CN112041193A - Method for transmitting electric power to an electrical energy store of a vehicle electrical system and vehicle 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), which is supplied with electric power by an alternating current charging connection (ACLB), to the electric Energy Store (ES) of the vehicle Electrical System (ES). In the alternating current adaptive charging mode, power is transmitted from the rectifier (GR) through the converter (I) and from the converter (I) through the Electric Machine (EM) to the Energy Storage (ES). Furthermore, an onboard electrical system (BN) for carrying out the method is described.

Description

Method for transmitting electric power to an electrical energy store of a vehicle electrical system and vehicle electrical system

Technical Field

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

Background

In order to control the charging of the energy store, power electronics are installed in the motor vehicle. Since the power electronics are designed for high powers of more than 10kW or more than 100kW and, furthermore, different and correspondingly changing voltage levels at the charging connection and the energy storage must be overcome, high costs for the power electronics result.

Disclosure of Invention

The object of the present invention is therefore to specify a possibility which makes it possible to transfer electrical power to an energy store of an on-board electrical system at reduced cost.

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

It is proposed that a rectifier is provided for transmitting the 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 level on the rectifier side of the rectifier and on the energy store, the power output by the rectifier is either transmitted directly (in particular without a voltage transformation) to the energy store or transmitted via the inverter and the electric machine connected thereto (i.e. downstream) to the energy store. In direct transmission, the power loss is only generated in the rectifier (and not in the inverter), whereas in transmission through the inverter and the electric machine (and through the preceding rectifier), these two components can be operated as a dc transformer, so that different voltage levels between the rectifier and the energy store can be compensated for. In the ac direct charging mode, power is therefore transmitted directly, and in the ac adaptive charging mode, power is conducted between the rectifier and the energy store via the Inverter (Inverter) and the electric machine. In both modes, a power factor correction filter (PFC filter) is implemented in particular in the rectifier. In addition, in both modes, rectification is implemented in the rectifier. In the ac adaptive charging mode, no step-up conversion (aufwaterswandlung) is preferably implemented in the rectifier. In the direct ac charging mode, a step-up conversion is preferably carried out, in particular beyond the step-up conversion of the voltage used for carrying out the power factor correction filtering. In the power factor correction filtering, the voltage can be slightly increased, in particular by not more than 5%, 7%, 10%, 15%, in order to implement the filtering. This is understood to be a voltage increase, which is required for implementing the power factor correction filtering. The boost conversion exceeds this voltage rise and is associated with a rise in voltage no greater than the voltage rise in PFC filtering, for example greater than 5%, 7%, 10%, 15% and preferably at least 50%, 100%, 150% or 200% rise. 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 (interconnected if necessary) at the alternating current connection.

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 account of the voltage level of the energy store (which changes during charging) and the different voltages or connection conditions at the ac terminals, since the ac terminals (depending on the charging station) can be in a single phase or in multiple phases.

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

In the ac direct charging mode, power is transferred directly from the rectifier (in particular from the dc side thereof) to the energy storage. In this connection, "direct" means that no voltage transformation is carried out between the energy store and the rectifier. The rectifier may be an uncontrolled rectifier, but preferably may be a controlled rectifier, which preferably has the function of carrying out a power factor correction filter (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 here. The rectifier is supplied with power by an alternating current 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 can be provided that, in addition to the rectification, the rectifier can also carry out a (direct current) step-up conversion, in particular a step-up conversion beyond the voltage increase that is dependent on the PFC filtering. The rectifier can thus be provided to carry out a step-up conversion, which results in a voltage whose level is clearly above the peak-to-peak voltage of the (optionally interconnected) ac voltage at the ac charging connection. An increase of no more than about 5%, 7%, 10% or 15% is not considered a significant increase. The insignificant increase is due to PFC filtering and not to boost conversion (in ac direct charge mode).

