Charging device and method for operating same

Abstract

The invention relates to a charging device (102) for a vehicle (100) for charging an energy storage unit (101) of the vehicle (100) from a multiphase external AC voltage source (103), wherein the charging device (102) has: at least one first connection for connecting the charging device (102) to the multiphase external AC voltage source (103), at least one second connection for connecting the charging device (102) to the energy storage unit (101), a bidirectional DC-DC converter (205) which is electrically connected to the at least one second connection, a voltage source DC link (204) having at least one DC link capacitor, an AC-DC converter (203) which is electrically connected to the DC-DC converter (205) via the voltage source DC link (204), and a switching device (202), wherein the AC-DC converter (203) can be electrically connected to the at least one first connection via the switching device (202), and wherein the charging device (102) is designed to initially precharge the voltage source DC link (204) from the energy storage unit (101) via the DC-DC converter (205) and then to connect a first phase (201a) of the multiphase external AC voltage source (103) to the AC-DC converter (202) by means of the switching device (202), in order to further precharge the voltage source DC link (204).

Description

[0001] R.409842

[0002] - 1 -

[0003] Description

[0004] title

[0005] Charging device and method for operating such a

[0006] The present invention relates to a charging device for a vehicle for charging an energy storage unit from a multi-phase external AC voltage source, and a corresponding method.

[0007] Background of the invention

[0008] Electric vehicles are trending in the automotive industry because they consume cleaner energy and can achieve better performance compared to vehicles powered by fossil fuels. On-board charging devices can be used to charge energy storage systems in electric vehicles.

[0009] Disclosure of the invention

[0010] According to the invention, a charging device and a method for operating such a device, comprising the features of the independent claims, are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

[0011] The invention relates to a charging device for a vehicle for charging an energy storage unit from a multiphase external AC voltage source. The vehicle can, in particular, be an at least partially electrically powered vehicle that has a corresponding energy storage unit, for example, a vehicle battery. The energy storage unit is charged by means of an external AC voltage source, wherein this external AC voltage source is, for example, R.409842

[0012] - 2 -

[0013] Charging station for a vehicle that is at least partially electrically powered, or it can be designed as a conventional household power connection.

[0014] The charging device allows, in particular, the conversion of the alternating current supplied by the external AC power source into a direct current, as well as the adjustment of this direct current so that it can be used to charge the energy storage unit. The charging device can, in particular, be designed as an on-board charger.

[0015] Another function of the charging device is to limit the inrush current, which can occur due to a voltage difference between the external AC voltage source and the corresponding terminals of the charging device.

[0016] Increased inrush currents can be limited by pre-charge resistors, which are bypassed via relays during the charging process. Components whose resistance increases with temperature, such as PTC resistors, can be used as pre-charge resistors. High inrush currents cause the temperature-dependent component to heat up, increasing its resistance and thus resulting in a self-regulating limitation of the current flow.

[0017] The proposed charging device now has at least one primary connection for connecting the charging device to the multi-phase external AC power source. This primary connection can be, for example, an IEC Type 2 connector according to the international standard EN 62196, a GB / T connector according to Chinese standards, or a CCS (Combined Charging System) connector.

[0018] The charging device also has at least one second connection for connecting the charging device to the energy storage unit. This allows the alternating current (AC) supplied by the external AC power source, which is converted into DC by the charging device, to be used to charge the energy storage unit. R.409842

[0019] - 3 -

[0020] The charging device also includes a DC-DC converter electrically connected to at least one second terminal, a DC link, and an AC-DC converter electrically connected to the DC-DC converter via the DC link. Furthermore, the charging device has a switching device by which the AC-DC converter can be electrically connected to at least one first terminal.

[0021] The AC-DC converter, which is electrically connected to the DC-DC converter via the intermediate circuit, converts the alternating voltage supplied by the external AC power source into a direct voltage. This conversion to a direct voltage, as well as the subsequent transformation of this direct voltage by the DC-DC converter, is particularly necessary for charging the energy storage unit. The AC-DC converter can also incorporate a power factor control (PFC) stage.

