Method for operating a bidirectional charging device, bidirectional charging device and electric vehicle

Abstract

The invention relates to a bidirectional charging device, in particular a bidirectional charging device in an electric vehicle. During energy transmission for feeding electrical energy into an energy supply network, electrical parameters within the charging device can be monitored, and if the monitored parameters deviate from a predefined value range, the electrical connection within the charging device can be interrupted by means of switching elements present in the charging device. For this purpose, a hybrid interruption is provided, wherein interruption takes place by opening a semiconductor switching element and a mechanical switching element arranged in series with the semiconductor switching element.

Description

[0001] Description

[0002] title

[0003] Method for operating a bidirectional charger, bidirectional charger and electric vehicle

[0004] Technical area

[0005] The present invention relates to a method for operating a bidirectional charger, in particular a bidirectional charger for an electric vehicle. The present invention further relates to a bidirectional charger and an electric vehicle.

[0006] State of the art

[0007] Fully or at least partially electrically powered vehicles comprise an electric drive system that can be supplied with electrical energy from an electrical energy storage device, such as a traction battery. The electrical energy storage device of such a vehicle can be charged from an external energy source when the vehicle is stationary. Among other things, charging concepts exist for this purpose in which the electric vehicle can be connected to a single- or multi-phase electrical power supply network, and the alternating voltage provided by this power supply network can then be rectified by a charger integrated into the vehicle and adjusted to a voltage level suitable for charging the electrical energy storage device.

[0008] For example, the publication DE 10 2022 201 132 A1 describes a charger for an electrically powered vehicle and a method for operating a charger for an electrically powered vehicle. The charger described therein has an input-side AC voltage connection for connecting an AC voltage source and an output-side high-voltage DC voltage connection for connecting a battery to be charged.

[0009] Furthermore, initial concepts already exist for expanding a charger in an electric vehicle to enable reverse energy transfer from the electrical energy storage device to the charger's AC voltage connection. Such chargers are referred to below as bidirectional chargers. If such a bidirectional charger is to be connected to a power grid to feed electrical energy into the power grid, existing regulations and standards must be observed. In particular, it must be ensured that reliable galvanic isolation between the charger and the power grid is guaranteed in the event of a fault or error on the grid side.

[0010] Disclosure of the invention

[0011] The present invention provides a method for operating a bidirectional charger, a bidirectional charger, and an electric vehicle having the features of the independent patent claims. Further advantageous embodiments are the subject of the dependent patent claims.

[0012] Accordingly, it is provided:

[0013] A method for operating a bidirectional charger, in particular a bidirectional charger for an electric vehicle. The bidirectional charger is designed to transfer electrical energy from a DC voltage connection to an AC voltage connection in a first operating mode. The bidirectional charger is further designed to transfer electrical energy from the AC voltage connection to the DC voltage connection in a second operating mode. The method comprises a step of monitoring at least one electrical measured value during the transfer of electrical energy from the DC voltage connection to the AC voltage connection. Furthermore, the method comprises a step of interrupting an electrical connection between the AC voltage connection and the DC voltage connection if at least one monitored measured value lies outside a predetermined value range.Interrupting the electrical connection involves opening at least one electrical switching element and opening at least one mechanical switching element. Both the electrical switching element and the mechanical switching element are located within the charger.

[0014] Furthermore, it is planned:

