CN112041193B - Method for transmitting electric power to an electric energy store of an on-board electrical system, and on-board electrical system - Google Patents

Abstract

The invention relates to a method for transmitting electric power to an electric Energy Store (ES) of a vehicle electrical system (BN), wherein in an alternating current direct charging mode, power is transmitted directly from a rectifier (GR) of the vehicle electrical system (BN) to the Energy Store (ES) of the vehicle Electrical System (ES), the rectifier being supplied by an alternating current charging connection (ACLB). In the ac-adapted charging mode, power is transferred from the rectifier (GR) through the inverter (I) and from the inverter (I) through the motor (EM) to the Energy Store (ES). Furthermore, a vehicle-mounted electrical system (BN) for carrying out the method is described.

Description

Method for transmitting electric power to an electric energy store of an on-board electrical system, and on-board electrical system

Technical Field

A motor vehicle with an electric drive has an electric energy store in the form of a traction battery, which supplies the electric drive with electric power. For charging the energy store, a charging connection is provided on such a motor vehicle. An external energy source can be connected via the charging connector.

Background

In order to control the charging of the energy store, power electronics are installed in the motor vehicle. Because power electronics are designed for high powers of more than 10kW or more than 100kW and, furthermore, different and correspondingly changing voltage levels on the charging connection and the energy store have to be overcome, very high costs are incurred for the power electronics.

Disclosure of Invention

The object of the invention is therefore to specify a possibility for transmitting electrical power to an energy store of an on-board electrical system at a lower cost.

This object is achieved by the subject matter of the independent claims. Further embodiments, features and advantages are obtained with the aid of the dependent claims, the description and the accompanying drawings.

It is proposed that a rectifier is provided for transmitting an alternating current between the alternating current charging connection and an energy store of the vehicle electrical system, which rectifier is connected to the alternating current charging connection. Depending on the voltage levels on the rectifier side of the rectifier and on the energy store, the power output by the rectifier is either directly (in particular without transformation) transferred to the energy store or it is transferred to the energy store via the converter and the (i.e. downstream) motor connected thereto. In direct transmission, the loss of power is only generated in the rectifier (and not in the inverter), whereas in transmission through the inverter and the motor (and through the preceding rectifier), these two components can be operated as direct current transformers, so that different voltage levels between the rectifier and the energy store can be compensated. Thus, in the alternating current direct charging mode, power is directly transferred, and in the alternating current adaptive charging mode, power is directed between the rectifier and the energy storage through an Inverter (Inverter) and the motor. In both modes, in particular, a power factor correction filter (PFC filter) is implemented in the rectifier. Furthermore, in both modes, rectification is implemented in the rectifier. In the ac-fitted charging mode, boost conversion (Aufwaertswandlung) is preferably not implemented in the rectifier. In the alternating current direct charging mode, boost conversion is preferably performed, especially beyond voltage boost for performing power factor correction filtering. In the case of the pfc filter, the voltage can be increased slightly, in particular by no more than 5%, 7%, 10%, 15%, in order to carry out the filtering. This is understood to be a voltage rise which is required in order to implement the pfc filtering. Boost conversion overrides this voltage boost and is associated with a boost in voltage that is no greater than the voltage boost in PFC filtering, for example with a boost greater than 5%, 7%, 10%, 15% and preferably at least 50%, 100%, 150% or 200%. The step-up or voltage step-up is related to the output voltage of the rectifier, which is related to the peak-to-peak value of the voltage on the ac connection (if necessary interconnected).

Depending on the ratio of the voltage levels between the rectifier and the energy storage, an alternating current direct charging mode or an alternating current adapted charging mode is implemented. It is thus possible to take into account the voltage level of the energy store (which changes during charging) and the different voltages or connections at the ac power connection, since the ac power connection (depending on the charging station) can be single-phase or multi-phase.