As a step-up conversion, the increase in the rectified voltage relative to the peak-to-peak voltage of the (optionally interconnected) ac voltage at the ac charging connection is exceeded, in particular by more than the voltage increase associated with PFC filtering. In particular, in the case of no voltage transformation by a clear transformer (DC/DC converter) downstream of the rectifier circuit, the boost conversion is preferably carried out by a controller of the switches of the PFC-capable rectifier. The step-up conversion is carried out in particular in an alternating current direct charging mode and not in an alternating current adaptive charging mode (in which only the voltage increase associated with the PFC function is carried out). Therefore, the rectifier is equipped in particular with a boost function (corresponding to a boost conversion). This function may be implemented in an ac direct charging mode and not run in an ac adaption mode. In ac adaptation mode, the converter and the electric machine operate as a Buck converter (Abwaertswandler preset difference, Buck converter).

In the ac adaptive charging mode, power is transmitted from the rectifier through the inverter and through the electric machine to the energy storage. The converter, in particular its rectifying side, is connected to the rectifying side of the rectifier. The ac side of the converter is connected to the electric machine, in particular to the phase or winding connections of the electric machine. Power is thus transmitted from the inverter through the electric machine to the energy storage. In this case, 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 by the electric machine by feeding power to at least one phase connection of the electric machine and outputting it from a star point (opposite thereto). The phase connection is also referred to as an external phase connection. Power is transferred through the inductance of at least one winding (or winding segment) of the electric machine.

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

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

A switching device may be used to select one mode from at least two possible modes (ac direct charging mode or ac adapted charging mode). In the direct alternating current charging mode, the switching device connects the rectifier to 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 adaptive charging mode, the switching device connects the rectifier with the converter or establishes a power path which leads through the converter and the electric machine. For this purpose, a further switch of the switching device can be provided, which switches the power transmitted here. 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. The rectifier also implements a power factor correction filter function (PFC function, i.e., power factor correction function) particularly on the ac side of the rectifier. Where the power factor is increased, the harmonic components are reduced, or both. The rectifier can be designed as a Vienna rectifier. In order to implement the power factor correction filtering, the rectifier comprises (for each phase) at least one energy-storing structural element, for example a coil or a capacitor. The energy-storing structural element can be arranged, for example, in the form of a series inductance (for each phase) in series with the phase connection of the rectifier (on the ac side). Alternatively or additionally, the energy-storing structural elements may be connected in parallel with the different phase connections, for example in a delta configuration or a star configuration. The energy-storing components are designed in the form of parallel capacitors, by means of which the terminals are connected to one another. Therefore, the rectifier may be configured for power correction filtering, or may implement power factor correction filtering (PFC). The power correction filtering may be equivalent to the herein mentioned change in power factor or an increase in power factor and a decrease in harmonic components.

The converter may be a controlled full wave bridge, for example a multi-phase BnC bridge, in particular with a number of phases, where n corresponds to twice the number of phases. The inverter may be designed as a B6C bridge. Furthermore, the converters may be designed as one or more H-bridges.

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

In the ac adaptive charging mode, power can be transmitted from the electric machine to the energy store via a filter, in particular via a filter (as viewed from the inverter) downstream of the electric machine or between the electric machine and the energy store.

In the ac adaptive charging mode, the converter may be operated as a step-down converted dc voltage converter (referred to simply as a step-down converter). In the ac adaptive charging mode, the converter can be operated as a buck converter, in particular together with at least one winding of the electric machine. Furthermore, in the ac adaptive charging mode, the inverter may operate as a switch of a buck converter produced by combining the inverter and the electric machine (and corresponding controller). Only a part of all power switches of the converter is used in particular to realize 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 direct ac charging mode, all switches of the converter are in particular open. In the ac adaptive charging mode, the dc voltage formed by the rectification (and PFC filtering) is matched to the (lower) voltage level on the battery in order to avoid an excessively high current flow as a result of the strong voltage drop between the rectified ac voltage and the energy store voltage.

The voltage output by the inverter or the electric machine can be filtered by means of a filter. The filter is arranged downstream of the electric machine and is connected (without a switch) in particular to the star point or to an internal phase connection of the electric machine.

