low-voltage (LV) battery.

Disadvantages of such known vehicle electrical systems are, for example, the installation space required by the energy transmission device and its weight, as well as the amount of material and costs required to provide the energy transmission device.

The pamphlet DE 10 2019 000 238 A1 relates to a method for charging a battery of a first vehicle electrical system, wherein a DC voltage converter, which leads to a second vehicle electrical system, can be optionally connected to the battery or to the output of a PFC unit via a switch.

The pamphlet DE 11 2016 005 080 T5 describes a bidirectional conversion device in which an AC connection is connected to a battery via the conversion device. These three components are linked in series, with no further options for linking.

The pamphlet US 2018/0198381 A1 describes a circuit with galvanic isolation, where an H-bridge is provided galvanically isolated from another H-bridge. This is used to supply a load by means of an AC voltage source across the galvanic isolation. Here, too, there is a serial, static link between the individual components that exist between the AC voltage source and the load.

It is an object of the present invention to eliminate the above disadvantages in a vehicle electrical system of the type mentioned at the outset and to provide a way of accomplishing the various operating modes such as loading mode, unloading mode and reloading mode, which is less complex.

According to the invention, this object is achieved by a vehicle electrical system according to claim 1 and a method for operating such a vehicle electrical system according to claim 7. The dependent claims are directed to advantageous developments of the invention.

• - einen bidirektional betreibbaren Spannungswandler, über den in einer ersten Übertragungsrichtung die Übertragung der elektrischen Energie im Lademodus erfolgt, und in einer zweiten Übertragungsrichtung die Übertragung der elektrischen Energie im Entlademodus und im Umlademodus erfolgt, und
• - eine Umschalteinrichtung, die dazu ausgebildet ist, den Spannungswandler im Lademodus und im Entlademodus einerseits mit dem Ladeanschluss und andererseits mit dem HV-Bordnetzteil zu verbinden, und im Umlademodus einerseits mit dem HV-Bordnetzteil und andererseits mit dem LV-Bordnetzteil zu verbinden.

The vehicle electrical system according to the invention is characterized in that the energy transmission device has:

• - A bidirectionally operable voltage converter, via which the electrical energy is transmitted in the charging mode in a first transmission direction, and the transmission of the energy in a second transmission direction electrical energy takes place in the discharge mode and in the transfer mode, and
• - A switching device which is designed to connect the voltage converter in the charging mode and in the discharging mode on the one hand to the charging connection and on the other hand to the HV on-board power supply, and to connect it to the HV on-board power supply on the one hand and the LV on-board power supply on the other in the charging mode.

With the invention, the functions of the charging mode, discharging mode and recharging mode can advantageously be achieved by means of one and the same circuit device, namely the bidirectionally operable voltage converter, which is to be operated in one of two possible directions (electrical energy transmission) depending on the currently required mode. The invention thus enables a drastic simplification of the circuitry of the vehicle electrical system. The correct "connection" of the bidirectionally operable voltage converter to the corresponding on-board power supply components (HV on-board power supply, LV on-board power supply, charging connection), which depends on the currently required mode and is therefore variable, can be easily accomplished using the switching device.

A preferred use of the vehicle electrical system within the scope of the invention results for an electric vehicle or a (plug-in) hybrid vehicle, in particular z. B. Road vehicles of this type in which an electrical drive device is supplied with electrical energy from the high-voltage (HV) on-board power supply, whereas other (less powerful) electrical consumers of the vehicle (such as lighting devices) from the low-voltage (LV) - On-board power supply are supplied.

In one embodiment of the invention, the terms “high voltage (HV) DC voltage” (first vehicle electrical system voltage) and “low voltage (LV) DC voltage” (second vehicle electrical system voltage) are to be understood to mean that the HV DC voltage is significantly greater than the LV DC voltage , e.g. B. by at least one factor 2 , especially by at least one factor 5 .

In one embodiment of the invention, it is provided that the HV DC voltage is greater than 60 V and the LV DC voltage is a maximum of 60 V (which, for example, also corresponds to a customary definition of these terms).

In a preferred embodiment of the invention, the HV direct voltage is greater than 200 V, in particular greater than 300 V, and / or the LV direct voltage is a maximum of 60 V, in particular a maximum of 30 V.

The charging station, to which the vehicle electrical system or vehicle equipped with it is connected in the charging mode and in the discharging mode, can be used as charging station voltage z. B. provide a DC voltage. In this case it is preferred that the voltage level of the charging station voltage is between the voltage levels of the first on-board network voltage ( HV ) and the second vehicle electrical system voltage ( LV ) lies.

However, the charging station can also provide a (z. B. sinusoidal) alternating voltage as the charging station voltage. In this case it is preferred that the peak value of the charging station voltage between the voltage levels of the first on-board electrical system voltage ( HV ) and the second vehicle electrical system voltage ( LV ) lies.