A method for transmitting electrical power to an electrical energy store of an on-board electrical system is described. The electrical energy store is preferably a battery, for example a traction battery, which may in particular be a lithium battery. The electrical energy store is in particular a high-voltage accumulator. The electric power is transmitted from the charging station or from another source of electrical energy to outside the vehicle electrical system. However, it is also possible to transmit power in the opposite direction. The on-board electrical system is in particular a high-voltage on-board electrical system. By the term "high voltage" is meant a rated voltage above 60V, in particular a rated voltage of at least 120V, 300V, 350V, 380V or at least 450V or 600V, for example 380V, 400V or 800V.

In the direct ac charging mode, power is transferred directly from the rectifier (especially from the dc side thereof) to the energy storage. In this relationship, "direct" means that no transformation is performed between the energy storage and the rectifier. The rectifier may be an uncontrolled rectifier, but preferably may be a controlled rectifier, which preferably has the function of performing a power factor correction filtering (on the ac side of the rectifier or on the charging connection), wherein in particular the power factor is amplified and/or harmonic components are reduced. The rectifier is supplied by an ac charging connection of the vehicle electrical system. The ac charging connection is connected to the rectifier, in particular to the ac side of the rectifier. It may be provided that in addition to the rectification, the rectifier may also carry out (direct current) boost conversion, in particular boost conversion that exceeds a voltage boost that depends on PFC filtering. The rectifier can thus be provided for carrying out a boost conversion which results in a voltage whose level is significantly above the peak-to-value voltage of the (optionally interconnected) ac voltage on the ac charging connection. An elevation of no more than about 5%, 7%, 10% or 15% is not considered a significant elevation. The insignificant increase is due to PFC filtering and not to boost conversion (in the ac direct charge mode).

As a boost conversion, the peak-to-peak voltage rise of the rectified voltage relative to the (optionally interconnected) ac voltage on the ac charging connection is exceeded, in particular by more than the voltage rise associated with PFC filtering. In particular, the boost conversion is preferably carried out by the controller of the switching of the PFC-capable rectifier without a voltage transformation by a specific transformer (DC/DC converter) downstream of the rectifier circuit. Boost conversion is implemented in particular in the ac direct charging mode and not in the ac adaptive charging mode (in which only the voltage boost associated with PFC function is implemented). The rectifier is therefore equipped with, inter alia, a boost function (corresponding to boost conversion). This function may be implemented in an ac direct charging mode and not operate in an ac adaptation mode. In the ac-adapted mode, the inverter and the motor operate as Buck converters (abwartswandler preset difference, buck converters).

In the ac-adapted charging mode, power is transferred from the rectifier through the inverter and through the motor to the energy storage. The converter, in particular the rectifying side thereof, is connected to the rectifying side of the rectifier. The ac side of the inverter is connected to the motor, in particular to the phase or winding connections of the motor. Power is thus transmitted from the inverter through the motor to the energy storage. In this case, the power is transmitted via at least one winding or along at least one winding section of the electric machine. In particular, the power can be transmitted via the electric machine by feeding it in at least one phase connection of the electric machine and outputting it from the (opposite) star point. The phase connection is also called an external phase connection. Power is transferred through the inductance of at least one winding (or winding section) of the motor.

In the transmission of power through an inverter and a motor connected thereto, the inverter and the motor are operated together as a Buck converter (Buck converter) or as a synchronous converter in Buck converter mode. In this case, the at least one power switch of the converter forms at least one switch of the buck converter during operation of the at least one winding of the motor as an inductance of the buck converter. The inverter and the motor may constitute a (separate or cascaded) buck converter.

The inverter or at least one power switch thereof is controlled so as to constitute a buck-converted dc voltage converter together with at least one winding of the motor. The buck-converted direct current voltage converter is also referred to as buck-converted DC/DC converter. The nominal voltage for the voltage level output at the motor (i.e. the voltage at the at least one internal phase connection or star point) may be preset, for example, by a charge controller, which may be preceded by a controller of the power switch of the inverter. When the motor and inverter are operated together as a dc voltage converter, the star point, i.e. the internal phase connection, can be released from each other (all connections or a subset thereof).