[0015] A bidirectional charger with an AC voltage connection, a DC voltage connection, a voltage converter arrangement, a control device, and at least one mechanical switching element. The AC voltage connection is designed to be electrically coupled to a power supply network. The power supply network can be a single-phase or multi-phase electrical power supply network. The DC voltage connection is designed to be electrically coupled to an electrical energy storage device, in particular the traction battery of an electric vehicle. The voltage converter arrangement is designed to transfer electrical energy from the DC voltage connection to the AC voltage connection in a first operating mode. Furthermore, the voltage converter arrangement is designed to transfer electrical energy from the AC voltage connection to the DC voltage connection in a second operating mode.The at least one mechanical switching element is arranged between a connection point of the AC voltage connection and a corresponding connection point of the voltage converter arrangement. In particular, a mechanical switching element can be arranged between each connection point of the AC voltage connection and the corresponding connection point of the voltage converter arrangement. The mechanical switching element(s) can be, for example, relays or contactors. The control device is designed to monitor at least one electrical measured value during the transmission of electrical energy from the DC voltage connection to the AC voltage connection.Furthermore, the control device is designed to interrupt the electrical connection between the AC voltage connection and the DC voltage connection if at least one monitored measured value lies outside a specified value range. The interruption of the electrical connection.

[0016] Connection includes both an opening of at least one electrical switching element and an opening of at least one mechanical switching element.

[0017] Finally, it is planned:

[0018] An electric vehicle with a bidirectional charger according to the invention and an electrical energy storage device. The electrical energy storage device is electrically coupled to the DC voltage connection of the bidirectional charger.

[0019] Advantages of the invention

[0020] The present invention is based on the finding that bidirectional chargers can increasingly be provided in electric vehicles. These chargers can be used not only to transfer electrical energy from an AC voltage source to the electric vehicle's electrical energy storage device, but also to reverse the energy transfer from the electrical energy storage device to the AC voltage connection. If the AC connection is to be coupled to an electrical power supply network in order to feed electrical energy into this power supply network, the requirements of existing and, where applicable, future standards and regulations must be met. This includes, in particular, safely disconnecting the electrical connection between the charger and the power supply network, for example, in the event of a malfunction or error.

[0021] One idea of ​​the present invention is to meet the requirements for electrical isolation between the charger and the AC voltage connection, if possible, using components already present in the charger. Furthermore, one idea of ​​the present invention is to provide galvanic isolation using mechanical switching elements such as relays to separate the electrical connection between the charger and the AC voltage connection, and to also incorporate electronic switching elements already present in the charger, such as semiconductor switches, e-fuses, or the like, on the other. For this purpose, the invention provides for isolation between the charger and an external AC voltage network using a hybrid switching concept.Such a hybrid switching concept provides for the combination of a mechanical switching element, such as a relay, and at least one electrical switching element, in particular a semiconductor switching element. As will be explained in more detail below, the electrical switching elements can be, for example, semiconductor switching elements of the voltage converter arrangement in the charger. Furthermore, optional e-fuses can also be included, if available. Such a hybrid switching concept with at least two switching components arranged in series, in which at least one switching component is a mechanical switching element that enables galvanic isolation, can achieve particularly efficient, reliable isolation that can also comply with applicable standards and regulations.The inventive disconnection to the external power grid is implemented entirely with components within the charger in the electric vehicle. Therefore, no additional components or measures are required to feed electrical energy from the electric vehicle's electrical energy storage device into an external power grid.

[0022] The monitoring of relevant parameters such as voltage, frequency, current, etc. during the release of electrical energy from the electrical energy storage device can also be carried out entirely within the charger. Existing sensors, in particular voltage and current sensors within the charger, can be used for this purpose. Monitoring, evaluation, and any necessary interruption are thus carried out entirely within the charger. Optionally, an interruption within the charger can also be initiated based on an external signal. It is also possible, for example, to issue a signal when a fault or error is detected in order to initiate further measures outside the charger if necessary.

[0023] According to one embodiment, interrupting the electrical connection first involves opening at least one electrical switching element. Only after at least one electrical switching element has been opened does the mechanical switching element open. In this way, the mechanical switching element is generally opened in a de-energized state. This can reduce wear on the mechanical switching element and increase its service life.

