Method for operating an electric charger, charger, and motor vehicle

Abstract

The invention relates to a method for operating an electric charger (1), in particular for a motor vehicle, wherein: the charger has an input connection unit (2) for connecting to a supply grid connection unit (3) of a supply grid; the input connection unit (2) has at least a first, a second and a third input connection (L1, L2, L3); the charger has a voltage transformer stage (4) for providing a DC voltage; the voltage transformer stage (4) has at least a first, a second and a third half-bridge (5, 6, 7); each of the half-bridges (5, 6, 7) is connectable or connected to a different one of the input connections (L1, L2, L3); the voltage transformer stage (4) has a DC link (14) having at least one DC link capacitor (15, 16), in particular a series circuit consisting of a first and a second DC link capacitor (15, 16); and the charger (1) has a switching element (S2) that is designed to connect the third half bridge (7) to the first input connection (L1) in a first switching position and to the third input connection (L3) in a second switching position; the method comprising the following steps: switching the switching element (S2) into the first switching position; detecting a first electrical voltage at the first input connection (L1) and a second electrical voltage at the second input connection (L2); charging the at least one DC link capacitor (15, 16) to a bias voltage that is specified according to the first and the second electrical voltage; switching the switching element (S2) into the second switching position once the charging is complete; detecting at least a third electrical voltage at the third input connection (L3); and identifying a grid configuration or a fault in the supply grid on the basis of the determined electrical voltages.

Description

[0001] Description

[0002] title

[0003] The invention relates to a method for operating an electrical charger, in particular for a motor vehicle, wherein the charger has an input connection unit for connecting to a supply network connection unit of a supply network, wherein the input connection unit has at least a first, second and third input connection, wherein the charger has a voltage converter stage for providing a direct voltage, wherein the voltage converter stage has at least a first, second and third half-bridge, wherein each of the half-bridges is connectable or connected to a different one of the input connections, wherein the voltage converter stage has an intermediate circuit with at least one intermediate circuit capacitor, in particular a series circuit comprising a first and a second intermediate circuit capacitor, and wherein the charger has a switching element which is designed toThe third half-bridge is connected to the first input terminal in a first switching position and to the third input terminal in a second switching position. Furthermore, the invention relates to a charger and a motor vehicle with such a charger.

[0004] State of the art

[0005] Power grids vary worldwide, characterized by grid voltage, grid frequency, and the distribution system. Furthermore, a charger for charging an electric vehicle's high-voltage battery (on-board charger or OBC) can be connected to one or more phases when several electrical phases are available. Chargers of the type mentioned above are known for this purpose. The charger must be capable of operating with many grid configurations. For example, a charger in the German distribution system can be connected as a single-, two-, or three-phase device. In order for a control unit assigned to the charger to select the appropriate operating strategy, the current grid configuration is usually first detected. Detection of the current grid configuration occurs, for example, via grid-side voltage sensors.

[0006] Disclosure of the invention

[0007] The method according to the invention with the features of claim 1 is characterized by the following steps: switching the switching element into the first switching position, detecting a first electrical voltage at the first input terminal and a second electrical voltage at the second input terminal, charging the at least one intermediate circuit capacitor to a bias voltage predetermined as a function of the first and second electrical voltages, switching the switching element into the second switching position after charging is complete, detecting at least a third electrical voltage at the third input terminal, and detecting a grid configuration or a fault in the supply grid as a function of the determined electrical voltages. Therefore, according to the invention, before detecting the grid configuration, as described above, the intermediate circuit capacitor is precharged, which is discharged at the start of a charging process.The precharging according to the invention advantageously ensures that no unacceptably high inrush current flows when the switching element is switched to the second switching position and thus a current-carrying path is established between the third input terminal and the intermediate circuit. For example, electrical precharging resistors are assigned to at least the first and second input terminals in order to limit the respective inrush current. Due to the precharging in the first switching position of the switching element, there is no current-carrying connection between the third input terminal and the intermediate circuit capacitor at the start of the charging process, so that a precharging resistor is unnecessary here, thus advantageously saving components and costs. As long as the switching element is in the first switching position, no information about the mains voltage is available at the third input terminal.Therefore, according to the invention, after precharging, the switching element is switched to the second switching position in order to be able to measure voltages at all three input terminals and to complete the detection of the applied grid configuration. The half-bridges are preferably electrically connected in parallel to one another and / or to the intermediate circuit capacitor(s). The electrical voltages are applied by the supply grid. Charging of the intermediate circuit capacitor is completed when the predetermined bias voltage is reached. The switching element is particularly designed to distribute an electrical current between the first and third half-bridges in the first switching position with a single-phase grid connection, thereby advantageously increasing the total current consumption.