In one embodiment it is provided that a sinusoidal 220 V alternating voltage is used as the charging station voltage.

The charging port for connecting the vehicle electrical system to the charging station can in particular, for. B. from an electrical connector component such. B. a charging socket or a charging plug at the end of an electrical cable, with a matching mating connector component is provided by the charging station. In the context of the invention, however, it should not be ruled out that the charging connection represents a component of an inductive charging device on the vehicle side, which is formed by components on the vehicle side and the charging station side after the vehicle has been positioned accordingly.

In one embodiment it is provided that the voltage converter has a first converter side and a second converter side, the switching device being designed to connect the first converter side to the charging connection in the charging mode and in the discharging mode and to connect it to the LV on-board power supply unit in the charging mode. This advantageously enables the second converter side to be permanently connected to the HV on-board power supply unit.

The terms “first converter side” and “second converter side” refer to the two ends of the energy transmission path formed by the voltage converter in the circuitry sense. In this respect, these sides could also be referred to as the input side and output side of the voltage converter, but due to the bidirectionality of the voltage converter used in the invention, the assignments “input” and “output” depend on which of the two possible transmission directions the electrical energy is transmitted in.

In one embodiment, each of the two converter sides is formed by a two-pole connection (two connections or two connection points).

In one embodiment, the switching device is designed to act on two poles, i. H. designed to connect the two poles of a two-pole connection of a converter side of the voltage converter either with the two poles of the two-pole charging connection or with the two poles of the LV on-board power supply, depending on the required operating mode.

In another embodiment, the changeover device is designed to be single-pole; H. designed to connect only one of the two poles of the relevant connection of the voltage converter to one of the two poles of the charging connection or to one of the two poles of the LV on-board power supply, depending on the required operating mode. The other of the two poles of the voltage converter, the charging connection and the LV on-board power supply unit can be permanently connected to one another in this case.

• - zwei Eingangsanschlüsse, die über eine jeweilige Drossel mit einem jeweiligen von zwei Brückenzweiganschlüssen einer Vollbrücke verbunden sind,
• - die genannte Vollbrücke mit vier ansteuerbaren Halbleiterschaltern,
• - zwei Ausgangsanschlüsse, die mit einem jeweiligen von zwei Vollbrückenversorgungsanschlüssen verbunden sind,
• - einen Kondensator mit zwei Kondensatoranschlüssen, die mit einem jeweiligen der zwei Ausgangsanschlüsse verbunden sind.

In one embodiment it is provided that the voltage converter has a voltage converter unit which, viewed in the first transmission direction (that is, the transmission direction actually used for the “charging mode”) has:

• - two input connections, which are connected via a respective choke to a respective one of two bridge branch connections of a full bridge,
• - the mentioned full bridge with four controllable semiconductor switches,
• - two output ports connected to a respective one of two full bridge supply ports,
• a capacitor with two capacitor terminals connected to a respective one of the two output terminals.

Such a voltage converter unit is also referred to below as a “first voltage converter unit” (to distinguish it from a “second voltage converter unit” described below).

Here, the terms “input connections” and “output connections” refer to the first transmission direction used in “charging mode”, i.e. H. the voltage converter unit can convert a voltage applied to the input connections and make it available in a voltage-converted manner at the output connections, electrical energy being transmitted from the input connections to the output connections. When the voltage converter unit is operated in “discharge mode” or in “charge reversal mode”, the connections of the voltage converter unit, which are referred to here as “input connections” and “output connections” merely for the sake of simpler circuitry description, swap their roles.

In one embodiment, the input terminals are connected directly to the chokes, i.e. H. by an electrical conductor without further circuit components arranged in the course of the line.

Notwithstanding this, however, at least one such further component could also be arranged in each of these line courses, in particular z. B. a resistive (z. B. current measuring resistor), inductive or capacitive component.

In one embodiment, a filter, in particular, for example, is in the circuit-related energy transmission path that runs between the input connections and the chokes. B. arranged passive filter, which z. B. can advantageously be designed as a so-called EMC filter to suppress the transmission of high-frequency interference signals via the voltage converter unit.

In a preferred embodiment, the two chokes are inductively coupled to one another. For this purpose, this z. B. be arranged on a jointly used magnetic flux guide ("core").

In one embodiment, the chokes are connected directly to the bridge arm connections of the full bridge (i.e. by an electrical conductor with no further circuit components arranged in the line). At this point, however, the arrangement of (at least) one further component should not be excluded.

A “full bridge”, which is often also referred to as an H-bridge in the art, is a circuit arrangement in which two series connections of variable-resistance elements, here the semiconductor switches, run parallel to one another between two connections, here referred to as full-bridge supply connections.