[0022] The DC-DC converter serves to adapt the direct current (DC) voltage provided by the AC-DC converter. For example, the battery voltage of electric vehicles can range from 200V to over 800V, while the alternating current (AC) voltage provided by charging stations, depending on the number of phases, is typically in the range of 200V to 400V. Therefore, it is particularly necessary to adapt the DC voltage provided by the AC-DC converter to the DC voltage required for charging the energy storage unit using the DC-DC converter. The DC-DC converter is connected to the energy storage unit via at least one other terminal.

[0023] The DC-DC converter is also bidirectional, which allows the energy storage unit to be charged by the DC voltage provided by the AC-DC converter. Conversely, this bidirectional functionality makes it possible to use the voltage provided by the energy storage unit to charge the DC link. This application is explained in more detail below. R.409842

[0024] - 4 -

[0025] The intermediate circuit is electrically connected to the DC-DC converter and the AC-DC converter and includes at least one intermediate capacitor (or DC link capacitor). This intermediate circuit serves primarily to smooth the pulsating DC voltage signal provided by the AC-DC converter. The at least one intermediate capacitor is charged as the DC voltage increases. The DC voltage then decreases according to its pulsating waveform; however, this decrease is reduced by the voltage supplied by the capacitor. This results in a beneficial smoothing of the pulsating DC voltage signal, allowing the energy storage unit to be charged more evenly, which is particularly beneficial for the energy storage unit's lifespan.

[0026] Another component of the charging device is the switching device, whereby the AC-DC converter can be electrically connected to at least one first terminal via this switching device. The switching device allows the control of switching on the individual phases of the external AC voltage source.

[0027] The charging device is designed so that the DC link can be initially pre-charged from the energy storage unit via the bidirectional DC-DC converter. Further pre-charging of the DC link is possible by connecting the first phase of the multi-phase external AC voltage source to the AC-DC converter.

[0028] The DC link can only be pre-charged by the energy storage unit up to a certain voltage, which is limited by the voltage of the energy storage unit. Further pre-charging of the DC link may be necessary, in particular, to match its voltage to the voltage of the external AC voltage source or to the DC voltage provided by the AC-DC converter. For this purpose, the first phase of the external AC voltage source is connected to the AC-DC converter, resulting in a further pre-charging of the DC link. This allows the voltage of the DC link to be adjusted even closer to that of the external AC voltage source R.409842.

[0029] - 5 - equalize. If the DC link is pre-charged to a predetermined voltage value, for example, the other phases of the external AC voltage source can be switched on, thereby initiating the charging process of the energy storage unit.

[0030] Further pre-charging of the DC link via the AC-DC converter using the first phase of the external AC voltage source may be necessary if the voltage provided by the energy storage unit and transformed by the DC-DC converter is insufficient to achieve a sufficiently high pre-charging voltage of the DC link, for example a pre-charging voltage of 800V (DC).

[0031] The maximum pre-charge voltage achievable through initial charging is limited by the turns ratio of the DC-DC converter. For example, with an energy storage unit voltage of 195V (DC) and a DC-DC converter turns ratio of 2, a maximum pre-charge voltage of 390V (DC) can be achieved. Therefore, with an AC voltage of 272Vrms (AC), corresponding to an amplitude of approximately 385V (DC), the intermediate circuit must be pre-charged to at least 385V (DC) to avoid high inrush currents.

[0032] When adding, for example, two additional phases, the pre-charge voltage of the DC link must be increased further. The potential voltage applied to the DC link by the external AC power source is approximately 666 V (DC), which results from the compounding of the voltages of the three phases, specifically from the product of 385 V (DC) and the square root of 3. Therefore, the additional phases of the external AC power source are only connected once the DC link has been pre-charged to 800 V (DC).

[0033] By pre-charging the DC link, especially using the energy storage unit, it is possible to avoid high inrush currents by matching the DC link voltage to the voltage of the external voltage source, or to the voltage provided by the AC-DC converter.

[0034] - 6 -

[0035] DC voltage can be adjusted. This eliminates the need for pre-charge resistors to limit inrush currents, resulting in significant cost savings, particularly in the manufacturing of the charging device.

[0036] Reducing potential inrush currents is advantageous, for example, to ensure the protection of electronic components such as transistors, since high currents in particular can severely stress and / or destroy electronic components. Furthermore, limiting inrush currents may be necessary, especially according to relevant standards, such as IEC 61851-1 or ISO 17409.