[0024] According to one embodiment, the at least one electrical switching element comprises a semiconductor switching element. In particular, the electrical switching element can comprise a semiconductor switching element in a voltage converter arrangement of the bidirectional charger. The voltage converter arrangement of the bidirectional charger can, for example, comprise an AC / DC converter and a DC / DC converter. The DC / DC converter can adapt the electrical voltage level of the DC voltage. In the first operating mode, the AC / DC converter can convert the electrical DC voltage provided by the DC / DC converter into an AC voltage. For this purpose, a B2 bridge with two semiconductor switching elements can be provided for each electrical phase of the AC voltage. By appropriately opening semiconductor switching elements in the AC / DC converter orThe DC-DC converter can thus interrupt the flow of electrical current.

[0025] According to one embodiment, the bidirectional charger can comprise one or more so-called e-fuses. In particular, an e-fuse can be provided between each connection point of the AC voltage connection and a corresponding connection point of the voltage converter arrangement. Such an e-fuse can interrupt an electrical connection when a predetermined trigger condition is reached, for example, when a predetermined current value is exceeded. Such an e-fuse can be implemented, for example, from two opposing semiconductor switching elements. Thus, such an e-fuse can also be used as an electrical switching element that interrupts the electrical connection between the AC voltage connection and the voltage converter arrangement.

[0026] According to one embodiment, the e-fuses are opened first to open the at least one electrical switching element. Subsequently, additional semiconductor switching elements, for example in the voltage converter arrangement, can be opened if necessary. Preferably, the mechanical switching element(s) are then opened last. The above embodiments and refinements can be combined with one another as desired, where appropriate. Further embodiments, refinements, and implementations of the invention also include combinations of features of the invention not explicitly mentioned above or described below with respect to the exemplary embodiments. In particular, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the invention.

[0027] Short description of the drawings

[0028] Further features and advantages of the invention are explained below with reference to the figures. These show:

[0029] Fig. 1: a schematic representation of a principle diagram for an electric vehicle according to an embodiment, which is coupled to a power supply network;

[0030] Fig. 2: a schematic representation of a principle diagram of a bidirectional charger according to an embodiment;

[0031] Fig. 3: a schematic representation of a basic circuit diagram for an e-fuse as it can be implemented in an embodiment of the bidirectional charger;

[0032] Fig. 4: a schematic representation of a basic circuit diagram of an AC / DC converter as it can be implemented in an embodiment of the bidirectional charger; and

[0033] Fig. 5: a flowchart of how a method for operating a bidirectional charger according to an embodiment may be based.

[0034] Description of embodiments

[0035] Figure 1 shows a schematic representation of a principle diagram of an electric vehicle 3 with a bidirectional charger 1, which is electrically coupled to a power supply network 5 via a charging point 4. To charge an electrical energy storage device 2 in the electric vehicle 3, the power supply network 5 can, for example, provide electrical energy, which is thus made available at the charging point 4, for example a wall box or the like. This charging point 4 can also be referred to as Electrical Vehicle Supply Equipment (EVSE). The electric vehicle 3, in particular the charger 1, can be electrically connected to this charging point 4 by means of a suitable cable connection. Thus, a single- or multi-phase electrical alternating voltage from the power supply network 5 is applied to an alternating voltage connection of the charger 1.This alternating voltage can be converted into a direct voltage by means of the charger 1, which is suitable for charging the electrical energy storage device 3.

[0036] In a further operating mode, the charger 1 can convert electrical energy from the electrical energy storage device 2 into a single-phase or multi-phase alternating voltage and provide it at the connection to the charging point 4. This alternating voltage can thus be fed into the energy supply network 5 via the charging point 4.

[0037] Figure 2 shows a schematic representation of a principle diagram for a bidirectional charger 1, which can both charge an electrical energy storage device 2 using electrical energy from the energy supply network 5 and feed electrical energy from the electrical energy storage device 2 into the energy supply network 5. The charger 1 comprises an AC voltage connection 11. This AC voltage connection 11 can be electrically connected, for example, to a charging point 4 via a suitable cable connection. Furthermore, the charger 1 comprises a DC voltage connection 12, which can be electrically coupled to the electrical energy storage device 2 of the electric vehicle 3.