[0008] According to a preferred development of the invention, the predetermined bias voltage for charging the intermediate circuit capacitor is higher than the first and / or second voltage by a predetermined factor, in particular at least 10% or 15%. This advantageously ensures that voltage fluctuations in the supply network do not lead to impermissible inrush currents when the switching element is switched to the second switching position.

[0009] Particularly preferably, the predetermined bias voltage for charging the intermediate circuit capacitor is higher than the amplitude of a line-to-line voltage at the input terminals by a predetermined factor, in particular at least 10% or 15%. This advantageously ensures that even voltage fluctuations in the supply network do not lead to inadmissible inrush currents when the switching element is switched to the second switching position. The bias voltage is preferably calculated as the product of 1.15 x ^2 x ^3 xu, where 1.15 is the aforementioned increase in the bias voltage as the precharging factor, > / 3 is a line-to-line factor between the individual phase voltages and line-to-line voltages, U is a nominal voltage, and ^2 is a conversion factor from the effective value to the amplitude value of the nominal voltage at the corresponding input terminal. For a nominal voltage of 230 V, this results in a bias voltage of approximately 648 V.According to a preferred embodiment of the invention, a single-, two-, or three-phase alternating voltage is recognized as the network configuration. This ensures particularly advantageous and simple recognition of the network configuration from conventional network configurations.

[0010] Particularly preferably, it is provided that, in the first switching position of the switching element, a single- or two-phase alternating voltage is detected as a preliminary network configuration depending on the first and second electrical voltages. Detecting a preliminary network configuration provides a particularly advantageous option for facilitating fault detection.

[0011] According to a preferred development of the invention, the first and second electrical voltages are detected again in the second switching position of the switching element, and a network configuration or a fault is detected depending on the detected voltages. This re-detection provides a particularly simple way of detecting a network configuration or a fault. In particular, a fault is detected by comparing the first voltages determined in the first and second switching positions with each other and / or the second voltages determined in the first and second switching positions with each other.

[0012] Particularly preferably, a charging process is initiated depending on the detected grid configuration. This advantageously ensures that the charging process is coordinated with the grid configuration.

[0013] According to a preferred development of the invention, when an error is detected, a safety shutdown is carried out and / or an error message is output. The safety shutdown advantageously ensures that no dangerous situations arise. Outputting the error message advantageously ensures that a user is informed of the error and can take appropriate measures. It is particularly preferably provided that the charger has a voltage sensor assigned to each of the first, second and third half-bridges between the respective half-bridge and one of the input connections, and that the grid configuration is determined depending on sensor signals from the voltage sensors. Voltage sensors arranged in this way advantageously ensure that the voltages and thus the grid configuration can be determined particularly easily.

[0014] According to a preferred development of the invention, it is provided that the voltage sensor assigned to the third half-bridge is arranged between the switching element and the third half-bridge, that the first electrical voltage is determined in the first switching position of the switching element, and that the third electrical voltage is determined in the second switching position of the switching element. Such an arrangement of the voltage sensor results in the advantage that, compared to a voltage sensor arranged between the third input connection and the switching element, it detects an electrical voltage independently of the switching position of the switching element. Preferably, a voltage sensor is provided in front of and behind the switching element.