[0037] In a further embodiment, during the initial pre-charging of the DC link, all phases of the external AC voltage source can be disconnected from the AC-DC converter. This ensures that the DC link is pre-charged exclusively by the voltage provided by the energy storage unit, which can be converted, in particular, by the bidirectional DC-DC converter. This reduces the voltage difference between the DC link and the first phase of the external AC voltage source, thus minimizing inrush currents when the external AC voltage source is connected, especially without the need for one or more pre-charging resistors.

[0038] In a further embodiment, at least one additional phase of the external AC voltage source can be connected to the AC-DC converter by means of the switching device after the first phase of the external AC voltage source has been connected to the AC-DC converter. Connecting the first phase of the external AC voltage source to the AC-DC converter further pre-charges the DC link, thus reducing inrush currents when the additional phases of the external AC voltage source are connected. Connecting the additional phases of the external AC voltage source to the AC-DC converter, in particular, initiates the charging process of the energy storage unit. R.409842

[0039] - 7 - In a further embodiment, the at least one further phase of the external AC voltage source is only connected to the AC-DC converter after the DC link has been charged to at least one predetermined voltage threshold. The at least one predetermined voltage threshold can, in particular, be selected such that the voltage difference between the pre-charged DC link and the DC voltage converted by the AC-DC converter is small enough that no, or only small, inrush currents occur.

[0040] In another embodiment, the charging device does not use a pre-charge resistor connected in parallel to a first switch of the switching device. The first switch serves to connect the first phase to the AC-DC converter. As explained above, the use of the pre-charge resistor could, in particular, limit inrush currents. The pre-charge resistor could, in particular, have a temperature-dependent characteristic curve, such that its resistance increases with rising temperature. High currents would lead to a temperature increase in the pre-charge resistor and thus to a higher resistance, which in turn would result in a self-regulating limitation of the current flow through the pre-charge resistor.

[0041] The proposed charging device eliminates the need for a pre-charge resistor, which is typically connected in parallel to the first switch, to limit inrush currents. This reduces the number of electronic components required for the charging device's circuitry, resulting in lower costs and a simpler, therefore less fault-prone, design.

[0042] In another embodiment, the switching device is designed such that the individual phases of the multi-phase external AC voltage source can be connected to the AC-DC converter separately. This allows, in particular, further pre-charging of the DC link by connecting the first phase of the external AC voltage source to the AC-DC converter. R.409842

[0043] - 8 - further phases of the external AC voltage source are not connected to the AC-DC converter and are only switched to the AC-DC converter when the voltage of the DC link has reached, for example, a predefined voltage threshold.

[0044] In a further embodiment, the at least one first connection has three terminals designed for connecting a three-phase AC voltage. The first phase serves in particular for further pre-charging the DC link, while the two further phases are only connected to the AC-DC converter when, for example, a certain pre-charging voltage is applied to the DC link.

[0045] Connections for three-phase AC voltage are particularly relevant for charging equipment for electric vehicles, as they enable, for example, higher charging power and thus a faster charging process for the energy storage unit, especially compared to single-phase connections. Furthermore, a charging device that provides connections for three-phase AC voltage is compatible with common charging standards such as IEC Type 2, GB / T, or CCS. Additionally, a three-phase charging device can also be operated in single-phase mode by connecting only one phase to the three-phase connection. This allows, for example, charging via a conventional household electrical connection, especially a 230V connection, in addition to multi-phase charging.

[0046] In a further embodiment, the at least one first terminal has a terminal for a neutral conductor. This neutral conductor serves as a reference potential and enables a directed current flow.

[0047] In a further embodiment, a method for charging an energy storage unit using a charging device is proposed. In a first step, a voltage intermediate circuit is initially pre-charged using the voltage provided by an energy storage unit via a bidirectional DC-DC converter. In a further step, a first phase R.409842

[0048] - 9 - a multi-phase external AC voltage source is connected to an AC-DC converter via a switching device. In a further step, the DC link is pre-charged via the AC-DC converter using the first phase of the multi-phase external AC voltage source.