Furthermore, a dc voltage charging mode can be set. In this mode, power (which is present as direct current/direct current voltage) is transferred directly (i.e. without voltage conversion) from the direct current charging connection to the energy store. Alternatively and in combination therewith, a dc voltage adaptive charging mode can be provided, in which power is transmitted from the dc charging connection via the dc voltage converter to the energy store. The dc voltage converter may be a specific dc voltage converter for dc voltage charging or may be formed by an inverter and a switch of the electric machine. In the last-mentioned case, power is transmitted from the dc charging connection via the electric machine to the inverter and from the inverter 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 provided, in which the energy store is connected to the electric machine via an inverter. In this case, power is transmitted from the energy store via the inverter to the electric machine and is converted there by the electric machine into mechanical power (traction mode), or power is generated in the electric machine starting from the mechanical power and is transmitted via the inverter to the energy store. In the drive mode and in the recovery mode, the rectifier is deactivated and in particular has an open power switch.

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

The rectifier can be operated in a rectifier mode, in which the voltage present at the ac charging connection is only rectified 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 a boost conversion, but only a voltage boost associated with PFC filtering, if necessary, for example a boost of not more than 5%, 7%, 10% or 15%. In this mode, a rectified voltage is generated by an effective and optionally interconnected ac voltage at the ac charging connection and, if necessary, by an insignificant voltage increase associated with PFC filtering. The rectifier can be provided for operating also in a rectified voltage switching mode, in which the rectifier rectifies the voltage present at the ac voltage charging connection and, in addition, carries out a step-up switching that exceeds (does not significantly) the voltage increase caused by the PFC filtering. In order to be able to carry out (significant, i.e. above 5%, 7%, 10% or 15%) boost conversion, the rectifier has at least one energy-storing component, such as at least one capacitor or at least one inductor, as described above.

The rectifier has, in particular, a Power Factor Correction (PFC) function. The power factor correction function is implemented by means of at least one energy-storing component. The step-up conversion is thus realized with the components of the rectifier which are also used for 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 an ac direct charge mode, the rectifier performs boost conversion (as well as rectification and PFC filtering). The inverter is deactivated here, in particular because the power is conducted directly from the rectifier to the energy store. For example, the ac direct charging mode is set up when the peak-to-peak voltage (square root of two times the effective value of the voltage) at the ac charging connection does not exceed a predetermined difference (range) below the voltage of the energy store. This applies in particular to the single-phase occupation of an ac charging connection. Furthermore, the ac direct charging mode can be set when the peak-peak value of the voltage of the interconnection on the ac charging connection (corresponding to the square root of two times the voltage of the interconnection on the ac charging connection) does not exceed a predetermined difference below the voltage of the energy store.

Thus, for example, an ac direct charging mode can be set for a single-phase charging of the ac charging connection at voltages of the energy store of greater than 325V or 350V and at a network voltage of 230V available ac voltage. In this case, the rectifier also operates as a step-up chopper (step-up converter), i.e., performs a step-up operation, so that the voltage output by the rectifier is higher than would be produced in pure rectification and pure PFC filtering without (significant) step-up conversion.

When charging (corresponding to a three-phase occupation of the ac charging connection) with, for example, a three-phase current (star adaptation with an effective ac voltage of 230V or an interconnected effective ac voltage of approximately 400V), and the voltage of the energy storage exceeds 600V, 620V or 650V or 670V, an ac direct charging mode is likewise implemented in which the rectifier performs a step-up conversion function in addition to the functions of rectification and power factor correction, and outputs the power directly to the energy storage (without passing through an inverter/motor).

In addition, it can be provided that, in the ac adaptive charging mode, the rectifier does not perform a step-up conversion and only performs a rectification and performs a PFC function. The inverter is activated here and performs a step-down conversion together with at least one winding inductance of the electrical machine. Power is directed by the rectifier through the inverter and the electric machine (in this sequence) to the energy storage. The ac adaptive charging mode is set, for example, when the peak-to-peak voltage (square root of two times the effective value of the voltage) at the ac charging connection does not exceed a predetermined difference above the voltage of the energy store. This applies in particular to the single-phase occupation of an ac charging connection. Furthermore, the ac direct charging mode can be set when the peak-peak value of the voltage of the interconnection on the ac charging connection (corresponding to the square root of two times the voltage of the interconnection on the ac charging connection) does not exceed a preset difference above the voltage of the energy store. Thus, for example, an ac adaptive charging mode can be set for a single-phase occupancy of the ac charging connection in the available ac voltage of the energy store of not more than 325V or 350V and in the available network voltage of 230V ac voltage. Here, the rectifier operates only as a rectifier (and PFC filter) and not as a boost chopper (boost converter), i.e. no boost (which exceeds the voltage increase caused via PFC filtering) is carried out. The voltage output by the rectifier thus corresponds to the voltage generated in pure rectification without step-up conversion (including PFC filtering). When, for example, charging with a three-phase current (star adaptation with 230V or interconnected alternating currents of approximately 400V) (corresponding to a three-phase occupation of the alternating current charging connection) and the voltage of the energy store does not exceed 600V, 620V, 650V or also 670V, an alternating current adaptation charging mode is likewise implemented in which the rectifier only performs the functions of rectification and PFC filtering and not the function of step-up conversion. The rectifier outputs power to the energy store not directly but via an inverter/electric machine which reduces the voltage level. The converter and the electric machine are adapted to the rectified voltage regulation by step-down conversion.