A switching device may be used to select one mode from at least two possible modes (alternating current direct charging mode or alternating current adaptive charging mode). In the direct ac charging mode, the switching device connects the rectifier and the energy store in particular in a direct manner (i.e. without voltage conversion). The switch of the switching device transmits power here. In the ac-adapted charging mode, the switching device connects the rectifier with the inverter or establishes a power path leading through the inverter and the motor. For this purpose, a further switch of the switching device can be provided for this purpose, which switch transmits power. The further switch and the first-mentioned switch preferably together form a switching device. The two switches are alternately closed, i.e. when one switch is closed, the other switch is open. In the inactive mode, both switches may be open.

The rectifier rectifies the power in at least one of the alternating current charging modes, preferably in the alternating current direct charging mode and in the alternating current adapted charging mode. The rectifier is in particular a controlled rectifier. In addition, the rectifier performs a power factor correction filter function (PFC function, i.e., power factor correction function), in particular on the ac side of the rectifier. Where the power factor is increased, the harmonic component is reduced, or both. The rectifier may be configured as a Vienna rectifier. For performing the power factor correction filtering, the rectifier (for each phase) comprises at least one energy-storing structural element, such as a coil or a capacitor. The energy-storing structural element can be arranged in series with the phase connection of the rectifier (on the ac side), for example in the form of a series inductance (for each phase). Alternatively or additionally, the energy-storing structural elements may be connected in parallel with different phase connections, for example in a delta configuration or a star configuration. The energy-storing structural elements are designed as parallel capacitors, with the phase connections being connected to one another by means of the parallel capacitors. Thus, the rectifier may be configured for power correction filtering, or to implement power correction filtering (PFC, i.e., power factor correction). The power correction filtering may be equivalent to the herein-mentioned change in power factor or increase in power factor and decrease in harmonic component.

The converter may be a controlled full wave bridge, such as a multiphase BnC bridge, having in particular a plurality of phases, where n corresponds to twice the number of phases. The converters may be designed as B6C bridges. Furthermore, the converter may be designed as one or more H-bridges.

The converter and/or rectifier may comprise semiconductor switches, such as MOSFETs or IGBTs or diodes. The semiconductor switch is a power switch.

In the ac-fitted charging mode, power may be transmitted from the motor to the energy store via a filter, in particular via a filter which is arranged downstream (seen from the inverter) of the motor or between the motor and the energy store.

In the ac-adapted charging mode, the converter may operate as a buck-converted dc voltage converter (simply buck converter). In the ac-fitted charging mode, the converter may in particular be operated as a buck converter together with at least one winding of the electric machine. Furthermore, in the ac-adapted charging mode, the converter may operate as a switch of a buck converter generated by combining the converter and the motor (and corresponding controller). Only a part of all power switches of the converter are used in particular for implementing the switches of the buck converter. The buck converter thus formed can convert the dc voltage output by the rectifier into a further lower dc voltage. In the ac direct charging mode, the inverter may be deactivated. In the alternating current direct charging mode, all switches of the converter are in particular open. In the ac-adapted charging mode, the dc voltage formed by rectification (and PFC filtering) is matched to the (lower) voltage level on the battery in order to avoid excessively high currents, which are thus caused by a strong voltage drop between the rectified ac voltage and the energy store voltage.

The voltage output by the inverter or the motor may be filtered by means of a filter. The filter is then arranged downstream of the motor and is connected in particular to the star point or to a phase connection (switchlessly) inside the motor.

In addition, a dc voltage charging mode may be set. In this mode, power (which is present as a dc/dc voltage) is transferred directly (i.e., without voltage conversion) from the dc charging connection to the energy storage. Alternatively and in combination therewith, a dc voltage-adapted charging mode may be provided, wherein power is transmitted from the dc charging connection to the energy store via the dc voltage converter. The dc voltage converter may be a defined dc voltage converter for dc voltage charging or may be formed by an inverter and a switch of the motor. In the last-mentioned case, power is transmitted from the dc charging connection via the motor to the converter and from there to the energy store. The switch (which connects the energy store directly to the dc charging connection) is open in the dc voltage adapted charging mode and closed in the dc voltage charging mode (which may also be referred to as direct dc voltage charging mode).

