Charger and method for operating a charger

Abstract

Charger (1), in particular for an electric or plug-in hybrid vehicle, comprising at least two power stages (10, 20, 30), by means of which an alternating voltage is converted into a direct voltage, and at least one control device (2) for controlling the power stages (10, 20, 30), wherein the control device (2) is designed such that it detects the number of connected phases of an alternating voltage and, depending on the number of detected phases, controls a corresponding number of power stages (10, 20, 30), wherein the control device (2) is designed such that it determines a control history of the individual power stages (10, 20, 30) and takes this into account when selecting the power stages (10, 20, 30) to be controlled in such a way that the power stages (10, 20, 30) are evenly loaded, wherein the control device (2) assigns at least one connection (L1, L2, L3) for a phase to optionally different power stages (10, 20,30), characterized in that each charging stage (10, 20, 30) has a first half-bridge (11, 21, 31) with power semiconductor switches, which is connected to a terminal (L1, L2, L3) for one phase, wherein the first half-bridges (11, 21, 31) of the charging stages (10, 20, 30) are each connected to terminals (L1, L2, L3) of different phases, wherein all power stages (20, 30) except for one power stage (10) have at least one further half-bridge (22, 33), wherein the at least one further half-bridge (22, 33) is connected to a terminal (L1) of a different phase than the first half-bridge (21, 31).