Furthermore, an onboard power supply system with an ac charging connection and a rectifier is described. The onboard power supply system and its components correspond in particular to the onboard power supply system and the components with which the embodiments of the method and the method are described. The rectifier is optionally connected via a switching device either directly to the electrical energy store, this corresponding to an alternating current direct charging mode, or via an inverter and the electric machine to the electrical energy store, this corresponding to an alternating current adapted charging mode. The switching device is therefore provided for selecting two power paths (starting from the rectifier) which lead to the energy store. One power path is direct, while the other power path leads through the inverter and the electric machine connected thereto. The converter is connected with the electric energy accumulator through the motor. The converter is connected between the rectifier and the motor. Starting from the rectifier, the motor is arranged behind the current converter. And a motor is connected between the energy accumulator and the current converter. The internal phase connection (or at least one of the phase connections) of the electric machine is connected to an energy store. The external phase connection of the electric machine is connected to the energy store. The star point, the at least one internal phase connection or the star point-side end of at least one or all windings of the electric machine is connected to an energy store.

This enables a direct charging or a charging via an inverter and an electric machine downstream of the inverter, which together may represent a step-down dc voltage converter (step-down converter). In this case, at least one power switch of the inverter forms at least one switch of the buck converter, and at least one winding or a section thereof forms an inductance of the buck converter. The inverter or at least a subset of the power switches of the inverter is configured for operation also as switches of the buck converter.

The rectifier is arranged for rectifying 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 is increased and the harmonics are reduced. Furthermore, a rectifier is provided for adjustable step-up conversion of the voltage. The rectifier can be designed as a Vienna rectifier, as mentioned above. The rectifier is also designed in particular for implementing a power correction filter. For this purpose, the rectifier has at least one energy storage element, 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 also used to implement the boost conversion function of the rectifier. For this purpose, as already mentioned, the rectifier has in particular at least one energy-storing element, such as an inductance or a capacitor. As the at least one energy-storing element for forming the step-up conversion 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 adaptive charging mode and an ac direct charging mode. In particular, the control unit and the rectifier are together arranged for implementing an alternating current adapted charging mode and an alternating current direct charging mode. The control unit is arranged to adjust either the ac-adapted charging mode or the ac-direct charging mode (or other modes).

As mentioned, the rectifier can be provided for operating as a boost converter in at least one operating mode (in particular in an alternating current direct charging mode). Furthermore, it can be provided that the rectifier does not operate as a step-up converter in the ac adaptive charging mode (except for an insignificant voltage increase, for example, of not more than 5%, 7%, 10%, or 15%, which is caused by the PFC function). The rectifier can in particular have components which are designed to rectify a voltage which is at least 50%, 100%, 150% or 200% above the nominal peak-to-peak voltage across the ac electrical connection (if appropriate taking into account relevant interconnection factors).

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

The onboard power supply system can also have a dc charging connection. The dc charging connection is preferably connected to the energy store via at least one switch. The direct current charging connector is not connected with an energy storage device through a filter, and the energy storage device is connected to the motor (or arranged behind the motor) when necessary.