Finally, a driving mode or a recuperation mode can be set, in which the energy store is connected to the electric machine via an inverter. In this case, the power is transmitted from the energy store to the electric machine via the converter and is converted there from the electric machine into mechanical power (traction mode), or the power is generated in the electric machine starting from the mechanical power and is transmitted via the converter to the energy store. In the driving mode and in the recuperation mode, the rectifier is deactivated and in particular has an open power switch.

There may be a feedback mode (in which power may be transferred from the electric energy storage to at least one of the charging contacts), for example a first feedback mode in which power is transferred from the energy storage directly through the (controllable) rectifier to the ac charging contact (where the rectifier is subsequently commutated), a second feedback mode in which power is transferred from the energy storage through the electric machine and the inverter connected thereto and through the (controllable) rectifier to the ac charging contact (where the rectifier is subsequently commutated and the inverter converts the dc voltage), or a third feedback mode in which power is output from the energy storage to the dc voltage charging contact.

The rectifier may operate in a rectifier mode in which the voltage present at the ac charging connection is rectified only and subjected to PFC filtering, wherein the rectifier does not perform voltage conversion (which is associated with PFC filtering). In other words, the rectifier does not perform boost conversion, but rather only performs voltage boosting associated with PFC filtering if necessary, for example boosting by no more than 5%, 7%, 10% or 15%. In this mode, a rectified voltage is produced by an active and optionally interconnected ac voltage on the ac charging connection and, if necessary, by an insignificant voltage rise associated with PFC filtering. The rectifier can be provided for operation also in a rectified voltage conversion mode in which it rectifies the voltage present at the ac voltage charging connection and in addition carries out a boost conversion that exceeds (not significantly) the voltage increase caused by PFC filtering. In order to be able to carry out a boost conversion (notably, i.e. exceeding 5%, 7%, 10% or 15%) the rectifier has at least one energy-storing structural element, such as at least one capacitor or at least one inductance, as described above.

The rectifier has in particular a power factor correction function (Power Factor Correction, PFC). The power factor correction function is implemented by means of at least one energy-storing structural element. The boost conversion is thus implemented with the components of the rectifier that are also used to implement the power factor correction function. The boost conversion and/or power factor correction functions are implemented and controlled by switching the semiconductor switches of the rectifier according to parameters such as duty cycle, switching phase, phase offset and frequency.

In an embodiment, in the ac direct charging mode, the rectifier performs boost conversion (as well as rectification and PFC filtering). The converter is deactivated here, in particular because the power is directed from the rectifier directly to the energy store. The ac direct charging mode is for example adjusted when the peak-to-peak voltage (corresponding to the square root of two times the effective value of the voltage) at the ac charging connection does not exceed a preset difference (margin) below the voltage of the energy store. This applies in particular to the occupation of a single phase of an ac charging connector. In addition, the ac direct charging mode may be adjusted when the peak-to-peak-value of the voltage of the interconnect on the ac charging connector (corresponding to the square root of two times the voltage of the interconnect on the ac charging connector) does not exceed a preset difference below the voltage of the energy storage.

Thus, in the case of a single-phase occupation of the ac charging connection in a voltage of the energy store of more than 325V or 350V and in a network voltage of 230V of the ac voltage available, for example, the ac direct charging mode can be set. The rectifier also operates as a boost chopper (boost converter), i.e. boost is implemented, so that the voltage output by the rectifier is higher than the voltage generated in pure rectification and pure PFC filtering without (significant) boost conversion.

When charging (corresponding to a three-phase occupation of the ac charging connection) with, for example, a three-phase current (with a star-shaped adaptation of the effective ac voltage of 230V or of the interconnecting about 400V) and the voltage of the energy store exceeds 600V, 620V or 650V or 670V, an ac direct charging mode is likewise implemented, in which the rectifier performs a boost conversion function in addition to the functions of rectification and power factor correction and outputs power directly to the energy store (not by means of an inverter/motor).