Description

The invention relates to a charging device and a method for operating a charging device.A charging device is known from DE 10 2009 000 096 A1, in particular for an electric or plug-in hybrid vehicle, comprising at least two power stages, by means of which an AC voltage is converted into a DC voltage, and at least one control device for controlling the power stages, wherein the control device is designed such that it detects the number of connected phases of an AC voltage and controls a corresponding number of power stages as a function of the number of detected phases. Specifically, it is disclosed that charging is carried out with a single-phase alternating voltage or with a three-phase three-phase power supply system. Accordingly, the charging device comprises three power stages each having a half bridge with two power semiconductor switches and free-wheeling diodes arranged in parallel with the power semiconductor switches.U.S. Pat. No. 4,451,773 A discloses a charging device for a battery, by means of which the battery can be charged both from a single-phase and from a three-phase alternating voltage network.DE 10 2011 108 495 A1 discloses an inverter for use in a motor vehicle, by means of which an DC voltage can be converted into an AC voltage for electric machines.U.S. Pat. No. 2,333,617 A discloses a charging device for a battery from a three-phase alternating voltage network.EP 2 362 522 A2 discloses a circuit for connecting a power unit or charging unit for an accumulator or a battery to a supply network, wherein the supply network has at least two connections. The power unit or charging unit has at least two connection units or stages, wherein each connection unit or stage can be connected to all connections of the supply network.From post-published DE 10 2013 007 971 A1, a charging device of the generic type is known.The invention is based on the technical problem of providing a charging device which has a longer service life and of providing a method for operating such a charging device.The solution of the technical problem results from a charger having the features of claim 1 and a method for operating a charger having the features of claim 6.The charger comprises at least two power stages, by means of which an alternating voltage is converted into a direct voltage. Furthermore, the charger comprises at least one control device for controlling the power stages, wherein the control device is designed such that it detects the number of connected phases of an AC voltage and controls a corresponding number of power stages as a function of the number of detected phases. The control device is further designed in such a way that it determines a control history of the individual power stages and takes it into account when selecting the power stages to be controlled in such a way that the power stages are loaded uniformly, wherein the control device can assign at least one connection for one phase to different power stages as desired. The basic idea here is that, in the case of a fixed assignment, one power stage is loaded more heavily than the others. If the charging device is designed, for example, to be charged to both single- and three-phase networks, the power stage assigned to the single-phase network connection is loaded more heavily than the other two. The greater load leads to an increased risk of failure. According to the invention, the control history of the power stages is now taken into account, wherein the control strategy of the control device attempts to adapt the control history of the power stages and thus of the loads. This reduces the risk of the charger failing. It should be noted here that the charger can also be designed in such a way that a DC voltage is converted into an AC voltage and fed back into the grid. These unloading processes are then preferably also taken into account in the control history. Charging or charging processes will always be referred to below, but these may also include the aforementioned discharging processes.Each charging stage has a first half bridge with two power semiconductor switches which is connected to a terminal for one phase, the first half bridges of the charging stages being connected in each case to terminals of different phases, all the power stages having at least one further half bridge except for one power stage, the at least one further half bridge being connected to a terminal of a different phase than the first half bridge. Thus, a different phase can be very easily assigned to a power stage, wherein the control device then controls the corresponding half bridge.The control history can take account of the load on the power stages qualitatively or quantitatively.In one embodiment, the control history includes the number of chargings at the respective power level. This represents a qualitative description of the load, which does not necessarily have to correspond to the real load, for example because the charging times in the individual charging processes can be very different. However, the acquisition and storage of the control history is very easy. Alternatively, the charging time can be summed up.In another alternative embodiment, the control history includes the energy provided by the respective power level via the charging operations or the provided energy difference compared to at least one other power level. In the first case, the respective energy quantities are summed and compared. In the second case, preferably one power stage is the reference, the control history of the other power stages expressing how much more or less the power stages have provided energy compared to the reference power stage. The energy or energy difference provided represents a quantitative value for the loading of the power stages. In this case, it can additionally be provided that the charging times are also weighted as a function of the charging voltages. The energy or energy difference can also be expressed here by an equivalent such as, for example, current x time (with assumed constant voltage).In a further embodiment, a first power stage does not have a further half bridge and the further power stages have exactly one further half bridge, wherein the further half bridges are connected to the connection of the phase of the first power stage. This reduces the additional circuit complexity (for example to two further half bridges in the case of three power stages), wherein use is made here of the fact that usually only the alternative is in any case to charge in one or three phases.With regard to the method for operating the charging device, reference can be made in full to the preceding explanations relating to the charging device.The invention is explained in more detail below with reference to preferred exemplary embodiments. The figures show: FIG. 1 shows a schematic block diagram of a charging device in a first embodiment, FIG. 2 shows a schematic block diagram of a charging device in a second non-claimed embodiment, and FIGS. 3 a- 3 e show an exemplary course for the method.FIG. 1 shows a schematic block diagram of a charging device 1. The charging device 1 comprises a first line stage 10, a second power stage 20 and a third power stage 30. the first power stage 10 comprises a first half bridge 11 with two power semiconductor switches, not shown, which are designed, for example, as transistors or thyristors. Furthermore, the first power