Depending on the set resistance of the four elements or the switching states (on or off) of the individual semiconductor switches, the full bridge can thus be used, for. For example, a voltage between the supply connections can be passed on to two “center taps” of the series connections (each lying in the path between the two semiconductor switches) (with any polarity). Due to the common name " Bridge path ”for an electrical load connected to these center taps, these center taps are referred to here as bridge arm connections.

The controllable semiconductor switches of the full bridge are preferably each designed as a field effect transistor (FET), in particular z. B. MOSFET, and in pairs in the respective series circuits preferably connected directly to one another.

The two output terminals of the voltage converter unit can, for. B. be connected directly to a respective one of the two full bridge supply connections.

In the circuitry energy transmission path between the output connections and the full bridge supply connections could, for. B. a filter, especially z. B. passive EMC filter.

Finally, the voltage converter unit can have a capacitor with two capacitor connections which are connected to a respective one of the two output connections. In this case in particular, the voltage converter unit can then particularly advantageously represent a so-called power factor correction filter (PFC) in the charging mode or be used as such in order to transfer the electrical energy from the charging station or the charging connection with a power factor of approximately 1 into the vehicle electrical system or to be transmitted further to the electrical HV energy store.

The voltage converter unit described above could in principle already form the bidirectionally operable voltage converter of the vehicle electrical system by, for. B. their output connections are permanently connected to the HV on-board power supply or the electrical HV energy storage device and their input connections by means of the switching device either to the charging connection (charging and discharging mode) or to the LV on-board power supply or the electrical LV, depending on the desired operating mode -Energy storage (recharging mode) can be connected.

It should be noted, however, that in practice a galvanic separation between the two converter sides is usually desirable, but the structure of the voltage converter unit described up to this point does not yet provide such galvanic separation, be it between the charging station and the HV on-board power supply unit (during charging and discharging) or between the HV on-board power supply and LV on-board power supply (when reloading).

• - zwei Eingangsanschlüsse, die (direkt oder indirekt) mit einem jeweiligen von zwei Vollbrückenversorgungsanschlüssen einer ersten Vollbrücke verbunden sind,
• - die genannte erste Vollbrücke mit vier ansteuerbaren Halbleiterschaltern (z. B. vier FETs),
• - einen ersten Schwingkreis mit wenigstens einer Drossel und wenigstens einem Kondensator, und mit zwei Schwingkreisanschlüssen, die mit einem jeweiligen von zwei Brückenzweiganschlüssen der ersten Vollbrücke verbunden sind,
• - einen zweiten Schwingkreis mit wenigstens einer Drossel und wenigstens einem Kondensator, und mit zwei Schwingkreisanschlüssen, die mit einem jeweiligen von zwei Brückenzweiganschlüssen einer zweiten Vollbrücke verbunden sind (direkt oder indirekt),
• - die genannte zweite Vollbrücke mit vier ansteuerbaren Halbleiterschaltern (z. B. vier FETs),
• - zwei Ausgangsanschlüsse, die mit einem jeweiligen von zwei Vollbrückenversorgungsanschlüssen der zweiten Vollbrücke verbunden sind,

wobei die Drossel des ersten Schwingkreises induktiv mit der Drossel des zweiten Schwingkreises gekoppelt ist.In one embodiment, e.g. B. is particularly advantageous with regard to the galvanic separation achieved with it, the voltage converter has a voltage converter unit, which, viewed in the first transmission direction, has:

• - two input connections that are (directly or indirectly) connected to a respective one of two full bridge supply connections of a first full bridge,
• - the mentioned first full bridge with four controllable semiconductor switches (e.g. four FETs),
• - A first resonant circuit with at least one choke and at least one capacitor, and with two resonant circuit connections, which are connected to a respective one of two bridge arm connections of the first full bridge,
• - A second resonant circuit with at least one choke and at least one capacitor, and with two resonant circuit connections, which are connected (directly or indirectly) to a respective one of two bridge arm connections of a second full bridge,
• - the mentioned second full bridge with four controllable semiconductor switches (e.g. four FETs),
• - two output connections, which are connected to a respective one of two full bridge supply connections of the second full bridge,

wherein the choke of the first resonant circuit is inductively coupled to the choke of the second resonant circuit.

Such a voltage converter unit is also referred to below as a “second voltage converter unit” (to distinguish it from the first voltage converter unit already described above).

In one embodiment, each of the two resonant circuits is formed by a resonant circuit path (connecting the two resonant circuit connections), in the course of which two (e.g. immediately successive) chokes and a capacitor are arranged, one of the chokes being inductive (with a choke of the other resonant circuit ) is coupled, for example with a shared magnetic core to form a transformer.

In a particularly advantageous embodiment of the invention, the voltage converter has both a “first voltage converter unit” and a “second voltage converter unit” arranged functionally in series with it.

Considered in the first transmission direction, the first is preferred Voltage converter unit and then arranged the second voltage converter unit.

In one embodiment of the invention, the vehicle electrical system also has a program-controlled control device for activating the energy transmission device.