[0049] By initially precharging the DC link using the voltage provided by the energy storage unit, and by further precharging it using the voltage provided by the first phase of the external AC power supply, the voltage difference between the DC link and the voltage of the external AC power supply can be reduced. This difference can lead to increased inrush currents, especially when the individual phases are switched on. Contrary to the prior art, no precharging resistor is required to limit the inrush currents.

[0050] For further embodiments of the method and their description, reference is made to the above statements on the charging device, which apply accordingly here.

[0051] In another embodiment, a charging device according to the preceding description is used for the method of charging an energy storage unit.

[0052] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawing.

[0053] The invention is schematically illustrated in the drawing using exemplary embodiments and is described below with reference to the drawing.

[0054] Brief description of the drawings

[0055] Figure 1 schematically shows a vehicle to illustrate the invention. R.409842

[0056] - 10 -

[0057] Figure 2 schematically shows a structure of a charging device in one embodiment.

[0058] Figure 3 shows a schematic switching arrangement of a charging device in one embodiment.

[0059] Figure 4 shows a flowchart of a charging process of an energy storage unit using a charging device in one embodiment.

[0060] embodiment(s) of the invention

[0061] Figure 1 schematically shows a vehicle 100 to illustrate the invention. The vehicle 100 includes, by way of example, an energy storage unit 101 and a charging device 102, which can be configured according to the invention. Also shown by way of example is a multi-phase external AC voltage source 103, to which the charging device 102 can be electrically connected, e.g., via a charging interface 104 on the vehicle 100. The charging interface 104 can, for example, be configured as an IEC Type 2 connector, a GB / T connector, or a CCS connector.

[0062] In the following, identical elements or components will be designated with the same reference symbols in order to simplify the description and to be able to build upon each other for different figures.

[0063] Figure 2 shows a schematic diagram 200 of a charging device 102 for charging the energy storage unit 101. The charging device 102 has, by way of example, three first terminals 206a, 206b, 206c, to which the three phases 201a, 201b, 201c of the external AC voltage source 103 are connected. The charging device 102 also has at least one second terminal 206d, to which, by way of example, the energy storage unit 101 is connected.

[0064] The charging device 102 includes a switching device 202, an AC-DC converter 203, a voltage intermediate circuit 204, and a bidirectionally designed R.409842

[0065] - 11 -

[0066] The DC-DC converter 205 is used. The switching device 202 allows the individual phases 201a, 201b, 201c of the external AC voltage source 103 to be connected to the AC-DC converter 203, whereby the phases 201a, 201b, 201c can be switched on separately, as indicated by the dashed lines in Figure 2. The AC-DC converter 203 serves to convert the AC voltage provided by the external AC voltage source 103 into a DC voltage required for charging the energy storage unit 101. The DC link 204 has, in particular, the function of smoothing the DC voltage signal generated by the AC-DC converter 203, which may have a pulsating characteristic. The DC-DC converter 205 adjusts this smoothed DC voltage signal so that the DC voltage applied to the second terminal 206d has an amplitude suitable for charging the energy storage unit 101.

[0067] It is also possible to precharge the DC link 204 via the DC-DC converter 205 using the voltage applied to the energy storage unit 101. The external AC voltage source 103 is disconnected from the AC-DC converter 203 by means of the switching device 202, so that the precharging of the DC link 204 is carried out exclusively by the energy storage unit 101. The DC link 204 can be precharged further by connecting the first phase 201a of the external AC voltage source 103 to the AC-DC converter 203 by means of the switching device 202. Once the DC link 204 is precharged, for example to a predetermined threshold voltage, the further phases 201b and 201c can be switched on and the charging of the energy storage unit 101 can begin.

[0068] Pre-charging the DC link 204 allows, in particular, the limitation of inrush currents that can occur due to voltage differences between the external AC voltage source 103 and the AC-side terminal of the AC-DC converter 203. Limiting these inrush currents can, for example, improve the protection of electronic components where a high current flow can lead to permanent impairment of functionality. Furthermore, as R.409842

[0069] - 12 - as described above, it may be necessary to limit inrush currents to appropriate limits in accordance with prescribed standards, for example IEC 61851-1 or ISO 17409.

[0070] Figure 3 shows a schematic switching arrangement 300 of a charging device 102 in a further embodiment. The charging device 102 can correspond to the charging device according to Figure 2.