[0015] The charger with the features of claim 11 is characterized by a control device specifically designed to carry out the method according to the invention. This results in the aforementioned advantages.

[0016] The motor vehicle with the features of claim 12 is characterized by the charger according to the invention. This also results in the aforementioned advantages.

[0017] Further preferred features and combinations of features emerge from the above description and from the claims. The invention is explained in more detail below with reference to the drawings.

[0018] Figure 1 shows a circuit diagram of an advantageous charger, and

[0019] Figure 2 shows a method for operating the charger. Figure 1 shows an electrical circuit diagram of an advantageous charger 1. The charger 1 has an input connection unit 2 on the input side for connection to a supply network connection unit 3 of a supply network with a single-, two-, or three-phase alternating voltage. The input connection unit 2 has a first input connection L1, a second input connection L2, a third input connection L3, a neutral conductor connection N, and a protective conductor connection PE.

[0020] The charger 1 further comprises a voltage converter stage 4 for providing a DC voltage. The voltage converter stage 4 comprises a first half-bridge 5 consisting of the semiconductor switches S11 and S12, a second half-bridge 6 consisting of the semiconductor switches S13 and S14, and a third half-bridge 7 consisting of the semiconductor switches S15 and S16.

[0021] The half-bridges 5, 6, and 7 are electrically connected in parallel. The semiconductor switches of the respective half-bridges 5, 6, and 7 are each electrically connected in series. The semiconductor switches S11, S13, and S15 are low-side switches, and the semiconductor switches S12, S14, and S16 are high-side switches.

[0022] In each case, a center tap between the semiconductor switches S11 to S16 of a half-bridge 5, 6, 7 is connectable or connected, preferably via a respective first, second and third choke 8, 9, 10, to a respective other of the input terminals L1, L2, L3 via a respective first, second and third connecting line 11, 12, 13.

[0023] The center tap of the first half-bridge 5 is connected to the first input terminal L1 via the first choke 8 and the first connecting line 11. The center tap of the second half-bridge 6 is connected to the second input terminal L2 via the second choke 9 and the second connecting line 12. The center tap of the third half-bridge 7 is connected to the third input terminal L3 via the third choke 10 and the third connecting line 13.

[0024] The voltage converter stage 4 further comprises an intermediate circuit 14 with a

[0025] A series circuit consisting of a first intermediate circuit capacitor 15 and a second intermediate circuit capacitor 16. The intermediate circuit capacitors 15, 16 are connected in parallel to the half-bridges 5, 6, 7. The ends of the half-bridges 5, 6, 7 are connected to a two-pole intermediate terminal 17. The high-side switches are connected to a positive intermediate terminal 18, and the low-side switches are connected to a negative intermediate terminal 19.

[0026] A DC-DC converter 20 is connected to the intermediate terminal 17. The DC voltage at the intermediate terminal 17, which is present on the input side of the DC-DC converter 20, is converted into a charging voltage for charging a battery 21, preferably a traction battery or high-voltage battery, connected to the output side of the DC-DC converter 20.

[0027] A series circuit of a first diode 22 and a second diode 23 is connected in parallel to the half-bridges 5, 6, 7. The first and second diodes 22, 23 are reverse-biased and prevent current flow from the positive intermediate terminal 18 to the negative intermediate terminal 19 and allow current flow from the negative intermediate terminal 19 to the positive intermediate terminal 18. A center tap between the first and second diodes 22, 23 is connected to the neutral conductor terminal N via a neutral conductor 24.

[0028] The charger 1 has a first switching element S1, which is designed to selectively connect or disconnect the first input terminal L1 from the first half-bridge 5. The charger 1 further has a second switching element S2, which is designed to connect the third half-bridge 7, in a first switching position, to the first input terminal L1 via the connecting line 11 and, in a second switching position, to the third input terminal L3 via the connecting line 13. In other words, the second switching element S2 is designed to conduct a charging current from the first input terminal L1 or from the third input terminal L3 to the third choke 10.