stage 10 comprises non-illustrated free-wheeling diodes for the power semiconductor switches and further elements in order to provide a smoothed DC voltage at the output. The second power stage 20 comprises a first half bridge 21 and a further, second half bridge 22, likewise the third power stage 30 comprises a first half bridge 31 and a further, second half bridge 32. furthermore the charger 1 comprises a terminal L 1 for a first phase of an alternating voltage, a terminal L 2 for a second phase of an alternating voltage, a terminal L 3 for a third phase of an alternating voltage and a terminal N for a neutral conductor. The terminal L 1 is connected to the first half bridge 11 of the first power stage 10 (more precisely to a center tap, not shown, of the half bridge 11). The terminal L 2 is connected to the first half bridge 21 of the second power stage 20 and the terminal L 3 is connected to the first half bridge 31 of the third power stage 30. In addition, the terminal L 1 is connected to the further half bridge 22 of the second power stage 20 and to the further half bridge 32 of the third power stage 30. The terminal N is connected to all three power stages 10, 20, 30. Furthermore, the output lines for "+" and "-" of the three power stages 10, 20, 30 are connected to one another. These combined positive and negative lines are connected, for example, to a high-voltage battery of an electric or plug-in hybrid vehicle.Furthermore, the charger 1 comprises a control device 2 which is responsible, inter alia, for the actuation of all half bridges 11, 21, 22, 31, 32. This is schematically indicated by the control signals S 1-S 3 for the three power stages 10, 20, 30. A further task of the control device 2 is to detect how many phases are at the terminals L 1-L 3 and to determine a control history for the power stages 10, 20, 30.If the control device 2 detects that a phase of an alternating voltage is present at each of the three terminals L 1-L 3, the control device 2 controls the first half bridges 11, 21, 31 of the three power stages 10, 20, 30, which then operate together as a three-phase rectifier. The second half bridges 22, 32, on the other hand, are blocked. In this case, all three power stages 10, 20, 30 are loaded uniformly.If, on the other hand, only one phase is connected (typically to L1), then only one power stage 10 is required. Theoretically, it would also be conceivable to operate all three power stages 10, 20, 30 in parallel with the charging device 1 according to the invention, but this results in the disadvantage of greater losses. In the parallel operation of the three power stages 10, 20, 30, the half bridges 11, 22, 32 would be driven in the same way by the control device 2, wherein the half bridges 21, 31 would be blocked. However, it is to be assumed below that only one power stage 10, 20 or 30 is active in only one phase present.In this case, the control device 2 acquires the control history of the individual power stages 10, 20, 30 during single-phase operation. The control history can be the number of charging cycles, the charging time, the energy passed through over the charging cycles, or a related variable such as current x time (e.g. in Ah) over the charging cycles, which is proportional to the energy when a constant voltage is assumed.The control device 2 now compares the control history of the three power stages 10, 20, 30 and selects the power stage with the historically lowest load. If this evaluation reveals, for example, that the second power stage 20 is historically the least loaded, the second half bridge 22 is actuated by the control device 2 and all other half bridges 11, 21, 31, 32 are blocked. The control device 2 thus distributes the single-phase charging cycles as uniformly as possible to the three power stages 10, 20, 30, in order to thus extend the service life of the charger 1.The additional outlay compared to a conventional charger is in this case the two half bridges 22, 32 and the modified control of the control device 2 (including the detection and storage of the control history for the power stages).FIG. 2 shows an alternative embodiment of the charging device 1, wherein identical elements have identical reference numerals. In contrast to the embodiment according to FIG. 1, all three power stages 10, 20, 30 have only one first half bridge 11, 21, 31 each. The switching of the terminal L1 takes place via a switching device 40 which has a switch 41 which can be in at least three positions and operates like a demultiplexer. In a first position shown, the terminal L 1 is connected to the first power stage 10. Accordingly, the terminal L 1 is connected to the second power stage 20 in the second position of the switch 41 and to the third power stage 30 in the third position. In this case, the control device 2 again selects the historically least loaded power stage 10, 20, 30 in a single-phase charging process as a function of the control history and accordingly controls the switch 41 via the control signal S. The half bridge of the selected power stage is then driven by corresponding control signals S 1-S 3. In comparison with the embodiment according to FIG. 1, two half bridges 22, 32 are saved at the expense of the switching device 40. In this case, it can be provided that a switch is also arranged between the terminals L 2 or L 3 and the second power stage 20 or third power stage 30, in order to switch the terminals L 2 or L 3 to the voltage-free state when the first terminal L 1 is switched to the second power stage 20 or third power stage 30.The mode of operation of the charging device 1 will now be explained in more detail with reference to FIGS. 3a to 3e. In this case, FIG. 3 ashows the current I over the time t for the first power stage 10, FIG. 3 bshows the current I over the time t for the second power stage 20 and FIG. 3 cshows the current I over the time t for the third power stage 30. FIG. 3 dillustrates the difference of the products current x time between the first power stage 10 and the second power stage 20. Accordingly, FIG. 3 e shows the difference between the first power stage 10 and the third power stage 30. The representations according to FIGS. 3 dand 3 ein this case represent control histories. In the initial state, the load is the same for all three power stages 10, 20, 30.In the first two hours, a charging cycle then takes place by means of the first power stage 10, so that after two hours 2 h x 10 A=20 Ah were charged. Accordingly, the load increases (see FIGS. 3 dand 3 e).It can then be seen from the control history that the first power stage 10 is loaded more heavily than the second and third power stages 20, 30. a further charging cycle takes place between the third and sixth hours, wherein the control device 2 has selected the second power stage 20. Accordingly, the second power stage 20 converts 3 h x 10 A = 30 Ah. As can be seen from FIG. 3 d, the difference is continuously reduced and at the end the second power stage 20 is loaded by 10 Ah more than the first power stage 10. Therefore, the third charge cycle controller 2 selects the third power stage 30 after eight hours. 10 Ah are then reacted in one hour and the difference in FIG. 3e is reduced. After nine hours, the image then results that the third power stage 30 is loaded the least, so that it would be selected by the control device 2 for the next single-phase charging cycle.