This activation of the energy transmission device includes activation of the switching device so that the connection of the voltage converter corresponding to a currently required operating mode is provided (or is achieved by switching).

In the case of using a voltage converter suitable for its operation to be controlled, in particular z. B. with regard to a transmission direction of the (bidirectionally operable) voltage converter defined by this activation, the activation of the energy transmission device also includes such activation of the voltage converter.

This is e.g. B. required when using a voltage converter which includes a first and / or second voltage converter unit of the type described above. In this case, the control of the voltage converter comprises switching the relevant semiconductor switches (for example FETs) on and off in accordance with a control strategy suitable (for the desired voltage conversion).

The control strategy can be implemented in a program-controlled manner by means of the aforementioned program-controlled control device.

In the case of a control of a first and / or second voltage converter unit of the type described above, the z. For example, the control strategy implemented in the control device can be used to define, in particular, the switching times at which each of the semiconductor switches to be controlled is to be switched on and off.

• - Auswählen eines bestimmten Betriebsmodus des Fahrzeugbordnetzes aus mehreren Betriebsmodi, die den Lademodus, den Entlademodus und den Umlademodus umfassen,
• - Ansteuern der Umschalteinrichtung derart, dass damit die dem ausgewählten Betriebsmodus entsprechende Verbindung des Spannungswandlers vorgesehen wird,
• - Ansteuern des Spannungswandlers derart, dass damit die dem ausgewählten Betriebsmodus entsprechende Übertragung der elektrischen Energie vorgesehen wird.

According to a further aspect of the present invention, a method for operating a vehicle electrical system of the type described here is proposed, comprising the steps:

• - Selecting a specific operating mode of the vehicle electrical system from several operating modes, which include the charging mode, the discharging mode and the reloading mode,
• - Control of the switching device in such a way that the connection of the voltage converter corresponding to the selected operating mode is provided,
• - Control of the voltage converter in such a way that the transmission of electrical energy corresponding to the selected operating mode is provided.

• 1 ein Blockschaltbild eines Fahrzeugbordnetzes nach dem Stand der Technik,
• 2 ein Blockschaltbild eines Fahrzeugbordnetzes gemäß eines Ausführungsbeispiels,
• 3 ein Schaltbild einer Spannungswandlereinheit gemäß eines Ausführungsbeispiels, und
• 4 ein Schaltbild einer Spannungswandlereinheit gemäß eines weiteren Ausführungsbeispiels.

The invention is described further below on the basis of exemplary embodiments with reference to the accompanying drawings. They represent:

• 1 a block diagram of a vehicle electrical system according to the prior art,
• 2 a block diagram of a vehicle electrical system according to an embodiment,
• 3 a circuit diagram of a voltage converter unit according to an embodiment, and
• 4th a circuit diagram of a voltage converter unit according to a further embodiment.

1 shows the structure of a vehicle electrical system 1 as is known in the art.

The vehicle electrical system 1 has a high-voltage (HV) on-board power supply 10 with an electrical HV energy store 12th (e.g. electric battery such as lithium-ion accumulator) to provide HV DC voltage HV from Z. B. 400 V as a first vehicle electrical system voltage.

Furthermore, the vehicle electrical system 1 a low-voltage (LV) on-board power supply 20th with an electrical LV energy storage 22nd (e.g. electric battery such as lead accumulator) to provide LV DC voltage LV from Z. B. 12 V as a second vehicle electrical system voltage.

The vehicle electrical system 1 also has a charging port 32 for connecting the vehicle electrical system 1 to a (e.g. public) charging station 30th on.

The charging station 30th as in 1 symbolizes an alternating voltage of z. B. 220 V as a charging station voltage CV ready to get electrical power from the charging station 30th to the vehicle electrical system 1 or from the vehicle electrical system 1 to the charging station 30th to be able to transfer.

• - in einem Lademodus die Ladestationsspannung CV in die HV-Bordnetzspannung HV zu wandeln und damit elektrische Energie von der Ladestation 30 zum elektrischen HV-Energiespeicher 12 zu übertragen,
• - in einem Entlademodus die HV-Bordnetzspannung HV in die Ladestationsspannung CV zu wandeln und damit elektrische Energie vom elektrischen HV-Energiespeicher 12 zur Ladestation 30 zu übertragen, und
• - in einem Umlademodus die HV-Bordnetzspannung HV in die LV-Bordnetzspannung LV zu wandeln und damit elektrische Energie vom elektrischen HV-Energiespeicher 12 zum elektrischen LV-Energiespeicher 22 zu übertragen.