[0029] The charger 1 also has a third switching element S3, which is designed to selectively connect or disconnect the second input terminal L2 from the second half-bridge 6. Finally, the charger 1 also has a fourth switching element S4, which is arranged between a center tap between the two diodes 22, 23 and a center tap between the two intermediate circuit capacitors 15, 16.

[0030] In this case, precharging resistors, preferably switchable resistors, thermistors, or NTC resistors, are connected in parallel with the first switching element S1 and the third switching element S3 so that a starting current decays and is limited when an alternating voltage is connected to the input connection unit 2 before the first and third switching elements S1, S3 are closed. The switching elements are preferably designed as semiconductor switching components (IGBT or MOSFET, based on Si, SiC, or GaN), as contactors, or as relays.

[0031] Furthermore, the charger has a voltage sensor V assigned to each of the first, second and third half-bridges 5, 6, 7 between the respective half-bridge 5, 6, 7 and one of the input terminals L1, L2, L3, which measures the voltage of the respective input terminal L1, L2, L3 relative to the neutral conductor terminal N.

[0032] The voltage sensor V assigned to the third half-bridge 7 is arranged here between the switching element S2 and the third half-bridge 7. Alternatively or additionally, the voltage sensor V is arranged between the third input terminal L3 and the switching element S2, as indicated by the dashed line.

[0033] Additional voltage sensors V are provided between the two intermediate terminals 18, 19 and between the center tap between the two intermediate circuit capacitors 15, 16 and the negative intermediate terminal 19, i.e., parallel to the intermediate circuit capacitor 16. Each of the chokes 8, 9, 10 is assigned a current sensor A.

[0034] The charger 1 is also assigned a control device 25, which is designed in particular to detect and evaluate sensor signals from sensors A, V, to control the switching elements S1 to S4, and / or to control the half-bridges S11 to S16. An advantageous method for operating the charger 1 is described below with reference to Figure 2. Figure 2 shows the method using a flowchart. In particular, the method ensures that an impermissibly high inrush current is reliably avoided. The method is preferably carried out by a control device assigned to the control unit 1, for example, the control device 25.

[0035] In step 100, the method begins by switching the second switching element S2 to the first switching position. A first electrical voltage at the first input terminal L1 and a second electrical voltage at the second input terminal L2 are then detected using the voltage sensors V.

[0036] If, in a decision step 200, the voltage sensors V detect that a voltage is present at both the first input terminal L1 and the second input terminal L2, the method continues with step 301. A two-phase alternating voltage is thus detected as the provisional grid configuration. If, however, it is detected that a voltage is present only at the first input terminal L1, the method continues with step 302. A single-phase alternating voltage is detected as the provisional grid configuration.

[0037] In steps 301 and 302, a predetermined bias voltage is determined depending on the first or the first and second voltages, respectively. Preferably, the predetermined bias voltage is higher than the first and / or second voltage or an amplitude of a phase-to-phase voltage at the input terminals by a predetermined factor, for example, 15%. The intermediate circuit capacitors 15, 16 are then precharged to this bias voltage.

[0038] In the following steps 401 and 402, it is detected that the bias voltage has been reached and thus charging is complete. The second switching element S2 is then switched to the second switching position. In the subsequent steps 501 and 502, at least a third electrical voltage is detected at the third input terminal L3. Depending on the determined electrical voltages, either a permissible grid configuration or a fault in the supply grid is detected in decision steps 601 and 602.

[0039] Preferably, the first and second electrical voltages are also measured again. For example, an error is detected if the newly measured voltages show inadmissible values, for example, if the first electrical voltage is zero.

[0040] If an error is detected, the method ends with step 700. In step 700, in particular, a safety shutdown is carried out and / or an error message is output.