It may furthermore be provided that in the ac-fitted charging mode, the rectifier does not carry out a boost conversion and only carries out a rectification and carries out a PFC function. The converter is activated here and performs a buck conversion together with at least one winding inductance of the motor. The power is led by the rectifier through the inverter and the motor (in this sequence) to the energy storage. An ac-adapted charging mode is for example adjusted when the peak-to-peak voltage (corresponding to the square root of two times the effective value of the voltage) on the ac charging connection does not exceed a preset difference above the voltage of the energy storage. This applies in particular to the occupation of a single phase of an ac charging connector. In addition, the ac direct charging mode may be adjusted when the peak-to-peak-value of the voltage of the interconnect on the ac charging connector (corresponding to the square root of two times the voltage of the interconnect on the ac charging connector) does not exceed a preset difference above the voltage of the energy storage. Thus, in the case of a single-phase occupation of the ac charging connection in the active ac voltage of the energy store of no more than 325V or 350V and in the active network voltage of the ac voltage of 230V, for example, an ac-adapted charging mode can be set. The rectifier here operates only as a rectifier (and PFC filter) and does not operate as a boost chopper (boost converter), i.e. does not carry out a boost (which exceeds the voltage rise caused by PFC filtering). The voltage output by the rectifier thus corresponds to the voltage generated in pure rectification without boost conversion (including PFC filtering). When charging (corresponding to a three-phase occupation of the ac charging connection) with, for example, a three-phase current (star-shaped adaptation with an alternating current of about 400V with 230V or an interconnection) and the voltage of the energy store does not exceed 600V, 620V, 650V or also 670V, an ac-adapted charging mode is likewise implemented, in which the rectifier only performs the functions of rectification and PFC filtering and does not perform the function of boost conversion. The rectifier outputs power to the energy store not directly here, but via an inverter/motor which reduces the voltage level. The converter and the motor are here adapted to the rectified voltage regulation by means of buck conversion.

Furthermore, an on-board electrical system having an ac charging connection and a rectifier is described. The on-board electrical system and its components correspond in particular to the on-board electrical system and components by means of which embodiments of the method and the method are described. The rectifier is optionally connected either directly to the electrical energy store by means of a switching device, wherein this corresponds to an alternating current direct charging mode, or to the electrical energy store by means of an inverter and a motor, wherein this corresponds to an alternating current adaptation charging mode. The switching device is thus provided for selecting two power paths (starting from the rectifier) which lead to the energy store. One power path is direct and the other power path leads through the inverter and the motor connected thereto. The current converter is connected with the electric energy accumulator through the motor. The inverter is connected between the rectifier and the motor. Starting from the rectifier, the motor is placed after the converter. A motor is connected between the energy accumulator and the current converter. The internal phase connection (or at least one of them) of the motor is connected to an energy store. The external phase joint of the motor is connected with the energy accumulator. The star point, at least one internal phase connection or the star point-side end of at least one winding or all windings of the electrical machine are connected to an energy store.

This enables either direct charging or charging by means of a converter and a motor arranged downstream of the converter, which together may represent a buck-converted direct voltage converter (buck converter). The at least one power switch of the converter forms at least one switch of the buck converter, while the at least one winding or a section thereof forms the inductance of the buck converter. At least one subset of the converters or power switches of the converters is configured to also operate as switches of the buck converter.

The rectifier is configured to rectify the alternating current transmitted through the alternating current charging connector. Furthermore, a rectifier is provided for PFC filtering, wherein in particular the power factor of the power transmitted via the ac charging connection increases and the harmonics decrease. Furthermore, a rectifier is provided for adjustable boost conversion of the voltage. The rectifier can be configured as a Vienna rectifier as previously mentioned. The rectifier is also designed in particular to implement a power correction filter. For this purpose, the rectifier has at least one energy storage component, such as a coil or a capacitor. In other words, the rectifier is equipped with a power correction filter, or at least with a function of power correction filtering or changing the power factor. The power correction filter element is furthermore used to implement the boost conversion function of the rectifier. For this purpose, the rectifier has, as already mentioned, in particular at least one energy-storing element, such as an inductance or a capacitor. As at least one energy-storing element for constructing the boost converter function, the same at least one energy-storing element is preferably used, with which the PFC filter function of the rectifier is implemented. The rectifier is arranged to implement an ac-adapted charging mode and an ac direct charging mode. In particular, the control unit and the rectifier are together arranged for implementing an ac-adapted charging mode and an ac direct charging mode. The control unit is arranged to either adjust out an ac-adapted charging mode or adjust out an ac direct charging mode (or other modes).