The vehicle electrical system 1 furthermore has an energy transmission device 40 , 50 who is trained to

• - in a charging mode, the charging station voltage CV into the HV vehicle electrical system voltage HV to convert and thus electrical energy from the charging station 30th for electrical HV energy storage 12th transferred to,
• - in a discharge mode, the HV vehicle electrical system voltage HV into the charging station voltage CV to convert and thus electrical energy from the electrical HV energy storage 12th to the charging station 30th to transfer, and
• - the HV vehicle electrical system voltage in a recharging mode HV into the LV vehicle electrical system voltage LV to convert and thus electrical energy from the electrical HV energy storage 12th to electrical LV energy storage 22nd transferred to.

At the in 1 conventional energy transmission device shown 40 , 50 a special "on-board charger" (OBC) 40 for charging the HV energy store 12th with electrical energy from the charging station 30th used.

The on-board charger 40 as in 1 shown two stages, namely a first voltage converter unit 42 and a second voltage converter unit 44 .

The first voltage converter unit 42 consists of an AC / DC converter and an intermediate circuit capacitor as shown C. , wherein the first voltage converter unit 42 During the charging process, a filter for power factor correction (PFC) is implemented at the same time (in addition to the AC / DC conversion). A so-called EMC filter is in the path between the charging connection 32 and the voltage converter unit 42 inserted.

The second voltage converter unit 44 is an isolated (ie providing galvanic separation) DC-DC converter which, as shown, consists of a DC / AC converter circuit, a transformer and an AC / DC converter circuit.

In the example shown is the on-board charger 40 bidirectional (as indicated by double arrows in 1 symbolized), so that the energy transfer is possible in both directions, ie also the discharge mode, often referred to as "Vehicle-to-Grid (V2G)" mode, using the on-board charger 40 can be done. Other modes such as "Vehicle-to-Device (V2D)" or "Vehicle-to-Home (V2H)" can also be implemented with it.

For "reloading", ie for charging the LV battery 22nd by means of electrical energy from the HV battery 12th , has the energy transmission device 40 , 50 also a dedicated DC / DC converter 50 on.

The DC / DC converter 50 is an isolated DC-DC converter, which consists of a DC / AC converter circuit, a transformer, and an AC / DC converter circuit as shown.

In the following description of further exemplary embodiments, the same reference symbols are used for components with the same effect. Essentially, only the differences from the exemplary embodiment (s) already described are discussed, and reference is hereby expressly made to the description of previous exemplary embodiments.

2 shows an embodiment of a vehicle electrical system according to the invention 1 , having a HV on-board power supply unit 10 with an electrical HV energy store 12th (e.g. battery) to provide HV DC voltage HV as a first vehicle electrical system voltage, and an LV vehicle electrical system part 20th with an electrical LV energy storage 22nd (e.g. battery) to provide LV DC voltage LV as a second vehicle electrical system voltage, as well as a charging connection 32 for connecting the vehicle electrical system 1 to a charging station 30th . In this respect, it differs in 2 Vehicle electrical system shown 1 not from the one related to 1 shown example.

In contrast to the conventional design, the in 2 shown example, however, a jointly used energy transmission device to accomplish the necessary energy transfers during charging, discharging and reloading 60 provided, which advantageously results in a drastic simplification of the circuitry.

The energy transmission device 60 is from a first voltage converter unit 62 , a second voltage converter unit 64 and a switch 66 educated.

The first voltage converter unit 62 can here z. B. as well as the voltage converter unit 42 of the conventional example ( 1 ) an AC / DC converter and an intermediate circuit capacitor C. and at the same time implement a PFC filter for power factor correction (PFC) during the charging process.

An EMC filter EMC is in the example of 2 also provided, but advantageously on one in the energy transmission path between the charging connection 32 and the switch 66 located place.

The second voltage converter unit 64 can also z. B. as well as the voltage converter unit 44 of the conventional example ( 1 ) have or consist of an isolated DC-DC converter which, as shown, is formed from a DC / AC converter circuit, a transformer and an AC / DC converter circuit.

The energy transmission device 60 accordingly has the bidirectional voltage converter 62 , 64 via which in a first transmission direction (in 2 from left to right) the electrical energy is transferred in charging mode, and in a second transfer direction (in 2 from right to left) the electrical energy is transferred in the discharge mode and in the transfer mode.

The switch 66 realizes a switching device, which is designed as shown, the voltage converter 62 , 64 in the charging mode and in the discharging mode on the one hand with the charging connection 32 and on the other hand with the HV on-board power supply 10 to be connected, and in reloading mode on the one hand with the HV on-board power supply 10 and on the other hand to connect to the LV on-board power supply 20.

A dedicated DC / DC converter is advantageous (see converter 50 in 1 ) is not necessary for reloading, since this functionality is in the example of 2 by means of the voltage converter units 62 and 64 in connection with the switch 66 is realized.

In 2 is also a program-controlled control device 80 (e.g. microcontroller) to control the energy transmission device 60 drawn. The control is in 2 symbolized by dashed lines.