[0071] The charging interface 104 is connected to an external AC voltage source 103, comprising three phases 201a, 201b, 201c. Additionally, the charging interface 104 is connected to a neutral conductor 301a and a protective conductor 301b (so-called PE connection), which, for example, in the event of a short circuit between a live conductor and a conductive part of the housing, dissipates the resulting fault current.

[0072] Furthermore, the phase-carrying connections between the external AC voltage source 103 and the charging interface 104 have fuses 302a, 302b, and 302c. The fuse 302a of the connection carrying the first phase 201a can, for example, be rated to activate at a current of 32A. In the connections carrying the other two phases 201b and 201c, the fuses 302b and 302c can, for example, be activated at a current of 16A each.

[0073] The charging interface 104 establishes an electrical connection between the external AC voltage source 103 and the neutral conductor 301a with the first terminals of the charging device 206a, 206b, 206c, 307a. This connects, in particular, the three phases 201a, 201b, 201c of the external AC voltage source 103, as well as the reference potential of the neutral conductor 301a, to the first terminals 206a, 206b, 206c, 307a of the charging device 102.

[0074] In the embodiment shown in Figure 3, the switching device 202 has switching elements S1 to S4, which can, for example, be designed as relays. Switching element S1 allows the first phase 201a to be connected to the AC-DC converter 203, while R.409842

[0075] - 13 - the switching elements S2 and S4 can be used to connect the second and third phases 201b, 201c of the external AC voltage source 103. Additionally, measuring points for potential voltage measurements are shown in Figure 3.

[0076] The AC-DC converter 203, which can be configured as a PFC stage, features half-bridges with the individual switching elements S11 to S16, as well as the inductors 304a, 304b, 304c. Furthermore, measuring points for potential current measurements are indicated in Figure 3.

[0077] The DC link 204 includes a switching element S5 and diodes 305a and 305b. Furthermore, the DC link 204 includes two capacitors 306a and 306b, which contribute in particular to smoothing the DC voltage provided by the AC-DC converter 203; these are the so-called intermediate capacitors. An unnamed ground potential can serve as a reference potential, especially for the AC component of the current flowing in the charging device. Figure 3 also shows measuring points for possible voltage measurement. The switching element S5 is open during a single-phase charging process and closed during a multi-phase charging process.

[0078] The bidirectional DC-DC converter 205 has four half-bridges with switching elements S21 to S24 and S41 to S44, unnamed capacitors and inductors, and a coil with a magnetic core. A first part of the bidirectional DC-DC converter 205 is connected to the voltage intermediate circuit 204, and a second part of the DC-DC converter 205 has two secondary terminals 206d and 307b, to which, in particular, the energy storage unit 101 is connected.

[0079] The topology shown here is only an example; other topologies are also possible. For example, relays or semiconductor switches can be used as switches or switching elements. Typically, MOSFETs, IGBTs, SiC FETs, or GaN FETs are used, and in some cases, diodes (Si, SiC, or GaN) are also employed. R.409842

[0080] - 14 -

[0081] Figure 4 shows an exemplary sequence of a charging process of an energy storage unit using a charging device, which can be designed in particular according to the invention.

[0082] In a first process step 401, the voltage intermediate circuit 204 is initially precharged via the DC-DC converter 205 using the energy storage unit 101.

[0083] After the DC link has been initially pre-charged, the first phase 201a of the external AC voltage source 103 can be connected to the AC-DC converter 203 in a further step 402. When the switching element S1 is closed, the first phase 201a is specifically connected to the AC-DC converter 203 by means of the switching elements S2 and S3.

[0084] In process step 403, the voltage intermediate circuit 204 is further precharged via the AC-DC converter 203 using the first phase 201a of the external AC voltage source 103.

[0085] In a next step 404, the additional phases 201b, 201c of the external AC voltage source 103 are connected to the AC-DC converter 203. The connection of the additional phases 201b, 201c can, for example, occur when the DC link 204 has reached a predetermined pre-charge voltage, thereby reducing inrush currents when the additional phases 201b, 201c are connected.