As mentioned, the rectifier may be provided for operation as a boost converter in at least one operating mode, in particular in an alternating current direct charge mode. It may furthermore be provided that the rectifier does not operate as a boost converter in the ac-fitted charging mode (except for a voltage increase of, for example, not more than 5%, 7%, 10% or 15% which is not significantly caused by the PFC function). The rectifier may in particular have components which are designed to rectify at least 50%, 100%, 150% or 200% of the voltage above the nominal peak-peak voltage on the ac power connection (if necessary taking into account the relevant interconnection factors).

The motor may be connected to the electrical energy storage via a filter. The filter may be placed later in the switch (from the motor perspective) of the switching device. The filter is connected in particular directly, i.e. without a switch, to the motor, in particular to at least one internal phase connection.

The on-board electrical system may furthermore have a direct current charging connection. The direct current charging connection is preferably connected to the energy store via at least one switch. The direct current charging connector is not connected to the energy store via a filter, the energy store being connected to the motor (or downstream of the motor) if necessary.

The on-board electrical system may furthermore have a control device, which was also referred to as a controller for short. The control means is controllably connected with the switching device and the converter. The control device may be divided and/or comprise parts controlling the switching devices in multiple pieces and/or in stages, including further parts controlling the converters or their power switches, and may furthermore have a superordinate control unit. However, the hierarchy or division of the control devices may be varied and will not be discussed in detail below. The control device is arranged to control the switching device in an alternating current direct charging mode, connecting the alternating current charging connection directly to the energy store. The control device is furthermore provided for controlling the switching device in an ac-adapted charging mode, connecting the ac charging connection with the converter. In this mode, the control means are arranged to control the inverter to operate as a direct voltage converter together with at least one winding of the motor. The switching device is especially arranged for switching the converter inactive in an alternating current direct charging mode, i.e. all switches of the converter are arranged in an open state.

The control device may furthermore be configured to set the two switches of the switching device open in the dc charging state and to set the switch connecting the dc charging connection to the energy store closed.

The switching device may have a first switch, which connects the rectifier with the energy store. The switching device may have a second switch arranged between the energy storage and a connection connecting the rectifier and the converter. The second switch is arranged in particular between the motor and the energy store or connects the two components. The second switch may be arranged in particular at the star point of the electric machine (or at the phase connection inside it), and may connect the star point or the phase connection inside it to the energy store. In the alternating current charging mode, the first and second switches are alternately opened or closed.

In an alternative embodiment, the switching device comprises only the first switch, while the second switch is implemented by a switch of the converter. In this case, the power path leading through the converter or the motor (and for transmission in the ac-adapted charging mode) is opened or closed by the switch of the converter itself, whereas the path leading directly from the rectifier to the energy store is opened or closed by the first switch. The control device is configured for alternately opening or closing the first switch on the one hand and the switch of the inverter on the other hand in an alternating current charging mode. The control device may be configured to control the first switch to be closed in the alternating current direct charging mode and to control the switch of the converter to be open and to control the first switch to be open in the alternating current adaptive charging mode and to control the switch of the converter to be closed. Instead of controlling all switches of the converter to be closed, it is also possible to control a subset of the full bridges to be closed or to control only one full bridge of the converter to be closed.

Drawings

The onboard electrical system described here is designed to carry out the method. The method uses the described components of the on-board electrical network. Fig. 1 shows an overview for explaining an onboard electrical system or method in more detail.