• - Auswählen eines bestimmten Betriebsmodus des Fahr-zeugbordnetzes aus den Betriebsmodi Lademodus, Entlademodus und Umlademodus,
• - Ansteuern des Umschalters 66 derart, dass damit die dem ausgewählten Betriebsmodus entsprechende Verbindung des Spannungswandlers 62, 64 vorgesehen wird, und
• - Ansteuern des Spannungswandlers 62, 64 derart, dass damit die dem ausgewählten Betriebsmodus entsprechende Übertragung der elektrischen Energie vorgesehen wird.

By means of the control device 80 can be a method for operating the vehicle electrical system 1 take place, comprising the steps:

• - Selection of a certain operating mode of the vehicle electrical system from the operating modes of loading mode, unloading mode and reloading mode,
• - Actuation of the switch 66 such that the connection of the voltage converter corresponding to the selected operating mode 62 , 64 is provided, and
• - Control of the voltage converter 62 , 64 in such a way that the transmission of electrical energy corresponding to the selected operating mode is provided.

With reference to the 3 and 4th exemplary circuit configurations of the in 2 schematically drawn first and second voltage converter units 62 and 64 explained.

3 shows a circuit diagram of the voltage converter unit 62 , having two input connections (on the left in the figure), which have a respective throttle L1 or. L2 are connected to each of two bridge branch connections of a full bridge, that of four controllable semiconductor switches, here in the form of FETs S1 to S4 is formed, two output terminals (on the right in the figure), which are connected to a respective one of two full bridge supply terminals, and a capacitor C. with two capacitor terminals connected to a respective one of the two output terminals.

The terms “input connections” and “output connections” for the two converter sides refer to the operation of the bidirectional voltage converter unit 62 in the “first transmission direction” (from left to right in the figure), which according to the invention is provided for the charging mode.

In this case the voltage converter unit works 62 as AC / DC converter (rectifier), preferably up-converting, so that the output DC voltage is greater than the peak value of the supplied AC voltage. In the example there is a conversion from 220 V AC to 400 V DC.

If the voltage converter unit 62 however, if the "second transmission direction" is operated (from right to left in the figure), which is provided according to the invention for the discharge mode and the charge transfer mode, the "input connections" and "output connections" to a certain extent swap their roles, ie the voltage to be converted becomes at the "output connections" (right) and the voltage-converted voltage is output at the "input connections" (left).

The input connections represent a first transducer side and the output connections represent a second transducer side, the changeover switch 66 ( 2 ) is controlled by the control device in such a way that the first converter side is connected to the charging connection in the charging mode and in the discharging mode 32 is connected (or remains) and in reloading mode with the LV on-board power supply 20th connected (or remains connected). The second converter side can permanently connect to the HV on-board power supply 10 stay connected.

In the case of energy transmission in the second transmission direction (in 3 from right to left), a distinction must be made between two sub-cases, namely on the one hand operation in the unloading mode and on the other hand operation in transfer mode.

The voltage converter unit works in the discharge mode 62 as a DC / AC converter (inverter), preferably down-converting, so that the peak value of the output AC voltage is smaller than the supplied DC voltage. In the example there is a conversion from 400 V direct voltage to 220 V (50 Hz) alternating voltage.

The voltage converter unit works in recharging mode 62 as a DC / DC converter (DC voltage converter), preferably down-converting, so that the output DC voltage is lower than the supplied DC voltage. In the example there is a conversion from 400 V direct voltage to 12 V direct voltage. The AC / DC voltage converter unit, which also serves as a PFC stage in charging mode 62 is thus used as a DC / DC step-down converter in recharging mode HV on LV to walk.

• - zwei Eingangsanschlüsse (in der Figur links), die mit einem jeweiligen von zwei Vollbrückenversorgungsanschlüssen einer ersten Vollbrücke verbunden sind, die von vier FETs Si1 bis Si4 gebildet ist,
• - einen ersten Schwingkreis Lr1, Lt1, Cr1 mit zwei Drosseln Lr1, Lm, Lt1 und einem Kondensator Cr1, und mit zwei Schwingkreisanschlüssen, die mit einem jeweiligen von zwei Brückenzweiganschlüssen der ersten Vollbrücke verbunden sind (Lm in 4 repräsentiert eine Magnetisierungsinduktivität eines aus Lt1 und Lt2 gebildeten Transformators),
• - einen zweiten Schwingkreis Lr2, Lt2, Cr2 mit zwei Drosseln Lr2, Lt2 und einem Kondensator Cr2, und mit zwei Schwingkreisanschlüssen, die mit einem jeweiligen von zwei Brückenzweiganschlüssen einer zweiten Vollbrücke verbunden sind, die von vier FETs So1 bis So4 gebildet ist,
• - zwei Ausgangsanschlüsse (in der Figur rechts), die mit einem jeweiligen von zwei Vollbrückenversorgungsanschlüssen der zweiten Vollbrücke verbunden sind,

wobei die Drossel Lt1 des ersten Schwingkreises induktiv und unter Einsatz eines Magnetleitmittels (z. B. Eisenkern) mit der Drossel Lt2 des zweiten Schwingkreises gekoppelt ist, so dass diese Drosseln funktional betrachtet einen Transformator ausbilden. 4th shows the structure of the voltage converter unit 64 , having