[0038] The charging device 1 further comprises a voltage converter arrangement 15, which can, on the one hand, convert the single-phase or multi-phase electrical alternating voltage provided at the AC voltage connection 11 into a direct voltage in order to charge an electrical energy storage device 2 connected to the direct voltage connection 12. Furthermore, the voltage converter arrangement 15 can convert the electrical direct voltage provided by the electrical energy storage device 2 into a single-phase or multi-phase alternating voltage and provide this at the AC voltage connection 11. For this purpose, the voltage converter arrangement 15 can, for example, comprise an AC / DC converter 15-1 and a DC / DC converter 15-2. As explained in more detail below, the AC / DC converter 15-1 can comprise a B2 bridge for each electrical phase of the alternating voltage.The AC / DC converter can thus rectify the AC voltage provided at the AC voltage terminal 11 and provide the rectified voltage to the DC-DC converter 15-2. Alternatively, the AC / DC converter 15-1 can convert a DC voltage provided by the DC-DC converter 15-2 into a single-phase or multi-phase AC voltage to output it at the AC voltage terminal 11. Furthermore, the AC / DC converter 15-1 can also adjust a power factor if necessary. Accordingly, the AC / DC converter 15-1 can also be referred to as a power factor corrector (PFC).

[0039] The charger 1 further comprises voltage sensors 16-i and current sensors 17-i. If necessary, further sensors can also be provided depending on the application or requirements. The measured values ​​recorded by the voltage and current sensors 16-i, 17-i are provided to a control device 18. The control device 18 can receive and evaluate the recorded measured values. In particular, the control device 18 can monitor the function of the charger 1 using the received measured values ​​and, if necessary, further parameters. Likewise, the electrical voltage of the power supply network can also be monitored by the voltage sensors 16-i. For example, when there is an energy flow from the DC voltage connection 12 to the AC voltage connection 11, the control device 18 can compare the recorded measured values ​​and / or parameters derived from the recorded measured values ​​with one or more target values. If the recorded or calculated values ​​orIf parameters of the charger are outside a predefined tolerance range, i.e. if at least one value exceeds or falls below a predefined limit, this can be detected, for example, as an error or fault. In particular, if at least one value or parameter deviates from the predefined tolerance range, an electrical connection within the charger 1 can be interrupted. In this way, the electrical connection between the voltage converter arrangement 15 and the AC voltage connection 11 and thus to the charging point 4 and the energy supply network 5 can be interrupted. The charger 1 comprises a mechanical switching element 14-i between each connection point of the AC voltage connection 11 and a corresponding connection point of the voltage converter arrangement 15. This mechanical switching element 14-i can be a relay, contactor, or the like, for example.While the current sensors 17-i can each be provided between the mechanical switching element 14-i and a connection point of the voltage converter arrangement 15, the current sensors 13-i are preferably provided between the connection points of the AC voltage connection 11 and the mechanical switching elements 14-i. In this way, an electrical voltage at the AC voltage connection 11 can also be detected when the mechanical switching elements 14-i are open.

[0040] Optionally, so-called e-fuses 13-i can be provided, preferably between the connection points of the AC voltage connection 11 and the mechanical switching elements 14-i. A possible embodiment of such e-fuses 13-i is described in more detail below.

[0041] For a previously mentioned interruption of an electrical connection to the charging point 4 or the energy supply network 5, a combination of the opening of at least two switching components arranged in series is provided. In particular, this involves a combined opening of mechanical switching components 14-i and at least one semiconductor switching component. Such a combination of a mechanical switching element and a semiconductor switching element is also referred to as a hybrid switching element. For example, the required interruption of the electrical connection within the charging device 1 can be achieved by opening semiconductor switching elements within the voltage converter arrangement 15. For this purpose, for example, the corresponding semiconductor switching elements in the B2-B bridges of the AC / DC converter 15-1 can be opened.Additionally or alternatively, suitable semiconductor switching elements of the DC-DC converter 15-2 can also be opened.