The onboard power supply system may also have a control device, which was also referred to as a control unit for short before. The control device is controllably connected with the switching device and the converter. The control device may be multi-piece and/or hierarchically divided or comprise parts controlling the switching devices, comprise further parts controlling the converter or its power switches, and may furthermore have a superior control unit. However, the hierarchy or division of the control devices may be varied and is not discussed in detail below. The control device is arranged for controlling the switching device in an alternating current direct charging mode, and the alternating current charging connector is directly connected with the energy storage device. The control device is also provided for controlling the switching device in an alternating current adapted charging mode, connecting the alternating current charging connection with the converter. In this mode, the control device is provided for controlling the inverter and, together with at least one winding of the electric machine, operates as a direct voltage converter. The switching device is provided in particular for switching the converter inactive in the direct ac charging mode, i.e. for setting all switches of the converter in the open state.

The control device can furthermore be designed to open both switches of the switching device in the dc charging state and to close the switch connecting the dc charging connection to the energy store.

The switching device may have a first switch connecting the rectifier and the energy storage. The switching device may have a second switch, which is arranged between the energy store and a connection connecting the rectifier and the inverter. The second switch is in particular arranged between the electric machine and the energy store or connects these two components. The second switch can be arranged in particular at the star point of the electric machine (or at an internal phase connection thereof) and can connect the star point or the internal phase connection 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 arrangement comprises only the first switch, while the second switch is realized by a switch of the converter. In this case, the power path leading through the converter or the electrical machine (and for transmission in the ac power adaptation charging mode) is opened or closed by the switch of the converter itself, while the path leading directly from the rectifier to the energy storage is opened or closed by the first switch. The control device is designed to alternately open or close 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 designed to control the first switch to close and the switch of the converter to open in the direct ac charging mode and to control the first switch to open and the switch of the converter to close in the adaptive ac charging mode. Instead of controlling all switches of the converter closed, it is also possible to control a subset of the full bridges closed or to control only one full bridge of the converter closed.

Drawings

The onboard power supply system described here is designed to carry out the method. The method uses the described components of the onboard power supply system. Fig. 1 shows an overview for elaborating an on-board electrical system or method.

Detailed Description

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

The motor M has a star point SP. The star point is positioned on the connection head inside the motor. The stars SP may be designed to be separable.

The second switch S1 is placed after the motor, seen from the inverter I. The second switch S1 connects the electric machine M (in particular its star point SP or at least one internal 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 between the electric machine M and the energy storage ES, in particular between the second switch S1 and the energy storage.

An ac charging connection ACLB (for example designed as a charging socket) is connected via a rectifier GR to the first switch B1 and to the inverter I. The first switch B1 and the inverter 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 network CAN, which is located outside the vehicle electrical system and CAN be provided in the charging station LS. The ac network ACN comprises an ac power supply. The rectifier GR has the function of a power factor correction filter (in addition to the rectifying function) so as to be able to regulate and in particular increase (relative to the use of a rectifier without PFC function) the power factor present at the ac charging connection ACLB.

If the first switch B1 is closed and the second switch S2 is open, the rectifier GR is directly connected to the energy storage ES. This corresponds to the alternating current direct charging mode. If the first switch B1 is open and the second switch S2 is closed, the rectifier GR is connected to the energy storage ES via the inverter I and the motor M (in this order). The inverter and the electric machine are operated together as the initially mentioned dc transformer (in particular step-down converted). The optional filter F makes it possible to suppress switching pulses in the on-board electrical system BN, which switching pulses are generated by a switching process in the converter I during operation as (a switching unit of) the dc transformer.

The grounding switch B2 switchably connects the energy store to the negative supply potential of the vehicle electrical system. The aforementioned switches B1 and S2 and switch B3 are provided in the positive supply potential rail. The battery disconnect switch B3 is provided between the filter and the energy storage ES. Switches B2 and B3 are set to closed in the alternating current charging mode and can be set to open in the event of a fault or in an inactive vehicle electrical system.

The optional direct-current voltage charging connector DCLB can enable the vehicle-mounted power grid BN to be connected to a direct-current network DCN, and the direct-current network is located outside the vehicle-mounted power grid BN. The dc power network DCN may be part of the charging station LS. The dc voltage charging connection DCLB is connected to the energy store via the dc voltage switch S2 (and via the switch B3). The connection between the switch S2 and the energy storage 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 dc voltage charging connection DCLB and energy storage ES is routed via switch C1. Switch C1 connects dc voltage charging connection DCLB and energy storage ES. If the switch is closed, power can be transferred directly from the dc voltage charging connection DCLB to the energy storage ES.