• two input terminals (on the left in the figure) which are connected to a respective one of two full bridge supply terminals of a first full bridge, that of four FETs Si1 to Si4 is formed
• - a first resonant circuit Lr1 , Lt1 , Cr1 with two chokes Lr1 , Lm , Lt1 and a capacitor Cr1 , and with two resonant circuit connections which are connected to a respective one of two bridge arm connections of the first full bridge ( Lm in 4th represents a magnetizing inductance of an off Lt1 and Lt2 formed transformer),
• - a second resonant circuit Lr2 , Lt2 , Cr2 with two chokes Lr2 , Lt2 and a capacitor Cr2 , and with two resonant circuit connections which are connected to a respective one of two bridge arm connections of a second full bridge, those of four FETs So1 to So4 is formed
• - two output connections (on the right in the figure), which are connected to a respective one of two full bridge supply connections of the second full bridge,

being the throttle Lt1 of the first resonant circuit inductively and using a magnetic conductor (e.g. iron core) with the choke Lt2 of the second resonant circuit is coupled so that these chokes form a transformer from a functional point of view.

The designations input connections and output connections for the two converter sides are again related to the operation of the voltage converter unit 64 in the first transmission direction (in 4th from left to right), which is provided according to the invention for the charging mode. If the voltage converter unit 64 is operated in the second transmission direction (from right to left in the figure) (unloading mode and reloading mode), the input connections and output connections again to a certain extent swap their roles.

The input connections represent a first transducer side and the output connections represent a second transducer side, in which case according to FIG 2 the first converter side of the voltage converter unit 64 with the second converter side of the voltage converter unit 62 is connected and the second converter side of the voltage converter unit 64 with the HV on-board power supply 10 connected is.

The voltage converter unit 64 works in both possible energy transmission directions (first and second transmission direction) and thus in all three operating modes relevant here (charging mode, discharging mode, recharging mode) as an isolated DC / DC converter, i.e. DC / DC converter with electrical isolation between the two converter sides, for example in such a way that the output DC voltage is the same (or not significantly different from) the supplied DC voltage. In the example there is a conversion from 400 V direct voltage to 400 V direct voltage.

The control of the voltage converter unit 64 takes place so that in the first transmission direction (from left to right) the first full bridge Si1 to Si4 is controlled as an inverter to energize the transformer mentioned and the second full bridge So1 to So4 is controlled as a rectifier for rectifying an alternating current generated on the other side of the transformer in connection with the second resonant circuit.

With a view to the most efficient energy transfer possible, the two oscillating circuits including the transformer form a resonant network. It is preferably excited (e.g. by switching the FETs on and off in complementary pairs Si1 to Si4 ) with a frequency (resonance frequency) that is at least 100 kHz or even at least 200 kHz. On the other hand, it is advantageous for many applications if this frequency is a maximum of 2 MHz, in particular a maximum of 1 MHz.

A particular advantage of using a configuration like that with the voltage converter unit 64 realized, however, is that, if desired, a DC voltage upward or downward conversion (also with galvanic isolation) can be accomplished with it, in which the output DC voltage deviates from the supplied DC voltage. A control that realizes this can be useful for specific applications or specific operating states of the relevant vehicle electrical system.

In summary, both the conventional on-board charger (OBC) and the conventional "recharging device" (LV-DC / DC converter) are in one converter ( 60 ) integrated. This bidirectional converter can be used to advantage to charge an electrical HV energy storage device from the public grid via a charging station and also to feed electrical energy back into the grid (or in a house, device, vehicle, etc. equipped with an electrical energy storage device), and also to charge a LV energy store from the HV energy store (recharging mode). It can be advantageous e.g. B. a simple switch (z. B. as a semiconductor switch such as FET etc.) can be used to connect / disconnect the converter to and from the charging station (or "grid", or other electrical device) or depending on the operating mode to realize to and from the LV energy storage. Conventional OBC components can advantageously continue to be used or their functionality can be significantly improved (additional use for charging / recharging an LV battery). This leads to great savings in terms of the previous costs of the LV DC / DC converter, as well as in terms of volume and weight.