[0042] If e-fuses 13-i are also provided in the charger 1, these e-fuses 13-i can also be opened. Since such e-fuses 13-i are generally used for overcurrent protection, such components are also capable of safely and reliably isolating relatively high electrical currents. Therefore, these components are preferably opened first, before other components within the charger 1 are opened. Subsequently, semiconductor switching elements in the voltage converter arrangement 15 can be opened if necessary. If, however, no e-fuses 13-i are present, the semiconductor switching elements in the voltage converter arrangement 15 are preferably opened first.

[0043] Furthermore, the mechanical switching elements 14-i are opened, preferably last. By opening these mechanical switching elements 14-i, a galvanic isolation between the AC voltage connection 11 and the voltage converter arrangement 15 can be achieved. Thus, the power supply network 5 is also safely and reliably separated from the electrical energy source 2.

[0044] Figure 3 shows a schematic representation of a basic circuit diagram of an e-fuse 13 according to one embodiment. This can be, for example, an e-fuse 13-i, such as can optionally be used in the previously described charger 1. As can be seen from Figure 3, such an e-fuse can be implemented, for example, by a series connection of two complementary semiconductor switching elements 13a and 13b.

[0045] Figure 4 shows a schematic representation of a basic circuit diagram of an AC / DC converter 15-1 according to an embodiment, such as can be used, for example, for the previously described charger 1. As can be seen in Figure 4, the AC / DC converter comprises, for example, a B2 bridge with two semiconductor switching elements M1 to M6 for each electrical phase L1, L2, L3. An inductance I can be provided between the AC-side connection points and the nodes at which the two semiconductor switching elements M1 to M6 of a B2 bridge are connected to one another.Such a circuit arrangement can, on the one hand, carry out active rectification of an alternating voltage with any necessary power factor correction for charging the electrical energy storage device 2, and, on the other hand, carry out the necessary conversion into an at least approximately sinusoidal alternating voltage for converting the direct voltage provided by the electrical energy storage device 2 into an alternating voltage. For the previously described interruption, for example in the event of a fault or error, the semiconductor switching elements M1 to M6 in the AC / DC converter 15-1 can be opened, so that no further electrical energy can then flow from the electrical energy storage device 2 toward the alternating voltage connection 11 and thus into the power supply network 5.

[0046] Finally, Figure 5 shows a flowchart that may underlie a method for operating a bidirectional charger according to one embodiment. The bidirectional charger may, for example, be the bidirectional charger 1 previously described in connection with Figures 1 to 4. Accordingly, this bidirectional charger 1 can transmit electrical energy from the DC voltage connection 12 to the AC voltage connection 11 in a first operating mode and can transmit electrical energy from the AC voltage connection 11 to the DC voltage connection 12 in a second operating mode. The method comprises a step S1 for monitoring at least one electrical measured value during the transmission of electrical energy from the DC voltage connection 12 to the AC voltage connection 11.For example, monitoring the electrical measured values ​​may include recording current or voltage values ​​in the area of ​​the AC voltage connection 11. Furthermore, frequency, phase position, or other parameters may also be determined and monitored if necessary.

[0047] The method further comprises a step S2 for interrupting an electrical connection between the AC voltage connection 11 and the DC voltage connection 12. In particular, the electrical connection can be interrupted if at least one monitored measured value lies outside a predetermined value range or tolerance range. As already explained in detail above, interrupting the electrical connection comprises both opening at least one electrical switching element and opening at least one mechanical switching element within the charger 1. Preferably, at least one electrical switching element is opened first, and only then is the mechanical switching element opened.