Claims

Charging device (1), in particular for an electric or plug-in hybrid vehicle, comprising at least two power stages (10, 20, 30), by means of which an alternating voltage is converted into a direct voltage, and at least one control device (2) for controlling the power stages (10, 20, 30), wherein the control device (2) is designed in such a way that it detects the number of connected phases of an alternating voltage and controls a corresponding number of power stages (10, 20, 30) as a function of the number of detected phases, wherein the control device (2) is designed in such a way that it determines a control history of the individual power stages (10, 20, 30) and takes it into account when selecting the power stages (10, 20, 30) to be controlled in such a way that the power stages (10, 20, 30) are loaded uniformly, wherein the control device (2) controls at least one terminal (L1, L2, L3) for a phase can optionally assign different power stages (10, 20, 30), characterized in that each charging stage (10, 20, 30) has in each case a first half bridge (11, 21, 31) with power semiconductor switches, which is connected to a terminal (L1, L2, L3) for a phase, wherein the first half bridges (11, 21, 31) of the charging stages (10, 20, 30) are in each case connected to terminals (L1, L2, L3) of different phases, wherein all the power stages (20, 30) have, apart from one power stage (10), at least one further half bridge (22, 33), wherein the at least one further half bridge (22, 33) is connected to a terminal (L1) of a different phase than the first half bridge (21, 31).Charger according to claim 1, characterised in that the control history contains the number of charging processes with the respective power stage (10, 20, 30).Charger according to claim 1, characterized in that the control history contains the energy provided by the respective power stage (10, 20, 30) about the charging processes or the provided energy difference compared to at least one other power stage (10, 20, 30).Charger according to one of the preceding claims, characterized in that the charger (1) has three power stages (10, 20, 30).Charger according to one of the preceding claims, characterized in that a first power stage (10) does not have a further half bridge and the further power stages (20, 30) have exactly one further half bridge (22, 32), wherein the further half bridges (22, 32) are connected to the terminal (L1) of the phase of the first power stage (10).Method for operating a charger (1), in particular for an electric or plug-in hybrid vehicle, wherein the charger (1) comprises at least two power stages (10, 20, 30) by means of which an alternating voltage is converted into a direct voltage, and at least one control device (2) for controlling the power stages (10, 20, 30), wherein the control device (2) detects the number of connected phases of an alternating voltage and controls a corresponding number of power stages (10, 20, 30) as a function of the number of detected phases, wherein the control device (2) determines a control history of the individual power stages (10, 20, 30) and takes it into account when selecting the power stages (10, 20, 30) to be controlled in such a way that the power stages (10, 20, 30) are loaded uniformly, wherein the control device (2) controls at least one terminal (L1) for a phase of selectively different power stages (10, 20, 30), A charging stage according to claim 30), characterized in that each charging stage (10, 20, 30) has a respective first half bridge (11, 21, 31) with power semiconductor switches, which is connected to a terminal (L1, L2, L3) for one phase, wherein the first half bridges (11, 21, 31) of the charging stages (10, 20, 30) are each connected to terminals (L1, L2, L3) of different phases, wherein all the power stages (20, 30) have at least one further half bridge (22, 33) except for one power stage (10), wherein the at least one further half bridge (22, 33) is connected to a terminal (L1) of a different phase than the first half bridge (21, 31).Method according to Claim 6, characterized in that the control history contains the number of charging processes with the respective power stage (10, 20, 30).Method according to claim 6, characterised in that the control history contains the energy provided by the respective power stage (10, 20, 30) via the charging processes or the energy difference provided in comparison with at least one other power stage (10, 20, 30).

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