Detailed Description

The symbolically represented on-board electrical system BN comprises an energy store ES (in the form of a traction battery) and a converter I, which is connected to the energy store ES via a first switch B1. On the opposite side, the motor M is connected to an inverter. The motor M has in particular a plurality of phases and can be designed as a permanently excited, self-excited or other excited motor, for example as a synchronous motor or can be an asynchronous motor.

The motor M has a star point SP. The star point is located on the inner phase joint of the motor. The star point SP may be designed to be separable.

From the inverter I, the second switch S1 is placed downstream of the motor. The second switch S1 connects the electric machine M (in particular its star point SP or at least one internal phase connection of the electric machine EM) to the energy store, in particular directly, i.e. without changing the voltage. An optional filter F may be provided, which is located between the motor M and the energy store ES, in particular between the second switch S1 and the energy store.

The ac charging connection ACLB (designed for example as a charging socket) is connected to the first switch B1 and to the converter I via a rectifier GR. The first switch B1 and the converter I (in particular the dc voltage side thereof) are connected to the dc voltage side of the rectifier GR. The ac charging connection ACLB is connected to an ac power network CAN, which is located outside the vehicle electrical system and CAN be arranged in the charging station LS. The ac power network ACN comprises an ac power source. The rectifier GR has the function of a power factor correction filter (in addition to the rectification function) so that the power factor present at the ac charging connection ACLB can be regulated and in particular (relative to the use of a rectifier without PFC function) increased.

If the first switch B1 is closed and the second switch S2 is open, the rectifier GR is directly connected to the energy store ES. This corresponds to an alternating current direct charge mode. If the first switch B1 is open and the second switch S2 is closed, the rectifier GR is connected to the energy store ES via the converter I and the motor M (in this order). The converter and the motor together are operated as a (in particular buck) dc transformer as mentioned at the outset. The optional filter F enables suppression of switching pulses in the vehicle electrical system BN, which are generated by switching processes in the converter I when operating as (a switching unit of) a dc transformer.

The ground switch B2 switchably connects the energy store to a negative supply potential of the on-board electrical system. The previously mentioned switches B1 and S2 and switch B3 are arranged in the positive supply potential rail. The battery separation switch B3 is provided between the filter and the accumulator ES. The switches B2 and B3 are set to be closed in the alternating current charging mode and can be set to be open in the event of a fault or in an inactive on-board electrical system.

The optional direct voltage charging connector DCLB enables a connection of the on-board electrical system BN to a direct current network DCN, which is located outside the on-board electrical system BN. The direct current network DCN may be part of the charging station LS. The dc voltage charging connection DCLB is connected to the energy store via a dc voltage switch S2 (and via a switch B3). The connection between the switch S2 and the energy store ES is direct, i.e. without a transformer. However, for voltage level adaptation, a dc transformer may be downstream of the dc voltage charging connection DCLB. An alternative (or additional) connection between the dc voltage charging connection DCLB and the energy store ES is routed via the switch C1. The switch C1 connects the dc voltage charging connection DCLB and the energy store ES. If the switch is closed, power may be transferred directly from the dc voltage charging connection DCLB to the energy store ES.

A control device CT, which is schematically shown, is connected in a controlled manner to the switches B1 and S1. As mentioned, the control device CT alternately controls the switches B1 and S1 in the alternating-current charging mode. For this reason, the switches B1 and S1 form a switching device (by alternating control). The control device CT is furthermore connected in a controlled manner to the switches S2, B3 and C1 (if present), which are closed during the alternating current charging, while the switches S1, B1 are open. The control device CT is furthermore connected in a controlled manner to the switches S2 and B3 or C1 in order to control them to be closed in contrast to the switches B1 and S1 when the direct current charging mode is present. The control device can furthermore be connected in a controlled manner to the rectifier GR and to the converter I. When the switch S1 is not provided, instead of the switch, the switch of the inverter I may be opened or closed by the control device, for example, when switching between alternating current charging modes. The control device CT is provided via a controllable connection to the rectifier GR for regulating the power factor present at the ac charging connection ACLB by the rectifier and for filtering or attenuating harmonics. As mentioned, the control device CT can be constructed in multiple parts or in stages. The control device CT may furthermore have an input for inputting the nominal operating mode. The control unit can furthermore be configured to implement a traction mode or a recuperation mode, as described at the outset.