[0048] In summary, the present invention relates to a bidirectional charger, in particular a bidirectional charger in an electric vehicle. During an energy transfer for feeding electrical energy into a power grid, electrical parameters within the charger can be monitored. If the monitored parameters deviate from a predetermined value range, the electrical connection within the charger can be interrupted by means of switching elements present in the charger. For this purpose, a hybrid interruption is provided, wherein the interruption occurs by opening a semiconductor switching element and a mechanical switching element arranged in series with the semiconductor switching element.

Claims

Claims 1. A method for operating a bidirectional charger (1) which is designed to transmit electrical energy from a DC voltage connection (12) to an AC voltage connection (11) in a first operating mode and to transmit electrical energy from the AC voltage connection (11) to the DC voltage connection (12) in a second operating mode, the method comprising: Monitoring (S1) at least one electrical measured value during the transmission of electrical energy from the DC voltage connection (12) to the AC voltage connection (11); Interrupting (S2) an electrical connection between the AC voltage connection (11) and the DC voltage connection (12) if at least one monitored measured value lies outside a predetermined value range, wherein the interrupting (S2) of the electrical connection comprises opening at least one electrical switching element (13-i, M1 -M6) and opening at least one mechanical switching element (14-i) within the bidirectional charger (1).

2. The method according to claim 1, wherein the interruption (S2) of the electrical connection first comprises opening the at least one electrical switching element (13-i, M1 -M6) and then opening the mechanical switching element (14-2).

3. The method according to claim 1 or 2, wherein the at least one electrical switching element comprises a semiconductor switching element (M1 -M6) in a voltage converter arrangement (15) of the bidirectional charger (1).

4. The method according to claim 1 to 3, wherein the at least one electrical switching element comprises an e-fuse (13-i) between the AC voltage terminal (11) and the voltage converter arrangement (15) of the bidirectional charger (1).

5. The method according to claim 3 and 4, wherein the opening of the at least one electrical switching element (13-i, M1 -M6) first comprises opening the e-fuse (13-i) and then opening a semiconductor switching element (M1 -M6) in the voltage converter arrangement (15).

6. A bidirectional charger (1), comprising: an AC voltage connection (11) designed to be electrically coupled to a power supply network (15); a DC voltage connection (12) designed to be electrically coupled to an electrical energy store (2); a voltage converter arrangement (15) designed to transfer electrical energy from the DC voltage connection (12) to the AC voltage connection (11) in a first operating mode and to transfer electrical energy from the AC voltage connection (11) to the DC voltage connection (12) in a second operating mode; at least one mechanical switching element (14-i) arranged between a connection point of the AC voltage connection (11) and a corresponding connection point of the voltage converter arrangement (15); a control device (18) designed to monitor at least one electrical measured value during a transfer of the electrical energy from the DC voltage connection (12) to the AC voltage connection (11) and to trigger an interruption of an electrical connection between the AC voltage connection (11) and the DC voltage connection (12) if at least one monitored measured value lies outside a predetermined value range, wherein the interruption of the electrical connection comprises opening at least one electrical switching element (13-i, M1-M6) and opening the at least one mechanical switching element (14-i).

7. Bidirectional charger (1) according to claim 6, wherein an e-fuse (13-i) is arranged between a connection point of the AC voltage connection (11) and a corresponding connection point of the voltage converter arrangement (15), and wherein the opening of the electrical switching element comprises an opening of the e-fuse (13-i).

8. Bidirectional charger (1) according to claim 6 or 7, wherein the voltage converter arrangement (15) comprises an AC / DC converter (15-1) and a DC-DC converter (15-2), and wherein the opening of the electrical switching element comprises opening a semiconductor switching element (M1 -M6) in the AC / DC converter and / or opening a semiconductor switching element in the DC-DC converter (15-2).

9. An electric vehicle (3) comprising a bidirectional charger (1) according to one of claims 6 to 8; and an electrical energy storage device (2) electrically coupled to the DC voltage terminal (12) of the bidirectional charger (1).

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