The control device CT, which is schematically illustrated, is connected to the switches B1 and S1 in a controlled manner. 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 (by alternate control) form a switching device. 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 charging of the alternating current, while the switches S1, B1 are open. The control device CT is also connected in a controlled manner to the switches S2 and B3 or C1 in order to control the switches to be closed in contrast to the switches B1 and S1 when the dc charging mode is present. The control device can furthermore be connected to the rectifier GR and the inverter I in a controlled manner. When the switch S1 is not provided, instead of this switch, the switch of the inverter I may be opened or closed by the control device, for example when switching between ac charging modes. The control device CT is provided via a controllable connection to the rectifier GR to regulate the power factor present at the ac charging connection ACLB by the rectifier, and to filter or attenuate harmonics. As mentioned, the control device CT can be designed in multiple parts or in stages. The control device CT may furthermore have an input for inputting a nominal operating mode. The control device can furthermore be designed to implement a traction mode or a recovery mode, as described at the outset.

Optional or alternative components or connections are shown in phantom, dotted or dashed lines.

Claims (12)

1. Method for transmitting electric power to an electric Energy Store (ES) of an on-board electrical system (BN), wherein in an alternating current direct charging mode power is transmitted directly to the Energy Store (ES) of the on-board electrical system (BN) by a rectifier (GR) of the on-board electrical system, which is supplied by an alternating current charging connection (ACLB), and in an alternating current adaptive charging mode power is transmitted from the rectifier (GR) through an inverter (I) and from the inverter (I) through an Electric Machine (EM) to the Energy Store (ES).

2. Method according to claim 1, wherein in the ac direct charging mode a switching device (B1, S1) connects the rectifier (GR) with the Energy Storage (ES) and in the ac adaptive charging mode the switching device (B1, S1) connects the rectifier (GR) with the converter (I).

3. Method according to claim 1 or 2, wherein the rectifier (GR) rectifies power and implements a power factor correction filtering function in at least one of the ac charging modes and/or implements a boost conversion in the ac direct charging mode.

4. Method according to any of the preceding claims, wherein in the alternating current adapted charging mode power is transferred from the Electric Machine (EM) to the Energy Storage (ES) through a filter (F).

5. A method according to any of the preceding claims, wherein in 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.

6. Method according to any of the preceding claims, wherein in the direct voltage charging mode power is transferred directly from the direct current charging connection (DCLB) to the Energy Storage (ES).

7. Vehicle electrical system having an alternating current charging connection (ACLB) and a rectifier (GR), wherein the Rectifier (RG) can be connected selectively via a switching device (B1, S1) either directly to the electrical Energy Store (ES) or via an inverter (I) and an Electric Machine (EM), wherein the inverter (I) is connected to the electrical Energy Store (ES) via the Electric Machine (EM).

8. The vehicle electrical system according to claim 7, wherein the rectifier (GR) is designed for rectifying the alternating current transmitted via the alternating current charging connection (ACLB) and for power factor correction filtering the power transmitted via the alternating current charging connection (ACLB).

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

10. The vehicle electrical system according to one of claims 7 to 9, further comprising a direct current charging connection (DCLB) which is connected to the Energy Store (ES) via a switch (S2; B3; C1).

11. The vehicle electrical system according to one of claims 7 to 10, further comprising a control device (CT) which is connected in a controlled manner to the switching devices (B1, S1) and to the inverter (I), wherein the control device (CT) is provided for controlling the switching devices (B1, S2) in an alternating current direct charging mode, the alternating current charging connection (ACLB) being connected directly 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, the alternating current charging connection (ACLB) being connected to the inverter (I), and for controlling the inverter (I), and at least one winding of the electric machine (M) operating together as a dc voltage converter, and in particular as a step-down converter.

12. The vehicle electrical system according to one of claims 7 to 11, wherein the rectifier (GR) is provided for operating as a boost converter in at least one operating mode.

Images