Optional or alternative components or connections are shown in phantom, dotted or dash-dot lines.

Claims (12)

1. Method for transmitting electric power to an electric Energy Store (ES) of a vehicle electrical system (BN), wherein in an alternating current direct charging mode power is transmitted directly from a rectifier (GR) of the vehicle electrical system (BN) to the Energy Store (ES) of the vehicle Electrical System (ES), which rectifier is supplied by an alternating current charging connection (ACLB), and in an alternating current adaptive charging mode power is transmitted from the rectifier (GR) via an inverter (I) and from the inverter (I) via a motor (EM) to the Energy Store (ES), wherein the rectifier (GR) rectifies the power and implements a power factor correction filter function in the two alternating current charging modes, wherein in the alternating current adaptive charging mode no boost conversion is implemented in the rectifier (GR) and in the alternating current direct charging mode a boost conversion is implemented in the rectifier (GR) that exceeds the voltage boost caused by the power factor correction filter.

2. Method according to claim 1, wherein in the alternating current direct charging mode a switching device (B1, S1) connects the rectifier (GR) with the Energy Store (ES), and in the alternating current adapted charging mode the switching device (B1, S1) connects the rectifier (GR) with the inverter (I).

3. Method according to claim 1 or 2, wherein in the ac-adapted charging mode power is transferred from the motor (EM) to the Energy Store (ES) through the filter (F).

4. Method according to claim 1 or 2, wherein in an ac-adapted charging mode the converter (I) operates as a dc voltage converter and converts the dc voltage output by the rectifier (GR) to a lower dc voltage.

5. Method according to claim 1 or 2, wherein in the direct voltage charging mode power is transferred from the direct current charging connection (DCLB) directly to the Energy Store (ES).

6. Vehicle electrical system for carrying out the method according to any one of claims 1 to 5, having an alternating current charging connection (ACLB) and a rectifier (GR), wherein the Rectifier (RG) is selectively connectable either directly to an electrical Energy Store (ES) by means of a switching device (B1, S1) or to the electrical Energy Store (ES) by means of an inverter (I) and a motor (EM), wherein the inverter (I) is connected to the electrical Energy Store (ES) by means of the motor (EM).

7. The on-board electrical system according to claim 6, wherein the rectifier (GR) is configured for rectifying an alternating current transmitted through an alternating current charging connection (ACLB) and is configured as a power factor correction filter for a power transmitted through an alternating current charging connection (ACLB).

8. The onboard electrical system according to claim 6 or 7, wherein the electric machine is connected to an electrical Energy Store (ES) via a filter.

9. The on-board electrical system according to claim 6 or 7, further comprising a direct current charging connector (DCLB) which is connected to the Energy Store (ES) via a switch (S2; B3; C1).

10. The on-board electrical system according to claim 6 or 7, further having a control device (CT) which is controllably connected to the switching devices (B1, S1) and to the converter (I), wherein the control device (CT) is provided for controlling the switching devices (B1, S2) in an alternating current direct charging mode, for directly connecting the rectifier (GR) to the Energy Store (ES), and the control device (CT) is further provided for controlling the switching devices (B1, S2) in an alternating current adaptive charging mode, for connecting the rectifier (GR) to the converter (I), and for controlling the converter (I) such that the converter and at least one winding of the motor (M) together operate as a direct current voltage converter.

11. The onboard electrical system according to claim 10, wherein the control device (CT) is arranged for controlling the converter (I) in an ac-adapted charging mode such that the converter and at least one winding of the motor (M) together operate as a buck converter.

12. The on-board electrical system according to claim 6 or 7, wherein the rectifier (GR) is provided for operating as a boost converter in at least one operating mode.