[0041] If, however, a permissible grid configuration is detected, a charging process is initiated depending on the detected grid configuration. For example, starting from step 601, three-phase charging occurs in step 701 if a third electrical voltage greater than zero was detected, two-phase charging occurs in step 702 if no third electrical voltage greater than zero was detected, and single-phase charging occurs in step 703 starting from step 602.

[0042] In step 701, a three-phase alternating voltage is identified as the final grid configuration, in step 702, a two-phase alternating voltage is identified as the final grid configuration, and in step 703, a single-phase alternating voltage is identified as the final grid configuration. The method ends after the charging process is completed.

Claims

Claims 1. A method for operating an electric charger (1), in particular for a motor vehicle, wherein the charger has an input connection unit (2) for connection to a supply network connection unit (3) of a supply network, wherein the input connection unit (2) has at least a first, second and third input connection (L1, L2, L3), wherein the charger has a voltage converter stage (4) for providing a DC voltage, wherein the voltage converter stage has at least (4) a first, second and third half-bridge (5, 6, 7), wherein each of the half-bridges (5, 6, 7) is connectable or connected to a different one of the input connections (L1, L2, L3), wherein the voltage converter stage (4) has an intermediate circuit (14) with at least one intermediate circuit capacitor (15, 16), in particular a series circuit comprising a first and a second intermediate circuit capacitor (15, 16), and wherein the charger (1) has a switching element (S2),which is designed to connect the third half-bridge (7) in a first switching position to the first input terminal (L1), and in a second switching position to the third input terminal (L3), with the following steps:, Switching the switching element (S2) into the first switching position, detecting a first electrical voltage at the first input terminal (L1) and a second electrical voltage at the second input terminal (L2), Charging the at least one intermediate circuit capacitor (15, 16) to a predetermined bias voltage dependent on the first and second electrical voltages, Switching the switching element (S2) to the second switching position after charging is complete, Detecting at least a third electrical voltage at the third input terminal (L3), and Detection of a network configuration or a fault in the supply network depending on the detected electrical voltages.

2. Method according to claim 1, characterized in that the predetermined bias voltage for charging the intermediate circuit capacitor (15, 16) is higher than the first and / or second voltage by a predetermined factor, in particular at least 10% or 15%.

3. Method according to one of the preceding claims, characterized in that the predetermined bias voltage for charging the intermediate circuit capacitor (15, 16) is higher by a predetermined factor, in particular at least 10% or 15%, than an amplitude of a chain voltage at the input terminals (L1, L2).

4. Method according to one of the preceding claims, characterized in that a single-, two- or three-phase alternating voltage is recognized as the network configuration.

5. Method according to one of the preceding claims, characterized in that in the first switching position of the switching element (S2) a single-phase or two-phase alternating voltage is recognized as a provisional network configuration depending on the first and second electrical voltage.

6. Method according to one of the preceding claims, characterized in that in the second switching position of the switching element (S2) the first and the second electrical voltage are detected again, and that a network configuration or a fault is detected as a function of the detected voltages.

7. Method according to one of the preceding claims, characterized in that a charging process is started depending on the recognized network configuration.

8. Method according to one of the preceding claims, characterized in that when an error is detected, a safety shutdown is carried out and / or an error message is output.

9. Method according to one of the preceding claims, characterized in that the charger (1) has a voltage sensor (V) assigned to each of the first, second and third half-bridges (5, 6, 7) between the respective half-bridge (5, 6, 7) and one of the input terminals (L1, L2, L3), and in that the network configuration is determined as a function of sensor signals from the voltage sensors (V).

10. Method according to one of the preceding claims, characterized in that the voltage sensor (V) assigned to the third half-bridge (7) is arranged between the switching element (S2) and the third half-bridge (7), that in the first switching position of the switching element (S2) the first electrical voltage is determined, and that in the second switching position of the switching element (S2) the third electrical voltage is determined.

11. Charging device (1), characterized by a control device (25) which is specially designed to carry out the method according to one of the preceding claims.

12. Motor vehicle, characterized by a charger (1) according to claim 11.

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