List of reference symbols

1

Vehicle electrical system

10

HV (high voltage) on-board power supply

12

HV energy storage

HV

HV vehicle electrical system voltage (first vehicle electrical system voltage)

20th

LV (low voltage) on-board power supply

22nd

LV energy storage

LV

LV vehicle electrical system voltage (second vehicle electrical system voltage)

30th

Charging station

32

Charging port

CV

Charging station voltage

EMC

EMC filter

40

Board charger (OBC)

42

first voltage converter unit

C.

capacitor

44

second voltage converter unit

50

DC / DC converter (on-board charger)

60

Energy transmission device

62

first voltage converter unit

L1

throttle

L2

throttle

S1-S4

FETs

64

second voltage converter unit

Si1-Si4

FETs

Lr1

throttle

Lt1

throttle

Cr1

capacitor

Lr2

throttle

Lt2

throttle

Cr2

capacitor

So1-So4

FETs

66

Toggle switch

80

Control device

Claims (7)

Vehicle electrical system (1), comprising - an HV electrical system part (10) with an electrical HV energy store (12) for providing an HV direct voltage (HV), - an LV electrical system part (20) with an electrical LV energy store (22) for providing a LV DC voltage (LV), - a charging connection (32) for connecting the vehicle electrical system (1) to a charging station (30), which has a charging station voltage (CV) for transferring electrical energy between the charging station (30) and the Vehicle electrical system (1) provides - an energy transmission device (60) which is designed to - convert the charging station voltage (CV) into the HV vehicle electrical system voltage (HV) in a charging mode and thus convert electrical energy from the charging station (30) to the electrical HV - to transfer energy storage (12), - to convert the HV on-board electrical system voltage (HV) into the charging station voltage (CV) in a discharge mode and thus to transfer electrical energy from the electrical HV energy storage device (12) to the charging station (30) - to convert the HV vehicle electrical system voltage (HV) into the LV vehicle electrical system voltage (LV) in a recharging mode and thus transfer electrical energy from the electrical HV energy store (12) to the electrical LV energy store (22), characterized in that the energy transmission device (60) has: - a bidirectionally operable voltage converter (62, 64), via which the electrical energy is transmitted in the charging mode in a first transmission direction, and the electrical energy is transmitted in the discharging mode and in the recharging mode in a second transmission direction, - A switching device (66) which is designed to connect the voltage converter (62, 64) in the charging mode and in the discharging mode, on the one hand, to the charging connection (32) and, on the other hand, to the HV on-board power supply unit (10), and, in the charging mode, to the HV on-board power supply (10) and on the other hand to connect to the LV on-board power supply (20). Vehicle electrical system (1) according to Claim 1 , wherein the voltage converter (62, 64) has a first converter side and a second converter side, the switching device (66) being designed to connect the first converter side to the charging connection (32) in the charging mode and in the discharging mode and to the LV in the charging mode -Board power supply (20) to connect, and wherein the second converter side is connected to the HV on-board power supply (10). Vehicle electrical system (1) according to one of the preceding claims, wherein the voltage converter (62, 64) has a first voltage converter unit (62) which, viewed in the first transmission direction, has: - two input connections, which are connected via a respective choke (L1, L2) to a respective one of two bridge branch connections of a full bridge, - the mentioned full bridge with four controllable semiconductor switches (S1 to S4), - two output ports connected to a respective one of two full bridge supply ports, - optionally a capacitor (C) with two capacitor connections which are connected to a respective one of the two output connections. Vehicle electrical system (1) according to one of the preceding claims, wherein the voltage converter (62, 64) has a second voltage converter unit (64) which, viewed in the first transmission direction, has: - two input connections that are connected to a respective one of two full bridge supply connections of a first full bridge, - the mentioned first full bridge with four controllable semiconductor switches (Si1 to Si4), - A first resonant circuit (Lr1, Lm, Lt1, Cr1) with at least one choke (Lr1, Lm, Lt1) and at least one capacitor (Cr1), and with two resonant circuit connections which are connected to a respective one of two bridge arm connections of the first full bridge, - a second resonant circuit (Lr2, Lt2, Cr2) with at least one choke (Lr2, Lt2) and at least one capacitor (Cr2), and with two resonant circuit connections, which are connected to a respective one of two bridge arm connections of a second full bridge, - the mentioned second full bridge with four controllable semiconductor switches (So1 to So4), - Two output connections which are connected to a respective one of two full bridge supply connections of the second full bridge, the choke (Lt1) of the first resonant circuit being inductively coupled to the choke (Lt2) of the second resonant circuit. Vehicle electrical system (1) with the features of Claims 3 and 4th , the first voltage converter unit (62) and then the second voltage converter unit (64) being arranged in the first transmission direction. Vehicle electrical system (1) according to one of the preceding claims, further comprising a program-controlled control device (80) for controlling the energy transmission device (60). Method for operating a vehicle electrical system (1) according to one of the preceding claims, comprising - Selecting a specific operating mode of the vehicle electrical system (1) from several operating modes which include the charging mode, the discharging mode and the reloading mode, - controlling the switching device (66) in such a way that the connection of the voltage converter (62, 64) corresponding to the selected operating mode is provided, - Control of the voltage converter (62, 64) in such a way that the transmission of electrical energy corresponding to the selected operating mode is provided.

Images