[0086] After the further phases 201 b, 201c have been switched on, the charging process begins, step 405, whereby the energy provided by the external AC voltage source 103 is converted into a DC voltage by means of the AC-DC converter 203, which is smoothed by means of the voltage intermediate circuit 204 and transformed by means of the DC-DC converter 205 to a voltage level intended for charging the energy storage unit 101.

Claims

R.409842 - 15 - Claims 1. Charging device (102) for a vehicle (100) for charging an energy storage unit (101) of the vehicle (100) from a multi-phase external AC voltage source (103), wherein the charging device (102) comprises: at least one first terminal (206a, 206b, 206c, 307a) for connecting the charging device (102) to the multi-phase external AC voltage source (103), at least one second terminal (206d, 307b) for connecting the charging device (102) to the energy storage unit (101), a bidirectional DC-DC converter (205) which is electrically connected to the at least one second terminal (206d, 307b), a DC link (204) with at least one DC link capacitor, an AC-DC converter (203) which is electrically connected to the DC-DC converter (205) via the DC link (204). is connected to a switching device (202), wherein the AC-DC converter (203) is electrically connected via the switching device (202) to the at least one first terminal (206a, 206b,206c, 307a), and wherein the charging device (102) is configured to initially precharge the DC link (204) via the DC-DC converter (205) from the energy storage unit (101) and then, by means of the switching device (202), to connect a first phase (201a) of the multi-phase external AC voltage source (103) to the AC-DC converter (202) in order to further precharge the DC link (204).

2. Charging device (102) according to claim 1, wherein during the initial pre-charging of the voltage intermediate circuit (204) all phases (201a, 201b, 201c) of the external AC voltage source (103) are disconnected from the AC-DC converter (203). R.409842 - 16 - are.

3. Charging device (102) according to claim 1 or 2, which is configured, after connecting the first phase (201a) of the multi-phase external AC voltage source (103) to the AC-DC converter (203), to connect at least one further phase of the multi-phase external AC voltage source (103) to the AC-DC converter (203) by means of the switching device (202).

4. Charging device (102) according to claim 3, which is configured to connect at least one further phase to the AC-DC converter (203) after the voltage intermediate circuit (204) has been charged to at least one predetermined voltage threshold.

5. Charging device (102) according to one of the preceding claims, which does not have a pre-charging resistor connected in parallel to a first switch (S1) of the switching device (202), which first switch (S1) is provided for connecting the first phase (201a) to the AC-DC converter (203).

6. Charging device (102) according to one of the preceding claims, wherein the switching device (203) is designed such that the individual phases (201a, 201b, 201c) of the multi-phase external AC voltage source (103) can be switched to the AC-DC converter (203) separately.

7. Charging device (102) according to one of the preceding claims, wherein the at least one first connection (206a, 206b, 206c, 307a) has three connections (206a, 206b, 206c) for a three-phase alternating voltage.

8. Charging device according to one of the preceding claims, wherein the at least one first connection (206a, 206b, 206c, 307a) has a connection (307a) for a neutral conductor (301a). R.409842 - 17 - 9. Method for charging an energy storage unit (101) using a charging device (102), comprising the following steps: Initial pre-charging (401) of a voltage intermediate circuit (204) of the charging device using a voltage provided by an energy storage unit (101) via a DC-DC converter (205), Connecting a first phase (402) of a multi-phase external AC voltage source (103) to an AC-DC converter (203) by means of a switching device (202), and Further pre-charging (403) of the voltage intermediate circuit (204) by means of a first phase (201a) of the multi-phase external AC voltage source (103) via the AC-DC converter (203).

10. The method of claim 9, further comprising: Switching on additional phases (404) of the multi-phase external AC voltage source (103) to the AC-DC converter (203), thereby starting the charging process (405) of the energy storage unit (101).

11. Method according to one of claims 9 to 10, wherein the switching on of further phases (404) takes place after the voltage intermediate circuit (204) has been charged to at least one predetermined voltage threshold.

12. Method according to one of claims 9 to 11, wherein during the initial pre-charging (401) of the voltage intermediate circuit (204) all phases of the external AC voltage source (103) are disconnected from the AC-DC converter (203).

13. Method according to any one of claims 9 to 12, wherein a charging device (102) according to claims 1 to 8 is used.

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